CN115014210A - Compensation light path structure for improving measurement precision - Google Patents
Compensation light path structure for improving measurement precision Download PDFInfo
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- 238000005259 measurement Methods 0.000 title claims abstract description 147
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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
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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
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- G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
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Abstract
The utility model discloses a compensation light path structure for improving measurement accuracy, the rebuild device includes the measurement light path structure and the compensation light path structure that are used for acquireing the initial height of target point, compensation light path structure includes first generation module, beam splitting module, interference objective, and data processing module, first generation module is used for producing the compensation beam that the bandwidth is not more than first default, beam splitting module includes first beam splitting unit and second beam splitting unit, first beam splitting unit is configured to receive the compensation beam and reflects the compensation beam to interference objective, the compensation beam forms the compensation reflection beam at interference objective, data processing module compensates initial height based on the compensation reflection beam in order to obtain comprehensive measurement height. According to the present disclosure, a compensation optical path structure that compensates for a measurement height of a target point to improve measurement accuracy of the target point can be provided.
Description
Technical Field
The present disclosure relates to an intelligent manufacturing equipment industry, and more particularly, to a compensation optical path structure for improving measurement accuracy.
Background
With the development of ultra-precision machining technology, ultra-precision detection technology is also becoming more important. The optical measurement method is widely applied to the field of optical measurement due to the advantages of low cost and high precision. Among them, an optical measurement system based on the interference principle has the advantages of high accuracy and high resolution, and is often used for accurate measurement of physical quantities.
The white light interferometer is an ultra-precise measurement device based on a white light interferometry technology, and in the prior art, the white light interferometer usually adopts a single white light source to measure the height of an object to be measured. In the measurement scanning process, if the optical path difference between the measurement light and the reference light is smaller than the coherence length of the white light source, the two beams of light can interfere to generate a white light interference signal. When the optical path difference between the measurement light and the reference light is equal to zero, the intensity of the interference signal reaches a maximum. Therefore, the height information of the object to be measured can be obtained through the zero optical path difference position.
However, the measurement precision and accuracy of the white light interferometer are obviously influenced by the environment. Generally speaking, the environmental impact includes two aspects of industrial environmental impact and natural environmental impact, wherein the industrial environmental impact refers to that the ground generates low-frequency vibration due to vibration caused by people and surrounding environment, and then the low-frequency vibration is transferred to the interferometer; the natural environment influence refers to that the interferometer generates certain vibration due to the change of the natural environment, such as air flow, temperature change and the like. The two types of vibration caused by environmental influence belong to environmental vibration. When environmental vibration exists, white light interference fringes generated based on a white light interferometer are prone to generate jitter, for example, interference fringe images are mutually overlapped, deformed, repaired, blurred or burred, and the like, so that a measurement result has large errors; furthermore, the large amplitude of the fringe fluctuation of the plurality of interference patterns will make the interference fringes invisible and impossible to measure.
Disclosure of Invention
The present disclosure has been made in view of the above-described state of the art, and an object thereof is to provide a compensation optical path structure capable of compensating for a measurement height of a target point to improve measurement accuracy of the target point.
The present disclosure provides a compensating optical path structure for improving measurement accuracy when a reconstruction device measures the height of a target point, the reconstruction means comprise a measurement optical path structure for acquiring an initial height of the target point and the compensation optical path structure, the compensation optical path structure comprises a first generation module, a light splitting module, an interference objective lens and a data processing module, the first generation module is used for generating a compensation light beam with the bandwidth not greater than a first preset value, the light splitting module comprises a first light splitting unit and a second light splitting unit, the first beam splitting unit is configured to receive the compensation beam and reflect the compensation beam to the interference objective lens where the compensation beam forms a compensation reflected beam, the data processing module compensates the initial height based on the compensated reflected beam to obtain a composite measured height.
In this case, vibration information of the target point due to environmental vibration can be obtained, and the vibration information can be calculated in a visual form, so that the initial height of the target point can be compensated based on the vibration information to obtain a comprehensive measurement height. In addition, the reconstruction device according to the present embodiment can reconstruct the three-dimensional shape of the object based on the integrated measurement height of the target point, and thus can improve the reconstruction accuracy of the object by the reconstruction device.
In addition, in the compensation optical path structure according to the present disclosure, optionally, a first receiving module in signal connection with the data processing module is further included, and the first receiving module is configured to receive the compensation reflected light beam reflected by the second light splitting unit and form a compensation interference signal. Thereby, the compensation optical path structure is able to compensate the initial height of the target point based on the compensation interference signal. In this case, the data processing module may perform signal processing based on the compensation reflected light beam to calculate compensation information of the target point due to the environmental vibration and compensate for the initial height. This can improve the accuracy of the measurement of the height of the target point by the reconstruction device.
In the optical compensation path structure according to the present disclosure, the first receiving module may include a first receiving unit and a first lens unit, and the first lens unit may be disposed between the first receiving unit and the second beam splitting unit. In this case, the first lens unit is capable of focusing the compensating reflected light beam on the first receiving unit, which is capable of converting the received compensating reflected light beam into a compensating interference signal.
In addition, in the compensated optical path structure according to the present disclosure, optionally, the data processing module is configured to obtain compensation information based on the compensated interference signal, and compensate the initial height based on the compensation information to obtain a comprehensive measured height. In this case, the data processing module may perform signal processing based on the compensation reflected light beam to calculate compensation information of the target point due to the environmental vibration and compensate for the initial height. This can improve the accuracy of measuring the height of the target point by the reconstruction device.
In addition, in the compensation optical path structure according to the present disclosure, optionally, the interference objective lens includes a third light splitting unit configured to receive the compensation beam and split the compensation beam into a first compensation beam reflected to the reference unit and a second compensation beam transmitted to the target point; the first compensation target beam is reflected to the reference unit through the third light splitting unit and reflected by the reference unit to form a first compensation reflected beam, the second compensation target beam is transmitted to the target point through the third light splitting unit and reflected by the target point to form a second compensation reflected beam, and the first compensation reflected beam and the second compensation reflected beam form a compensation reflected beam. In this case, the compensation beam can be decomposed into a first compensation beam and a second compensation beam after reaching the interference object mirror, wherein the first compensation beam can be reflected to the reference unit via the third reflection unit, and the second compensation beam can be transmitted to the target point via the third reflection unit, and since the first compensation beam and the second compensation beam reach different places, the first compensation reflected beam and the second compensation reflected beam formed by the first compensation beam and the second compensation beam through reflection can have an optical path difference.
