Device and method for detecting off-axis wedge-shaped lens

Abstract

The invention discloses an off-axis wedge-shaped lens detection device and method. The wedge-shaped lens detection device mainly comprises a dynamic interferometer, a spherical lens, an alignment cross wire, a parallel plate, a standard reflector and an auto-collimation collimator. According to the invention, the auto-collimation collimator is matched with the parallel plate and the alignment cross wire to carry out reference transmission so as to complete optical path calibration, and the dynamic interferometer is used to detect transmission wave surface error data of the off-axis wedge-shaped lens. And processing and calculating to obtain PV and GRMS values of the wave surface according to the wave surface error data. The method can be widely applied to detection of transmission wave surfaces, off-axis amount and rear intercept of off-axis wedge-shaped lenses with different shapes and sizes, and is particularly suitable for a monitoring scheme requiring high-precision control of the off-axis amount. Measurement results are fed back to guide machining, and the machining quality of the off-axis wedge-shaped lens can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of optical detection, and is a detection device and method for off-axis wedge lenses, which can be widely used in high-precision detection of off-axis wedge lenses of various shapes and sizes, and is particularly suitable for monitoring schemes that require high-precision control of off-axis quantities. Background Art

[0002] The off-axis wedge lens can be regarded as a part of the plano-convex lens. It is mainly used for beam focusing and beam harmonic color separation in large high-power laser devices. When parallel light passes through the off-axis wedge lens, it will produce a convergence effect on the main optical axis of the lens. The distance between the central axis of the lens and the optical axis is the off-axis amount. The off-axis wedge lens is usually processed by a variety of composite processes such as ultra-precision grinding, airbag polishing and small tool CNC polishing. The off-axis amount, back intercept and transmitted wavefront error are important technical indicators for the grinding and polishing of off-axis wedge lenses.

[0003] At present, the mainstream test method for the transmitted wavefront is the interference method. However, due to the special shape of the off-axis wedge lens, it is difficult to calibrate the optical path if it is adjusted only by experience. Similar coaxial wedge lens measurement indicators are mainly wedge angle difference and pyramidal error. Researchers have proposed a method for measuring the wedge angle difference and pyramidal error of a coaxial wedge lens using a dynamic interferometer, which includes optical path adjustment means and calculation methods [201310210297.X]. The optical properties of the coaxial wedge lens and the off-axis wedge lens are different, and the measurement method cannot be directly transferred. The present invention proposes a method for using a laser rangefinder and a 4D dynamic interferometer to respectively detect the back intercept, off-axis amount and transmission wavefront error of an off-axis wedge lens, and at the same time describes in detail the reference transfer and optical path calibration scheme. The present invention can be widely used in the detection of various off-axis wedge lenses, and the measurement result feedback guides the processing, which can effectively improve the processing quality of the off-axis wedge lens. Summary of the invention

[0004] The purpose of the present invention is to provide a detection device and method for an off-axis wedge lens, which can accurately measure the off-axis amount of the wedge lens and the transmission wavefront errors PV and GRMS, so as to provide feedback to guide processing.

[0005] The technical solution of the present invention is as follows:

[0006] In one aspect, the present invention provides a detection device for an off-axis wedge lens, which is characterized in that it includes:

[0007] Dynamic interferometer, equipped with a four-dimensional adjustment frame, for measuring wavefront errors;

[0008] An off-axis wedge lens fixture is provided with a three-dimensional adjustment frame for clamping and positioning the off-axis wedge lens to be tested;

[0009] Standard reflector, equipped with a two-position adjustment mount, used to reflect the light beam to form an interference pattern;

[0010] A collimator equipped with a two-dimensional adjustment frame is used to generate a parallel light beam and calibrate the light path;

[0011] Parallel plates, equipped with a two-dimensional adjustment mount, serve as a calibration tool to ensure the parallelism of the beam;

[0012] Crosshairs, equipped with a three-dimensional adjustment frame, are used to accurately locate and adjust the beam position;

[0013] The dynamic interferometer, the off-axis wedge lens to be measured and the standard reflector are sequentially placed on a measuring platform, and the precise calibration and measurement of the optical path are achieved by adjusting the position and angle of each component.

[0014] The detection device according to claim 1, further comprising:

[0015] The spherical lens is installed in front of the dynamic interferometer and is used to converge the plane wave into a spherical wave to generate a point light source, and the focus of the spherical lens coincides with the focus of the off-axis wedge lens to be measured;

[0016] Interferometer pinhole plate, used to reduce the test beam to a circular hole of a predetermined size to improve measurement accuracy.

