Optical manufacturing adjustment auxiliary zero calibration measurement system and method based on CGH

Abstract

The invention is suitable for the technical field of measurement, and provides a CGH-based optical manufacturing adjustment auxiliary zero calibration measurement system and method, and the system comprises an interference measurement module, an improved PSF measurement module, a semi-transparent and semi-reflective mirror, and a CGH, the CGH is used for carrying out phase modulation on the interference measurement module and the improved PSF measurement module, and the improved PSF measurement module is used for carrying out phase modulation on the interference measurement module and the improved PSF measurement module. The CGH includes an improved PSF measurement phase portion, a tilt angle measurement phase portion, and a positioning holographic phase portion. According to the method, accurate calibration of the relative position of the optical-mechanical element of the system is realized by utilizing the divisible characteristic of the computer generated hologram (CGH), and inherent errors generated in the assembling process of a processing or measuring system are effectively reduced. The system has the advantages of structural modularization, real-time response, high-precision measurement and the like, and is particularly suitable for high-precision measurement of the attitude of the optical element, so that the precision and stability of a high-end equipment processing platform and in the optical manufacturing and adjusting process are remarkably improved.

Description

Technical Field

[0001] The invention belongs to the field of measurement technology, and in particular relates to a CGH-based optical manufacturing assembly auxiliary zero-position calibration measurement system and method. Background Art

[0002] With the continuous improvement of photoelectric detection accuracy, the demand for three-dimensional real-time high-precision measurement methods for high-end equipment processing platforms has become more urgent, aiming to ensure the accuracy of the real-time measurement results of the photoelectric detection system and the validity of the data. Therefore, it is necessary to design a multi-dimensional (yaw angle, pitch angle and axial / lateral displacement) measurement system that can simultaneously achieve high-precision tilt angle measurement and displacement measurement, and can record status data in real time to provide a basis for subsequent analysis.

[0003] Optomechanical systems are usually composed of multiple optomechanical components. The tilt and jitter of the processing platform of high-end equipment will cause slight changes in the relative position of the optomechanical components, which will lead to a decrease in measurement and processing accuracy. Therefore, the precise position measurement and calibration of optomechanical components have become a key technology in the process of optomechanical processing, manufacturing and assembly. Slight deviations in the position and posture of optomechanical components may lead to a significant decrease in system performance, or even fail to achieve the expected optical effect. Existing measurement methods have problems such as low accuracy, poor real-time performance, and complex error correction, especially in high-precision processing, manufacturing and assembly. Accurate measurement and real-time error compensation have become a major problem. Interferometric measurement methods have the characteristics of high precision, non-contact, and non-destructive. At the same time, computer-generated hologram technology (CGH) has developed rapidly in recent years and has been gradually applied in high-precision optical wavefront modulation. In view of the above problems, the present invention proposes an optical manufacturing and assembly auxiliary zero-position calibration measurement system and method based on CGH. Summary of the invention

[0004] The purpose of the present invention is to provide an optical manufacturing assembly auxiliary zero-position calibration measurement system and method based on CGH, aiming to solve the problems raised in the above background technology.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] The CGH-based optical manufacturing and adjustment auxiliary zero-position calibration measurement system includes:

[0007] An interferometric measurement module is used for rough measurement of pitch angle, yaw angle and axial displacement, and has an interferometric optical path; the interferometric measurement module includes a standard spherical interferometer and a reference mirror;

[0008] The improved PSF measurement module is used for high-precision measurement of axial displacement and measurement of large lateral eccentric displacement, and is an optical 4f system; the improved PSF measurement module comprises a laser reference point, a sensor and two objective lenses, the laser reference point is installed in the central area of ​​the reference mirror support structure, and the two objective lenses include objective lens 1 and objective lens 2;

[0009] A semi-transparent and semi-reflective mirror is used to separate the measurement light of the improved PSF measurement module and the interference measurement module. One part of the measurement light in the interference measurement module enters the standard spherical interferometer, and the other part enters the sensor plane.

