A Plane Polarization Residual Stress Detection Device and Method Based on Spectral Confocality

Abstract

This invention discloses a plane polarization residual stress detection device and method based on spectral confocality, belonging to the field of optical measurement technology. The device mainly includes an illumination collimation component, a polarization modulation component, a dispersion focusing component, a signal detection component, and a data processing component arranged sequentially along the optical path. By incorporating the polarization modulation component and the signal detection component, and utilizing the spectral confocal principle combined with polarization detection technology, this invention achieves non-contact, high-precision measurement of the residual stress of the optical element under test. It solves the problems of sample damage and low efficiency associated with traditional contact measurements, and is applicable to various optical materials, possessing good versatility and engineering application value.

Description

Technical Field

[0001] This invention relates to the field of optical measurement technology, and specifically to a plane polarization residual stress detection device and method based on spectral confocality. Background Technology

[0002] Residual stress is inevitably generated during the fabrication, processing, assembly, and use of optical components. However, excessive or unevenly distributed residual stress can lead to problems such as optical distortion, performance degradation, and component failure, thereby seriously impairing the imaging quality, operational reliability, and lifespan of the optical system. Therefore, the detection of residual stress on the surface of optical components is crucial.

[0003] Existing testing methods can be mainly divided into two categories: destructive (contact) testing and non-destructive (non-contact) testing. Destructive testing usually includes methods such as pinhole testing, strip cutting, and indentation, which can cause irreversible damage to high-value precision optical components, and the measurement accuracy is easily affected by process and human factors. In non-destructive testing, X-ray diffraction has the problems of expensive equipment and high testing threshold, micro Raman spectroscopy has the problem that the accuracy is greatly affected by environmental factors (such as temperature, pressure, vibration, etc.), and white light interferometry has high requirements for environmental stability and complex signal reconstruction.

[0004] Therefore, existing residual stress detection methods cannot meet the requirements of high efficiency, low cost, and high anti-interference, and have become an obstacle to the advancement of optical systems. Summary of the Invention

[0005] This invention provides a plane polarization residual stress detection device and method based on spectral confocality, aiming to overcome the shortcomings of existing residual stress detection methods, such as damage to optical components, high cost, low anti-interference ability, and low detection efficiency.

[0006] In a first aspect, embodiments of the present invention provide a plane polarization residual stress detection device based on spectral confocality, comprising: arranged sequentially along the optical path:

[0007] An illumination collimation assembly for producing parallel incident light;

[0008] A polarization modulation component is used to modulate the incident light into linearly polarized light and to perform spatial filtering on the incident light;

[0009] A dispersive focusing assembly includes a beam splitter and a dispersive objective lens group. The beam splitter is used to reflect filtered incident light to the dispersive objective lens group, and the dispersive objective lens group is used to disperse the filtered incident light axially and focus it on the test point of the optical element under test.

[0010] A signal detection component is used to receive reflected light that has been reflected by the measured point and then passed through the beam splitter; it includes a color sensor that outputs multi-channel color component values ​​of the reflected light.

[0011] A data processing component is used to calculate the measured light intensity based on the color component values, and to calculate the residual stress at the measured point based on the measured light intensity.

[0012] Secondly, embodiments of the present invention provide a method for detecting plane polarization residual stress based on spectral confocality, comprising:

[0013] A standard optical element is placed on a three-dimensional displacement stage, and its axial movement is controlled to perform scanning. The calibrated color component values ​​of the color sensor and the wavelength data of the spectrometer are collected respectively to establish a first correspondence between axial position and wavelength, and a second correspondence between axial position and reference light intensity. The reference light intensity is calculated from the calibrated color component values.

[0014] The optical element under test is placed on the three-dimensional displacement stage, and the polarizer and analyzer are kept orthogonal. The axial movement of the polarizer and analyzer is controlled to perform scanning. The first color component value of the optical element under test is acquired when the polarizer and analyzer are synchronously in the initial position, and the second color component value is acquired after synchronous rotation of 45°.

[0015] The first measured light intensity and the second measured light intensity are calculated based on the first color component value and the second color component value, respectively, and then superimposed to obtain the total measured light intensity; the axial position of the measured point on the optical element under test is determined according to the first correspondence, and the reference light intensity of the axial position is obtained according to the second correspondence; the residual stress of the measured point is determined according to the total measured light intensity and the reference light intensity.

[0016] Thirdly, embodiments of the present invention provide an electronic device, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the above-described method for detecting plane polarization residual stress based on spectral confocality.