[0017] On the other hand, the present invention also provides a method for off-axis wedge lens detection using the above detection device, which is characterized in that it includes the following steps:

[0018] S1. Use a collimator and a parallel plate to calibrate the parallelism of the light beam;

[0019] S2. Adjust the two-dimensional tilt of the standard reflector to ensure that the light beam can accurately return to the collimator and be at the center of the cross wire;

[0020] S3. Install the off-axis wedge lens to be tested on the off-axis wedge lens fixture, and adjust the two-dimensional tilt of the fixture so that the light beam can accurately return to the collimator;

[0021] S4. Use the crosshairs to determine the ideal optical axis position of the off-axis wedge lens to be tested;

[0022] S5. Adjust the position and angle of the dynamic interferometer so that it can receive and measure the light beam passing through the off-axis wedge lens to be measured;

[0023] S6. By installing a pinhole plate and a spherical lens, the test beam is reduced and projected onto the off-axis wedge lens to be tested;

[0024] S7. Adjust the position and angle of the off-axis wedge lens to be tested and the standard reflector so that the test beam returns to the dynamic interferometer and is in a zero position inspection state;

[0025] S8. Use a laser rangefinder to measure the distance from the focus of the spherical lens to the center of the front surface of the off-axis wedge lens to be measured, and calculate the back intercept of the off-axis wedge lens to be measured based on the known theoretical off-axis value and the Pythagorean theorem;

[0026] S9. Use a dynamic interferometer to measure the wavefront error of the transmitted wavefront, and perform data processing to obtain the wavefront error peak-to-valley value (PV) and the wavefront error gradient root mean square (GRMS).

[0027] Further, the method further comprises the following steps:

[0028] Before measuring the wavefront error, the measurement area is cropped, local invalid points are filled, and four-mirror transformation low-pass filtering is performed to improve the accuracy and reliability of the measurement data.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1) The present invention proposes a set of refined optical path adjustment steps, including calibration of a collimator and a parallel plate, tilt adjustment of a standard reflector, tilt adjustment of an off-axis wedge lens fixture, and precise positioning of a crosshair and a dynamic interferometer, etc., to ensure precise calibration of the optical path and accurate alignment of the measurement beam, thereby improving the accuracy and stability of the measurement.

[0031] 2) The interferometric measurement data processing method, including the steps of cropping the effective measurement area, filling the local invalid points, and four-mirror transformation low-pass filtering, can eliminate the noise and error in the measurement process and improve the accuracy and reliability of the measurement data.

[0032] 3) By calculating the wavefront error peak-to-valley value (PV) and the wavefront error gradient root mean square (GRMS), the optical performance of the off-axis wedge lens to be tested can be fully evaluated, making the measurement results more comprehensive and accurate, providing strong support for lens quality control. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the adjustment of the standard reflector and the off-axis wedge lens to be measured in the present invention.

[0034] Figure 2 This is a schematic diagram of the dynamic interferometer adjustment in the present invention.

[0035] Figure 3 This is the final measurement optical path schematic diagram of the present invention

[0036] Figure 4 Flow chart of the detection method of the off-axis wedge lens of the present invention DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments, but this should not limit the protection scope of the present invention.

[0038] This embodiment relates to the detection of off-axis wedge lenses, including the detection of their theoretical off-axis amount, theoretical back intercept and overall dimensions. In order to achieve this goal, a set of detection devices and methods are designed.

[0039] The theoretical off-axis distance of the measured wedge lens is 300mm, the theoretical back intercept is 5163.86mm, and the overall dimensions are 430mm×430mm.

[0040] See also Figure 1 and Figure 3 , Figure 1 is a schematic diagram of the adjustment of the standard reflector and the off-axis wedge lens to be measured in the present invention, Figure 3 The final measurement optical path schematic diagram of the present invention includes:

[0041] Dynamic interferometer 1, equipped with a four-dimensional adjustment frame, is used to measure the wavefront error;

[0042] The off-axis wedge lens fixture 7 is equipped with a three-dimensional adjustment frame for clamping and positioning the off-axis wedge lens 5 to be tested; and the off-axis wedge lens fixture 7 is provided with a positioning surface for locating the off-axis wedge lens clamping position;

[0043] A standard reflector 6, provided with a two-dimensional adjustment mount, for reflecting the light beam to form an interference pattern;

[0044] A collimator 3, equipped with a two-dimensional adjustment frame, is used to generate a parallel light beam and calibrate the light path;

[0045] A parallel plate 4, equipped with a two-dimensional adjustment frame, serves as a calibration tool to ensure the parallelism of the light beam;

[0046] Crosshair 2, equipped with a three-dimensional adjustment frame, is used to accurately locate and adjust the beam position;

[0047] The dynamic interferometer 1, the off-axis wedge lens 5 to be measured and the standard reflector 6 are sequentially placed on the measuring platform, and the precise calibration and measurement of the optical path are achieved by adjusting the position and angle of each component.

