A system for measuring an angle of incidence and a method of measuring the same

Abstract

This application discloses a system and method for measuring the incident angle, belonging to the field of optical measurement technology. The measurement system includes an incident light modulation component, a signal processing component, and an optical transformation and detection component. The optical transformation and detection component includes an error amplification unit, a Fourier lens, and a two-dimensional PSD detection unit. The reflected light beam from the front surface is sequentially amplified by the error amplification unit to amplify the angle deviation, and then converted into a positional displacement on the rear focal plane by the Fourier lens. The two-dimensional PSD detection unit located on the focal plane receives the light spot and outputs a corresponding electrical signal. The deviation value of the incident angle on the two-dimensional plane can be calculated in real time using the electrical signal. This application effectively solves the technical problem of incident angle variation caused by manufacturing errors on the surface of glass protective windows, affecting the accuracy of triangulation measurement. It achieves non-contact, high-sensitivity, and high-dynamic-response real-time measurement and compensation of the incident angle, significantly improving the overall measurement accuracy and adaptability of the system.

Description

Technical Field

[0001] This application relates to the field of optical measurement technology, and more specifically to a system and method for measuring the incident angle. Background Technology

[0002] Laser triangulation is a non-contact 3D measurement technique based on geometric triangulation. Its core system consists of a laser emitter, a projection optics system, an image sensor, and a camera. Oblique laser triangulation is an important variant of this technique, the key difference being the projection method of the laser beam. In the classic direct (or orthogonal) layout, the laser beam is usually incident approximately perpendicular to the surface being measured. In the oblique layout, the laser beam is projected onto the surface at a large angle, significantly deviating from the normal direction. The reflected or scattered light is focused by a lens and projected onto the camera's imaging sensor. Similarly, changes in surface height cause displacement of the laser spot position on the imaging surface; the normal displacement or depth value of the surface can be calculated using the established triangular geometric model.

[0003] While oblique laser triangulation excels in measuring micro-displacements and micro-vibrations, the components under test are often protected by glass or other materials. When protected by glass, the laser beam must first strike the glass surface, pass through it, and then strike the surface of the component under test. Refraction occurs during this process, leading to distance errors depending on whether the light beam is inside or outside the glass. Furthermore, manufacturing defects in the glass surface cause the actual normal to deviate slightly from the theoretical normal, resulting in a small angular error between the actual and theoretical incident angles. This angular error affects the distance error and causes a significant displacement of the laser spot on the imaging surface, thus amplifying the measurement error of the incident angle.

[0004] Therefore, there is an urgent need for a measurement system and method for the incident angle to solve the technical problem of inaccurate measurement of the incident angle in the triangulation method for oblique laser beams in the existing technology. Summary of the Invention

[0005] The purpose of this application is to provide a system and method for measuring the incident angle, which can solve at least one of the technical problems mentioned above. The specific solution is as follows:

[0006] According to a specific embodiment of this application, this application provides a measurement system for incident angle, including an incident light modulation component and a signal processing component, and further including an optical transformation and detection component;

[0007] The incident light modulation component is used to generate a modulated laser beam, which illuminates the front surface of the glass window under test at a preset reference incident angle.

[0008] The optical transformation and detection component is used to receive the reflected light beam from the front surface, optically amplify and transform the reflection angle deviation signal carried by the reflected light beam, and convert it into an electrical signal characterizing the position of the light spot.

[0009] The signal processing component is used to acquire and process the electrical signal, calculate the deviation value of the reference incident angle, and obtain the actual incident angle.

[0010] The incident light modulation component includes, in sequence along the laser output light path: a laser source, a polarizer, a half-wave plate, an attenuator, and an aperture; the beam emitted from the laser source is linearly polarized by the polarizer, its polarization state is adjusted by the half-wave plate, its power is attenuated by the attenuator, and stray light is filtered out by the aperture to form the modulated laser beam;

[0011] The optical transformation and detection assembly includes, in sequence along the reflected light path, an error amplification unit, a Fourier lens, and a two-dimensional PSD detection unit. The reflected light beam from the front surface is amplified by the error amplification unit to amplify the angle deviation, and the Fourier lens converts the angle change into a position displacement on the rear focal plane. The two-dimensional PSD detection unit located on the focal plane receives the light spot and outputs the corresponding electrical signal.

[0012] Furthermore, the error amplification unit includes: a first reflector and a second reflector;

[0013] The first reflector and the second reflector are arranged opposite to each other;

[0014] The reflected beam is incident on one end of the first reflector. After incident, it is reflected at least once by the second reflector between the first and second reflectors, and then exits through the other end of the second reflector, thereby amplifying the angular deviation.

