Linear differential confocal displacement sensor system based on lateral encoding

Abstract

The present invention relates to a linear differential confocal displacement sensor system based on lateral encoding, and belongs to the field of sensor technology. The technical problem of low measurement efficiency of differential confocal microscope technology in the prior art is solved. The linear differential confocal displacement sensor system based on lateral encoding of the present invention converts the differential confocal microscope from point measurement to line scanning mode measurement while ensuring the measurement accuracy, and uses a blazed grating to achieve spectral lateral encoding, so that light of different wavelengths can be decomposed, and the measured element is measured through an achromatic lens in the desired order. By analyzing the light intensity signals of different wavelengths, all information on the sample height in the lateral direction can be obtained at the same time. The linear differential confocal displacement sensor system of the present invention can obtain more information in one scan, thereby reducing the overall measurement dimension. The method of reducing the measurement dimension simplifies the data acquisition process and improves the operating efficiency of the system.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a linear differential confocal displacement sensor system based on transverse encoding. Background Art

[0002] The development of differential confocal microscopy technology has made ultra-precise bipolar absolute measurement possible. This technology can achieve extremely high measurement accuracy through heterodyne interference technology. Based on this principle, researchers have developed a three-heterodyne confocal microscope, which has higher axial resolution and signal-to-noise ratio, further improving the accuracy and stability of measurement. In order to further improve the lateral resolution of differential confocal microscopy, researchers have proposed an ultra-high lateral resolution differential confocal device using a phase filter. The device optimizes the optical system by using only a phase filter, thereby significantly improving the lateral resolution capability of the confocal microscope. These technological advances have made the application prospects of differential confocal microscopy technology in the field of high-precision three-dimensional measurement broader. In future scientific research and industrial detection, differential confocal microscopy technology will play an increasingly important role. It can not only meet the needs of high-precision measurement, but also promote the development of microstructure detection technology, improve production and detection efficiency, and help scientific research and industrial manufacturing to continue to advance. Through continuous optimization and innovation, differential confocal microscopy technology is expected to demonstrate its powerful performance and advantages in more application scenarios.

[0003] However, traditional differential confocal microscopes usually use point measurement to scan in multiple dimensions to obtain complete three-dimensional information of the sample. Therefore, traditional differential confocal microscopes still face the same problem as existing point detection non-contact probes, namely, low measurement efficiency. Summary of the invention

[0004] The present invention aims to solve the technical problem of low measurement efficiency of differential confocal microscopy technology in the prior art, and provides a linear differential confocal displacement sensor system based on lateral encoding. The linear differential confocal displacement sensor system of the present invention can obtain more information in one scan, thereby reducing the overall measurement dimension. The method of reducing the measurement dimension simplifies the data acquisition process and improves the operating efficiency of the system.

[0005] In order to solve the above technical problems, the technical solutions of the present invention are as follows:

[0006] A linear differential confocal displacement sensor system based on transverse encoding, comprising in sequence in the direction of the optical path: a light source, a first collimating lens, a first beam splitter, a first blazed grating, a telecentric aperture, a first achromatic lens and a piezoelectric ceramic driver; wherein the first beam splitter is also connected in sequence to: a second beam splitter, a first focusing lens, a first pinhole and a first imaging spectrometer; the second beam splitter is also connected in sequence to: a second focusing lens, a second pinhole and a second imaging spectrometer; the positions of the first pinhole and the second pinhole are symmetrical in the front-to-back direction of the focal length of the first focusing lens and the second focusing lens;

[0007] The light beam output by the light source forms a collimated light beam through the first collimating lens. The collimated light beam passes through the first beam splitter and the first blazed grating to separate light beams of different wavelengths, thereby obtaining a spectrally transversely coded illumination light beam. The spectrally transversely coded illumination light beam passes through a telecentric aperture to eliminate the magnification change so that it is parallel to the optical axis when entering the first achromatic lens. After the light beam is focused by the first achromatic lens, it is imaged in a linear manner onto the surface of the measured component placed on the piezoelectric ceramic driver. After the reflected return light beam is split by the first beam splitter and the second beam splitter, it enters the first focusing lens and the second focusing lens of the same focal length respectively. After the focused light beam passes through the first pinhole and the second pinhole respectively, the obtained spectral information data is received by the first imaging spectrometer and the second imaging spectrometer respectively.

