A fast-adjustable all-metal telescope objective lens and its adjustment method

Abstract

The present invention discloses a fast-adjustable all-metal telescope objective lens and an adjustment method thereof, comprising a plurality of optical elements connected to a plurality of bracket parts, and also comprising a primary mirror, a secondary mirror, a third mirror and a fourth mirror arranged in the plurality of optical elements. The debugging steps of the present invention are as follows: the first bracket part is installed on the tooling, a point source microscope device is placed on the optical axis, the second bracket part is installed with the first optical element, the second and third optical elements are installed on the second bracket part, the optical element and the bracket part are disassembled after adjustment, the second bracket part and the second optical element are reinstalled, the radial offset of the second optical element and the radial offset of the third optical element are adjusted, the tooling is removed, and the adjustment is completed. The beneficial effects of the present invention are as follows: the number of optical and mechanical parts is reduced, the optical elements can be designed in an integrated manner, the all-metal material parts simplify the assembly, are suitable for batch and standardized production, the requirements for assembly equipment are reduced, the adjustment efficiency is improved compared with the traditional telescope objective lens, and the number of adjustment iterations is effectively reduced.

Description

Technical Field

[0001] The invention relates to the technical field of optical design and optical-mechanical structure, and in particular to a fast-adjustable all-metal telescope objective lens and an adjustment method thereof. Background Art

[0002] Telescope objective lenses are a type of widely used optical lens, which have many applications in the fields of astronomy, military defense, aerospace optical remote sensing. From small civilian telephoto camera lenses to large Hubble Space Telescopes, they all belong to the category of telescope objective lenses; according to the optical elements used, telescope objective lenses can be divided into three categories: reflective, refractive, and catadioptric hybrid; according to the layout of the elements in the optical system, they can be divided into coaxial and off-axis types. Among them, coaxial reflective telescope objective lenses have the design advantages of no chromatic aberration and compact structure, and are superior to other types of telescope objective lenses in terms of cost-effectiveness, and are the most widely used in practice.

[0003] The coaxial reflective telescope objective lens originated from the telescope using spherical reflectors developed by Newton in 1618. With the application of quadratic curved reflectors, the coaxial reflective optical system has realized various aberration corrections, improved imaging quality, and enhanced the system identification ability; the use of three-reflection or even four-reflection optical systems can further improve the performance of the optical system, achieve large field of view, eliminate astigmatism, compact system structure, shorten the tube length, and reduce the weight of the instrument.

[0004] While the three-mirror and four-mirror optical systems improve the overall performance of telescope objectives, they also bring higher requirements for design, processing and installation; the compact system structure significantly increases the relative aperture and surface shape requirements of aspheric reflectors, and the cycle and cost of aspheric processing increase significantly; the multi-reflector optical structure makes the installation tolerance of each optical component more stringent, and also increases the length and complexity of the installation process, especially for large-aperture and long-focus telescope objectives, where the above problems are more prominent.

[0005] For comparison, the references: Sun Wen, Hu Jianjun, et al., Optical design of a novel two-mirror catadioptric flat-field anastigmat telescope objective [J], Infrared and Laser Engineering, 2015, 44(12): 3667-3672 and Sun Wen, Design and development of a low-cost high-resolution remote sensing camera for micro-satellites [D], Soochow University, 2015. The optical system indicators of the two-mirror catadioptric optical structure telescope objective are the same, namely, entrance pupil diameter 200mm, focal length 1400mm, F number 7. Due to the use of glass material reflector and aphotic focal compensation lens group in the optical and mechanical design, the glass reflector needs to be matched with the frame and glued and installed. The secondary mirror shape is corrected by manual polishing and repair. The wavefront of the system is corrected. The interferometer 0-position detection method is used for the assembly and adjustment of the two-mirror system. It depends on the detection equipment and the skills and processes of the processing personnel. It is expected that the standardization of aspheric reflector parts and the mass production of the whole machine cannot be achieved. The telescope objective lens needs to use titanium alloy material to match the thermal expansion coefficient of the reflector substrate glass material. The designed optical-mechanical structure weight is 11.18 kg, the structure length is 350 mm, and the diameter is 250 mm. The weight and size are far beyond the telescope objective lens that can be realized by the technical solution of the present invention. Summary of the invention

[0006] The object of the present invention is to provide a fast-adjustable all-metal telescope objective lens and an adjustment method thereof, so as to solve the problems raised in the above-mentioned background technology.