[0015] Furthermore, the first reflector is arranged parallel to the horizontal reference.

[0016] The reflecting surface of the second reflector, which is opposite to the first reflector, is set at a preset angle to the horizontal reference plane; the non-reflecting surface of the second reflector is set parallel to the horizontal reference plane.

[0017] Furthermore, the reflecting surface of the second reflector is rotated by the preset angle about a Y-axis parallel to the incident plane.

[0018] Furthermore, both the first and second reflectors have a reflectivity greater than 99% and are made of the same material.

[0019] Furthermore, the range of the reference incident angle is 30°-45°.

[0020] This application also provides a method for measuring the incident angle, including:

[0021] The light is incident on the surface of the standard part at a preset reference incident angle, the optical path parameters of the measurement system are calibrated, and the initial imaging position coordinates of the initial spot on the two-dimensional PSD detection unit are recorded at this time.

[0022] The light beam is incident on the front surface of the glass window to be tested at the reference incident angle, the reflected light beam is received from the front surface, the reflected light beam is optically magnified and transformed, and converted into an electrical signal characterizing the position of the light spot.

[0023] The electrical signal is collected and processed. Based on the change in the imaging position of the reflected beam on the two-dimensional PSD detection unit, the incident angle deviation of the incident light relative to the front surface is quantitatively calculated to obtain the actual incident angle.

[0024] Further, the quantitative calculation of the incident angle deviation of the incident light relative to the front surface includes:

[0025] Acquire the real-time imaging position coordinates of the real-time light spot on the two-dimensional PSD detection unit during the measurement process;

[0026] Based on the initial imaging position coordinates and the real-time imaging position coordinates, calculate the positional changes of the light spot in the X-axis and Y-axis directions;

[0027] Based on the position change and the optical path parameters calibrated by the measurement system, a correspondence between the position change of the light spot and the incident angle deviation is established, and the deviation values ​​of the incident angle in the X-axis direction and the Y-axis direction are obtained.

[0028] Furthermore, the imaging position coordinates on the two-dimensional PSD detection unit are:

[0029]

[0030]

[0031] in, , These represent the effective photosensitive surface size of the two-dimensional PSD detection unit in the X-axis and Y-axis directions, respectively. , , , These represent the output signals of the corresponding electrodes of the two-dimensional PSD detection unit.

[0032] Furthermore, the actual incident angle includes:

[0033]

[0034]

[0035] in, , These represent the components of the actual incident angle in the X-axis and Y-axis directions, respectively. Indicates the reference angle of incidence; , These represent the deviations of the incident angle in the X-axis and Y-axis directions, respectively.

[0036] Compared with the prior art, the above-described solutions of this application have at least the following beneficial effects:

[0037] 1. This application relates to a measurement system and method for incident angle. An error amplification unit optically amplifies the angular deviation of the reflected light, and an optical transformation unit converts the angular change into a spot displacement on the focal plane. In other words, by introducing an error amplification unit and a PSD feedback system, the system utilizes the reflected light from the glass surface to precisely measure minute deviations in the incident angle, thus solving the accuracy problem of the oblique laser triangulation method when measuring objects with glass windows. It does not require additional complex interference devices, has a simple structure, and strong anti-interference capability.

[0038] 2. This application relates to a measurement system and method for incident angle. Through the technical solution of the first and second reflectors in the error amplification unit, the reflected light beam is reflected multiple times between the two mirrors. Each time it is reflected on the second reflector, the light deflection angle caused by the small deviation of the incident angle is accumulated and amplified. The measurement system can detect the incident angle change at the sub-micro-radian level, which greatly enhances the ability to detect small tilt angles or topographic errors on the glass surface.

[0039] 3. This application relates to a measurement system and method for incident angle. By folding the optical path, the light beam is reflected multiple times between two planes, and the total optical path is significantly shortened. This not only achieves a higher angle magnification effect and greatly reduces the space occupied by the optical system, but also reduces the sensitivity to air turbulence, temperature gradient and mechanical vibration. This improves the stability and reliability of the system in non-laboratory environments, which is conducive to achieving long-term, dynamic high-precision measurement. It is also more suitable for space-constrained industrial sites or portable measurement equipment. Attached Figure Description

[0040] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings:

[0041] Figure 1 This is a schematic diagram of the oblique laser triangulation method provided in an embodiment of this application.

[0042] Figure 2 This is a schematic diagram of the structure of an incident angle measurement system provided in an embodiment of this application.