[0017] Fourthly, embodiments of the present invention provide a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the above-described method for detecting plane polarization residual stress based on spectral confocality.

[0018] The plane polarization residual stress detection device and method based on spectral confocality provided in this invention, by setting up a polarization modulation component and a signal detection component, and utilizing the principle of spectral confocality combined with polarization detection technology, achieves non-contact, high-precision measurement of the residual stress of the optical element under test, solving the problems of easy sample damage and low efficiency of traditional contact measurement.

[0019] Meanwhile, by extracting the intensity component from the multi-channel color component values ​​output by the color sensor and converting the color model, the interference of color changes caused by dispersion on light intensity measurement is effectively eliminated, significantly improving the accuracy of stress calculation.

[0020] This invention balances detection efficiency and resolution, effectively solving the shortcomings of existing detection technologies such as damage to optical components, high cost, low anti-interference, and low detection efficiency. It is applicable to a variety of optical materials and has good versatility and engineering application value. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic diagram of a plane polarization residual stress detection device based on spectral confocality provided in an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the movement of the three-dimensional displacement stage during the calibration stage provided in an embodiment of the present invention;

[0024] Figure 3 A schematic flowchart of a plane polarization residual stress detection method based on spectral confocality provided in an embodiment of the present invention;

[0025] Figure 4 A schematic diagram of an optical element under test with typical laser damage, provided for an embodiment of the present invention;

[0026] Figure 5 A schematic diagram of the "axial position-wavelength" and "axial position-reference strength" curves provided in an embodiment of the present invention;

[0027] Figure 6 This is a comparative schematic diagram of the two-dimensional residual stress distribution of the optical element under test provided in an embodiment of the present invention.

[0028] Among them, 1. Broadband light source, 2. Collimating lens, 3. Polarizer, 4. First converging lens, 5. First spatial filter, 6. Beam splitter, 7. Dispersive objective lens group, 8. Optical element under test, 9. Three-dimensional displacement stage, 10. Second spatial filter, 11. Second converging lens, 12. Analyzer, 13. Color sensor. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0030] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0031] Figure 1 This is a schematic diagram of a plane polarization residual stress detection device based on spectral confocality provided in an embodiment of the present invention. By combining spectral confocality with polarization detection, high-precision, non-contact measurement of residual stress in optical components is achieved. The device includes a calibration stage and a detection stage; system calibration is required before formal detection.

[0032] Reference Figure 1 As shown, the plane polarization residual stress detection device based on spectral confocality provided in this embodiment of the invention mainly includes an illumination collimation component, a polarization modulation component, a dispersion focusing component, a signal detection component, and a data processing component arranged sequentially along the optical path during the detection stage.

[0033] The illumination collimation assembly generates parallel incident light. In this embodiment, it includes a broadband light source 1 and a collimating lens 2. The broadband light source 1 is used to emit stable continuous-wavelength polychromatic light, which is converted into a parallel beam by the collimating lens 2 as incident light.

[0034] The polarization modulation component modulates the incident light generated by the illumination collimation component into linearly polarized light and performs spatial filtering on the incident light. In this embodiment, the polarization modulation component includes a polarizer 3, a first converging lens 4, and a first spatial filter 5 arranged sequentially. The incident light passes through the polarizer 3, whose transmission direction is fixed, and is modulated into linearly polarized light. Then, the modulated incident light is focused and coupled to the first spatial filter 5 by the first converging lens 4 for spatial filtering. The first spatial filter 5 is an illumination pinhole, which can effectively filter out stray light from the light source and limit the spatial divergence of the beam.

[0035] The dispersive focusing assembly focuses the filtered incident light onto the test point of the optical element 8 under test, causing the test point to reflect the incident light and thus form reflected light carrying stress information. In this embodiment, it includes a beam splitter 6 and a dispersive objective lens group 7. The beam splitter 6 is a beam splitter prism used to reflect the filtered incident light to the dispersive objective lens group 7. The dispersive objective lens group 7 is composed of lenses with different dispersion characteristics, which enables light of different wavelengths to have different focusing positions on the optical axis. It is used to axially disperse the filtered incident light and focus it onto the test point surface of the optical element 8 under test, and Fresnel reflection occurs at the interface to form reflected light. If there is a residual stress field on the surface of the optical element under test, stress birefringence effect occurs when the reflected light passes through the region, and its polarization state will change relative to the incident direction.

