A compensation structure for the comprehensive error of spliced ​​detectors

Abstract

The present invention discloses a compensation structure for the comprehensive error of a spliced ​​detector, that is, discrete compensation sheets of different optical thicknesses are installed between the telescope or imaging optical system of an existing photoelectric remote sensing instrument and the spliced ​​detector. The discrete compensation sheets are optically coated according to the working band of the photoelectric instrument, and are sequentially installed between the corresponding spliced ​​detector assembly and the telescope or imaging optical system of the existing photoelectric remote sensing instrument. They can be directly fixed on the spliced ​​detector assembly, or fixed on the optical-mechanical structure of the telescope by bonding or pressing plates. The present invention can compensate for the mechanical splicing error and temperature deformation of the spliced ​​detector in the height or depth direction, correct the field curvature of a large-field telescope or optical lens, compensate for the additional optical path difference of discrete optical elements such as a spliced ​​detector window sheet or filter, reduce the difficulty of splicing large-scale spliced ​​detectors, equivalently realize the confocal plane design of the spliced ​​detector, and ensure the imaging quality of the spliced ​​detector in the full field of view.

Description

Technical Field

[0001] The present invention relates to a method and structure for compensating the comprehensive error of a spliced ​​detector of a photoelectric remote sensing instrument or an imaging instrument. The method and structure can be used to compensate for (a) mechanical splicing errors of spliced ​​detectors of a linear array or planar array optical remote sensing instrument in the height or depth direction, (b) field curvature of an imaging optical system such as a large-field telescope or an optical lens, (c) temperature deformation of the spliced ​​detector, and (d) additional optical path difference of discrete optical elements such as a window plate or a filter of a spliced ​​detector assembly, thereby reducing the difficulty of splicing large-scale spliced ​​detectors, equivalently realizing the confocal plane design of the spliced ​​detectors, and ensuring the imaging quality of the spliced ​​detectors in the full field of view. Background Art

[0002] In order to expand the coverage and resolution capability of optical remote sensing instruments and improve the temporal and spatial resolution of optoelectronic information acquisition, large-field-of-view and high-resolution optoelectronic systems have gained more and more attention and applications, and the corresponding ultra-long linear array and ultra-large area array detectors are in increasing demand. Ultra-long linear array and ultra-large area array detectors are obtained by staggered splicing of short linear arrays or small area arrays, thereby expanding the scale of detectors and achieving higher resolution and coverage of a larger observation range.

[0003] Among the commonly used large-field-of-view photoelectric remote sensing instruments, the most common form of large-scale detector implementation is the long linear array detector with a staggered arrangement in a herringbone shape. The ultra-long linear detector is achieved by splicing short linear detectors end to end and arranging them alternately in a herringbone shape, sampling at intervals on the entire image plane, which is equivalent to realizing an ultra-large-scale linear array splicing detector. For planar array detectors, a similar method can be adopted to realize an ultra-large-scale planar array splicing detector by arranging small planar array detectors in a herringbone shape or a field shape.

[0004] The visible light detector made of 17 CCDs spliced ​​together by the Changchun Institute of Optics, Fine Mechanics and Physics of the Chinese Academy of Sciences, the 2048×1 long-wave infrared detector developed by the Shanghai Institute of Technical Physics of the Chinese Academy of Sciences, as well as the US Kepler astronomical satellite, Europe's GAIA astronomical satellite, the US Advanced Land Imager ALI (Advanced Land Imager) and the multi-spectrum thermal imager MTI (Multi-spectrum Thermal Imager) have all successfully applied spliced ​​long-line detectors or spliced ​​array detectors.

[0005] For optical remote sensing instruments in low-Earth orbit, the push-broom imaging system using long-line detectors is a good way to obtain images. The large-field push-broom imaging optical remote sensing system can achieve wide ground coverage. For example, the Cook-type off-axis reflective optical system has a field of view of 20° or more, which corresponds to a ground coverage of more than 176km in a 500km low-Earth circular orbit.

