High-precision assembling device and method for miniaturized reverse cassegrain objective lens
By optimizing the structure and assembly scheme of Schwarzschild objectives, utilizing the self-centering of the spherical stage and the adjustment of the rubber pads, and eliminating the multi-degree-of-freedom fine-tuning structure, the problem of large size and difficulty in integration of traditional Schwarzschild objectives has been solved, achieving miniaturization and high surface accuracy, and broadening the application fields.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HEFEI INSTITUTE OF PHYSICAL SCIENCE CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2026-06-01
- Publication Date
- 2026-07-24
AI Technical Summary
Traditional Schwarzschild objectives are large in size due to the need for multi-degree-of-freedom fine-tuning structures, making them difficult to integrate into small optical and mechanical devices and difficult to achieve high surface accuracy.
By optimizing the objective lens structure and assembly scheme, and using components such as the lens group, primary lens barrel, primary lens gasket, primary lens retaining ring, objective lens connector, secondary lens gasket, secondary lens mount, and secondary lens retaining ring, high surface accuracy is achieved by utilizing the self-centering of the spherical stage and the adjustment of the rubber pads, eliminating the multi-degree-of-freedom fine-tuning structure.
It effectively reduces the size of Schwarzschild objectives, improves surface accuracy, facilitates integration into miniaturized devices, and features a simple structure, convenient assembly and adjustment, and low cost.
Smart Images
Figure CN122449724A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of objective lens assembly and adjustment, specifically relating to a high-precision assembly and adjustment device and method for a miniaturized reverse Cassegrain objective lens. Background Technology
[0002] The reverse Cassegrain objective (also known as a Schwarzschild objective) is an achromatic reflective objective. Characterized by its large aperture, long focal length, and multi-band capability, it is widely used as a light-collecting element in telescopes, aerospace, and military equipment. In defect detection equipment based on scattering and fluorescence methods, large-aperture (NA) objectives are typically used to collect scattered light and fluorescence signals over a wider spatial angle to improve instrument sensitivity and resolution. Furthermore, the fluorescence wavelength range for defects using fluorescence methods is quite broad, including 350-870 nm, making Schwarzschild objectives suitable for such instruments. Reflective systems usually require high precision and integration, placing strict demands on the lens surface shape and overall dimensions of the objective. The Schwarzschild structure itself is not easily adjustable. To achieve high surface shape accuracy, multi-degree-of-freedom fine-tuning structures are typically added to the objective to adjust the relative positions of the primary and secondary mirrors. This also results in Schwarzschild objectives being typically large and unable to be integrated into smaller devices. Summary of the Invention
[0003] Traditional Schwarzschild objectives, to achieve high surface accuracy, typically require the integration of multi-degree-of-freedom fine-tuning mechanisms to adjust the relative positions of the primary and secondary mirrors. This results in a large overall size for Schwarzschild objectives, placing significant space requirements and hindering their application in small optical and mechanical equipment. To address these technical problems, this invention provides a miniaturized, high-surface-accuracy assembly and adjustment device and method for reverse Cassegrain objectives. By optimizing the objective structure and assembly scheme, the surface accuracy of the Schwarzschild objective is effectively improved without the need for additional fine-tuning mechanisms, while simultaneously reducing its size. This facilitates its integration into highly integrated optical and mechanical equipment such as defect detection instruments. This invention achieves the high surface accuracy requirements of Schwarzschild objectives without using multi-degree-of-freedom fine-tuning structures through optimized objective structure and installation method. This effectively reduces the size of the Schwarzschild objective, broadens its application areas, and makes it suitable for space-constrained applications.