[0036] The reflected light returns along the original optical path, passes through the dispersive objective lens group 7 and the beam splitter 6 again, and then enters the signal detection component. In this embodiment, the signal detection component includes a second spatial filter 10, a second converging lens 11, an analyzer 12, and a color sensor 13 arranged sequentially.

[0037] In this path, the reflected light first passes through the second spatial filter 10, which is a probe pinhole. At this time, the first spatial filter 5, the second spatial filter 10 and the measurement surface of the optical element under test 8 form a conjugate filtering structure. Its core function is to implement highly selective spatial filtering, that is, only the reflected light focused on the surface of the optical element under test 8 is allowed to pass through, while the scattered light from inside the optical element under test 8 and the background stray light from the non-focusing plane are effectively blocked.

[0038] Subsequently, the filtered reflected light is focused and coupled to an analyzer 12 by a second converging lens 11. The transmission direction of the analyzer 12 is orthogonal to the transmission direction of the polarizer 3. According to the principle of polarization optics, when there is no residual stress, the reflected light maintains its original polarization state, and the analyzer 12 blocks the reflected light from passing through. When residual stress exists, the analyzer 12 allows some of the reflected light, whose polarization state has rotated due to stress birefringence, to pass through. This portion of the reflected light can be received by the color sensor 13. Finally, the reflected light is received by the color sensor 13, which outputs the multi-channel color component values ​​of the reflected light, including red channel values, green channel values, and blue channel values ​​(i.e., R, G, B values).

[0039] For example, the polarizer and analyzer in this embodiment are linear polarizers, which are composed of two N-BK7 optical glass substrates and a linear polarizing film in the middle, with an extinction ratio of 5000:1.

[0040] The data processing component includes the HSI color model, which orthogonally decomposes the spectral signal into three independent and non-interfering feature variables: hue, saturation, and intensity. Hue (H) directly reflects the dominant wavelength information or color category of the spectrum, saturation (S) characterizes the purity of the color, i.e., the narrowness of the spectral bandwidth, while intensity (I) directly characterizes the intensity information of the image. The HSI color model is used to convert the acquired color component values ​​to the HSI color space, and the intensity component (I component) is independently extracted as the measured light intensity. Finally, the residual stress at the measured point on the optical element under test is calculated based on this measured light intensity. The HSI color model used in this embodiment can separate the intensity information (I component) from the color information (H and S components). Because there is a non-linear relationship between RGB values ​​and wavelength, it is necessary to convert the RGB color model to the HSI color model before realizing its correspondence with wavelength.

[0041] In practical applications, data processing components can be selected from electronic devices with information processing capabilities, such as computers.

[0042] In a preferred embodiment, the analyzer 12 and the polarizer 3 are respectively connected to a rotary drive mechanism for driving them to rotate to change the transmission vibration direction.

[0043] To obtain complete light intensity information, after acquiring the color component values ​​of the optical element under test when the polarizer and analyzer are synchronously in their initial positions, the polarizer 3 and analyzer 12 are rotated 45° synchronously via a rotary drive mechanism before acquiring their color component values ​​again. During this process, the polarizer 3 and analyzer 12 must remain orthogonal at all times to ensure the highest signal-to-noise ratio.

[0044] According to the principles of photoelasticity, stress-induced birefringence causes the reflected light intensity to vary periodically with the polarization angle. The initial position provides a reference light intensity, while the 45° position is at the point of highest sensitivity for birefringence modulation, maximizing the reflection of stress-induced phase delay information. By acquiring light intensity data at these two specific angles and superimposing them, the total light intensity data is obtained, from which the data processing component can calculate the residual stress value at the measured point. Simultaneously, synchronous rotation ensures that the device remains in an orthogonal polarization state, effectively suppressing background stray light and improving the signal-to-noise ratio of the detection.

[0045] For example, the rotary drive mechanism can be a method in which one motor drives two gears, or two motors are linked together, to ensure that the deflector rotates 45° and the detector also rotates 45°.

[0046] In a preferred embodiment, the device further includes a displacement assembly comprising a high-precision three-dimensional displacement stage 9. The three-dimensional displacement stage 9 carries a standard optical element during the calibration phase and a test optical element 8 during the testing phase. It can perform a bow-shaped scan on either the standard optical element or the test optical element 8, enabling point-by-point detection of a local area including the core region of the damage pit, the edge heat-affected zone, and the surrounding substrate.