[0008] In the above technical solution, the axial light intensity response signals received by the first imaging spectrometer and the second imaging spectrometer are and , and the differential confocal response signal is obtained by differential subtraction. , the differential confocal response signal The height information of one wavelength of the measured component is obtained. After the height information of all wavelengths is calculated, all the height information of one lateral dimension of the measured component is obtained. Then, the axial distance and another lateral dimension of the measured component are controlled by the piezoelectric ceramic driver to complete the measurement, thereby completing the three-dimensional reconstruction of the measured component.

[0009] In the above technical solution, the first imaging spectrometer and the second imaging spectrometer respectively include: a second collimating lens, a second blazed grating, a second achromatic lens and a CCD camera in sequence in the direction of the optical path; the second collimating lens is used to collimate the light source into a parallel light beam; the second blazed grating is used to separate light of different wavelengths to achieve lateral encoding; the second achromatic lens is used to focus light beams of different wavelengths at the same position; and the CCD camera is used to receive spectral information.

[0010] In the above technical solution, the light source is continuous white light with a wide wavelength band.

[0011] In the above technical solution, for a single point and a single wavelength in the horizontal direction, it is necessary to calculate the differential confocal response signal of the single point, and the process is as follows:

[0012] When the distance of the measured element surface away from the focus of the first achromatic lens is When , the light field of the point light source is , after passing through the first collimating lens and the first achromatic lens, the light field distribution for:

[0013] ;

[0014] Among them, the out-of-focus spread function for:

[0015] ;

[0016] The reflected light field reflected from the surface of the measured element forms a light field near its focus after passing through the first achromatic lens and the focusing lens. Again, we can use the Huygens-Fresnel diffraction integral formula to get:

[0017] ;

[0018] Among them, the out-of-focus spread function for:

[0019] ;

[0020] The incident light wave number is , is the wavelength of light, is the focal length of the first collimating lens, is the focal length of the first achromatic lens, is the focal length of the focusing lens, , and are the pupil functions of the first collimating lens, the first achromatic lens and the focusing lens, respectively, is the defocus amount, is a pure imaginary number, , All represent integral differentials;

[0021] Assuming pupil function , and is an axisymmetric function, let , , , through the coordinate conversion formula and Hankel transformation, and ignore the small terms, and at the same time change the variable , , , Normalize it and get the light field in polar coordinates Transformed light field for:

[0022] ;

[0023] in, , is a variable The normalized coordinates of , is a variable The normalized coordinates of , is a variable The normalized coordinates of , is a variable The normalized coordinates of , is the normalized radial radius of the pupil; is a variable The polar angle of is a Bessel function of order 0; , , They are respectively , , After transformation, let , the pupil function obtained;

[0024] When only the intensity response of the imaging spectrometer along the optical axis is considered, let , ignoring the influence of aberration, that is , , , the formula is simplified to:

[0025] ;

[0026] The post-focus response signals obtained by the first imaging detector and the second imaging detector are respectively Pre-focus response signal Differential subtraction to obtain coordinate normalized differential confocal response signal for:

[0027] .

[0028] The beneficial effects of the present invention are:

[0029] The linear differential confocal displacement sensor system based on lateral encoding of the present invention converts the point measurement of the differential confocal microscope into line scanning mode measurement while ensuring the measurement accuracy, and uses a blazed grating to realize spectral lateral encoding, so that light of different wavelengths can be decomposed, and the measured element is measured through an achromatic lens in a desired order. By analyzing the light intensity signals of different wavelengths, all information on the sample height in the lateral direction can be obtained simultaneously.