[0004] To achieve the above objectives, the present invention adopts the following technical solution:
[0005] A high-precision assembly and adjustment device for a miniaturized reverse Cassegrain objective lens includes a lens assembly, a main lens barrel, a main lens gasket, a main lens retaining ring, an objective lens connector, an adhesive layer, a secondary lens gasket, a secondary lens mount, and a secondary lens retaining ring. The lens assembly consists of a main lens and a secondary lens. The main lens is installed inside the main lens barrel, which has a spherical platform machined inside. This spherical platform has the same radius of curvature as the main lens, and the main lens and the main lens barrel achieve line contact through the spherical platform. A main lens gasket and a main lens retaining ring are sequentially arranged on the back of the main lens. The main lens retaining ring is connected to the main lens barrel and presses the main lens gasket tightly against the back of the main lens. A side opening is provided on the main lens barrel. An adhesive injection hole is used to inject adhesive between the primary mirror and the primary microscope tube to form a primary mirror gasket. The center of the secondary mirror mount is used to install the secondary mirror, and the back of the secondary mirror is bonded to the secondary mirror mount by dispensing adhesive. The secondary mirror mount is fixed to the front end face of the primary microscope tube by a secondary mirror retaining ring. An adhesive injection hole is provided on the side of the primary microscope tube to inject adhesive between the secondary mirror mount and the primary microscope tube to form a secondary mirror gasket. A secondary mirror gasket is placed between the secondary mirror mount and the primary microscope tube, and the thickness of the secondary mirror gasket is adjustable. The objective lens connector is fixed to the outer periphery of the primary microscope tube to provide an external mechanical interface.
[0006] Furthermore, the spherical platform inside the main lens barrel and the line contact structure with the main lens enable self-centering of the main lens.
[0007] Furthermore, the primary lens pad is formed by injecting silicone rubber through the injection hole on the side of the primary lens barrel, and the number of primary lens pads is 8 to 12.
[0008] Furthermore, the primary mirror gasket and the primary mirror pressure ring are axially locked to prevent the primary mirror from becoming loose.
[0009] Furthermore, the secondary mirror mount has a circular groove machined at the position where the secondary mirror is installed. The side of the groove fits tightly with the side of the secondary mirror to ensure the alignment accuracy between the secondary mirror and the secondary mirror mount.
[0010] Furthermore, the secondary mirror gaskets are processed into a series of gaskets with a thickness interval of 20 micrometers, and the distance between the primary mirror and the secondary mirror is adjusted by replacing the secondary mirror gaskets of different thicknesses.
[0011] Furthermore, the main lens barrel, the secondary lens washer, and the secondary lens mount are respectively provided with installation angle marks for the main lens barrel, the secondary lens washer, and the secondary lens mount, which are used to confirm the installation angle between the parts during the assembly and adjustment process.
[0012] Furthermore, the effective aperture of the secondary mirror is processed to be slightly larger than its design value, so as to compensate for the tilt error between the primary mirror and the secondary mirror by sacrificing part of the effective aperture during the assembly and adjustment process.
[0013] Furthermore, the primary and secondary mirrors are made of fused silica, and the primary mirror barrel, primary mirror gasket, primary mirror pressure ring, secondary mirror gasket, secondary mirror mount, and secondary mirror pressure ring are made of titanium alloy or Invar, so that the thermal expansion coefficients of the structural components and the lens are close.
[0014] The present invention also provides a method for high-precision mounting of a miniaturized reverse Cassegrain objective lens, comprising:
[0015] Place the primary mirror tube on the center offset measuring device, using the primary mirror tube installation angle mark as the radial reference plane, and adjust the position of the primary mirror tube with a dial indicator; place the primary mirror directly into the primary mirror tube, achieving self-centering through the contact line of the spherical stage; install the secondary mirror in the secondary mirror mount, and fix it with adhesive on the back of the secondary mirror; adjust the inter-mirror distance between the primary and secondary mirrors by changing the secondary mirror gaskets of different thicknesses; adjust the eccentricity between the primary and secondary mirrors on the center offset measuring device, retaining a certain amount of eccentricity to compensate for tilt error; use a laser interferometer to measure the wavefront aberration of the objective lens system.
