Laser collimation device and method of assembling same

Abstract

The application relates to the field of laser collimation technology, and particularly discloses a laser collimation device and an assembling and adjusting method thereof; the laser collimation device comprises an off-axis primary mirror, an off-axis secondary mirror, a connecting plate and an interferometer; the off-axis primary mirror is provided with a primary mirror working surface and a primary mirror connecting surface; the off-axis secondary mirror is provided with a secondary mirror working surface and a secondary mirror connecting surface; the interferometer is used for performing common reference CGH detection on the primary mirror working surface and the primary mirror connecting surface and performing common reference CGH detection on the secondary mirror working surface and the secondary mirror connecting surface during lens processing; the primary mirror connecting surface and the secondary mirror connecting surface are arranged on the two sides of the connecting plate respectively, and the primary mirror connecting surface and the secondary mirror connecting surface are parallel to each other. In the scheme, since the two surfaces of the lens are subjected to CGH detection during lens processing, it is not necessary to adjust the two-dimensional tilt freedom of the lens after installation, and the effect of reducing the assembling and adjusting quantity of the lens freedom and reducing the assembling and adjusting difficulty of the device can be achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser collimation technology, in particular to a laser collimation device and a method for assembling and adjusting the same. BACKGROUND

[0002] With the development of optical imaging and measurement into the high-definition and high-precision stage, the requirements for optical performance and environmental stability of precision instruments are also increasing. Therefore, the design of optical and mechanical structures, the processing of optical elements and the optical assembly and adjustment technology should also be continuously updated and iterated to meet the development needs of technology.

[0003] The laser collimation device is a common optical system, mainly having two structures of refractive type and reflective type, wherein the reflective optical system has the advantages of no chromatic aberration, easy processing and realization of large aperture. In addition, compared with the coaxial reflective system, the off-axis optical system has higher utilization rate of light energy because there is no central obstruction, and therefore is more suitable for laser collimation devices.

[0004] At present, the off-axis reflective imaging optical system has been widely used in high-performance space optical systems, such as the Quickbird-2 satellite payload of the United States, the Jilin-1 satellite payload and the Tianwen-1 satellite payload of China, etc. The off-axis laser collimation system similar to the above also has a wide range of application scenarios, such as off-axis laser radar and communication fields.

[0005] In the design of optical and mechanical structures, in order to meet the mechanical performance of optical elements, the design of the support structure is generally complex, and there are many components, which is not easy for structure processing and assembly.

[0006] In the optical assembly and adjustment, taking the Tianwen-1 satellite payload of the domestic space exploration satellite as an example, the optical assembly and adjustment technology of the off-axis reflective system is difficult, mainly because there are many adjustment degrees of the optical elements. In the assembly and adjustment process of the optical system, the primary mirror is used as the reference for assembly and adjustment, and then the six degrees of freedom of other optical elements are adjusted in sequence. The system needs to adjust 6(n-1) degrees of freedom (wherein n is the number of optical elements in the off-axis reflective system), which makes the assembly and adjustment work complex and increases the period of system assembly and adjustment. For the adjustment of the above degrees of freedom, please refer to the article “Tianwen-1 High-resolution Camera Main Optical Machine Online Assembly and Adjustment Technology Research” by Wang Kejun, Dong Jihong and Zhu Shiyu, etc.

[0007] Based on the above, the existing off-axis reflective laser collimation device has the problem of difficult assembly and adjustment. SUMMARY

[0008] Therefore, the purpose of the present application is to provide a laser collimation device and a method for assembling and adjusting the same, which can reduce the difficulty of assembly and adjustment of the laser collimation device.

