A large-aperture optical element stress detection device and detection method thereof

Abstract

The present invention provides a large-aperture optical stress detection device and a detection method thereof. The detection optical path uses a linearly polarized laser as the input detection light, which is expanded by a converging lens, then collimated by a beam splitter prism and a large-aperture collimating objective lens to enter a large-aperture component to be tested, then reflected by a standard reflector, passes through the component to be tested again, converged by a collimator and reflected by a beam splitter prism, and then collimated by a collimator. Finally, a polarization camera is used to collect light intensity information, and visualization of stress in a large-aperture sample is realized through back-end data processing. Compared with the traditional detection optical path, the optical path does not require a wave plate, and does not require any rotation or movement of any components, so that real-time detection of large-aperture stress birefringence can be realized, thereby avoiding errors introduced by wave plates and motion platforms. The method does not require the use of a splicing algorithm, can simultaneously obtain the stress distribution of the entire large-aperture sample, and is easy to integrate with the existing large-aperture interference optical path.

Description

Technical Field

[0001] The present invention belongs to the field of optical detection, and in particular relates to a large-caliber optical stress detection device and a detection method thereof. Background Art

[0002] The magnitude of residual stress is an important indicator for evaluating the performance of optical components, especially for large-diameter components. When there is a large internal stress, the optical glass may break by itself because it is heated, pressed or rapidly cooled during processing. Even if the internal stress is not too large, the surface of the processed optical parts will slowly deform over time due to the internal stress, seriously affecting the imaging quality. In addition, due to the existence of internal stress, the isotropic properties of optical glass are destroyed; due to the uneven distribution of internal stress, the optical uniformity quality will be reduced, resulting in inconsistent refractive index distribution, which will cause the wavefront to deform after passing through the optical glass and deteriorate the image quality.

[0003] The birefringence detection of large-aperture optical materials has important applications in the growth and processing of high-power laser materials, and the influence of stress is even more difficult to avoid during the processing and manufacturing process. In many important national application projects and scientific research experiments, such as high-power large-scale laser experiments, large-aperture optical components are required, and the quality of optical components is an important factor in ensuring the success of the entire experiment. Therefore, in the manufacture of large-aperture optical materials and components, it is extremely important to accurately determine stress birefringence and its spatial distribution.

[0004] For existing stress detection devices, the larger the measuring aperture, the more zero-order wave plates of the same aperture must be equipped, which is a disadvantage that is difficult to overcome. In addition, existing measurement methods are usually based on interferometric measurement technology, and the sample to be measured needs to be moved during the measurement. Moving large-aperture samples will inevitably produce large measurement errors. Therefore, current domestic technology cannot achieve stress detection with an aperture of 1m or above. Summary of the invention

[0005] The purpose of the present invention is to provide a large-aperture optical stress detection device and a detection method thereof, which improves the traditional scissor-type optical path structure and introduces a polarization camera at the receiving end. This method does not require the use of a splicing algorithm and can simultaneously obtain the stress distribution of the entire large-aperture sample. Moreover, the optical path does not require a wave plate and does not require rotating or moving any parts, so it can achieve real-time detection of large-aperture stress birefringence, avoiding errors introduced by wave plates and motion platforms.

[0006] The technical solution to realize the present invention is: a large-aperture optical stress detection device, which utilizes a prism-type optical path, including a linearly polarized light source, a converging lens, a beam splitter, a first collimating lens, a standard reflector, a second collimating lens, and a polarization camera. The linearly polarized light source, the converging lens, the beam splitter, the first collimating lens, the component to be measured, and the standard reflector are arranged in sequence along the first optical axis, and the second collimating lens and the polarization camera are arranged in sequence along the second optical axis. The first optical axis is located on the transmission light path of the beam splitter, and the second optical axis is located on the reflection light path of the beam splitter.