[0010] CGH, installed in the Fourier plane of the 4f system, is used to phase modulate the interferometric measurement module and the improved PSF measurement module, including:

[0011] Improve the PSF measurement phase part, including the central area, for phase modulation, and achieve axial / lateral displacement measurement by changing the PSF shape on the sensor;

[0012] The inclination measurement phase part includes an annular region, which is used to modulate the standard spherical wavefront phase to make it consistent with the reference mirror type, thereby realizing dual-axis inclination measurement;

[0013] The positioning holographic phase part includes a wavefront modulated annular reflection area for positioning the CGH and a wavefront modulated point transmission area for positioning the reference mirror.

[0014] Furthermore, the central region modulates the standard PSF that diffuses as the defocus amount increases into two main lobes that continuously rotate as the system defocus amount changes by modulating the phase.

[0015] Furthermore, the phase of the central area is obtained by the Fresnel zone method, and the phase is related to the total number of Fresnel zones L and the radius R1 of the phase plate, and the spacing between the two main lobes and the axial range corresponding to their rotation of 180° are changed only by modifying the total number of Fresnel zones L; the optical path transmission of the 4f system is derived according to the Fresnel diffraction principle, and the sensitivity of the PSF rotation angle θ to the axial displacement Δz of the object is obtained;

[0016] When L remains unchanged, that is, the phase of the central area remains unchanged, the numerical aperture NA of the 4f system is adjusted to adjust the size of the measurement range, and high-precision measurement is performed in a small axial displacement range; NA = R1 / f1, f1 is the focal length of the objective lens of the 4f system, and NA is adjusted by adjusting f1.

[0017] Furthermore, after the laser emitted by the laser reference point is collimated by objective lens 2, it is phase modulated by the central area in the Fourier plane of the 4f system, and converges through objective lens 1 of the optical path of the 4f system to reach the sensor. The PSF no longer diffuses with the increase of the defocus amount, and the two main lobes rotate continuously with the position of the laser reference point, and the rotation angle changes with the axial displacement of the laser reference point. The imaging position of the PSF on the sensor plane changes with the lateral displacement of the laser reference point.

[0018] Furthermore, the wavelength of light waves used by the standard spherical interferometer is 632.8 nm.

[0019] Furthermore, the wavelength of the laser reference point is 520 nm.

[0020] The CGH-based optical manufacturing assembly auxiliary zero-position calibration measurement method is applied to the system as described above, and the measurement method includes the following steps:

[0021] The calibration phase includes:

[0022] Step S11: Utilize the reflection area to locate and calculate the relative position of the CGH. When the interference pattern contrast of the standard spherical interferometer is zero, the position of the CGH can be accurately located and calculated.

[0023] Step S12: Using the transmission area to locate the reference mirror, after the incident light is modulated, its third-order diffraction light projects two vertical line segments at the specified position of the edge of the reference mirror to form a cross line as a positioning reference, and one cross line is projected in each of the positive and negative directions of X and Y, forming a total of eight cross lines; at the same time, fine-tune the measuring reflector so that the first to sixth terms of the Zernike coefficient are less than 0.01, so that the position of the reference mirror can be accurately located;

[0024] Step S13: accurately locate the CGH position according to step S11, that is, locate the position of the Fourier surface of the 4f system; accurately locate the reference mirror position according to step S12, that is, locate the reference position of the laser point; further locate the position of the objective lens and the sensor, and when the rotation angle of the two main lobe spots displayed on the sensor plane is 0°, the displacement measurement calibration is completed;

[0025] The measurement phase includes:

[0026] Step S21: using an interferometric measurement module to perform a rough measurement of the pitch angle, yaw angle, and axial displacement;

[0027] Step S22: According to the rough axial displacement, the focal length of the objective lens in the PSF measurement module is adjusted to narrow the measurement range to near the displacement value, and the axial displacement is further measured with high precision; according to the pitch angle and yaw angle, the lateral displacement is further measured with high precision; and finally multi-dimensional measurement is achieved.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention utilizes the partitionable characteristics of computer-generated holograms (CGH) to achieve accurate calibration of the relative positions of the system's optical and mechanical components, effectively reducing the inherent errors generated during the assembly of the processing or measurement system. The present invention exhibits advantages such as structural modularity, real-time response, and high-precision measurement, and is particularly suitable for high-precision measurement of the posture (including yaw angle, pitch angle, and axial displacement) of optical components, thereby significantly improving the accuracy and stability of high-end equipment processing platforms and optical manufacturing and adjustment processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural diagram of the system in the present invention.

