WO2015001918A1 - Interference measurement method and device - Google Patents

Interference measurement method and device Download PDF

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Publication number
WO2015001918A1
WO2015001918A1 PCT/JP2014/065282 JP2014065282W WO2015001918A1 WO 2015001918 A1 WO2015001918 A1 WO 2015001918A1 JP 2014065282 W JP2014065282 W JP 2014065282W WO 2015001918 A1 WO2015001918 A1 WO 2015001918A1
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Prior art keywords
interference
wave
interference measurement
distance
measurement method
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PCT/JP2014/065282
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French (fr)
Japanese (ja)
Inventor
健二 愛甲
啓 志村
成弥 田中
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株式会社日立ハイテクノロジーズ
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Publication of WO2015001918A1 publication Critical patent/WO2015001918A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
    • G01B11/0608—Height gauges

Definitions

  • the present invention relates to an interference measurement method and apparatus, and more particularly to a technique for measuring the thickness of a substance using millimeter waves and terahertz waves and the height of a specific substance in the substance.
  • One of the methods for measuring displacement using millimeter waves is an in-vehicle radar device that measures the distance by modulating millimeter waves.
  • This on-vehicle radar uses radio waves having frequencies of 60 to 61 GHz and 76 to 77 GHz (wavelengths of 4.9 to 5 mm and 3.8 to 3.9 mm), and has been put into practical use since around 1990.
  • the oscillation frequency is FM-modulated, emitted from the antenna, the signal reflected from the target is multiplied with the original signal, analog processing is performed, and the relative speed of the target and the distance to the target are calculated from the signal processing. ing.
  • the operating distance can be detected from about several meters to several hundreds of meters.
  • SS-OCT Scept-Source-Optical-Coherence-Tomography
  • Patent Document 1 As a prior art document related to an on-vehicle radar, for example, there is Patent Document 1, and as a prior art document related to SS-OCT, there is, for example, Non-Patent Document 1.
  • the above-described in-vehicle radar using millimeter waves is designed for the purpose of detecting a vehicle ahead, and thus the detection accuracy of the measurement distance is about several tens of centimeters.
  • the required accuracy when measuring the height of an object under or in a dielectric material or measuring the thickness unevenness of a dielectric film is on the order of several ⁇ m. Can not be satisfied.
  • the displacement measurement method using optical interference phenomenon has been reported in the past with examples using visible light (wavelength of about 350 nm to about 750 nm) or near infrared light (wavelength of about 1 ⁇ m).
  • this wavelength the displacement of the surface can be measured in order to use the reflected light from the surface of the material to be measured.
  • the use of near-infrared light has been actively used because of the absorptance with respect to the wavelength of a living body.
  • the absorptance of the substance is high and it is difficult to acquire internal displacement information. Therefore, the displacement of an opaque substance inside a substance that cannot be seen through by visible light, the thickness of a thin film that is opaque by visible light, and the unevenness of the thin film substrate are measured by a conventional optical displacement measuring device. I can't.
  • SS-OCT for fundus examination uses red laser light with a wavelength of 800 nm to 900 nm or an infrared laser with a wavelength of 1050 nm, and is used for examination of the retina of the fundus. ing.
  • the wavelength since the wavelength is in the vicinity of 1 ⁇ m, it absorbs relatively less moisture than infrared light and enables ophthalmic observation in a deeper region than a conventional red (near 800 nm) light source.
  • the observation of the underlying choroid is limited. This is because, in the case of light in this region, attenuation due to absorption of a dielectric material is large. For this reason, the conventional SS-OCT method is not suitable for measuring the thickness by transmitting the material, or measuring the height and size of the material in the dielectric. Alternatively, it cannot be used for measuring displacement such as defects.
  • An object of the present invention is to solve the above-described problems and provide a displacement measuring method and apparatus for measuring the thickness of a substance and the height of a specific substance in the substance with high accuracy.
  • an interference measurement method in which an object is irradiated with an irradiation wave composed of millimeter waves or terahertz waves, and the surface of the object and the reflection in the object or the object are reflected.
  • an irradiation wave composed of millimeter waves or terahertz waves
  • the surface of the object and the reflection in the object or the object are reflected.
  • the object is irradiated with an irradiation wave consisting of a millimeter wave or a terahertz wave, and from the surface of the object and the back surface of the object or a reflecting surface in the object.
  • a detection unit that detects the interference wave by causing interference between the reflected wave of the reflected wave and the reflected wave from a predetermined reference surface, and the output of the detection unit, the surface of the object and the back surface of the object or the reflecting surface in the object
  • An interference measurement device having a configuration including a calculation unit that calculates the distance between the two is provided.
  • the frequency modulation using millimeter waves and terahertz waves can be used to obtain the characteristics of interference signals at a plurality of frequencies, so that the calculation of the phase difference between the reference surface and the measurement surface can be facilitated. .
  • FIG. 3 is a diagram illustrating an example of a detailed configuration of an interferometer unit according to the first embodiment.
  • FIG. 3 is a diagram for explaining an operation principle of SS-OCT according to the first embodiment. It is a figure which shows generation
  • FIG. It is a figure which shows an example of the determination sequence based on Example 1 whether it is a convex surface or a concave surface.
  • FIG. 6 is a diagram illustrating a specific example of an SS-OCT interference signal according to Embodiment 1.
  • FIG. It is a figure which shows the measurement principle of plate
  • FIG. It is a figure which shows the principle of the interference measurement which concerns on Example 3, and a foreign material inspection under a film
  • FIG. 10 is a diagram illustrating a specific example of an SS-OCT interference signal according to Embodiment 1.
  • FIG. It is a figure which shows the measurement principle of plate
  • FIG. It is a figure which shows the principle of the interference measurement which concerns on Example 3, and a foreign material inspection under a film
  • FIG. 7 It is a figure which shows the structure which aims at the detection efficiency improvement by the reference surface of a multi-partition mirror shape based on Example 7.
  • FIG. It is a figure for demonstrating the dielectric material transmittance
  • the millimeter wave or terahertz wave used in the present invention refers to an electromagnetic wave having a wavelength of 30 ⁇ m to 10 mm.
  • the technical meaning of using these millimeter waves or terahertz waves will be outlined.
  • Millimeter waves or terahertz waves have the property of transmitting through dielectric materials. According to the present invention, it is possible to measure the thickness of the constituent material, the undulation of the surface, etc. through the material. Furthermore, the state of the lower layer of the dielectric material can be seen. In other words, measure the height and depth that cannot be measured with normal visible light by measuring the shape, unevenness, scratch-like dent, or convex shape when the lower layer is not flat, using the property of transmitting light. Is possible.
  • the Schottky barrier diode which is a millimeter wave transmission source, multiplies the input frequency and outputs it, frequency modulation can be easily realized by changing the input frequency.
  • the Gunn Diodes of the other source is a VCO (Voltage Control Oscillator), so frequency modulation is easy, and distance measurement is easy from the data value of the modulated interference wave. It is.
  • the function of the interferometer can be realized with a simple configuration.
  • Displacement measurement methods using frequency modulation using millimeter waves or terahertz waves can obtain the characteristics of interference signals at multiple frequencies, making it easy to calculate the phase difference between the reference surface and the measurement surface. Compared with a typical OCT calculation method, since the calculation method is simple, an expensive arithmetic processor is unnecessary and high-speed calculation is possible.
  • the first embodiment is a displacement measuring method for measuring a displacement amount and a height of a substance under or in a film formed of a dielectric material that transmits millimeter waves, and a displacement measurement. It is an Example regarding an apparatus.
  • a Gunn diode which is a semiconductor material
  • an oscillation source using a Schottky barrier diode and a nonlinear crystal using a wavelength tunable semiconductor laser (LD) as seed light.
  • An oscillation source by frequency conversion used, an oscillation source by a high frequency circuit using an LC circuit, or the like can be used, and it is easy to vary the oscillation frequency in any case.
  • FIG. 1 Under the control of a personal computer (PC) 100 functioning as a calculation unit and a processing unit, an interface (I / F) 101, a transmitter 102, a synthesizer 103, an SBD (Schottky with an attached waveguide and antenna) Barrier Diode) AMC (Active Multi Chain) 104, beam splitter 105, sensor SBD 106 provided with a waveguide and an antenna, lock-in amplifier 107, measurement surface 108, reference surface 109, and control signal of PC 100 is I / F101 is sent to the synthesizer 103, and a drive frequency scan (12.5 GHz to 20 GHz) is performed. The output of synthesizer 103 is sent to AMC (SBD) 104.
  • I / F101 is sent to the synthesizer 103, and a drive frequency scan (12.5 GHz to 20 GHz) is performed.
  • the output of synthesizer 103 is sent to AMC (SBD) 104.
  • the frequency of the millimeter wave oscillator 103 which is an oscillation unit.
  • the frequency is varied by inputting an instruction from the PC 100 to the synthesizer 103 via the I / F 101.
  • the output of the synthesizer 103 is supplied to the AMC (SBD) 104, and the multiplied millimeter wave is output.
  • the synthesizer 103 assuming that 100 GHz is a center frequency, the output is subjected to frequency modulation between 75 GHz and 120 GHz.
  • a synchronizing signal on the oscillator side and the receiver side is supplied from the transmitter 102 oscillating at 1 kHz.
  • On the receiving side there is a lock-in amplifier 107 for detecting weak signals, and after removing the noise strongly with a synchronized band pass filter, the intensity of the interference wave is output to the PC 100 to perform highly sensitive interference measurement. Is realized.
  • a millimeter wave with frequency modulation is used for interference measurement.
  • 100 GHz is the center frequency
  • 75 GHz to 120 GHz is frequency-modulated and used.
  • AMC products such as 20 GHz to 40 GHz, 40 GHz to 60 GHz, 50 GHz to 75 GHz, 60 GHz to 90 GHz, 90 GHz to 140 GHz, 140 GHz to 220 GHz are sold, and can be supplied to the above interferometer configuration. It is also possible.
  • the object is obtained by sensing the reflected light by forming the millimeter wave from the light source AMC 104 into a desired beam shape using a resin lens that transmits the millimeter wave, and irradiating the object.
  • the displacement, depth, and height of an object can be measured.
  • the configuration of the interferometer and the phenomenon of interference are the same in principle as the configuration of an interferometer using a normal laser. The operation principle for measuring the height and displacement with millimeter waves for realizing the present embodiment will be described below.
  • a coherent electromagnetic wave oscillation source is used in the displacement measurement due to millimeter wave interference in this embodiment.
  • the millimeter wave has a long coherence distance and is an electromagnetic wave source suitable for interference measurement.
  • the beam supplied from this wave source is supplied to the interferometer shown in FIG. In the interferometer part, it is branched into two by a wire grid polarizer or a polarization beam splitter (PBS) 105.
  • PBS polarization beam splitter
  • the direction of polarization is defined using terms in the optical field. That is, a plane parallel to a plane formed by a normal to the reflection surface and an incident wave incident angle is defined as a P-polarization (P-polarization) plane, and a plane perpendicular to the plane is an S-polarization (S-polarization).
  • the polarization plane from the AMC 104 which is an oscillation source provided with a waveguide and an antenna is P-polarized light
  • the emitted electromagnetic wave enters the beam splitter 105 through the lens.
  • the polarization plane of the reflection surface of the beam splitter 105 is installed in a direction rotated by 45 °.
  • the 45-degree component electromagnetic wave transmitted through the beam splitter 105 is reflected by a reference mirror prepared as the reference surface 108 and returns to the oscillation source side.
  • the other reflected 45 ° electromagnetic wave branched by the beam splitter 105 is reflected by the measurement surface 109 whose height is to be measured, and returns to the oscillation source side.
  • the azimuth angle is changed by 90 ° due to the passage of ⁇ / 2, and the electromagnetic wave whose polarization plane has changed from the incident time is reflected by the beam splitter 105, and a waveguide and an antenna are attached. It reaches the sensor SBD106.
  • the azimuth angle is changed by 90 ° due to the passage of ⁇ / 2, and the electromagnetic wave whose polarization plane has changed from the incident time is not reflected by the beam splitter 105 but is transmitted and reaches the sensor SBD 106.
  • the return electromagnetic waves do not interfere with each other because their 90 ° polarization plane directions are different from each other.
  • a polarization component having a direction of 45 ° is selected with respect to the measurement surface and the reference surface.
  • the antenna and waveguide attached to the sensor SBD 106 have a polarization plane selection function. Therefore, the millimeter wave reflected from the reference surface 109 and the millimeter wave reflected from the measurement surface cause interference. If it is installed in the direction of S-polarization so that the plane of polarization is aligned with the angle direction, an interference waveform from both reflected waves can be obtained.
  • the combination of the antenna and the waveguide attached to the sensor SBD 106 has polarization selectivity, it is different from the case of using visible light or infrared light and does not require an external polarizing element.
  • the displacement information of the position of the measurement surface 108 has a measurement scale based on the wavelength of the millimeter wave used for the measurement. That is, as shown in FIG. 2B, the relative displacement difference between the reference surface 109 and the measurement surface 108 is measured.
  • I (r) The intensity I (r) of the interference wave that can be measured with the interferometer is shown in the equation.