In addition, in the compensation optical path structure according to the present disclosure, optionally, the measurement optical path structure includes a second generation module, the splitting module, the interference objective lens, the data processing module, and a second receiving module, the second generation module is configured to generate a measurement beam having a bandwidth not less than a second preset value, the first preset value is not greater than the second preset value, the first splitting unit is further configured to receive the measurement beam and reflect the measurement beam to the interference objective lens, the measurement beam forms a measurement reflected beam at the interference objective lens, the second receiving module is configured to receive the measurement reflected beam transmitted through the second splitting unit, and the data processing module obtains the initial height of the target point based on the measurement reflected beam. In this case, in the measuring optical path structure, the first measuring reflected light beam and the second measuring reflected light beam can interfere to form a measuring interference signal, and the data processing unit can obtain the initial height of the target point based on the generated measuring interference signal.
In addition, in the compensated optical path structure according to the present disclosure, optionally, the reconstruction apparatus further includes a coupling unit configured to receive the compensation beam and the measurement beam and couple the compensation beam and the measurement beam. In this case, the compensation beam and the measuring beam can be coupled by the coupling unit to be one beam to be transmitted to the first beam splitting unit, and then the compensation beam and the measuring beam can be made to synchronously reach the interference objective lens, and the compensation reflected beam and the measurement reflected beam are synchronously formed, which is advantageous for obtaining compensation information more accurately matched with the initial height of the target point.
In addition, in the compensation optical path structure according to the present disclosure, optionally, the measurement apparatus further includes a timing synchronization unit configured to send a control signal to the first receiving module and the second receiving module so that the first receiving module and the second receiving module receive the compensation reflected light beam and the measurement reflected light beam synchronously.
In addition, in the compensation optical path structure according to the present disclosure, optionally, a response time of the first receiving module to one optical signal is not greater than a response time of the second receiving module to one optical signal. In this case, the first receiving module and the second receiving module can receive optical signals synchronously, and thus compensation information monitored by the compensation optical path structure can be synchronized with measurement information of the measurement optical path structure, further improving the overall measurement accuracy of the reconstruction apparatus.
In addition, in the compensated optical path structure according to the present disclosure, optionally, the reconstruction apparatus further includes a driving module configured to adjust a relative position of the interference objective lens and the target point. In this case, the relative position of the interference objective and the target point can be varied, so that the initial height of the target point can be obtained on the basis of the measurement reflected beam, and the target point is compensated on the basis of the compensation reflected beam to obtain the overall measurement height.
According to the present disclosure, a compensation optical path structure that compensates for a measurement height of a target point to improve measurement accuracy of the target point can be provided.
Drawings
The disclosure will now be explained in further detail by way of example only with reference to the accompanying drawings.
Fig. 1 is a schematic diagram illustrating an application scenario of a reconstruction apparatus according to the present disclosure.
Fig. 2 is a block diagram showing a structure of a compensation optical path according to the present disclosure.
Fig. 3 is a schematic diagram illustrating a structure of a compensation optical path according to the present disclosure.
Fig. 4 is a schematic diagram showing an internal optical path structure of an interference objective lens according to the present disclosure.
FIG. 5 is a schematic diagram illustrating a compensated interference signal and scan run according to the present disclosure.
Fig. 6 is a block diagram showing the structure of the measurement optical path according to the present disclosure.
Fig. 7 is a schematic diagram showing a measurement optical path structure according to the present disclosure.
FIG. 8 is a schematic diagram illustrating measurement interference signals and scanning strokes in accordance with the present disclosure.
Fig. 9 is a schematic diagram showing the overall optical path structure to which the present disclosure relates.
Fig. 10 is a schematic diagram illustrating synchronous reception of optical signals by the measurement optical path structure and the compensation optical path structure according to the present disclosure.
Detailed Description
Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, the same components are denoted by the same reference numerals, and redundant description thereof is omitted. The drawings are schematic, and the proportions of the dimensions of the components and the shapes of the components may be different from the actual ones.
It is noted that the terms "comprises" and "comprising," and any variations thereof, in this disclosure, such that a process, method, apparatus, article, or apparatus that comprises or has a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include or have other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
In addition, the headings and the like referred to in the following description of the present disclosure are not intended to limit the content or scope of the present disclosure, but merely serve as a reminder for reading. Such a subtitle should neither be understood as a content for segmenting an article, nor should the content under the subtitle be limited to only the scope of the subtitle.
The present disclosure relates to a compensation optical path structure for improving measurement accuracy, which may also be referred to as a compensation optical path structure in the following. In some examples, the compensation optical path structure for improving the measurement accuracy according to the present disclosure may also be referred to as a compensation optical path structure for acquiring vibration information or an optical path structure for acquiring compensation information.
According to the compensation optical path structure of the present disclosure, vibration information (which may also be compensation information) of a target point due to environmental vibration can be obtained, the compensation information can be calculated in a visual form, and an initial height of the target point can be compensated based on the compensation information to obtain a comprehensive measurement height. In addition, the reconstruction device according to the present embodiment can reconstruct the three-dimensional shape of the object based on the integrated measurement height of the target point, and thus can improve the reconstruction accuracy of the object by the reconstruction device.
Hereinafter, the compensating optical path structure according to the present embodiment will be described in detail with reference to the drawings.
Fig. 1 is a schematic diagram illustrating an application scenario of a reconstruction apparatus 10 according to the present disclosure. Fig. 2 is a block diagram illustrating a structure of the compensation optical path structure 100 according to the present disclosure. Fig. 3 is a schematic diagram illustrating a compensated optical path structure 100 according to the present disclosure.