[0006] Under the above conditions, assuming that each pixel corresponds to a ground resolution of 10m, the corresponding push-broom imaging optical remote sensing system requires at least 17,600 effective pixels to cover the above width, which leads to an increase in the number of pixels and splicing scale of long-line detectors. Large array detectors also have such requirements. Through the mechanical splicing of a single small array chip, an ultra-large-scale array detector is obtained to achieve high-resolution large-field imaging and obtain high-resolution ground object information within a large field of view at one time, which is beneficial to improving the spatiotemporal resolution of optoelectronic remote sensing instruments.

[0007] Long-line array and area array splicing detectors have specific requirements for splicing position accuracy. The positioning errors in the length X and width Y directions of the line array (area array) correspond to the object-image conjugate relationship of the optical camera or remote sensing system, affecting the geometric positioning accuracy. Long-line array and large area array splicing detectors use precision mechanical adjustment mechanisms to achieve high-precision adjustment and alignment of splicing modules, with an accuracy of up to μm. The existing splicing process can basically guarantee the splicing accuracy in the length X and width Y directions, and through appropriate overlapping pixel design, it can be compensated and improved in post-processing.

[0008] The stitching error in the Z (depth) direction of the linear or planar array height needs to be compensated by the focal depth of the optical system. Usually, the focal depth of the optical system is limited, and the adjustment error of the optical instrument will also affect the tolerance of the focal depth. Therefore, the existing linear or planar array stitching detectors have higher requirements for the coplanar accuracy of the stitching, and it takes a lot of cost to solve this problem.

[0009] However, as the scale of splicing expands, the coplanarity requirements for the spliced ​​sub-modules in spliced ​​detectors with a length of more than 1000mm are becoming increasingly higher, and the existing mechanical splicing technology is difficult to adapt to the increasingly larger splicing scale and precision requirements.

[0010] In addition, the materials and components of the spliced ​​base plate and the spliced ​​detectors are different, and the spliced ​​detectors are fixed to the spliced ​​base plate using a bonding interface or a mechanical connection structure. In such a spliced ​​structure, due to the influence of thermal expansion and contraction and the bimetallic effect, the influence of temperature changes and temperature gradients on the flatness of the long-line array or large-array spliced ​​structure becomes more significant, and at the order of 1000mm, the size of the long-line array or large-array spliced ​​detector increases, and the deformation and warping under the influence of temperature changes or temperature gradients are extremely significant.

[0011] For large-scale spliced ​​arrays of infrared detectors, the positions of the spliced ​​submodules are precisely adjusted under laboratory conditions to obtain the best coplanarity. However, the operating temperature of infrared detectors is usually required to be around 100K. Under such temperature field conditions, due to thermal expansion and contraction, bimetallic effect, and thermal mismatch between the detector and the substrate material, the infrared detectors spliced ​​in linear or planar arrays will be significantly deformed or warped at the operating temperature. At this time, the splicing flatness is difficult to meet the predetermined technical index requirements. In order to correct the low-temperature flatness, it is necessary to spend a lot of time, energy, and debugging costs in the cycle of normal temperature repair and low-temperature testing to improve the limited splicing accuracy.

[0012] Similarly, for large-scale spliced ​​detectors of visible light or other bands, as the number of spliced ​​modules increases, the power consumption of electronics increases and is concentrated in a certain area or range of the spliced ​​modules, resulting in significant temperature changes in the spliced ​​area. At this time, the thermal expansion and contraction caused by the thermal effect causes the coplanarity of the spliced ​​detector to deteriorate. That is, in the room temperature splicing test, certain methods and means are needed to compensate for the deformation of the spliced ​​detector under the high and low temperature thermal effects, or to compensate for the changes in the coplanarity of the spliced ​​detector caused by temperature changes and temperature gradients.

[0013] Finally, for the stitching of curved image planes, the American Kepler astronomical satellite adopted a curved image plane design. The stitched detectors used a co-curved surface stitching method. By curved image planes, the telescope or optical system was optimized to reduce the aberration of field curvature, thereby achieving a larger field of view and better quality optical lenses. At this time, new requirements were put forward for the coplanarity accuracy of the stitched detectors.