[0048] A spherical lens is installed in front of the dynamic interferometer 1 to converge the plane wave into a spherical wave to generate a point light source, and the focus of the spherical lens coincides with the focus of the off-axis wedge lens 5 to be measured. The standard reflector 6 is placed behind the off-axis wedge lens 5 and parallel to the plane side of the off-axis wedge lens 5. The spherical light beam passes through the off-axis wedge lens 5 and returns to the dynamic interferometer 1 via the standard reflector 6.

[0049] See also Figure 4 , Figure 41 is a flow chart of a method for detecting an off-axis wedge lens of the present invention. As shown in the figure, the detection method comprises the following steps:

[0050] ①Optical path adjustment, such as Figure 1 As shown:

[0051] A collimator 3 and a parallel plate 4 are placed on the measuring platform in sequence to calibrate the parallelism of the light beam. The collimator light beam emitted from the collimator 3 is aligned with the parallel plate 4, and the two-dimensional tilt of the collimator 3 is adjusted so that the collimator light beam is incident vertically on the parallel plate 4.

[0052] After the standard reflector 6 is placed on the parallel plate 4, the collimator light beam is aligned with the standard reflector 6, and the two-dimensional inclination of the standard reflector 6 is adjusted so that the collimator light beam returns to the collimator 3 and is at the cross center of the collimator.

[0053] ②Install and adjust the off-axis wedge lens 5 to be tested:

[0054] The off-axis wedge lens fixture 7 is placed between the parallel plate 4 and the standard reflector 6, and the workbench of the off-axis wedge lens fixture (7) is pre-leveled. The off-axis wedge lens 5 to be measured is mounted on the off-axis wedge lens fixture 7, and it is ensured that the side surface and the light-transmitting plane of the off-axis wedge lens 5 to be measured are close to the positioning surface of the off-axis wedge lens fixture 7, and the light-transmitting plane of the off-axis wedge lens 5 to be measured faces the dynamic interferometer 1.

[0055] The two-dimensional tilt of the off-axis wedge lens fixture 7 is adjusted so that the light beam can return to the collimator 3 and be located at the cross center of the collimator.

[0056] Use the crosshairs 2 to determine the ideal optical axis position of the off-axis wedge lens 5 to be tested, such as Figure 2 As shown, place the crosshair 2 and use a three-dimensional coordinate measuring instrument to adjust the three-dimensional translation of the crosshair 2 so that the center of the crosshair 2 is located on the ideal optical axis of the off-axis wedge lens 5 to be measured, that is, the center of the crosshair 2 is 300 mm away from the central axis of the off-axis wedge lens 5 to be measured.

[0057] ③Dynamic interferometer measurement:

[0058] The dynamic interferometer 1 is placed, and the initial position of the dynamic interferometer 1 is roughly adjusted using a tape measure, so that the distance between the light transmission plane of the off-axis wedge lens 5 to be measured and the light beam emission port of the dynamic interferometer 1 is close to 5163 mm.

[0059] Turn on the power switch of dynamic interferometer 1 and warm it up for more than 4 hours;

[0060] The position and angle of the dynamic interferometer 1 are adjusted so that it can receive and measure the light beam passing through the off-axis wedge-shaped lens 5 to be measured and is in a zero position inspection state.

[0061] Install the interferometer pinhole plate, reduce the test beam to a 1 mm round hole, and adjust the two-dimensional translation of the dynamic interferometer 1 so that the center of the test beam is aligned with the center of the crosshairs 2.

[0062] like Figure 3 As shown, the interferometer pinhole plate is removed, the parallel plate 4 is withdrawn, and the spherical lens is installed to project the reduced test light beam onto the off-axis wedge lens 5 to be tested, and the off-axis wedge lens 5 to be tested is adjusted to move along the optical axis and the two-dimensional tilt of the standard reflector 6 is fine-tuned, so that the test light beam returns to the dynamic interferometer 1 in a zero-position inspection state, and the focus of the spherical lens coincides with the focus of the off-axis wedge lens 5 to be tested.

[0063] ④ Calculation of theoretical off-axis distance and back intercept:

[0064] Use a laser rangefinder to measure the distance s1 from the focus A of the spherical lens to the center of the front surface of the off-axis wedge lens 5 to be measured. The distance from the center of the front surface of the off-axis wedge lens 5 to the optical axis is known (i.e., the theoretical off-axis amount t).

[0065] According to the known theoretical off-axis value and the Pythagorean theorem, the back intercept s2 of the off-axis wedge lens to be tested is calculated as follows:

[0066]

[0067] The interferometer measurement results are used to determine whether the actual off-axis value meets the tolerance requirements. The off-axis value is 300 mm ± 1 mm, and the back intercept is 5163.86 mm ± 5 mm, which meets the requirements.

