CN116678310A - Light-splitting interferometer and imaging light path thereof - Google Patents
Light-splitting interferometer and imaging light path thereof Download PDFInfo
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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
- G01B9/00—Measuring instruments characterised by the use of optical techniques
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- G01B9/02015—Interferometers characterised by the beam path configuration
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Abstract
The invention discloses a beam-splitting interferometer and an imaging light path thereof, wherein the imaging light path comprises: the first lens group is used for receiving the imaging light beam and collimating the imaging light beam to form a first collimated light beam, the dispersive element is used for expanding the collimated light beam to form a dispersive light beam, the second lens group is used for focusing the dispersive light beam to form a first focusing light beam, the third lens group is used for collimating the first focusing light beam to form a second collimated light beam, the scanning mirror is used for scanning the second collimated light beam to form a scanning light beam, the fourth lens group is used for focusing the scanning light beam to the area camera, and the controller is used for controlling the scanning frequency of the scanning mirror to be the same as the exposure frequency of the area camera; the scanning mirror changes a scanning angle, and the scanning beam of the area array camera is converted into the scanning beam of the next adjacent column of pixels. The imaging speed and the time resolution of the imaging light path are obviously improved.
Description
Technical Field
The invention relates to the technical field of optics, in particular to a beam-splitting interferometer and an imaging light path thereof.
Background
Interferometers are widely used in astronomy, optics, engineering measurements, oceanography, seismology, spectroscopy, quantum physical experiments, remote sensing, radar and other precision measurement fields. In the optical field, it is possible to measure the film thickness of an object to be measured, detect a two-dimensional or three-dimensional image of the object to be measured, and the like. However, the problem is that the interferometers in the related art are all linear array cameras, and the number of digital-to-analog conversion channels of the linear array cameras is small, so that the data acquisition rate is low, the imaging speed of the interferometers is limited to hundreds of thousands of lines/second, and the requirements of current users cannot be met.
Disclosure of Invention
The invention provides a light-splitting interferometer and an imaging light path thereof, which are used for solving the problem of relatively low imaging speed in the related technology.
To solve the above problem, an embodiment of a first aspect of the present invention provides an imaging optical path of a beam splitter interferometer, including:
the imaging device comprises a first lens group, a dispersive element, a second lens group, a third lens group, a scanning mirror, a fourth lens group, an area array camera and a controller, which are sequentially arranged along the transmission path of an imaging light beam;
the first lens group is used for receiving an imaging light beam and collimating the imaging light beam to form a first collimated light beam, the dispersive element is used for expanding the first collimated light beam to form a dispersed light beam, the second lens group is used for focusing the dispersed light beam to form a first focusing light beam, the third lens group is used for collimating the first focusing light beam to form a second collimated light beam, the scanning mirror is used for scanning the second collimated light beam to form a scanning light beam, the fourth lens group is used for focusing the scanning light beam to the area array camera, and the controller is electrically connected with the scanning mirror and the area array camera and used for controlling the scanning frequency of the scanning mirror to be the same as the exposure frequency of the area array camera; the area array camera is positioned on the image space focal plane of the fourth lens group;
wherein the scanning mirror changes a scanning angle, and the scanning light beam sampled by the last column of pixels of the area array camera is converted into the scanning light beam sampled by the next column of pixels adjacent to the last column of pixels.
Optionally, the dispersive element is located at an object-side focal plane of the second lens group, the image-side focal plane of the second lens group is co-located with the object-side focal plane of the third lens group, the scanning mirror is located at the image-side focal plane of the third lens group, or the scanning mirror is located at the image-side focal plane of the third lens group and also located at the object-side focal plane of the fourth lens group.
Optionally, the first lens group comprises at least one lens; the second lens group includes at least one lens; the third lens group includes at least one lens; the fourth lens group includes at least one lens.
Optionally, the first lens group is a reflective lens group or a transmissive lens group, the second lens group is a reflective lens group or a transmissive lens group, the third lens group is a reflective lens group or a transmissive lens group, and the fourth lens group is a reflective lens group or a transmissive lens group.
Optionally, the dispersion element is one of a grating, a prism, a diffraction beam splitter or a super surface material optical beam splitter, and the dispersion element is a reflective dispersion element or a transmissive dispersion element.