[0047] It should be noted that, due to limitations of the attached diagram, Figure 1 Only the optical element under test is shown; the standard optical element is not shown. During the calibration phase, the standard optical element is placed on the corresponding three-dimensional displacement stage.

[0048] In a preferred embodiment, the apparatus further includes a calibration component comprising a spectrometer. During the calibration phase, the optical element under test 8 is replaced with a standard optical element, wherein the standard optical element is a non-destructive optical element made of the same material as the optical element under test 8, to ensure that the surface reflectivity during the calibration process is consistent with the actual test conditions.

[0049] During the calibration phase, the axial dispersion characteristics of the system and the reference reflected light intensity distribution of the optical element under test in an undamaged state can be established. The correspondence between axial position and wavelength is established through calibration experiments, clarifying the specific wavelength actually involved in the measurement process, and thus matching the corresponding initial light intensity reference, providing a physical basis for subsequent signal processing.

[0050] Reference Figure 2 As shown, a standard optical element is placed on a three-dimensional displacement stage 9. The stage 9 moves the standard optical element along the Z-axis to initially determine the effective range of the system response and thus determine the sampling interval. A sampling step size is set, and the axial positions are moved sequentially for point-by-point scanning at equal intervals. At each axial position, the wavelength component in a confocal state is reflected from the surface of the standard optical element to form calibration reflected light. This calibration reflected light enters either the spectrometer or the color sensor 13. Specifically, the spectrometer is first placed in the optical path, replacing the color sensor 13, to receive the calibration reflected light, thereby collecting wavelength data of the calibration reflected light at different axial positions of the standard optical element. Then, the spectrometer is removed from the optical path and reset as the color sensor 13, which receives the calibration reflected light, thereby collecting the calibration color component values ​​of the calibration reflected light.

[0051] For example, the scanning range can be set to a rectangular area of ​​3mm×3mm, the sampling step size can be set, and each sampling point can be measured 10 times and the average value can be taken to improve data stability. Furthermore, the color component value of each measured point can be obtained.

[0052] It should be noted that, due to limitations of the attached diagram, Figure 1The spectrometer is not shown. However, this does not affect the understanding and implementation of this technical solution by those skilled in the art. Those skilled in the art can set up the spectrometer according to the above description and achieve the expected technical effect.

[0053] During the calibration phase, the data processing component receives the aforementioned axial position, wavelength data, and calibration color component values. It then establishes a first correspondence between axial position and wavelength, and a second correspondence between axial position and reference light intensity, wherein the reference light intensity is calculated from the calibration color component values. Preferably, the first and second correspondences can be presented in tabular or graphical form for easy reference.

[0054] During the detection phase, the data processing component determines the axial position of the measured point according to the first correspondence, obtains the reference light intensity of the axial position according to the second correspondence, and determines the residual stress of the measured point according to the total measured light intensity and the reference light intensity.

[0055] In this embodiment, to achieve high-precision residual stress measurement, the device employs a dual-parameter decoupled detection strategy. Specifically, during the calibration stage, a high-resolution spectrometer is used to acquire the precise dispersion curve of the dispersive lens group, thus establishing a first correspondence between "axial displacement and wavelength," overcoming the limitation of color sensors not being able to directly acquire wavelength information. Simultaneously, the color sensor receives the same reflected light, acquiring the corresponding color component value. From this color component value, the corresponding reference light intensity is obtained, thereby establishing a second correspondence between "axial position and reference light intensity."

[0056] During the measurement phase, the system switches to a color sensor (such as an RGB sensor). Based on the correspondence established during the calibration phase, the data processing unit analyzes the R, G, and B values ​​output by the color sensor to quickly inversely determine the current focal position and polarization state change, thereby calculating the residual stress.

[0057] This configuration ensures both measurement accuracy (derived from spectrometer calibration) and real-time detection (derived from the color sensor).

[0058] In summary, the detection device provided by the embodiments of the present invention adopts non-contact detection, which balances detection efficiency and resolution, and effectively solves the defects of existing detection technologies such as damage to optical components, high cost, low anti-interference ability and low detection efficiency. It is applicable to a variety of optical materials and has good versatility and engineering application value.

