A high-precision coaxial autocollimator optical system

Abstract

The present invention relates to the field of optical measurement technology and discloses a high-precision coaxial autocollimator optical system, comprising a beam expander objective lens, a first plane reflector, a second plane reflector, a beam splitting cemented prism, a pinhole stop, a beam expander eyepiece, and a laser light source, arranged in sequence along the incident direction of light. Light is split by the beam splitting cemented prism and then incident on a PSD position sensor and a CCD detector, respectively. The present invention utilizes a beam splitting cemented prism to coaxially position the PSD position sensor and the CCD detector at the end of the beam expander objective lens. This allows the system to simultaneously receive information reflected from the laser and independently measure it, combining the advantages of both the PSD position sensor and the CCD detector. The system has the advantages of a high frame rate, a large measurement angle, and high measurement accuracy.

Description

Technical Field

[0001] The present invention relates to the field of optical measurement technology, and in particular to a high-precision coaxial autocollimator optical system. Background Art

[0002] As a high-precision angle measurement instrument, autocollimators are widely used in high-precision machine tool manufacturing, aerospace, testing institutions, and scientific research laboratories. They can also measure the stability accuracy of equipment such as electro-optical tracking systems and electro-optical stabilized aiming pods. These systems are mounted on moving platforms. Changes in the platform's posture, vibration, and disturbances during movement can cause unstable optical axis pointing, significantly affecting the clear imaging of observation equipment in electro-optical stabilized systems.

[0003] Optoelectronic stabilization systems isolate disturbances from moving objects, continuously measure and adjust the platform's attitude changes, accurately maintain a dynamic attitude reference, and track targets through image detection equipment. While suppressing external interference and achieving stability, optoelectronic stabilization systems experience stabilization errors due to various factors. The magnitude of this stabilization error is described by stabilization accuracy. If stabilization accuracy is poor, the optoelectronic stabilization system will be unable to accurately aim at the target and may even fail to track. Therefore, accurate testing of high stabilization accuracy is a prerequisite for ensuring long-range target detection and recognition in optoelectronic stabilization systems, making it a crucial test device for such systems.

[0004] However, existing autocollimators, whether using PSD position sensors or CCD detectors, have limitations. PSD position sensors exhibit nonlinearity at image edges, which reduces the confidence level of edge measurements. CCD detectors cannot maintain high frame rates without maintaining high resolution, and high frame rates without maintaining high resolution. For targets with high-frequency, large-angle motion, CCD detectors cannot simultaneously meet the requirements of high resolution and high frame rates.

[0005] Therefore, based on the above technical problems, it is necessary to develop a high-precision and large-range autocollimator. Summary of the Invention

[0006] In view of the technical problems existing in the prior art, the present invention provides a high-precision coaxial autocollimator optical system for measuring small angles and high-precision angles.

[0007] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a high-precision coaxial autocollimator optical system, comprising a beam expander objective lens, a plane reflector 1, a plane reflector 2, a beam splitting cemented prism, a pinhole aperture, a beam expander eyepiece, and a laser light source, which are arranged in sequence along the incident direction of the light; the light is split by the beam splitting cemented prism and then incident on a PSD position sensor and a CCD detector respectively.

[0008] The laser light source emits laser light, which passes through the beam expander eyepiece, pinhole diaphragm, beam splitter cemented prism, plane reflector 2, plane reflector 1, beam expander objective lens exit optical system in sequence and hits the reflector to be measured. The reflector to be measured returns the laser light along the original path, and after being split by the beam splitter cemented prism, it reaches the PSD position sensor and CCD detector respectively.

[0009] Preferably, the focal length of the beam expander objective lens is 1200 mm, the focal length of the beam expander eyepiece is 40 mm, and the beam expander objective lens and the beam expander eyepiece are combined into a 30x beam expander system.

[0010] Preferably, the beam expander objective lens comprises a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged in sequence along the incident direction of the light;

[0011] The beam expander eyepiece includes a sixth lens, a seventh lens, and an eighth lens arranged in sequence along the incident direction of the light;

[0012] The first lens has positive refractive power, is convex in the direction of incident light, and is concave in the opposite direction of incident light;

[0013] The second lens has negative optical power, is convex in the direction of incident light, and is concave in the opposite direction of incident light;

[0014] The third lens has positive refractive power, is convex in the direction of incident light, and is flat in the opposite direction of incident light;

[0015] The fourth lens has negative optical power and is concave in the direction of incident light and concave in the opposite direction of incident light.