Optionally, the scanning mirror is one of a galvanometer scanning galvanometer, a resonance galvanometer, a MEMS galvanometer, a polygon turning mirror, an electro-optic deflector or an acousto-optic deflector.
In order to solve the above problem, an embodiment of a second aspect of the present invention provides an optical splitting interferometer, including: the imaging light path, the wide-spectrum light source, the optical fiber coupler, the reference light path and the sample light path of the light-splitting interferometer of any embodiment of the invention;
the light source input end of the optical fiber coupler is connected with the wide spectrum light source, the sample end of the optical fiber coupler is connected with the sample light path, the reference end of the optical fiber coupler is connected with the reference light path, and the coupling end of the optical fiber coupler is connected with the imaging light path;
the wide-spectrum light source is used for emitting a wide-spectrum light beam, the optical fiber coupler is used for leading in the wide-spectrum light beam and dividing the wide-spectrum light beam into a reference light beam and a sample light beam, the reference light beam is used in a reference light path and reflected by the reference light path to form a reference reflected light beam, and the sample light beam is used in a sample light path and emitted by the sample light path to form a sample reflected light beam; the fiber coupler is further configured to couple the reference reflected beam and the sample reflected beam to form an imaging beam, and the imaging optical path is configured to image based on the imaging beam.
Optionally, the reference light path includes: the optical fiber coupler comprises a fifth lens group, a sixth lens group and a reference reflector, wherein the fifth lens group is used for collimating the reference beam to the sixth lens group, the sixth lens group is used for focusing the reference beam to the reference reflector, the reference reflector is used for reflecting the reference beam to form a reference reflected beam to the sixth lens group, the sixth lens group is also used for collimating the reference reflected beam to the fifth lens group, and the fifth lens group is also used for focusing the reference reflected beam to a reference end of the optical fiber coupler.
Optionally, the sample optical path includes: the optical fiber coupler comprises a seventh lens group, a scanning vibrating mirror and an eighth lens group, wherein the seventh lens group is used for collimating a sample light beam to the scanning vibrating mirror, the scanning vibrating mirror scans the sample light beam to the eighth lens group, the eighth lens group is used for focusing the sample light beam to a sample to be detected, the sample light beam to be detected is reflected to form a sample reflection light beam to the eighth lens group, the eighth lens group is also used for collimating the sample reflection light beam to the scanning vibrating mirror, the scanning vibrating mirror scans the sample reflection light beam to the seventh lens group, and the seventh lens group is also used for focusing the sample reflection light beam to a sample end of the optical fiber coupler.
Optionally, the scanning galvanometer is one of a galvanometer scanning galvanometer, a resonance galvanometer and an MEMS galvanometer, and the scanning frequency of the scanning galvanometer is the same as that of the scanning mirror.
According to the beam-splitting interferometer and the imaging optical path thereof provided by the embodiment of the invention, the imaging optical path comprises: the imaging device comprises a first lens group, a dispersive element, a second lens group, a third lens group, a scanning mirror, a fourth lens group, an area array camera and a controller, which are sequentially arranged along the transmission path of an imaging light beam; the first lens group is used for receiving the imaging light beam and collimating the imaging light beam to form a first collimated light beam, the dispersive element is used for expanding the collimated light beam to form a dispersive light beam, the second lens group is used for focusing the dispersive light beam to form a first focusing light beam, the third lens group is used for collimating the first focusing light beam to form a second collimated light beam, the scanning mirror is used for scanning the second collimated light beam to form a scanning light beam, the fourth lens group is used for focusing the scanning light beam to the area camera, and the controller is electrically connected with the scanning mirror and the area camera and is used for controlling the scanning frequency of the scanning mirror to be the same as the exposure frequency of the area camera; wherein the scanning mirror changes a scanning angle, and the scanning light beam sampled by the last column of pixels of the area array camera is converted into the scanning light beam sampled by the next column of pixels adjacent to the last column of pixels. Thus, the imaging speed and time resolution of the interferometer are significantly improved by the use of the scanning mirror and the area camera.
It should be understood that the description in this section is not intended to identify key or critical features of the embodiments of the invention or to delineate the scope of the invention. Other features of the present invention will become apparent from the description that follows.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of an imaging optical path of a beam splitter interferometer according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of capturing a scanning beam by an area camera in an imaging optical path of a beam splitting interferometer according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a beam-splitting interferometer according to an embodiment of the present invention.
