Laser auto-collimation peak alignment angle measuring method and device

Abstract

The invention relates to the technical field of precision optical detection, and discloses a laser auto-collimation peak alignment angle measuring method and device, and the device comprises a point light source, a first spectroscope located in the emergent direction of the point light source, and a collimating mirror and a measured prism element which are sequentially arranged along the reflection direction of the first spectroscope; the rotating table bears the prism element to be measured, and the rotating table is connected with an angle measuring module for measuring the rotating angle of the prism element; the detection unit comprises a slit plate and a photoelectric detector which are sequentially arranged in the direction opposite to the reflection direction of the first spectroscope, and the slit plate is provided with a slit; and the controller is respectively connected with the point light source, the rotary table, the angle measurement module and the photoelectric detector, and finally high-resolution and high-precision measurement and the like of the included angle of the measured prism element are realized.

Description

Technical Field

[0001] This invention relates to the field of precision optical inspection technology, and in particular to a laser autocollimation peak alignment angle measurement method and device for high-precision measurement of the plane angle of optical prisms, coaxial mirrors and prism elements. Background Technology

[0002] Planar prism elements are widely used in aerospace, satellite exploration, and military weaponry. The error of the plane angle of the prism seriously affects important performance parameters such as imaging quality, reliability, and stability of the optical system. With the improvement of my country's military industry and the development of national defense needs, higher precision and quality requirements have been put forward for the processing of high-precision optical prisms and many optical and mechanical parts with strict requirements on angles in plane mirror prism optical systems. Therefore, high-precision measurement of the plane angle of prism elements is of great significance.

[0003] For measuring the included angle of prism elements, there are mainly optical indexing head method, circular grating method, optical internal reflection method, interferometry, fiber optic method, ring laser method, and autocollimation method. The optical indexing head method offers high accuracy and sensitivity, but its reliance on visual reading of the measured information results in low efficiency and cumbersome operation. The circular grating method offers high accuracy and stability, enabling full-circumference measurement, but its dynamic characteristics are poor, and precise alignment between the grating and the turntable is crucial. The optical internal reflection method features small instrument size and simple structure, but its measurement accuracy is not high. The interferometry method offers high resolution and accuracy, but its operating conditions are demanding, its environmental adaptability is poor, and its cost is high. The fiber optic method offers high sensitivity and wide bandwidth, but its measurement resolution is low and its dynamic range is small. The ring laser method offers a wide dynamic range but is costly, and it is sensitive to environmental factors, resulting in significant measurement errors in conventional environments.

[0004] Among existing methods, autocollimation is widely used as an important means of measuring angles due to its advantages of high measurement resolution and high measurement accuracy. However, when autocollimation uses a long-focal-length autocollimating tube for high-sensitivity alignment, the focused spot is large and easily affected by the surface area and reflectivity of the measured element, which limits the angle measurement accuracy of autocollimation. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a laser autocollimation peak alignment angle measurement method and apparatus, which achieves high-resolution alignment of the surface of the measured prism element, suppresses the influence of element tower difference on the measurement results, and improves the measurement accuracy of the plane angle of the measured prism element.

[0006] The first aspect of this invention provides a method and apparatus for measuring the peak alignment angle of a laser autocollimation. The apparatus for measuring the peak alignment angle of a laser autocollimation includes: A point light source, a first beam splitter located in the emission direction of the point light source, a collimating mirror and a prism element to be measured arranged sequentially along the reflection direction of the first beam splitter; The rotary worktable carries the prism element to be measured, and the rotary worktable is connected to an angle measuring module to measure its rotation angle. The detection unit includes a slit plate and a photodetector arranged sequentially in the opposite direction to the reflection direction of the first beam splitter, and the slit plate has a slit; The controller is connected to the point light source, the rotary table, the angle measurement module, and the photodetector. The controller controls the point light source to emit a diverging beam and controls the rotation of the rotary table. The diverging beam is collimated into parallel light after passing through the first beam splitter and collimating lens and then illuminates the prism element under test. The rotation of the rotary table causes the prism element under test to rotate. The focused light spot on the slit plate passes through the slit, and the photodetector detects the light intensity signal transmitted through the slit. The controller uses the light intensity signal as the vertical axis and the rotation angle value of the rotary table as the horizontal axis to plot the peak alignment curve. The peak alignment curve is used to obtain the angles of each face of the prism element under test based on its peak point.