[0016] The fifth lens has positive refractive power and is convex in the direction of incident light and convex in the opposite direction of incident light;

[0017] The second lens and the third lens are tightly bonded together, and the fourth lens and the fifth lens are tightly bonded together.

[0018] The sixth lens has negative optical power, is concave in the direction of incident light, and is convex in the opposite direction of incident light;

[0019] The seventh lens has negative optical power, is concave in the direction of incident light, and is flat in the opposite direction of incident light;

[0020] The eighth lens has negative optical power, is concave in the direction of incident light, and is convex in the opposite direction of incident light.

[0021] Preferably, the curvature radii of the surfaces of the first to eighth lenses in the direction of incident light are R1 to R8, and the curvature radii of the surfaces of the first to eighth lenses in the direction opposite to the direction of incident light are R1′ to R8′, satisfying the following conditions:

[0022] 120mm<R1<130mm, 350mm<R1′<370mm;

[0023] 350mm<R2<430mm, 65mm<R2′<75mm;

[0024] 65mm<R3<75mm, R3′=∞;

[0025] -120mm<R4<-140mm, 120mm<R4′<140mm;

[0026] 120mm<R5<140mm, -800mm<R5′<-600mm;

[0027] -60mm<R6<-30mm, -30mm<R6′<-20mm;

[0028] -40mm<R7<-20mm, R7′=∞;

[0029] -40mm<R8<-15mm, -50mm<R8′<-30mm.

[0030] Preferably, the refractive index of the glass material used for the first to eighth lenses is n1-n8, the Abbe number of the glass material used for the first to eighth lenses is v1-v8, and the following optical conditions are satisfied:

[0031] 1.48<n1<1.60, 60<v1<65;

[0032] 1.75<n2<1.85, 30<v2<40;

[0033] 1.60<n3<1.65, 55<v3<60;

[0034] 1.70<n4<1.80, 25<v4<30;

[0035] 1.90<n5<1.95, 15<v5<25;

[0036] 1.85<n6<1.95, 15<v6<20;

[0037] 1.55<n7<1.65, 50<v7<60;

[0038] 1.75<n8<1.85, 33<v8<38.

[0039] Preferably, the glass thicknesses of the first to eighth lenses are L1 to L8, respectively, and meet the following conditions:

[0040] 14mm<L1<16mm;

[0041] 5.5mm<L2<6mm;

[0042] 16mm<L3<21mm;

[0043] 4.5mm<L4<5mm;

[0044] 9mm<L5<11mm;

[0045] 2.5mm<L6<3mm;

[0046] 1.8mm<L7<2.2mm;

[0047] 1.8mm<L8<2.2mm.

[0048] Preferably, the air gap between the first lens and the second lens is 70~80mm, the air gap between the third lens and the fourth lens is 60~65mm, the air gap between the fifth lens and the plane reflector 1 is 90~110mm, the air gap between the plane reflector 1 and the plane reflector 2 is 180~200mm, the air gap between the plane reflector 2 and the beam splitting prism is 100~120mm, the air gap between the beam splitting prism and the PSD position sensor is 65mm, the air gap between the beam splitting prism and the CCD detector is 38mm, the air gap between the beam splitting prism and the pinhole aperture is 15~17mm, the air gap between the pinhole aperture and the sixth lens is 16~17mm, the air gap between the sixth lens and the seventh lens is 2~3mm, the air gap between the seventh lens and the eighth lens is 3~4mm, and the air gap between the eighth lens and the laser light source is 28~35mm.

[0049] Preferably, the beam splitting and cemented prism includes a pentaprism and two right-angle prisms, and the non-right-angle surface of the right-angle prism is cemented to the pentaprism.

[0050] Preferably, beam splitting films are provided on the bonding surfaces formed by the two right-angle prisms and the pentaprism, forming beam splitting plane A and beam splitting plane B respectively, the beam splitting ratio of beam splitting plane A and the beam splitting ratio of beam splitting plane B are both 1:1, the two acute angles of the triangular surface on the right-angle prism are 22.5° and 67.5° respectively, the angle between the optical axis corresponding to the CCD detector and the optical axis corresponding to the PSD position sensor is 45°, the optical path of the CCD detector in the pentaprism includes two sections, one of which is shared with the PSD position sensor and has a length of 36.2 mm, and the other is 30 mm long, and the optical path of the PSD position sensor and the CCD detector in one of the right-angle prisms is the same, both being 6.2 mm.