Referring to fig. 1, a compensating optical path structure 100 according to the present disclosure may be applied to a reconstruction apparatus 10 as shown in fig. 1. In some examples, the reconstruction device 10 may be used to measure the surface height of the test object 20. In some examples, the reconstruction apparatus 10 may be an apparatus for measuring a surface height of the object 20 and reconstructing a three-dimensional topography of the object 20 based on the surface height (see fig. 3).
In some examples, the analyte 20 (described later) may be referred to as a sample. The sample can be a semiconductor, a 3C electronic glass screen, a micro-nano material, an automobile part, an MEMS device or other ultra-precise devices. In some examples, the sample may be a device for application in the fields of aerospace and the like.
In some examples, the measurement point at which the reconstruction device 10 measures the object 20 may be referred to as the target point 21. I.e. the reconstruction means 10 may be used to measure the height of the target point 21. The target point 21 may be a point, a line, or an area. In some examples, test object 20 may include at least one target point 21. Measuring one target point 21 can obtain the height of one target point 21, and measuring multiple target points 21 can obtain the height of multiple target points 21. In this case, if only the height of one target point 21 needs to be obtained, the reconstruction device 10 only needs to measure one target point 21; when the reconstruction device 10 measures a plurality of target points 21 of the object 20, the three-dimensional surface topography of the object 20 can be reconstructed based on the heights of the plurality of target points 21. In some examples, the height may be a surface height of the test object 20.
In some examples, the compensating optical path structure 100 may be used to improve the measurement accuracy when the reconstruction apparatus 10 measures the height of the target point 21. Thereby, the height data of the target point 21 can be more accurate.
In some examples, the reconstruction apparatus 10 may include a compensating optical path structure 100. In some examples, the reconstruction apparatus 10 may include a measurement optical path structure 200 (described later). The measurement optical path structure 200 may be used to acquire an initial height of the target point 21. In the measuring optical path, the initial height of the target point 21 may be acquired based on the measuring interference signal generated by the measuring beam L20.
In some examples, the reconstruction apparatus 10 may include a compensated optical path structure 100. The compensation optical path structure 100 may be used to obtain compensation information of the target point 21 due to environmental vibration. In some examples, the reconstruction device 10 may compensate the above compensation information for the initial height to obtain a comprehensive measured height of the target point 21. This can improve the measurement accuracy of the reconstruction device 10 with respect to the target point 21. In some examples, the reconstruction apparatus 10 can reconstruct the object 20 based on the combined measurement accuracy of the plurality of target points 21 to obtain a more accurate three-dimensional surface topography.
In some examples, the measuring light beam L20 may be white light. In some examples, the wavelength of the measuring light beam L20 may be 400nm-700nm, for example, may be 400nm, 450nm, 500nm, 550nm, 6000nm, 650nm, or 700 nm. In this case, the reconstruction apparatus 10 can obtain clearer image information of the surface of the object 20 when measuring the information of the object 20.
In some examples, the compensating optical path structure 100 may compensate the initial height based on a compensating interference signal generated by the compensating optical beam L10. In some examples, the compensating light beam L10 may be infrared light. The wavelength of the compensating light beam L10 may be not less than 900 nm. For example, the wavelength of the compensating light beam L10 may be 950nm, 980nm, 1000nm, or the like. In this case, the wavelength band spanned by the measuring beam L20 and the compensating beam L10 has a sufficiently long interval so that the measuring beam L20 and the compensating beam L10 can have a higher degree of isolation, and the influence of the compensating beam L10 on the measuring beam L20 during measurement can be reduced.
In some examples, the bandwidth of the compensation light beam L10 may not be greater than the first preset value. The bandwidth of the measuring beam L20 may be not less than the second preset value, and the first preset value may not be greater than the second preset value. For example, the first preset value may be 50nm, and the second preset value may be 100 nm.
Referring to fig. 2 and 3, in the present embodiment, the compensating optical path structure 100 may include a first generating module 110, a light splitting module 120, an interference objective 130, and a data processing module 140.
The first generating module 110 may be configured to generate the compensating light beam L10. The beam splitting module 120 may be used to change the propagation direction of the compensating light beam L10. Interference objective 130 may be used to form compensated reflected beam L10'. The data processing module 140 may compensate the initial height based on the compensated reflected beam L10' to obtain a composite measured height.
As described above, the first generation module 110 may be used to generate the compensation light beam L10. In some examples, the compensation light beam L10 may be a narrow-band light having a bandwidth not greater than a first preset value. Thus, the first generation module 110 may be a narrowband light source. In some examples, the compensation light beam L10 generated by the first generation module 110 may be changed in propagation direction by the light splitting module 120.
In some examples, the light splitting module 120 may include a first light splitting unit 121. The first light splitting unit 121 may be configured to receive the compensation light beam L10. The first light splitting unit 121 may be used to reflect the compensation light beam L10. In some examples, the first light splitting unit 121 may be configured to receive the compensation light beam L10 and reflect the compensation light beam L10. Thereby, the compensation light beam L10 can change the propagation direction based on the setting of the first light splitting unit 121.
In some examples, the compensating optical path structure 100 may further include a beam adjustment module 160. The beam adjustment module 160 may be used to adjust the convergence of the compensation beam L10. In some examples, the light beam adjusting module 160 may be disposed between the first generating module 110 and the first light splitting unit 121 to adjust the convergence of the compensation light beam L10.
In some examples, the beam modification module 160 may include a convergence unit 161 and a collimation unit 162. The converging unit 161 may be used to converge the compensating light beam L10 into a beam. The collimating unit 162 may be used to convert the compensation light beam L10 from diverging light to collimated light. In this case, the compensation light beam L10 can be converged into a beam after passing through the first lens unit 152 and then sent to the collimating unit 162, and the collimating unit 162 converts the converged compensation light beam L10 into collimated light and sends the collimated light to the first light splitting unit 121, so that the divergence of the compensation light beam L10 can be reduced and the energy loss of the compensation light beam L10 can be reduced.
In some examples, the compensating optical path structure 100 may not include the beam adjustment module 160.