[0009] To achieve the above technical objectives, the present application provides a first aspect of a laser collimation device, comprising: an off-axis primary mirror, an off-axis secondary mirror, a connecting plate, and an interferometer;

[0010] The off-axis primary mirror is provided with a primary mirror working surface and a primary mirror connecting surface;

[0011] The interferometer is used to perform a common reference CGH test on the primary mirror working surface and the primary mirror connecting surface during the lens processing process to ensure that the primary mirror working surface and the primary mirror connecting surface both meet the first preset surface shape requirement;

[0012] The off-axis secondary mirror is provided with a secondary mirror working surface and a secondary mirror connecting surface;

[0013] The interferometer is further used to perform a common reference CGH test on the secondary mirror working surface and the secondary mirror connecting surface during the lens processing process to ensure that the secondary mirror working surface and the secondary mirror connecting surface both meet the second preset surface shape requirement;

[0014] The primary mirror connecting surface and the secondary mirror connecting surface are respectively arranged on both sides of the connecting plate, and the primary mirror connecting surface and the secondary mirror connecting surface are parallel to each other.

[0015] Furthermore, the working surface of the primary mirror is a parabola;

[0016] The off-axis secondary mirror is a hyperbolic mirror;

[0017] The primary mirror connecting surface and the secondary mirror connecting surface are both planes.

[0018] Furthermore, in the first preset surface shape requirement, the optical axes of the primary mirror working surface and the primary mirror connecting surface are parallel, the RMS value of the primary mirror working surface is lower than 13nm, the RMS value of the primary mirror connecting surface is lower than 30nm, and the parallelism of the primary mirror connecting surface is less than 10uard;

[0019] In the second preset surface shape requirement, the optical axes of the secondary mirror working surface and the secondary mirror connecting surface are parallel, the RMS value of the secondary mirror working surface is lower than 13nm, the RMS value of the secondary mirror connecting surface is lower than 30nm and the parallelism of the secondary mirror connecting surface is less than 10uard.

[0020] Furthermore, the primary mirror connecting surface and the secondary mirror connecting surface are connected to the connecting plate by bonding.

[0021] Furthermore, the primary mirror connection surface and the secondary mirror connection surface are both connected to the connection plate via an alkaline catalytic adhesive.

[0022] Furthermore, the connecting plate, the off-axis primary mirror and the off-axis secondary mirror are all made of glass.

[0023] Further, the connecting plate, the off-axis primary mirror and the off-axis secondary mirror are all made of a low-expansion glass material with a thermal expansion coefficient less than 10 -8 m / k.

[0024] The second aspect of the present application provides a method for assembling and adjusting a laser collimation device, applied to any of the above laser collimation devices, and comprising the following steps:

[0025] During the processing of the off-axis primary mirror, the off-axis primary mirror is detected by the interferometer through CGH until the optical axis of the primary mirror working surface and the optical axis of the primary mirror connecting surface on the off-axis primary mirror are parallel to each other;

[0026] During the processing of the off-axis secondary mirror, the off-axis secondary mirror is detected by the interferometer through CGH until the optical axis of the secondary mirror working surface and the optical axis of the secondary mirror connecting surface on the off-axis secondary mirror are parallel to each other;

[0027] After the primary mirror connecting surface is bonded to one side end of the connecting plate, the secondary mirror connecting surface is bonded to the other side end of the connecting plate.

[0028] As can be seen from the above technical solutions, the present application provides a laser collimation device and a method for assembling and adjusting the same; wherein the laser collimation device comprises an off-axis primary mirror, an off-axis secondary mirror, a connecting plate and an interferometer; the off-axis primary mirror is provided with a primary mirror working surface and a primary mirror connecting surface; the interferometer is used to detect the primary mirror working surface and the primary mirror connecting surface through CGH during the processing of the lens to ensure that the primary mirror working surface and the primary mirror connecting surface both meet the first preset surface shape requirement; the off-axis secondary mirror is provided with a secondary mirror working surface and a secondary mirror connecting surface; the interferometer is used to detect the secondary mirror working surface and the secondary mirror connecting surface through CGH during the processing of the lens to ensure that the secondary mirror working surface and the secondary mirror connecting surface both meet the second preset surface shape requirement; the primary mirror connecting surface and the secondary mirror connecting surface are respectively arranged on both sides of the connecting plate, and the primary mirror connecting surface and the secondary mirror connecting surface are parallel to each other.