[0043] Figure 3 This is a first schematic diagram illustrating the relationship between the deviation between the reflection angle and the incident angle, provided in an embodiment of this application.

[0044] Figure 4 This is a second schematic diagram illustrating the relationship between the deviation between the reflection angle and the incident angle, provided in an embodiment of this application.

[0045] Figure 5 This is a schematic diagram of the structure of an error amplification unit of an incident angle measurement system provided in an embodiment of this application.

[0046] Figure 6 This is a schematic diagram of the light spot on the two-dimensional PSD detection unit of an incident angle measurement system provided in an embodiment of this application.

[0047] Explanation of reference numerals in the attached figures:

[0048] Laser source 1, polarizer 2, half-wave plate 3, attenuator 4, aperture 5, front surface 6, error amplification unit 7, first reflector 701, second reflector 702, Fourier lens 8, four-quadrant PSD detector 9, signal processing component 10. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0050] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or device. Without further limitation, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the product or device that includes that element.

[0051] The embodiments of this application are described in detail below with reference to the accompanying drawings.

[0052] Example 1:

[0053] In the application of oblique laser triangulation, the incident angle is a core geometric parameter. By adjusting the incident angle, the imaging position of the reflected light spot on the receiving detector can be controlled, and the displacement or distance of the object can be calculated using the proportional relationship of similar triangles. In oblique laser triangulation, the device under test is protected by a glass window; therefore, during actual measurement, the laser beam first enters the front surface of the glass, passes through the front surface, and then enters the measured surface of the device under test. Figure 1 As shown, Indicates the angle of incidence of the laser beam. The solid line represents the beam without a glass window, and the dashed line represents the beam with a glass window. Refraction occurs as the beam passes through the glass window, resulting in the appearance of beams with and without a glass window. The distance error, and the manufacturing deviation of the glass window, further affect the incident angle of the laser beam, causing deviations. The figure also illustrates the root cause of the problem: the actual optical path deviates from the ideal optical path due to the increased glass window and its surface topography errors, resulting in a slight deviation in the actual incident angle.

[0054] The technical solution of this application accurately measures the minute deviation between the incident angle caused by the surface topography error of the glass protective cover and its theoretical preset value, that is, the reference incident angle. It is used to improve the measurement accuracy of triangulation on objects inside glass.

[0055] This application provides a system for measuring the incident angle, including an incident light modulation component, a signal processing component 10, and an optical transformation and detection component. The incident light modulation component generates a modulated laser beam, which illuminates the front surface 6 of a glass window at a preset reference incident angle. The optical transformation and detection component receives the reflected light beam from the front surface 6 of the glass window, optically amplifies and transforms the reflection angle deviation signal carried by the reflected beam, and converts it into an electrical signal characterizing the position of the light spot. The signal processing component 10 acquires and processes the electrical signal, calculates the deviation value of the reference incident angle, and obtains the actual incident angle.

[0056] like Figure 2 As shown, the incident light modulation assembly, along the laser output light path, sequentially includes: a laser source 1, a polarizer 2, a half-wave plate 3, an attenuator 4, and an aperture 5. The optical transformation and detection assembly, along the reflected light path, sequentially includes: an error amplification unit 7, a Fourier lens 8, and a two-dimensional PSD detection unit. In this embodiment, the two-dimensional PSD detection unit is a four-quadrant PSD detector 9.

[0057] In the technical solution of this application embodiment, the Gaussian beam emitted by the semiconductor laser source 1 with a wavelength of 635nm is first converted into linearly polarized light by a P-polarizer 2 to improve the consistency of the reflected signal. Then, the polarization direction is adjusted to a predetermined angle by a half-wave plate 3 to control the surface reflection intensity and suppress parasitic reflection contrast. Subsequently, an attenuator 4 attenuates the laser power to the linear operating region, reducing saturation and thermal drift. Finally, an aperture 5 filters out stray light and higher-order mode components from the periphery of the beam, limiting the spatial path of stray light and residual double-surface reflections, thereby forming a modulated laser beam with stable power, controllable polarization state, and excellent beam quality. The modulated laser beam irradiates the front surface 6 of the glass window at a preset reference incident angle. After being reflected by the front surface 6 of the glass window, the reflected light beam passes sequentially through the first reflecting mirror 701 and the second reflecting mirror 702 in the error amplification unit 7. First, it is incident on the first reflecting mirror 701 and reflected. Then, it is incident at a specific angle on the tilted second reflecting mirror 702. After at least one reflection between the two mirrors, it exits, amplifying the angular deviation. This process amplifies the change in reflection angle caused by the slight deviation of the normal to the glass surface. Optical magnification results in a larger change in the exit angle. The magnified beam of light is then incident on a Fourier lens 8 with a focal length of f=100mm. The Fourier lens 8 measures the angular change of the beam. This is linearly converted into a lateral positional displacement on its rear focal plane. In this embodiment, the effective photosensitive surface size of the four-quadrant PSD detector 9 is: = =10mm, the four-quadrant PSD detector 9 is placed at the back focal plane of the Fourier lens 8 to receive the light spot and convert the two-dimensional position coordinates of the center of the light spot into four weak electrical signal outputs in real time.