[0051] Preferably, the CCD detector can be a high-resolution area array detector or a high-frame-rate linear array CCD.

[0052] The present invention also includes other components that enable a high-precision coaxial autocollimator optical system to function properly, all of which are conventional technical means in the art. In addition, devices or components not limited in the present invention all adopt conventional technical means in the art.

[0053] The present invention provides a high-precision coaxial autocollimator optical system, which uses a beam splitting cemented prism to coaxially integrate a PSD position sensor and a CCD type detector into one system. The two systems perform mutual self-checking and verification, and then use the signal processing and settlement methods in the existing technology to further screen and correct the data with large output results, which can reduce measurement errors and improve measurement accuracy.

[0054] The optical system of the present invention can detect the angular change of the object side reflector. Through the beam splitting and cementing prism, the PSD position sensor, the CCD detector and the laser light source can be coaxial and the optical path difference between the PSD position sensor and the CCD detector is the same, thereby achieving high-precision detection and self-correction and reducing measurement interference caused by complex environments.

[0055] The present invention adopts a 37° folding optical path and is matched with a 22.5° beam splitter prism to fold the CCD detector, which can fully utilize space and effectively reduce the overall size.

[0056] The present invention uses a beam splitting cemented prism to place the PSD position sensor and the CCD type detector coaxially at the objective end of the beam expander, which can simultaneously receive the information reflected by the laser and measure it independently. It can take into account the advantages of the PSD position sensor and the CCD type detector, and has the advantages of high frame rate, large measurement angle, high measurement accuracy, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 Schematic diagram of an optical system according to an embodiment of the present invention.

[0058] Figure 2 Schematic diagram of the appearance of the beam splitting cemented prism in an embodiment of the present invention.

[0059] Figure 3 FIG. 4 is a graph showing the optical transfer function (MTF) of the beam expander objective lens according to an embodiment of the present invention.

[0060] Figure 4 This is a distortion diagram of the beam expander objective lens according to an embodiment of the present invention.

[0061] Figure 5 2 is a point diagram of a beam expander system according to an embodiment of the present invention.

[0062] Figure 6This is a PSF diagram of the beam expander system according to an embodiment of the present invention.

[0063] In the figure: 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens; 6. Plane reflector 1; 7. Plane reflector 2; 8. PSD position sensor; 9. Beam splitting cemented prism; 10. Pinhole stop; 11. Sixth lens; 12. Seventh lens; 13. Eighth lens; 14. Laser light source; 15. CCD detector; 16. Pentaprism; 17. Right-angle prism; 18. Beam splitting surface A; 19. Beam splitting surface B; 20. Measured reflector. DETAILED DESCRIPTION

[0064] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0065] Example

[0066] See also Figure 1 A high-precision coaxial autocollimator optical system includes a beam expander objective lens, a plane reflector 6, a plane reflector 7, a beam splitting cemented prism 9, a pinhole aperture 10, a beam expander eyepiece, and a laser light source 14, which are arranged in sequence along the incident direction of the light; the light is split by the beam splitting cemented prism 9 and then incident on the PSD position sensor 8 and the CCD detector 15 respectively.

[0067] In this embodiment, the laser light source 14 emits laser light, which passes through the beam expander eyepiece, the pinhole aperture 10, the beam splitting cemented prism 9, the plane reflector 2 7, the plane reflector 1 6, and the beam expander objective lens exit optical system in sequence and hits the reflector to be measured. The reflector to be measured returns the laser light along the original path, and after being split by the beam splitting cemented prism 9, it reaches the PSD position sensor 8 and the CCD detector 15 respectively.

[0068] The focal length of the beam expander objective lens is 1200 mm, the focal length of the beam expander eyepiece is 40 mm, and the beam expander objective lens and the beam expander eyepiece are combined into a 30x beam expander system.