In some examples, the compensation light beam L10 reflected by the first light splitting unit 121 may be sent to the interference objective 130. The compensation beam L10 can form a compensation reflected beam L10' at the interference objective lens 130.
In some examples, the light splitting module 120 may further include a second light splitting unit 122. The second light splitting unit 122 may be used to change the propagation direction of the compensation reflected light beam L10'.
Fig. 4 is a schematic diagram showing an internal optical path structure of the interference objective 130 according to the present disclosure.
Referring to fig. 4, in some examples, interference objective 130 may include a third light splitting unit 131 and a reference unit 132. Among them, the third light splitting unit 131 may be configured to receive the compensation light beam L10 and split the compensation light beam L10 into the first compensation light beam L11 and the second compensation light beam L12. In some examples, the third light splitting cell 131 may also be configured to reflect the first compensated light beam L11 to the reference cell 132 and transmit the second compensated light beam L12 to the target point 21.
In some examples, the first compensated target light beam L30 may be reflected to the reference cell 132 via the third light splitting cell 131 and reflected by the reference cell 132 to form a first compensated reflected light beam L10'. In some examples, the second compensation reflected light beam L12 may be transmitted to the target point 21 via the third light splitting unit 131 and reflected by the target point 21 to form a second compensation reflected light beam L10'. In some examples, the first compensating reflected light beam L10 ' and the second compensating reflected light beam L10 ' may form a compensating reflected light beam L10 '. Specifically, the third light splitting unit 131 may be further configured to combine the first compensated light beam L11 and the second compensated light beam L12 to form a compensated reflected light beam L10'. In other words, the compensated reflected light beam L10 ' may include the first compensated reflected light beam L10 ' and the second compensated reflected light beam L10 '. In this case, the compensation light beam L10 can be split into the first compensation light beam L11 and the second compensation light beam L12 after reaching the interference objective 130, wherein the first compensation light beam L11 can be reflected to the reference unit 132 via the third light splitting unit 131, and the second compensation light beam L12 can be transmitted to the target point 21 via the third light splitting unit, and since the first compensation light beam L11 and the second compensation light beam L12 reach different places, the first compensation reflected light beam L10 'and the second compensation reflected light beam L10' formed by the reflection of the first compensation light beam L11 and the second compensation light beam L12 can have optical path length differences.
FIG. 5 is a schematic diagram illustrating a compensated interference signal and scan run according to the present disclosure. Where I may be the light intensity and z may be the scan stroke.
As described above, the third light splitting unit 131 may be configured to combine the first and second compensation light beams L11 and L12 to form the compensation reflected light beam L10'. In some examples, the compensating reflected light beam L10' may include the first compensating light beam L11 and the second compensating light beam L12 having an optical path difference. Thus, the first compensation light beam L11 and the second compensation light beam L12 can interfere to generate a compensation interference signal.
In some examples, the direction of the relative displacement of the interference objective 130 and the object 20 may be referred to as a scanning direction. Referring to fig. 3, the scanning direction may be as shown in the Z direction of fig. 3. In some examples, the relative displacement of the interference objective 130 and the object 20 may be referred to as a scanning stroke when the reconstruction device 10 measures one target point 21.
In some examples, the scan stroke may be no less than the coherence length of the measuring beam L20. In some examples, the compensation light beam L10, which may have a bandwidth not greater than the first preset value, is referred to as a narrow-band light beam. The narrow-band light beam has a longer coherence length. Thus, the first compensating reflected light beam L10 ' and the second compensating reflected light beam L10 ' included in the compensating reflected light beam L10 ' can both interfere to generate a compensating interference signal over the entire scanning stroke for which one target point 21 is measured. Referring to fig. 5, in some examples, the compensation interference signal may be a sine wave signal and may be formed throughout the scan stroke.
In some examples, the vibration of the target point 21 may be monitored based on the compensation light beam L10. In other words, compensation information (vibration information) of the target point 21 due to the environmental vibration during the measurement can be obtained based on the compensation light beam L10. This enables the initial height to be compensated for by the compensation light beam L10. In some examples, compensation information of the target point 21 during the measurement may be obtained based on the compensation interference signal. The compensating interference signal may be a sine wave signal. In some examples, the compensating interference signal of the compensating optical path may be referred to as a vibration monitoring signal.
As described above, the light splitting module 120 may further include the second light splitting unit 122. The second light splitting unit 122 may be disposed in the same direction as the first light splitting unit 121. The second light splitting unit 122 may be a dichroic beam splitter. In some examples, the compensating reflected light beam L10' may reach the second light splitting unit 122 via the first light splitting unit 121 after exiting through the interference objective 130. In other words, the second light splitting unit 122 may be configured to receive the compensated reflected light beam L10' transmitted through the first light splitting unit 121. In some examples, the second receiving unit 221 may reflect the compensated reflected light beam L10' to the first receiving module 150.
In some examples, the first receiving module 150 may be configured to receive the compensation reflected light beam L10' reflected via the second light splitting unit 122 and form a compensation interference signal. Thereby, the compensation optical path structure 100 can compensate the initial height of the target point 21 based on the compensation interference signal.
In some examples, the first receiving module 150 may include a first receiving unit 151 and a first lens unit 152. Among them, the first lens unit 152 may be disposed between the first receiving unit 151 and the second light splitting unit 122. In some examples, the first receiving unit 151 may be a photodetector. Preferably, the first receiving unit 151 may be a point photodetector. Thereby, the first receiving unit 151 can convert the received compensation reflected light beam L10' into a compensation interference signal. In some examples, a point photodetector may have the advantage of high speed, large dynamic range received signals. In this case, using the point photodetector as the first receiving unit 151 enables the reconstruction apparatus 10 to quickly and accurately receive the light intensity variation information of the target point 21 in the process of measuring the target point 21. Thereby, more accurate compensation information can be obtained. In some examples, the first lens unit 152 may be a condensing lens having a function of condensing a light beam. In this case, the first lens unit 152 can focus the compensation reflected light beam L10' on the first receiving unit 151. In some examples, the first receiving module 150 may not include the first lens unit 152.