  • I (r) Is + Ir + 2 ⁇ ⁇ (Ir + Is ⁇ COS ( ⁇ s ⁇ r))
  • Is intensity of measurement light
  • Ir intensity of reference light
  • ⁇ s phase of measurement light
  • ⁇ r phase of reference light
  • the interference waveform has a period of ⁇ / 2 of the light source wavelength, when there is a phase difference exceeding the phase difference ⁇ / 2, the interference wave is a repetitive waveform so that the displacement from the reference plane is recognized. It is necessary to measure the displacement by counting the number of interference waves with the phase difference at the same time as the reference plane as the origin. Also, with this method, if the reference surface and measurement surface are displaced due to environmental changes, the reference surface must always be re-recognized, that is, an operation approximated to the origin registration operation called calibration is required. And the operation is complicated. Therefore, when a multi-pixel interferometer is realized for industrial use, it is inconvenient.
  • the measurement frequency of the above example is kept constant and the measurement is based on the physical position difference from the reference surface or reference surface, the measured value can be obtained when the reference surface position information is lost. Absent. Therefore, it is necessary to always hold the reference plane information, and if the information is missing, it is necessary to collect it again, which is inconvenient to measure.
  • This method is a method called time domain (TD) -OCT, and has drawbacks such as low speed and origin registration.
  • TD time domain
  • a countermeasure a method has been devised in which the displacement between the interference surfaces is determined by changing the frequency of the electromagnetic wave for measurement and measuring the change in frequency of the interference signal.
  • SD Spectral Domain
  • SS Send-Source
  • this SS-OCT method is adopted, and a method for calculating the distance is devised as described below.
  • FIG. 3 shows a principle configuration of SS-OCT distance calculation using the millimeter wave of this embodiment.
  • the interference wave when the interference wave is obtained by changing the frequency of the light source, the incident wave and the reflected wave are generated between the reference surface (upper surface in the drawing) 301 and the measurement surface (lower surface in the drawing) 302.
  • the interference waves strengthen each other, so that the interference waves have the maximum amplitude.
  • the peaks and valleys of the reflected wave from the upper surface and the reflected wave from the lower surface are exactly the same, the interference waves cancel each other, so that the interference wave has the minimum amplitude.
  • the distance between the upper surface and the lower surface can be calculated by measuring the intensity of the interference wave while changing the frequency.
  • Fig. 4 shows an image representing the difference in the number of gaps and interference fringes in the SS-OCT method. Comparing the case where the gap is narrow and the case where the gap is wide, as indicated by 401 in the upper part of the figure, when the gap is narrow, the frequency of the interference wave expressing light and dark is small, and the interference fringe interval is rough. It can be recognized that as the gap becomes wider as indicated by 402 in the lower stage, the number of the gaps increases and the interference fringe spacing becomes finer.
  • the interference intensity S (k) at this time is obtained by the following equation.
  • S (k) Is (k) + Ir (k) + 2 ⁇ ⁇ ⁇ Is (k) ⁇ Ir (k) ⁇ ⁇ n (an ⁇ cos (k ⁇ Zn + ⁇ (k)) Is (k),
  • a constant lightness level (DC level) of interference intensity, that is, a change component (AC level) of the interference waveform obtained by subtracting Is (k) + Ir (k) indicates the interference intensity. That is, the power spectrum density of only the interference signal has the following relationship.
  • FIG. 5 shows an example of a calculation sequence in the PC 100 that is the calculation unit of the present embodiment.
  • the gap amount is calculated by paying attention to the relationship between the gap amount and the frequency at which the interference signal is maximized.
  • the case is divided from the case where the gap is narrow.
  • the gap may be small if the interference wave does not have a maximum value. Can be assumed.
  • the gap amount is calculated using the interference wave signal values of the f1 frequency and the f2 frequency shown in (b) of the figure (503-508).
  • the maximum value of the interference wave is one (509), and the case where the maximum value is one is divided.
  • the numerical value of the wavelength of the frequency that becomes the maximum value is the gap amount (510, 511).
  • frequencies (wavelengths) of all the maximum values are listed (512), and the least common multiple is calculated (513).
  • FIG. 6 shows a sequence diagram for explaining this determination sequence.
  • the determination sequence 600 in FIG. 6A corresponds to the determination sequence (517) in FIG.
  • the actual measurement state is illustrated.
  • the illumination spot diameter is several mm even when narrowed down, and the vertical step (plate thickness) is the case.
  • the height (thickness) value has displacement data over 2 pixels or more. From this tendency, concave / convex is determined by tracing the change in the maximum frequency. That is, when the measurement surface is above the reference surface, the frequency of the maximum value of the interference wave shifts in a higher direction, but when the measurement surface is below the reference surface, the opposite characteristics are exhibited. From this tendency, it is possible to determine the convex shape or the concave shape by following the change in the maximum frequency.
  • the thickness value is obtained in the convexity determination.
  • This method does not require complicated calculations. Further, the gap amount can be calculated from the characteristics of the interference wave without providing conditions such as setting of the window function.
  • FIG. 7 shows an example in which the phase difference is measured by the interferometer system shown in FIGS. 1 and 2 of the present embodiment.
  • the frequency was varied between 78 GHz and 102 GHz, and the intensity of the interference wave was measured.
  • the maximum value for each frequency was obtained, the values shown in the table below were obtained.
  • the conditions for frequency modulation by the high-frequency signal source have been described as means for changing the oscillation frequency.
  • the wavelength of the laser light emitted from the LD can be changed by changing the injection current.
  • this technology is applied to millimeter wave oscillation, it is necessary to convert visible light or infrared light emitted by visible light LD light into millimeter waves.
  • Nonlinear crystals can be used as parts suitable for such applications. Examples of the nonlinear crystal include KTP (KTiOPO 4 ) and DAST (4-dimethylamino-N-methyl-4-stilbazolium tosylate). Matching according to the frequency of a specific millimeter wave is required from conditions such as the wavelength used, crystal orientation, and phase matching angle, and conditions are set for each crystal.
  • the reference surface (reference surface) is set to the lower surface of the object 120.
  • the reference surface 109 installed in FIG. 2 is not necessary, and the plate thickness can be calculated based on the lower surface of the object 120.
  • the measurement when the defect or foreign matter 111 is present in the inside or bottom of the layer and the foreign matter detection Examples will be described.
  • the measurement of the film thickness of the object 120 is the same as in Example 2 shown in FIG. 8, but when detecting defects due to scattered waves and foreign matter 111 in the film, the reflected light from the surface of the layer is regarded as background noise. Therefore, removal is necessary. Therefore, as shown in (b) of the figure, by adjusting the rotation angle of the ⁇ / 2 plate, the reflected wave from the upper surface of the layer is reduced, and the scattered wave signal from the in-film foreign matter 111 is efficiently generated. It becomes possible to detect with high sensitivity.
  • Example 4 an example in which the surface (upper surface) of a layer by confocal use can be measured with high resolution will be described.
  • a confocal mechanism of optical microscope technology is used.
  • a pinhole plate 112 having a pinhole having a hole diameter of about 0.1 mm is installed in front of the sensor SBD 106, and a measurement surface 108 is installed at a lens conjugate position of this pinhole.
  • a measurement point equivalent to a pinhole of ⁇ 0.1 mm can be installed on the measurement surface 108.
  • the position of the pinhole in front of the sensor SBD 106 is sequentially moved in the plane direction by XY two-dimensional driving, so that the measurement point can be moved sequentially on the measurement surface 108. Then, two-dimensional measurement information can be obtained by arranging desired measurement point information vertically and horizontally. By moving the pinhole plate 112 in the optical axis direction (Z-axis direction) and further moving it in the plane direction and repeating the measurement, the situation in the layer can be measured three-dimensionally with good resolution. That is, according to this embodiment, three-dimensional OCT can be realized by obtaining and acquiring two-dimensional surface information and measuring the height by interference.
  • data indicating the condition of the bottom of the layer can be obtained by installing a pinhole at a conjugate position with the bottom of the layer. Note that when a pinhole is installed and a conjugate relationship is made as in the present embodiment, the lateral resolution is improved, but conversely the measurement range in the vertical direction decreases, so the diameter of the pinhole depends on the requirements. It is necessary to select a shape.
  • an oscillator and a receiver are installed separately and an interference signal is detected.
  • millimeter waves and terawaves which are radio waves, unlike devices in the optical region.
  • One device for transmission and one for reception. Therefore, as a fifth embodiment, an embodiment in which a Schottky barrier diode is configured as a dual function device for transmission and reception will be described.
  • a Schottky barrier diode (SBD) 113 that oscillates radio waves is used for both transmission and reception, but can be used as both functional devices for transmission and reception by changing the bias voltage and current value. It is. For example, since 1 kHz synchronous detection is applied, it is possible to switch between transmission and reception at the detection timing.
  • the oscillation wave from the frequency modulation circuit 117 is applied to the SBD 113, and the radio wave from the SBD 113 provided with a polarizing plate function including a waveguide and an antenna passes through the lens 114, the ⁇ / 2 plate 115, and the lens 116.
  • the radio wave irradiated and reflected on the object 120 for thickness measurement is received by the SBD 113 on the reverse path, and the output is input as a received wave to the signal processing circuit 118 through the signal amplifier, for predetermined signal processing. Is given.
  • the other bias circuits are not shown.
  • the installation angle of the ⁇ / 2 plate 115 installed in the middle of the detection system It is possible to cope with it by adjusting.
  • the dimension measuring apparatus having the configuration of the present embodiment since it also serves as a transmission / reception function device, it can be realized in a small portable type. For example, application to a film thickness inspection device for a coating film on an outer wall that does not transmit light is possible.
  • FIG. 12 illustrates Example 6 using multi-pixel sensing in which receivers (sensors) are arranged on a line.
  • the illumination light for inspection irradiates an illumination wave spread in an elliptical shape in the millimeter wave irradiation region of the thickness measurement object 120 so that it can correspond to a plurality of sensors with a cylindrical lens or the like in the optical path on the way. Since the reflected interference waves are simultaneously received by the plurality of receiver arrays 119 and the outputs can be processed in parallel, the inspection can be performed over a wide area in a short time.
  • each of the divided mirrors of the multi-divided mirror 121 constituting the reference mirror is switched over time.
  • Each mirror position of the multi-partition mirror 121 having the configuration of the present embodiment can be controlled independently.
  • the reflection timing can be controlled by switching these mirrors at high speed, and the information on the measurement target surface 120 can be detected with high resolution. is there. That is, since the reflecting mirror and the object point are in a conjugate relationship and only the reflecting mirror can be detected, it is possible to sense the surface of the object point as surface information by sequentially switching the divided mirrors.
  • the information inside and below the layer can be detected with high resolution.
  • FIG. 14 shows the ratio of the millimeter wave used in the present example through the dielectric material for each frequency.
  • the horizontal axis is the millimeter wave frequency
  • the vertical axis is the relative value of transmittance. Examples of materials include polyester, denim, campus, and leather. It can be seen that the transmittance decreases as the frequency increases. Therefore, when aiming at measurement utilizing the transmission characteristics of a substance, it is a good idea to select a frequency with reference to this graph.
  • FIG. 15 is an enlarged view of the measurement unit.
  • the height measurement method (OCT) using visible light is considered as an application product example.
  • OCT optical coherence tomography
  • the reflected light from the surface is used for interference. It is possible to measure surface irregularities and flatness with high sensitivity without contact.
  • the amount of decrease in film thickness can be calculated from the displacement (AB) in the figure.
  • FIG. 16 illustrates a case where foreign matter in the film, rust and alteration have occurred under the film, and the effect of each example will be described. Also in this case, if the film cannot be permeated, it cannot be grasped that a foreign substance is present and that alteration under the film has occurred. If it is possible to measure the position under the film, as in the case of the previous film thickness measurement, when the change is measured while recognizing the position of the film upper surface and the film lower surface, there is partial variation under the film. If there is a change in the lower side of the film, or if there is a sudden change in the film thickness, it is possible to extract information such as containing foreign substances. Since at least the occurrence of an abnormality can be detected, it is possible to determine the presence of the displacement even before the measurement.
  • the millimeter wave has a length of several millimeters, the outline of the object is not clear, that is, the resolution in the lateral direction is low. For this reason, an object having a small lateral size of 1 mm or less is detected small. That is, the size of a substance (foreign matter) that is k smaller cannot be detected correctly. Although the resolution depends on conditions on the detection side, a large object can be correctly detected from an object size of approximately the wavelength. In the case of application examples such as maintenance of iron bridges and iron pillars, it is assumed that a defect of several mm size becomes a problem rather than a defect of small size. Since the thickness of the coating film is on the order of several hundreds of millimeters, it is expected that the present interferometer can detect defects occurring in the coating film and correctly measure the coating film thickness variation within a few ⁇ m. .
  • FIG. 17 shows the frequency of the millimeter wave and the degree of penetration depth, and the effect of each example will be described. From another data, there is a characteristic that the moisture absorption rate near 100 GHz is low. It can be seen that the use of millimeter waves in this region is effective for internal measurement because of less attenuation in the living body. By using millimeter waves that have a deeper penetration depth than infrared rays, it is possible to expect accurate grasp of the degree of burns.
  • OCT is utilized as an ophthalmic diagnostic apparatus using infrared rays. However, the above-described measurement method and apparatus according to the present invention enables measurement in a deeper region than the present, and performance as an ophthalmic diagnostic instrument. Improvement is expected.