[0007] The linearly polarized light source emits a laser, which is converged by a converging lens, transmitted through a beam splitter prism, and expanded and collimated by a collimating lens. After the expanded light passes through the component to be tested, a phase delay is generated. The light carrying the stress information of the component to be tested is reflected by a standard reflector along the original optical path to the beam splitter prism, reflected by the beam splitter prism, and received by a polarization camera after passing through the second collimating lens. The light passes through the component to be tested twice in total, and the stress birefringence finally solved is twice the actual value.

[0008] The detection method of the large-aperture optical stress detection device comprises the following steps:

[0009] Step 1: First, build the first optical axis optical path, and adjust the linear polarized light source, the converging lens, the beam splitter, the first collimating lens, and the standard reflector to a coaxial state without adding the component to be tested.

[0010] Step 2: Place the beam expander and collimator lens at the second optical axis so that the light reflected by the standard reflector is received by the target surface of the polarization camera after beam expansion and collimation.

[0011] Step 3: Rotate the polarization camera so that the emission direction of the linear polarized light is parallel to the 90° unit of the polarization camera. Assuming that the initial linear polarized light is along the y-axis direction and the amplitude is 2a, the complex amplitude E of the linear polarized light emitted by the linear polarized light source is:

[0012] E=2a cos ωt

[0013] Where ω represents the angular frequency and t represents the time.

[0014] Step 4: Place the component to be tested between the first collimating lens and the standard reflector. After the linearly polarized light passes through the component to be tested, due to the existence of the crystal birefringence effect, o-light and e-light will generate The phase difference of the linear polarized light is α, assuming that the angle between the fast axis of the element to be tested and the incident linear polarized light is α, then the phase difference of the linear polarized light after birefringence is The complex amplitude E in the x direction after the DUT is x , the complex amplitude E in the y direction y They are:

[0015]

[0016] The complex amplitudes P0, P received by the 0°, 45°, 90°, and 135° units of the polarization camera 45 , P 90 , P 135 They are:

[0017]

[0018] The four polarization units collect the light intensity information I0, I 45 ,I 90 ,I 135 They are:

[0019]

[0020] Step 5: The light passes through the component to be tested twice and finally irradiates the target surface of the polarization camera. The four polarization units collect the light intensity information I0, I 45 ,I 90 ,I 135 , simplify the above formula to get:

[0021]

[0022] Therefore, the light intensity information of the three polarization units is used to calculate the amplitude 2a, the angle between the fast axis direction of the component under test and the incident polarized light, and the phase difference

[0023] Compared with the prior art, the present invention has the following significant advantages:

[0024] (1) Compared with the traditional detection optical path, this optical path does not need to consider the adjustment of the polarization angle of the polarizer and analyzer, does not need to add additional phase delay wave plates (half wave plates, quarter wave plates) in the optical path, and does not need to rotate or move any parts. It can realize real-time detection of large-aperture stress birefringence and avoid the errors introduced by wave plates and motion platforms.

[0025] (2) This method is based on the acquisition of polarized light intensity at four equally spaced points. It does not require the use of a stitching algorithm and can simultaneously obtain the stress distribution of the entire large-aperture sample. It is also easy to integrate with existing large-aperture interferometer optical paths.

[0026] (3) Only the light intensity information is needed to calculate the phase difference, and thus the stress magnitude. This method can theoretically measure the stress magnitude of components with any aperture, especially optical components with an aperture of 1 m or more. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structure of the entire detection device.

[0028] Figure 2 Schematic diagram of the collimated beam expansion optical path.

[0029] Figure 3 Schematic diagram of the target surface structure of a polarization camera.

[0030] Figure number identification: 1. Linear polarized light source; 2. Converging lens; 3. Beam splitter prism; 4. Beam expander and collimator lens; 5. Component to be tested; 6. Standard reflector; 7. Beam expander and collimator lens; 8. Polarization camera.