[0059] Furthermore, referring to Figure 3 As shown, this embodiment of the invention provides a method for detecting plane polarization residual stress based on spectral confocality, which is implemented based on the detection device described in any of the foregoing embodiments. The method mainly includes the following steps:

[0060] Step 301: Place the standard optical element on a three-dimensional displacement stage and control its axial movement to perform scanning; collect the calibrated color component values ​​of the color sensor and the wavelength data of the spectrometer respectively, and establish a first correspondence between the axial position and the wavelength, and a second correspondence between the axial position and the reference light intensity; wherein, the reference light intensity is calculated from the calibrated color component values.

[0061] In this step, the detection device described in the foregoing embodiments needs to be calibrated before formal testing.

[0062] A standard optical element is placed on a three-dimensional displacement stage, which is then controlled to move the standard optical element along the Z-axis. After setting the sampling step size, the axial positions are moved sequentially for point-by-point scanning at equal intervals. At each axial position, the calibration reflected light generated by the reflection from the surface of the standard optical element enters the spectrometer or color sensor at the rear end. At this time, the spectrometer collects the wavelength data of the calibration reflected light from the standard optical element at different axial positions, while the color sensor collects the calibration color component values ​​of the corresponding calibration reflected light.

[0063] The data processing component records the received spectral wavelengths at different axial positions Z. And establish the axial position Z and wavelength The first correspondence is established. Simultaneously, the data processing component records the calibrated color component values ​​of the standard optical element at different axial positions Z, and calculates the reference light intensity from these calibrated color component values. And establish the axial position Z and the reference light intensity The second correspondence. Based on the aforementioned operations, the system calibration is completed.

[0064] In this embodiment, the optical element under test exhibits typical laser-induced damage stress. High-purity double-sided polished fused silica disc glass was selected as the substrate material, with a sample diameter of 25.4 mm and a thickness of 2 mm. During fabrication, a 10.6 μm CO2 laser was used as the heat source. After being focused by a focusing lens, the laser beam was incident perpendicularly on the sample surface in a Gaussian beam mode, ultimately forming a significant permanent residual stress field around the damage pit. The damage pit has a diameter of 549.597 μm and a depth of 5.969 μm. See details below. Figure 4 As shown.

[0065] The standard optical element is made of the same non-destructive fused silica glass as the optical element under test, to ensure that the surface reflectivity during the calibration process is consistent with the actual test conditions.

[0066] Simultaneously, based on the aforementioned standard optical elements, a first correspondence between axial position and wavelength, and a second correspondence between axial position and reference light intensity were established. Finally, two sets of curves were plotted: "axial position - wavelength" and "axial position - reference intensity," as detailed below. Figure 5 As shown.

[0067] Step 302: Place the optical element under test on a three-dimensional displacement stage, keep the polarizer and analyzer orthogonal, and control their axial movement to scan; collect the first color component value of the optical element under test when the polarizer and analyzer are synchronously in the initial position, and the second color component value after synchronous rotation of 45°.

[0068] In this step, during the formal testing, the optical element under test is placed on a three-dimensional displacement stage, keeping the polarizer and analyzer orthogonal. The three-dimensional displacement stage is then controlled to move the optical element under test along the Z-axis. After setting the sampling step size, the axial positions are moved sequentially for point-by-point scanning at equal intervals. At each axial position, the reflected light from the surface of the optical element under test enters the color sensor at the rear.

[0069] The polarizer and analyzer are controlled to be in the initial orthogonal position (0°), and the first color component value of the optical element under test at the initial position is acquired by the color sensor; then, the polarizer and analyzer are controlled to rotate synchronously by 45°, and the second color component value is acquired.

[0070] Step 303: Calculate the first measured light intensity and the second measured light intensity according to the first color component value and the second color component value respectively, and superimpose them to obtain the total measured light intensity; determine the axial position of the measured point on the optical element under test according to the first correspondence relationship, and obtain the reference light intensity of the axial position according to the second correspondence relationship; determine the residual stress of the measured point according to the total measured light intensity and the reference light intensity.

[0071] In this step, the collected first and second color component values ​​are converted using a data processing component, and the first and second measured light intensities are extracted independently. Adding the two measurement results together yields the total measured light intensity at the measured point. .

[0072] Furthermore, the axial position of the measured point on the optical element under test is determined according to the first correspondence, and the reference light intensity of the axial position is obtained according to the second correspondence. Based on the total measured light intensity and the reference light intensity, the residual stress at the measured point is further calculated using the residual stress intensity characterization formula.