In some examples, a plurality of first receiving units 151 may be included. In some examples, the number of the first receiving units 151 may be not less than 3. For example, 3, 4, 5, etc. first receiving units 151 may be included. In some examples, when the reconstruction apparatus 10 includes a plurality of first receiving units 151, the plurality of first receiving units 151 may monitor vibration information of a plurality of target points 21, and may synthesize a vibration plane based on the plurality of vibration information. In this case, the reconstruction device 10 can implement not only the function of compensating for the initial height of the target point 21 but also the function of compensating for the angular change of the target point 21.
In some examples, the first receiving module 150 may be in signal connection with the data processing module 140. The data processing module 140 may compensate the initial height based on the compensated reflected beam L10' to obtain a composite measured height. In this case, the data processing module 140 may perform signal processing based on the compensation reflected light beam L10' to calculate compensation information of the target point 21 due to environmental vibration and compensate for the initial height. This can improve the accuracy of measuring the height of the target point 21 by the reconstruction device 10.
In particular, the data processing module 140 may be in signal connection with the first receiving module 150. And more particularly, to the first receiving unit 151. Thereby, the first receiving module 150 can transmit the compensation interference signal to the data processing module 140. The data processing module 140 may be configured to obtain compensation information based on the compensated interference signal and compensate the initial altitude based on the compensation information to obtain a composite measured altitude. In this case, the data processing module 140 can obtain compensation information of the target point 21 due to the environmental vibration based on the compensation interference information, and can reduce a measurement error due to the environmental vibration after compensating the initial height based on the compensation information, thereby improving the measurement accuracy of the reconstruction apparatus 10.
In some examples, a data acquisition unit 170 may be disposed between the data processing module 140 and the first receiving unit 151. The compensating interference signal may be sent to the data processing module 140 via the data acquisition unit 170.
In some examples, the compensation information may refer to measurement errors due to environmental vibrations, i.e., the vibration information mentioned above.
In summary, according to the compensated optical path structure 100 of the present disclosure, a measurement error of the height of the target point 21 due to environmental vibration during the measurement process can be obtained. In the present disclosure, a measurement error due to environmental vibration may become compensation information or vibration information. And the compensation optical path structure 100 according to the present disclosure can also correct (compensate) the initial height based on the compensation information to obtain the integrated measurement height of the target point 21, so as to improve the measurement accuracy of the reconstruction apparatus 10.
Fig. 6 is a block diagram showing a measurement optical path structure 200 according to the present disclosure. Fig. 7 is a schematic diagram illustrating a measurement optical path structure 200 according to the present disclosure.
As described above, the reconstruction apparatus 10 can obtain the initial height of the target point 21 based on the measurement optical path structure 200. In some examples, the measurement optical path structure 200 may include a second generation module 210, a splitting module 120, an interference objective 130, a data processing module 140, and a second receiving module 220.
The second generating module 210 may be configured to generate the measuring light beam L20 with a bandwidth not less than a second preset value. The first light splitting unit 121 may also be configured to receive the measuring light beam L20 and reflect the measuring light beam L20 to the interference objective 130, where the measuring light beam L20 forms a measuring reflected light beam L20'.
Specifically, as described above, the interference objective 130 may include the third light splitting unit 131 and the reference unit 132. Wherein, the third light splitting unit 131 may be further configured to receive the measuring light beam L20 and split the measuring light beam L20 into the first measuring light beam and the second measuring light beam. In some examples, the third light splitting unit 131 may also be configured to reflect the first measuring beam to the reference unit 132 and transmit the second measuring beam to the target point 21. In some examples, the first measurement target beam may be reflected to the reference cell 132 via the third light splitting cell 131 and reflected by the reference cell 132 to form a first measurement reflected beam. In some examples, the second measuring beam may be transmitted to the target point 21 via the third light splitting unit 131 and reflected by the target point 21 to form a second measuring reflected beam. In some examples, the first measured reflected beam and the second measured reflected beam may form a measured reflected beam L20'. Specifically, the third light splitting unit 131 may also be configured to combine the first measuring light beam and the second measuring light beam to form a measuring reflected light beam L20'. In other words, the measuring reflected light beam L20' may include a first measuring reflected light beam and a second measuring reflected light beam. In this case, the measuring beam L20 can be split into a first measuring beam and a second measuring beam after reaching the interference objective 130, wherein the first measuring beam can be reflected to the reference unit 132 via the third light splitting unit 131, the second measuring beam can be transmitted to the target point 21 via the third light splitting unit 131, and the first measuring beam and the second measuring beam formed by reflection of the first measuring beam and the second measuring beam can have an optical path difference because the first measuring beam and the second measuring beam reach different places (the specific principle can refer to fig. 4).
As described above, the measuring light beam L20 may be white light. The bandwidth of the measuring beam L20 may not be less than the second preset value. In some examples, the measuring light beam L20, which may have a bandwidth not less than the second preset value, is referred to as broadband white light.
FIG. 8 is a schematic diagram illustrating measurement interference signals and scan runs in accordance with the present disclosure.
In some examples, the first measurement reflected beam and the second measurement reflected beam may form interference. The reconstruction means 10 can thus obtain the initial height of the object point 21 on the basis of the measured interference signals of the first and second measured reflected beams. Since the coherence length of the broadband white light is short, when the optical path difference between the first measurement reflected light beam and the second measurement reflected light beam is not greater than the coherence length of the measurement light beam L20, the first measurement reflected light beam and the second measurement reflected light beam may interfere to generate interference fringes. In some examples, when the optical path difference between the first measurement reflected light beam and the second measurement reflected light beam is zero, the interference fringes thereof are most significant, the intensity of the measurement interference signal may reach a maximum value, and the reconstruction apparatus 10 may obtain the initial height of the target point 21 based on the measurement interference signal at that time. Therefore, the initial height of the target point 21 can be obtained by locating the position of zero optical path difference.