[0016] Beneficial effects:
[0017] 1. This invention solves the problem of achieving high surface accuracy in the assembly and adjustment of small Schwarzschild objectives.
[0018] 2. This invention eliminates the need for additional fine-tuning devices inside the objective lens, reducing the objective lens's size and making it easier to apply to miniaturized devices.
[0019] 3. The entire system of the present invention has a simple structure, is easy to assemble and adjust, and has a low cost. Attached Figure Description
[0020] Figure 1 This is a schematic diagram of the high-precision mounting device for the miniaturized reverse Cassegrain objective lens of the present invention.
[0021] Figure 2 This is a schematic diagram of the lens assembly;
[0022] Figure 3 This is a schematic diagram of the adhesive layer used for fixing.
[0023] Figure 4 This is a schematic diagram of the secondary mirror mount;
[0024] Figure 5 A schematic diagram showing the installation angle markings for the main mirror barrel and secondary mirror gaskets;
[0025] Figure 6 A schematic diagram showing the installation angle markings of the main telescope tube and the secondary telescope mount;
[0026] Figure 7A flowchart of the assembly and adjustment method of the high surface accuracy assembly and adjustment device for the miniaturized reverse Cassegrain objective lens of the present invention.
[0027] Figure 8 A schematic diagram for using a dial indicator to confirm the reference of the main tube;
[0028] Figure 9 A schematic diagram for adjusting the inter-mirror spacing;
[0029] Figure 10 A schematic diagram for adjusting mirror eccentricity;
[0030] Figure 11 This is a schematic diagram illustrating the wavelet aberration testing principle of an objective lens system.
[0031] The attached figures are labeled as follows: mirror group 1, primary mirror tube 2, primary mirror gasket 3, primary mirror retaining ring 4, objective lens connector 5, adhesive layer 6, secondary mirror gasket 7, secondary mirror mount 8, secondary mirror retaining ring 9, primary mirror 11, secondary mirror 12, radial reference plane 21, axial reference plane 22, primary mirror adhesive pad 61, secondary mirror adhesive pad 62, secondary mirror gasket mounting angle mark 71, secondary mirror mount mounting angle mark 81, laser interferometer 101, spherical reference mirror 102, and spherical reflecting mirror 103. Detailed Implementation
[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.
[0033] like Figures 1-3 As shown, the high-precision mounting device for the miniaturized reverse Cassegrain objective lens of the present invention includes a lens assembly 1, a main lens barrel 2, a main lens gasket 3, a main lens retaining ring 4, an objective lens connector 5, an adhesive layer 6, a secondary lens gasket 7, a secondary lens mount 8, and a secondary lens retaining ring 9. The lens assembly 1 includes a main lens 11 and a secondary lens 12, both of which are spherical mirrors. The main lens 11 is mounted inside the main lens barrel 2, and the two are in direct contact. A spherical platform is machined inside the main lens barrel 2, and its radius of curvature is consistent with that of the main lens 11, so that the contact line between the main lens 11 and the main lens barrel 2 lies on this spherical surface, providing a self-centering effect for the main lens. This effectively reduces the influence of the main lens tilt and eccentricity errors on the optical performance of the objective lens. The centering accuracy of the main lens is ensured by the machining accuracy of the main lens barrel and the main lens. After the primary mirror is installed into the primary mirror tube, silicone rubber is injected through the injection hole on the side of the primary mirror tube to form a primary mirror pad 61 for fixing the position of the primary mirror. A primary mirror gasket 3 and a primary mirror pressure ring 4 are installed on the back of the primary mirror to prevent the primary mirror from loosening.
