CN102162739B

CN102162739B - Method and device for testing in-orbit dynamic transfer function of space camera

Info

Publication number: CN102162739B
Application number: CN2010106135964A
Authority: CN
Inventors: 李宪圣; 任建伟; 任建岳; 刘则洵; 万志
Original assignee: Changchun Institute of Optics Fine Mechanics and Physics of CAS
Current assignee: Changchun Institute of Optics Fine Mechanics and Physics of CAS
Priority date: 2010-12-30
Filing date: 2010-12-30
Publication date: 2012-11-07
Anticipated expiration: 2030-12-30
Also published as: CN102162739A

Abstract

The invention provides a method and a device for testing an in-orbit dynamic transfer function of a space camera, and relates to the space optical field. By the invention, the problems that only a small partial area within image element ground resolution can be tested by the conventional camera during radiation brightness measurement of targets paved on the ground during in-orbit dynamic transfer function test, the test data has larger deviation due to the non-uniform targets, and the atmospheric transmissivity and the atmospheric back scattering which are calculated by adopting software are much different from actual values can be solved. In the invention, the test data of the in-orbit dynamic transfer function of the camera can be acquired directly by using the space camera as an optical remote sensor, adding a target of which the placement space frequency is 11p/mm on the ground and using an image shot by the space camera, so an error due to inaccurate ground measurement and atmospheric software calculation can be avoided, the modulation degree from the ground target comprising the atmospheric transmissivity and the atmospheric back scattering to the pupil of the camera is acquired directly, and the in-orbit dynamic transfer function of the camera can be obtained accurately and conveniently. The invention is applied to the in-orbit dynamic transfer test.

Description

Space camera on-orbit dynamic transmission test method and device

技术领域 technical field

本发明涉及空间光学领域，具体涉及一种空间相机在轨动态传函测试方法及装置。 The invention relates to the field of space optics, in particular to an on-orbit dynamic transmission test method and device for a space camera. the

背景技术 Background technique

相机动态传递函数是检验相机成像质量的重要参数，目前，相机在轨动态传函测试是通过测试地面靶标的对比度，即：通过反射比计算靶标的调制度，采用软件计算大气透过率和大气后向散射，而后计算相机入瞳的黑白靶标调制度。该方法存在几个方面的问题，其一、地面测试数据为点测量，只是测量靶标的局部，测试区域只是象元地面分辨力内的小部分，由于靶标的不均匀会造成比较大的偏差。其二，用软件计算大气透过率和大气后散射与实际偏离较大，软件提供的是理想化的模型，并不能正好与当时的天气状况相对应，造成计算值与实际值有较大的偏差。因而给最终的相机在轨动态传函测试造成较大的偏差。要获得准确的动态传函就必须准确的获得靶标（包含大气透过率和大气后向散射）到相机入瞳的调制度。 The dynamic transfer function of the camera is an important parameter to test the imaging quality of the camera. At present, the on-orbit dynamic transfer function of the camera is tested by testing the contrast of the ground target, that is, the modulation degree of the target is calculated by the reflectance, and the atmospheric transmittance and atmospheric transmittance are calculated by software. Backscatter, and then calculate the black and white target modulation degree of the camera entrance pupil. There are several problems in this method. First, the ground test data is a point measurement, which is only a part of the target, and the test area is only a small part of the ground resolution of the pixel. The unevenness of the target will cause relatively large deviations. Second, the calculation of atmospheric transmittance and atmospheric backscattering by software deviates greatly from the actual one. The software provides an idealized model, which does not exactly correspond to the weather conditions at that time, resulting in a large discrepancy between the calculated value and the actual value. deviation. Therefore, a large deviation is caused to the final on-orbit dynamic transmission test of the camera. To obtain accurate dynamic transmission, it is necessary to accurately obtain the modulation degree from the target (including atmospheric transmittance and atmospheric backscatter) to the camera entrance pupil. the

发明内容 Contents of the invention

本发明为解决在现有相机在轨动态传函测试中在地面铺设的靶标辐射亮度测量中只能测试象元地面分辨力内的局部小区域，且由于靶标的不均匀等造成的测试数据有比较大的偏差，同时采用软件计算大气透过率和大气后散射与实际值偏差大的问题，提供一种利用空间相机获取的地面靶标的图像获得在轨动态传函测试方法及装置。 The present invention solves the problem that in the existing camera on-orbit dynamic transmission test, in the measurement of the radiance of the target laid on the ground, only a local small area within the ground resolution of the pixel can be tested, and the test data caused by the unevenness of the target etc. Relatively large deviation, while using software to calculate the problem of large deviation between atmospheric transmittance and atmospheric backscattering and the actual value, provide a method and device for on-orbit dynamic transmission test obtained by using the image of the ground target acquired by the space camera. the

