Clamping device for measuring verticality and coaxiality of lens based on double-optical-path decentration measuring instrument

Abstract

The utility model discloses a clamping device for measuring verticality and coaxiality of a lens based on a dual-optical-path decentration measuring instrument. The clamping device comprises an elastic clamp seat and an elastic clamp cap, the elastic clamp seat is detachably arranged on an adjusting platform of the dual-optical-path decentration measuring instrument; a through hole is formed in the elastic clamp seat, and a light-emitting end of a lower light path of the double-light-path decentration measuring instrument directly faces one end of the through hole of the elastic clamp seat; a to-be-tested lens is placed on the step of the boss of the elastic clamp seat; the elastic clamp cap covers the elastic clamp seat and is detachably connected with the elastic clamp seat; the top inner side supporting surface of the elastic clamp seat is in clamping contact with the cylindrical surface of the to-be-detected lens; the top inner side step of the elastic clamp seat is contacted with the edge of the lower convex surface of the to-be-measured lens. According to the device, the lens can be prevented from being damaged and protected while the lens is clamped, the cylindrical surface of the lens is ensured to be exposed, normal measurement is ensured, in the measurement process, the lens is clamped reliably, displacement or rotation is avoided, and the accuracy of a measurement result can be improved.

Description

Technical Field

[0001] The present application relates to the field of thermal imaging technology, and particularly to a clamping device for measuring the perpendicularity and coaxiality of a lens based on a double optical path center deviation measuring instrument. Background Technique

[0002] During the processing and production of optical lenses, there are differences between the actual processed lens dimensions and the design values. When the differences are too large, the lens will be scrapped. To avoid unqualified products from leaving the factory, before leaving the factory, it is necessary to detect various parameter indicators of the produced lenses to ensure that the lenses meet the design requirements.

[0003] If there is a center deviation in the lens, the optical axis of the assembled optical system is likely to deviate, causing the optical system to be unable to accurately align with the observed target and reducing the imaging performance of the optical system. This problem is particularly prominent in fields with higher requirements for optical axis accuracy, such as long-distance temperature measurement of power equipment, video security, on-site rescue, and gun sights.

[0004] In addition, for optical systems such as measuring instruments, the deviation of the lens center will also cause off-axis aberrations in the image, leading to problems such as field curvature, coma, and distortion. This makes the system unable to accurately capture the geometric shape and size of the object, affecting the measurement accuracy of the instrument.

[0005] Therefore, in the design and production of lenses, it is necessary to strictly control the center deviation of the lens to avoid further error accumulation during the subsequent assembly process. In the existing lens production process, the center deviation of the lens is mainly inspected to ensure that the center deviation of the lens to be measured (3) meets the design requirements.

[0006] According to GB / T 7242-2010 "Lens Center Deviation", the so-called lens center deviation refers to the deviation of the normal line at the centering vertex of the lens optical surface from the reference axis. The indicators characterizing the lens center deviation include: surface tilt angle χ, spherical center difference α, and eccentricity difference C.

[0007] In actual production, the center deviation of the lens is often characterized by measuring the edge equal thickness difference. Since the measuring probe needs to be in rigid contact with the lens surface when measuring the edge equal thickness difference, this method is only applicable to the control of the lens center deviation in the blank stage. Otherwise, it is easy to cause wear or damage to the smooth surface of the polished lens.

[0008] In some optical design software (such as CODE V), when evaluating the influence of the lens center deviation on the optical system performance, it is necessary to rotate and translate the lens, that is, intentionally deviate the lens from the ideal position, and then calculate the lens aberration again and compare the change of the aberration.

[0009] Rotating the lens means rotating the optical axis of the lens by a small angle with respect to the mounting reference plane, which is equivalent to tilting the optical axis of the lens with respect to the reference plane, resulting in a perpendicularity error. The perpendicularity of the reference plane (usually the trailing edge plane of the lens) to the optical axis of the lens can be used to characterize this error.

[0010] Translating the lens means moving the lens by a small value in the direction perpendicular to the optical axis, approximately resulting in a coaxiality error between the actual outer cylinder and the theoretical outer cylinder of the lens. The coaxiality of the outer cylinder of the lens to the optical axis can be used to characterize this error.

[0011] Therefore, some optical designers use perpendicularity and coaxiality to characterize the lens center deviation in the drawings. The advantage is that the measurement results of perpendicularity and coaxiality can be substituted into the rotation and translation parameters of the optical design software to accurately evaluate and predict the impact of the actual lens center deviation on the optical system. It can be seen that the two indicators of lens perpendicularity and coaxiality enrich and improve the index system of lens center deviation, providing more options for optical designers to characterize and control the lens center deviation. However, the existing measurement methods cannot accurately measure perpendicularity and coaxiality, affecting the effective use of the above method for evaluating lens center deviation.

[0012] Therefore, there is an urgent need to accurately measure the perpendicularity and coaxiality of the lens.

[0013] The control and detection technology for the center deviation of visible light optical elements mainly adopts the transmission method, and evaluates and controls the center deviation by measuring the spherical center difference and eccentricity difference. For infrared lenses, since common infrared optical materials such as germanium, silicon, and chalcogenide glasses are opaque to visible light, and the transmittance of zinc selenide and infrared-grade zinc sulfide to visible light is limited, the existing center deviation measuring instruments that must measure through visible light cannot perform transmission-type center deviation inspection on most infrared optical materials, and the development of the center deviation detection technology for infrared lenses lags behind relatively.