[0069] The beam expander objective lens comprises a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, and a fifth lens 5 arranged in sequence along the incident direction of light;

[0070] The beam expander eyepiece includes a sixth lens 11, a seventh lens 12, and an eighth lens 13 arranged in sequence along the incident direction of the light;

[0071] The first lens 1 has positive refractive power, is convex in the direction of incident light, and is concave in the opposite direction of incident light;

[0072] The second lens 2 has a negative optical power, is convex in the direction of incident light, and is concave in the opposite direction of incident light;

[0073] The third lens 3 has positive refractive power, is convex in the direction of incident light, and is flat in the opposite direction of incident light;

[0074] The fourth lens 4 has negative optical power and is concave in the direction of incident light and concave in the opposite direction of incident light.

[0075] The fifth lens 5 has positive refractive power and is convex in the direction of incident light and convex in the opposite direction of incident light.

[0076] The second lens 2 and the third lens 3 are tightly bonded together, and the fourth lens 4 and the fifth lens 5 are tightly bonded together.

[0077] The sixth lens 11 has negative optical power, is concave in the direction of incident light, and is convex in the opposite direction of incident light;

[0078] The seventh lens 12 has negative optical power, is concave in the direction of incident light, and is flat in the opposite direction of incident light;

[0079] The eighth lens 13 has negative optical power, and is concave in the direction of incident light and convex in the opposite direction of incident light.

[0080] The curvature radii of the surfaces of the first to eighth lenses in the direction of incident light are R1 to R8, respectively. The curvature radii of the surfaces of the first to eighth lenses in the direction opposite to the direction of incident light are R1′ to R8′, respectively, satisfying the following conditions:

[0081] R1=125.27mm, R1′=365.6mm;

[0082] R2=391.7mm, R2′=68.66mm;

[0083] R3=68.66mm, R3′=∞;

[0084] R4=-136.46mm, R4′=128.53mm;

[0085] R5=128.53mm, R5′=-691.8mm;

[0086] R6<-40.2mm, R6′=-25.3mm;

[0087] R7<-30.4mm, R7′=∞;

[0088] R8<-25.3mm, R8′=-42.7mm.

[0089] The refractive index of the glass material used for the first to eighth lenses ranges from n1 to n8, and the Abbe number of the glass material used for the first to eighth lenses ranges from v1 to v8, satisfying the following optical conditions:

[0090] n1=1.52, v1=64.2;

[0091] n2=1.80, v2=35;

[0092] n3=1.61, v3=56.7;

[0093] n4=1.73, v4=28.3;

[0094] n5=1.92, v5=18.9;

[0095] n6=1.92, v6=18.9;

[0096] n7=1.61, v7=58.6;

[0097] n8=1.80,v8=35.

[0098] The glass thicknesses of the first lens 1 to the eighth lens 13 are L1 to L8, respectively, and meet the following conditions:

[0099] L1=15mm;

[0100] L2=5.8mm;

[0101] L3=19mm;

[0102] L4=4.6mm;

[0103] L5=10mm;

[0104] L6=2.7mm;

[0105] L7=2mm;

[0106] L8=2mm.

[0107] The air gap between the first lens 1 and the second lens 2 is 77.77 mm, the air gap between the third lens 3 and the fourth lens 4 is 62.41 mm, the air gap between the fifth lens 5 and the plane reflector 1 is 100.2 mm, the air gap between the plane reflector 1 and the plane reflector 2 is 190.5 mm, the air gap between the plane reflector 2 and the beam splitting and cemented prism 9 is 114 mm, the air gap between the beam splitting and cemented prism 9 and the PSD position sensor 8 is 65 mm, the air gap between the beam splitting and cemented prism 9 and the CCD detector 15 is 38 mm, the air gap between the beam splitting and cemented prism 9 and the pinhole aperture 10 is 16 mm, the air gap between the pinhole aperture 10 and the sixth lens 11 is 16.5 mm, the air gap between the sixth lens 11 and the seventh lens 12 is 2.5 mm, the air gap between the seventh lens 12 and the eighth lens 13 is 3.5 mm, and the air gap between the eighth lens 13 and the laser light source 14 is 31.3 mm.

[0108] The beam splitting cemented prism includes a pentaprism 16 and two right-angle prisms 17 , and the non-right-angled surface of the right-angle prism is cemented to the pentaprism.