空间相机在轨动态传函测试方法，该方法包括以下步骤： Space camera dynamic transmission test method in orbit, the method comprises the following steps:

步骤一、第一直角靶标、第二直角靶标、奈奎斯特频率的纵向靶标和奈奎斯特频率的横向靶标摆在同一水平地面上； Step 1, the first right-angle target, the second right-angle target, the longitudinal target of Nyquist frequency and the horizontal target of Nyquist frequency are placed on the same horizontal ground;

步骤二、采用步骤一所述的第一直角靶标中白靶标和第二直角靶标中的黑靶标获得到相机入瞳处的包含大气影响在内的调制度M_物， Step 2, using the white target in the first rectangular target and the black target in the second rectangular target described in step 1 to obtain the modulation factor M _object including the atmospheric influence at the entrance pupil of the camera,

具体计算过程为：所述第一直角靶标中的黑靶标、白靶标与第二直角靶标中的黑靶标、白靶标在同一太阳高角下，在地面上具有相同的反射率和相同的辐亮度； The specific calculation process is: the black target and the white target in the first rectangular target and the black target and the white target in the second rectangular target have the same reflectivity and the same radiance on the ground under the same high sun angle;

在地面上具有相同反射率ρ_Wλ的白靶标具有相同的辐亮度B_W， White targets with the same reflectivity _ρWλ on the ground have the same radiance _BW ,

${B B}_{W W} = = {Σ Σ}_{λ λ = = 500500}^{900900} \frac{{E E.}_{λ λ} \times \times {ρ ρ}_{Wλ Wλ}}{π π} = = {Σ Σ}_{λ λ = = 500500}^{900900} {B B}_{Wλ Wλ} - - - - - - ((11))$

式中：B_W-白靶标的辐亮度； In the formula: B _W - the radiance of the white target;

B_Wλ-白靶标的光谱辐亮度； B _Wλ - the spectral radiance of the white target;

E_λ-太阳到达地面的光谱辐照度； E _λ - the spectral irradiance of the sun reaching the ground;

ρ_Wλ-白靶标的光谱反射率； _ρWλ - the spectral reflectance of the white target;

λ-波长，单位为nm； λ-wavelength, the unit is nm;

在地面上具有相同反射率ρ_Dλ的黑靶标具有相同的辐亮度B_D， A black target with the same reflectivity ρ _Dλ on the ground has the same radiance B _D ,

${B B}_{D D.} = = {Σ Σ}_{λ λ = = 500500}^{900900} \frac{{E E.}_{λ λ} \times \times {ρ ρ}_{Dλ Dλ}}{π π} = = {Σ Σ}_{λ λ = = 500500}^{900900} {B B}_{Dλ Dλ} - - - - - - ((22))$

式中：B_D-黑靶标的辐亮度； In the formula: B _D - the radiance of the black target;

B_Dλ-黑靶标的光谱辐亮度； B _Dλ - the spectral radiance of the black target;

ρ_Dλ-黑靶标的光谱反射率； ρ _Dλ - the spectral reflectance of the black target;

大气光谱透过率为τ_λ，大气散射光谱辐亮度为B_SCATλ，所述白靶标到达相机入瞳的辐亮度L_W为 The atmospheric spectral transmittance is τ _λ , the atmospheric scattering spectral radiance is B _SCATλ , and the radiance L _W of the white target reaching the entrance pupil of the camera is

${L L}_{W W} = = {Σ Σ}_{λ λ = = 500500}^{900900} ((\frac{{E E.}_{λ λ} \times \times {ρ ρ}_{Wλ Wλ}}{π π} \times \times {τ τ}_{λ λ} + + {B B}_{SCATλ SCATλ}))$

$= = {Σ Σ}_{λ λ = = 500500}^{900900} \frac{{E E.}_{λ λ} \times \times {ρ ρ}_{Wλ Wλ}}{π π} \times \times {τ τ}_{λ λ} + + {Σ Σ}_{λ λ = = 500500}^{900900} {B B}_{SCATλ SCATλ} = = {Σ Σ}_{λ λ = = 500500}^{900900} \frac{{E E.}_{λ λ} \times \times {ρ ρ}_{Wλ Wλ}}{π π} \times \times {τ τ}_{λ λ} + + {B B}_{SCAT SCAT}$