  • this invention is not limited to the above-mentioned Example, Various modifications are included.
  • the above-described embodiments have been described in detail for better understanding of the present invention, and are not necessarily limited to those having all the configurations described.
  • a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment.

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Abstract

A displacement measurement method and device for measuring the thickness of a target substance relative to a dielectric material which does not transmit visible light, and the height and the depth of defects and foreign objects in the substance are provided. By using the millimeter waves and terahertz waves as irradiation waves transmitting through the dielectric material, through the interference of waves reflected from the measurement surface (108) and waves reflected from a reference surface (109), it is possible to acquire, with high precision and without attenuation, information about the thickness, depth, and height of the objects to be measured.

Description

干渉測定方法、及びその装置Interferometry method and apparatus
　本発明は干渉測定方法、及び装置に係り、特にミリ波およびテラヘルツ波を用いた物質の厚み、及び物質中にある特定の物質の高さの測定技術に関する。 The present invention relates to an interference measurement method and apparatus, and more particularly to a technique for measuring the thickness of a substance using millimeter waves and terahertz waves and the height of a specific substance in the substance.
　ミリ波を用いて変位を測定する方式の１つとして、ミリ波に変調を掛けて距離を測定する車載レーダ装置がある。この車載レーダは、周波数６０～６１ＧＨｚ、及び７６～７７ＧＨｚ（波長４．９～５ｍｍと３．８～３．９ｍｍ）の電波を使用し、１９９０年ごろから実用化されている。この方式では、発振周波数をＦＭ変調してアンテナから発射し、ターゲットから反射された信号を元の信号と掛け合わせてアナログ処理して、信号処理からターゲットの相対速度とターゲットまでの距離を算出している。動作距離は、おおよそ数ｍから百数十ｍで検出が可能となっている。 One of the methods for measuring displacement using millimeter waves is an in-vehicle radar device that measures the distance by modulating millimeter waves. This on-vehicle radar uses radio waves having frequencies of 60 to 61 GHz and 76 to 77 GHz (wavelengths of 4.9 to 5 mm and 3.8 to 3.9 mm), and has been put into practical use since around 1990. In this method, the oscillation frequency is FM-modulated, emitted from the antenna, the signal reflected from the target is multiplied with the original signal, analog processing is performed, and the relative speed of the target and the distance to the target are calculated from the signal processing. ing. The operating distance can be detected from about several meters to several hundreds of meters.
　また、半導体レーザ（laser diode :ＬＤ）やスーパルミネッセントダイオード（super luminescence diode：ＳＬＤ)の駆動電流に変調を掛けて干渉計光源とし、基準面からの反射光と、測定対象物からの反射光を干渉させて、その干渉光の強度変化から測定対象物の位置や反射面の高さを検出する方法が近年研究され、ＳＳ－ＯＣＴ（Swept Source-Optical Coherence Tomography）と称されている。 Also, it modulates the drive current of a semiconductor laser (laser diode) (LD) or super luminescence diode (SLD) to produce an interferometer light source, and reflects light from the reference surface and reflection from the measurement object. In recent years, a method for detecting the position of a measurement object and the height of a reflecting surface from a change in the intensity of the interference light by causing the light to interfere with each other has been studied and is called SS-OCT (Swept-Source-Optical-Coherence-Tomography).
　なお、車載レーダに関する先行技術文献として、例えば特許文献１、ＳＳ－ＯＣＴに関する先行技術文献として、例えば非特許文献１がある。 Note that, as a prior art document related to an on-vehicle radar, for example, there is Patent Document 1, and as a prior art document related to SS-OCT, there is, for example, Non-Patent Document 1.
特開２００３－２９４８３８号公報JP 2003-294838 A
　上述したミリ波を用いた車載レーダは、前方の車両を検出する目的で設計されているため、測定距離の検出精度はおおよそ数十センチ程度となっている。それに対し、例えば、誘電体物質下あるいは、物質中の物体の高さ測定、あるいは、誘電体膜の厚さむらを測定する場合の要求精度は数μｍオーダーのため、このような測定対象の要求を満足することはできない。 The above-described in-vehicle radar using millimeter waves is designed for the purpose of detecting a vehicle ahead, and thus the detection accuracy of the measurement distance is about several tens of centimeters. On the other hand, for example, the required accuracy when measuring the height of an object under or in a dielectric material or measuring the thickness unevenness of a dielectric film is on the order of several μm. Can not be satisfied.
　一方、光学的な干渉現象を利用した変位の測定方式では従来から、可視光（波長が約３５０ｎｍ～約７５０ｎｍ）あるいは、近赤外光（波長が約１μｍ近傍）を利用した事例がなどで報告されている。この波長を利用した場合には、測定対象部質の表面からの反射光を利用するために、表面の変位が測定できる。眼科用の変位測定装置では、生体の波長に対する吸収率から近赤外光の利用も盛んになっている。しかし、この波長領域を利用した場合には、物質での吸収率が高く、内部の変位情報を取得することが困難である。そのため、可視光により目視で透過して見えない物質の内部にある不透明物質の変位や、可視光で不透明な薄膜の膜厚、薄膜下地の凹凸などは、従来の光学方式の変位測定装置では測定ができない。 On the other hand, the displacement measurement method using optical interference phenomenon has been reported in the past with examples using visible light (wavelength of about 350 nm to about 750 nm) or near infrared light (wavelength of about 1 μm). Has been. When this wavelength is used, the displacement of the surface can be measured in order to use the reflected light from the surface of the material to be measured. In the ophthalmic displacement measuring apparatus, the use of near-infrared light has been actively used because of the absorptance with respect to the wavelength of a living body. However, when this wavelength region is used, the absorptance of the substance is high and it is difficult to acquire internal displacement information. Therefore, the displacement of an opaque substance inside a substance that cannot be seen through by visible light, the thickness of a thin film that is opaque by visible light, and the unevenness of the thin film substrate are measured by a conventional optical displacement measuring device. I can't.
　非特許文献１に見るように、眼底検査用のＳＳ－ＯＣＴでは、波長は８００ｎｍ～９００ｎｍの赤色レーザ光、あるいは、波長が１０５０ｎｍの赤外線レーザを使用し、眼底部の網膜などの検査に活用されている。この場合、波長が１μｍ近傍であるため、赤外光よりも比較的水分への吸収が少なく、従来の赤色（８００ｎｍ近傍）光源より深い領域の眼科的な観察を可能としているが、眼底網膜、さらにその下層の脈絡膜の観察にとどまっている。それは、この領域の光の場合は、誘電体製の物質の吸収による減衰が大きいためのである。このような理由により、従来のＳＳ－ＯＣＴ方式は、物質を透過して厚みを測るとか、誘電体中の物質の高さ、サイズを測定するには適しておらず、誘電体裏の物質、或いは欠陥などの変位計測には利用できない。 As seen in Non-Patent Document 1, SS-OCT for fundus examination uses red laser light with a wavelength of 800 nm to 900 nm or an infrared laser with a wavelength of 1050 nm, and is used for examination of the retina of the fundus. ing. In this case, since the wavelength is in the vicinity of 1 μm, it absorbs relatively less moisture than infrared light and enables ophthalmic observation in a deeper region than a conventional red (near 800 nm) light source. Furthermore, the observation of the underlying choroid is limited. This is because, in the case of light in this region, attenuation due to absorption of a dielectric material is large. For this reason, the conventional SS-OCT method is not suitable for measuring the thickness by transmitting the material, or measuring the height and size of the material in the dielectric. Alternatively, it cannot be used for measuring displacement such as defects.
　本発明の目的は、上述した課題を解決し、物質の厚み、及び物質中にある特定の物質の高さを高精度に測定する変位測定方法、及びその装置を提供することにある。 An object of the present invention is to solve the above-described problems and provide a displacement measuring method and apparatus for measuring the thickness of a substance and the height of a specific substance in the substance with high accuracy.
　上記の目的を達成するため、本発明においては、干渉測定方法であって、ミリ波あるいはテラヘルツ波からなる照射波を対象物に照射し、対象物の表面と、裏面もしくは対象物の中の反射面からの反射波と、所定の参照面からの反射波とを干渉させ、その干渉波を検出することにより、対象物の表面と、裏面もしくは対象物の中の反射面との間の距離を検出する干渉測定方法を提供する。 To achieve the above object, according to the present invention, there is provided an interference measurement method in which an object is irradiated with an irradiation wave composed of millimeter waves or terahertz waves, and the surface of the object and the reflection in the object or the object are reflected. By reflecting the reflected wave from the surface and the reflected wave from the predetermined reference surface and detecting the interference wave, the distance between the surface of the object and the reflecting surface in the object or the back surface is determined. An interference measurement method for detecting is provided.
　また、上記の目的を達成するため、本発明においては、ミリ波あるはテラヘルツ波からなる照射波を対象物に照射し、対象物の表面と、対象物の裏面もしくは対象物中の反射面からの反射波と、所定の参照面からの反射波とを干渉させて干渉波を検出する検出部と、検出部の出力により、対象物の表面と、対象物の裏面もしくは対象物中の反射面との間の距離を算出する算出部とを備えた構成の干渉測定装置を提供する。 In order to achieve the above object, in the present invention, the object is irradiated with an irradiation wave consisting of a millimeter wave or a terahertz wave, and from the surface of the object and the back surface of the object or a reflecting surface in the object. A detection unit that detects the interference wave by causing interference between the reflected wave of the reflected wave and the reflected wave from a predetermined reference surface, and the output of the detection unit, the surface of the object and the back surface of the object or the reflecting surface in the object An interference measurement device having a configuration including a calculation unit that calculates the distance between the two is provided.
　本発明の構成により、ミリ波あるいはテラヘルツ波を用いて変位を測ることにより、構成物質の厚み、表面のうねりなどの測定が可能となる。更に、ミリ波やテラヘルツ波を用いて周波数変調を利用し、複数の周波数における干渉信号の特性を得ることができるため、参照面と測定面間の位相差の計算の容易化を図ることができる。 With the configuration of the present invention, by measuring the displacement using millimeter waves or terahertz waves, it is possible to measure the thickness of the constituent materials, surface waviness, and the like. Furthermore, the frequency modulation using millimeter waves and terahertz waves can be used to obtain the characteristics of interference signals at a plurality of frequencies, so that the calculation of the phase difference between the reference surface and the measurement surface can be facilitated. .
実施例１に係る、変位測定装置の全体構成の一例を示す図である。It is a figure which shows an example of the whole structure of the displacement measuring device based on Example 1. FIG. 実施例１に係る、干渉計部の詳細構成の一例を示す図である。FIG. 3 is a diagram illustrating an example of a detailed configuration of an interferometer unit according to the first embodiment. 実施例１に係る、ＳＳ－ＯＣＴの動作原理を説明するための図である。FIG. 3 is a diagram for explaining an operation principle of SS-OCT according to the first embodiment. 実施例１に係る、ギャップが狭い場合と広い場合の干渉縞の発生比較を示す図である。It is a figure which shows generation | occurrence | production comparison of the interference fringe in the case where a gap is narrow based on Example 1, and when it is wide. 実施例１に係る、干渉縞から変位（ギャップ）を求めるシーケンスの一例を示す図である。It is a figure which shows an example of the sequence which calculates | requires a displacement (gap) from an interference fringe based on Example 1. FIG. 実施例１に係る、凸面か、凹面かの判定シーケンスの一例を示す図である。It is a figure which shows an example of the determination sequence based on Example 1 whether it is a convex surface or a concave surface. 実施例１に係る、ＳＳ－ＯＣＴの干渉信号の一具体例を示す図である。6 is a diagram illustrating a specific example of an SS-OCT interference signal according to Embodiment 1. FIG. 実施例２に係る、板厚の測定原理を示す図である。It is a figure which shows the measurement principle of plate | board thickness based on Example 2. FIG. 実施例３に係る、干渉計測と膜下の異物検査の原理を示す図である。It is a figure which shows the principle of the interference measurement which concerns on Example 3, and a foreign material inspection under a film | membrane. 実施例４に係る、共焦点方式による高解像度多点測定の一例を示す図である。It is a figure which shows an example of the high-resolution multipoint measurement by a confocal method based on Example 4. FIG. 実施例５に係る、発振器と受信器の一デバイス化した干渉計部の一例を示す図である。FIG. 10 is a diagram illustrating an example of an interferometer unit that is formed as one device of an oscillator and a receiver according to a fifth embodiment. 実施例６に係る、並列センシングによる検出効率向上を図る構成を示す図である。It is a figure which shows the structure which aims at the detection efficiency improvement by parallel sensing based on Example 6. FIG. 実施例７に係る、多分割ミラー形状の参照面による検出効率向上を図る構成を示す図である。It is a figure which shows the structure which aims at the detection efficiency improvement by the reference surface of a multi-partition mirror shape based on Example 7. FIG. 各実施例に係る、テラヘルツ波の誘電体物質透過率を説明するための図である。It is a figure for demonstrating the dielectric material transmittance | permeability of a terahertz wave based on each Example. 各実施例に係る、膜厚の変動を説明するための図である。It is a figure for demonstrating the fluctuation | variation of the film thickness based on each Example. 各実施例に係る、膜中欠陥の検出を説明するための図である。It is a figure for demonstrating the detection of the defect in a film | membrane based on each Example. 各実施例に係る、生体皮膚組織の異常検出・計測を説明するための図である。It is a figure for demonstrating the abnormality detection and measurement of a biological skin tissue based on each Example.