[0109] The bonding surfaces formed by the two right-angle prisms and the pentaprism are both provided with beam-splitting films, forming beam-splitting surfaces A18 and beam-splitting surfaces B19, respectively. The beam-splitting ratios of beam-splitting surfaces A and B are both 1:1. The two acute angles of the triangular surfaces on the right-angle prism are 22.5° and 67.5°, respectively. The angle between the optical axis corresponding to the CCD detector and the optical axis corresponding to the PSD position sensor is 45°. The optical path of the CCD detector in the pentaprism includes two sections, one of which is shared with the PSD position sensor and has a length of 36.2 mm, and the other is 30 mm in length. The optical path of the PSD position sensor and the CCD detector in one of the right-angle prisms (the right-angle prism opposite to the CCD detector) is the same, both being 6.2 mm.

[0110] See also Figure 2 In this embodiment, the beam splitting prism is formed by gluing two identical right-angle prisms and a pentaprism together. The two acute angles of the triangular face of the right-angle prism are 22.5° and 67.5°, respectively. The pentagonal face of the pentaprism has one right angle, and the other four angles are all 112.5°. The pentagonal face is symmetrical about the angle bisector of the right angle. This special angle setting can align the three optical axes of the PSD position sensor 8, CCD detector 15, and laser light source 14, thereby achieving a coaxial effect. The two right-angle prisms are glued to two non-adjacent side surfaces of the pentaprism.

[0111] The CCD detector 15 is a high-resolution area array detector. In actual use, a high-frame-rate linear array CCD can also be used.

[0112] The laser light emitted by the laser light source 14 passes through the beam expander eyepiece (composed of the sixth lens 11, the seventh lens 12, and the eighth lens 13) and the pinhole aperture 10 in sequence to reach the beam splitting cemented prism 9, and is split on the beam splitting surface B. The reflected light is incident on the right-angle prism and is absorbed by the extinction, and the transmitted light passes through the beam splitting cemented prism 9, is reflected twice by the plane reflector 2 7 and the plane reflector 1 6, and then passes through the beam expander objective lens (composed of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, and the fifth lens 5) to reach the measured reflector 20. The reflector 20 under test returns the laser light along its original path. The returned laser light passes through the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the plane reflector 1 6, and the plane reflector 2 7 in sequence before being perpendicularly incident on the beam-splitting cemented prism 9. The beam is split on the beam-splitting surface B. The reflected light is reflected by the beam-splitting surface B and split again on the beam-splitting surface A. The resulting reflected light is reflected by the beam-splitting surface A and reaches the PSD displacement sensor 8. The transmitted light is transmitted through the beam-splitting surface A and reaches the area array CCD detector 15. The PSD displacement sensor 8 and the CCD detector 15 calculate the angular change of the reflector 20 under test based on the laser displacement caused by the angular change of the reflector 20 under test.

[0113] In this embodiment, the total length of the optical system can be reduced by bending the light path through plane reflector 1 6 and plane reflector 2 7, and the angle between the reflected light axis and the incident light axis is 37°; the air gap between the PSD position sensor 8 and the spectroscopic glued prism 9 is 65 mm, and the gap between the CCD detector 15 and the spectroscopic glued prism 9 is 38 mm. Combined with the spectroscopic bonding of the spectroscopic glued prism 9, it can be ensured that the two systems have the same optical path.

[0114] The optical transfer function (MTF) curve of the beam expander objective lens of this embodiment is as follows: Figure 3 As shown in the figure, the six curves are respectively the meridional and sagittal modulation transfer function curves for the receiving target surface at half height of 0 mm, 4 mm, and 6 mm at the diagonal half height, wherein the horizontal axis represents the spatial frequency in line pairs / millimeter (lp / mm), and the vertical axis represents the MTF value. The higher the curve, the better the imaging quality. The vertical axis MODULUS OF THE OTF stands for optical transfer function, which refers to optical transfer function. In this embodiment, the vertical axis is the optical modulation transfer function, that is, MTF, T is the meridional transfer function curve, and S is the sagittal transfer function curve.

[0115] like Figure 3 As shown in FIG. 6 , it can be seen from the six curves that the lens of this embodiment has a wavelength range of 460 nm to 660 nm, and the meridional and sagittal modulation transfer function curves are greater than 0.4 at 60 lp / mm, reaching a near diffraction limit level.

[0116] The distortion diagram of the beam expander objective lens in this embodiment is as follows: Figure 4 As shown, the horizontal axis represents the percentage value of distortion (PERCENT), and the vertical axis represents the normalized field of view. Figure 4 It can be seen that the lens distortion of this embodiment is less than 0.0001%, which further indicates that the distortion error of the optical system has little effect on the measurement accuracy of the system.