[0034] The secondary mirror 12 is located at the center of the secondary mirror tube 8 and is bonded to the secondary mirror tube 8 by applying adhesive to its back. A circular groove is machined into the secondary mirror tube 8 at the mounting position as a secondary mirror mount angle mark 81. The tight fit between the side of the secondary mirror mount angle mark 81 and the side of the secondary mirror 12 ensures the alignment accuracy of the secondary mirror 12 and the secondary mirror tube 8. The secondary mirror tube 8 is fixed to the main mirror tube 2 by a secondary mirror retaining ring 9. An adhesive injection hole is machined on the side of the main mirror tube 2 to adjust the eccentricity of the secondary mirror tube 8 and the secondary mirror 12. After adjustment, adhesive is injected to form a secondary mirror pad 62 to fix the position of the secondary mirror tube 8. During machining, the effective aperture of the secondary mirror 12 should be slightly larger than its design value so that subsequent assembly and adjustment can compensate for the tilting error of the main and secondary mirrors by sacrificing a small amount of effective aperture.
[0035] This invention uses the primary lens barrel 2 as the core support structure. Internally, a spherical platform achieves self-centering through line contact with the primary lens 11. The back of the primary lens 11 is axially locked by a primary lens washer 3 and a primary lens retaining ring 4. Silicone rubber is injected through injection holes on the side to form a primary lens pad 61 for flexible fixation. The secondary lens 12 is installed at the center of the secondary lens mount 8 via adhesive dispensing on its back. A replaceable secondary lens washer 7 is provided between the outer end face of the mount and the front end face of the primary lens barrel 2 to precisely adjust the lens spacing. The secondary lens mount 8 is axially pressed against the primary lens barrel 2 by the secondary lens retaining ring 9. The secondary lens mount 8 is axially pressed against the primary lens barrel 2 by the secondary lens retaining ring 9. The gap is filled with glue to form a secondary mirror pad 62 for positioning after eccentric adjustment; the mirror assembly 1 consists of a primary mirror 11 and a secondary mirror 12 forming a coaxial reflection system. The primary mirror tube 2, the secondary mirror gasket 7, and the secondary mirror mount 8 are respectively provided with a primary mirror tube installation angle mark 21, a secondary mirror gasket installation angle mark 71, and a secondary mirror mount installation angle mark 81 for assembly and alignment. The objective lens connector 5 fixed on the outer periphery of the primary mirror tube 2 provides an external mechanical interface. The entire device achieves high-precision miniaturized integration by optimizing the structure and replacing the traditional fine adjustment mechanism with glue bonding and gasket adjustment.
[0036] A secondary mirror gasket 7 is provided between the secondary mirror tube 8 and the primary mirror tube 2. Preferably, a series of secondary mirror gaskets 7 are machined at 20μm thickness intervals. During the assembly and adjustment process, the distance between the primary and secondary mirrors is adjusted by replacing secondary mirror gaskets 7 of different thicknesses.
[0037] Preferred, such as Figure 4 , Figure 5 , Figure 6 As shown, the main lens barrel 2, the secondary lens gasket 7, and the secondary lens mount 8 are provided with the main lens barrel installation angle mark 21, the secondary lens gasket installation angle mark 71, and the secondary lens mount installation angle mark 81, which are used to confirm the installation angle between the parts during the assembly and adjustment process.
[0038] Preferably, the objective lens connector 5 provides an external mechanical interface for integrating the objective lens into an optical inspection device.
[0039] To avoid excessive thermal stress between the lens and structural components during temperature changes, which could affect the image quality of the optical system, the coefficients of thermal expansion of the structural components and the lens should be as close as possible. In one design, fused silica is used for the lens, which has a low coefficient of thermal expansion and fewer internal defects. The structural components are made of titanium alloy or Invar steel. Titanium alloy is lighter, while Invar steel has a coefficient of thermal expansion closer to that of glass.
[0040] Preferably, both the primary lens 11 and the secondary lens 12 are fixed using adhesive methods, such as highly elastic RTV adhesive. The primary lens 11 uses side-point bonding, which is easy to operate, produces a high-quality adhesive layer, and is less likely to cause severe lens misalignment due to uneven adhesive layer thickness. The number of adhesive pads per ring is 8-12. To minimize thermal stress, a heat dissipation design is required, with an adhesive layer thickness of 6mm. The calculation formula is:
[0041] ;
[0042] in, This indicates the coefficient of thermal expansion of the frame material. This indicates the coefficient of thermal expansion of the lens material. Indicates the coefficient of thermal expansion of adhesive materials. This indicates the radius of a circular optical glass. This indicates the Poisson's ratio of the adhesive.