[0007] Optionally, the slot plate is made of an opaque material and the thickness of the slot plate is greater than 0.1mm.

[0008] Optionally, the width of the slit is 0.1 to 1 times the diameter of the light spot.

[0009] Optionally, a coarse aiming unit located between the first beam splitter and the collimating lens is also included. The coarse aiming unit detects the optical path information in front of the photodetector. The controller is connected to the coarse aiming unit and adjusts the tilt angle and position of the prism element under test through the optical path information obtained by the coarse aiming unit.

[0010] Optionally, the coarse aiming unit includes a second beam splitter, a field mirror located sequentially in the reflection direction of the second beam splitter, and an image photodetector, with the image photodetector connected to the controller.

[0011] Optionally, the rotary table includes: a motor and an adjustable and self-aligning table connected by a coupling and bearings, the motor and a motor driver are connected, the motor driver is connected to a controller, and the motor speed is 0.01 degrees / second to 10 degrees / second.

[0012] Optionally, the point light source includes a laser and a light source converging mirror arranged coaxially.

[0013] Optionally, the angle measurement module includes a circular grating, which is mounted on the rotating shaft of the rotary table.

[0014] Optionally, the rotary table can rotate in the following ways: forward, reverse, and reciprocating.

[0015] A second aspect of the present invention provides a method for measuring the peak alignment angle of a laser autocollimation, using the aforementioned laser autocollimation peak alignment angle measuring device, comprising the following steps: The divergent beam emitted by the point light source is reflected by the first beam splitter and then collimated into parallel light by the collimating lens. The parallel light illuminates the prism element under test. The light reflected by the prism element under test is converged by the collimating lens and then by the first beam splitter to form a focused spot on the slit plate. As the prism element being measured rotates with the rotary table, the focused spot moves laterally and passes through the slits in sequence. The photodetector detects the light intensity passing through the slit and obtains the light intensity signal. The angle measurement module measures the corresponding rotation angle of the rotary table. Using the light intensity signal as the vertical axis and the rotation angle value of the rotary table as the horizontal axis, a peak alignment curve is plotted. Each vertical face of the prism element under test obtains a peak alignment curve, and the angle corresponding to the peak point of each peak alignment curve is the angle of each face of the prism element under test.

[0016] The technical solution provided by the embodiments of the present invention has the following advantages compared with the prior art: This invention provides a laser autocollimation peak alignment angle measurement method and device. The method employs autocollimation peak alignment, which uses the principle of autocollimation peak alignment to align the surface of the prism element under test. By combining a long-focal collimation optical path with peak detection, the surface alignment resolution of the prism element is significantly improved. The influence of prism element tower aberration is suppressed through a photodetector and a one-dimensional single-slit design. The autocollimation peak alignment method can overcome the diffraction limit, leveraging the high sensitivity of the long-focal autocollimation optical path while suppressing the influence of long-focal diffraction, thus improving alignment resolution and achieving high-precision alignment of the surface of the prism element under test. Alignment is performed using the zero-crossing point of the peak alignment signal, effectively suppressing the influence of differences in the reflective surface area and reflectivity of the prism element under test, improving the adaptability and repeatability of alignment for each face of the prism element under test. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a laser self-collimation peak alignment angle measuring device provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the movement of the converging light spot on the surface of the slit plate provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the detection unit provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of a point light source provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of the rotary table provided in an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures: 1. Point light source; 2. First beam splitter; 3. Collimating lens; 4. prism element under test; 5. Rotary stage; 6. Circular grating; 7. Detection unit; 8. Peak alignment curve; 9. Coarse aiming unit; 10. Laser; 11. Light source converging lens; 12. Slit plate; 13. Photodetector; 14. Second beam splitter; 15. Field lens; 16. Image photodetector; 17. Slit; 18. Alignment curve one; 19. Focused spot; 20. Alignment curve two; 21. Alignment curve three; 22. Controller; 23. Bearing; 24. Coupling; 25. Motor; 26. Motor driver; 27. Tilt and centering stage. Detailed Implementation

[0019] The following detailed description of a specific embodiment of the present invention is provided in conjunction with the accompanying drawings. However, it should be understood that the scope of protection of the present invention is not limited to the specific embodiment.