[0030] The linear differential confocal displacement sensor system based on lateral coding of the present invention can receive a differential confocal response signal for each wavelength on the imaging spectrometer. The zero-crossing position of the differential confocal response signal accurately corresponds to the position where the surface of the measured element coincides with the focusing point O of the measuring light beam, which is the height information of the measured element. After the height information of all wavelengths is calculated, all the height information of the measured element in one lateral dimension is obtained; then, the axial distance of the measured element and the other lateral dimension are controlled by the piezoelectric ceramic driver (PZT) to complete the measurement, and the three-dimensional reconstruction of the measured element can be completed. The linear differential confocal displacement sensor system of the present invention is a lateral coding performed on a differential confocal microscope system. After the lateral coding, only two dimensions need to be scanned. When scanning, the traditional differential confocal microscope needs to scan in three dimensions to obtain all the information of the object and perform three-dimensional reconstruction.

[0031] The linear differential confocal displacement sensor system based on lateral encoding of the present invention can encode one of the measurement dimensions into the lateral direction by introducing a dispersion method of lateral encoding. This encoding method can obtain more information in one scan, thereby reducing the overall measurement dimension. The method of reducing the measurement dimension simplifies the data acquisition process and improves the operating efficiency of the system. The system greatly reduces the number of scans required when scanning samples, thereby significantly shortening the measurement time. For a large number of samples that need to be analyzed quickly or time-sensitive experiments, shortened measurement time means higher experimental efficiency. In addition, this advantage is particularly prominent in high-throughput measurement applications, which can greatly improve sample processing speed and laboratory productivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0033] Figure 1 It is a schematic structural diagram of the linear differential confocal displacement sensor system based on lateral encoding of the present invention.

[0034] Figure 2 The internal structure of the imaging spectrometer.

[0035] Figure 3 For imaging spectrometer Signal strength graph.

[0036] Figure 4 For imaging spectrometer Signal strength graph.

[0037] The reference numerals in the figures indicate:

[0038] 1-light source, 2-first collimating lens, 3-first beam splitter, 4-first blazed grating, 5-telecentric aperture, 6-first achromatic lens, 7-measured element, 8-piezoelectric ceramic actuator (PZT), 9-second beam splitter, 10-first focusing lens, 11-first pinhole, 12-first imaging spectrometer, 13-second focusing lens, 14-second pinhole, 15-second imaging spectrometer.

[0039] 121 - a second collimating lens, 122 - a second blazed grating, 123 - a second achromatic lens, 124 - a CCD camera. DETAILED DESCRIPTION

[0040] The inventive concept of the present invention is as follows: the differential confocal microscope in the prior art still faces the common problem of point detection non-contact probes, namely, low measurement speed. In the actual measurement process, detection efficiency is very important. As time goes by, the measurement results may change due to various factors. Environmental factors such as temperature, humidity and light may change, affecting the accuracy of the measurement results. The absolute position of the object being measured may move over time, causing measurement errors, and the degree of error impact is directly related to the measurement accuracy. At the same time, the measurement tool may drift and need to be recalibrated to ensure accuracy.

[0041] For large-surface measurement requirements, many R&D personnel hope to use multiple detectors to work simultaneously to achieve the measurement effect of line scanning. However, this method is very costly and does not meet the actual engineering requirements. In order to greatly improve the measurement efficiency of differential confocal microscopy technology, the present invention proposes a linear differential confocal displacement sensor system based on lateral encoding. Traditional differential confocal microscopes usually need to scan in multiple dimensions to obtain complete three-dimensional information of the sample. The present invention can encode one of the measurement dimensions into the lateral direction by introducing a dispersion method of lateral encoding. This encoding method can obtain more information in one scan, thereby reducing the overall measurement dimension. The method of reducing the measurement dimension simplifies the data acquisition process and improves the operating efficiency of the system. The number of scans required by the system when scanning the sample is greatly reduced, thereby significantly shortening the measurement time. For a large number of samples that need to be analyzed quickly or time-sensitive experiments, the shortened measurement time means higher experimental efficiency. In addition, this advantage is particularly prominent in high-throughput measurement applications, which can greatly improve sample processing speed and laboratory productivity.