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the technical solution of the present invention is further described below in conjunction with the embodiments shown in the accompanying drawings. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0034] In addition, in the present invention, the descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0035] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0036] Combination Figure 1 to Figure 3The large-aperture optical stress detection device described in the present invention includes a linearly polarized light source 1, a converging lens 2, a dichroic prism 3, a first collimating lens 4, a standard reflector 6, a second collimating lens 7, and a polarization camera 8. The linearly polarized light source 1, the converging lens 2, the dichroic prism 3, the first collimating lens 4, the component to be measured 5, and the standard reflector 6 are arranged in sequence along the first optical axis, and the second collimating lens 7 and the polarization camera 8 are arranged in sequence along the second optical axis.

[0037] In this embodiment, a linearly polarized light source 1 emits a laser, which is converged by a converging lens 2, transmitted through a beam splitter prism 3, and expanded and collimated by a collimating lens 4. After the expanded light passes through a component to be measured 5, a phase delay is generated. The light carrying the stress information of the component to be measured 5 is reflected by a standard reflector 6 along the original optical path to the beam splitter prism 3, reflected by the beam splitter prism 3, and received by a polarization camera 8 after passing through a second collimating lens 7. The light passes through the component to be measured 5 twice in total, and the magnitude of the stress birefringence finally solved is twice the actual value.

[0038] The linearly polarized light source 1 generates linearly polarized laser light, including o-light and e-light, and there is no need to add a zero-order wave plate in the optical path to change the phase.

[0039] Every four polarization units of the target surface of the polarization camera 8 are a whole, and the four polarization units are respectively 0°, 45°, 90°, and 135°. Therefore, when collecting light, there is no need to add an additional filter or analyzer in front of the polarization camera 8, which simplifies the structure of the entire system. In addition, the entire system does not require manual rotation of a certain device, avoiding the problem of having to rotate the material when detecting material stress using the traditional quarter-wave plate method.

[0040] The o-light and e-light are superimposed on the target surface of the polarization camera, and the light intensity information is received by each polarization unit (0°, 45°, 90°, 135°) of the polarization camera. The measurement of the stress magnitude of the component to be measured is converted into the measurement of the light intensity received by each polarization unit. The stress magnitude of the large-aperture optical component is intuitively reflected through the light intensity information.

[0041] The detection method of the large-aperture optical stress detection device comprises the following steps:

[0042] Step 1: First, build the first optical axis optical path, and adjust the linear polarized light source 1, the converging lens 2, the beam splitter prism 3, the first collimating lens 4, and the standard reflector 6 to a coaxial state without adding the component to be measured.

[0043] Step 2: Place the beam expander and collimator lens 7 at the second optical axis, so that the light reflected by the standard reflector 6 is received by the target surface of the polarization camera after beam expansion and collimation.

[0044] Step 3, rotate the polarization camera 8 so that the emission direction of the linear polarized light is parallel to the 90° unit of the polarization camera; assuming that the initial linear polarized light is along the y-axis direction and the amplitude is 2a, then the complex amplitude E of the linear polarized light emitted by the linear polarized light source 1 is:

[0045] E=2a cos ωt

[0046] Where ω represents the angular frequency and t represents the time.

[0047] Step 4: Place the DUT 5 between the first collimating lens 4 and the standard reflector 6. After the linearly polarized light passes through the DUT 5, due to the existence of the crystal birefringence effect, the o-light and the e-light will generate The phase difference of the linear polarized light is α, assuming that the angle between the fast axis of the element to be tested 5 and the incident linear polarized light is α, then the phase difference of the linear polarized light after birefringence is The complex amplitude E of the DUT in the x direction after 5 x , the complex amplitude E in the y direction y They are:

[0048]

[0049] The complex amplitudes P0, P received by the 0°, 45°, 90°, and 135° units of the polarization camera 8 45 , P 90 , P 135 They are:

[0050]

[0051] According to the formula derivation, we can get the light intensity information I0, I 45 ,I 90 ,I 135 They are:

[0052]

[0053] Step 5: The light passes through the element to be tested 5 twice and finally irradiates the target surface of the polarization camera 8. The four polarization units collect the light intensity information I0, I 45 ,I 90 ,I 135 , simplify the above formula to get:

[0054]

[0055] Therefore, the light intensity information of three units is used to calculate the amplitude 2a, the angle between the fast axis direction of the element under test 5 and the incident polarized light α, and the phase difference

[0056] It should be noted that the test light in this optical path passes through the component to be tested twice, so the stress magnitude obtained is twice the actual stress magnitude.