　以下、本発明を実施するための種々の形態を、図面に従い説明する。本発明で用いるミリ波あるいはテラヘルツ波とは、その波長が３０μｍから１０ｍｍの波長の電磁波をいう。まず、本発明の各種の実施例を説明する前に、これらのミリ波あるいはテラヘルツ波を用いることの技術的な意味を概説する。 Hereinafter, various modes for carrying out the present invention will be described with reference to the drawings. The millimeter wave or terahertz wave used in the present invention refers to an electromagnetic wave having a wavelength of 30 μm to 10 mm. First, before describing various embodiments of the present invention, the technical meaning of using these millimeter waves or terahertz waves will be outlined.
　（１）ミリ波あるいはテラヘルツ波は誘電体物質を透過する性質がある。本発明によれば、物質を透過して、構成物質の厚み、表面のうねりなどの測定が可能である。さらに、誘電体物質の下層の状態が判る。つまり、下層が平面でない場合の形状、凹凸、あるいは、キズのような凹み、凸形状などを通常の可視光では、計測できない高さ、深さを、透過する性質を利用して、計測することが可能である。 (1) Millimeter waves or terahertz waves have the property of transmitting through dielectric materials. According to the present invention, it is possible to measure the thickness of the constituent material, the undulation of the surface, etc. through the material. Furthermore, the state of the lower layer of the dielectric material can be seen. In other words, measure the height and depth that cannot be measured with normal visible light by measuring the shape, unevenness, scratch-like dent, or convex shape when the lower layer is not flat, using the property of transmitting light. Is possible.
　（２）ミリ波の発信源であるショットキ－バリアダイオード（ＳＢＤ）は入力周波数を逓倍して出力するので、入力周波数を変えることによって、容易に周波数変調が実現できる。また、もう一方の発信源のガンダイオード(Gunn Diodes)では、ＶＣＯ（Voltage Control Oscillator）になっているので、周波数変調が容易であり、変調を掛けた干渉波のデータ値から距離の測定が容易である。 (2) Since the Schottky barrier diode (SBD), which is a millimeter wave transmission source, multiplies the input frequency and outputs it, frequency modulation can be easily realized by changing the input frequency. In addition, the Gunn Diodes of the other source is a VCO (Voltage Control Oscillator), so frequency modulation is easy, and distance measurement is easy from the data value of the modulated interference wave. It is.
　（３）さらに、可変したときの各周波数でのコヒーレンシが良いために、可干渉距離が長く、各周波数での干渉信号がS/N良く得られる。 (3) Furthermore, since coherency at each frequency when variable is good, the coherence distance is long, and an interference signal at each frequency can be obtained with good S / N.
　（４）ダイオードから導波路＋アンテナにより、空間に放出するために、直線偏波の方向選択性が高く、干渉効果を効率的に形成できる。また、電波の発振と受信は１つのデバイスで兼用することができるので、簡単な構成で干渉計の機能の実現が可能である。 (4) Since the light is emitted from the diode into the space by the waveguide + antenna, the direction selectivity of the linearly polarized wave is high, and the interference effect can be formed efficiently. In addition, since the oscillation and reception of radio waves can be shared by a single device, the function of the interferometer can be realized with a simple configuration.
　ミリ波やテラヘルツ波を用いて周波数変調を利用した変位測定方式では、複数の周波数における干渉信号の特性を得ることができるため、参照面と測定面間の位相差の計算が容易にでき、一般的なＯＣＴ計算方式と比較して、計算方式は簡易であるために、高額な演算処理機が不要であり、かつ、高速な演算が可能となる。 Displacement measurement methods using frequency modulation using millimeter waves or terahertz waves can obtain the characteristics of interference signals at multiple frequencies, making it easy to calculate the phase difference between the reference surface and the measurement surface. Compared with a typical OCT calculation method, since the calculation method is simple, an expensive arithmetic processor is unnecessary and high-speed calculation is possible.
　第一の実施例は、対象物として、特にミリ波を透過する誘電体物質で形成された膜の下あるいは、膜中にある物質の変位量、高さを測定する変位測定方法、および変位測定装置に関する実施例である。 The first embodiment is a displacement measuring method for measuring a displacement amount and a height of a substance under or in a film formed of a dielectric material that transmits millimeter waves, and a displacement measurement. It is an Example regarding an apparatus.
　まず、本実施例において、ミリ波の発振源としては、半導体物質であるガンダイオード、ショットキーバリアダイオードを用いた発振源、その他には、波長可変半導体レーザ（ＬＤ）を種光として非線形結晶を用いた周波数変換による発振源、ＬＣ回路を用いた高周波回路による発振源などが利用でき、いずれであってもその発振周波数を可変することは容易である。ミリ波、テラヘルツ波を使用することによって、可視光では透過しないために測定ができない不可視物体の膜厚、あるいは物体の下、および、中に形成されている反射物体（反射面）の変位、高さ、深さの測定を可能とする変位測定方法、および変位測定装置を実現できる。 First, in this embodiment, as a millimeter wave oscillation source, a Gunn diode, which is a semiconductor material, an oscillation source using a Schottky barrier diode, and a nonlinear crystal using a wavelength tunable semiconductor laser (LD) as seed light. An oscillation source by frequency conversion used, an oscillation source by a high frequency circuit using an LC circuit, or the like can be used, and it is easy to vary the oscillation frequency in any case. By using millimeter waves and terahertz waves, the film thickness of an invisible object that cannot be measured because it is not transmitted by visible light, or the displacement of the reflecting object (reflecting surface) formed under and in the object, high In addition, a displacement measuring method and a displacement measuring device capable of measuring the depth can be realized.
　まず、図１を用いて、ミリ波の発振器と受信器として、ショットキーバリアダイオードを用いた本実施例の干渉計システムの一構成例を説明する。図１において、算出部、処理部として機能するパーソナルコンピュータ（ＰＣ）１００の制御の下、インタフェース（Ｉ／Ｆ）１０１、発信器１０２、シンセサイザ１０３、導波管とアンテナが付設されたＳＢＤ（Schottky Barrier Diode）のＡＭＣ（Active Multi Chain）１０４、ビームスプリッタ１０５、導波管とアンテナが付設されたセンサＳＢＤ１０６、ロックインアンプ１０７、測定面１０８、参照面１０９から構成され、ＰＣ１００の制御信号がＩ／Ｆ１０１を介してシンセサイザ１０３に送られ、駆動周波数スキャン（１２．５ＧＨｚ～２０ＧＨｚ）がなされる。シンセサイザ１０３の出力はＡＭＣ（ＳＢＤ）１０４に送られる。 First, a configuration example of the interferometer system of this embodiment using a Schottky barrier diode as a millimeter wave oscillator and receiver will be described with reference to FIG. In FIG. 1, under the control of a personal computer (PC) 100 functioning as a calculation unit and a processing unit, an interface (I / F) 101, a transmitter 102, a synthesizer 103, an SBD (Schottky with an attached waveguide and antenna) Barrier Diode) AMC (Active Multi Chain) 104, beam splitter 105, sensor SBD 106 provided with a waveguide and an antenna, lock-in amplifier 107, measurement surface 108, reference surface 109, and control signal of PC 100 is I / F101 is sent to the synthesizer 103, and a drive frequency scan (12.5 GHz to 20 GHz) is performed. The output of synthesizer 103 is sent to AMC (SBD) 104.
　本装置構成では、干渉波の位相差から変位を算出するために、発振部であるミリ波の発振器１０３の周波数を変えて測定する。発振部側では、ＰＣ１００からの指示を、Ｉ／Ｆ１０１経由で、シンセサイザ１０３に入力することにより、周波数を可変する。シンセサイザ１０３の出力をＡＭＣ（ＳＢＤ）１０４に供給して、逓倍したミリ波を出力している。シンセサイザ１０３では、１００ＧＨｚを中心周波数とすると、その出力は７５ＧＨｚ～１２０ＧＨｚ間で周波数の変調を掛けている。また、別途、１ｋＨｚで発振している発信器１０２から発振器側と受信器側の同期信号を供給している。受信側には、微弱信号検出用にロックインアンプ１０７があり、同期を掛けたバンドパスフィルターで、強力にノイズを除去した後、干渉波の強度をＰＣ１００に出力して、高感度な干渉計測を実現している。 In this apparatus configuration, in order to calculate the displacement from the phase difference of the interference wave, measurement is performed by changing the frequency of the millimeter wave oscillator 103 which is an oscillation unit. On the oscillation unit side, the frequency is varied by inputting an instruction from the PC 100 to the synthesizer 103 via the I / F 101. The output of the synthesizer 103 is supplied to the AMC (SBD) 104, and the multiplied millimeter wave is output. In the synthesizer 103, assuming that 100 GHz is a center frequency, the output is subjected to frequency modulation between 75 GHz and 120 GHz. Separately, a synchronizing signal on the oscillator side and the receiver side is supplied from the transmitter 102 oscillating at 1 kHz. On the receiving side, there is a lock-in amplifier 107 for detecting weak signals, and after removing the noise strongly with a synchronized band pass filter, the intensity of the interference wave is output to the PC 100 to perform highly sensitive interference measurement. Is realized.
　次に、図２を用いて、干渉計の機能として実現する光学系の構成を説明する。周波数変調が掛ったミリ波を干渉測定用に使用する。例えば、１００ＧＨｚを中心周波数とすると、７５ＧＨｚ～１２０ＧＨｚまでを周波数変調して利用している。その他の周波数については、２０ＧＨｚ～４０ＧＨｚ、４０ＧＨｚ～６０ＧＨｚ、５０ＧＨｚ～７５ＧＨｚ、６０ＧＨｚ～９０ＧＨｚ、９０ＧＨｚ～１４０ＧＨｚ、１４０ＧＨｚ～２２０ＧＨｚなどのＡＭＣ製品が販売されており、上記の干渉計の構成に供給することが同じく可能である。 Next, the configuration of the optical system realized as the function of the interferometer will be described with reference to FIG. A millimeter wave with frequency modulation is used for interference measurement. For example, assuming that 100 GHz is the center frequency, 75 GHz to 120 GHz is frequency-modulated and used. For other frequencies, AMC products such as 20 GHz to 40 GHz, 40 GHz to 60 GHz, 50 GHz to 75 GHz, 60 GHz to 90 GHz, 90 GHz to 140 GHz, 140 GHz to 220 GHz are sold, and can be supplied to the above interferometer configuration. It is also possible.
　この光源であるＡＭＣ１０４からのミリ波を、ミリ波を透過する樹脂材質のレンズを用いて、所望のビーム形状に成型して、対象物に照射して、その反射光をセンシングすることによって、対象物の変位、深さ、高さを計測可能とする。干渉計の構成と、干渉する現象は、通常のレーザを利用した干渉計と原理構成は同等である。本実施例を実現するミリ波での高さ、変位測定についての動作原理を以下に説明をする。 The object is obtained by sensing the reflected light by forming the millimeter wave from the light source AMC 104 into a desired beam shape using a resin lens that transmits the millimeter wave, and irradiating the object. The displacement, depth, and height of an object can be measured. The configuration of the interferometer and the phenomenon of interference are the same in principle as the configuration of an interferometer using a normal laser. The operation principle for measuring the height and displacement with millimeter waves for realizing the present embodiment will be described below.
　まず、本実施例のミリ波による干渉による変位計測では、コヒーレントな可干渉性のある電磁波の発振源を使用する。ミリ波は、可干渉距離が長く、干渉計測に適した電磁波源である。この波動源から供給したビームは、図２の（ａ）に示す干渉計に供給される。干渉計部分では、ワイヤーグリッド偏光子、あるいは、偏光ビームスプリッタ（ＰＢＳ）１０５にて２分岐される。ここで、偏波の方向を光学分野での用語を用いて定義する。すなわち、反射面の垂線と入射波入射角度で作る平面と平行な面をＰ偏波（Ｐ偏光）面、垂直な面をＳ偏波（Ｓ偏光）とする。干渉系を形成する場合には、２方向に分割する必要がある。導波管とアンテナが付設された発振源であるＡＭＣ１０４からの偏波面をＰ偏波とする時、出射された電磁波はレンズを介してビームスプリッタ１０５に入射する。このビームスプリッタ１０５の反射面の偏波面は、それから４５°回転した方向に設置する。ビームスプリッタ１０５を透過した透過４５°成分の電磁波は、参照面１０８として用意した参照ミラーで反射して、発振源側に戻る。また、ビームスプリッタ１０５で分岐されたもう一方の反射４５°成分の電磁波は、高さの測定対象としている測定面１０９で反射されて、発振源側に戻る。 First, a coherent electromagnetic wave oscillation source is used in the displacement measurement due to millimeter wave interference in this embodiment. The millimeter wave has a long coherence distance and is an electromagnetic wave source suitable for interference measurement. The beam supplied from this wave source is supplied to the interferometer shown in FIG. In the interferometer part, it is branched into two by a wire grid polarizer or a polarization beam splitter (PBS) 105. Here, the direction of polarization is defined using terms in the optical field. That is, a plane parallel to a plane formed by a normal to the reflection surface and an incident wave incident angle is defined as a P-polarization (P-polarization) plane, and a plane perpendicular to the plane is an S-polarization (S-polarization). When forming an interference system, it is necessary to divide into two directions. When the polarization plane from the AMC 104 which is an oscillation source provided with a waveguide and an antenna is P-polarized light, the emitted electromagnetic wave enters the beam splitter 105 through the lens. The polarization plane of the reflection surface of the beam splitter 105 is installed in a direction rotated by 45 °. The 45-degree component electromagnetic wave transmitted through the beam splitter 105 is reflected by a reference mirror prepared as the reference surface 108 and returns to the oscillation source side. The other reflected 45 ° electromagnetic wave branched by the beam splitter 105 is reflected by the measurement surface 109 whose height is to be measured, and returns to the oscillation source side.