[0042] The linear differential confocal displacement sensor system based on lateral coding of the present invention is a lateral coding performed on a differential confocal microscope system. When a traditional differential confocal microscope is scanned, it is necessary to scan in three dimensions in order to obtain all the information of the object and perform three-dimensional reconstruction. After lateral coding, the present invention only needs to scan two dimensions. Lateral coding is to separate white light into lights of different wavelengths through dispersion and lenses, and focus it laterally on the measured element. By analyzing the light intensity signals of different wavelengths, all the lateral information of the height of the measured element can be obtained at the same time, that is, all the height information of the measured element in one lateral dimension can be obtained. Then, through the piezoelectric ceramic driver (PZT), the axial distance of the measured element and the other lateral dimension are controlled to complete the measurement, and the three-dimensional reconstruction of the measured element can be completed.

[0043] The linear differential confocal displacement sensor system based on transverse encoding of the present invention has a main structure that a wide-band continuous white light source forms a collimated beam through a collimator, and the collimated beam passes through a beam splitter and a blazed grating to achieve wavelength separation, that is, spectral transverse encoding, and then the obtained spectrally coded illumination beam is focused by an achromatic lens and imaged in a linear manner onto the surface of an object (measured element) placed on a piezoelectric ceramic driver (PZT). The grating pitch and blazed angle of the blazed grating can control the emission angle of light of a specific wavelength, so that the linear coding on the focal plane of the achromatic lens can be stably arranged at the expected value designed or calibrated. After reflection, the return beam passes through a beam splitter and enters focusing lenses of the same focal length respectively, and a pinhole is placed behind each of the two focusing lenses. The positions of the two pinholes are symmetrical in the front and rear directions of the focal length of the focusing lens, and a spectrometer is placed behind the pinhole for data reception.

[0044] The present invention is described in detail below with reference to the accompanying drawings.

[0045] Combination Figure 1 The linear differential confocal displacement sensor system based on transverse encoding of the present invention is specifically described, which includes in the direction of the optical path: a light source 1, a first collimating lens 2, a first beam splitter 3, a first blazed grating 4, a telecentric aperture 5, a first achromatic lens 6 and a piezoelectric ceramic driver 8; wherein the first beam splitter 3 is also connected in sequence to: a second beam splitter 9, a first focusing lens 10, a first pinhole 11 and a first imaging spectrometer 12; the second beam splitter 9 is also connected in sequence to: a second focusing lens 13, a second pinhole 14 and a second imaging spectrometer 15; the light source 1 is a wide-band continuous white light;

[0046] The light source 1 is used to output a stable wide-band white light source; the first collimating lens 2 is used to collimate the light source into a parallel light beam; the first blazed grating 4 is used to separate light of different wavelengths to achieve lateral encoding; the telecentric aperture 5 is used to eliminate the magnification change so that the light is parallel to the optical axis when entering the first achromatic lens 6; the first achromatic lens 6 is used to focus light of different wavelengths at the same position; the piezoelectric ceramic driver 8 is used to control the measured element 7 to achieve lateral movement and axial movement; the beam splitter (the first beam splitter 3 and the second beam splitter 9) is used for light splitting; the focusing lens (the first focusing lens 10 and the second focusing lens 13) is used to focus the parallel light beam; the pinhole (the first pinhole 11 and the second pinhole 14) is used to suppress defocused light and reduce the interference of scattered light; the imaging spectrometer (the first imaging spectrometer 12 and the second imaging spectrometer 15) is used to image and analyze the spectrum, Figure 2 This is a diagram of the internal structure of an imaging spectrometer, which includes in the direction of the optical path: a second collimating lens 121, a second blazed grating 122, a second achromatic lens 123 and a CCD camera 124; the second collimating lens 121 is used to collimate the light source into a parallel light beam; the second blazed grating 122 is used to separate light of different wavelengths to achieve lateral encoding; the second achromatic lens 123 is used to focus light beams of different wavelengths on the same position; the CCD camera 124 is used to receive spectral information.