Referring to fig. 8, in some examples, the measurement interference signal collected by the measurement optical path structure 200 may be a sine wave signal modulated by a gaussian envelope. Specifically, at the zero optical path difference position, the measurement interference signal has an interference peak. The initial height of the target point 21 can be obtained based on the interference peak. When the optical path difference between the first measurement reflected light beam and the second measurement reflected light beam is greater than the coherence length of the measurement light beam L20, the first measurement reflected light beam and the second measurement reflected light beam do not interfere with each other and no measurement interference signal is generated.
In some examples, when the optical path difference between the first and second sub-measurement reflected light beams L20' is zero, the vertical distance between the reference cell 132 and the third light splitting cell 131 and the vertical distance between the third light splitting cell 131 and the target point 21 may be equal.
As described above, the scanning stroke may be not less than the coherence length of the measuring beam L20. In this case, the measurement interference signal generated by the interference of the measurement reflected light beam L20 'during the scanning process can be displayed completely, the peak value of the measurement interference signal can be accurately determined, and the compensation information can be obtained based on the compensation interference signal of the compensation reflected light beam L10' during the whole scanning process.
In some examples, the measurement optical path structure 200 may further include a second receiving module 220. The second receiving module 220 may be configured to receive the measurement reflected light beam L20' transmitted through the second light splitting unit 122. In some examples, the second receiving module 220 may include a second receiving unit 221 and a second lens unit 222. The second lens unit 222 may be a lens unit having the same function as the first lens unit 152.
In some examples, the second receiving unit 221 may be a CDD camera or a CMOS camera. Thereby, the second receiving unit 221 is able to convert the received measuring reflected light beam L20' into a measuring interference signal.
In some examples, the data processing module 140 may acquire the initial height of the target point 21 based on the measured reflected light beam L20'. Specifically, the second receiving unit 221 may be in signal connection with the data processing module 140. The data processing module 140 may obtain an initial height of the target point 21 based on the interference signal
In some examples, the measurement optical path structure 200 may also include a beam adjustment module 160, that is, may include a convergence unit 161 and a collimation unit 162. In some examples, the measurement optical path structure 200 may not include the converging unit 161 and the collimating unit 162.
In this case, in the measurement optical path structure 200, the first measurement reflected light beam and the second measurement reflected light beam can interfere to form a measurement interference signal, and the data processing unit can obtain the initial height of the target point 21 based on the generated measurement interference signal.
Fig. 9 is a schematic diagram illustrating an overall optical path structure 300 in accordance with the present disclosure.
As described above, the reconstruction apparatus 10 may include the measurement optical path structure 200 and the compensation optical path structure 100. Referring to fig. 9, in some examples, the measurement optical path structure 200 and the compensation optical path structure 100 may be combined into a total optical path structure 300. That is, the overall optical path structure 300 may include any one of the modules or units described above.
In some examples, the reconstruction apparatus 10 may further include a drive module (not shown) that may be configured to adjust the relative positions of the interference objective 130 and the target point 21. In some examples, the drive module may adjust the interference objective 130 away from or close to the target point 21. In other examples, the drive module may adjust target point 21 away from or near interference objective 130. In this case, the relative positions of the interference objective lens 130 and the target point 21 can be varied, so that the initial height of the target point 21 can be obtained based on the measurement reflected light beam L20 ', and the target point 21 is compensated based on the compensation reflected light beam L10' to obtain the integrated measurement height.
In some examples, the reconstruction device 10 may also include a carrier module. The carrying module can be used for carrying the object 20 to be tested. That is, the driving module may drive the interference objective 130 and the carrying module to change their relative positions. In some examples, the driving module may be configured to adjust the relative distance between the carrying module and the interference objective 130 so that optical path length differences of the plurality of target points 21 included in the surface of the object 20 and the reference unit 132 of the interference objective 130 are sequentially zero. In this case, the reconstruction apparatus 10 can obtain the heights of the target points 21 based on the measured interference signals of the target points 21, compensate the heights of the target points 21 based on the measured interference signals of the target points 21, and reconstruct a more accurate three-dimensional surface topography of the object 20.
In some examples, the measurement optical path structure 200 and the compensation optical path structure 100 are combined into the total optical path structure 300. The reconstruction apparatus 10 may further include a coupling unit 310, and the coupling unit 310 may be configured to receive the compensation light beam L10 and the measurement light beam L20 and to couple the compensation light beam L10 and the measurement light beam L20. At this time, the coupling unit 310 may be arranged at 45 ° to the exit direction of the compensation light beam L10. Or at 45 deg. to the exit direction of the measuring light beam L20 (see fig. 9). In this case, the compensation light beam L10 and the measuring light beam L20 can be coupled by the coupling unit 310 to be one light beam to be transmitted to the first light splitting unit 121, and thus the compensation light beam L10 and the measuring light beam L20 can be made to arrive at the interference objective lens 130 in synchronization, and the compensation reflected light beam L10 'and the measuring reflected light beam L20' are formed in synchronization, which is advantageous for obtaining compensation information more accurately matched with the initial height of the target point 21.
In some examples, the compensation light beam L10 and the measurement light beam L20 coupled by the coupling unit 310 may be taken as the target light beam L30. The first light splitting unit 121 receives the object beam L30 and reflects the object beam L30 to the interference objective lens 130. Next, the target reflected light beam L30 'is formed by the target light beam L30 at the interference objective lens 130 (specifically, refer to fig. 4 for how to form the target reflected light beam L30', which is not described herein again). Then, the target reflected light beam L30' exiting through the interference objective lens 130 may be transmitted to the second light splitting unit 122 through the first light splitting unit 121. The second light splitting unit 122 may receive the object light beam L30 'and decouple the object light beam L30' into a compensation reflected light beam L10 'matched with the compensation light beam L10 and a measurement reflected light beam L20' matched with the measurement light beam L20. The second beam splitting unit 122 then reflects the compensated reflected beam L10 'to the first receiving module 150 and transmits the measurement reflected beam L20' to the second receiving module 220. Also, the first and second receiving units 151 and 221 may receive the compensation reflected light beam L10 'and the measurement reflected light beam L20' simultaneously. Finally, the data processing module 140 obtains the initial height of the target point 21 based on the measurement reflected light beam L20 ', obtains compensation information of the target point 21 based on the compensation reflected light beam L10', and compensates the initial height to obtain a comprehensive measurement height.