[0007] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a fast-adjustable all-metal telescope objective lens, comprising an effective optical surface primary mirror, a secondary mirror, a third mirror, a fourth mirror, a first bracket part and a second bracket part, wherein the inner edge of the primary mirror and the outer edge of the third mirror are close to each other in axial direction and have no radial overlap, and the optical and mechanical design combines the primary mirror and the third mirror into a first optical element, the fourth mirror is a second optical element, and the secondary mirror is a third optical element, the first optical element is inlaid with a detachable first spherical surface in the center hole of the third mirror, the back of the second optical element is designed with a second spherical surface with an annular aperture, and the back of the third optical element is designed with a third spherical surface, the common spherical center of the first spherical surface, the second spherical surface and the third spherical surface is located behind the third optical element on the optical axis, the first bracket part is used to install the first optical element, and the second bracket part is used to connect the first optical element, the second optical element and the third optical element.

[0008] Preferably, the first optical element, the second optical element and the third optical element simultaneously include at least one effective optical surface and an auxiliary spherical surface for adjustment, and the auxiliary spherical surface is used as an adjustment reference for the effective optical surface, and the measurement and adjustment of the center position of the auxiliary spherical surface is used to replace the measurement and adjustment of the effective optical surface.

[0009] Preferably, the first optical element, the second optical element and the third optical element comprise a plurality of auxiliary adjustment spherical surfaces, the centers of which are located at the same point, and the auxiliary adjustment spherical surfaces are reflective surfaces, and the surface shape is a spherical surface or a spherical surface with a center hole.

[0010] Preferably, the plurality of effective optical surfaces included in the first optical element, the second optical element and the third optical element are reflective surfaces, and the surface shapes are spherical surfaces, quadratic surfaces or high-order aspherical surfaces.

[0011] Preferably, the first optical element, the second optical element and the third optical element are processed by diamond single-point turning technology, and the processing coaxiality and spacing size errors of the effective optical surface and the auxiliary spherical mirror can directly meet the tolerance requirements of the optical system.

[0012] Preferably, the magnitude relationship of the curvature radii R1, R2, and R3 of the first spherical surface, the second spherical surface, and the third spherical surface is R1>R2>R3.

[0013] Preferably, the all-metal telescope objective lens that can be quickly adjusted adopts a coaxial reflective optical system.

[0014] Preferably, the materials used for the quickly adjustable all-metal telescope objective lens include, but are not limited to, aluminum alloy, magnesium alloy, chemical nickel, silicon, and ceramic glass.

[0015] Preferably, the quickly adjustable all-metal telescope objective lens is a concave-convex-concave-convex structure, and the optical surfaces of the primary mirror, secondary mirror, third mirror and fourth mirror are all aspherical surfaces, the effective aperture of the optical system is 200mm, the focal length is 1400mm, the F number is 7, the full field of view angle is 1.3°, the total weight of the optical-mechanical structure is 1.65kg, the structure length is 240mm, and the diameter is 206mm.