　参照面１０８からの戻り電磁波の内、λ／２通過により方位角が９０°代わり、偏波面が入射時とは変化した電磁波が、ビームスプリッタ１０５で反射して、導波管とアンテナが付設されたセンサＳＢＤ１０６へ届く。測定面１０９側の場合には、λ／２通過により方位角が９０°代わり、偏波面が入射時とは変化した電磁波が、ビームスプリッタ１０５で反射されず、透過してセンサＳＢＤ１０６に届く。この戻り電磁波は、お互いに９０°偏波面方向が異なるので、そのままでは干渉しない。干渉させるためには、測定面と参照面に対して、４５°の方向の偏光成分を選択する。ミリ波の場合には、センサＳＢＤ１０６に付設されたアンテナと導波路に偏波面の選択機能があるので、参照面１０９から反射したミリ波と測定面から反射したミリ波は干渉を起こすため、４５°方向に偏波面を合わせる様に、Ｓ偏波の方向に設置すると、両反射波からの干渉波形を得ることができる。このように、センサＳＢＤ１０６に付設したアンテナと導波路の組合せに偏光選択性があるので、可視光や赤外光を使用する場合と異なっていて外付けの偏光素子を必要としない。 Of the return electromagnetic wave from the reference surface 108, the azimuth angle is changed by 90 ° due to the passage of λ / 2, and the electromagnetic wave whose polarization plane has changed from the incident time is reflected by the beam splitter 105, and a waveguide and an antenna are attached. It reaches the sensor SBD106. In the case of the measurement surface 109 side, the azimuth angle is changed by 90 ° due to the passage of λ / 2, and the electromagnetic wave whose polarization plane has changed from the incident time is not reflected by the beam splitter 105 but is transmitted and reaches the sensor SBD 106. The return electromagnetic waves do not interfere with each other because their 90 ° polarization plane directions are different from each other. In order to cause interference, a polarization component having a direction of 45 ° is selected with respect to the measurement surface and the reference surface. In the case of a millimeter wave, the antenna and waveguide attached to the sensor SBD 106 have a polarization plane selection function. Therefore, the millimeter wave reflected from the reference surface 109 and the millimeter wave reflected from the measurement surface cause interference. If it is installed in the direction of S-polarization so that the plane of polarization is aligned with the angle direction, an interference waveform from both reflected waves can be obtained. Thus, since the combination of the antenna and the waveguide attached to the sensor SBD 106 has polarization selectivity, it is different from the case of using visible light or infrared light and does not require an external polarizing element.
　参照面１０８を固定した場合には、測定面１０８の位置の変位情報は、測定に使用するミリ波の波長が測定のスケールになる。つまり、図２の（ｂ）に示すように、参照面１０９と測定面１０８の相対変位差を測定することになる。 When the reference surface 108 is fixed, the displacement information of the position of the measurement surface 108 has a measurement scale based on the wavelength of the millimeter wave used for the measurement. That is, as shown in FIG. 2B, the relative displacement difference between the reference surface 109 and the measurement surface 108 is measured.
　干渉計で測定できる干渉波の強度I(r)を式に示す。
　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　
　　　　　I(r)=Is+Ir+2×√（Ir+Is×COS（θs－θr）)
　　　　　ここで、Is：測定光の強度、Ir：参照光の強度
　　　　　Θs：測定光の位相、θr：参考光の位相
　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　
　なお、この基本構成の干渉計による変位の測定には、課題が２つある。その課題を説明する。
  まず、干渉強度の情報のみを考慮した場合、測定可能範囲に課題がある。この干渉方式では、干渉波形の位相差を変位計測に用いるために、参照面を基準として、変位を測定する必要がある。しかし、干渉波形は光源波長のλ/２を周期としているので、位相差λ/２を超える位相差が有る場合には、干渉波が繰り返し波形のために基準面との変位を認識するためには、基準面と同一時の位相差を原点として、干渉波の波数をカウントして、変位を計測することが必要である。また、この方式では、環境の変動により、参照面と測定面との変位が生じる場合には、常に参照面の認識をし直すこと、つまり、キャリブレーションと呼ばれる原点登録操作に近似した操作が必要になり、動作が煩雑である。そのため、工業用に多画素の干渉計を実現する場合には使い勝手が悪い。 The intensity I (r) of the interference wave that can be measured with the interferometer is shown in the equation.

I (r) = Is + Ir + 2 × √ (Ir + Is × COS (θs−θr))
Where Is: intensity of measurement light, Ir: intensity of reference light Θs: phase of measurement light, θr: phase of reference light
It should be noted that there are two problems in measuring displacement with this basic configuration interferometer. The problem will be described.
First, when only information on interference intensity is considered, there is a problem in the measurable range. In this interference method, in order to use the phase difference of the interference waveform for displacement measurement, it is necessary to measure the displacement with reference to the reference surface. However, since the interference waveform has a period of λ / 2 of the light source wavelength, when there is a phase difference exceeding the phase difference λ / 2, the interference wave is a repetitive waveform so that the displacement from the reference plane is recognized. It is necessary to measure the displacement by counting the number of interference waves with the phase difference at the same time as the reference plane as the origin. Also, with this method, if the reference surface and measurement surface are displaced due to environmental changes, the reference surface must always be re-recognized, that is, an operation approximated to the origin registration operation called calibration is required. And the operation is complicated. Therefore, when a multi-pixel interferometer is realized for industrial use, it is inconvenient.
　次に、干渉距離を測る際、上記の事例の測定周波数を一定にして置いて、参照面あるいは基準面との物理的な位置差から測る場合では、参照面位置情報が無くなると測定値が出せない。そこで、常に参照面情報を保持しておく必要があり、情報が欠落したら再度採取が必要であり、測定が不便である。この方式は、タイムドメイン（ＴＤ）－ＯＣＴと呼ばれている方式であり、低速、且つ原点登録が必要なことなどの欠点があった。その対策として、測定用の電磁波の周波数を変えて、干渉信号の周波数別の変化を測定することによって、干渉面間の変位を求める方式が考案された。 Next, when measuring the interference distance, if the measurement frequency of the above example is kept constant and the measurement is based on the physical position difference from the reference surface or reference surface, the measured value can be obtained when the reference surface position information is lost. Absent. Therefore, it is necessary to always hold the reference plane information, and if the information is missing, it is necessary to collect it again, which is inconvenient to measure. This method is a method called time domain (TD) -OCT, and has drawbacks such as low speed and origin registration. As a countermeasure, a method has been devised in which the displacement between the interference surfaces is determined by changing the frequency of the electromagnetic wave for measurement and measuring the change in frequency of the interference signal.
　この方式の一つに、測定センサ側に分光器を用いて、干渉信号の分光スペクトル別の信号強度から、測定面の面位置の算出を行う、スペクトラルドメイン（ＳＤ）－ＯＣＴがある。しかし、この方法では、測定に時間が掛ることや、分光器のロスがあるために、波長の算出精度に限界があることが報告されている。そこで、この不具合の対策をするために、干渉計に照射する電磁波の周波数を変えて、その周波数毎に干渉信号強度を得る方式が、光学の分野で近年開発されている。Ｓｗｅｐｔ－Ｓｏｕｒｃｅ（ＳＳ）－ＯＣＴと呼ばれ、現在、眼底診断装置で使用されている。 One of these methods is Spectral Domain (SD) -OCT, which uses a spectroscope on the measurement sensor side to calculate the surface position of the measurement surface from the signal intensity of each interference spectrum. However, this method has been reported to have a limit in wavelength calculation accuracy due to the time required for measurement and the loss of the spectroscope. Therefore, in order to deal with this problem, a method for changing the frequency of the electromagnetic wave applied to the interferometer and obtaining the interference signal intensity for each frequency has been recently developed in the field of optics. It is called “Swept-Source (SS) -OCT” and is currently used in a fundus diagnosis apparatus.
　本実施例のミリ波を利用する変位測定装置の構成では、このＳＳ－ＯＣＴの方式を採用し、更に距離の算出方法に次に説明する考案をした。 In the configuration of the displacement measuring apparatus using the millimeter wave according to the present embodiment, this SS-OCT method is adopted, and a method for calculating the distance is devised as described below.
　図３に、本実施例のミリ波を利用するＳＳ－ＯＣＴの距離算出の原理構成を示す。同図において、光源の周波数を変えて、干渉波を得る場合、基準面（図中では、上面）３０１と測定面（図中では、下面）３０２の間で、入射波と反射波の波形が同じ形状の場合には、上面と下面からの反射波が重なった時に、干渉波は強め合うことから、干渉波は最大振幅になる。一方、上面からの反射波と下面からの反射波の、山と谷がちょうど一致している場合には、干渉波は互いに打ち消し合うことから、干渉波は最少振幅になる。そして、周波数を変えながら、この干渉波の強度を測定することによって、上面と下面との距離を算出することができる。 FIG. 3 shows a principle configuration of SS-OCT distance calculation using the millimeter wave of this embodiment. In the figure, when the interference wave is obtained by changing the frequency of the light source, the incident wave and the reflected wave are generated between the reference surface (upper surface in the drawing) 301 and the measurement surface (lower surface in the drawing) 302. In the case of the same shape, when the reflected waves from the upper surface and the lower surface overlap, the interference waves strengthen each other, so that the interference waves have the maximum amplitude. On the other hand, when the peaks and valleys of the reflected wave from the upper surface and the reflected wave from the lower surface are exactly the same, the interference waves cancel each other, so that the interference wave has the minimum amplitude. The distance between the upper surface and the lower surface can be calculated by measuring the intensity of the interference wave while changing the frequency.
　図４に、ＳＳ－ＯＣＴ方式でのギャップと干渉縞の本数の違いを画像で表現した図を示す。ギャップが狭い場合と広い場合を比較すると、同図上段の４０１に示すように、ギャップが狭い場合には、明暗を表現する干渉波の周波数は数が少なく、干渉縞間隔が粗いが、同図下段の４０２に示すようにギャップが広くなると、その数が増加し、干渉縞間隔が細かくなる様子が認識できる。 Fig. 4 shows an image representing the difference in the number of gaps and interference fringes in the SS-OCT method. Comparing the case where the gap is narrow and the case where the gap is wide, as indicated by 401 in the upper part of the figure, when the gap is narrow, the frequency of the interference wave expressing light and dark is small, and the interference fringe interval is rough. It can be recognized that as the gap becomes wider as indicated by 402 in the lower stage, the number of the gaps increases and the interference fringe spacing becomes finer.
　以下に、本実施例のミリ波を用いた変位測定装置の構成において、周波数変調波を光源とした場合の、算出部における高さ、厚さ方向の測定の寸法算出方法について説明をする。
  まず、通常のコヒーレントな光源を使用した時のＳＳ－ＯＣＴの計算方式について、説明する。変調波の波長λとするとき、波数は２π/λとなる。 In the following, a description will be given of a method for calculating dimensions in the height and thickness direction measurement in the calculation unit when the frequency modulation wave is used as the light source in the configuration of the displacement measuring apparatus using millimeter waves of the present embodiment.
First, an SS-OCT calculation method when a normal coherent light source is used will be described. When the wavelength of the modulated wave is λ, the wave number is 2π / λ.
　この時の干渉の強度S(ｋ)は、次式で求められる。
　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　
　　S(ｋ)=Is(ｋ)+Ir(k)+2×√{Is(k)×Ir(k)×Σn(an×cos(k×Zn＋φ(k))
　　　　　　　 　　　　　Is(k)、Ir(k)：信号波と参照波のスペクトル分布
　　　　　　　　　 　　　ｋは測定光源の波数、
　　　　　　　　　　 　　Anは深さZnでの反射率、φ(k)は信号波と参照波の位相差
　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　
　干渉強度の一定明度レベル（ＤＣレベル）、つまりIs(k)+Ir(k)を引いた、干渉波形の変化成分（ＡＣレベル）は、干渉強度を示す。つまり、干渉信号のみのパワースペクトル密度は下記の関係になる。 The interference intensity S (k) at this time is obtained by the following equation.

S (k) = Is (k) + Ir (k) + 2 × √ {Is (k) × Ir (k) × Σn (an × cos (k × Zn + φ (k))
Is (k), Ir (k): Spectral distribution of signal wave and reference wave k is the wave number of the measurement light source,
An is the reflectivity at depth Zn, φ (k) is the phase difference between the signal wave and the reference wave
A constant lightness level (DC level) of interference intensity, that is, a change component (AC level) of the interference waveform obtained by subtracting Is (k) + Ir (k) indicates the interference intensity. That is, the power spectrum density of only the interference signal has the following relationship.