Fig. 10 is a schematic diagram illustrating that the measurement optical path structure 200 and the compensation optical path structure 100 according to the present disclosure receive optical signals synchronously.
In some examples, the reconstruction apparatus may further include a timing synchronization unit 320, and the timing synchronization unit 320 may be configured to transmit a control signal to the first and second receiving modules 150 and 220 so that the first and second receiving modules 150 and 220 may synchronously receive the compensated reflected light beam L10 'and the measured reflected light beam L20'. In this case, the first receiving module 150 and the second receiving module 220 can synchronize the received optical signals, and thus, the compensation information monitored by the compensation optical path structure 100 can be synchronized with the measurement information of the measurement optical path structure 200, further improving the overall measurement accuracy of the reconstruction apparatus 10.
Specifically, the timing synchronization unit 320 may be signal-connected to the first receiving unit 151, and the timing synchronization unit 320 may be signal-connected to the second receiving unit 221. The timing synchronization unit 320 may transmit the frame synchronization pulse to the first receiving unit 151 signal and the second receiving unit 221 signal. And, the time interval of each frame may be the same. One data information (i.e., white light interference signal and compensation interference signal) of the object point 21 can be obtained per frame. In other examples, multiple data information of the target point 21 may be obtained per frame. In some examples, N frames of data may be acquired to reconstruct the three-dimensional surface topography of the test object 20. N may be an even number.
In some examples, in order to reduce the influence of the environmental vibration on the measurement accuracy, the rates at which the first receiving unit 151 and the second receiving unit 221 receive the optical signals may be increased as much as possible. As described above, the first receiving unit 151 may be a point photodetector. The second receiving unit 221 may be a CDD camera or a CMOS camera. The frame rate of the first receiving unit 151 may be 1MHZ-1 GHZ. The frame rate of the second receiving unit 221 may be 50HZ-1 KHZ. Therefore, the sampling rate of the first receiving unit 151 may be much greater than that of the second receiving unit 221. That is, the time for which the first receiving unit 151 responds to an optical signal may not be greater than the response time for which the second receiving unit 221 responds to an optical signal. Let the first receiving unit 151 receive an optical signal for a time τ 1 The second receiving unit 221 receives an optical signal for a time τ 2 In combination with the Frame synchronization pulses (Frame1, Frame2, and Frame3 … …), a time chart of the synchronous collection of the optical signals by the measurement optical path structure 200 and the compensation optical path structure 100 can be shown in fig. 10. In this case, the sampling integration time of the first receiving unit 151 may be much lower than that of the second receiving unit 221, so that the vibration information monitored by the compensation optical path structure 100 can more accurately reflect the environmental vibration.
In some examples, the same timing synchronization unit 320 is used to control the first receiving unit 151 and the second receiving unit 221 to synchronously trigger sampling, so that the interference signals of the compensation optical path structure 100 and the measurement optical path structure 100 can have synchronicity, and the vibration information monitored by the compensation optical path structure 100 can be synchronized with the initial height obtained by the measurement optical path structure 200.
Hereinafter, how to obtain compensation information based on the compensation optical path structure 100 and compensate the initial height to obtain the integrated measured height will be described in detail.
In some examples, the intensity model of the compensating interference signal formed by the compensating reflected beam L10' may be expressed as equation (1):
I(t)＝A+B cos[θ+φ(t)] (1)
where θ can be the wavefront phase, φ (t) can be a time-varying phase shift, and A and B can be the DC term coefficients and AC term coefficients, respectively. I (t) may be light intensity, and t is scan time.
If the first receiving unit 151 collects the compensation interference signals from the kth frame to the pth frame, the interference light intensities of the kth frame and the pth frame may be formula (2) and formula (3), respectively:
I k ＝A+B cos(θ) (2)
wherein, I k May compensate for the intensity, I, of the reflected beam L10' at the k-th frame p It is possible to compensate for the light intensity of the reflected light beam L10' at the p-th frame,
may be a phase increment.
In some examples, equations (2) and (3) may be further derived to obtain a wavefront phase θ of object point 21 of test object 20, which may satisfy equation (4):
in some examples, the phase shift between two frames may be incremented by
("four-step phase shift method"), the wavefront phase θ:
in some examples, the phase truth value at the target point 21 corresponding to the first receiving unit 151 can be set to θ, since the range of the tangent function is [ - π/2, + π/2]The function period is pi, the sequence of light intensities (I) collected from N frames 1 ，I 2 ，I 3 ，L I N ) The interference phase shift of adjacent frames can be calculated:
1 st to 2 nd frames: theta 1 ＝θ+δ 1
Frames 3 to 4: theta 2 ＝Mod π (θ+π+δ 2 )＝θ+δ 2
Frames 5 to 6: theta.theta. 3 ＝Mod π (θ+2π+δ 3 )＝θ+δ 3
…
Frames k-1 to k: theta k ＝Mod π (θ+2π+δ k/2 )＝θ+δ k/2
…
Frames N-1 to N: theta N/2 ＝Mod π (θ+2π+δ N/2 )＝θ+δ N/2
Wherein k is 1, 2., N/2,
δ k an additional amount of phase shift due to vibration noise between the 2k-1 to 2k frames.
In some examples, the above N/2 formulas may be added and averaged to obtain equation (6):
when the frame rate of acquisition is sufficient, the averaged vibration component may be close to zero:
therefore, the wavefront phase of the surface of the target point 21 of the object 20 corresponding to the first receiving unit 151 can be expressed by equation (7):
where N is the total number of frames collected, θ k Indicating the phase change of the target point in the adjacent frames (2 k-1 ~ 2k frames),
this enables to obtain an accurate wavefront phase.
In some examples, the error due to environmental vibrations may be calculated based on the accurate wavefront phase described above. In some examples, errors due to environmental vibrations may also be referred to as vibration disturbances.