[0073] In the application of spectral confocal residual stress detection, the residual stress on the surface of the optical element material under test induces optical anisotropy through photoelastic effect, which changes the polarization transmission characteristics of incident light and interface reflection behavior, ultimately causing the intensity of reflected light emitted from the orthogonal polarization detection path to change regularly. Thus, the collected light intensity signal is a comprehensive result of the stress field modulating the amplitude of polarized light.

[0074] Specifically, the device uses continuous-wavelength polychromatic light, which is collimated and modulated by a polarizer to form a linearly polarized beam with a defined vibration direction. This beam is then incident perpendicularly onto the surface of the optical element under test, which has residual stress. Assume the amplitude of the incident light is... The angle between its vibration direction and the direction of the first principal stress inside the material of the optical element under test is . According to the theory of stress-induced birefringence, when a light vector enters an anisotropic medium, it undergoes intrinsic decomposition along two orthogonal principal stress directions, forming two parallel principal stress directions in the same plane. and The two independent vibrational components can be expressed as:

[0075]

[0076]

[0077] in, , , and Two orthogonal principal stress directions and The corresponding principal refractive index, Where is the wavelength of the incident light. and It is a complex exponential phase factor.

[0078] According to Fresnel's law of reflection, light travels through air (refractive index 1000) at a refractive index of 1000. When an optical medium is incident normally at its interface, the amplitude reflection coefficient is determined by the difference in refractive index between the media on both sides of the interface. For a stress-induced birefringent medium, the principal refractive indices corresponding to the two principal stress directions are respectively... and Therefore, the amplitude reflection coefficient along the two principal axes and They are defined as follows:

[0079]

[0080]

[0081] This set of equations reveals the core modulation mechanism of the stress field on the reflected light signal: the difference in principal stress directly leads to the splitting of the principal refractive index, which in turn causes an asymmetric difference in the reflection efficiency of the two orthogonal polarization components at the interface.

[0082] After reflection from the interface, the light wave experiences half-wave loss due to the abrupt change in the medium's wave impedance and amplitude attenuation under the influence of its respective reflection coefficient. At this point, the two components of the reflected light field, carrying information about the principal refractive index difference on the surface of the optical element under test, return along the original path. The polarization state of the reflected light has fundamentally changed relative to the incident light; this change stems from the asymmetric distortion of the reflection amplitude ratio caused by stress anisotropy at the interface. The final expressions for the two orthogonal components of the reflected light field are:

[0083]

[0084]

[0085] The physical model described above shows that after reflection from the surface of a stressed medium, the polarization state of the reflected light undergoes a fundamental change relative to the incident light. This change originates from the variation in the reflection amplitude ratio caused by stress anisotropy at the interface. This physical mechanism, in which the stress field modulates the amplitude of the reflected light through refractive index anisotropy, constitutes the core theoretical basis for inverting residual stress using the intensity of reflected light.

[0086] The reflected light returns along its original path and enters the analyzer, which is orthogonal to the polarization direction of the polarizer. Only the vibration component aligned with the analyzer's transmission axis can pass through, thus enabling the selection and detection of the stress modulation signal. Therefore, the combined vibration of the transmitted light wave after passing through the analyzer can be expressed as:

[0087]

[0088] Since the device only involves interface reflection, the phase term... It can be considered close to zero, and the difference in reflection coefficient is small, so we can approximate it as... Then the transmitted light intensity can be simplified as:

[0089]

[0090] The initial illumination intensity, The initial refractive index is denoted as .

[0091] exist or hour, This means that the reflected light passing through the analyzer undergoes extinction, and on the optical element under test, all points where the principal stress direction is parallel to the polarization direction of the analyzer appear as dark spots. To obtain the full intensity distribution at that point, the polarizer and analyzer need to be rotated synchronously by 45°.

[0092] After rotating 45°, when the linearly polarized light passing through the polarizer illuminates the optical element under test, the two vibration components can be expressed as:

[0093]

[0094]

[0095] After reflection and orthogonal polarization, the intensity of the reflected light can be expressed as:

[0096]

[0097] By superimposing the two measurements, the azimuth angle can be eliminated. The effect of stress is considered to obtain the total reflected light intensity, which is only related to stress, i.e., the total measured light intensity at the measured point on the optical element under test.