[0014] The double-path center deviation measuring instrument uses upper and lower optical paths to generate reflection images of the two surfaces of the lens respectively, and evaluates the lens center deviation according to the situation of the reflection images, thus breaking through the limitation that most infrared optical materials are opaque to visible light, providing the possibility for measuring the center deviation of infrared lenses. This instrument is mainly used for the detection, optical assembly and adjustment of the center deviation of lenses made of infrared optical materials (such as CN202222573192.8, CN202310841981.1). During the assembly process, it can effectively reduce the difficulty of assembly and debugging and improve the assembly and adjustment efficiency.

[0015] In the existing double-light-path center deviation measuring instrument, the attitude of the lens is mainly adjusted to make the optical axis of the lens coincide with the optical axis of the instrument. The optical axis of a single lens is the connection line of the centers of the two spherical surfaces. In theory, when the reflected images of the two surfaces of the lens completely coincide with the crosshair reticle, it means that the connection line of the centers of the two spherical surfaces of the lens (i.e., the optical axis) completely coincides with the optical axis of the measuring instrument. At this time, the runout of the trailing edge surface and the outer cylinder of the lens are measured respectively. According to the previous description, the perpendicularity and coaxiality errors of the lens to be measured (3) with respect to the optical axis are obtained.

[0016] Of course, due to the existence of errors, it is impossible to completely adjust and coincide the reflected images of the two surfaces of the lens to be measured with the crosshair reticle. It is only possible to control this error within a sufficiently small value as much as possible. This is a main source of the measurement error of this method.

[0017] In addition, the coaxiality error obtained by this method includes the roundness error of the lens to be measured itself. If the roundness error of the lens itself is too large, it will seriously affect the coaxiality measurement result of the lens. Generally, according to the measurement theory, to ensure the validity of the measurement result, it is required that the roundness error of the lens to be measured should be at least less than one-third of the coaxiality requirement.

[0018] The information disclosed in the background art section is only intended to increase the understanding of the overall background of the present utility model, and should not be regarded as an admission or any form of implication that this information constitutes the prior art already known to those of ordinary skill in the art. Summary of the Utility Model

[0019] The present application provides a clamping device for measuring the perpendicularity and coaxiality of a lens based on a double-light-path center deviation measuring instrument. This device can avoid damaging the lens while clamping the lens, protect the lens, and at the same time ensure the exposure of the cylindrical surface of the lens to ensure the normal progress of the measurement.

[0020] The present application provides a device for measuring the perpendicularity and coaxiality of a lens based on a double-light-path center deviation measuring instrument, including: an elastic fixture seat and an elastic fixture cap;

[0021] The elastic fixture seat is detachably arranged on the adjustment platform of the double-light-path center deviation measuring instrument; a through hole is arranged inside the elastic fixture seat, and the light output end of the lower light path of the double-light-path center deviation measuring instrument is arranged opposite to one end of the through hole of the elastic fixture seat;

[0022] The lens to be measured is placed on the step of the convex platform of the elastic fixture seat;

[0023] The elastic fixture cap covers the elastic fixture seat and is detachably connected to the elastic fixture seat; the inner support surface at the top of the elastic fixture seat is in clamping contact with the cylindrical surface of the lens to be measured; the inner step at the top of the elastic fixture seat is in contact with the edge of the lower convex surface of the lens to be measured.

[0024] Preferably, the elastic fixture seat includes: a base, a pedestal, and a boss; the pedestal is disposed in the central region of the base, and a boss is provided on the pedestal; a through hole penetrates through the base, the pedestal, and the boss; the lens to be measured is placed on the boss.

[0025] Preferably, on the inner wall of the upper part of the through hole provided in the boss, a support surface and a step are provided; the clearance between the support surface on the inner wall of the through hole of the boss above the pedestal and the outer circular surface of the lens to be measured is 0.05 - 0.15 mm; the width of the step is 0.5 - 1.5 mm; the height of the step is 0.5 - 2.5 mm.

[0026] Preferably, the outer circular surface of the lens to be measured exposes more than 1 mm above the top surface of the boss; the total height of the elastic fixture seat is 40 - 55 mm; the thickness of the base is 10 - 20 mm.

[0027] Preferably, the inner diameter of the step is larger than the effective aperture of the lens to be measured;

[0028] On the upper part of the boss, a support surface and a step are provided. The support surface fits against the outer circular surface of the lens to be measured, and the lower convex surface contacts the step.

[0029] Preferably, a plurality of slots are evenly distributed at the circumferential top end of the boss; the width of the slot is 1 - 2.5 mm, and the depth of the slot is 20 - 25 mm.

[0030] Preferably, the number of slots is 2E; when the aperture of the lens to be measured ≤ 30 mm, E = 3; when the aperture of the lens to be measured > 30 mm, E = 4; when the aperture of the lens to be measured increases by 20 mm each time, E increases by 1.

[0031] Preferably, the through hole provided at the center of the base has a hole diameter of Φ15 - 30 mm.

[0032] Preferably, a threaded structure is provided on the lower part of the inner wall of the elastic fixture cap, and is threadedly connected to the threaded structure provided on the outer wall of the pedestal; the tapered surface on the upper inner wall of the elastic fixture cap is press - connected to the tapered surface on the outer wall of the upper boss of the elastic fixture; the top support surface of the boss contacts the cylindrical surface of the lens to be measured.