Detailed Description
In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprise" and "have," as well as any variations thereof, are intended to cover a non-exclusive inclusion.
Fig. 1 is a schematic optical path diagram of an imaging optical path of a beam splitter interferometer according to an embodiment of the present invention. As shown in fig. 1, an imaging optical path 100 of the optical splitting interferometer includes:
a first lens group 101, a dispersive element 102, a second lens group 103, a third lens group 104, a scanning mirror 105, a fourth lens group 106, an area camera 107 and a controller 108 are sequentially arranged along a path along which the imaging light beam 001 is transmitted;
the first lens group 101 is used for receiving the imaging light beam 001 and collimating the imaging light beam 001 to form a first collimated light beam 002, the dispersive element 102 is used for expanding the first collimated light beam 002 to form a dispersed light beam 003, the second lens group 103 is used for focusing the dispersed light beam 003 to form a first focusing light beam 004, the third lens group 104 is used for collimating the first focusing light beam 004 to form a second collimating light beam 005, the scanning mirror 105 is used for scanning the second collimating light beam 005 to form a scanning light beam 006, the fourth lens group 106 is used for focusing the scanning light beam 006 to the area camera 107, the controller 108 is electrically connected with the scanning mirror 105 and the area camera 107 and is used for controlling the scanning frequency of the scanning mirror 105 to be the same as the exposure frequency of the area camera 107; the area array camera 107 is located on the image side focal plane of the fourth lens group 106;
wherein the scanning mirror 105 changes a scanning angle, the area camera 107 is converted from the last column of pixel sampling scanning beams 006 to the next adjacent column of pixel sampling scanning beams 006.
It should be noted that, the first focusing light beam 004 focuses to form a thin spectral line at the focal plane of the image side of the second lens group 103. And then collimated by the third lens group 104 into a second collimated beam 005. The light of a single wavelength of the second collimated beam 005 is collimated but is concentrated between different wavelengths, which will be concentrated and superimposed at the scanning mirror 105, after which the collimated light is separated between the different wavelengths. And then focused by the fourth lens group 106 into a thin spectral line (focused on a column of pixels of the area camera 107).
It will be appreciated that the imaging beam 001 of the interferometer varies with the point to be measured of the object to be measured, and that, for example, there are two points to be measured, the imaging beam 001 includes a first imaging beam and a second imaging beam. As shown in fig. 2, the area camera 107 includes photosensitive elements 109 arranged along rows and columns, and the first imaging beam sequentially passes through the first lens group 101, the dispersive element 102, the second lens group 103 and the third lens group 104, then strikes the scanning mirror 105, is scanned by the scanning mirror 105, and is focused onto a row of pixels on the area camera 107 by passing through the fourth lens group 106 (as in fig. 2, the first scanning beam 0061 is focused onto the photosensitive elements 109 corresponding to a row of pixels). After the imaging light beam 001 sampled in the current period changes, the second imaging light beam sequentially passes through the first lens group 101, the dispersive element 102, the second lens group 103 and the third lens group 104, then strikes the scanning mirror 105, is scanned by the scanning mirror 105, and is focused onto the next row of pixels on the area camera 107 through the fourth lens group 106 (as in fig. 2, the second scanning light beam 0062 is focused onto the photosensitive element 109 corresponding to the other row of pixels), and the moving direction is shown as the x direction in fig. 2. Further, as the point to be measured of the object to be measured in the early stage of the interferometer changes, the scanning beam 006 of each sampling can be on the photosensitive element 109 corresponding to one row of pixels of the area camera 107 by scanning the scanning mirror 105 in the imaging optical path 100. Thus, the imaging speed is greatly improved relative to a linear camera. In this embodiment, the size of the photosensitive element 109 in the x-direction is larger than the width of the spectral line itself, and the size of the plurality of photosensitive elements 109 in the direction perpendicular to the x-direction (i.e., the column direction in fig. 2) is larger than the length of the spectral line itself. The scan mirror 105 changes an angle such that the spectral line reflected from it can move from the last column of pixels to the next column of pixels. Wherein the scanning period of the scanning mirror 105 is synchronized with the exposure period of the area camera 107.