　Sinterf(k)=2×√Is(k)×Ir(k)×cos（kZn+φ(k)）
　Wiener-Khinchinの定理によると、このパワースペクトル密度は自己相関関数のフーリエ変換に等しい。よって、スペクトル干渉信号をフーリエ逆変換することによって、干渉の変位を計算することができて、つまり、試料面での変位（干渉距離）を算出することができる。波長１μｍ近傍のＬＤやＳＬＤを用いた光学のＳＳ－ＯＣＴでは、変位（干渉距離）を算出するためにこの計算をしている。しかし、この計算方法では、計算が複雑で、フーリエ変換の境界条件の条件設定に依っては、算出誤差を発生させる可能性がある。そこで、本実施例の構成においては、この通常のフーリエ変換に代わる、新たに考案した変位の計算方式を用いる。 Sinterf (k) = 2 × √Is (k) × Ir (k) × cos (kZn + φ (k))
According to Wiener-Khinchin's theorem, this power spectral density is equal to the Fourier transform of the autocorrelation function. Therefore, by performing Fourier inverse transform on the spectrum interference signal, the displacement of interference can be calculated, that is, the displacement (interference distance) on the sample surface can be calculated. In optical SS-OCT using an LD or SLD near a wavelength of 1 μm, this calculation is performed to calculate the displacement (interference distance). However, in this calculation method, the calculation is complicated, and there is a possibility of generating a calculation error depending on the setting of the boundary condition of the Fourier transform. Therefore, in the configuration of the present embodiment, a newly devised displacement calculation method is used instead of the normal Fourier transform.
　図５に、本実施例の算出部であるＰＣ１００での計算シーケンスの一例を示した。本実施例の方式では、ギャップ量と、干渉信号の極大になる周波数との関係に着目してギャップ量の計算を行う。まず、図５の計算シーケンス５００においては、ギャップが狭い場合から場合分けをする。 FIG. 5 shows an example of a calculation sequence in the PC 100 that is the calculation unit of the present embodiment. In the system of this embodiment, the gap amount is calculated by paying attention to the relationship between the gap amount and the frequency at which the interference signal is maximized. First, in the calculation sequence 500 of FIG. 5, the case is divided from the case where the gap is narrow.
　同図の（ｂ）に示す周波数を下限値から上限値へスキャンして干渉波の強度特性データを取得した時（５０１）、干渉波が極大値を持たない場合には、ギャップが小さいことが想定できる。この場合には、同図の（ｂ）に示すf1周波数とf2周波数の干渉波信号値を用いて、ギャップ量の算出を行う（５０３－５０８）。 When the interference wave intensity characteristic data is acquired by scanning the frequency shown in FIG. 5B from the lower limit value to the upper limit value (501), the gap may be small if the interference wave does not have a maximum value. Can be assumed. In this case, the gap amount is calculated using the interference wave signal values of the f1 frequency and the f2 frequency shown in (b) of the figure (503-508).
　次に、干渉波の極大値が一つか否かを判定し（５０９）、極大値が１つの場合を分ける。この場合には、極大値になる周波数の波長その数値がギャップ量である（５１０、５１１）。次に、干渉波の極大値が２つ以上有る場合、全ての極大値の周波数（波長）をリストアップし（５１２）、その最小公倍数を算出する（５１３）。次に、基準面に対して、凸面（プラス値）か凹面かの判定が必要か判断し（５１４）、不要の場合、最小公倍数がギャップとなる（５１４、５１５、５１６）。さらに、基準面に対して、凸面（プラス値）、凹面になっているかの判定が必要とした場合、判定シーケンス（５１７）を行う。 Next, it is determined whether or not the maximum value of the interference wave is one (509), and the case where the maximum value is one is divided. In this case, the numerical value of the wavelength of the frequency that becomes the maximum value is the gap amount (510, 511). Next, when there are two or more maximum values of the interference wave, frequencies (wavelengths) of all the maximum values are listed (512), and the least common multiple is calculated (513). Next, it is determined whether it is necessary to determine whether the surface is convex (plus value) or concave with respect to the reference surface (514). If not, the least common multiple becomes a gap (514, 515, 516). Further, when it is necessary to determine whether the reference surface is a convex surface (plus value) or a concave surface, a determination sequence (517) is performed.
　図６にこの判定シーケンスを説明するシーケンス図を示した。同図の（a）の判定シーケンス６００が、図５の判定シーケンス（５１７）に対応する。 FIG. 6 shows a sequence diagram for explaining this determination sequence. The determination sequence 600 in FIG. 6A corresponds to the determination sequence (517) in FIG.
　まず、図６の（ｂ）において、実際の測定の状態を図示すると、順次測定する中では、照明スポット径は絞り込んだ場合にも、数mmの径になり、垂直段差（板厚）の場合にも、高さ（厚み）数値は２画素以上に渡って、変位データを持つことになす。この傾向から、極大値周波数の変化をトレースすることによって、凹、凸の判定を行う。すなわち、測定面が参照面より上側に有る時、干渉波の極大値の周波数は、高い方向にシフトするが、測定面が参照面より下側に有る時は、逆の特性を示す。この傾向より、極大値の周波数の変化をたどることによって、凸形状か、凹形状化の判定が行える。板厚の測定の場合には、
（測定側とは反対面）裏面を基準（参照面）とする時、凸判定の中で板厚の数値を得ることになる。この方式では、複雑な計算をすることなく。また、窓関数の設定などの条件を設けなくても、干渉波の特徴からギャップ量の算出が可能である。 First, in FIG. 6B, the actual measurement state is illustrated. During sequential measurement, the illumination spot diameter is several mm even when narrowed down, and the vertical step (plate thickness) is the case. In addition, the height (thickness) value has displacement data over 2 pixels or more. From this tendency, concave / convex is determined by tracing the change in the maximum frequency. That is, when the measurement surface is above the reference surface, the frequency of the maximum value of the interference wave shifts in a higher direction, but when the measurement surface is below the reference surface, the opposite characteristics are exhibited. From this tendency, it is possible to determine the convex shape or the concave shape by following the change in the maximum frequency. In the case of plate thickness measurement,
(Surface opposite to the measurement side) When the back surface is used as a standard (reference surface), the thickness value is obtained in the convexity determination. This method does not require complicated calculations. Further, the gap amount can be calculated from the characteristics of the interference wave without providing conditions such as setting of the window function.
　図７に、本実施例の図１と図２に示した干渉計システムで、位相差を測定した事例を示す。この測定事例では、周波数は78GHｚから102GHｚ間を可変して、干渉波の強度を測定した。周波数毎の極大値を求めると、下表の数値になった。

表
Figure JPOXMLDOC01-appb-I000001
FIG. 7 shows an example in which the phase difference is measured by the interferometer system shown in FIGS. 1 and 2 of the present embodiment. In this measurement example, the frequency was varied between 78 GHz and 102 GHz, and the intensity of the interference wave was measured. When the maximum value for each frequency was obtained, the values shown in the table below were obtained.

table
Figure JPOXMLDOC01-appb-I000001
　極大値の周波数から、波長を算出し、その最小公倍数で位相差を求めると63.4mmとなる。この時、干渉計システムの参照面と測定面の距離は、63.4/2＝31.7mmであった。この事から、極大値計算方式による、位相差の算出とそれを用いた変位量の算出は可能であること明らかである。また、位相差が少ない場合には、極大値を持たないことになる。その場合には、任意の周波数を２つ選定して、その周波数での干渉強度値から位相差を計算して、変位量の算出が可能であるが、ここでは、計算は省略する。なお、上記の計算例では、干渉波の極大値に着目して位相差を計算している。しかし、計算には、極小値を用いることも同じく可能であり、同様の手法を用いて、同等の結果を得ることができる。 Calculating the wavelength from the maximum frequency and finding the phase difference with the least common multiple gives 63.4 mm. At this time, the distance between the reference surface and the measurement surface of the interferometer system was 63.4 / 2 = 31.7 mm. From this, it is clear that the phase difference can be calculated and the displacement amount can be calculated using the maximum value calculation method. Further, when the phase difference is small, there is no maximum value. In that case, it is possible to select two arbitrary frequencies and calculate the phase difference from the interference intensity value at that frequency to calculate the amount of displacement, but here the calculation is omitted. In the above calculation example, the phase difference is calculated by paying attention to the maximum value of the interference wave. However, it is also possible to use the minimum value for the calculation, and an equivalent result can be obtained using the same method.
　なお、図１に示した本実施例の干渉計システムにおいては、発振周波数を変化させる手段として、高周波信号源にて周波数変調をさせる条件についての説明をした。しかし、変調させる手段は他にもある。たとえば、注入電流の変化によって、ＬＤから発せられるレーザ光の波長の変動させることができる。この技術をミリ波の発振に応用する場合には、可視光ＬＤ光で発光する可視光あるいは、赤外光をミリ波に変換することが必要である。
このような用途に適した部品として、非線形結晶を用いることが可能である。この非線形結晶の種類としては、ＫＴＰ(KTiOPO4)、ＤＡＳＴ(4-dimethylamino-N-methyl-4-stilbazolium tosylate)などがある。使用波長と結晶方位、位相整合角度などの条件から特定のミリ波の周波数に応じた整合が必要であり、各結晶毎に条件を設定して使用する。 In the interferometer system of the present embodiment shown in FIG. 1, the conditions for frequency modulation by the high-frequency signal source have been described as means for changing the oscillation frequency. However, there are other means for modulating. For example, the wavelength of the laser light emitted from the LD can be changed by changing the injection current. When this technology is applied to millimeter wave oscillation, it is necessary to convert visible light or infrared light emitted by visible light LD light into millimeter waves.
Nonlinear crystals can be used as parts suitable for such applications. Examples of the nonlinear crystal include KTP (KTiOPO 4 ) and DAST (4-dimethylamino-N-methyl-4-stilbazolium tosylate). Matching according to the frequency of a specific millimeter wave is required from conditions such as the wavelength used, crystal orientation, and phase matching angle, and conditions are set for each crystal.
　図８を用いて、第２の実施例として、干渉計の形態の他の実施例についての説明を行う。同図の対象物１２０の板厚、即ち上面と下面間の厚みを測る本実施例においては、参照面(基準面)は対象物１２０の下面に設定することにする。この場合には、図２に設置した参照面１０９は必要がなく、対象物１２０の下面基準での板厚の算出が可能である。 Referring to FIG. 8, another example of an interferometer will be described as a second example. In the present embodiment in which the plate thickness of the object 120 in FIG. 5, that is, the thickness between the upper surface and the lower surface is measured, the reference surface (reference surface) is set to the lower surface of the object 120. In this case, the reference surface 109 installed in FIG. 2 is not necessary, and the plate thickness can be calculated based on the lower surface of the object 120.
　次に図９を用いて、第３の実施例として、対象物１２０の層厚の測定の他に、層の内部や底面に欠陥や膜中異物１１１が有った場合の測定と異物検出の実施例について説明をする。対象物１２０の膜厚の測定は図８に示した実施例２と同じであるが、散乱波による欠陥や膜中異物１１１の検出をする場合には、層表面からの反射光は背景ノイズとなることから除去が必要である。そこで、同図の（ｂ）に示すように、λ／２板の回転角度を調整することによって、層上面からの反射波を低減して、膜中異物１１１からの散乱波信号を効率的に感度良く、検出することが可能になる。 Next, with reference to FIG. 9, as a third embodiment, in addition to the measurement of the layer thickness of the object 120, the measurement when the defect or foreign matter 111 is present in the inside or bottom of the layer and the foreign matter detection Examples will be described. The measurement of the film thickness of the object 120 is the same as in Example 2 shown in FIG. 8, but when detecting defects due to scattered waves and foreign matter 111 in the film, the reflected light from the surface of the layer is regarded as background noise. Therefore, removal is necessary. Therefore, as shown in (b) of the figure, by adjusting the rotation angle of the λ / 2 plate, the reflected wave from the upper surface of the layer is reduced, and the scattered wave signal from the in-film foreign matter 111 is efficiently generated. It becomes possible to detect with high sensitivity.
　次に、実施例４として、共焦点利用による層の表面（上面）を解像度良く測定可能な実施例を説明する。本実施例においては、光学の顕微鏡技術の共焦点の仕組みを利用する。図１０に示すように、センサＳＢＤ１０６の前に穴径φ０．１ｍｍほどのピンホールを有するピンホールプレート１１２を設置して、このピンホールのレンズ共役の位置に測定面１０８を設置する。この場合、測定面１０８にφ０．１ｍｍのピンホール同等の測定点を設置ができる。そして、センサＳＢＤ１０６前のピンホールを、Ｘ－Ｙ２次元駆動により平面方向に順次位置送りをすることによって、測定面１０８上で、順次測定点の移動をすることができる。そして、縦と横に所望の測定点情報を並べることにより、２次元の測定情報を得ることができる。ピンホールプレート１１２を光軸方向（Ｚ軸方向）に移動させて、さらに、平面方向に移動させて測定を繰り返すことによって、層中の状況を解像度良く、三次元の測定が可能である。すなわち、本実施例によれば、２次元面情報出取得と、干渉による高さ測定で、３次元のＯＣＴが実現可能となる。 Next, as Example 4, an example in which the surface (upper surface) of a layer by confocal use can be measured with high resolution will be described. In this embodiment, a confocal mechanism of optical microscope technology is used. As shown in FIG. 10, a pinhole plate 112 having a pinhole having a hole diameter of about 0.1 mm is installed in front of the sensor SBD 106, and a measurement surface 108 is installed at a lens conjugate position of this pinhole. In this case, a measurement point equivalent to a pinhole of φ0.1 mm can be installed on the measurement surface 108. The position of the pinhole in front of the sensor SBD 106 is sequentially moved in the plane direction by XY two-dimensional driving, so that the measurement point can be moved sequentially on the measurement surface 108. Then, two-dimensional measurement information can be obtained by arranging desired measurement point information vertically and horizontally. By moving the pinhole plate 112 in the optical axis direction (Z-axis direction) and further moving it in the plane direction and repeating the measurement, the situation in the layer can be measured three-dimensionally with good resolution. That is, according to this embodiment, three-dimensional OCT can be realized by obtaining and acquiring two-dimensional surface information and measuring the height by interference.