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the technical solution of this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0021] The present invention will be described below through several specific embodiments. To keep the following description of the embodiments clear and concise, detailed descriptions of known functions and components may be omitted. When any component of an embodiment of the present invention appears in more than one drawing, the component may be represented by the same reference numerals in each drawing.

[0022] like Figure 1 , Figure 2 and Figure 3As shown, at least some embodiments of the present invention provide a method and apparatus for measuring the peak alignment angle of a laser autocollimation, comprising: a point light source 1, a first beam splitter 2 located in the emission direction of the point light source 1, a collimating mirror 3 arranged sequentially along the reflection direction of the first beam splitter 2, and a prism element 4 to be measured. Under the command of a controller 26, the point light source 1 emits a diverging beam, which, after being reflected by the first beam splitter 2, enters the collimating mirror 3, which converts the diverging beam into high-quality parallel light. A rotary table 5 carries the prism element 4 to be measured and rotates... The worktable 5 is connected to an angle measuring module that measures its rotation angle. Parallel light is perpendicularly irradiated onto the prism element 4 (such as a polyhedron) mounted on the rotary worktable 5. The controller 22 drives the rotary worktable 5 to slowly and precisely rotate the prism element 4. The detection unit 7 includes a slit plate 12 and a photodetector 13 arranged sequentially in the opposite direction to the reflection direction of the first beam splitter 2. The slit plate 12 has a slit 17. The light beam reflected from the optical surface of the prism element 4 returns along its original path and passes through the collimating lens 3 again. At this time, the collimating lens 3 converges the returning parallel light, and this converged light passes through the first beam splitter 2 and reaches the detection unit 7. The detection unit 7 consists of a slit plate 12 and a photodetector 13 thereafter. The slit 17 on the slit plate 12 is located near the focal plane of the collimating lens 3. The controller 22 is connected to the point light source 1, the rotary stage 5, the angle measurement module and the photodetector 13 respectively. The controller 22 controls the point light source 1 to emit a diverging beam and controls the rotary stage 5 to rotate. After passing through the first beam splitter 2 and the collimating lens 3, the diverging beam is collimated into parallel light and illuminates the prism element 4 under test. The rotation of the rotary stage 5 drives the prism element 4 under test to rotate. The focused light spot 19 on the slit plate 12 passes through the slit 17. The photodetector 13 detects the light intensity signal transmitted through the slit 17. The controller 22 uses the light intensity signal as the vertical axis and the rotation angle value of the rotary stage 5 as the horizontal axis to draw the peak alignment curve 8. When the rotary table 5 rotates, the focused light spot 19 scans on the slit plate 12, and the photodetector 13 detects the light intensity passing through the slit 17 in real time. The controller 22 synchronously collects the rotation angle value of the rotary table 5 (from the angle measurement module) and the light intensity signal of the photodetector 13. The controller 22 plots the peak alignment curve 8 with the rotation angle value on the horizontal axis and the light intensity signal on the vertical axis. The peak alignment curve 8 is used to obtain the angle of each face of the prism element 4 under test based on its peak points. Each peak point on the curve corresponds to the normal direction of a reflecting surface of the prism element 4 under test (at this time, the focused light spot 19 just passes through the center of the slit 17, and the light intensity is the maximum). By calculating the rotation angle difference corresponding to adjacent peak points, the inter-face angle of the focused light spot 19 can be obtained.

[0023] This invention provides a laser autocollimation peak alignment angle measurement method and device. The method employs autocollimation peak alignment, which uses the principle of autocollimation peak alignment to align the surface of the prism element under test. By combining a long-focal collimation optical path with peak detection, the surface alignment resolution of the prism element is significantly improved. The influence of prism element tower aberration is suppressed through a photodetector and a one-dimensional single-slit design. The autocollimation peak alignment method can overcome the diffraction limit, leveraging the high sensitivity of the long-focal autocollimation optical path while suppressing the influence of long-focal diffraction, thus improving alignment resolution and achieving high-precision alignment of the surface of the prism element under test. Alignment is performed using the zero-crossing point of the peak alignment signal, effectively suppressing the influence of differences in the reflective surface area and reflectivity of the prism element under test, improving the adaptability and repeatability of alignment for each face of the prism element under test.