[0043] While ensuring sufficient adhesive strength, the bonding area should be minimized as much as possible. The minimum bonding area between adhesive layer 6 and main mirror 11 is... for:
[0044] ;
[0045] In the formula, W (in N) represents the weight of the lens. (Dimensionless) represents the acceleration factor under harsh conditions, and J (in MPa) represents the tensile strength of the adhesive used. This is for the safety factor.
[0046] like Figure 7 As shown, the assembly and adjustment method of the miniaturized reverse Cassegrain objective lens high surface accuracy assembly and adjustment device of the present invention includes the following steps:
[0047] Step 1: Place the main lens barrel 2 slightly above the center, set the radial reference plane 21, and use the plane perpendicular to the radial reference plane 21 as the axial reference plane 22. Adjust the position of the main lens barrel 2 using a dial indicator (i.e., Figure 7 Install the main lens barrel slightly above the center (find the reference point), such as... Figure 8 As shown.
[0048] Step 2: Directly insert the primary lens 11 into the primary lens tube 2 (i.e., Figure 7(The primary mirror is installed into the primary mirror tube). Because the contact area between the primary mirror tube 2 and the primary mirror 11 is processed into a spherical surface, the primary mirror tube contacts the primary mirror line, which achieves a self-centering effect, and there is no need to adjust the eccentricity and tilt of the primary mirror 11.
[0049] Step 3: Install the secondary mirror 12 in the secondary mirror mount 8, and apply adhesive to the back of the secondary mirror 12 for fixation.
[0050] Step 4: Adjust the distance between the primary mirror 11 and the secondary mirror 12. The thickness d1 of the primary mirror 11 is measured during processing, and the overall thickness d2 is measured off-center. Subtracting these two values gives the distance d3 between the mirrors. Adjust the distance between the mirrors by replacing the secondary mirror gasket 7. Figure 9 As shown.
[0051] Step 5: Adjust the eccentricity of the primary mirror 11 and secondary mirror 12 slightly above the center. Since the tilt cannot be adjusted individually, a certain amount of eccentricity should be maintained between the primary mirror 11 and secondary mirror 12 to compensate for tilt errors. Figure 10 As shown.
[0052] Step 6: After assembly and adjustment, use a laser interferometer 101 to measure the wavelet aberration of the objective lens system, such as... Figure 11 As shown. A spherical reference mirror 102 is installed on the laser interferometer 101, and a spherical reflecting mirror 103 is installed on the other side of the objective lens system. By adjusting the positional relationship between the components, the wavelet aberration of the objective lens system can be measured.
[0053] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A high-precision mounting device for a miniaturized reverse Cassegrain objective lens, characterized in that, The system includes a mirror assembly, a primary mirror barrel, a primary mirror gasket, a primary mirror retaining ring, an objective lens connector, an adhesive layer, a secondary mirror gasket, a secondary mirror mount, and a secondary mirror retaining ring. The mirror assembly consists of a primary mirror and a secondary mirror. The primary mirror is installed inside the primary mirror barrel, which has a spherical platform machined inside. This spherical platform has the same radius of curvature as the primary mirror, and the primary mirror and the primary mirror barrel achieve line contact through the spherical platform. A primary mirror gasket and a primary mirror retaining ring are sequentially arranged on the back of the primary mirror. The primary mirror retaining ring is connected to the primary mirror barrel and presses the primary mirror gasket tightly against the back of the primary mirror. An adhesive injection hole is provided on the side of the primary mirror barrel, through which adhesive is injected. An adhesive is applied between the primary mirror and the primary microscope tube to form a primary mirror pad; the center of the secondary mirror mount is used to install the secondary mirror, which is bonded to the secondary mirror mount by applying adhesive to its back; the secondary mirror mount is fixed to the front end face of the primary microscope tube by a secondary mirror retaining ring; an injection hole is provided on the side of the primary microscope tube, through which adhesive is injected to form a secondary mirror pad between the secondary mirror mount and the primary microscope tube; a secondary mirror gasket is placed between the secondary mirror mount and the primary microscope tube, and the thickness of the secondary mirror gasket is adjustable; the objective lens connector is fixed to the outer periphery of the primary microscope tube to provide an external mechanical interface.