[0058] like Figure 3 and Figure 4 As shown, the geometric relationship between the surface morphology error and the angle deviation of the glass is explained. The theoretical front surface 6 represents the ideal glass surface, and its normal direction is the theoretical reference. Indicates the reference angle of incidence; Indicates the actual angle of incidence; Indicates the deviation of the angle of incidence; Indicates the theoretical reflection angle; Indicates the actual reflection angle; Indicates the deviation of the reflection angle; Represents the theoretical normal; This represents the actual normal. Actual front surface 6 represents the real surface with manufacturing errors. The laser beam is incident at a reference angle. Irradiation refers to the laser beam illuminating the front surface 6 of the theoretical glass window at a predetermined angle. When surface errors exist, the actual angle of incidence... for The theoretical reflection angle formed by the laser beam on the front surface 6 of the theoretical glass window according to the law of reflection. Because the front surface 6 of the glass window is actually tilted, there is a deviation in the angle of incidence. This causes the direction of the actual reflected light to shift relative to the theoretical direction of the reflected light; this shift angle is _____. Actual reflection angle for According to the law of optical reflection, = The actual reflected light rays pass sequentially through the error amplification unit 7 and the Fourier lens 8 before being received by the four-quadrant PSD detector 9.

[0059] This application provides a preferred technical solution, such as... Figure 5 As shown, the error amplification unit 7 includes: a first reflector 701 and a second reflector 702; the first reflector 701 and the second reflector 702 are arranged opposite to each other; the actual reflected beam is incident on one end of the first reflector 701, and after incident, it is reflected at least once between the first reflector 701 and the second reflector 702, and then exits through the other end of the second reflector 702, thereby amplifying the angular deviation. The first reflector 701 is arranged parallel to the horizontal reference; the reflecting surface of the second reflector 702 opposite to the first reflector 701 is arranged at a preset angle to the horizontal reference plane; the non-reflecting surface of the second reflector 702 is arranged parallel to the horizontal reference plane. The reflecting surface of the second reflector 702 rotates around a Y-axis parallel to the incident plane by a preset angle, the preset angle being... .

[0060] The actual reflected light beam from the front surface 6 of the glass window carries the initial deviation angle. The beam first strikes the first reflecting mirror 701 and is reflected. Then, the beam strikes the reflecting surface of the tilted second reflecting mirror 702 at a certain angle, resulting in the first reflection. After this reflection, the direction of the beam returns to its original position. Based on this, a fixed deflection amount caused by the mirror tilt of the reflecting surface of the second reflecting mirror 702 is added. Afterwards, the beam returns to the first reflecting mirror 701 and is reflected again, undergoing specific multiple reflections between the second reflecting mirror 702 and the first reflecting mirror 701. In this embodiment, the reflected beam undergoes two reflections on the reflecting surface of the second reflecting mirror 702 before exiting through the other end of the second reflecting mirror 702.

[0061] Because the reflecting surface of the second reflecting mirror 702 is tilted According to the law of reflection, each time a beam of light is reflected at a reflecting surface, its exit direction will change by 2° relative to the incident direction. The additional angular change, relative to the horizontal reference. For each reflection of the reflected beam from the second reflecting surface 702, the corresponding reflection angle deviation increases by 2. That is, the deviation value is amplified by a factor of two each time it is reflected on the reflecting surface of the second reflector 702. Therefore, the lengths of the first reflector 701 and the second reflector 702 can be selected according to the factor of the deviation value to be amplified, and this application does not limit this. In the embodiment of this application, when the actual reflected beam is reflected twice on the second reflector 702, a total of 4 A fixed angle offset, the deviation value compared to 4 more The light rays that ultimately enter the Fourier lens 8 undergo a 4-fold change relative to the unmagnified actual reflected light rays. The angle shift. Therefore, the total angular deflection of the beam emitted from error amplification unit 7. A slight deviation from the original There is an amplification relationship between them: By setting appropriate Values ​​that can detect things that are difficult to detect directly. The signal is converted and amplified into an angle signal that is easily measured precisely by the subsequent Fourier lens 8 and the four-quadrant PSD detector 9. This significantly improves system sensitivity.