[0029] In this scheme, by detecting the two surfaces of the lens through CGH during the processing of the lens, it is not necessary to adjust the two-dimensional tilt freedom of the lens after installation, because the off-axis primary mirror and the off-axis secondary mirror both meet the preset requirements during the assembly and adjustment, thereby achieving the effect of reducing the number of lens freedom degrees during assembly and adjustment and reducing the difficulty of assembly and adjustment of the device. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0031] Figure 1 A schematic diagram of the structure of a laser alignment device provided in an embodiment of the present application after installation and adjustment is completed;

[0032] Figure 2 A schematic diagram of the adjustment of an off-axis primary mirror of a laser collimation device provided in an embodiment of the present application;

[0033] Figure 3 A schematic diagram of the off-axis secondary mirror adjustment of a laser collimation device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions of the embodiments of this application in conjunction with the accompanying drawings. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection requested by this application.

[0035] In the description of the embodiments of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, they should not be understood as limiting the embodiments of the present application. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance.

[0036] In the description of the embodiments of the present application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, replaceable connections, or integral connections. They can also refer to mechanical connections or electrical connections. They can also refer to direct connections or indirect connections through an intermediate medium. They can also refer to internal connections between two components. For those skilled in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0037] See also Figures 1 to 3In a first aspect, an embodiment of the present application provides a laser collimation device, comprising: an off-axis primary mirror 10, an off-axis secondary mirror 20, a connecting plate 30, and an interferometer 40. The off-axis primary mirror 10 is provided with a primary mirror working surface 11 and a primary mirror connecting surface 12; the off-axis secondary mirror 20 is provided with a secondary mirror working surface 21 and a secondary mirror connecting surface 22.

[0038] Figure 1 ] is a structural diagram of the laser alignment device provided in this embodiment after installation and adjustment; Figure 1 In the figure, the off-axis primary mirror optical axis refers to the optical axis of the primary mirror working surface 11; the off-axis secondary mirror optical axis refers to the optical axis of the secondary mirror working surface 21; and the bonding plane optical axis refers to the optical axis of the primary mirror connecting surface 12 and the secondary mirror connecting surface 22.

[0039] The interferometer 40 is used to perform a common reference CGH detection on the primary mirror working surface 11 and the primary mirror connecting surface 12 during the lens processing process to ensure that the primary mirror working surface 11 and the primary mirror connecting surface 12 both meet the first preset surface shape requirement; the interferometer 40 is also used to perform a common reference CGH detection on the secondary mirror working surface 21 and the secondary mirror connecting surface 22 during the lens processing process to ensure that the secondary mirror working surface 21 and the secondary mirror connecting surface 22 both meet the second preset surface shape requirement.

[0040] The primary mirror connection surface 12 and the secondary mirror connection surface 22 are respectively disposed on two sides of the connection plate 30 , and the primary mirror connection surface 12 and the secondary mirror connection surface 22 are parallel to each other.

[0041] In this embodiment, the interferometer 40 is used to perform common reference CGH detection on the off-axis primary mirror 10 and the off-axis secondary mirror 20 during the lens processing process, so that the CG design of the two lenses can be completed strictly in accordance with the preset requirements, and the number of degrees of freedom required for lens adjustment can be reduced during the lens adjustment after lens processing, thereby reducing the difficulty of adjusting the laser alignment device.

[0042] In the embodiment provided in the present application, the primary mirror working surface 11 is a parabola; the off-axis secondary mirror 20 is a hyperbolic mirror; and the primary mirror connecting surface 12 and the secondary mirror connecting surface 22 are both planes.