It should be noted that, the dispersive element 102 is located between the first lens group 101 and the second lens group 103 and in front of the scanning mirror 105, which is advantageous to maintain the angle between the collimated light beam 002 and the dispersive element 102, that is, to maintain the same incident angle of the collimated light beam 002 into the dispersive element 102, so that the exit angle of the light beams with different wavelengths after being dispersed by the dispersive element 102 is fixed and does not change due to the change of the incident angle of the first collimated light beam 002 into the dispersive element. This is focused by the second lens group 103, then collimated by the third lens group 104, and then scanned by the scanning mirror 105 (i.e., the incidence angle of the second collimated beam 005 on the scanning mirror 105 is changed), thereby changing the position of the spectral line on the area camera 107. In addition, by providing the fourth lens group 106 between the scanning mirror 105 and the area camera 107, the area camera 107 is positioned on the image-side focal plane of the fourth lens group 106, and the focusing by the fourth lens group 106 can be clearly focused on the pixel plane of the area camera 107 no matter where the scanning beam 006 is positioned on the fourth lens group 106. That is, when the second collimated light beam 005 reaches the scan mirror 105, the light beam of a single wavelength is collimated, but is focused between different wavelengths. Upon exiting the scan mirror 105, the single wavelength beam is collimated, but is dispersed between different wavelengths. And then focused by the fourth lens group 106 into a thin spectral line (focused on a column of pixels of the area camera 107).
In addition, if the scanning mirror 105 is located at the object focal plane of the fourth lens group 106, it will act like an image telecentric lens, and the scanning beam 006, after being focused by the fourth lens group 106, will be vertically incident on the pixel plane.
And the controller 108 controls the scanning frequency of the scanning mirror 105 to be the same as the exposure frequency of the area camera 107, that is, in one scanning period of the scanning mirror 105, the area camera 107 is in the exposure period, and further, the scanning light beams 006 continuously scanned by the scanning mirror 105 can be sequentially exposed by different rows of pixels of the area camera 107, so that the scanning light beams and the area camera are synchronous, thereby being beneficial to improving the imaging speed.
The photosensitive element 109 may be a CCD or CMOS photosensitive element. Optionally, the dispersive element 102 is one of a grating, a prism, a diffraction spectroscopy device, or a super-surface material optical spectroscopy device, and the dispersive element 102 is a reflective dispersive element or a transmissive dispersive element. The design of the light path change is facilitated, for example, the volume reduction of the whole light path is facilitated.
Alternatively, the scanning mirror 105 is one of a galvanometer scanning galvanometer, a resonant galvanometer, a MEMS galvanometer, a polygon mirror, an electro-optic deflector, or an acousto-optic deflector.
In summary, the imaging optical path of the interferometer provided by the embodiment of the invention can be obviously improved in imaging quality and imaging speed.
Optionally, with continued reference to fig. 1, the dispersive element 102 is located at the object-side focal plane of the second lens group 103, the image Fang Jiaomian of the second lens group 103 is co-located with the object-side focal plane of the third lens group 104, and the scanning mirror 105 is located at the image-side focal plane of the third lens group 104. Alternatively, the scanning mirror is located at the image side focal plane of the third lens group and is also located at the object side focal plane of the fourth lens group.
The image Fang Jiaomian of the second lens group 103 is co-located with the object focal plane of the third lens group 104, such that the dispersed light beam 003 is focused into a spectral line after the second lens group 103. The scanning mirror 105 is located at the focal plane of the image side of the third lens group 104, so that when the second collimated light beam 005 reaches the scanning mirror 105, light beams with different wavelengths are in a converging state, and after being scanned by the scanning mirror 105, the scanning light beam 006 can be collimated to reach the fourth lens group 106, and finally focused on the area camera 107 to form a clear spectral line. If the scanning mirror 105 is located at the object focal plane of the fourth lens group 106, an effect similar to that of an image telecentric lens is achieved, and the scanning beam 006, after being focused by the fourth lens group 106, is perpendicularly incident to the pixel plane, so as to be beneficial to improving the brightness of the image.
Optionally, with continued reference to fig. 1, the first lens group 101 includes at least one lens; the second lens group 103 includes at least one lens; the third lens group 104 includes at least one lens; the fourth lens group 106 includes at least one lens.
The lens may be a convex lens. The lens can also be a cemented lens combined by different lenses, and can meet the focusing and collimating functions, and the invention is not particularly limited to the above. The first lens group 101 is a collimating lens group, the second lens group 103 is a focusing lens group, the third lens group 104 is a collimating lens group, and the fourth lens group 106 is a focusing lens group.