[0024] Optionally, the slit plate 12 is made of an opaque material, such as metal, plastic, glass coated with a light-absorbing material, or crystal. The thickness of the slit plate 12 is greater than 0.1 mm. Through interaction with the focused spot 19, the angular deviation information of the beam is linearly converted into a light intensity change signal, which is the physical basis of the peak alignment measurement method. The geometric center of the slit 17 defines a precise reference position in the optical path. The system only determines that it is "aligned" when the center of the focused spot 19 coincides with this reference position. The opaque material ensures that no stray light, except through the slit, can be transmitted to the photodetector behind it. This is crucial for obtaining a high signal-to-noise ratio and high-contrast peak signal. Thickness greater than 0.1 mm: The primary purpose of this thickness requirement is to ensure that the slit plate has sufficient mechanical strength and flatness. An excessively thin plate is prone to deformation due to internal stress or fixing pressure, leading to a loss of geometric accuracy of the slit and introducing systematic errors. Sufficient thickness allows for the use of more precise machining processes (such as wire EDM and laser processing) to manufacture the slit, resulting in a vertical, sharp slit edge with minimal burrs. Simultaneously, the slit thickness (i.e., slit depth) introduces a certain degree of diffraction. While diffraction widens the light spot, in this embodiment, a carefully designed thickness can match the light spot size, making the intensity signal change curve (i.e., edge response function) steeper as the light spot sweeps across the slit. This, in turn, helps improve the accuracy of peak position determination. The width of slit 17 should be slightly larger than the Airy disk diameter on the focal plane of collimating lens 3. If the width is too large, the peak curve will become flat, peak positioning will be less sensitive, and measurement sensitivity will decrease. If the width is too small, the transmitted light intensity will be significantly weakened, and the diffraction effect will be too strong, leading to a decrease in the signal-to-noise ratio.

[0025] Specifically, the width of slit 17 is 0.1 to 1 times the diameter of the light spot. The fundamental function of slit 17 in the device of this invention is to linearly convert the position information of the focused light spot 19 into a light intensity signal readable by the photodetector 13. The quality of this conversion process is directly determined by the ratio between the slit width (W) and the diameter of the focused light spot (D, usually referring to the Airy disk diameter or the waist diameter of the Gaussian spot). The width of slit 17 is 0.1 to 1 times the diameter of the light spot; this range is a precisely balanced "golden interval" designed to balance measurement sensitivity, signal strength, and positioning accuracy. When W / D ≈ 1.0 (wide slit mode): most light energy is allowed to pass through, the signal strength is maximum, the signal-to-noise ratio is high, and the alignment tolerance requirements of the optical system are relatively relaxed. When the focused light spot 19 sweeps across slit 17, the light intensity changes slowly, resulting in a relatively flat peak curve. This leads to less sensitive peak positioning, and relatively low measurement sensitivity and accuracy. It is suitable for applications where high accuracy is not required, but strong signal strength and good system robustness are needed. When W / D ≈ 0.1 (narrow slit mode): A small change in the position of the focused spot 19 will cause drastic fluctuations in light intensity, resulting in a very steep peak curve, which greatly improves the sensitivity and accuracy of peak position determination. However, the amount of light transmitted decreases sharply, the signal is weak, and the signal-to-noise ratio is poor. Simultaneously, the diffraction effect will be very significant, potentially distorting the signal waveform. It becomes extremely sensitive to mechanical vibration and spot stability. Suitable for laboratory conditions requiring extreme precision and ultra-stable environments with low-noise detection systems. When W / D is between 0.3 and 0.7: Within this range, the system can simultaneously obtain a sufficiently steep peak curve slope to achieve high-precision peak positioning and a sufficiently strong light signal to ensure a good signal-to-noise ratio. When the focused spot 19 passes through the slit 17, Fraunhofer diffraction occurs. The narrower the slit 17 (the smaller the W / D), the stronger the diffraction effect, and the outgoing beam will diverge, which is equivalent to forming a "diffraction-broadened" spot on the detector. The change in light intensity received by photodetector 13 from minimum to maximum as the focused spot 19 passes through the edge of slit 17 is called the edge response. The W / D ratio directly determines the slope of this response curve. The steeper the slope, the stronger the system's ability to detect edges (i.e., peak centers).