[0062] This application provides a preferred technical solution where the first reflector 701 and the second reflector 702 both have a reflectivity greater than 99% and are made of the same material. In this embodiment, the first reflector 701 and the second reflector 702 are coated with a film that has a reflectivity higher than 99% at the laser operating wavelength, and can be made of the same substrate material, fused silica, with a matching coefficient of thermal expansion, thereby obtaining the best signal-to-noise ratio and stability.

[0063] In the technical solution of this application embodiment, the error amplification unit 7 consists of a first reflector 701 and a second reflector 702 arranged opposite to each other. The total magnification of the measurement system can be precisely controlled by the high reflectivity two-plane multiple reflection structure and the preset tilt angle of the second reflector 702, realizing high-magnification optical amplification of small angular deviations in a compact space. This allows for flexible matching of different accuracy requirements and space constraints, and solves the contradiction between high sensitivity and miniaturization.

[0064] This application provides a preferred technical solution where the reference incident angle ranges from 30° to 45°. This is based on a comprehensive trade-off between various optical principles, signal quality, and system feasibility. According to the Fresnel reflection formula, the reflectivity of the S-polarization component monotonically increases as the incident angle gradually increases from 0°. For typical optical glass, the reflectivity of the front surface 6 is approximately 5%–10% when the incident angle is in the 30°–45° range. This provides a sufficiently strong and stable starting signal for the detection of the four-quadrant PSD detector 9, while avoiding technical problems such as weak reflected signals and insufficient signal-to-noise ratio when the angle is too small, or weak transmitted light and difficulties in system layout when the angle is too large, although the reflectivity is higher.

[0065] The beam, after having its angular deviation amplified by error amplification unit 7, is incident on the Fourier lens. The distance from the exit point of error amplification unit 7 to the Fourier lens is s. The Fourier lens 8 linearly converts the angular change Δψ of the beam into a lateral displacement on the back focal plane, which is received by the four-quadrant PSD detector 9. The four-quadrant PSD detector 9 is precisely positioned at the back focal plane of the Fourier lens 8 to receive the light spot and convert the two-dimensional position coordinates of the light spot center into four electrical signals in real time: , , , Output. The signal processing component 10 acquires and processes four electrical signals, calculates the deviation value of the reference incident angle, and obtains the actual incident angle.

[0066] In this embodiment, the incident angle measurement system is implemented by a signal processing component 10, which performs high-speed, synchronous acquisition, digitization, buffering, and uploading of the electrical signals output by the two-dimensional PSD detector unit, and the host computer performs real-time calculation of the incident angle deviation. The signal processing component 10 includes a transimpedance amplifier module and a data acquisition module based on a field-programmable gate array (FPGA). A MAX3232 level conversion chip is connected within the FPGA board to ensure that the input current does not burn out the FPGA board. The FPGA board has a USB serial port for communication with the host computer via the RS232 protocol. The transimpedance amplifier converts the four current signals from the four-quadrant PSD detector 9 into four analog voltage signals. , , and The FPGA acquisition module has a built-in analog-to-digital converter (ADC) that synchronously acquires these four voltage channels at a predetermined sampling rate and digitizes them. The FPGA calculates the deviation value of the reference incident angle to obtain the actual incident angle.

[0067] This application provides an incident angle measurement system that, by incorporating an error amplification unit 7 including a first reflector 701 and a second reflector 702, causes the reflected light beam from the front surface 6 of the glass window under test to undergo multiple reflections between the two mirrors, thereby optically amplifying minute incident angle deviations. The amplified beam is then focused by a Fourier lens 8 onto a two-dimensional PSD detection unit for high-precision position sensing, and the incident angle deviation value is calculated in real time by a signal processing component 10. The system improves angle detection sensitivity while effectively reducing the space occupied by the optical system, achieving a balance between high precision and compactness.

[0068] Example 2:

[0069] The technical solution of this application embodiment also provides a method for measuring the incident angle. The measurement method is based on an incident angle measurement system, and the specific steps include:

[0070] S1. The light is incident on the surface of the standard piece at a preset reference incident angle. The optical path parameters of the measurement system are calibrated, and the initial imaging position coordinates of the initial spot on the two-dimensional PSD detection unit are recorded. In this embodiment, the standard piece is a known reference flat glass with extremely high surface accuracy.