[0033] Preferably, the height of the elastic fixture cap should match that of the elastic fixture seat;

[0034] The threaded structure on the inner wall of the elastic fixture cap should match the threaded structure on the outer wall of the pedestal of the elastic fixture seat;

[0035] The tapered surface on the inner wall of the elastic fixture cap should match the tapered surface on the outer wall of the upper boss of the elastic fixture seat.

[0036] The beneficial effects that can be produced by this application include:

[0037] 1) The clamping device for measuring the perpendicularity and coaxiality of a lens based on a double-light-path center deviation measuring instrument provided by this application can avoid damaging the lens while clamping the lens, protect the lens, and at the same time ensure the exposure of the cylindrical surface of the lens, ensuring the normal progress of the measurement. During the measurement process, the lens is clamped reliably without displacement or rotation, which can improve the accuracy of the measurement results. Description of the Drawings

[0038] Figure 1 Schematic diagram of the perpendicularity and coaxiality measurement principles in at least one embodiment provided by this application;

[0039] Figure 2 Schematic diagram of the lens to be measured in at least one embodiment provided by this application;

[0040] Figure 3 Schematic diagram of the cross-sectional front view of the elastic fixture base in at least one embodiment provided by this application;

[0041] Figure 4 Schematic diagram of the cross-sectional front view of the elastic fixture cap in at least one embodiment provided by this application;

[0042] Figure 5 Schematic diagram of the optical flat in at least one embodiment provided by this application;

[0043] Figure 6 Schematic diagram of the cross-section of the clamping device for measuring the perpendicularity and coaxiality of a lens based on a double-light-path center deviation measuring instrument in at least one embodiment provided by this application;

[0044] Figure 7 Exploded view schematic diagram of the clamping device for measuring the perpendicularity and coaxiality of a lens based on a double-light-path center deviation measuring instrument in at least one embodiment provided by this application;

[0045] Figure 8 Schematic diagram of the measurement method flow for measuring the perpendicularity and coaxiality of a lens based on a double-light-path center deviation measuring instrument in at least one embodiment provided by this application;

[0046] Legend Explanation:

[0047] Elastic fixture base 1, base 11, slot 111, boss 12, support surface 112, base 113, step 114, elastic fixture cap 2, lens to be measured 3, trailing edge surface 31, optical flat 4, screw 5, adjustment platform 41, upper light path 42, lower light path 43, horizontal adjustment knob 45, vertical adjustment knob 44. Detailed Description of the Invention

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are part of the embodiments of the present utility model, rather than all of the embodiments. The components of the embodiments of the present utility model usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0049] Therefore, the following detailed description of the embodiments of the present utility model provided in the accompanying drawings is not intended to limit the scope of the claimed present utility model, but merely represents the selected embodiments of the present utility model. Based on the embodiments in the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present utility model.

[0050] The technical means not detailed in this application and not used to solve the technical problems of this application are set according to the common general knowledge in the art, and various ways of setting common general knowledge can be implemented.

[0051] See Figures 1 to 7 , the clamping device for measuring the perpendicularity and coaxiality of a lens based on a double optical path center deviation measuring instrument provided in this application, the elastic fixture includes: an elastic fixture base 1, an elastic fixture cap 2, the elastic fixture base 1 is fixed on the adjustment platform 41 of the double optical path center deviation measuring instrument by screws 5; the lens to be measured 3 is placed on the elastic fixture base 1; the lower part of the elastic fixture cap 2 is threadedly connected to the elastic fixture base 1 by threads, and the inner wall of the upper part of the elastic fixture cap is provided with a conical surface that is press-connected to the outer wall of the convex platform on the upper part of the elastic fixture base, fixing the lens to be measured 3 on the elastic fixture base 1.

[0052] The trailing edge surface 31 of the lens to be measured 3 faces upward, the lens to be measured 3 is placed on the top support surface 112 of the convex platform 12 of the elastic fixture base 1, and the cylindrical surface of the lens to be measured 3 is in contact with it, and the lower convex surface is in contact with the step 114, and the cylindrical surface of the lens to be measured 3 is exposed. The height of the cylindrical surface exposed above the top surface of the clamping device must be greater than 1 mm. After tightening the elastic fixture cap 2, the elastic fixture base 1 contracts inward, and the convex platform 12 clamps the cylindrical surface of the lens to be measured 3. Remove the lens, then place the flat crystal 4 on the trailing edge surface 31 of the lens to be measured 3 for angle error adjustment in the vertical direction, install the lens, remove the flat crystal, and perform angle error adjustment in the horizontal direction until the angle meets the requirements. Use a micrometer to measure the runout value of the trailing edge surface of the lens to be measured as the perpendicularity of the lens, and use a micrometer to measure the 1 / 2 runout value of the cylindrical surface of the lens to be measured as the coaxiality of the lens.

[0053] Through this fixture, reliable clamping of the lens to be measured 3 can be achieved, the detection is safe and reliable, and accurate perpendicularity and coaxiality can be obtained at the same time.

[0054] In a specific embodiment, the dual - optical - path center - deviation measuring instrument used includes: an adjustment platform 41, an upper optical path 42, a lower optical path 43, a horizontal adjustment knob 45, and a vertical adjustment knob 44; the bottom of the adjustment platform 41 is provided with the vertical adjustment knob 44 and the horizontal adjustment knob 45. The vertical adjustment knob 44 is used to adjust the inclination of the adjustment platform 41; the horizontal adjustment knob 45 is used to adjust the translation of the adjustment platform 41 in the horizontal direction.