[0047] The wide-band continuous white light beam output by the light source 1 is formed into a collimated light beam through the first collimating lens 2. After the collimated light beam passes through the first beam splitter 3 and the first blazed grating 4, the separation of light beams of different wavelengths is realized, that is, spectral transverse encoding. The obtained spectral transverse encoding illumination light beam passes through the telecentric aperture 5 to eliminate the magnification change so that it is parallel to the optical axis when entering the first achromatic lens 6. After the light beam is focused by the first achromatic lens 6, it is imaged in a linear manner onto the surface of the measured element 7 placed on the piezoelectric ceramic driver 8. The grating pitch and blazed angle of the first blazed grating 4 can be controlled. The emission angle of the light of a specific wavelength enables the linear code on the focal plane of the first achromatic lens 6 to be stably arranged at the expected value designed or calibrated; the return light beam reflected by the surface of the measured element 7 is split by the first beam splitter 3 and the second beam splitter 9, and then enters the first focusing lens 10 and the second focusing lens 13 with the same focal length respectively, and the first pinhole 11 and the second pinhole 14 are respectively placed behind the two focusing lenses, and the positions of the two pinholes are symmetrical in the front and rear directions of the focal length of the focusing lens, and the first imaging spectrometer 12 and the second imaging spectrometer 15 are placed behind the two pinholes to receive spectral information data;

[0048] The axial light intensity response signals received by the first imaging spectrometer 12 and the second imaging spectrometer 15 are and , and the differential confocal response signal is obtained by differential subtraction. , the differential confocal response signal The height information of one wavelength of the measured element 7 is calculated. After the height information of all wavelengths is calculated, all the height information of one lateral dimension of the measured element 7 is obtained. Then, the axial distance and another lateral dimension of the measured element 7 are controlled by the piezoelectric ceramic driver 8 to complete the measurement, thereby completing the three-dimensional reconstruction of the measured element 7.

[0049] The linear differential confocal displacement sensor system based on transverse coding of the present invention is a transverse coding performed on a differential confocal microscopy system. After transverse coding, only two dimensions need to be scanned. Transverse coding is to separate white light into different wavelengths of light through dispersion and lenses, and to focus it transversely on the measured element 7. By analyzing the light intensity signals of different wavelengths, all information on the height transverse direction of the measured element 7 can be obtained simultaneously.

[0050] For a single point and a single wavelength in the horizontal direction, it is still the measurement principle of differential confocal microscopy. It is necessary to calculate the differential confocal response signal formula of a single point.

[0051] The light beam is focused near the surface position of the measured element 7. When the measured element 7 is scanned near the position, two imaging spectrometers symmetrically located one in front of the other behind the focus of the focusing lens respectively receive the axial light intensity response signal reflected from the surface of the measured element 7. and , and the differential confocal response signal is obtained by differential subtraction. .