[0071] The measurement system is activated, causing laser source 1 to emit a collimated beam with a wavelength of 635nm. After modulation and filtering by polarizer 2, half-wave plate 3, attenuator 4, and aperture 5, the beam forms a modulated laser beam with stable power and controllable polarization. This modulated laser beam is then incident on the surface of the standard part at a preset reference incident angle. The reflected beam from the standard part's surface then passes sequentially through error amplification unit 7 and Fourier lens 8, ultimately forming a clear initial spot on the photosensitive surface of the four-quadrant PSD detector 9. Figure 6 As shown, the initial distance, or initial imaging position coordinate, is defined as the distance between the initial spot position on the four-quadrant PSD detector 9 and the zero point of the four-quadrant PSD detector 9 in the X and Y axes. , Record the amplified output current signals of the four electrodes of the four-quadrant PSD detector 9, respectively along the X-axis. , In the Y-axis direction , The transimpedance amplifier converts the four current signals of the four-quadrant PSD detector 9 into four analog voltage signals, which are denoted as reference voltages, and calculates the initial imaging position coordinates based on the reference voltages.

[0072] In this embodiment of the application, the initial imaging position coordinates are:

[0073]

[0074]

[0075] in, , These represent the effective photosensitive surface size of the two-dimensional PSD detection unit in the X-axis and Y-axis directions, respectively. , , , These represent the output signals of the corresponding electrodes of the two-dimensional PSD detection unit when measuring standard parts.

[0076] S2. Receive the reflected light beam from the front surface 6 of the glass window, perform optical amplification and transformation on the reflected light beam, and convert it into an electrical signal that characterizes the position of the light spot.

[0077] Remove the standard component and place the protective cover of the glass window onto an incident angle measurement system. Maintaining the same reference incident angle as in step S1, the same modulated laser beam is incident on the front surface 6 of the glass window. The beam is reflected from the front surface 6 of the glass window into the subsequent optical path. The reflected beam carries the slight change in reflection angle caused by the deviation of the actual surface normal. After being amplified twice by the error amplification unit 7 on the second reflecting mirror 702, the deviation value is amplified. After amplification, it is incident on the Fourier lens 8 for transformation, forming a real-time light spot on the four-quadrant PSD detector 9. The four-quadrant PSD detector 9 outputs a current in real time, which is converted into a voltage signal characterizing the position of the implemented light spot.

[0078] Similarly, in this embodiment, the real-time imaging position coordinates are:

[0079]

[0080]

[0081] in, , These represent the effective photosensitive surface size of the two-dimensional PSD detection unit in the X-axis and Y-axis directions, respectively. , , , These represent the output signals of the corresponding electrodes of the two-dimensional PSD detection unit when measuring the front surface 6 of the glass window.

[0082] S3. Acquire and process electrical signals. Based on the change in the imaging position of the reflected beam on the two-dimensional PSD detection unit, quantitatively calculate the incident angle deviation of the incident light relative to the front surface 6 of the glass window to obtain the actual incident angle.

[0083] Based on the real-time voltage of the four-quadrant PSD detector 9, the real-time imaging position coordinates (x, y) of the real-time spot during the measurement process are calculated.

[0084] Based on the initial imaging position coordinates and the real-time imaging position coordinates, calculate the positional changes of the light spot in the X-axis and Y-axis directions. The specific expressions are as follows:

[0085]

[0086]

[0087] in, , These represent the changes in position along the X-axis and Y-axis, respectively.

[0088] Based on the position change and the optical path parameters calibrated by the measurement system, the correspondence between the position change of the light spot and the incident angle deviation is established, and the deviation values ​​of the incident angle in the X-axis direction and the Y-axis direction are obtained.

[0089] The four-quadrant PSD detector 9 is positioned at the back focal plane of the Fourier lens 8. The beam emitted from the error amplification unit 7 is deflected upon impact with the Fourier lens 8. The two-dimensional angular deflection of the emitted beam relative to the optical axis of the Fourier lens 8 is... , The deviation values ​​in the X-axis and Y-axis directions are respectively , The expression is:

[0090]

[0091]

[0092] Where s represents the distance from the exit point of the error amplification unit 7 to the Fourier lens; f represents the focal length of the Fourier lens 8.

[0093] Based on the principles of geometric optics, , A relationship is established between the deviation of the actual reflection angle in the X-axis and Y-axis directions. The expression for the deviation of the actual reflection angle is:

[0094]

[0095]

[0096] in, This represents the deviation of the actual reflection angle along the X-axis. This represents the deviation of the actual reflection angle along the Y-axis.