[0016] A method for adjusting an all-metal telescope objective lens that can be quickly adjusted comprises the following steps:

[0017] Step 1: Install the first bracket part to the tooling device, and the first optical element and the first bracket part are installed as a whole by screw connection;

[0018] Step 2: Place the point source microscope 13 on the optical axis, adjust the device position to align with the center of the first spherical surface at the center of the first optical element, focus the spherical center autocollimation image and adjust it to the center of the device image plane, the first spherical surface autocollimation image position, lock the device position, and record the first spherical surface center image and position data as the adjustment reference;

[0019] Step 3, installing the second bracket component to the first optical element;

[0020] Step 4, install the second optical element to the second bracket part, obtain the self-collimated image of the second spherical center on the back of the second optical element through a point source microscope, record the image of the second spherical center and the position data x2, y2 in units of pixel numbers, the radius size data r2, and calculate the radial offset X2, Y2, and axial offset Z2 of the second optical element in units of mm;

[0021] Step 5, install the third optical element to the second bracket part, obtain the self-collimated image of the third spherical center on the back of the third optical element through the point source microscope, record the image and position data x3, y3 of the second spherical center, radius size data r3, calculate the radial offset X3, Y3, and axial offset Z3 of the third optical element;

[0022] Step 6, disassemble the second optical element, the third optical element and the bracket parts, and use the diamond single-point turning process to repair the mounting end surface of the second bracket parts according to the axial offsets Z2 and Z3;

[0023] Step 7, reinstall the second bracket part and the second optical element, and confirm through a point source microscope that the axial offset Z1 is reduced to meet the assembly tolerance requirement;

[0024] Step eight, adjusting the radial offsets X2 and Y2 of the second optical element to meet the assembly tolerance requirements, and fixing the second optical element;

[0025] Step nine, the third optical element, using a point source microscope to measure and confirm that the axial offset Z2 is reduced to meet the assembly tolerance requirement;

[0026] Step 10, radial offsets X3 and Y3 of the third optical element are adjusted to meet assembly tolerance requirements, and the third optical element is fixed;

[0027] Step eleven, remove the tooling and the center inlay of the first optical element to complete the installation.

[0028] Beneficial Effects

[0029] The invention provides a fast-adjustable all-metal telescope objective lens and an adjustment method thereof, which reduces the number of optical and mechanical parts, enables integrated design of optical elements, and simplifies assembly of all-metal parts.

[0030] Suitable for batch and standardized production, this technical solution uses a metal aspheric reflector made by diamond single-point turning, which has better manufacturing efficiency, precision and consistency, and does not rely on the skills and experience of the processing personnel; the same metal material can be used to process optical elements and structural parts, which is convenient for realizing the passive athermalization of telescope objective optical machinery;

[0031] The requirements for installation and adjustment equipment are reduced because the optical system image quality or system wavefront measurement is not required during the installation and adjustment process, and there is no need to occupy expensive large-aperture transducers or interferometers;

[0032] The adjustment efficiency is improved compared with the traditional telescope objective lens because it does not need to glue the reflector for installation. The optical element can be assembled with high position accuracy in one time. The method of using optical imaging to measure the position of the optical element is objective and reliable, which effectively reduces the number of adjustment iterations. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the structure of the coaxial four-reflection optical system of the present invention;

[0034] Figure 2 A schematic diagram of the light envelope of the coaxial four-reflection optical system of the present invention;

[0035] Figure 3 It is a schematic diagram of the auxiliary spherical surface and the common spherical center position of the present invention;

[0036] Figure 4 It is a schematic diagram of the optical-mechanical structure of the present invention;

[0037] Figure 5 is a cross-sectional view of the optical-mechanical structure of the present invention;

[0038] Figure 6 It is a schematic diagram of the positional relationship between the optical machine and the imaging optical path and the adjustment optical path of the present invention;

[0039] Figure 7a This is a schematic diagram of the optical path of the self-collimation imaging of the spherical surface 1 of the present invention;

[0040] Figure 7b It is a schematic diagram of the optical path of the self-collimation imaging of the spherical surface 2 of the present invention;

[0041] Figure 7c This is a schematic diagram of the optical path of the spherical surface 3 self-collimation imaging of the present invention;

[0042] Figure 8 It is a schematic diagram of assembling and adjusting the data to be tested of the present invention.