[0052] When the distance of the surface of the measured element 7 away from the focus of the first achromatic lens 6 is When , the light field of the point light source is After passing through the first collimating lens 2 and the first achromatic lens 6, the light field distribution is for:

[0053] ;

[0054] Among them, the out-of-focus spread function for:

[0055] ;

[0056] The reflected light field reflected from the surface of the measured element 7 passes through the first achromatic lens 6 and the focusing lens to form a light field near its focus. Again, we can use the Huygens-Fresnel diffraction integral formula to get:

[0057] ;

[0058] Among them, the out-of-focus spread function for:

[0059] ;

[0060] The incident light wave number is , is the wavelength of light, is the focal length of the first collimating lens 2, is the focal length of the first achromatic lens 6, is the focal length of the focusing lens, , and are the pupil functions of the first collimating lens 2, the first achromatic lens 6 and the focusing lens, respectively, is the defocus amount, is a pure imaginary number, , All represent integral differentials;

[0061] Assuming pupil function , and is an axisymmetric function, let , , , through the coordinate conversion formula and Hankel transformation, and ignore the small terms, and at the same time change the variable , , , Normalize it and get the light field in polar coordinates Transformed light field for:

[0062] ;

[0063] in, ,yes The normalized coordinates of , is a variable The normalized coordinates of , is a variable The normalized coordinates of is a variable The normalized coordinates of , is the normalized radial radius of the pupil; is a variable The polar angle of is a Bessel function of order 0; , , They are respectively , , After transformation, let , the pupil function obtained; when only considering the intensity response of the imaging spectrometer along the optical axis, let , ignoring the influence of aberration, that is , , , the formula is simplified to:

[0064] ;

[0065] The post-focus response signals obtained by the first imaging spectrometer 12 and the second imaging spectrometer 15 are respectively Pre-focus response signal Differential subtraction to obtain coordinate normalized differential confocal response signal for:

[0066] .

[0067] Response signal Intensity and response signal Strength Figure 3 and 4 .

[0068] On the imaging spectrometer, each wavelength can receive a differential confocal response signal. The zero-crossing position of the differential confocal response signal accurately corresponds to the position where the surface of the measured element 7 coincides with the focusing point O of the measuring light beam, which is the height information of the measured element 7. After the height information of all wavelengths is calculated, all the height information of the measured element 7 in one lateral dimension is obtained.

[0069] Then, the piezoelectric ceramic driver 8 is used to control the axial distance of the measured element 7 and another lateral dimension to complete the measurement, thereby completing the three-dimensional reconstruction of the measured element 7.

[0070] In summary, the linear differential confocal displacement sensor system based on lateral encoding of the present invention can encode one of the measurement dimensions into the lateral direction by introducing a dispersion method of lateral encoding. This encoding method can obtain more information in one scan, thereby reducing the overall measurement dimension. The method of reducing the measurement dimension simplifies the data acquisition process and improves the operating efficiency of the system. The number of scans required by the system when scanning samples is greatly reduced, thereby significantly shortening the measurement time. For a large number of samples that need to be analyzed quickly or time-sensitive experiments, shortening the measurement time means higher experimental efficiency. In addition, this advantage is particularly prominent in high-throughput measurement applications, which can greatly improve the sample (i.e., the measured element) processing speed and laboratory productivity. The simulation results show that the system of the present invention is practical and effective.

[0071] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A linear differential confocal displacement sensor system based on lateral encoding, characterized in that: In the direction of the optical path, the optical system comprises: a light source (1), a first collimating lens (2), a first beam splitter (3), a first blazed grating (4), a telecentric aperture (5), a first achromatic lens (6) and a piezoelectric ceramic driver (8); wherein the first beam splitter (3) is also connected in sequence to: a second beam splitter (9), a first focusing lens (10), a first pinhole (11) and a first imaging spectrometer (12); the second beam splitter (9) is also connected in sequence to: a second focusing lens (13), a second pinhole (14) and a second imaging spectrometer (15); the positions of the first pinhole (11) and the second pinhole (14) are symmetrical in the front-rear direction of the focal length of the first focusing lens (10) and the second focusing lens (13); The light beam output by the light source (1) passes through the first collimating lens (2) to form a collimated light beam. The collimated light beam passes through the first beam splitter (3) and the first blazed grating (4) to separate light beams of different wavelengths, thereby obtaining a spectrally transversely coded illumination light beam. The spectrally transversely coded illumination light beam passes through the telecentric aperture (5) to eliminate the magnification change so that it is parallel to the optical axis when entering the first achromatic lens (6). After the light beam is focused by the first achromatic lens (6), it is imaged in a linear manner onto the surface of the measured element (7) placed on the piezoelectric ceramic driver (8). After the reflected return light beam is split by the first beam splitter (3) and the second beam splitter (9), it enters a first focusing lens (10) and a second focusing lens (13) of the same focal length respectively. After the focused light beam passes through the first pinhole (11) and the second pinhole (14), the obtained spectral information data is received by the first imaging spectrometer (12) and the second imaging spectrometer (15).