[0026] While slit-based detection systems offer extremely high precision (down to the nanometer-radian level), their linear operating range is very limited (typically only a few tens of microradians). If the light spot deviates too far from the slit region, the photodetector will be unable to generate an effective differential signal, causing the system to "lose lock." At the start of the measurement, the installation of the measured prism element 4 will inevitably have a large initial angular and positional deviation, far exceeding the acquisition range of a precision aiming system. Manually finding and approaching the alignment point is an extremely time-consuming process dependent on operator experience, making automated measurement impossible.

[0027] Based on the above issues, refer again Figure 1The laser autocollimation peak alignment angle measuring device provided in at least some embodiments of the present invention also includes a coarse aiming unit 9 located between the first beam splitter 2 and the collimating lens 3. The coarse aiming unit 9 detects the optical path information in front of the photodetector 13. The controller 22 is connected to the coarse aiming unit 9 and adjusts the tilt angle and position of the measured prism element 4 through the optical path information obtained by the coarse aiming unit 9.

[0028] Specifically, the coarse aiming unit 9 includes a second beam splitter 14, a field mirror 15 located in the reflection direction of the second beam splitter 14, and an image photodetector 16, which is connected to the controller 22.

[0029] The main function of the second beam splitter 14 is to couple a small portion of the beam energy from the main optical path with a low reflectivity (e.g., 10%~20%) and reflect it to the coarse aiming detection optical path. The vast majority (80%~90%) of the laser energy passes through the second beam splitter 14 and continues to the collimating lens 3 and the measured prism element 4, ensuring that the light signal returning to the photodetector 13 has sufficient intensity to maintain its extremely high signal-to-noise ratio and measurement accuracy. The reflected 10%~20% of the light energy is sufficient for the image detector 16 to obtain a clear and bright beacon spot, completing the coarse aiming task. The field lens 15, typically a convex lens, is placed in the reflected optical path of the second beam splitter 14. Its key function is to bring the spot information from infinity closer and image it onto the target surface of the image detector 16. It converges the returning parallel light from infinity, carrying angular information, into a clear spot image. The position of this spot on the detector directly corresponds to the tilt angle of the working surface of the measured prism. The beam from the collimating lens may have a large aperture, while the target surface size of the image detector 16 is limited. The field lens 15 can converge the large-aperture parallel light, making it effectively received by a small-sized detector. The focal length of the field lens 15 determines the field of view of the coarse aiming system. The shorter the focal length, the larger the field of view, and the larger the range of initial deviations that can be captured, which is very advantageous for rapid initial acquisition. The image detector 16 is an area-array CCD or CMOS camera. It converts the optical image of the spot light arriving at its target surface into a digital signal containing pixel coordinates and grayscale information.

[0030] The controller 26 drives the image detector 16 to perform continuous or triggered acquisition, obtaining the raw image containing the light spot. The controller 26 runs a built-in image processing algorithm. First, threshold segmentation is performed to separate the light spot from the background. Then, the centroid algorithm is used to calculate the precise position of the light spot in the pixel coordinate system. The controller 26 compares the calculated centroid position of the light spot with a preset reference position to obtain the pixel-level deviation. The controller 26 converts the pixel deviation into an angular deviation based on the focal length of the field lens 15 and the pixel size of the detector. Subsequently, it generates a corresponding control signal to drive the two-dimensional tilt adjustment mechanism on the rotary table 5 to adjust the posture of the measured prism element 4. The above process forms a closed-loop control. The controller 26 continuously monitors the position of the light spot and continuously adjusts it until the centroid of the light spot stabilizes within the tolerance range allowed by the reference position, indicating that the coarse aiming is complete.