[0043] Reference numerals

[0044] 1-primary mirror, 2-secondary mirror, 3-third mirror, 4-fourth mirror, 5-first optical element, 6-second optical element, 7-third optical element, 8-first spherical surface, 9-second spherical surface, 10-third spherical surface, 11-first bracket part, 12-second bracket part, 13-common spherical center, 14-point source microscope device, 15-first spherical self-collimation image, 16-image plane, 17-second spherical self-collimation image, 18-third spherical self-collimation image. DETAILED DESCRIPTION

[0045] The following are specific embodiments of the present invention, which further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0046] Example 1

[0047] The coaxial four-mirror telephoto objective lens is a concave-convex-concave-convex structure. The effective optical surfaces are primary mirror 1, secondary mirror 2, third mirror 3, and fourth mirror 4. All effective optical surfaces are aspherical. The optical system has an effective aperture of 200mm, a focal length of 1400mm, an F number of 7, a full field of view of 1.3°, a total weight of 1.65kg for the optical and mechanical structure, a structural length of 240mm, and a diameter of 206mm.

[0048] The optical system structure is as follows Figure 1 As shown, the optical path is described as follows: the light in the imaging optical path is reflected by the primary mirror 1 to the secondary mirror 2, and is reflected by the secondary mirror 2 to form an image to the primary image plane, the primary image plane is located at the center hole of the fourth mirror 4, the imaging light passes through the center hole of the fourth mirror 4 to the third mirror 3, and is then reflected by the third mirror 3 to the fourth mirror 4, and the light reflected by the fourth mirror 4 passes through the center hole of the third mirror 3 to form an image to the image plane.

[0049] like Figure 3 As shown in the light envelope of the optical system, the primary mirror 1 and the third mirror 3 are both concave. In the optical design, the inner edge of the primary mirror 1 and the outer edge of the third mirror 3 are close in axial position and have no radial overlap. In the optical-mechanical design, the primary mirror 1 and the third mirror 3 are combined into one optical element for processing. The optical element containing the primary mirror and the third mirror is the first optical element 5, the optical element with four mirrors is the second optical element 6, and the optical element with the secondary mirror 2 is the third optical element 7.

[0050] like Figure 3 As shown, the first optical element 5 is inlaid with a detachable first spherical surface 8 in the center hole of the three mirrors 3, and the first spherical surface is used as an auxiliary spherical surface for adjustment. The second optical element 6 is designed with a second spherical surface 9 with an annular aperture on the back, and the third optical element 7 is designed with a third spherical surface 10 on the back. The common center of the first spherical surface 8, the second spherical surface 9, and the third spherical surface 10 is located behind the third optical element on the optical axis. The curvature radii of the first spherical surface 8, the second spherical surface 9, and the third spherical surface 10 are R1, R2, and R3, and the size relationship is R1>R2>R3.

[0051] When the self-collimation image point of the auxiliary spherical mirror is used for optical element position measurement, the radial resolution Δdx, Δdy and the axial resolution Δdz are calculated as follows: In the formula, S pixel is the pixel size of the point source microscope, β is the lateral magnification of the optical system in the point source microscope, R 球 D is the radius of the auxiliary sphere, 球 is the effective aperture of the auxiliary sphere, and · is the multiplication operator.

[0052] like Figure 4 , 5 As shown, the parts constituting the telephoto objective lens include a first bracket part 11 and a second bracket part 12 in addition to the first optical element 5, the second optical element 6, and the third optical element 7. The first bracket part 11 is used to install the first optical element 5 and is designed with an external interface of the telephoto objective lens. The second bracket part 12 is used to install and connect the first optical element 5, the second optical element 6, and the third optical element 7. All optical elements and bracket parts are made of aluminum alloy material Al6061-T6, and effective optical surfaces, assembly spherical surfaces and installation end surfaces are processed or trimmed by diamond single-point turning, and the geometric tolerance between each surface is required to be ±1μm.