2. The linear differential confocal displacement sensor system according to claim 1, characterized in that: Axial light intensity response signals received respectively by the first imaging spectrometer (12) and the second imaging spectrometer (15) and , and the differential confocal response signal is obtained by differential subtraction. , the differential confocal response signal The height information of one wavelength of the measured element (7) is obtained. After the height information of all wavelengths is calculated, all the height information of one lateral dimension of the measured element (7) is obtained. Then, the axial distance of the measured element (7) and another lateral dimension are controlled by the piezoelectric ceramic driver (8) to complete the measurement, thereby completing the three-dimensional reconstruction of the measured element (7).

3. The linear differential confocal displacement sensor system according to claim 1, characterized in that: The first imaging spectrometer (12) and the second imaging spectrometer (15) respectively comprise, in order in the direction of the optical path: a second collimating lens (121), a second blazed grating (122), a second achromatic lens (123) and a CCD camera (124); the second collimating lens (121) is used to collimate the light source into a parallel light beam; the second blazed grating (122) is used to separate light of different wavelengths to achieve transverse encoding; the second achromatic lens (123) is used to focus light beams of different wavelengths at the same position; and the CCD camera (124) is used to receive spectral information.

4. The linear differential confocal displacement sensor system according to claim 1, characterized in that: The light source (1) is continuous white light with a wide wavelength band.

5. The linear differential confocal displacement sensor system according to claim 2, characterized in that: For a single point and a single wavelength in the horizontal direction, the differential confocal response signal of the single point needs to be calculated. The process is as follows: When the distance of the surface of the measured element (7) deviating from the focus of the first achromatic lens (6) is When , the light field of the point light source is After passing through the first collimating lens (2) and the first achromatic lens (6), the light field distribution is for: ； Among them, the out-of-focus spread function for: ； The reflected light field reflected from the surface of the measured element (7) passes through the first achromatic lens (6) and the focusing lens to form a light field near its focus. Again, we can use the Huygens-Fresnel diffraction integral formula to get: ； Among them, the out-of-focus spread function for: ； The incident light wave number is , is the wavelength of light, is the focal length of the first collimating lens (2), is the focal length of the first achromatic lens (6), is the focal length of the focusing lens, , and are the pupil functions of the first collimating lens (2), the first achromatic lens (6) and the focusing lens, respectively, is the defocus amount, is a pure imaginary number, , All represent integral differentials; Assuming pupil function , and is an axisymmetric function, let , , , through the coordinate conversion formula and Hankel transformation, and ignore the small terms, and at the same time change the variable , , , Normalize it to get the light field in polar coordinates Transformed light field for: ； in, , is a variable The normalized coordinates of , is a variable The normalized coordinates of , is a variable The normalized coordinates of , is a variable The normalized coordinates of , is the normalized radial radius of the pupil; is a variable The polar angle of is a Bessel function of order 0; , , They are respectively , , After transformation, let , the pupil function obtained; When only the intensity response of the imaging spectrometer along the optical axis is considered, let , ignoring the influence of aberration, that is , , , the formula is simplified to: ； The post-focus response signals respectively obtained by the first imaging detector (12) and the second imaging detector (15) are Pre-focus response signal Differential subtraction to obtain coordinate normalized differential confocal response signal for: 。

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