[0117] The point arrangement diagram of the beam expander system of this embodiment is as follows Figure 5 As shown, in actual application, a laser with a wavelength of 635 nm is selected for irradiation. It can be seen that the point diagram of the beam expander system of this embodiment is all discrete within the Airy disk at a wavelength of 635 nm (the black circle in the figure), indicating that it reaches a near diffraction limit level.

[0118] The PSF function curve of the beam expander system of this embodiment is as follows: Figure 6 As shown in the figure, the PSF function curve refers to the energy expansion of the imaging point of an ideal geometric object point after passing through the optical system. Figure 6 It can be seen that the bottom width of the focal point of the imaging point is relatively narrow, at 450 μm, indicating that the energy concentration of the beam expander system is relatively high and the imaging quality is good.

[0119] The present invention provides a high-precision coaxial autocollimator optical system, which utilizes a beam splitting cemented prism to coaxially integrate a PSD position sensor and a CCD detector into one system. The two systems perform mutual self-checking and verification, and then further screen and correct the data with large output results through signal processing and settlement methods in the prior art, thereby reducing measurement errors and improving measurement accuracy.

[0120] The optical system of the present invention can detect the angular change of the object side reflector. Through the beam splitting and bonding prism 9, the PSD position sensor 8, the CCD detector 15, and the laser light source 14 can be coaxial (that is, the optical axes of the three coincide before the beam splitting and bonding prism), and the optical path difference between the PSD position sensor 8 and the CCD detector 15 is the same, thereby achieving high-precision detection and self-correction, and reducing measurement interference caused by complex environments.

[0121] While the embodiments of the present invention have been described above, the above description is intended to be exemplary, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A high-precision coaxial autocollimator optical system, characterized in that: It includes a laser light source, a beam expander eyepiece, a pinhole diaphragm, a beam splitter cemented prism, a second plane reflector, a first plane reflector, and a beam expander objective lens, which are arranged in sequence along the incident direction of the light; The beam splitting cemented prism comprises a pentaprism and two right-angle prisms, wherein the non-right-angle surface of the right-angle prism is cemented to the pentaprism; Beam-splitting films are provided on the bonding surfaces formed by the two right-angle prisms and the pentaprism, forming beam-splitting planes A and B, respectively. The beam-splitting ratios of beam-splitting planes A and B are both 1:

1. The two acute angles of the triangular surface on the right-angle prism are 22.5° and 67.5°, respectively. The angle between the optical axis corresponding to the CCD detector and the optical axis corresponding to the PSD position sensor is 45°. The optical path of the CCD detector in the pentaprism consists of two sections, one of which is shared with the PSD position sensor and has a length of 36.2 mm, and the other is 30 mm in length. The optical path of the PSD position sensor and the CCD detector in one of the right-angle prisms is the same, both 6.2 mm. The laser emitted by the laser light source passes through the beam expander eyepiece and the pinhole aperture in turn to reach the beam splitting cemented prism, and is split on the beam splitting surface B. The reflected light is incident on the right-angle prism and is absorbed by the extinction. The transmitted light passes through the beam splitting cemented prism, is reflected twice by plane mirror 2 and plane mirror 1, and then passes through the beam expander objective to reach the measured reflector. The measured reflector returns the laser to the original path, and the returned laser is vertically incident on the beam splitting cemented prism and is split on the beam splitting surface B. The reflected light is reflected by the beam splitting surface B and is split again on the beam splitting surface A. The reflected light formed by the second split is reflected by the beam splitting surface A and reaches the PSD position sensor. The transmitted light is transmitted by the beam splitting surface A and reaches the CCD detector. The PSD position sensor and the CCD detector calculate the angle change value of the measured reflector based on the laser displacement caused by the angle change of the measured reflector.

2. A high-precision coaxial autocollimator optical system according to claim 1, characterized in that: The focal length of the beam expander objective lens is 1200 mm, the focal length of the beam expander eyepiece is 40 mm, and the beam expander objective lens and the beam expander eyepiece are combined into a 30x beam expander system.