[0053] The specific system design parameters are as follows:

[0054] Imaging optical system parameters:

[0055]

[0056] Adjustment spherical parameters:

[0057] Face Name Spherical radius mm Spherical aperture The first sphere 65.00 30.00 The second sphere 116.00 37.64 The third sphere 188.16 24.00

[0058] Taking the common sphere center point as the coordinate origin and the incident direction of the light as the positive direction, the axial coordinate values ​​of the vertices of each face in the system are as follows:

[0059] Serial number Z axis coordinate mm Notes 1 0 Common center 2 64 The third spherical vertex 3 71.46 Secondary mirror vertex 4 116 Second spherical vertex 5 121.46 Four-mirror vertex 6 181.46 Primary mirror vertex 7 188.16 First spherical vertex 8 188.5 Three mirror apex

[0060] The point source microscope used has a magnification of 25 times and a detector pixel size of 2.8 μm. The calculation formulas for measuring radial resolution Δdx, Δdy and axial resolution Δdz based on the position of the optical element are: The calculated position measurement resolution of the optical element is as follows:

[0061]

[0062] Example 2

[0063] A method for quickly adjusting a telescope objective lens based on the above optical and optomechanical design is shown in the following figure: Figure 6 , the specific installation steps are as follows:

[0064] Step 1: Securely fix the optical element used as the adjustment reference in the system to the fixture;

[0065] Step 2: Place the point source microscope device on the optical axis, adjust the device position to align with the auxiliary adjustment sphere on the optical element as the adjustment reference, focus the spherical center autocollimation image and adjust it to the center of the device image plane, lock the device position, and record the optical element spherical center image and position data as the adjustment reference;

[0066] Step 3, assemble the optical elements to be assembled in sequence, obtain the self-collimated image of the center of the auxiliary spherical surface of each optical element through a fixed point source microscope, record the image data, and calculate the radial offset and axial offset of the optical element relative to the adjustment reference;

[0067] Step 4, disassembling the optical element assembled and measured in the third step, and using a diamond single-point turning process to repair the structural parts according to the axial offset;

[0068] Step 5, reinstall the optical element, measure again using the point source microscope to confirm that the axial offset is reduced to meet the assembly tolerance requirement;

[0069] Step 6, adjusting the radial offset of the optical element to meet the assembly tolerance requirement, and fixing the optical element;

[0070] Step 7: Remove the tooling and complete the adjustment. After the adjustment, the appearance of the telescope objective is as follows: Figure 4 , the cross-sectional structure is as follows Figure 5 .

[0071] The calculation method of the radial offset X, Y and axial offset Z of the optical element is: In the formula, x and y are the position data recorded in pixels, r is the radius size data, S pixel is the pixel size of the point source microscope, β is the lateral magnification of the optical system in the point source microscope, R 球 D is the radius of the auxiliary sphere, 球 is the effective aperture of the auxiliary sphere, and · is the multiplication operator.

[0072] Based on the diamond single-point turning process, the optical surface and the assembly reference spherical surface of the optical element are processed on the metal substrate, and the assembly reference spherical surface of each optical element is designed to be concentric; the diamond single-point turning process used for optical element processing enables the processing of the optical surface, the mechanical mounting surface and the assembly reference spherical surface to be completed in one clamping, and the shape and position errors between the surfaces can be ignored, thereby ensuring the accuracy of the reference transfer; during the assembly, the concentric characteristics of the assembly reference spherical surface are utilized, and the offset of the optical element is calculated by measuring the size and position of the self-collimated image of the sphere center, which is used as a reference for assembly and repair, thereby simplifying the assembly process, reducing the requirements for assembly equipment, and effectively improving the system assembly efficiency; in addition, the technical solution can also be extended to the design and assembly of off-axis optical imaging systems, and has strong practicality.

[0073] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the invention content within the protection scope of the present invention.