[0055] In a specific embodiment, the elastic fixture base 1 includes: a base 113, a pedestal 11, a boss 12, a step 114, and a slot 111; the pedestal 11 is arranged in the middle of the base 113, and the boss 12 is arranged on the upper part of the pedestal 11; a through - hole penetrating the base 113, the pedestal 11, and the boss 12 is opened along the central axis of the elastic fixture base 1 for clamping the lens under test 3 and allowing the test light to pass through. A threaded structure is arranged on the outer side wall of the pedestal 11. A plurality of slots 111 are evenly distributed at the circumferential top of the boss 12. A support surface 112 and a step 114 are accommodated in the through - hole of the boss 12. The top support surface 112 of the boss 12 contacts the cylindrical surface of the lens under test 3, and the inner - side step 114 at the top of the elastic fixture base 1 contacts the edge of the lower convex surface of the lens under test 3.

[0056] In a specific embodiment, a conical surface is arranged on the outer side wall of the upper part of the boss 12, which is convenient for the elastic fixture cap 2 to clamp and extrude the conical surface of the upper part of the boss 12 to apply a clamping force to the lens under test 3.

[0057] In a specific embodiment, a threaded structure is arranged on the lower part of the inner wall of the elastic fixture cap 2 and is threadedly connected to the outer side wall of the pedestal 11 of the elastic fixture base.

[0058] In a specific embodiment, a support surface 112 and a step 114 are arranged on the inner wall of the upper part of the through - hole provided in the boss 12. The clearance between the support surface 112 on the inner wall of the through - hole of the boss 12 above the pedestal 11 and the outer - circle surface of the lens under test 3 is 0.05 - 0.15 mm, and the width of the step 114 is 0.5 - 1.5 mm. Specifically, it still needs to be determined according to the effective aperture of the lens under test 3; the height of the step 114 is 0.5 - 2.5 mm, and specifically, it still needs to be determined according to the arc height of the lens under test; the inner diameter of the step 114 is larger than the effective aperture of the lens under test 3 to ensure that the surface quality of the inner surface within the effective aperture of the lens under test 3 is not damaged. With this setting, even if the surface of the lens under test 3 is accidentally scratched during operation, it can be ensured that the scratched part is outside the effective aperture of the lens under test 3 and does not affect the normal use of the lens under test 3.

[0059] In a specific embodiment, when the trailing - edge surface 31 of the lens under test 3 is placed upward on the elastic fixture base 1, the outer - circle surface of the lens under test 3 exposes more than 1 mm above the top surface of the boss 12. This is convenient for operation and avoids the problem that when the outer circle of the lens under test 3 is too little higher than the elastic fixture base 1, the dial indicator contacts the chamfer of the lens under test 3 when measuring the coaxiality, resulting in inaccurate measurement results.

[0060] In a specific embodiment, a plurality of slots 111 are evenly distributed at the circumferential top end of the boss 12; the width of the slot 111 is 1 - 2.5 mm, and the length of the slot 111 is 20 - 25 mm; the width and depth of the slot 111 increase with the increase of the diameter of the lens 3 to be measured. To achieve reliable support of the lens 3 to be measured by the boss 12. With such a setting, the elasticity of the elastic fixture can be enhanced, and the lens 3 to be measured can be easily clamped. Through the slots 111, it can be ensured that after the elastic fixture base 1 and the elastic fixture cap 2 are assembled, the top of the elastic fixture base 1 shrinks inward to generate the necessary clamping force on the lens 3 to be measured.

[0061] In a specific embodiment, the number of the slots 111 is 2E (E = 3, 4, 5,...). For example, when the diameter of the lens 3 to be measured ≤ 30 mm, E = 3; when the diameter of the lens 3 to be measured > 30 mm, E = 4; for every 20 mm increase in the diameter, E increases by 1 accordingly. For example, when the diameter of the lens 3 to be measured is 50 mm, E = 5; when the diameter of the lens 3 to be measured is 70 mm, E = 6; and so on. If the increase value of the diameter of the lens 3 to be measured is less than 20, take the value of the next lower level. For example, when the diameter of the lens 3 to be measured is 45 mm, E is 4.

[0062] The slots 111 are arranged on the boss 12 of the elastic fixture base 1. When the elastic fixture cap 2 is tightened, the slots 111 are squeezed by the conical surface of the elastic fixture cap 2, and the width of the slots becomes narrower, realizing the clamping of the lens 3 to be measured.

[0063] In a specific embodiment, the total height of the elastic fixture base 1 is 40 - 55 mm, and with the increase of the diameter of the lens 3 to be measured, the depth of the slot increases accordingly to maintain the elasticity of the elastic fixture; the thickness of the base 113 of the elastic fixture base 1 is 10 - 20 mm. Similarly, with the increase of the diameter of the lens 3 to be measured, the thickness of the base 113 of the elastic fixture base 1 increases accordingly to ensure the overall strength and stability of the elastic fixture.

[0064] In a specific embodiment, the inner diameter of the step 114 is larger than the effective diameter of the lens 3 to be measured to ensure the surface quality of the effective diameter of the lens 3 to be measured and avoid damage in this area.