Claims

1. A large-aperture optical stress detection device, using a scissor-type optical path, characterized in that: The invention comprises a linear polarized light source (1), a converging lens (2), a beam splitter prism (3), a first collimating lens (4), a standard reflector (6), a second collimating lens (7), and a polarization camera (8); the linear polarized light source (1), the converging lens (2), the beam splitter prism (3), the first collimating lens (4), a component to be measured (5), and the standard reflector (6) are arranged in sequence along a first optical axis; the second collimating lens (7) and the polarization camera (8) are arranged in sequence along a second optical axis; the first optical axis is located on a transmission light path of the beam splitter prism (3), and the second optical axis is located on a reflection light path of the beam splitter prism (3); A linearly polarized light source (1) emits laser light, which is converged by a converging lens (2), transmitted by a beam splitter prism (3), expanded and collimated by a first collimating lens (4), and the expanded light generates a phase delay after passing through a component to be measured (5). The light carrying stress information of the component to be measured (5) is reflected by a standard reflector (6) and reflected along the original light path to the beam splitter prism (3), and is reflected by the beam splitter prism (3) and received by a polarization camera (8) after passing through a second collimating lens (7). The light passes through the component to be measured (5) twice in total, and the stress birefringence magnitude finally solved is twice the actual value.

2. The large-aperture optical stress detection device according to claim 1, characterized in that: The linearly polarized light source (1) generates linearly polarized laser light, including o-light and e-light.

3. The large-aperture optical stress detection device according to claim 1, characterized in that: Every four polarization units on the target surface of the polarization camera (8) form a whole, and the four polarization units are respectively 0°, 45°, 90°, and 135°.

4. The detection method of the large-aperture optical stress detection device according to any one of claims 1 to 3, characterized in that: Here are the steps: Step 1: First, build a first optical axis optical path, and adjust the linear polarized light source (1), the converging lens (2), the beam splitter (3), the first collimating lens (4), and the standard reflector (6) to a coaxial state without adding a component to be measured; Step 2, placing the second collimating lens (7) at the second optical axis, so that the light reflected by the standard reflector (6) is received by the target surface of the polarization camera (8) after being expanded and collimated; Step 3, rotate the polarization camera (8) so that the emission direction of the linear polarized light is parallel to the 90° unit of the polarization camera (8); assuming that the initial linear polarized light is along the y-axis direction and the amplitude is 2a, then the complex amplitude E of the linear polarized light emitted by the linear polarized light source (1) is: E=2a cosωt Where, ω represents the angular frequency and t represents the time; Step 4: Place the component to be tested (5) between the first collimating lens (4) and the standard reflector (6). After the linearly polarized light passes through the component to be tested (5), due to the existence of the crystal birefringence effect, the o-light and the e-light will generate The phase difference of the linear polarized light is α, assuming that the angle between the fast axis of the element to be tested (5) and the incident linear polarized light is α, then the phase difference of the linear polarized light after birefringence is The complex amplitude E in the x direction after the DUT (5) x , the complex amplitude E in the y direction y They are: The complex amplitudes P0, P received by the 0°, 45°, 90°, and 135° units of the polarization camera (8) 45 , P 90 , P 135 They are: The four polarization units collect the light intensity information I0, I 45 ,I 90 ,I 135 They are: Step 5: The light passes through the component to be tested (5) twice and finally irradiates the target surface of the polarization camera (8). The four polarization units collect light intensity information I0, I 45 ,I 90 ,I 135 , simplify the above formula to get: Therefore, the light intensity information of the three polarization units is used to calculate the amplitude 2a, the angle α between the fast axis direction of the element under test (5) and the incident polarized light, and the phase difference 5. The detection method of the large-aperture optical stress detection device according to claim 4, characterized in that: It is capable of inspecting optical components with a diameter of 1m or more.

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