Optionally, the first lens group 101 is a reflective lens group or a transmissive lens group, the second lens group 102 is a reflective lens group or a transmissive lens group, the third lens group 103 is a reflective lens group or a transmissive lens group, and the fourth lens group 104 is a reflective lens group or a transmissive lens group.
Wherein, by reasonably configuring the reflected or transmitted light beams of the first lens group 101, the second lens group 102, the third lens group 103 and the fourth lens group 104, the design of the light path change is facilitated, such as the reduction of the volume of the whole light path is facilitated.
With continued reference to fig. 1, in fig. 1, the first lens group 101, the second lens group 102, the third lens group 103, and the fourth lens group 104 are all transmissive lens groups. If the light path is required to be turned back, one or more of the lens groups can be arranged as a reflection lens group, namely, the reflection surface of the lens group can be coated with a reflection coating to realize reflection. Alternatively, a mirror is disposed between each lens group to realize the trend of the light path.
Fig. 3 is a schematic structural diagram of a beam-splitting interferometer according to an embodiment of the present invention. As shown in fig. 3, the optical interferometer 200 includes: the imaging light path 100, the broad spectrum light source 201, the optical fiber coupler 202, the reference light path 203 and the sample light path 204 of the light-splitting interferometer of any embodiment of the invention;
the light source input end of the optical fiber coupler 202 is connected with the broad spectrum light source 201, the sample end of the optical fiber coupler 202 is connected with the sample light path 204, the reference end of the optical fiber coupler 202 is connected with the reference light path 203, and the coupling end of the optical fiber coupler 202 is connected with the imaging light path 100;
the broad spectrum light source 201 is used for emitting a broad spectrum light beam, the optical fiber coupler 202 is used for leading in the broad spectrum light beam and dividing the broad spectrum light beam into a reference light beam and a sample light beam, the reference light beam is used in the reference light path 203 and reflected by the reference light path 203 to form a reference reflected light beam, and the sample light beam is used in the sample light path 204 and emitted by the sample light path 204 to form a sample reflected light beam; the fiber coupler 202 is also used to couple the reference reflected beam and the sample reflected beam to form an imaging beam, and the imaging optical path 100 is used to image based on the imaging beam.
Since the optical splitter interferometer uses the imaging optical path 100 of the embodiment of the present invention, the imaging speed and imaging quality of the interferometer are improved.
Optionally, with continued reference to fig. 3, the reference optical path 203 includes: a fifth lens group 2031, a sixth lens group 2032 and a reference mirror 2033, the fifth lens group 2031 being for collimating a reference beam to the sixth lens group 2032, the sixth lens group 2032 being for focusing the reference beam to the reference mirror 2033, the reference mirror 2033 being for reflecting the reference beam to form a reference reflected beam to the sixth lens group 2032, the sixth lens group 2032 also being for collimating the reference reflected beam to the fifth lens group 2031, the fifth lens group 2031 also being for focusing the reference reflected beam to a reference end of the fiber coupler 202.
Optionally, with continued reference to fig. 3, the sample optical path 204 includes: the seventh lens group 2041, the scanning galvanometer 2042 and the eighth lens group 2043, wherein the seventh lens group 2041 is used for collimating the sample beam to the scanning galvanometer 2042, the scanning galvanometer 2042 is used for scanning the sample beam to the eighth lens group 2043, the eighth lens group 2043 is used for focusing the sample beam to the sample 300 to be measured, the sample 300 to be measured reflects the sample beam to form a sample reflected beam to the eighth lens group 2043, the eighth lens group 2043 is also used for collimating the sample reflected beam to the scanning galvanometer 2042, the scanning galvanometer 2042 is used for scanning the sample reflected beam to the seventh lens group 2041, and the seventh lens group 2041 is also used for focusing to the sample end of the fiber coupler 202.
Optionally, the scanning galvanometer 2042 is one of a galvanometer scanning galvanometer, a resonant galvanometer, and a MEMS galvanometer, and the scanning frequency of the scanning galvanometer 2043 is the same as the scanning frequency of the scanning mirror 105.