[0031] Figure 2 Schematic diagram of the structure of CGH in the system of the present invention.

[0032] Figure 3 It is a schematic diagram of the present invention.

[0033] In the figure: 1-standard spherical interferometer; 2-semi-transparent and semi-reflective mirror; 3-objective lens 1; 4-CGH; 5-objective lens 2; 6-reference mirror; 7-sensor; 8-central area; 9-annular area; 10-reflection area; 11-transmission area. DETAILED DESCRIPTION

[0034] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0035] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0036] An embodiment of the present invention provides an optical manufacturing assembly auxiliary zero-position calibration measurement system based on CGH, which integrates an interferometric measurement module, an improved point spread function (PSF) measurement module, a semi-transparent and semi-reflective mirror 2 and CGH 4. In conjunction with the semi-transparent and semi-reflective mirror 2 and CGH 4, the interferometric measurement module is used to perform rough measurements of pitch angles, yaw angles and axial displacements, and the improved PSF measurement module is used to perform high-precision measurements of axial displacements and measurements of larger lateral eccentric displacements, thereby achieving three-dimensional measurement.

[0037] The interference measurement module has only one interference optical path, including a standard spherical interferometer 1 (wavelength 632.8 nm) and a reference mirror 6.

[0038] The improved PSF (point spread function) measurement module is an optical 4f system, including a laser reference point, a sensor 7 and two objective lenses; the laser reference point is installed in the central area of ​​the reference mirror 6 support structure, and the laser wavelength is 520nm; the two objective lenses include objective lens 1 3 and objective lens 2 5.

[0039] The semi-transparent and semi-reflective mirror 2 is used to separate the measurement light of the improved PSF measurement module and the interference measurement module. The 632.8nm measurement light in the interference measurement module enters the standard spherical interferometer 1 behind the semi-transparent and semi-reflective mirror 2, while the other part of the measurement light will be reflected by the metal film and enter the sensor 7 plane in the improved PSF measurement module.

[0040] CGH 4, installed in the Fourier plane of the 4f system, is used for phase modulation of the interferometric measurement module and the improved PSF measurement module, including:

[0041] The improved PSF measurement phase part includes a central area 8, which is used to modulate the phase to change the PSF shape on the sensor 7 and realize axial / lateral displacement measurement. By modulating the phase, the standard PSF that diffuses with the increase of the defocus amount is modulated into two main lobes that rotate continuously with the system defocus amount, and the light intensity is always kept in a relatively concentrated state. The rotation angle of the two main lobes is directly related to the depth information. After the laser emitted by the laser reference point is collimated by the objective lens 2 5, it is phase modulated by the central area 8 in the Fourier plane of the 4f system, and converges to the sensor 7 through the objective lens 1 3 of the 4f optical path. The PSF no longer diffuses with the increase of the defocus amount, and the two main lobes rotate continuously with the change of the position of the laser reference point. The rotation angle changes with the axial displacement of the laser reference point, and the imaging position of the PSF on the plane of the sensor 7 changes with the lateral displacement of the laser reference point. The phase of the central area 8 is obtained by the Fresnel zone method. The phase is related to the total number of Fresnel zones L and the radius of the phase plate R1. The spacing between the two main lobes and the axial range corresponding to a 180° rotation are changed only by modifying the total number of Fresnel zones L. The optical path transmission of the 4f system is derived according to the Fresnel diffraction principle, and the sensitivity of the point spread function (PSF) rotation angle θ to the axial displacement Δz of the object is obtained:

[0042]

[0043] Wherein, NA is the numerical aperture of the 4f system; L is the total number of Fresnel bands; λ is the system measurement wavelength;

[0044] When L is constant, that is, the phase of the central area 8 is constant, the measurement range can be adjusted by adjusting the numerical aperture NA of the 4f system, and a higher precision measurement can be performed in a small axial displacement range. The numerical aperture NA of the 4f system is R1 / f1, where f1 is the focal length of the objective lens 3 of the 4f system, and NA is adjusted by adjusting f1.