[0065] In a specific embodiment, the bottom surface of the elastic fixture base 113 is ground so that the surface roughness of the base 113 is Ra1.6, the surface form accuracy is better than 0.002 mm, and the surface form is approximately concave spherical. The purpose of precisely grinding the bottom surface of the elastic fixture base 113 is not only to ensure that the elastic fixture can be firmly adsorbed on the vacuum chuck during the precise repair of the elastic fixture, but also to ensure that the elastic fixture base 1 can better fit with the adjustment platform 41 of the center deviation measuring instrument during detection. After being fixed with the screw 5, the overall elastic fixture is evenly stressed, reducing the measurement error.

[0066] In a specific embodiment, the step 114 of the elastic fixture base 1 contacts the convex edge of the lens 3 to be measured, and a 45° chamfer is formed at the contact between the step of the elastic fixture base and the lens. This can effectively remove the residual burrs during the precision machining of the step 114 and effectively avoid scratching the surface of the lens 3 to be measured when clamping the lens 3 to be measured.

[0067] In a specific embodiment, the aperture Φ of the through-hole of the through-base 113 is 15 - 30 mm. By opening the through-hole, the light after focusing in the lower optical path 43 can pass through the through-hole and irradiate on the surface of the lens 3 to be measured. The light source of the lower optical path 43 is the focused light transformed from the parallel light of the autocollimator. After passing through the through-hole, the focused light can be focused on the center of the spherical surface of the lens 3 to be measured. The reflected image of the center of the lower spherical surface passes through the central through-hole of the elastic fixture, and after being processed by the lower optical path 43, it becomes a cross image to achieve detection.

[0068] In a specific embodiment, taking the bottom surface of the ground base 113 as the reference, a high-precision CNC lathe (when conditions permit, it is recommended to use a single-point diamond machine tool) is used to complete the finish machining of the inner hole, step 114, 45° chamfer, and conical surface in one go. Ensure that the inner hole diameter and the distance from the edge to the step 114 meet the above requirements.

[0069] The finish machining of the inner hole, step 114, 45° chamfer, and conical surface is completed in one go by using a high-precision CNC lathe. Ensure that the clearance between the inner wall support surface 112 of the through-hole of the boss 12 above the base 11 and the outer circular surface of the lens 3 to be measured is 0.05 - 0.15 mm, the width of the step 114 is 0.5 - 1.5 mm, and specifically, it needs to be determined according to the effective aperture of the lens 3 to be measured; the height of the step 114 is 0.5 - 2.5 mm, and specifically, it needs to be determined according to the arc height of the lens to be measured; the inner diameter of the step 114 is larger than the effective aperture of the lens 3 to be measured to ensure that the inner surface quality within the effective aperture of the lens 3 to be measured is not damaged. Precision machining the elastic fixture base 1 can effectively improve the accuracy of the elastic fixture, reduce the adjustment difficulty, improve the detection efficiency and the accuracy of the measurement result, and reduce the measurement error.

[0070] In a specific embodiment, multiple countersunk screw holes are provided on the base 113, and the screw 5 is used to connect with the mounting hole of the measuring instrument adjustment platform 41. The screw 5 used is M4. Drilling M4 countersunk screw holes on the base of the elastic fixture base 1 is to not limit the length of the screw. In principle, a shorter screw is used to ensure that the elastic fixture can be fixed well, which can effectively save the clamping time and improve the detection efficiency.

[0071] In a specific embodiment, the elastic fixture cap 2 is connected to the elastic fixture base 1 by threads, and its threads, conical surface, and height should match the elastic fixture base 1, which can ensure uniform force when clamping the lens 3 to be measured and effectively reduce the risk of dark injury due to uneven force for some special materials such as fluoride and chalcogenide glass.

[0072] In a specific embodiment, the mating conical surface and connecting thread of the elastic fixture base 1 and the elastic fixture cap 2 need to be ground with emery to ensure sufficient and good contact. When in use, lubricating oil can be applied to the conical surface and the thread to ensure smooth operation without jamming when the elastic fixture cap 2 is tightened.

[0073] Grinding the conical surface and connecting thread of the elastic fixture base 1 and the elastic fixture cap 2, applying lubricating oil at the mating part and performing polishing can effectively enhance the fit between the elastic fixture base 1 and the elastic fixture cap 2, remove burrs, and avoid jamming of the elastic fixture base 1 and the elastic fixture cap 2 when the lens 3 to be measured is stressed during clamping.

[0074] In a specific embodiment, knurling is provided on the outer side wall of the base of the elastic fixture base 1 and the outer side wall of the elastic fixture cap 2 to increase the friction force and facilitate operation. It can increase the friction force when clamping the lens 3 to be measured, and can clamp the lens 3 to be measured more easily, improving the clamping efficiency.

[0075] In a specific embodiment, the diameter of the optical flat 4 is larger than the outer diameter of the lens 3 to be measured. The diameter of the optical flat 4 ranges from 40 to 200 mm, and the thickness of the optical flat 4 is 4 to 14 mm, and the value satisfies the requirement of the diameter-thickness ratio (diameter: thickness) = 10 to 15:1.

[0076] In a specific embodiment, the material used for the optical flat 4 is K9 glass or a visible light transmitting material with physical and chemical properties superior to K9 glass; the surface finish of the optical flat 4 is: grade V, and the parallelism difference between the two surfaces ≤ 5".