[0098]

[0099] According to the law of stress optics, Finally, the intensity characterization formulas for total measured light and residual stress are established:

[0100]

[0101] In practical measurements, it is difficult to directly obtain the absolute incident light intensity at the focal point. Therefore, in this embodiment, the reflection intensity of the undamaged surface of a standard optical element under parallel polarization is used. As a calibration reference. According to the Fresnel reflection formula, its relationship with the initial incident light intensity is: Substituting this into the above equation, the mapping relationship between the actual measurement and the stress can be expressed as:

[0102]

[0103] in, Indicates the refractive index of air. This represents the initial refractive index of the optical element under test. This represents the photoelastic coefficient of the optical element under test. To obtain the reference light intensity at the same axial position for calibration, It represents the total measured light intensity at the measured point on the optical element under test.

[0104] Figure 6This is a comparative schematic diagram of the two-dimensional residual stress distribution of the optical element under test. The left side of the figure is a schematic diagram of the stress distribution after being superimposed and inverted by multi-angle measurements of this device, while the right side is a transmission stress distribution diagram of the optical element under test collected by a commercial stress meter.

[0105] In this embodiment, due to the strictly complementary spatial distribution of the 0° and 45° measurement data, the extinction region caused by angle modulation is effectively filled after simple numerical accumulation, thus restoring the continuous and closed signal morphology of the damaged region. The total measured light intensity after superposition is calculated and normalized to obtain the two-dimensional residual stress distribution of the laser-damaged region on the optical element under test. Commercial stress meters measure the stress response after integration along the thickness direction of the optical element under test. Considering that the optical element under test is a fused silica disc with a thickness of only 2 mm, its thickness is relatively small compared to its 25.4 mm diameter, the transmission integration result can still reflect the planar stress distribution characteristics of the laser-damaged region to a certain extent. Therefore, normalizing the two measurement results allows for a direct comparison of the stress concentration location, overall distribution morphology, and one-dimensional profile variation trend.

[0106] In summary, the plane polarization residual stress detection device and method based on spectral confocality provided in this invention have the following technical effects:

[0107] (1) Achieve high-precision non-contact stress detection

[0108] This technical solution employs the principle of spectral confocality, generating axial dispersion through a beam-splitting element and a dispersive objective lens group, enabling precise determination of the axial position (i.e., focal plane) of the test point. Combined with a polarization modulation component and a signal detection component, it utilizes changes in the polarization characteristics of light to reflect the stress birefringence effect on the material surface. This composite technique of "spectral positioning + polarization analysis" achieves high-precision, non-contact, and non-destructive testing of residual stress on the surface and subsurface of optical components at the microscopic scale.

[0109] (2) Effectively eliminate environmental and system noise interference

[0110] By establishing a mapping relationship between "axial position - wavelength - reference light intensity" through calibration components (spectrometer), the interference of light source intensity fluctuations, detector sensitivity differences, and ambient stray light on the measurement results is effectively eliminated. Simultaneously, by extracting the intensity component (I component) using the HSI color model, hue and saturation interference unrelated to light intensity in the RGB color information can be removed, further improving the stability and accuracy of light intensity measurement.

[0111] (3) Improve the spatial resolution and sensitivity of detection

[0112] This technical solution employs a spatial filter (pinhole) in conjunction with a converging lens to achieve high-resolution detection in a confocal optical path, effectively suppressing defocused background signals and improving the axial and lateral resolution of the device. Furthermore, by synchronously rotating the polarizer and analyzer (e.g., dual-angle scanning at 0° and 45°) and superimposing and calculating the reflected light intensity under different polarization states, it can sensitively capture subtle changes in birefringence signals caused by stress, significantly improving the detection sensitivity for minute residual stresses.

[0113] (4) Balancing detection efficiency and versatility

[0114] Compared to traditional point-scanning stress meters, this technical solution, based on the combination of a color sensor (area array detector) and a three-dimensional displacement stage, enables rapid surface scanning of the optical element under test. The data processing component calculates the stress value in real time according to the pre-stored calibration mapping relationship, significantly improving the detection efficiency. Furthermore, the device has a compact structure and, by changing the dispersive objective lens group with different parameters, can adapt to the stress detection needs of various optical elements with different refractive indices and thicknesses, demonstrating strong versatility.

[0115] Based on the same inventive concept, embodiments of the present invention also provide an electronic device, which mainly includes a processor and a memory, wherein a computer program is stored in the memory. When the processor executes the computer program, it implements the steps described in any of the embodiments of the above-described plane polarization residual stress detection method based on spectral confocality.

[0116] This invention also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps described in any of the embodiments of the above-described plane polarization residual stress detection method based on spectral confocality.

[0117] Optionally, in this embodiment, the storage medium may be located in any computer terminal in a group of computer terminals in a computer network, or in any mobile terminal in a group of mobile terminals.