[0043] In a more specific embodiment, the first preset surface shape requirement may be: the optical axes of the primary mirror working surface 11 and the primary mirror connecting surface 12 are parallel, the RMS value of the primary mirror working surface 11 is less than 13 nm, the RMS value of the primary mirror connecting surface 12 is less than 30 nm, and the parallelism of the primary mirror connecting surface 12 is less than 10 μard;

[0044] The above-mentioned second preset surface requirement can be: the optical axes of the secondary mirror working surface 21 and the secondary mirror connecting surface 22 are parallel, the RMS value of the secondary mirror working surface 21 is lower than 13nm, the RMS value of the secondary mirror connecting surface 22 is lower than 30nm and the parallelism of the secondary mirror connecting surface 22 is less than 10uard.

[0045] Before processing the lens, a CGH working plane 41 may be designed in the CGH detection area of ​​the interferometer 40 according to the requirement of optical axis parallelism.

[0046] Taking the processing of the off-axis primary mirror 10 as an example, during the processing of the off-axis primary mirror 10, the glass blank can be processed first by optical cold processing; specifically, the optical working surface, bonding optical plane and other structural features of the off-axis primary mirror 10 can be milled and formed at one time, and the shape and position tolerances of each size are guaranteed according to normal machining precision, among which the surface accuracy of the optical working surface and the bonding optical plane reaches the micron level.

[0047] During the finishing phase, the primary mirror working surface 11 of the off-axis primary mirror 10 is ground and polished to remove the subsurface damage layer and ultimately polish the surface to an RMS value below 13 nm. Specifically, while ensuring the accuracy of geometric parameters such as the off-axis value and vertex curvature radius, the primary mirror working surface 11 is repeatedly measured and repaired using the detection area of ​​the CGH working plane 41 designed above using the interferometer 40.

[0048] After the main mirror working surface 11 is processed, since the main mirror connection surface 12 is also located in the dynamic detection range of the CGH working plane detection area, the CGH and the optical working surface are aligned at this time to detect the inclination and surface accuracy of the main mirror working surface 11, thereby ensuring that the RMS value of the processed main mirror working surface 11 is less than 30nm.

[0049] By repeatedly performing CGH detection on the primary mirror working surface 11 and the primary mirror connecting surface 12 until the CGH working plane 41 and the two optical surfaces are in alignment and the detected surface shapes of the two optical surfaces reach the expected design surface shapes, it means that the working optical surface of the off-axis primary mirror and the optical axis of the bonding surface are parallel. According to the current processing level, it can be controlled within 10μrad.

[0050] The processing and testing process of the off-axis secondary mirror 20 is the same as that of the off-axis primary mirror 10 described above, and will not be described in detail here.

[0051] Through the above-mentioned common reference CGH detection, when adjusting the lens, the off-axis primary mirror 10 can be used as a reference first, and one side end of the connecting plate 30 can be used as a bonding surface to fully contact the primary mirror connecting surface 12 of the off-axis primary mirror 10. Since both are flat and have very good optical surface shapes, they can be completely fitted together. Then, the two surfaces are pulled apart, alkaline catalytic adhesive is applied, and then reset to complete the bonding of the off-axis primary mirror 10 and the connecting plate 20.

[0052] Next, an interferometer 40 is used to build an adjustment and installation system for the off-axis primary mirror 10 and the off-axis secondary mirror 20, and the secondary mirror connection surface 22 of the off-axis secondary mirror 20 is completely attached to the other side end of the connecting plate 30. Since the processing of the off-axis secondary mirror 20 also adopts the above-mentioned CGH optical detection and processing, the optical axis of the off-axis secondary mirror 20 is now completely parallel to the optical axis of the off-axis primary mirror 10. Therefore, there is no need to adjust the two-dimensional tilt freedom of the off-axis secondary mirror 20. Therefore, the off-axis secondary mirror 20 only needs to adjust four degrees of freedom, so that the wavefront distortion measurement value of the system meets the design requirements.

[0053] During the aforementioned alignment process, the off-axis secondary mirror 20's adjustment is reduced from the traditional six dimensions to four, and the most challenging two-dimensional vertical tilt adjustment is omitted, significantly reducing the difficulty of alignment. Once the off-axis secondary mirror 20 is aligned, the two surfaces are separated, coated with alkaline-catalyzed adhesive, and then repositioned to bond the off-axis secondary mirror 20 to the connecting plate 30. This adhesive bonding method achieves permanent adhesion to the glass through a chemical bonding reaction, and the adhesive layer thickness can be controlled to the submicron level. This completes the alignment and integration of the main optical structure.