[0045] The inclination measurement phase part includes an annular region 9, which is used to modulate the standard spherical wavefront phase to make it consistent with the reference mirror 6 surface type, so as to realize dual-axis inclination measurement;

[0046] The positioning holographic phase portion includes a wavefront modulated annular reflection region 10 for positioning the CGH4 and a wavefront modulated point transmission region 11 for positioning the reference mirror 6 .

[0047] An embodiment of the present invention provides an optical manufacturing assembly auxiliary zero-position calibration measurement method based on CGH, which is applied to the above-mentioned system. The measurement process of the method is divided into a calibration phase and a measurement phase. The specific steps are as follows:

[0048] The calibration phase includes:

[0049] Step S11: using the reflection area 10 to locate and calculate the relative position of the CGH 4, when the interference pattern contrast of the standard spherical interferometer 1 is zero, the position of the CGH 4 can be accurately located and calculated.

[0050] Step S12: Use the transmission area 11 to locate the reference mirror 6. After the incident light is modulated, its third-order diffraction light projects two vertical line segments at the specified position on the edge of the reference mirror 6 to form a crosshair as a positioning reference. One crosshair is projected in each of the positive and negative directions of X and Y, forming a total of eight crosshairs; at the same time, the measuring reflector is fine-tuned so that the first to sixth terms of the Zernike coefficient are less than 0.01 (according to calculations, it is believed that the system has been zeroed at this time, and the inherent error is very small and the impact on the measurement accuracy can be ignored), so as to accurately locate the position of the reference mirror 6.

[0051] Step S13: According to step S11, the position of CGH 4 is accurately located, that is, the position of the Fourier surface of the 4f system is located; according to step S12, the position of the reference mirror 6 is accurately located, that is, the reference position of the laser point is located; the positions of the objective lens and the sensor 7 are further located. When the rotation angle of the two main lobe spots displayed on the plane of the sensor 7 is 0°, the displacement measurement calibration is completed, the entire measurement system is in the "zeroing" state, and the measurement can begin.

[0052] The measurement phase includes:

[0053] Step S21: using an interferometric measurement module to perform a rough measurement of the pitch angle, yaw angle, and axial displacement;

[0054] Step S22: According to the rough axial displacement, the focal length of the objective lens in the PSF measurement module is adjusted to narrow the measurement range to near the displacement value, and the axial displacement is further measured with high precision; according to the pitch angle and yaw angle, the lateral displacement is further measured with high precision; and finally multi-dimensional measurement is achieved.

[0055] The above are only preferred embodiments of the present invention. It should be pointed out that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. These should also be regarded as the protection scope of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. The optical manufacturing and adjustment auxiliary zero calibration measurement system based on CGH is characterized by: include: An interferometric measurement module is used for rough measurement of pitch angle, yaw angle and axial displacement, and has an interferometric optical path; the interferometric measurement module includes a standard spherical interferometer and a reference mirror; The improved PSF measurement module is used for high-precision measurement of axial displacement and measurement of large lateral eccentric displacement, and is an optical 4f system; the improved PSF measurement module comprises a laser reference point, a sensor and two objective lenses, the laser reference point is installed in the central area of ​​the reference mirror support structure, and the two objective lenses include objective lens 1 and objective lens 2; A semi-transparent and semi-reflective mirror is used to separate the measurement light of the improved PSF measurement module and the interference measurement module. One part of the measurement light in the interference measurement module enters the standard spherical interferometer, and the other part enters the sensor plane. CGH, installed in the Fourier plane of the 4f system, is used to phase modulate the interferometric measurement module and the improved PSF measurement module, including: Improve the PSF measurement phase part, including the central area, for phase modulation, and achieve axial / lateral displacement measurement by changing the PSF shape on the sensor; The inclination measurement phase part includes an annular region, which is used to modulate the standard spherical wavefront phase to make it consistent with the reference mirror type, thereby realizing dual-axis inclination measurement; The positioning holographic phase part includes a wavefront modulated annular reflection area for positioning the CGH and a wavefront modulated point transmission area for positioning the reference mirror.