[0014] The optical system or telescope of the spliced ​​linear array or planar array detector has a large field of view. For the Schmidt telescope of the Kepler astronomical satellite, the field of view angle is 12°. In the process of correcting various aberrations, the optical lens or telescope with a large field of view also needs to correct the field curvature. A flat image plane is a strong constraint condition of the optical system, while a curved image plane can reduce the requirements for aberration optimization, thereby achieving a lightweight and compact optical system design. If the field curvature of the large field of view optical lens is not specially corrected, each spliced ​​detector should be spliced ​​into a curved image plane.

[0015] At the same time, long-line or large-array spliced ​​detectors require corresponding windows or filters for optical band selection or sealing protection. However, these discrete windows or filters undergo multiple process processing and screening, and it is difficult to achieve optically equal thickness. The resulting optical path difference of unequal thickness will also cause the sub-modules of the spliced ​​detector to not be in the optimal focal position.

[0016] In previous practice, the above stitching errors all need to be absorbed by using the focal depth of the optical system as a tolerance. The theoretical focal depth of the optical system is ±2λF2 Due to the influence of optical system processing errors, installation accuracy, etc., the focal depth margin of the optical lens is small. For visible light lenses, the central wavelength λ=0.5μm, F=10, the focal depth is about ±100μm, and for long-wave infrared lenses, the central wavelength λ=8μm, F=2, the focal depth is about ±64μm.

[0017] Based on the above analysis, although linear or planar array spliced ​​detectors solve the problem of large field of view imaging, the spliced ​​detectors themselves are also affected by (a) coplanarity errors of the spliced ​​detectors (temperature changes, mechanical splicing), (b) the influence of field curvature of the large field of view optical system, and (c) the errors caused by discrete optical elements in the spliced ​​detector assembly. The above errors need to be comprehensively compensated to give full play to the role of the spliced ​​detector.

[0018] The method and model of discrete compensation sheets described in this article can be used for comprehensive error compensation of linear and planar array spliced ​​detectors and large field of view optical systems. Discrete compensation sheets with different optical thicknesses are made using optical materials with a certain refractive index. The height error of detector splicing, the field curvature of the optical system, and the optical path difference of discrete optical elements are compensated by changing the optical thickness of the discrete compensation sheets. The confocal plane design of the spliced ​​detector is equivalently realized, thereby ensuring the imaging quality of the spliced ​​detector on the entire image plane, which is beneficial to the large field of view and high resolution application of optical remote sensing instruments and imaging instruments. Summary of the invention

[0019] According to the technical characteristics and application background of linear or planar array spliced ​​detectors, a comprehensive error compensation structure of linear or planar array detectors is proposed, that is, discrete compensation sheets with different optical thicknesses are installed between the telescope or imaging optical system of the existing optoelectronic remote sensing instrument and the spliced ​​detector.

[0020] The photosensitive elements of the linear or planar array stitched detectors are arranged in a herringbone, field or straight shape. If an independent compensation sheet can be added to each stitched detector, the stitching error of the detector, the field curvature of the optical system and the optical path difference of the discrete optical elements and other factors can be compensated and corrected through compensation sheets of different optical thicknesses, so that the optical path difference between the large-field telescope or optical lens and the corresponding long linear or planar array stitched detector sub-module is equal, it can not only reduce the difficulty of stitching detectors, but also achieve equivalent confocal plane design, while ensuring the imaging quality of the full field of view of the stitched detector.

[0021] The linear array or planar array detector integrated error compensation structure of the present invention is as shown in the attached Figure 1As shown. The discrete compensating plate 1 is a parallel plate with different optical thicknesses. The optical material of the parallel plate is selected according to the working band of the optoelectronic instrument or the spliced ​​detector, and the optical coating treatment is performed according to the working band of the optoelectronic instrument; the discrete compensating plate 1 is fixed in the compensating plate holder 3 by gluing, and the compensating plate pressing plate 2 further fixes the discrete compensating plate 1, and the compensating plate pressing plate is fixed to the compensating plate holder 3 by screws; the compensating plate holder 3 is installed on the housing or base 6 of the spliced ​​detector assembly by screws or gluing, or fixed on an optical-mechanical structure such as a telescope; the discrete window or filter 4 of the spliced ​​detector is one of the components of the spliced ​​detector, or is omitted, and the discrete compensating plate 1 is directly used to replace the function of the discrete window or filter 4.