2. The high-precision mounting device for a miniaturized reverse Cassegrain objective lens according to claim 1, characterized in that, The spherical platform inside the primary lens barrel and the line contact structure with the primary lens enable self-centering of the primary lens.
3. The high-precision mounting device for a miniaturized reverse Cassegrain objective lens according to claim 1, characterized in that, The primary lens pads are formed by injecting silicone rubber through the injection hole on the side of the primary lens barrel, and the number of primary lens pads is 8 to 12.
4. The high-precision mounting device for a miniaturized reverse Cassegrain objective lens according to claim 1, characterized in that, The primary mirror gasket and the primary mirror pressure ring are axially locked to prevent the primary mirror from becoming loose.
5. The high-precision mounting device for a miniaturized reverse Cassegrain objective lens according to claim 1, characterized in that, The secondary mirror mount has a circular groove machined at the position where the secondary mirror is installed. The side of the groove fits tightly with the side of the secondary mirror to ensure the alignment accuracy between the secondary mirror and the secondary mirror mount.
6. The high-precision mounting device for a miniaturized reverse Cassegrain objective lens according to claim 1, characterized in that, The secondary mirror gaskets are manufactured in a series with a thickness interval of 20 micrometers. The distance between the primary and secondary mirrors can be adjusted by replacing the secondary mirror gaskets of different thicknesses.
7. The high-precision mounting device for a miniaturized reverse Cassegrain objective lens according to claim 1, characterized in that, The main lens barrel, the secondary lens washer, and the secondary lens mount are respectively provided with installation angle marks for the main lens barrel, the secondary lens washer, and the secondary lens mount, which are used to confirm the installation angles between the parts during the assembly and adjustment process.
8. The high-precision mounting device for a miniaturized reverse Cassegrain objective lens according to claim 1, characterized in that, The effective aperture of the secondary mirror is processed to be slightly larger than its design value, so that the tilt error between the primary mirror and the secondary mirror can be compensated by sacrificing part of the effective aperture during the assembly and adjustment process.
9. The high-precision mounting device for a miniaturized reverse Cassegrain objective lens according to claim 1, characterized in that, The primary and secondary mirrors are made of fused silica, and the primary mirror barrel, primary mirror gasket, primary mirror pressure ring, secondary mirror gasket, secondary mirror mount, and secondary mirror pressure ring are made of titanium alloy or Invar, so that the thermal expansion coefficients of the structural components and the lens are close.
10. A method for high-precision assembly and adjustment of a miniaturized reverse Cassegrain objective lens, characterized in that, A high-precision mounting device for a miniaturized reverse Cassegrain objective lens according to any one of claims 1 to 9 includes: Place the primary mirror tube on the center offset measuring device, set the radial reference plane, and adjust the position of the primary mirror tube using a dial indicator; place the primary mirror directly into the primary mirror tube, achieving self-centering through the contact line of the spherical stage; install the secondary mirror in the secondary mirror mount and fix it with adhesive on the back of the secondary mirror; adjust the inter-mirror distance between the primary and secondary mirrors by changing the secondary mirror gaskets of different thicknesses; adjust the eccentricity between the primary and secondary mirrors on the center offset measuring device, retaining a certain amount of eccentricity to compensate for tilt error; use a laser interferometer to measure the wavefront aberration of the objective lens system.