[0097] Since the error amplification unit 7 amplifies the deviation value, based on the geometric optical model determined by the system calibration of this application's technical solution, the positional changes of the light spot in the X-axis and Y-axis directions are calculated as incident angle deviation values, establishing a quantitative relationship between the light spot displacement and the angle deviation, expressed as:

[0098]

[0099]

[0100] in, This indicates the deviation of the incident angle in the X-axis direction; This represents the deviation of the incident angle in the Y-axis direction.

[0101] With the XOZ plane as the reference, the theoretical incident angle has no component in the YOZ direction. The YOZ component originates from the surface error of the front panel of the glass window. Rearranging the above formula, the actual expression for the incident angle is:

[0102]

[0103]

[0104] in, , These represent the components of the actual incident angle in the X-axis and Y-axis directions, respectively.

[0105] This application provides a method for measuring the incident angle, which optically amplifies and electrically calculates minute deviations in the incident angle. The method first measures a standard component using a preset reference incident angle, calibrates the system, and records the initial spot position coordinates on the two-dimensional PSD detection unit to establish a measurement reference. Then, when measuring the glass window under test, the reflected beam from its front surface 6 is received. The reflected beam enters an error amplification unit 7 composed of a first reflecting mirror 701 and a second reflecting mirror 702. The beam undergoes multiple reflections between the two high-reflectivity mirrors, progressively amplifying the minute incident angle deviation. The amplified beam is converged by a Fourier lens 8, forming a spot on the two-dimensional PSD detection unit on its rear focal plane. The PSD linearly converts the two-dimensional position information of the spot into four voltage signals. The signal processing component 10 acquires the voltage signals and, based on the calibrated optical path geometric parameters, calculates the spot displacement in real time using mathematical calculations and an optical model, thereby accurately obtaining the deviation value of the incident angle on the two-dimensional plane. The method of this application combines the optical amplification mechanism with the linear position sensing characteristics of the two-dimensional PSD detection unit, thereby achieving high sensitivity and fast real-time measurement of dynamically changing incident angles.

[0106] This application embodiment verifies the effectiveness of the technical solution through comparative experiments, comparing it with the long-baseline optical lever method in the prior art. In this embodiment, the laser source 1 outputs a continuous laser with a wavelength of 632.8 nm; the reflectivity R of the first reflector 701 and the second reflector 702 is 99%, the distance between them is 0.03 m, and the reflected beam undergoes six reflections between the first reflector 701 and the second reflector 702, with the angular deviation accumulating and amplified with each reflection. The four-quadrant PSD detector 9 has a field of view (FOV) of 12.0 mm and a position resolution of [missing information]. =2.0µm. Sensitivity is based on the minute angular error of the mirror surface 6 of the front surface of the glass window under test. Spot displacement caused by (µrad) Calculation: Long Baseline Optical Leverage Method Technical solutions of the embodiments of this application .

[0107] The specific data is shown in Table 1:

[0108] Table 1 Comparison of Experimental Results

[0109]

[0110] Comparative experiments were conducted to compare the performance of the two methods from multiple dimensions. The results show that the technical solution of this application improves the sensitivity to 6.00 µm / µrad through six reflections, with a minimum measurable angle of 0.33 µrad, which is superior to the 1.00 µm / µrad and 2.00 µrad of the long-baseline optical lever method with a single reflection. This demonstrates that the technical solution of this application has a stronger detection capability for minute angle changes. To achieve the same sensitivity (6 µm / µrad), the long-baseline optical lever method requires extending the optical arm to 1.5 m, while the technical solution of this application, through reflection and folding of the optical path, requires only a system length of 0.35 m, greatly saving space and making it suitable for integrated, portable devices. The total optical path of the technical solution of this application is 0.61 m, lower than the 1.50 m of the long-baseline optical lever method. The shorter optical path reduces the sensitivity to airflow, temperature gradients, and mechanical vibrations, which is beneficial for maintaining measurement stability in non-ideal environments. The technical solution of this application introduces approximately 6.3% optical power loss due to multiple reflections, with a reflectivity of 99%, but still retains 93.7% power, which is sufficient to support the stable operation of the four-quadrant PSD detector 9. Although the long baseline method has lower optical loss, it incurs a greater space cost.

[0111] In summary, the technical solution of this application, through the multiple reflection structure of the error amplification unit 7, achieves multi-level optical amplification of angular deviation within a limited size by realizing multiple reflections between the two mirrors. Combined with the application of geometric optics, it solves the technical problem in oblique laser triangulation where the laser must pass through a glass window to illuminate the measured surface, and the surface manufacturing error of the glass window causes its actual normal to deviate from the theoretical normal, resulting in a slight deviation in the incident angle. Furthermore, it significantly improves the sensitivity and resolution of incident angle detection.