　さらに、層の底面と共役位置にピンホールを設置することにより、層底面の状況を示すデータを得ることもできる。なお、本実施例のようにピンホールを設置して共役関係を作ると、横分解能は向上するが、逆に縦方向の測定レンジが減少する関係になるので、要求条件によって、ピンホールの径や形を選択する必要がある。 Furthermore, data indicating the condition of the bottom of the layer can be obtained by installing a pinhole at a conjugate position with the bottom of the layer. Note that when a pinhole is installed and a conjugate relationship is made as in the present embodiment, the lateral resolution is improved, but conversely the measurement range in the vertical direction decreases, so the diameter of the pinhole depends on the requirements. It is necessary to select a shape.
　以上説明した各実施例においては、発振器と受信器を別々に設置して、干渉信号を検出していたが、電波であるミリ波、テラ波の場合には、光の領域のデバイスと異なって、送信と受信のデバイスを１つにすることができる。そこで、実施例５として、ショットキーバリアダイオードを、送受信の両機能デバイスとして構成する実施例を説明する。 In each of the embodiments described above, an oscillator and a receiver are installed separately and an interference signal is detected. However, in the case of millimeter waves and terawaves, which are radio waves, unlike devices in the optical region. , One device for transmission and one for reception. Therefore, as a fifth embodiment, an embodiment in which a Schottky barrier diode is configured as a dual function device for transmission and reception will be described.
　図１１に示すように、電波を発振するショットキーバリアダイオード（ＳＢＤ）１１３は、送信と受信で各使用されるが、バイアス電圧、電流値を変えることで、送受信の両機能デバイスとして使用が可能である。例えば１ｋＨｚの同期検波を掛けているので、その検波タイミングで送信と受信の切り替えを行うことも可能である。同図において、周波数変調回路１１７からの発振波はＳＢＤ１１３に印加され、導波管とアンテナからなる偏光板機能が付設されたＳＢＤ１１３からの電波は、レンズ１１４、λ／２板１１５、レンズ１１６を介して、厚み測定対象物１２０に照射され、反射された電波は、逆の経路のＳＢＤ１１３で受信され、その出力が受信波として、信号増幅器を通り信号処理回路１１８に入力され、所定の信号処理が施される。なお、その他のバイアス回路等は図示を省略した。 As shown in FIG. 11, a Schottky barrier diode (SBD) 113 that oscillates radio waves is used for both transmission and reception, but can be used as both functional devices for transmission and reception by changing the bias voltage and current value. It is. For example, since 1 kHz synchronous detection is applied, it is possible to switch between transmission and reception at the detection timing. In the figure, the oscillation wave from the frequency modulation circuit 117 is applied to the SBD 113, and the radio wave from the SBD 113 provided with a polarizing plate function including a waveguide and an antenna passes through the lens 114, the λ / 2 plate 115, and the lens 116. Then, the radio wave irradiated and reflected on the object 120 for thickness measurement is received by the SBD 113 on the reverse path, and the output is input as a received wave to the signal processing circuit 118 through the signal amplifier, for predetermined signal processing. Is given. The other bias circuits are not shown.
　本実施例においても、対象の厚み測定物１２０からの下面（参照面）と上面（測定面）から反射波の信号強度の調整には、検出系途中に設置したλ/２板１１５の設置角度を調整することで対応が可能である。本実施例の構成の寸法測定装置によれば、送受機能デバイスを兼用するため、小型可搬型で実現が可能である。たとえば、光の透過しない外壁の塗装膜の膜厚検査器などへの応用が実現可能である。 Also in this embodiment, in order to adjust the signal intensity of the reflected wave from the lower surface (reference surface) and the upper surface (measurement surface) from the target thickness measurement object 120, the installation angle of the λ / 2 plate 115 installed in the middle of the detection system It is possible to cope with it by adjusting. According to the dimension measuring apparatus having the configuration of the present embodiment, since it also serves as a transmission / reception function device, it can be realized in a small portable type. For example, application to a film thickness inspection device for a coating film on an outer wall that does not transmit light is possible.
　なお、更に、実施例５の変形例として、検出の面積を広くし、効率化を図る装置構成として、第６の実施例がある。 Furthermore, as a modified example of the fifth embodiment, there is a sixth embodiment as a device configuration for increasing the detection area and improving the efficiency.
　図１２に、受信器（センサ）をライン上にならべた多画素センシングを使う実施例６を図示した。同図において、検査用の照明光は途中の光路の中で、シリンドリカルレンズなどで複数センサに対応できるように、厚み測定対象物１２０のミリ波照射領域で楕円形状に広げた照明波を照射して、その反射した干渉波を複数の受信器アレイ１１９で同時に受信し、その出力を並列処理して検査ができるために、短時間に広面積の検査をすることができる。 FIG. 12 illustrates Example 6 using multi-pixel sensing in which receivers (sensors) are arranged on a line. In the same figure, the illumination light for inspection irradiates an illumination wave spread in an elliptical shape in the millimeter wave irradiation region of the thickness measurement object 120 so that it can correspond to a plurality of sensors with a cylindrical lens or the like in the optical path on the way. Since the reflected interference waves are simultaneously received by the plurality of receiver arrays 119 and the outputs can be processed in parallel, the inspection can be performed over a wide area in a short time.
　さらに、広面積検査の他の変形実施例の一つとして、参照面にＸ－Ｙ多分割ミラーを設置する実施例を説明する。本実施例は、図１３に示すように、参照ミラーを構成する多分割ミラー１２１の各分割ミラーを時間で切り替えを行う構成の実施例である。本実施例の構成の多分割ミラー１２１の各ミラー位置は独立に制御可能であり、これらを高速で切り替えて反射タイミングの制御を行い、測定対象面１２０の情報を解像度良く検出することが可能である。すなわち、反射ミラーと物点が共役関係になっており、反射ミラーのみが検出できるので、順次に分割ミラーを切り替えて、物点上を面情報としてセンシングすることが可能となる。更に、本実施例においても、実施例４で説明したピンホールの事例の如く、光軸方向に移動することによって、層の内部や下部の情報も、解像度良く検出が可能である。 Furthermore, as another modified example of the large area inspection, an example in which an XY multi-partition mirror is installed on the reference surface will be described. In the present embodiment, as shown in FIG. 13, each of the divided mirrors of the multi-divided mirror 121 constituting the reference mirror is switched over time. Each mirror position of the multi-partition mirror 121 having the configuration of the present embodiment can be controlled independently. The reflection timing can be controlled by switching these mirrors at high speed, and the information on the measurement target surface 120 can be detected with high resolution. is there. That is, since the reflecting mirror and the object point are in a conjugate relationship and only the reflecting mirror can be detected, it is possible to sense the surface of the object point as surface information by sequentially switching the divided mirrors. Furthermore, in this embodiment, as in the case of the pinhole described in the fourth embodiment, by moving in the direction of the optical axis, the information inside and below the layer can be detected with high resolution.
　続いて、以上説明した各実施例を応用した測定例について説明する。図１４は、本実施例で用いたミリ波が、誘電体物質を透過する割合を周波数別に表している。横軸は、ミリ波の周波数、縦軸は、透過率の相対値である。材質の種類は、ポリエステル、デニム地、キャンパス地、皮革の事例を記載している。周波数は高くなるに従って、透過率が低下している様子が理解できる。そこで、物質の透過特性を活用した測定を狙う場合には、このグラフを参照して周波数を選定することが得策である。 Subsequently, measurement examples applying the above-described embodiments will be described. FIG. 14 shows the ratio of the millimeter wave used in the present example through the dielectric material for each frequency. The horizontal axis is the millimeter wave frequency, and the vertical axis is the relative value of transmittance. Examples of materials include polyester, denim, campus, and leather. It can be seen that the transmittance decreases as the frequency increases. Therefore, when aiming at measurement utilizing the transmission characteristics of a substance, it is a good idea to select a frequency with reference to this graph.
　次に、図１５を用いて、着色した塗装などの厚みの変動、平面度の測定に使用するときの効果を説明する。図１５は、その測定部の拡大図である。可視光を利用した高さの測定方式（ＯＣＴ）等が応用製品例として考えられ、可視光の通らない着色塗装、または、着色膜の場合には、表面からの反射光を干渉などを用いて、非接触で高感度に表面の凹凸、平面度などの測定が可能である。図中の（Ａ－Ｂ）の変位から膜厚の減少量が計算できる。しかし、下地の部在の剥がれなどが発生した場合、つまり、下地が凹凸形状になっている場合には、表面を測定しただけでは、その凹凸が膜厚の変動にあるのか、または、下地膜の凹凸の影響を受けているのかが判らない。 Next, with reference to FIG. 15, the effect when used for measuring thickness variation and flatness of a colored coating or the like will be described. FIG. 15 is an enlarged view of the measurement unit. The height measurement method (OCT) using visible light is considered as an application product example. In the case of a colored coating or colored film that does not allow visible light to pass, the reflected light from the surface is used for interference. It is possible to measure surface irregularities and flatness with high sensitivity without contact. The amount of decrease in film thickness can be calculated from the displacement (AB) in the figure. However, when peeling of a part of the base occurs, that is, when the base has a concavo-convex shape, whether the concavo-convex is a fluctuation in the film thickness by simply measuring the surface, or the base film I do not know whether it is affected by the unevenness.
　そこで、この膜の膜厚を正確に測定をするためには、膜を透過することが必要になる。ミリ波では、膜透過率が高いために、膜の上面の位置と下面の位置を測定することによって、膜厚を正確に測定することが可能となる。図中の（Ｂ－Ｃ）で正確な膜厚が解る。さらに、表面凸形状の場合には、裏面の情報から、剥がれが発生しているか、膜厚が厚いのかなどの情報を得ることができる。 Therefore, in order to accurately measure the film thickness of this film, it is necessary to permeate the film. Since millimeter wave has a high membrane transmittance, it is possible to accurately measure the film thickness by measuring the position of the upper surface and the lower surface of the film. The exact film thickness can be found at (BC) in the figure. Further, in the case of the convex shape on the front surface, information such as whether peeling has occurred or the film thickness is thick can be obtained from the information on the back surface.
　次に、図１６に、膜中の異物、膜下に錆、変質の発生している場合の事例を図示し、各実施例の効果を説明をする。この場合も、膜を透過することができなければ、異物存在していること、膜下での変質が発生していることは把握ができない。先の膜厚測定の事例のように、膜下の位置の測定が可能であれば、膜上面と膜下面の位置を認識しつつ、その変化を計測している時に、膜下の部分変動があれば、膜の下側の変質で有ったり、膜厚の急激な変動が有る場合には、異物を含有しているなどの情報をとりだすことが出来る。少なくとも、異常の発生を検出することができるために、その変位を計測前段階であっても、その存在を判断することが可能となる。 Next, FIG. 16 illustrates a case where foreign matter in the film, rust and alteration have occurred under the film, and the effect of each example will be described. Also in this case, if the film cannot be permeated, it cannot be grasped that a foreign substance is present and that alteration under the film has occurred. If it is possible to measure the position under the film, as in the case of the previous film thickness measurement, when the change is measured while recognizing the position of the film upper surface and the film lower surface, there is partial variation under the film. If there is a change in the lower side of the film, or if there is a sudden change in the film thickness, it is possible to extract information such as containing foreign substances. Since at least the occurrence of an abnormality can be detected, it is possible to determine the presence of the displacement even before the measurement.
　ミリ波は、波長が数ｍｍの長さを持つために、対象物の輪郭が明確ではない、つまり、横方向に対する分解能が低いことになる。そのために、１ｍｍ以下の横サイズの小さい物については、小さく検出されることになる。すなわち、ｋ小さい物質（異物）の寸法は正しく検出できない。分解能は、検出側の条件にも左右されるが、大よそ波長程度の物体サイズから大きいものが正しく検出できることになる。鉄橋や鉄柱などのメンテナンスなどの応用例の場合には、小さいサイズの欠陥よりも、数ｍｍサイズの欠陥が課題になることが想定される。塗装膜の膜厚は数百ｍｍオーダで形成されていることから、本干渉計によって塗装膜中に発生する欠陥の検出と塗装膜の膜厚変動が数μｍで正しく計測できることの効果は期待できる。 Since the millimeter wave has a length of several millimeters, the outline of the object is not clear, that is, the resolution in the lateral direction is low. For this reason, an object having a small lateral size of 1 mm or less is detected small. That is, the size of a substance (foreign matter) that is k smaller cannot be detected correctly. Although the resolution depends on conditions on the detection side, a large object can be correctly detected from an object size of approximately the wavelength. In the case of application examples such as maintenance of iron bridges and iron pillars, it is assumed that a defect of several mm size becomes a problem rather than a defect of small size. Since the thickness of the coating film is on the order of several hundreds of millimeters, it is expected that the present interferometer can detect defects occurring in the coating film and correctly measure the coating film thickness variation within a few μm. .