[0054] It should be noted that, in this embodiment, both the primary mirror connection surface 12 and the secondary mirror connection surface 22 are connected to the connection plate 30 via an alkaline catalytic adhesive, which can reduce damage to the lenses, while reducing the mechanical connection process and mechanical connection parts such as screws.

[0055] Optionally, the connecting plate 30 , the off-axis primary mirror 10 and the off-axis secondary mirror 20 are all made of glass.

[0056] Specifically, the connecting plate 30, the off-axis primary mirror 10 and the off-axis secondary mirror 20 are all made of a material with a thermal expansion coefficient less than 10 -8 The glass material may be made of a low expansion glass material with m / k ratio, for example, ULE fused quartz glass or grade 0 glass-ceramics.

[0057] In practical applications, existing laser alignment devices typically integrate and assemble optical lenses and metal brackets through mechanical connections such as clamps and screws, or through adhesive connections. However, because metals generally have a higher coefficient of thermal expansion and cannot fully match that of optical glass, such optical systems are significantly limited in terms of structural stability and environmental adaptability. For example, when the ambient temperature fluctuates significantly, optical systems using traditional metal and glass integration struggle to meet stringent optical performance requirements. Even when the metal is made of invar, a material with a lower coefficient of thermal expansion, or carbon fiber, these materials still cannot meet the requirements in applications requiring extremely high thermal stability, such as ultra-high precision and stability optical measurements for space gravitational wave detection.

[0058] In this embodiment, the connecting plate 30, the off-axis primary mirror 10 and the off-axis secondary mirror 20 are all made of glass. Compared with the previous structure, the optical elements and the supporting structure can be designed as an integrated whole, reducing the connection links between the optical elements and the mechanical structural parts, thereby reducing the number of parts of the laser alignment device, and further simplifying the structural design of the laser alignment device, reducing the difficulty of system integration and adjustment.

[0059] A second aspect of the present application provides a method for assembling and adjusting a laser alignment device, which is applied to any of the above-mentioned laser alignment devices and comprises the following steps:

[0060] During the processing of the off-axis primary mirror 10 , the off-axis primary mirror 10 is subjected to CGH detection by the interferometer 40 until the optical axis of the primary mirror working surface 11 and the optical axis of the primary mirror connecting surface 12 on the off-axis primary mirror 10 are parallel to each other;

[0061] During the processing of the off-axis secondary mirror 20 , the off-axis secondary mirror 20 is subjected to CGH detection by the interferometer 40 until the optical axis of the secondary mirror working surface 21 and the optical axis of the secondary mirror connecting surface 22 on the off-axis secondary mirror 20 are parallel to each other;

[0062] After the primary mirror connection surface 12 is bonded to one side end of the connection plate 30 , the secondary mirror connection surface 22 is bonded to the other side end of the connection plate 30 .

[0063] Specifically, after connecting the connecting plate 30 with the off-axis primary mirror 10 as a reference, an interferometer 40 is used to construct an adjustment and mounting system for the off-axis primary mirror 10 and the off-axis secondary mirror 20, and the secondary mirror connection surface 22 of the off-axis secondary mirror 20 is completely attached to the other side of the connecting plate 30. The installation process of the off-axis secondary mirror 20 no longer requires adjustment of the two-dimensional tilt degrees of freedom of the off-axis secondary mirror 20. Therefore, only four degrees of freedom need to be adjusted for the off-axis secondary mirror 20, enabling common reference detection and machining of the bonding surface and the optical working surface. This reduces the adjustment degrees of freedom of the optical components during assembly and mounting, thereby reducing the difficulty and cycle time of assembly and mounting.