[0112] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems or apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0113] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A system for measuring the incident angle, comprising an incident light modulation component and a signal processing component, characterized in that, It also includes optical transformation and detection components; The incident light modulation component is used to generate a modulated laser beam, which illuminates the front surface of the glass window under test at a preset reference incident angle. The optical transformation and detection component is used to receive the reflected light beam from the front surface, optically amplify and transform the reflection angle deviation signal carried by the reflected light beam, and convert it into an electrical signal characterizing the position of the light spot. The signal processing component is used to acquire and process the electrical signal, calculate the deviation value of the reference incident angle, and obtain the actual incident angle. The incident light modulation component includes, in sequence along the laser output light path: a laser source, a polarizer, a half-wave plate, an attenuator, and an aperture; the beam emitted from the laser source is linearly polarized by the polarizer, its polarization state is adjusted by the half-wave plate, its power is attenuated by the attenuator, and stray light is filtered out by the aperture to form the modulated laser beam; The optical transformation and detection assembly includes, in sequence along the reflected light path, an error amplification unit, a Fourier lens, and a two-dimensional PSD detection unit; the reflected light beam from the front surface is amplified by the error amplification unit to amplify the angle deviation, and the Fourier lens converts the angle change into a position displacement on the rear focal plane. The two-dimensional PSD detection unit located on the focal plane receives the light spot and outputs the corresponding electrical signal. The error amplification unit includes: a first reflector and a second reflector; The first reflector and the second reflector are arranged opposite to each other; The reflected beam is incident on one end of the first reflector. After incident, it is reflected at least once by the second reflector between the first and second reflectors, and then exits through the other end of the second reflector, thereby amplifying the angular deviation. The first reflector is set parallel to the horizontal reference. The reflecting surface of the second reflector, which is opposite to the first reflector, is set at a preset angle to the horizontal reference plane; the non-reflecting surface of the second reflector is set parallel to the horizontal reference plane. The reflecting surface of the second reflector is rotated by the preset angle about the Y-axis parallel to the incident plane.

2. The incident angle measurement system according to claim 1, characterized in that, Both the first and second reflectors have a reflectivity greater than 99% and are made of the same material.

3. The incident angle measurement system according to claim 1, characterized in that, The range of the reference incident angle is 30°-45°.

4. A method for measuring the angle of incidence, based on the angle of incidence measurement system as described in any one of claims 1-3, characterized in that, include: The light is incident on the surface of the standard part at a preset reference incident angle, the optical path parameters of the measurement system are calibrated, and the initial imaging position coordinates of the initial spot on the two-dimensional PSD detection unit are recorded at this time. The light beam is incident on the front surface of the glass window to be tested at the reference incident angle, the reflected light beam is received from the front surface, the reflected light beam is optically magnified and transformed, and converted into an electrical signal characterizing the position of the light spot. The electrical signal is collected and processed. Based on the change in the imaging position of the reflected beam on the two-dimensional PSD detection unit, the incident angle deviation of the incident light relative to the front surface is quantitatively calculated to obtain the actual incident angle.

5. The method for measuring the incident angle according to claim 4, characterized in that, The quantitative calculation of the incident angle deviation of the incident light relative to the front surface includes: Acquire the real-time imaging position coordinates of the real-time light spot on the two-dimensional PSD detection unit during the measurement process; Based on the initial imaging position coordinates and the real-time imaging position coordinates, calculate the positional changes of the light spot in the X-axis and Y-axis directions; Based on the position change and the optical path parameters calibrated by the measurement system, a correspondence between the position change of the light spot and the incident angle deviation is established, and the deviation values ​​of the incident angle in the X-axis direction and the Y-axis direction are obtained.

6. The method for measuring the incident angle according to claim 5, characterized in that, The imaging position coordinates on the two-dimensional PSD detection unit are: ， ， in, , These represent the effective photosensitive surface size of the two-dimensional PSD detection unit in the X-axis and Y-axis directions, respectively. , , , These represent the output signals of the corresponding electrodes of the two-dimensional PSD detection unit.

7. The method for measuring the incident angle according to claim 4, characterized in that, The actual incident angle includes: ， ， in, , These represent the components of the actual incident angle in the X-axis and Y-axis directions, respectively. Indicates the reference angle of incidence; , These represent the deviations of the incident angle in the X-axis and Y-axis directions, respectively.

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