[0022] Each photosensitive element 5 of the spliced ​​detector has an exclusive corresponding discrete compensation plate 1. The imaging light beam from the telescope or optical lens passes through the discrete compensation plate 1, through the opening of the compensation plate holder 3, or through the discrete window or filter 4 to reach the photosensitive element 5 of each spliced ​​detector in the spliced ​​detector assembly, or directly reaches the photosensitive element 5 of each spliced ​​detector in the spliced ​​detector assembly.

[0023] The above-mentioned comprehensive error compensation structure can be used for both in-line splicing detectors and planar array splicing detectors. It can be used for both planar splicing detectors and curved surface splicing detectors. The splicing detector can have either one or both of the windows and filters, or none of them.

[0024] The above compensation structure can be used in one or more combinations of detectors in the optical bands of ultraviolet, visible light, short-wave infrared, medium-wave infrared and long-wave infrared, that is, the working band of each spliced ​​detector can be the same, in which case the compensation film can be processed with the same optical coating. It can also be used in spliced ​​detectors with different working bands, that is, the submodules of the spliced ​​detector have different working bands, in which case the optical coating of the compensation film should be determined according to the corresponding working band of the spliced ​​detector.

[0025] The compensation sheet of the above compensation structure is installed in the compensation sheet holder, and can be installed by gluing or by screws + pressing plates to form a relatively independent compensation sheet assembly.

[0026] The compensation plate assembly can be directly installed on the spliced ​​detector as a part of the spliced ​​detector; it can also be installed on the telescope optomechanical structure in front of the spliced ​​detector as an external accessory of the spliced ​​detector, that is, it is transferred through parts such as the compensation plate holder. The core of the two installation methods is to maintain the relative position relationship between the discrete compensation plate and the spliced ​​detector sub-module.

[0027] A method for calculating the thickness of discrete compensation sheets

[0028] Step 1) Adjust the posture or position of the spliced ​​detector relative to the telescope or the optical-mechanical system so that the photosensitive element of each spliced ​​submodule i of the spliced ​​detector obtains the back intercept L corresponding to the best focal plane position i ;

[0029] Step 2) According to the change of the back intercept between the submodules ΔL i , divided by the refractive index n of the compensating plate i , which is the initial thickness of each compensation sheet. On this basis, the thickness d0 is uniformly increased to increase the strength of the compensation sheet and ensure the reliability of compensation sheet processing and installation. Thus, the initial thickness d of each discrete compensation sheet is obtained. i =ΔL i / n+d0;

[0030] Step 3) The compensation sheets determined in step 2) are sequentially loaded into the compensation sheet holder. Return to step 1) and repeat the above iterative process. According to the change of the back intercept of each spliced ​​submodule, the thickness of the compensation sheet is changed to make each submodule of the spliced ​​detector at the same back intercept L. f To stop the iteration.

[0031] The calculation principle and method of the thickness of the discrete compensation sheet can be found in the attached Figure 3 and Figure 4 Schematic diagram of the comprehensive error compensation structure of linear or planar array spliced ​​detectors.

[0032] The advantages of the present invention are:

[0033] 1. Simple structure and easy assembly. The discrete compensation sheet and compensation sheet holder form a module and can be assembled independently, which is conducive to the coordination with the existing long-line array or area array splicing detector;

[0034] 2. The splicing detector comprehensive error compensation structure can comprehensively compensate for various errors such as the splicing coplanarity error of the detector, the field curvature of the optical system, and the optical path difference of the discrete optical system.

[0035] (a) Compensating for the coplanar stitching error of detectors. Discrete compensation sheets of different thicknesses can match the optical path difference of each stitched detector in a linear or planar array stitched detector assembly, respectively, so that they are at their respective optimal focal plane positions, which can effectively reduce the coplanarity requirements of the linear or planar array stitched detector assembly.