[0077] In a specific embodiment, when the diameter of the optical flat 4 ≤ 100 mm, the aperture N of the surface shape of the optical flat 4 ≤ 3, the local aperture △N ≤ 1, and the local aperture △N within the central 50 mm area of the optical flat 4 ≤ 0.5;

[0078] When the diameter of the optical flat 4 > 100 mm, the aperture N of the surface shape of the optical flat 4 is required to be ≤ 4, the local aperture △N ≤ 1, the local aperture △N within the central 50 mm area of the optical flat 4 ≤ 0.5, and the diameter of the optical flat 4 is larger than the outer diameter of the lens 3 to be measured. Setting the area within the central 50 mm of the optical flat 4 in this way can improve the accuracy of the test results.

[0079] Controlling the optical flat 4 with the above technical indicators can ensure that the reflected images generated on the upper and lower surfaces of the optical flat 4 completely coincide, obtain a clear, thin and bright cross image, have a small measurement error, and improve the calibration speed.

[0080] In a specific embodiment, for the micrometer used to measure the trailing edge surface 31 and the outer cylinder runout of the lens 3 to be measured, the measurement accuracy should not be lower than 1 μm.

[0081] In a specific embodiment, the elastic fixture cap 2 includes: a cylinder body; a threaded structure is provided on the inner side wall of the lower part of the cylinder body, and this threaded structure is threadedly connected to the threaded structure on the outer side wall of the base 11 of the elastic fixture seat 1. A through hole is provided inside the cylinder body, and the conical surface of the upper inner side wall of the cylinder body presses against the conical surface area of the convex platform 12 of the elastic fixture seat to fix the lens 3 to be measured.

[0082] See Figure 8 , the above-mentioned detection method for measuring the perpendicularity and coaxiality of a lens based on a double-light-path center deviation measuring instrument includes the following steps:

[0083] Step S1: According to the structural parameters (aperture, curvature radii of the two surfaces) of the lens 3 to be measured, select and install the lenses of the upper light path 42 and the lower light path 43 that match the lens 3 to be measured; the specific selection rules are set according to the conventional requirements of the double-light-path center deviation measuring instrument and will not be elaborated here.

[0084] Step S2: Clean the lens 3 to be measured, the optical flat 4, the elastic fixture seat 1, the elastic fixture cap 2 and the screw 5;

[0085] Step S3: Apply a small amount of lubricating oil to the conical surface and the threaded part of the elastic fixture seat 1, with the amount being such that the lubricating oil does not flow. Excess lubricating oil can be wiped off with a tissue paper;

[0086] Step S4: Fix the base 113 of the elastic fixture seat 1 on the adjustment platform 41 of the double-light-path center deviation measuring instrument with the screw 5;

[0087] Step S5: Screw the elastic fixture cap 2 onto the elastic fixture seat 1 until the elastic fixture seat 1 does not deform;

[0088] Step S6: Wear latex gloves, place the lens 3 to be measured with the concave surface facing up, align it with the inner hole of the elastic fixture, and slowly place the lens 3 to be measured vertically downward on the step 114 of the elastic fixture seat 1, ensuring that the lens 3 to be measured is in full contact with the support surface 112 and the step 114 of the elastic fixture seat 1. During the placement process, it is prohibited to rotate the lens 3 to be measured to avoid scratching the lower surface of the lens 3 to be measured.

[0089] Step S7: Rotate the elastic fixture cap 2 to tighten the elastic fixture (a toothpick can be used to pry the lens 3 to be measured to determine whether the lens 3 to be measured is clamped), to clamp the lens 3 to be measured while ensuring that the cylindrical surface of the lens 3 to be measured is exposed after clamping, and the height of the cylindrical surface exposed above the top surface of the clamping device must be greater than 1 mm.

[0090] Step S8: Move the upper light path 42 and the lower light path 43 of the measuring instrument respectively to find the reflection images of the upper and lower surfaces of the lens 3 to be measured, adjust the light source to make the reflection images have appropriate brightness, and finely adjust the distances between the lenses of the upper light path 42 and the lower light path 43 and the lens 3 to be measured to form clear reflection images;

[0091] Step S9: Place the optical flat 4 on the trailing edge surface 31 of the lens 3 to be measured. Remove the lens of the upper optical path 42, adjust the light source until a clear cross cursor appears on the display interface, rotate the adjustment platform 41, and adjust it by turning the vertical adjustment knob 44 on the adjustment platform 41 until the angular error on the display interface is within 2".

[0092] Step S10: Remove the optical flat 4, reinstall the lens back into the upper optical path 42, input the curvature radii of the upper and lower surfaces of the lens 3 to be measured and the lens parameters, adjust the horizontal adjustment knob 45 of the adjustment platform 41, and obtain the angular errors β of the upper and lower surfaces of the lens 3 to be measured through the double - optical - path centering deviation measuring instrument.

[0093] If the angular error β does not meet the requirements, the vertical adjustment knob 44 and the horizontal adjustment knob 45 need to be adjusted until the β angle meets the requirements. The value of the β angle meets the requirements in Table 1.

[0094] Table 1 Range of values of the angular error β

[0095]

[0096]

[0097] Step S11: Bring the dial indicator probe into contact with the trailing edge surface 31 of the lens 3 to be measured, rotate the adjustment platform 41, observe and record the range of values of the trailing edge surface 31, which is the run - out value of the trailing edge surface 31, and this run - out value is the perpendicularity of the lens 3 to be measured; bring the dial indicator probe into contact with the cylindrical surface of the lens 3 to be measured, rotate the adjustment platform 41, observe and record the range of values of the cylindrical surface, which is the outer - circle run - out value, and half of the outer - circle run - out value is the coaxiality of the lens 3 to be measured.