It can be understood that the broad spectrum light source 201 may be an SLD light source, and the light beam emitted from the broad spectrum light source 201 is divided into a sample light beam and a reference light beam by the optical fiber coupler 202, and the sample light beam is scanned in the x-y direction by the scanning galvanometer 2042 in the sample light path 204, so as to realize the whole scanning of the sample 300 to be measured. The reference beam is incident on a reference mirror 2033 via a reference optical path 203. The sample reflected light beam reflected or backscattered by the sample 300 to be measured returns to the optical fiber coupler 202 in the original path, the reference reflected light beam reflected by the reference mirror 2033 returns to the optical fiber coupler 202 in the original path, the two returned lights are mixed and overlapped in the optical fiber coupler 202 to generate interference, and the interference light is led out from one optical fiber in the optical fiber coupler 202 to the imaging optical path 100. The fifth lens group 2031 to the eighth lens group 2043 each include at least one lens.
Wherein the interference light is collimated into a parallel beam by a first lens group 101 in an imaging optical path 100 and then irradiated on a dispersive element 102. The dispersive element 102 spreads the beam dispersions of different wavelengths in the parallel beam into different directions. Wherein, the dispersion element 102 can be a grating, a prism, a diffraction device, or an optical device such as a super surface material which can generate dispersion effect on light with different wavelengths; the dispersive element may be transmissive or reflective.
The light beams of different wavelengths dispersed and spread by the dispersive element 102 are incident on the second lens group 103, and the dispersive element 102 is located at the object focal plane of the second lens group 103. The second lens group 103 focuses parallel light beams with different wavelengths at the focal plane of the image side of the second lens group 103, each wavelength of light is focused by the second lens group 103 into a point, and all wavelengths of light are focused by the second lens group 103 into an intermediate spectral line. The second lens group 103 may be transmissive or reflective, and the second lens group 103 includes at least one lens.
The intermediate spectral lines then diverge and are incident on the third lens set 104. The object-side focal plane of the third lens group 104 and the image-side focal plane of the second lens group 103 coincide. Thus, the third lens group 104 collimates each wavelength of light into a parallel beam; however, these parallel light beams with different wavelengths are converged and overlapped at the focal plane of the image side of the third lens group 104. The third lens group 104 can be transmissive or reflective, and the third lens group 104 can include at least one lens.
At the image side focal plane of the third lens group 104, a scanning mirror 105 is disposed, and the scanning mirror 105 may be a galvanometer scanning mirror (for example, a galvanometer scanning mirror, a resonance mirror, or a MEMS mirror, etc.), a rotating polygon mirror, an electro-optical deflector, or an acousto-optical deflector, etc.
The parallel light beams with different wavelengths are converged and overlapped with each other, and then dispersed after being reflected by the scanning mirror 105 (i.e. at the focal plane of the image side of the third lens group 104). Continuing to be incident on the fourth lens group 106, the fourth lens group 106 focuses the parallel light beams with different wavelengths at the image-side focal plane of the fourth lens group 106 to form a spectral line (interference spectrum). The fourth lens group 106 can be transmissive or reflective, and the fourth lens group 106 can include at least one lens.
An area camera 107 is used to receive the spectral line, and an area image sensor chip in the area camera 107 is located at the focal plane of the image side of the fourth lens group 106, so that a clear spectral line can be obtained, and a spectral line can be received by an in-line pixel of the area camera 107. The area camera 107 includes an area image sensor (which may be a CCD, CMOS, NMOS, or other type of area image sensor).
The scanning period of the scanning mirror 105 and the exposure period of the area camera 107 are synchronized using an electric signal. When the scanning mirror 105 scans the light beam, the spectral lines are scanned and moved on the area array image sensor, so that the spectral lines sequentially irradiate pixels of different lines of the area array image sensor at different times in one scanning period of the scanning mirror 105. Thus, the planar array image sensor is scanned line by line in one scanning period of the scanning mirror 105, and a spectrum (interference spectrum) of a plurality of lines at different times can be obtained.
The interference spectrum data acquired by the area camera 107 is transmitted to a processor or computer or controller 108 for processing as follows: resampling the wave number space of each line of interference spectrum data to obtain interference spectrum data of linear sampling in the wave number space; then, fourier transformation is performed on the interference spectrum data of the linear sampling of each line wave number space, so that reflectivity information and phase information of the sample in the depth direction (Z direction) can be obtained.