[0031] refer to Figure 5The rotary table 5 includes a motor 25 and a tilt-aligning and self-aligning table 27 connected via a coupling 24 and bearings 23. The motor 25 is connected to a motor driver 26, which in turn is connected to a controller 22. The motor 25 rotates at speeds of 0.01° / s to 10° / s. The motor 25 can be driven by stepper motors, continuously variable motors, or servo drives. The coupling 24 connects the output shaft of the motor 25 to the spindle of the tilt-aligning and self-aligning table 27. It can be a diaphragm coupling or a bellows coupling, which effectively transmits torque while compensating for minor alignment errors without introducing additional backlash. The bearings 23 serve as the rotational support for the tilt-aligning and self-aligning table 27. Their rotational accuracy and runout are directly transmitted as angular errors. Ultra-high precision angular contact ball bearings or air static pressure bearings can be selected. Air static pressure bearings are virtually frictionless and wear-free, and possess extremely high rotational accuracy and stability, making them the preferred choice for the highest precision applications. The tilt and centering stage 27 integrates tilt and centering adjustment functions. When installing the prism element 4 to be measured, it must be ensured that its rotation axis is coaxial with the mechanical axis of the tilt and centering stage 27, and that its end face is perpendicular to the axis. Any tilt or eccentricity will cause unnecessary drift of the light spot during scanning, introducing Abbe error and cosine error, which seriously reduces measurement accuracy. The tilt and centering stage 27 can precisely adjust the pitch, yaw, and horizontal position of the stage through multiple (usually three) precision micron head screws to ensure that the light beam can be incident directly on each reflecting surface of the element being measured. The motor driver 26 receives a low-voltage command signal from the controller 22 and converts it into the high-power current / voltage required to drive the motor. The controller 22 sends pulse / direction signals or analog voltage signals to the motor driver 26 to precisely set the rotation speed and target position of the motor 25, and forms a fully closed-loop position control system with the angle measurement module to ensure that the actual value of the rotation angle is consistent with the command value. The motor 25 operates at an ultra-low speed (0.01° / s to 0.1° / s): The high-precision measurement mode is suitable for final fine measurements, calibration, or sampling of weak signals. The extremely low speed means that the controller 22 can collect a massive amount of data points in the very short time it takes for the focused spot 19 to sweep across the slit 17. This allows for high-density sampling of peak curves, and through subsequent Gaussian or polynomial fitting algorithms, the peak position can be accurately determined at the sub-pixel (sub-arcsecond) level, far exceeding the resolution of the sensor itself. Low-speed movement minimizes vibration and impact caused by inertia and reduces bearing friction instability, ensuring smooth movement and reliable data. At each sampling point, the photodetector 13 has a longer integration time to collect photons, thereby improving the signal-to-noise ratio. At a high speed (1° / s to 10° / s): The fast scanning and coarse positioning mode is suitable for rapid target finding, preliminary screening, or production cycles with high measurement efficiency requirements. It can significantly shorten the time to measure a complete prism cycle, improving throughput efficiency.Medium speed range (0.1 degrees / second to 1 degree / second): General balance mode, which ensures high measurement accuracy while taking into account reasonable measurement time, is the ideal balance point between accuracy and efficiency.

[0032] refer to Figure 4 The point light source 1 includes a laser 10 and a light source converging mirror 11 arranged coaxially.

[0033] The function of the light source converging mirror 11 is to further converge the tiny diverging beam emitted by the laser 10, forming a very bright, extremely small virtual point source within a very short distance. This virtual point source is located on the object-side focal plane of the collimating mirror 3. Although the emitting surface of the laser 10 is small, it still has physical dimensions. By efficiently collecting and focusing the emitted light, the light source converging mirror 11 effectively creates a secondary light source that is smaller and more ideal than the physical emitting surface. According to the principles of geometric optics, the emitted light can only be perfectly parallel when the light source is located on the focal plane of the collimating mirror. The light source converging mirror 11 ensures that the image point of the light emitted by the laser falls precisely on the focal point of the collimating mirror 3 after passing through it. It more effectively couples the beam of light emitted by the laser 10, which has a certain divergence angle, into the subsequent collimating mirror 3, reducing light waste and improving the overall luminous flux and signal-to-noise ratio of the system.