[0098] In this application, the run - out value refers to the difference obtained by subtracting the minimum value from the maximum value among the values displayed on the dial indicator during the measurement process.

[0099] Step S12: Repeat Step 11, measure the perpendicularity and coaxiality of the lens 3 to be measured at least 3 times or more, and calculate the average values of the perpendicularity and coaxiality. The results are the perpendicularity and coaxiality of the lens 3 to be measured, and record the measurement results.

[0100] Step S13: Loosen the elastic clamp cap 2, hold the exposed part of the lens 3 to be measured with fingers, slowly take out the lens 3 vertically upward, place it in a clean and dry container, and the measurement is completed.

[0101] This method takes the optical axis as the reference to unify the measurement reference with the design reference and the assembly reference, so as to obtain accurate detection results of the perpendicularity and coaxiality of the lens 3 to be measured. This method not only enriches and improves the index system of lens centering deviation, providing more options for optical designers to characterize and control lens centering deviation. It also enables optical designers to substitute the actual measurement results of perpendicularity and coaxiality back into the optical design software to quantitatively predict and evaluate the impact of lens centering deviation on the optical system, which is beneficial to improving the assembly quality of infrared optical systems.

[0102] In a specific embodiment, if, according to the detection requirements, after the test in step S13, it is still necessary to measure the same lens 3 to be measured, only need to re-place the lens 3 to be measured. Just operate according to steps 5 to 13 of this step.

[0103] In a specific embodiment, after the measurement, remove the lens 3 to be measured and place it in a container in the designated area. Remove the entire clamping device and store it in a dry and clean environment for standby.

[0104] In a specific embodiment, when the edge thickness of the lens 3 to be measured is less than 1.5 mm, only the perpendicularity can be detected, and the coaxiality cannot be detected.

[0105] In a specific embodiment, the lens 3 to be measured is a lens made of chalcogenide glass. Due to the particularity of the material, it is relatively easy to be scratched, and a micrometer with a ruby head is used for measurement.

[0106] In a specific embodiment, this detection method is applicable to accurately detecting the perpendicularity and coaxiality of lenses with various structural forms.

[0107] In a specific embodiment, when the lens 3 to be measured is a biconvex lens or a plano-convex lens, only the coaxiality of the lens can be detected, and the perpendicularity cannot be detected.

[0108] Embodiment

[0109] In this embodiment, the lens 3 to be measured is a germanium infrared lens, with a diameter of Φ48 mm, a central thickness of 7 mm, an edge thickness of 3.87 mm, and an effective aperture D 01＝ 44.6 / D 01＝ 37.4 mm, and the specific dimensional structure is as Figure 2 shown. The convex surface R1 of the lens 3 to be measured has an aspherical surface with a curvature radius of R70.9 mm, and the other side is a concave surface R2 with a curvature radius of R75.47 mm. The requirements for perpendicularity and coaxiality are: ⊥ = 0.02 mm, ◎ = 0.03 mm.

[0110] Based on the material, shape, and effective aperture of the lens, it is calculated that: the width of the step of the elastic fixture base 1 is 1 mm and the depth is 2.5 mm. At this time, the outer circle of the lens 3 to be measured is 2.15 mm higher than the outer circle of the elastic fixture. Slots are cut at the elastic fixture boss 12, the width of the slot is 2 mm, and the depth is 20 mm. The number of slots is 8 (evenly distributed); the thickness of the elastic fixture base is 8 mm; the height of the elastic fixture base is 46 mm. According to the lens aperture of 48 mm, the selected optical flat 4 has an aperture of Ф60 mm and a thickness of 6 mm, which is the best.

[0111] The elastic fixture base 1 is machined according to the design results, as Figure 3 shown. The clamping device includes: the elastic fixture base 1 as shown in Figure 3 , the elastic fixture cap 2 (as shown in Figure 4 ), the optical flat 4, and the screw 5 (as shown in Figure 5 ), and the three-dimensional schematic diagram of the clamping device (as shown in Figure 6 ).

[0112] During the measurement process, in order to achieve the measurement of perpendicularity and coaxiality, the clamping device with the aforementioned structure is adopted, and the assembled structure is shown in Figure 6, a ground and refined clamping device (elastic fixture) is used to protect the lens 3 to be measured and improve the fit between the elastic fixture base 1 and the elastic fixture cap 2. Fix the elastic fixture on the adjustment platform 41 with an M4 screw 5, and keep the elastic fixture base 1 and the elastic fixture cap 2 in a loose state; hold the outer circle of the lens 3 to be measured with both hands, align it with the elastic fixture, and slowly place the lens 3 to be measured vertically downward into the elastic fixture, ensuring that the top inner support surface 112 of the elastic fixture base 1 and the cylindrical surface of the lens 3 to be measured are in clamping contact, and the step 114 contacts the edge of the lower convex surface of the lens 3 to be measured. Rotate the elastic fixture cap 2 to tighten the elastic fixture. When tightening the elastic fixture, pay attention to preventing the lens 3 to be measured from rotating, and finally clamp the outer circle of the lens 3 to be measured. Place a flat crystal 4 with a diameter of Ф60 on the trailing edge surface 31 of the lens to calibrate the vertical tilt of the lens 3 to be measured. Remove the flat crystal 4, reinstall the lens back into the upper optical path 42, input the curvature radii of the upper and lower surfaces of the lens 3 to be measured and the lens parameters, and obtain the angular error β≤5" of the upper and lower surfaces of the lens 3 to be measured through a double optical path center deviation measuring instrument. Contact the probe of the dial indicator with the trailing edge surface 31 of the lens 3 to be measured, rotate the adjustment platform 41, and observe and record the value change range of the trailing edge surface 31, which is the runout value of the trailing edge surface 31, and this runout value is the perpendicularity of the lens 3 to be measured; contact the probe of the dial indicator with the cylindrical surface of the lens 3 to be measured, rotate the adjustment platform 41, and observe and record the value change range of the cylindrical surface, which is the outer circle runout value, and half of the outer circle runout value is the coaxiality of the lens 3 to be measured. Measure the perpendicularity and coaxiality of the lens 3 to be measured at least 3 times or more, and calculate the average value of the perpendicularity and coaxiality. The result is the perpendicularity and coaxiality of the lens 3 to be measured, and record the measurement result. The measurement result verified by the flat crystal 4 has high repeatability and accuracy. The 10-time repeatability measurement results of the perpendicularity and coaxiality are shown in the following table:

[0113] Table 2 Repeatability Measurement Record Table of Perpendicularity and Coaxiality

[0114]

[0115] As can be seen from the above table, when repeatedly detecting the perpendicularity and coaxiality of the same lens multiple times, the deviation of each measurement result from the average value of the 10 measurements does not exceed 0.0025 mm, and the technical requirements for perpendicularity and coaxiality are generally between 0.02 and 0.04 mm. Therefore, it can be considered that the measurement result of this method has high repeatability. When using this method to detect the perpendicularity and coaxiality of the lens, the result is relatively accurate.

[0116] Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A clamping device for measuring the perpendicularity and coaxiality of a lens based on a double-light-path center deviation measuring instrument, characterized in that, Including: Elastic fixture base (1), elastic fixture cap (2); The elastic fixture base (1) is detachably arranged on the adjustment platform (41) of the double-path center deviation measuring instrument; a through hole is arranged in the elastic fixture base (1), and the light-emitting end of the lower optical path (43) of the double-path center deviation measuring instrument is arranged facing one end of the through hole of the elastic fixture base (1); The lens to be measured (3) is placed on the step (114) of the boss (12) of the elastic fixture base (1); The elastic fixture cap (2) covers the elastic fixture base (1) and is detachably connected to the elastic fixture base (1); the inner support surface (112) at the top of the elastic fixture base (1) is in clamping contact with the cylindrical surface of the lens to be measured (3); the inner step (114) at the top of the elastic fixture base (1) is in contact with the edge of the lower convex surface of the lens to be measured (3).

2. The device according to claim 1, wherein The elastic fixture base (1) includes: a base (113), a base (11), and a boss (12); the base (11) is arranged in the central area of the base (113), and a boss (12) is arranged on the base (11); the through hole penetrates through the base (113), the base (11), and the boss (12); the lens to be measured (3) is placed on the boss (12).

3. The device according to claim 1, wherein A support surface (112) and a step (114) are arranged on the inner wall of the upper part of the through hole provided in the boss (12); the clearance between the inner wall support surface (112) of the through hole of the boss (12) above the base (11) and the outer circle surface of the lens to be measured (3) is 0.05 - 0.15 mm; the width of the step (114) is 0.5 - 1.5 mm; the height of the step (114) is 0.5 - 2.5 mm.

4. The device according to claim 1, characterized in that The outer circle surface of the lens to be measured (3) exposes more than 1 mm above the top surface of the boss (12); the total height of the elastic fixture base (1) is 40 - 55 mm; the thickness of the base (113) is 10 - 20 mm.

5. The device according to claim 1, characterized in that The inner diameter of the step (114) is larger than the effective aperture of the lens to be measured (3); The upper part of the boss (12) is provided with a support surface (112) and a step (114), the support surface (112) fits the outer circle surface of the lens to be measured (3), and the lower convex surface is in contact with the step (114).

6. The device according to claim 1, characterized in that, A plurality of slots (111) are evenly distributed at the circumferential top of the boss (12); the slot width of the slots (111) is 1 - 2.5 mm, and the depth of the slots (111) is 20 - 25 mm.

7. The device according to claim 6, characterized in that, The number of slots (111) is 2E; when the aperture of the lens to be measured (3) ≤ 30 mm, E = 3; when the aperture of the lens to be measured (3) > 30 mm, E = 4; when the aperture of the lens to be measured (3) increases by 20 mm each time, E increases by 1.

8. The device according to claim 1, characterized in that A through hole is arranged at the center of the base (113), and the aperture is Φ15 - 30 mm.

9. The device according to claim 1, characterized in that, The lower part of the inner wall of the elastic fixture cap (2) is provided with a threaded structure, which is threadedly connected to the threaded structure arranged on the outer wall of the base (11); the conical surface of the upper part of the inner wall of the elastic fixture cap (2) is press-connected to the conical surface of the outer wall of the upper boss (12) of the elastic fixture; the top support surface (112) of the boss (12) is in contact with the cylindrical surface of the lens to be measured (3).

10. The device according to claim 1, characterized in that The height of the elastic fixture cap (2) should match that of the elastic fixture base (1); The threaded structure of the inner wall of the elastic fixture cap (2) should match the threaded structure of the outer wall of the base (11) of the elastic fixture base (1); The conical surface on the inner wall of the elastic fixture cap (2) should match the conical surface on the outer wall of the upper boss (12) of the elastic fixture base (1).

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