$= = {Σ Σ}_{λ λ = = 500500}^{900900} {B B}_{Wλ Wλ} \times \times {τ τ}_{λ λ} + + {B B}_{SCAT SCAT} - - - - - - ((33))$

式中：B_SCAT-大气后向散射积分辐亮度； In the formula: B _SCAT - Atmospheric backscatter integrated radiance;

黑靶标到达相机入瞳的辐亮度L_D为 The radiance L _D of the black target reaching the entrance pupil of the camera is

${L L}_{D D.} = = {Σ Σ}_{λ λ = = 500500}^{900900} \frac{{E E.}_{λ λ} \times \times {ρ ρ}_{Dλ Dλ}}{π π} \times \times {τ τ}_{λ λ} + + {B B}_{SCAT SCAT}$

$= = {Σ Σ}_{λ λ = = 500500}^{900900} {B B}_{Dλ Dλ} \times \times {τ τ}_{λ λ} + + {B B}_{SCAT SCAT} - - - - - - ((44))$

相机经过实验室辐射定标，得出相机输出DN值与相机入瞳处的辐射亮度关系为： The camera has been calibrated by laboratory radiation, and the relationship between the camera output DN value and the radiance brightness at the entrance pupil of the camera is obtained as:

DN＝R×L DN=R×L

式中，DN-图像灰度值； In the formula, DN-image gray value;

R-响应度； R-responsiveness;

L-相机入瞳辐亮度； L-camera entrance pupil radiance;

所述相机输出的白靶标DN值的平均值为DN_W，相机输出的黑靶标DN值的平均值为DN_D，可得： The average value of the DN value of the white target output by the camera is DN _W , and the average value of the DN value of the black target output by the camera is D _D , which can be obtained:

DN_W＝R×L_W DN _W = R×L _W

即：L_W＝DN_W/R Namely: L _W = DN _W /R

同样可得： Also available:

L_D＝DN_D/R L _D =DN _D /R

获得：

get:

M_物-相机入瞳处的包含大气影响在内的调制度； M _object - the degree of modulation including atmospheric effects at the entrance pupil of the camera;

步骤三、采用步骤一所述的奈奎斯特频率纵向靶标和奈奎斯特频率的横向靶标（4）测试相机在空间频率为奈奎斯特频率处的像的调制度M_像，获得相机在轨动态传函； Step 3. Use the Nyquist frequency longitudinal target and the Nyquist frequency horizontal target described in step 1 (4) to test the modulation degree M _image of the camera image at the Nyquist frequency at the spatial frequency, and obtain the camera On-orbit dynamic transmission;

具体的计算过程为：所述奈奎斯特频率的纵向靶标和奈奎斯特频率的横向靶标到相机入瞳的调制度M_物与步骤二中第一直角靶标和第二直角靶标获得的到相机入瞳的调制度M_物相等；即： The specific calculation process is: the modulation degree M of the longitudinal target of the Nyquist frequency and the horizontal target of the Nyquist frequency to the entrance pupil of _{the camera} is the same as that obtained by the first right-angle target and the second right-angle target in step 2. The modulation _degree M of the camera entrance pupil is equal; that is:

计算相机垂直卫星飞行轨道方向的像的调制度M_像V和沿轨方向的像的调制度M_像H为： Calculate the modulation degree M _{image V} of the image perpendicular to the satellite flight track direction of the camera and the modulation degree M _{image H} of the image along the track direction as:

式中：DN_Vmax为相机垂直卫星飞行轨道方向的图像灰度值最大值； In the formula: DN _Vmax is the maximum value of the image gray value of the camera vertical to the satellite flight orbit;

DN_Vmin为相机垂直卫星飞行轨道方向的图像灰度值最小值； DN _Vmin is the minimum value of the gray value of the image in the direction of the vertical satellite flight orbit of the camera;

DN_Hmax为相机沿轨方向的图像灰度值最大值； DN _Hmax is the maximum value of the image gray value along the track of the camera;

DN_Hmin为相机沿轨方向的图像灰度值最小值； DN _Hmin is the minimum value of the image gray value along the track of the camera;

获得相机在轨动态传函；所述相机的在轨动态传函分别为相机在垂直卫星飞行轨道方向的动态传函MTF_V和沿轨方向的动态传函MTF_H： Obtain the on-orbit dynamic transfer of the camera; the on-orbit dynamic transfer of the camera is respectively the dynamic transfer MTF _V of the camera in the vertical satellite flight orbit direction and the dynamic transfer MTF _H of the along-track direction:

空间相机在轨动态传函测试装置，该装置包括第一直角靶标、第二直角靶标、奈奎斯特频率的纵向靶标和奈奎斯特频率的横向靶标；所述奈奎斯特频率的纵向靶标与卫星飞行轨道平行，奈奎斯特频率的横向靶标与卫星飞行轨道垂直，所述第一直角靶标、第二直角靶标、奈奎斯特频率的纵向靶标和奈奎斯特频率的横向靶标分别由白靶标和黑靶标组成；所述黑靶标与白靶标的对比度相同，所述第一直角靶标、第二直角靶标、奈奎斯特频率的纵向靶标和奈奎斯特频率的横向靶标摆在同一水平地面上，所述的第一直角靶标和第二直角靶标在空间位置上构成的空间频率与空间相机中的空间频率1lp/mm相对应，所有白靶标都是由同一种材料制成的高漫反射率白靶标，所有黑靶标由另外一种相同的材料制成的低漫反射率黑靶标。 A space camera on-orbit dynamic transmission test device, which includes a first right-angle target, a second right-angle target, a longitudinal target of the Nyquist frequency and a horizontal target of the Nyquist frequency; the longitudinal target of the Nyquist frequency The target is parallel to the satellite flight track, the horizontal target of the Nyquist frequency is perpendicular to the satellite flight track, the first right-angle target, the second right-angle target, the longitudinal target of the Nyquist frequency and the horizontal target of the Nyquist frequency Composed of a white target and a black target respectively; the contrast of the black target and the white target is the same, the first right-angle target, the second right-angle target, the vertical target of the Nyquist frequency and the horizontal target of the Nyquist frequency swing On the same horizontal ground, the spatial frequency formed by the first right-angle target and the second right-angle target at the spatial position corresponds to the spatial frequency 1lp/mm in the space camera, and all white targets are made of the same material A high diffuse reflectance white target, all black targets are made of another low diffuse reflectance black target of the same material. the

本发明的工作原理：本发明提出一种利用相机图像能准确获得相机在轨动态传函的方法；即：通过相机空间频率为1lp/mm的靶标图像获得包含大气透过率和大气后向散射的到相机入瞳的调制度的方法，通过相机空间频率为奈奎斯特频率的靶标图像获得像的调制度的方法，从而准确获得相机在轨动态传函的测试方法，并发明相应的测试装置。本发明是在地面摆设两种靶标，包括对应空间相机的空间频率为1lp/mm的靶标和空间频率为奈奎斯特频率的靶标，空间频率为1lp/mm的靶标用于测试靶标（包含大气透过率和大气后向散射等影响在内）到达相机入瞳处的包含大气影响在内的调制度M_物，空间频率为奈奎斯特频率的靶标用于测试相机在空间频率为奈奎斯特频率处的像的调制度M_像，从而获得相机在轨动态传函，即：MTF=M_像/M_物。在该方法中，用空间频率为1lp/mm的靶标图像获得相机入瞳的调制度M_物，是该靶标辐射亮度经过大气传输（即受大气透过率和大气后向散射等影响后）到达相机入瞳，被相机接收后转化为图像输出的，相机输出的图像灰度值和相机入瞳的辐亮度是线性响应关系，即图像灰度值正比于相机入瞳辐亮度，因而用空间频率为1lp/mm的靶标对应的图像灰度值（该图像几乎不受空间频率影响）即可求得相机入瞳处的调制度M_物，该M_物是包含当时大气透过率和大气后向散射在内的，是通过空间相机直接测得的真实值。与空间频率为奈奎斯特频率的靶标经大气透过率和大气后向散射后到达相机入瞳的状态是一致的，相同的太阳高角、相同的反射率、相同的大气透过率，相同的大气后向散射辐亮度，只是空间频率不同，因而该方法避免了因地面测量不准确和用大气软件计算引入的误差。能更准确方便的获得相机在轨动态传函。 The working principle of the present invention: the present invention proposes a method for accurately obtaining the dynamic transmission of the camera on orbit by using the camera image; The method of obtaining the modulation degree of the camera entrance pupil, the method of obtaining the modulation degree of the image through the target image whose spatial frequency is the Nyquist frequency, so as to accurately obtain the test method of the dynamic transmission of the camera on orbit, and invent the corresponding test device. In the present invention, two kinds of targets are placed on the ground, including a target with a spatial frequency of 1 lp/mm corresponding to a space camera and a target with a spatial frequency of Nyquist frequency, and a target with a spatial frequency of 1 lp/mm for testing targets (including atmospheric Transmittance and atmospheric backscattering, etc.) The modulation degree M _object including the atmospheric influence reaching the entrance pupil of the camera, the target whose spatial frequency is Nyquist frequency is used to test the camera at the spatial frequency of Nyquist frequency The modulation degree of the image at the Stern frequency is M _image , so as to obtain the on-orbit dynamic transmission of the camera, that is: MTF=M _image /M _object . In this method, the target image with a spatial frequency of 1lp/mm is used to obtain the modulation degree M of the camera entrance _pupil , which means that the radiance of the target arrives at The entrance pupil of the camera is converted into an image output after being received by the camera. The gray value of the image output by the camera and the radiance of the entrance pupil of the camera have a linear response relationship, that is, the gray value of the image is proportional to the radiance of the entrance pupil of the camera, so the spatial frequency The gray value of the image corresponding to the target of 1lp/mm (the image is hardly affected by the spatial frequency) can obtain the modulation degree M _object at the entrance pupil of the camera, _which includes the atmospheric transmittance and atmospheric backward Scattering is included, which is the real value directly measured by the space camera. It is consistent with the state that the target whose spatial frequency is the Nyquist frequency reaches the entrance pupil of the camera after the atmospheric transmittance and atmospheric backscattering. The same high angle of the sun, the same reflectivity, the same atmospheric transmittance, the same The atmospheric backscattered radiance of , but the spatial frequency is different, so this method avoids the errors introduced by inaccurate ground measurements and calculations by atmospheric software. It can more accurately and conveniently obtain the dynamic transmission of the camera in orbit.