[0034] Optionally, the angle measurement module includes a circular grating 6, which is mounted and fixed on the rotation axis of the rotary table 5. The circular grating 6 consists of a main grating ruler and an indicator grating. The main grating ruler is a disk with tens of thousands to tens of millions of precision lines etched on a glass or metal substrate. These lines are radially distributed. When the main grating rotates with the axis, while the indicator grating remains fixed, the interaction of the lines produces alternating bright and dark moiré fringes. Each time the axis rotates through a tiny angle, the moiré fringes shift by one cycle. By reading the changes in the moiré fringes with a photodetector and processing them through an electronic subdivision circuit, one fringe cycle can be subdivided into thousands of parts, thus achieving high-resolution measurement of minute angle changes. The circular grating is one of the most accurate devices in direct angle measurement, with an accuracy of ±0.1 arcseconds or even higher. Through electronic subdivision, its resolution can easily reach the order of 0.01 arcseconds, sufficient to match or even surpass the sensitivity of optical autocollimation systems. By combining circular grating multi-reading head detection for angle detection, the uniformity of grating lines and installation eccentricity error can be separated, thereby improving the accuracy of plane angle measurement.

[0035] Optionally, the rotary table 5 can rotate in the following ways: forward, reverse and reciprocating rotation. This allows multiple measurement curves to be obtained during measurement, and the average value can be taken as the final measurement curve to further improve measurement accuracy.

[0036] Another embodiment of the present invention provides a method for measuring the laser autocollimation peak alignment angle, using the above-described laser autocollimation peak alignment angle measuring device, including the following steps: The divergent beam emitted by the point light source 1 is reflected by the first beam splitter 2 and collimated into parallel light by the collimating lens 3. The parallel light illuminates the prism element 4 under test. The light path reflected by the prism element 4 under test is converged by the collimating lens 3 and then converged by the first beam splitter 2 onto the slit plate 12 to form a focused spot 19. As the rotary table 5 rotates, the focused spot 19 moves laterally and passes through the slit 17 in sequence. The photodetector 13 detects the light intensity passing through the slit 17 and obtains the light intensity signal. The angle measurement module measures the corresponding rotation angle of the rotary table 5. Using the light intensity signal as the vertical axis and the rotation angle value of the rotary table 5 as the horizontal axis, a peak alignment curve 8 is plotted. Each vertical surface of the measured prism element 4 obtains a peak alignment curve 8. The angle corresponding to the peak point of each peak alignment curve 8 is the angle of each surface of the measured prism element 4.

[0037] Refer again Figure 1 In one specific embodiment, the slit plate 12 is 0.5 mm thick and made of aluminum alloy (with a blackened surface oxidation). The slit 17 is 50 μm wide. Alignment curves 1-18, 20, and 21 are obtained according to the above method. The peak position of alignment curve 18 corresponds to the horizontal coordinate... θ 1. Align the peak position of curve 20 with the x-axis corresponding to: θ 2. The horizontal coordinate corresponding to the peak position of curve 3.21 is... θ 3. The relative angle between the first and second faces of the measured prism element 4 is 3. θ 2- θ 1. The relative angle between the second and third faces is... θ 3- θ 2. By analogy, the angle between each face is 30 degrees, and the measured prism element 4 is a 12-faceted prism.

[0038] Optionally, the surface of the prism element 4 under test includes a prism, a corner cabinet, a common reflector group, and a multifaceted prism, and the reflecting surface of the prism element 4 under test includes an inner reflecting surface and an outer reflecting surface.

[0039] Optionally, the photodetector 13 can be a large-area photodetector, a large-area photovoltaic cell, or a large-area CCD.

[0040] The laser self-collimation peak alignment angle measurement method utilizes the self-collimation peak alignment principle to align the surface of the prism element under test. By combining a long-focal collimation optical path with peak detection, the surface alignment resolution of the prism element is significantly improved. The influence of prism element tower difference is suppressed by photodetector and one-dimensional single slit design. Angle detection is performed by combining circular grating multi-readhead detection to separate grating line uniformity and installation eccentricity error, ultimately achieving high-resolution and high-precision measurement of the included angle of the prism element under test.