In some examples, the amount of phase shift for vibration noise addition in each frame j may be calculated based on equation (8):
wherein, I j Is to compensate the light intensity, I, of the interference signal in the j-th frame j-1 Is the light intensity of the compensation interference signal at the j-1 th frame, a is the direct current term coefficient of the intensity model of the compensation interference signal, and θ is the wavefront phase of the second receiving unit 720 corresponding to the object point 21.
In some examples, the first frame is an initial frame and the phase change due to the vibration may be zero, i.e., δ j 0. Thereby, the phase change of the target point 21 due to the vibration in each frame can be obtained based on the formula (8).
In some examples, after arranging a plurality (≧ 3) of the first receiving units 151, different amounts of Z-translation can be detected on a plurality of target points 21 at the same time, and can be fitted to a vibration plane, which can characterize the angular swing noise of the target points 21 in addition to the translation noise of the target points 21.
In some examples, alsoThe initial height of the target point 21 may be compensated based on equation (8). In some examples, the vibration of frame j may be calculated based on the monitor signal, and the phase change caused by the vibration of frame j is δ j Correspondingly, the displacement induced in the z direction can be represented by equation (9):
wherein λ is monitor May be the center wavelength of the compensating beam L10.
Suppose that the measurement interference signal of the measurement reflected beam L20' is at the j-th frame, at a sequence z of z-position j The sample data at target point 21 is (z) j ,I j ) The actual sampling position (position of the object 20) may be z in consideration of the displacement due to the environmental vibration j +ε j Thus, the sample data can be modified to:
as can be seen from the above, the uncompensated target point 21 sample data may be a regular sequence of positions (initial heights) or a time sequence. However, by calculating the error due to the environmental vibration and compensating the error to the initial height, an irregular but accurate position sequence (integrated height measurement) or time-series sampling can be obtained.
In summary, the present disclosure can obtain the initial height of the target point 21 based on the measurement interference signal generated by the measurement reflected light beam L20'. The initial height may be compensated based on the compensation interference signal of the compensation reflected light beam L10' throughout the scan stroke. The compensated initial height may be a composite measured height. In some examples, a comprehensive measured height of multiple target points 21 may be obtained based on the compensated optical path structure 100 of the present disclosure.
In the present embodiment, the heights of the target points 21 can be obtained by obtaining the measurement interference signals of the target points 21 of the object 20 based on the above disclosure, and the heights of the target points 21 are compensated based on the measurement interference signals of the target points 21, so that the more accurate three-dimensional surface topography of the object 20 can be reconstructed.
While the present disclosure has been described in detail in connection with the drawings and examples, it should be understood that the above description is not intended to limit the disclosure in any way. Those skilled in the art can make modifications and variations to the present disclosure as needed without departing from the true spirit and scope of the disclosure, which fall within the scope of the disclosure.
Claims (10)
1. A compensating optical path structure for improving the measurement accuracy is used for improving the measurement accuracy when a reconstruction device measures the height of a target point, characterized in that the reconstruction means comprise a measurement optical path structure and the compensation optical path structure for acquiring an initial height of the target point, the compensation optical path structure comprises a first generation module, a light splitting module, an interference objective lens and a data processing module, the first generation module is used for generating a compensation light beam with the bandwidth not greater than a first preset value, the light splitting module comprises a first light splitting unit and a second light splitting unit, the first beam splitting unit is configured to receive a compensation beam and reflect the compensation beam to the interference objective lens, where the compensation beam forms a compensation reflected beam, the data processing module compensates the initial height based on the compensated reflected beam to obtain a composite measured height.
2. The compensating optical path structure of claim 1,
the first receiving module is connected with the data processing module in a signal mode and is configured to receive the compensation reflected light beam reflected by the second light splitting unit and form a compensation interference signal.
3. The compensating optical path structure of claim 2,
the first receiving module comprises a first receiving unit and a first lens unit, and the first lens unit is arranged between the first receiving unit and the second light splitting unit.
4. The compensating optical path structure according to claim 2 or 3,
the data processing module is configured to obtain compensation information based on the compensation interference signal and compensate the initial altitude based on the compensation information to obtain a synthetic measured altitude.
5. The compensating optical path structure of claim 2,
the interference objective comprises a third beam splitting unit and a reference unit,
the third light splitting unit is configured to receive the compensation light beam and split the compensation light beam into a first compensation light beam reflected to the reference unit and a second compensation light beam transmitted to the target point;
the first compensation target beam is reflected to the reference cell via the third light splitting cell and reflected by the reference cell to form a first compensation reflected beam,
the second compensation target beam is transmitted to the target point through the third light splitting unit and is reflected by the target point to form a second compensation reflected beam, and the first compensation reflected beam and the second compensation reflected beam form a compensation reflected beam.
6. The compensating optical path structure of claim 5,
the measuring optical path structure comprises a second generating module, the light splitting module, the interference objective lens, the data processing module and a second receiving module,
the second generation module is used for generating a measuring beam with the bandwidth not less than a second preset value, the first preset value is not more than the second preset value,
the first beam splitting unit is further configured to receive a measuring beam and reflect the measuring beam to the interference objective, where the measuring beam forms a measuring reflected beam,
the second receiving module is configured to receive the measurement reflected light beam transmitted through the second light splitting unit, and the data processing module acquires an initial height of the target point based on the measurement reflected light beam.
7. The compensating optical path structure of claim 6,
the reconstruction apparatus further includes a coupling unit configured to receive the compensation beam and the measurement beam and to couple the compensation beam and the measurement beam.
8. The compensating optical path structure of claim 6,
the measurement apparatus further includes a timing synchronization unit configured to send a control signal to the first receiving module and the second receiving module to cause the first receiving module and the second receiving module to synchronously receive the compensation reflected beam and the measurement reflected beam.
9. The compensating optical path structure of claim 8,
the time for the first receiving module to respond to an optical signal is not more than the response time for the second receiving module to respond to an optical signal.
10. The compensating optical path structure of claim 1,
the reconstruction apparatus further comprises a driving module configured to adjust the relative position of the interference objective and the target point.
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