3. The high-precision coaxial autocollimator optical system according to claim 1, characterized in that: The beam expander objective lens includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged in sequence along the incident direction of light, where the incident direction of light is the incident direction of light reflected from the measured reflector; The beam expander eyepiece includes a sixth lens, a seventh lens, and an eighth lens arranged in sequence along the incident direction of light, where the incident direction of light is the incident direction of light reflected from the measured reflector; The first lens has positive refractive power, is convex in the direction of incident light, and is concave in the opposite direction of incident light; The second lens has negative optical power, is convex in the direction of incident light, and is concave in the opposite direction of incident light; The third lens has positive refractive power, is convex in the direction of incident light, and is flat in the opposite direction of incident light; The fourth lens has negative optical power and is concave in the direction of incident light and concave in the opposite direction of incident light. The fifth lens has positive refractive power and is convex in the direction of incident light and convex in the opposite direction of incident light; The second lens and the third lens are tightly bonded together, and the fourth lens and the fifth lens are tightly bonded together. The sixth lens has negative optical power, is concave in the direction of incident light, and is convex in the opposite direction of incident light; The seventh lens has negative optical power, is concave in the direction of incident light, and is flat in the opposite direction of incident light; The eighth lens has negative optical power, is concave in the direction of incident light, and is convex in the opposite direction of incident light.

4. The high-precision coaxial autocollimator optical system according to claim 3, characterized in that: The curvature radii of the surfaces of the first to eighth lenses in the direction of incident light are R1 to R8, respectively. The curvature radii of the surfaces of the first to eighth lenses in the direction opposite to the direction of incident light are R1′ to R8′, respectively. The incident direction of light is the direction of incident light reflected from the reflector to be measured, and the following conditions are met: 120mm<R1<130mm, 350mm<R1′<370mm; 350mm<R2<430mm, 65mm<R2′<75mm; 65mm<R3<75mm, R3′=∞; -120mm<R4<-140mm, 120mm<R4′<140mm; 120mm<R5<140mm, -800mm<R5′<-600mm; -60mm<R6<-30mm, -30mm<R6′<-20mm; -40mm<R7<-20mm, R7′=∞; -40mm<R8<-15mm, -50mm<R8′<-30mm.

5. The high-precision coaxial autocollimator optical system according to claim 3, characterized in that: The refractive index of the glass material used for the first to eighth lenses ranges from n1 to n8, and the Abbe number of the glass material used for the first to eighth lenses ranges from v1 to v8, satisfying the following optical conditions: 1.48<n1<1.60, 60<v1<65; 1.75<n2<1.85, 30<v2<40; 1.60<n3<1.65, 55<v3<60; 1.70<n4<1.80, 25<v4<30; 1.90<n5<1.95, 15<v5<25; 1.85<n6<1.95, 15<v6<20; 1.55<n7<1.65, 50<v7<60; 1.75<n8<1.85, 33<v8<38.

6. The high-precision coaxial autocollimator optical system according to claim 3, characterized in that: The glass thicknesses of the first to eighth lenses are L1 to L8, respectively, and meet the following conditions: 14mm<L1<16mm; 5.5mm<L2<6mm; 16mm<L3<21mm; 4.5mm<L4<5mm; 9mm<L5<11mm; 2.5mm<L6<3mm; 1.8mm<L7<2.2mm; 1.8mm<L8<2.2mm.

7. The high-precision coaxial autocollimator optical system according to claim 3, characterized in that: The air gap between the first lens and the second lens is 70~80mm, the air gap between the third lens and the fourth lens is 60~65mm, the air gap between the fifth lens and the plane reflector 1 is 90~110mm, the air gap between the plane reflector 1 and the plane reflector 2 is 180~200mm, the air gap between the plane reflector 2 and the beam splitting and cemented prism is 100~120mm, the air gap between the beam splitting and cemented prism and the PSD position sensor is 65mm, the air gap between the beam splitting and cemented prism and the CCD detector is 38mm, the air gap between the beam splitting and cemented prism and the pinhole aperture is 15~17mm, the air gap between the pinhole aperture and the sixth lens is 16~17mm, the air gap between the sixth lens and the seventh lens is 2~3mm, the air gap between the seventh lens and the eighth lens is 3~4mm, and the air gap between the eighth lens and the laser light source is 28~35mm.

8. The high-precision coaxial autocollimator optical system according to claim 1, characterized in that: The CCD detector is a high-resolution area array detector or a high-frame-rate linear array CCD.

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