[0036] (b) Compensating for the field curvature of an optical system The structure and method of the discrete compensating plate can also compensate for the field curvature of a telescope system or an optical instrument, which is equivalent to expanding the focal depth of the optical system;

[0037] (c) Compensation for optical path differences of discrete optical elements Discrete compensation sheets can also compensate for the unequal thickness errors and equal optical path differences of discrete optical elements such as discrete windows or filters of linear or planar array spliced ​​detectors.

[0038] 3. The described integrated error compensation structure of the stitched detector can also reduce the solid angle difference between the central field of view and the edge field of view of the linear or planar array stitched detector assembly, thereby limiting the stray radiation energy entering the stitched detector assembly, reducing the irradiance fluctuation of each stitched detector of the linear or planar array stitched detector assembly, improving the irradiance uniformity of the focal plane, and facilitating improving the dynamic range and detection sensitivity of the optoelectronic imaging system.

[0039] 4. The comprehensive error compensation structure of the spliced ​​detector is not only suitable for the plane splicing of long lines and large arrays, but also suitable for the curved image plane of curved surface splicing, which is beneficial to the large field of view and high resolution application of optical imaging or remote sensing instruments. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a cross-sectional view of the compensation structure corresponding to a photosensitive element of the spliced ​​detector comprehensive error compensation structure. Figure 1 In the figure, 1 is a discrete compensation sheet, 2 is a compensation sheet pressure plate, 3 is a compensation sheet holder, and 1 to 3 constitute the compensation structure. 4 is a window or filter of the spliced ​​detector assembly, 5 is a photosensitive element of the spliced ​​detector assembly, 6 is a housing or base of the spliced ​​detector, and 4 to 6 constitute a linear array or planar array spliced ​​detector assembly.

[0041] Figure 2 This is a top view of the integrated error compensation structure of the spliced ​​detector. Figure 2 The number 1 in the middle is a discrete compensation plate of different optical thickness.

[0042] Figure 3 It is a schematic diagram of the confocal plane stitching of existing stitching detectors.

[0043] Figure 4 This is the schematic diagram for calculating the thickness of the discrete compensation sheet of the spliced ​​detector. DETAILED DESCRIPTION

[0044] The following is a detailed description in conjunction with the accompanying drawings to better illustrate the structural features and functional characteristics of the present invention, rather than to limit the protection scope of the present invention.

[0045] Figure 1 and Figure 2 The components of the spliced ​​detector comprehensive error compensation structure of the present invention are identified in detail, including a discrete compensation sheet, a compensation sheet holder, a compensation sheet cover plate and a spliced ​​detector assembly.

[0046] The spliced ​​detector assembly is a product completed based on the existing splicing process. The window or filter 4 is one of the components of the spliced ​​detector, or it can be omitted. The arrangement and layout of the photosensitive elements 5 in the linear or planar array spliced ​​detector assembly are determined according to the results of the optical design or the overall design results. The shell or base 6 of the spliced ​​detector or the shell or base of the optical-mechanical system can be used as the final fixed base of the compensation plate. The thickness of the compensation plate is determined according to Figure 4 The method shown is used for design. Step 1) when the compensation sheet is not installed, the spliced ​​detector is adjusted so that each spliced ​​module i of the spliced ​​detector obtains the back intercept Li corresponding to the optimal focal plane position; Step 2) the change in the back intercept ΔLi between the submodules of the spliced ​​detector is divided by the material refractive index ni of the compensation sheet, that is, the initial thickness ΔLi / n of each compensation sheet. On this basis, the thickness d0 is uniformly increased to enhance the strength and processability of the compensation sheet and ensure the reliability of the processing and installation of the compensation sheet. Thus, the initial thickness di of each discrete compensation sheet is obtained = ΔLi / n+d0; Step 3) the compensation sheet determined in step 2) is installed in the compensation sheet holder. Go back to step 1) and repeat the above iterative process. According to the change in the back intercept of each spliced ​​submodule, the thickness of the corresponding compensation sheet is replaced so that each submodule of the spliced ​​detector is at the same back intercept Lf, and the iteration can be stopped.