[0041] The above inventions are merely a few specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A laser self-collimation peak alignment angle measuring device, characterized in that, include: A point light source, a first beam splitter located in the emission direction of the point light source, a collimating mirror and a prism element to be measured arranged sequentially along the reflection direction of the first beam splitter; A rotary table carries the prism element to be measured, and the rotary table is connected to an angle measuring module that measures its rotation angle. The detection unit includes a slit plate and a photodetector arranged sequentially in the opposite direction to the reflection direction of the first beam splitter, wherein the slit plate has a slit. The controller is connected to the point light source, the rotary table, the angle measurement module, and the photodetector. The controller controls the point light source to emit a diverging beam and controls the rotation of the rotary table. The diverging beam is collimated into parallel light after passing through the first beam splitter and collimating lens and then illuminates the prism element under test. The rotation of the rotary table causes the prism element under test to rotate. The focused light spot on the slit plate passes through the slit, and the photodetector detects the light intensity signal transmitted through the slit. The controller uses the light intensity signal as the vertical axis and the rotation angle value of the rotary table as the horizontal axis to plot the peak alignment curve. The peak alignment curve is used to obtain the angles of each face of the prism element under test based on its peak point.

2. The laser autocollimation peak alignment angle measuring device as described in claim 1, characterized in that, The slit plate is made of an opaque material and its thickness is greater than 0.1 mm.

3. The laser autocollimation peak alignment angle measuring device as described in claim 1, characterized in that, The width of the slit is 0.1 to 1 times the diameter of the light spot.

4. The laser autocollimation peak alignment angle measuring device as described in claim 1, characterized in that, It also includes a coarse aiming unit located between the first beam splitter and the collimating lens. The coarse aiming unit detects the optical path information in front of the photodetector. The controller is connected to the coarse aiming unit and adjusts the tilt angle and position of the prism element under test through the optical path information obtained by the coarse aiming unit.

5. The laser autocollimation peak alignment angle measuring device as described in claim 4, characterized in that, The coarse aiming unit includes a second beam splitter, a field mirror located sequentially in the reflection direction of the second beam splitter, and an image photodetector, wherein the image photodetector is connected to the controller.

6. The laser autocollimation peak alignment angle measuring device as described in claim 1, characterized in that, The rotary table includes a motor and an adjustable tilt and centering table connected by a coupling and bearings. The motor is connected to a motor driver, and the motor driver is connected to a controller. The speed of the motor is 0.01 degrees / second to 10 degrees / second.

7. The laser autocollimation peak alignment angle measuring device as described in claim 1, characterized in that, The point light source includes a laser and a light source converging lens arranged coaxially.

8. The laser autocollimation peak alignment angle measuring device as described in claim 1, characterized in that, The angle measurement module includes a circular grating, which is mounted and fixed on the rotating shaft of the rotary table.

9. The laser autocollimation peak alignment angle measuring device as described in claim 1, characterized in that, The rotary table can rotate in three ways: forward, reverse, and reciprocating.

10. A method for measuring the peak alignment angle of laser autocollimation, characterized in that, Using the laser autocollimation peak alignment angle measuring device according to any one of claims 1 to 9, the method includes the following steps: The divergent beam emitted by the point light source is reflected by the first beam splitter and then collimated into parallel light by the collimating lens. The parallel light illuminates the prism element under test. The light reflected by the prism element under test is converged by the collimating lens and then by the first beam splitter to form a focused spot on the slit plate. As the prism element being measured rotates with the rotary table, the focused spot moves laterally and passes through the slits in sequence. The photodetector detects the light intensity passing through the slit and obtains the light intensity signal. The angle measurement module measures the corresponding rotation angle of the rotary table. Using the light intensity signal as the vertical axis and the rotation angle value of the rotary table as the horizontal axis, a peak alignment curve is plotted. Each vertical face of the prism element under test obtains a peak alignment curve, and the angle corresponding to the peak point of each peak alignment curve is the angle of each face of the prism element under test.

Images