If the scanning period of the XY scanning galvanometer 2042 for scanning the sample in the X direction, the scanning period of the scanning mirror 105 for scanning the spectrum, and the exposure period of the area camera 107 are synchronized, one frame of 2D tangential plane image (including reflectivity information and phase information) of the sample 300 to be measured in the XZ direction can be obtained after each frame of interference spectrum data obtained by the area camera 107 is subjected to the above data processing. If the scanning in the Y direction of the sample 300 to be measured is added to the XY scanning mirror, a 3D image (including reflectivity information and phase information) of three dimensions X, Z and Y of the sample 300 to be measured can be reconstructed.
Compared to a beam-splitting interferometer using a line camera, a higher imaging speed (2 orders of magnitude higher) can be achieved because an area camera can employ a greater number of digital-to-analog conversion (ADC) channels than a line camera, typically with a greater data acquisition rate (which can be 2 orders of magnitude higher).
In addition, the spectrum of the light-splitting interferometer is scanned on the area array camera by adopting the scanning mirror, and the scanning speed of the scanning mirror is very high in general, even if an area array camera with very low frame rate is used for obtaining a 2D section picture of a single frame of a sample, the effective exposure time is very short, the time resolution is very high, and the light-splitting interferometer is suitable for imaging a high-dynamic morphology.
In some embodiments, the optical interferometer can realize defect detection and precise measurement of 3C electronic products in the field of industrial detection, such as detection of a printed circuit board, layering detection of a screen, detection of a mobile phone lens and the like. The detection of burrs of a pole piece of a lithium battery, the detection of alignment of the pole piece or the pole lug, and the detection of weld defects of a lithium battery shell are realized in the detection field of the lithium battery. The technology can realize real-time detection of the welding line in the laser welding process, and can detect the welding line while carrying out laser welding due to the immunity of the technology to stray light. Defect detection such as chip packaging is implemented in the field of semiconductor inspection. But also in biomedical fields such as ophthalmic tomographic imaging, dental tomographic imaging, skin tomographic imaging, and small animal tomographic imaging.
In summary, according to the optical interferometer and the imaging optical path thereof provided by the embodiments of the present invention, the imaging optical path includes: the imaging device comprises a first lens group, a dispersive element, a second lens group, a third lens group, a scanning mirror, a fourth lens group, an area array camera and a controller, which are sequentially arranged along the transmission path of an imaging light beam; the first lens group is used for receiving the imaging light beam and collimating the imaging light beam to form a first collimated light beam, the dispersive element is used for expanding the collimated light beam to form a dispersive light beam, the second lens group is used for focusing the dispersive light beam to form a first focusing light beam, the third lens group is used for collimating the first focusing light beam to form a second collimated light beam, the scanning mirror is used for scanning the second collimated light beam to form a scanning light beam, the fourth lens group is used for focusing the scanning light beam to the area camera, and the controller is electrically connected with the scanning mirror and the area camera and is used for controlling the scanning frequency of the scanning mirror to be the same as the exposure frequency of the area camera; the area array camera is positioned on the image side focal plane of the fourth lens group, the scanning mirror changes a scanning angle, and the scanning beam of the area array camera is converted into the scanning beam of the next adjacent array of pixel sampling. Thus, the imaging speed and time resolution of the interferometer are significantly improved by the use of the scanning mirror and the area camera.
The above embodiments do not limit the scope of the present invention. It will be apparent to those skilled in the art that various modifications, combinations, sub-combinations and alternatives are possible, depending on design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of the present invention.
Claims (10)
1. An imaging optical path of a beam-splitting interferometer, comprising:
the imaging device comprises a first lens group, a dispersive element, a second lens group, a third lens group, a scanning mirror, a fourth lens group, an area array camera and a controller, which are sequentially arranged along the transmission path of an imaging light beam;
the first lens group is used for receiving an imaging light beam and collimating the imaging light beam to form a first collimated light beam, the dispersive element is used for expanding the first collimated light beam to form a dispersed light beam, the second lens group is used for focusing the dispersed light beam to form a first focusing light beam, the third lens group is used for collimating the first focusing light beam to form a second collimated light beam, the scanning mirror is used for scanning the second collimated light beam to form a scanning light beam, the fourth lens group is used for focusing the scanning light beam to the area array camera, and the controller is electrically connected with the scanning mirror and the area array camera and used for controlling the scanning frequency of the scanning mirror to be the same as the exposure frequency of the area array camera; the area array camera is positioned on the image space focal plane of the fourth lens group;
wherein the scanning mirror changes a scanning angle, and the scanning light beam sampled by the last column of pixels of the area array camera is converted into the scanning light beam sampled by the next column of pixels adjacent to the last column of pixels.