[0064] The above are only preferred embodiments of the present application and are not intended to limit the present invention. Although the present application has been described in detail with reference to examples, those skilled in the art can still modify the technical solutions described in the aforementioned examples or make equivalent replacements for some of the technical features therein. However, any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A laser alignment device, characterized in that: include: An off-axis primary mirror (10), an off-axis secondary mirror (20), a connecting plate (30) and an interferometer (40); The off-axis primary mirror (10) is provided with a primary mirror working surface (11) and a primary mirror connecting surface (12); The interferometer (40) is used to perform a common reference CGH detection on the primary mirror working surface (11) and the primary mirror connecting surface (12) during the lens processing process, so as to ensure that the primary mirror working surface (11) and the primary mirror connecting surface (12) both meet a first preset surface shape requirement; The off-axis secondary mirror (20) is provided with a secondary mirror working surface (21) and a secondary mirror connecting surface (22); The interferometer (40) is also used to perform a common reference CGH detection on the secondary mirror working surface (21) and the secondary mirror connecting surface (22) during the lens processing process, so as to ensure that the secondary mirror working surface (21) and the secondary mirror connecting surface (22) both meet the second preset surface shape requirement; The primary mirror connection surface (12) and the secondary mirror connection surface (22) are respectively arranged on both sides of the connection plate (30), and the primary mirror connection surface (12) and the secondary mirror connection surface (22) are parallel to each other; In the first preset surface shape requirement, the optical axes of the primary mirror working surface (11) and the primary mirror connecting surface (12) are parallel, the RMS value of the primary mirror working surface (11) is lower than 13 nm, the RMS value of the primary mirror connecting surface (12) is lower than 30 nm, and the parallelism of the primary mirror connecting surface (12) is less than 10 μard; In the second preset surface shape requirement, the optical axes of the secondary mirror working surface (21) and the secondary mirror connecting surface (22) are parallel, the RMS value of the secondary mirror working surface (21) is lower than 13nm, the RMS value of the secondary mirror connecting surface (22) is lower than 30nm, and the parallelism of the secondary mirror connecting surface (22) is less than 10uard.

2. The laser alignment device according to claim 1, characterized in that: The primary mirror working surface (11) is a parabola; The off-axis secondary mirror (20) is a hyperbolic mirror; The primary mirror connection surface (12) and the secondary mirror connection surface (22) are both planes.

3. The laser alignment device according to claim 1, characterized in that: The primary mirror connection surface (12) and the secondary mirror connection surface (22) are connected to the connection plate (30) by bonding.

4. The laser alignment device according to claim 3, characterized in that: The primary mirror connection surface (12) and the secondary mirror connection surface (22) are both connected to the connection plate (30) via an alkaline catalytic adhesive.

5. The laser alignment device according to claim 1, characterized in that: The connecting plate (30), the off-axis primary mirror (10) and the off-axis secondary mirror (20) are all made of glass.

6. The laser alignment device according to claim 5, characterized in that: The connecting plate (30), the off-axis primary mirror (10) and the off-axis secondary mirror (20) are all made of a material having a thermal expansion coefficient of less than 10 -8 Made of m / k low expansion glass material.

7. A method for assembling a laser alignment device, characterized in that: The laser alignment device according to any one of claims 1 to 6 comprises the following steps: During the processing of the off-axis primary mirror (10), a CGH detection is performed on the off-axis primary mirror (10) by using an interferometer (40) until the optical axis of the primary mirror working surface (11) and the optical axis of the primary mirror connecting surface (12) on the off-axis primary mirror (10) are parallel to each other; During the processing of the off-axis secondary mirror (20), the off-axis secondary mirror (20) is subjected to CGH detection by an interferometer (40) until the optical axis of the secondary mirror working surface (21) and the optical axis of the secondary mirror connecting surface (22) on the off-axis secondary mirror (20) are parallel to each other; After the primary mirror connection surface (12) is bonded to one side end of the connection plate (30), the secondary mirror connection surface (22) is bonded to the other side end of the connection plate (30).

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