Claims

1. A fast-adjustable all-metal telescope objective lens adopts a coaxial reflective optical system, comprising an effective optical surface primary mirror (1), a secondary mirror (2), a third mirror (3), a fourth mirror (4), a first bracket part (11) and a second bracket part (12), characterized in that: The inner edge of the primary mirror (1) and the outer edge of the third mirror (3) are axially close and have no radial overlap. The optical machine design combines the primary mirror (1) and the third mirror (3) into a first optical element (5), the fourth mirror (4) is a second optical element (6), and the secondary mirror (2) is a third optical element (7). The first optical element (5) is inlaid with a detachable first spherical surface (8) in the center hole of the third mirror (3). The back of the second optical element (6) is designed with a second spherical surface (9) with an annular aperture. The back of the third optical element (7) is designed with a third spherical surface (10). The common spherical center (13) of the first spherical surface (8), the second spherical surface (9) and the third spherical surface (10) is located behind the third optical element (7) on the optical axis. The first bracket part (11) is used to install the first optical element (5), and the second bracket part (12) is used to connect the first optical element (5), the second optical element (6) and the third optical element (7). The first optical element is provided with a removable first spherical surface inlaid in the central hole of the three mirrors, the first spherical surface is used as an auxiliary spherical surface for adjustment, the back of the second optical element is provided with a second spherical surface with an annular aperture, and the back of the third optical element is provided with a third spherical surface, and the common spherical center of the first spherical surface, the second spherical surface and the third spherical surface is located behind the third optical element on the optical axis; The light in the imaging optical path is reflected by the primary mirror to the secondary mirror, and then reflected by the secondary mirror to form an image on the primary image plane. The primary image plane is located at the center hole of the four-mirror. The imaging light passes through the center hole of the four-mirror to the third mirror, and then is reflected by the third mirror to the fourth mirror. The light reflected by the fourth mirror passes through the center hole of the third mirror and forms an image on the image plane. When the self-collimation image point of the auxiliary spherical mirror is used for optical element position measurement, the radial resolution Δdx, Δdy and the axial resolution Δdz are calculated as follows: In the formula, S pixel is the pixel size of the point source microscope, β is the lateral magnification of the optical system in the point source microscope, R 球 D is the radius of the auxiliary sphere, 球 is the effective aperture of the auxiliary sphere, · is the multiplication operator; The first optical element (5), the second optical element (6) and the third optical element (7) simultaneously comprise at least one effective optical surface and an auxiliary spherical surface for adjustment, the auxiliary spherical surface for adjustment being used as an adjustment reference for the effective optical surface, and the measurement and adjustment of the center position of the auxiliary spherical surface is substituted for the measurement and adjustment of the effective optical surface; The effective optical surfaces included in the first optical element, the second optical element and the third optical element are reflective surfaces, and the surface shapes include one of a spherical surface, a quadratic surface or a high-order aspherical surface.

2. The all-metal telescope objective lens capable of rapid adjustment according to claim 1, characterized in that: The first optical element (5), the second optical element (6) and the third optical element (7) are processed by a diamond single-point turning process, and the processing coaxiality and spacing size errors of the effective optical surface and the auxiliary spherical mirror can directly meet the tolerance requirements of the optical system.

3. The all-metal telescope objective lens capable of rapid adjustment according to claim 1, characterized in that: The magnitude relationship of the curvature radii R1, R2, and R3 of the first spherical surface (8), the second spherical surface (9), and the third spherical surface (10) is R1>R2>R3.

4. The all-metal telescope objective lens capable of rapid adjustment according to claim 1, characterized in that: The all-metal telescopic objective lens capable of rapid adjustment adopts a coaxial reflection optical system.

5. The all-metal telescope objective lens capable of rapid adjustment according to claim 1, characterized in that: The material used for the rapidly adjustable all-metal telescope objective lens is selected from one of aluminum alloy, magnesium alloy and chemical nickel.

6. The all-metal telescope objective lens capable of rapid adjustment according to claim 1, characterized in that: The all-metal telescope objective lens that can be quickly adjusted is a concave-convex-concave-convex structure, and the optical surfaces of the primary mirror (1), the secondary mirror (2), the third mirror (3), and the fourth mirror (4) are all aspherical surfaces. The effective aperture of the optical system is 200 mm, the focal length is 1400 mm, the F number is 7, the full field angle is 1.3°, the total weight of the optical and mechanical structure is 1.65 kg, the structure length is 240 mm, and the diameter is 206 mm.

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