2. The CGH-based optical manufacturing and adjustment auxiliary zero-position calibration measurement system according to claim 1 is characterized in that: The central region modulates the standard PSF that diffuses as the defocus amount increases into two main lobes that continuously rotate as the system defocus amount changes by modulating the phase.

3. The CGH-based optical manufacturing and adjustment auxiliary zero-position calibration measurement system according to claim 2, characterized in that: The phase of the central area is obtained by the Fresnel zone method, and the phase is related to the total number of Fresnel zones L and the radius R1 of the phase plate, and the spacing between the two main lobes and the axial range corresponding to their rotation of 180° are changed only by modifying the total number of Fresnel zones L. The optical path transmission of the 4f system is derived according to the Fresnel diffraction principle, and the sensitivity of the PSF rotation angle θ to the axial displacement Δz of the object is obtained. When L remains unchanged, that is, the phase of the central area remains unchanged, the numerical aperture NA of the 4f system is adjusted to adjust the size of the measurement range, and high-precision measurement is performed in a small axial displacement range; NA = R1 / f1, f1 is the focal length of the objective lens of the 4f system, and NA is adjusted by adjusting f1.

4. The CGH-based optical manufacturing and adjustment auxiliary zero-position calibration measurement system according to claim 3 is characterized in that: The laser emitted by the laser reference point is collimated by objective lens 2, and then phase-modulated by the central area in the Fourier plane of the 4f system. After passing through objective lens 1 of the optical path of the 4f system, it reaches the sensor, and the PSF no longer diffuses with the increase of the defocus amount. The two main lobes rotate continuously with the position of the laser reference point, and the rotation angle changes with the axial displacement of the laser reference point. The imaging position of the PSF on the sensor plane changes with the lateral displacement of the laser reference point.

5. The CGH-based optical manufacturing and adjustment auxiliary zero-position calibration measurement system according to claim 1, characterized in that: The wavelength of light used by the standard spherical interferometer is 632.8 nm.

6. The CGH-based optical manufacturing and adjustment auxiliary zero-position calibration measurement system according to claim 1, characterized in that: The wavelength of the laser reference point is 520 nm.

7. An optical manufacturing assembly auxiliary zero-position calibration measurement method based on CGH, applied to a system as claimed in any one of claims 1 to 6, characterized in that: The measuring method comprises the following steps: The calibration phase includes: Step S11: Utilize the reflection area to locate and calculate the relative position of the CGH. When the interference pattern contrast of the standard spherical interferometer is zero, the position of the CGH can be accurately located and calculated. Step S12: Using the transmission area to locate the reference mirror, after the incident light is modulated, its third-order diffraction light projects two vertical line segments at the specified position of the edge of the reference mirror to form a cross line as a positioning reference, and one cross line is projected in each of the positive and negative directions of X and Y, forming a total of eight cross lines; at the same time, fine-tune the measuring reflector so that the first to sixth terms of the Zernike coefficient are less than 0.01, so that the position of the reference mirror can be accurately located; Step S13: accurately locate the CGH position according to step S11, that is, locate the position of the Fourier surface of the 4f system; accurately locate the reference mirror position according to step S12, that is, locate the reference position of the laser point; further locate the position of the objective lens and the sensor, and when the rotation angle of the two main lobe spots displayed on the sensor plane is 0°, the displacement measurement calibration is completed; The measurement phase includes: Step S21: using an interferometric measurement module to perform a rough measurement of the pitch angle, yaw angle, and axial displacement; Step S22: According to the rough axial displacement, the focal length of the objective lens in the PSF measurement module is adjusted to narrow the measurement range to near the displacement value, and the axial displacement is further measured with high precision; according to the pitch angle and yaw angle, the lateral displacement is further measured with high precision; and finally multi-dimensional measurement is achieved.

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