[0068] ⑤ Wavefront error measurement and data processing:

[0069] The wavefront error of the transmitted wavefront is measured using a dynamic interferometer 1.

[0070] The measured data are processed by cropping, filling invalid points, four-mirror transformation and low-pass filtering.

[0071] Calculate the peak-to-valley value (PV) of the wavefront error and the root mean square (GRMS) of the wavefront error gradient. Before calculation, first crop the effective measurement area, then fill in the local invalid points, and finally perform low-pass filtering through four-mirror transformation. Let the wavefront error matrix be D, and slopex and slopey are the partial derivatives of the matrix D in the x and y directions respectively:

[0072]

[0073] Let grmsm be the wavefront error gradient matrix, and the formula is as follows:

[0074]

[0075] According to D and grmsm, the wavefront error peak-to-valley value PV and the wavefront error gradient root mean square GRMS can be calculated by the following formula, where N is the number of valid data points:

[0076] PV=max(D)-min(D)

[0077]

[0078] The measured transmitted wavefront PV≤λ / 3 (λ=632.8nm) meets the requirement.

[0079] This embodiment provides an efficient and accurate off-axis wedge lens detection method, which can measure its key parameters such as theoretical off-axis amount, theoretical back intercept and external dimensions. The accuracy and reliability of the measurement results are ensured through precise optical path adjustment and data processing.

Claims

1. A detection device for an off-axis wedge lens, characterized in that: include: A dynamic interferometer (1) equipped with a four-dimensional adjustment frame for measuring wavefront errors; An off-axis wedge lens fixture (7) is provided with a three-dimensional adjustment frame and is used for clamping and positioning the off-axis wedge lens (5) to be tested; A standard reflector (6) is provided with a two-position adjustment mount and is used to reflect the light beam to form an interference pattern; A collimator (3) is provided with a two-dimensional adjustment frame and is used to generate a parallel light beam and calibrate the light path; A parallel plate (4) is provided with a two-dimensional adjustment frame, which serves as a calibration tool to ensure the parallelism of the light beam; A crosshair (2) is provided with a three-dimensional adjustment frame for accurately positioning and adjusting the position of the light beam; The dynamic interferometer (1), the off-axis wedge lens to be measured (5) and the standard reflector (6) are placed on a measurement platform in sequence, and the precise calibration and measurement of the optical path are achieved by adjusting the position and angle of each component.

2. The detection device according to claim 1, characterized in that: Also includes: A spherical lens is installed in front of the dynamic interferometer (1) and is used to converge the plane wave into a spherical wave to generate a point light source, and the focus of the spherical lens coincides with the focus of the off-axis wedge lens (5) to be measured; Interferometer pinhole plate, used to reduce the test beam to a circular hole of a predetermined size to improve measurement accuracy.

3. A method for off-axis wedge lens detection using the detection device according to claim 1 or 2, characterized in that: The following steps are involved: S1. Use a collimator (3) and a parallel plate (4) to calibrate the parallelism of the light beam; S2. Adjust the two-dimensional tilt of the standard reflector (6) to ensure that the light beam can accurately return to the collimator (3) and is at the center of the cross wire; S3. The off-axis wedge lens to be tested (5) is mounted on the off-axis wedge lens fixture (7), and the two-dimensional tilt of the fixture is adjusted so that the light beam can accurately return to the collimator (3); S4. Determine the ideal optical axis position of the off-axis wedge lens (5) to be measured using the crosshairs (2); S5. Adjust the position and angle of the dynamic interferometer (1) so that it can receive and measure the light beam passing through the off-axis wedge lens (5) to be measured; S6. By installing a pinhole plate and a spherical lens, the test beam is reduced and projected onto the off-axis wedge lens (5) to be tested; S7. Adjust the position and angle of the off-axis wedge lens (5) and the standard reflector (6) to be tested so that the test beam returns to the dynamic interferometer (1) and is in a zero position test state; S8. Use a laser rangefinder to measure the distance from the focus of the spherical lens to the center of the front surface of the off-axis wedge lens (5) to be measured, and calculate the back intercept of the off-axis wedge lens (5) to be measured based on the known theoretical off-axis amount and the Pythagorean theorem; S9. Use a dynamic interferometer (1) to measure the wavefront error of the transmitted wavefront, and perform data processing to obtain the wavefront error peak-to-valley value (PV) and the wavefront error gradient root mean square (GRMS).

4. The detection method according to claim 3, characterized in that: The following steps are also included: Before measuring the wavefront error, the measurement area is cropped, local invalid points are filled, and four-mirror transformation low-pass filtering is performed to improve the accuracy and reliability of the measurement data.

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