　次に生体の内部の状態の計測に使用した場合の説明を行う。ミリ波の波長は数ｍｍであることから、生体についても波長が長くなると浸透深さも深くなることが計測されている。赤外線の浸透深さは、数100μｍに対して、ミリ波の浸透深さは数ｍｍ程度との情報がある。しかし、一方、水分による吸収も発生するために、吸収率の少ない波長域を選択することが感度向上に必要となる。 Next, an explanation will be given of the case where it is used to measure the internal state of a living body. Since the wavelength of the millimeter wave is several mm, it has been measured that the penetration depth of a living body also increases as the wavelength increases. There is information that the penetration depth of infrared rays is several hundred μm, while the penetration depth of millimeter waves is about several millimeters. However, on the other hand, since absorption due to moisture also occurs, it is necessary to select a wavelength region with a low absorption rate in order to improve sensitivity.
　図１７に、ミリ波の周波数と浸透深さの程度を示し、各実施例の効果を説明する。別のデータからは１００ＧＨｚ近傍での水分の吸収率が低い特性がある。この領域のミリ波を活用することは生体内での減衰が少ないので内部の測定には有効であることが判る。赤外線より浸透深さの深いミリ波を使用することに依って、やけどの程度の正確な状態把握などに期待ができる。現在、赤外線を用いた眼科用の診断装置としてＯＣＴが活用されているが、上述した本発明に係る測定方法、装置では現在よりもさらに深い領域での測定が可能となり、眼科診断器としての性能向上が見込まれる。 FIG. 17 shows the frequency of the millimeter wave and the degree of penetration depth, and the effect of each example will be described. From another data, there is a characteristic that the moisture absorption rate near 100 GHz is low. It can be seen that the use of millimeter waves in this region is effective for internal measurement because of less attenuation in the living body. By using millimeter waves that have a deeper penetration depth than infrared rays, it is possible to expect accurate grasp of the degree of burns. Currently, OCT is utilized as an ophthalmic diagnostic apparatus using infrared rays. However, the above-described measurement method and apparatus according to the present invention enables measurement in a deeper region than the present, and performance as an ophthalmic diagnostic instrument. Improvement is expected.
　なお、本発明は上記した実施例に限定されるものではなく、様々な変形例が含まれる。例えば、上記した実施例は本発明のより良い理解のために詳細に説明したのであり、必ずしも説明の全ての構成を備えるものに限定されものではない。また、ある実施例の構成の一部を他の実施例の構成に置き換えることが可能であり、また、ある実施例の構成に他の実施例の構成を加えることが可能である。また、各実施例の構成の一部について、他の構成の追加・削除・置換をすることが可能である。 In addition, this invention is not limited to the above-mentioned Example, Various modifications are included. For example, the above-described embodiments have been described in detail for better understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.
１００　パーソナルコンピュータ（ＰＣ）
１０１　インタフェース（Ｉ／Ｆ）
１０２　発振器
１０３　シンセサイザ
１０４　ＡＭＣ（ＳＢＤ）
１０５　ビームスプリッタ
１０６　センサＳＢＤ
１０７　ロックインアンプ
１０８　測定面
１０９　参照面
１１０、１１４、１１６　レンズ
１１１　膜中異物
１１２　ピンホールプレート
１１３　ＳＢＤ
１１５　λ／２板
１１７　周波数変調回路
１１８　信号処理回路
１１９　受信器アレー
１２０　測定対象物
１２１　多分割ミラー 100 Personal computer (PC)
101 Interface (I / F)
102 Oscillator 103 Synthesizer 104 AMC (SBD)
105 Beam splitter 106 Sensor SBD
107 Lock-in amplifier 108 Measurement surface 109 Reference surface 110, 114, 116 Lens 111 Foreign matter in film 112 Pinhole plate 113 SBD
115 λ / 2 plate 117 frequency modulation circuit 118 signal processing circuit 119 receiver array 120 measurement object 121 multi-partition mirror

Claims (18)

  1. ミリ波あるいはテラヘルツ波からなる照射波を対象物に照射し、前記対象物の表面と、前記対象物の裏面もしくは対象物中の反射面からの反射波と、所定の参照面からの反射波とを干渉させて干渉波を干渉信号として検出する検出部と、
    前記検出部の出力により、前記対象物の表面と、前記対象物の裏面もしくは対象物中の前記反射面との間の距離を算出する算出部と、を備える、
    ことを特徴とする干渉測定装置。     Irradiating the object with an irradiation wave consisting of millimeter waves or terahertz waves, and a reflected wave from the surface of the object, a back surface of the object or a reflecting surface in the object, and a reflected wave from a predetermined reference surface Detecting the interference wave as an interference signal,
    A calculation unit that calculates a distance between the surface of the object and the back surface of the object or the reflection surface in the object by an output of the detection unit;
    An interference measuring apparatus characterized by that.
  2. 請求項１に記載の干渉測定装置であって、
    前記検出部は前記照射波の周波数を可変にして、前記周波数と干渉強度値から前記距離を算出する、
    ことを特徴とする干渉測定装置。     The interference measurement apparatus according to claim 1,
    The detection unit makes the frequency of the irradiation wave variable, and calculates the distance from the frequency and the interference intensity value.
    An interference measuring apparatus characterized by that.
  3. 請求項１に記載の干渉測定装置であって、
    前記算出部は、前記干渉信号から距離を算出する時に、可変幅内の周波数と干渉強度の極大値、もしくは、極小値から、前記参照面と前記対象物との距離を算出する、
    ことを特徴とする干渉測定装置。     The interference measurement apparatus according to claim 1,
    The calculation unit calculates the distance between the reference surface and the object from the maximum value of the frequency and interference intensity within the variable width or the minimum value when calculating the distance from the interference signal.
    An interference measuring apparatus characterized by that.
  4. 請求項１に記載の干渉測定装置であって、
    前記検出部は、前記ミリ波あるいはテラヘルツ波となる電磁波の発生に、入力周波数を逓倍化して出力できるアクティブマルチチェイン型ショットキーバリアダイオードを用いる、
    ことを特徴とする干渉測定装置。     The interference measurement apparatus according to claim 1,
    The detection unit uses an active multi-chain Schottky barrier diode that can output by multiplying an input frequency to generate an electromagnetic wave that becomes the millimeter wave or the terahertz wave,
    An interference measuring apparatus characterized by that.
  5. 請求項１に記載の干渉測定装置であって、
    前記検出部は、前記ミリ波あるいはテラヘルツ波となる電磁波の発生に、ＶＣＯ（Voltage Control Oscillator）を発振源としているガンダイオードを用いる、
    ことを特徴とする干渉測定装置。     The interference measurement apparatus according to claim 1,
    The detection unit uses a Gunn diode having a VCO (Voltage Control Oscillator) as an oscillation source to generate the electromagnetic wave that becomes the millimeter wave or the terahertz wave.
    An interference measuring apparatus characterized by that.
  6. 請求項１に記載の干渉測定装置であって、
    前記検出部は、前記対象物の距離を測る場合に、前記参照面として、前記対象物の前記測定面とは異なる面を用い、当該二面間の距離を測定する、
    ことを特徴とする干渉測定装置。     The interference measurement apparatus according to claim 1,
    The detection unit, when measuring the distance of the object, uses a surface different from the measurement surface of the object as the reference surface, and measures the distance between the two surfaces.
    An interference measuring apparatus characterized by that.
  7. 請求項１に記載の干渉測定装置であって、
    前検出部は、前記対象物の距離を測る場合に、検出光路中にピンホールを設置して、ピンホールの共役位置の干渉距離を測る、
    ことを特徴とする渉測定装置。     The interference measurement apparatus according to claim 1,
    The pre-detection unit, when measuring the distance of the object, installs a pinhole in the detection optical path, and measures the interference distance of the conjugate position of the pinhole,
    This is a measuring device.
  8. 請求項１に記載の干渉測定装置であって、
    前記検出部に、ライン状検出器アレイを用いる、
    ことを特徴とする干渉測定装置。     The interference measurement apparatus according to claim 1,
    A line-shaped detector array is used for the detection unit.
    An interference measuring apparatus characterized by that.
  9. 請求項１に記載の干渉測定装置であって、
    前記ミリ波あるいはテラヘルツ波となる電磁波を発振する発振部と前記検出部を１つのデバイス中に形成する、
    ことを特徴とする干渉測定装置。     The interference measurement apparatus according to claim 1,
    Forming the oscillation part for oscillating the electromagnetic wave to be the millimeter wave or the terahertz wave and the detection part in one device;
    An interference measuring apparatus characterized by that.
  10. 請求項１に記載の干渉測定装置であって、
    前記ミリ波およびテラヘルツ波の波長は、３０μｍ～１０ｍｍである、
    ことを特徴とする干渉測定装置。     The interference measurement apparatus according to claim 1,
    The wavelengths of the millimeter wave and the terahertz wave are 30 μm to 10 mm.
    An interference measuring apparatus characterized by that.
  11. 干渉測定方法であって、
    ミリ波あるいはテラヘルツ波からなる照射波を対象物に照射し、対象物の表面と、裏面もしくは対象物の中の反射面からの反射波と、所定の参照面からの反射波とを干渉させ、その干渉波を干渉信号として検出することにより、前記対象物の表面と、裏面もしくは対象物の中の前記反射面との間の距離を検出する、
    ことを特徴とする干渉測定方法。     An interference measurement method comprising:
    Irradiate the object with an irradiation wave consisting of millimeter waves or terahertz waves, and interfere the reflected wave from the surface of the object, the back surface or the reflecting surface in the object, and the reflected wave from the predetermined reference surface, By detecting the interference wave as an interference signal, the distance between the surface of the object and the back surface or the reflecting surface in the object is detected.
    An interference measurement method characterized by the above.
  12. 請求項１１に記載の干渉測定方法であって、
    前記照射波の周波数を可変にして、前記周波数と干渉強度値から距離を算出する、
    ことを特徴とする干渉測定方法。     The interference measurement method according to claim 11, comprising:
    The frequency of the irradiation wave is made variable, and the distance is calculated from the frequency and the interference intensity value.
    An interference measurement method characterized by the above.
  13. 請求項１１に記載の干渉測定方法であって、
    前記干渉信号から距離を算出する時に、可変幅内の周波数と干渉強度の極大値、もしくは、極小値から、前記距離を算出する、
    ことを特徴とする干渉測定方法。     The interference measurement method according to claim 11, comprising:
    When calculating the distance from the interference signal, calculate the distance from the maximum value or the minimum value of the frequency and interference intensity within the variable width,
    An interference measurement method characterized by the above.
  14. 請求項１１に記載の干渉測定方法であって、
    前記ミリ波あるいはテラヘルツ波となる電磁波の発生に、入力周波数を逓倍化して出力できるアクティブマルチチェイン型ショットキーバリアダイオードを用いる、
    ことを特徴とする干渉測定方法。     The interference measurement method according to claim 11, comprising:
    Using an active multi-chain Schottky barrier diode that can output by multiplying the input frequency for generation of the electromagnetic wave that becomes the millimeter wave or terahertz wave,
    An interference measurement method characterized by the above.
  15. 請求項１１に記載の干渉測定方法であって、
    前記ミリ波あるいはテラヘルツ波となる電磁波の発生に、ＶＣＯ（Voltage Control Oscillator）を発振源としているガンダイオードを用いる、
    ことを特徴とする干渉測定方法。     The interference measurement method according to claim 11, comprising:
    A Gunn diode using a VCO (Voltage Control Oscillator) as an oscillation source is used to generate electromagnetic waves that become millimeter waves or terahertz waves.
    An interference measurement method characterized by the above.
  16. 請求項１１に記載の干渉測定方法であって、
    前記対象物の距離を測る場合に、前記参照面として、前記対象物の前記測定面とは異なる面を用い、当該二面間の距離を測定する、
    ことを特徴とする干渉測定方法。     The interference measurement method according to claim 11, comprising:
    When measuring the distance of the object, using a surface different from the measurement surface of the object as the reference surface, and measuring the distance between the two surfaces,
    An interference measurement method characterized by the above.
  17. 請求項１１に記載の干渉測定方法であって、
    前記対象物の距離を測る場合に、検出光路中にピンホールを設置して、ピンホールの共役位置の干渉距離を測る、
    ことを特徴とする干渉測定方法。     The interference measurement method according to claim 11, comprising:
    When measuring the distance of the object, install a pinhole in the detection optical path, and measure the interference distance of the conjugate position of the pinhole,
    An interference measurement method characterized by the above.
  18. 請求項１１に記載の干渉測定方法であって、
    前記ミリ波、あるいはテラヘルツ波の波長は、３０μｍ～１０ｍｍである、
    ことを特徴とする干渉測定方法。     The interference measurement method according to claim 11, comprising:
    The wavelength of the millimeter wave or terahertz wave is 30 μm to 10 mm.
    An interference measurement method characterized by the above.
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