[0047] The principle of selecting the aperture of the compensation film is mainly determined by the results of the optical design. The discrete compensation films corresponding to the detector chips spliced ​​at different positions have different effective apertures. The maximum envelope can also be taken according to the results of the optical design as the unified aperture of the compensation film. Figure 4 method for design.

[0048] The parameters of the opening size and thickness of the discrete compensation plate holder are determined according to the results of the optical design to determine the opening size and position of the light-clearance aperture. The thickness of the holder and the pressure plate can be selected according to the design principles of thin-walled structures.

[0049] The assembly of the linear or planar array spliced ​​detector integrated error compensation structure can be completed through modular assembly and testing. The discrete compensation sheet 1, the compensation sheet pressing plate 2, the compensation sheet holder 3 and the linear or planar array spliced ​​detector assembly are relatively independent in terms of process, and can be assembled and tested in parallel. Figure 3 The conventional splicing detector error adjustment and compensation method is shown, as well as the serial assembly and overall disassembly situations thereof.

Claims

1. A linear array or planar array spliced ​​detector integrated error compensation structure, comprising discrete compensation sheets (1) of different optical thicknesses, a compensation sheet pressure plate (2), and a compensation sheet holder (3), which together form a compensation structure; a linear array or planar array spliced ​​detector assembly, comprising a discrete window or filter sheet (4) of the spliced ​​detector, a photosensitive element (5) of the spliced ​​detector, and a base or housing (6) of the spliced ​​detector, characterized in that: The discrete compensation plate (1) is a parallel plate with different optical thicknesses, the optical material of the parallel plate is selected according to the working band of the optoelectronic instrument or the spliced ​​detector, and optical coating treatment is performed according to the working band of the optoelectronic instrument; the discrete compensation plate (1) is fixed in the compensation plate holder (3) by gluing, the compensation plate pressure plate (2) further fixes the discrete compensation plate (1), and the compensation plate pressure plate is fixed to the compensation plate holder (3) by screws; the compensation plate holder (3) is installed on the base or housing (6) of the spliced ​​detector assembly by screws or gluing, or is fixed on an optical-mechanical structure such as a telescope or an optical system, and the discrete window or filter (4) of the spliced ​​detector is one of the components of the spliced ​​detector, or is omitted, and the discrete compensation plate (1) is directly used to replace the function of the discrete window or filter (4); Each photosensitive element (5) of the spliced ​​detector has an exclusive discrete compensation plate (1), and the imaging light beam from the telescope or the optical lens sequentially passes through the discrete compensation plate (1), through the opening of the compensation plate holder (3), or through the discrete window or filter (4) to reach the photosensitive element (5) of each spliced ​​detector in the spliced ​​detector assembly, or directly reaches the photosensitive element (5) of each spliced ​​detector in the spliced ​​detector assembly.

2. According to the linear array or planar array splicing detector comprehensive error compensation structure of claim 1, it is characterized in that the calculation method of the thickness of the discrete compensation sheet (1) is as follows: Step 1) Adjust the posture and position of the spliced ​​detector relative to the telescope or the optical-mechanical system so that the photosensitive element of each spliced ​​submodule i of the spliced ​​detector obtains the back intercept L corresponding to the best focal plane position i ; Step 2) According to the change of the back intercept between the submodules ΔL i , divided by the refractive index n of the compensating plate i , which is the initial thickness of each compensation sheet. On this basis, the thickness d0 is uniformly increased to increase the strength of the compensation sheet and ensure the reliability of the compensation sheet processing and installation. Thus, the initial thickness d of each discrete compensation sheet is obtained. i =ΔL i / n+d0; Step 3) The compensation sheets determined in step 2) are sequentially loaded into the compensation sheet holder, and the process is repeated in step 1). The thickness of the compensation sheets is changed according to the change of the back intercept of each spliced ​​submodule, so that each submodule of the spliced ​​detector is at the same back intercept L. f To stop the iteration.

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