2. An imaging optical path of a beam-splitting interferometer according to claim 1, wherein the dispersive element is located at the object-side focal plane of the second lens group, the image-side focal plane of the second lens group is co-located with the object-side focal plane of the third lens group, the scanning mirror is located at the image-side focal plane of the third lens group, or the scanning mirror is located at the image-side focal plane of the third lens group and also at the object-side focal plane of the fourth lens group.
3. The imaging optical path of a beam-splitting interferometer according to claim 1 or 2, wherein the first lens group comprises at least one lens; the second lens group includes at least one lens; the third lens group includes at least one lens; the fourth lens group includes at least one lens.
4. The imaging optical path of a beam splitter interferometer of claim 1, wherein the first lens group is a reflective or transmissive lens group, the second lens group is a reflective or transmissive lens group, the third lens group is a reflective or transmissive lens group, and the fourth lens group is a reflective or transmissive lens group.
5. The imaging optical path of a beam-splitting interferometer according to claim 1, wherein the dispersive element is one of a grating, a prism, a diffraction beam splitter, or a super-surface material optical beam splitter, and the dispersive element is a reflective dispersive element or a transmissive dispersive element.
6. The imaging optical path of a beam-splitting interferometer according to claim 1, wherein the scanning mirror is one of a galvanometer scanning galvanometer mirror, a resonant galvanometer, a MEMS galvanometer, a polygonal turning mirror, an electro-optic deflector, or an acousto-optic deflector.
7. A beam-splitting interferometer comprising: an imaging optical path, a broad spectrum light source, a fiber coupler, a reference optical path, a sample optical path of a beam splitter interferometer according to any of claims 1-6;
the light source input end of the optical fiber coupler is connected with the wide spectrum light source, the sample end of the optical fiber coupler is connected with the sample light path, the reference end of the optical fiber coupler is connected with the reference light path, and the coupling end of the optical fiber coupler is connected with the imaging light path;
the wide-spectrum light source is used for emitting a wide-spectrum light beam, the optical fiber coupler is used for leading in the wide-spectrum light beam and dividing the wide-spectrum light beam into a reference light beam and a sample light beam, the reference light beam is used in a reference light path and reflected by the reference light path to form a reference reflected light beam, and the sample light beam is used in a sample light path and emitted by the sample light path to form a sample reflected light beam; the fiber coupler is further configured to couple the reference reflected beam and the sample reflected beam to form an imaging beam, and the imaging optical path is configured to image based on the imaging beam.
8. The optical splitter interferometer of claim 7, wherein the reference optical path comprises: the optical fiber coupler comprises a fifth lens group, a sixth lens group and a reference reflector, wherein the fifth lens group is used for collimating the reference beam to the sixth lens group, the sixth lens group is used for focusing the reference beam to the reference reflector, the reference reflector is used for reflecting the reference beam to form a reference reflected beam to the sixth lens group, the sixth lens group is also used for collimating the reference reflected beam to the fifth lens group, and the fifth lens group is also used for focusing the reference reflected beam to a reference end of the optical fiber coupler.
9. The optical splitter interferometer of claim 7, wherein the sample optical path comprises: the optical fiber coupler comprises a seventh lens group, a scanning vibrating mirror and an eighth lens group, wherein the seventh lens group is used for collimating a sample light beam to the scanning vibrating mirror, the scanning vibrating mirror scans the sample light beam to the eighth lens group, the eighth lens group is used for focusing the sample light beam to a sample to be detected, the sample light beam to be detected is reflected to form a sample reflection light beam to the eighth lens group, the eighth lens group is also used for collimating the sample reflection light beam to the scanning vibrating mirror, the scanning vibrating mirror scans the sample reflection light beam to the seventh lens group, and the seventh lens group is also used for focusing the sample reflection light beam to a sample end of the optical fiber coupler.
10. The optical splitter interferometer of claim 7, wherein the scanning galvanometer is one of a galvanometer scanning galvanometer, a resonant galvanometer, and a MEMS galvanometer, and wherein the scanning frequency of the scanning galvanometer is the same as the scanning frequency of the scanning mirror.
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