[0118] In the above embodiments of the present invention, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0119] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A plane polarization residual stress detection device based on spectral confocality, characterized in that, Including those arranged sequentially along the optical path: An illumination collimation assembly for producing parallel incident light; A polarization modulation component is used to modulate the incident light into linearly polarized light and to perform spatial filtering on the incident light; A dispersive focusing assembly includes a beam splitter and a dispersive objective lens group. The beam splitter is used to reflect filtered incident light to the dispersive objective lens group, and the dispersive objective lens group is used to disperse the filtered incident light axially and focus it on the test point of the optical element under test. A signal detection component is used to receive reflected light that has been reflected by the measured point and then passed through the beam splitter again; It includes a color sensor that outputs multi-channel color component values ​​of the reflected light; A data processing component is used to calculate the measured light intensity based on the color component values, and to calculate the residual stress at the measured point based on the measured light intensity.

2. The apparatus according to claim 1, characterized in that, The polarization modulation assembly includes a polarizer, a first converging lens, and a first spatial filter arranged in sequence. The incident light is modulated into linearly polarized light by the polarizer and focused and coupled to the first spatial filter by the first converging lens for spatial filtering.

3. The apparatus according to claim 2, characterized in that, The signal detection component further includes a second spatial filter, a second converging lens, and a polarizer arranged in sequence. The reflected light passes through the second spatial filter, the second converging lens, and the polarizer in sequence and is then received by the color sensor. The transmission direction of the polarizer and the transmission direction of the polarizer are configured to be orthogonal to each other.

4. The apparatus according to claim 3, characterized in that, The analyzer and the polarizer are respectively connected to a rotary drive mechanism for driving them to rotate to change the transmission vibration direction.

5. The apparatus according to claim 1, characterized in that, It also includes a displacement component, which includes a three-dimensional displacement stage; The three-dimensional displacement stage is used to carry standard optical elements during the calibration stage and to carry optical elements under test during the testing stage.

6. The apparatus according to claim 1, characterized in that, It also includes a calibration component, which includes a spectrometer; The spectrometer is used to collect wavelength data of calibration reflected light formed by standard optical elements at different axial positions during the calibration phase; the color sensor is used to collect calibration color component values ​​of the calibration reflected light during the calibration phase. The data processing component is used to establish a first correspondence between axial position and wavelength, and a second correspondence between axial position and reference light intensity during the calibration phase; wherein, the reference light intensity is calculated from the calibration color component value; The data processing component is further configured to determine the axial position of the measured point according to the first correspondence during the detection stage, obtain the reference light intensity of the axial position according to the second correspondence, and determine the residual stress of the measured point according to the total measured light intensity and the reference light intensity.

7. A method for detecting plane polarization residual stress based on spectral confocality, characterized in that, include: A standard optical element is placed on a three-dimensional displacement stage, and its axial movement is controlled to perform scanning. The calibrated color component values ​​of the color sensor and the wavelength data of the spectrometer are collected respectively to establish a first correspondence between axial position and wavelength, and a second correspondence between axial position and reference light intensity; wherein the reference light intensity is calculated from the calibrated color component values. The optical element under test is placed on the three-dimensional displacement stage, and the polarizer and analyzer are kept orthogonal. The axial movement of the polarizer and analyzer is controlled to perform scanning. The first color component value of the optical element under test is acquired when the polarizer and analyzer are synchronously in the initial position, and the second color component value is acquired after synchronous rotation of 45°. The first measured light intensity and the second measured light intensity are calculated based on the first color component value and the second color component value, respectively, and then superimposed to obtain the total measured light intensity; the axial position of the measured point on the optical element under test is determined according to the first correspondence, and the reference light intensity of the axial position is obtained according to the second correspondence; The residual stress at the measured point is determined based on the total measured light intensity and the reference light intensity.

8. The method according to claim 7, characterized in that, The residual stress at the measured point is calculated using the following formula: in, Indicates the refractive index of air. This represents the initial refractive index of the optical element under test. This represents the photoelastic coefficient of the optical element under test. This represents the total measured light intensity at the measured point on the optical element under test. The reference light intensity is obtained at the same axial position through calibration.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory, characterized in that, When the processor executes the computer program, it implements the plane polarization residual stress detection method based on spectral confocality as described in claim 7 or 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the plane polarization residual stress detection method based on spectral confocality as described in claim 7 or 8.

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