本发明的有益效果：本发明通过地面摆设对应空间相机的空间频率为1lp/mm的靶标，和摆设对应相机空间频率为奈奎斯特频率靶标，通过分析空间相机获得的靶标图像，直接获得相机的在轨动态传函测试数据，该方法准确、简单和方便，避免因地面测量误差和估算大气透过率及大气后向散射等引入的误差。 Beneficial effects of the present invention: the present invention arranges a target whose spatial frequency is 1 lp/mm corresponding to the space camera on the ground, and arranging a target whose spatial frequency is the Nyquist frequency corresponding to the camera, and directly obtains the camera by analyzing the target image obtained by the space camera. This method is accurate, simple and convenient, and avoids errors introduced by ground measurement errors and estimated atmospheric transmittance and atmospheric backscattering. the

附图说明 Description of drawings

图1为本发明所述的空间相机在轨动态传函测试装置摆放示意图。 Fig. 1 is a schematic diagram of the layout of the space camera on-orbit dynamic transmission test device according to the present invention. the

图中：1、第一直角靶标，2、奈奎斯特频率的纵向靶标，3奈奎斯特频率靶标单元，4、奈奎斯特频率的横向靶标，5、第二直角靶标。 In the figure: 1. The first right-angle target, 2. The longitudinal target of the Nyquist frequency, 3. The Nyquist frequency target unit, 4. The horizontal target of the Nyquist frequency, 5. The second right-angle target. the

具体实施方式 Detailed ways

具体实施方式一、结合图1说明本实施方式，空间相机在轨动态传函测试方法，该方法由以下步骤实现： Specific embodiments one, illustrate present embodiment in conjunction with Fig. 1, space camera is on orbit dynamic letter test method, and this method is realized by the following steps:

步骤一、第一直角靶标1、第二直角靶标5、奈奎斯特频率的纵向靶标2和奈奎斯特频率的横向靶标摆在同一水平地面上； Step 1, the first right-angle target 1, the second right-angle target 5, the longitudinal target 2 of the Nyquist frequency and the horizontal target of the Nyquist frequency are placed on the same horizontal ground;

步骤二、采用步骤一所述的第一直角靶标1中的白靶标和第二直角靶标5中的黑靶标获得到相机入瞳处的包含大气影响在内的调制度M_物， Step 2, using the white target in the first rectangular target 1 described in step 1 and the black target in the second rectangular target 5 to obtain the modulation degree M _object including the atmospheric influence at the entrance pupil of the camera,

具体计算过程为：所述第一直角靶标1中的黑靶标、白靶标与第二直角靶标5中的黑靶标、白靶标在地面上具有相同的反射率和相同的辐亮度；在相机成像时刻，结合图1中的所有靶标都在相同的太阳高角下，经过相同的大气透过率，受相同的大气后向散射影响后，到达相机入瞳，再经过具有线性响应的相机后，获得相机输出的靶标图像。 The specific calculation process is: the black target and the white target in the first rectangular target 1 and the black target and the white target in the second rectangular target 5 have the same reflectivity and the same radiance on the ground; , combined with the fact that all the targets in Figure 1 are at the same high sun angle, after passing through the same atmospheric transmittance and affected by the same atmospheric backscattering, they reach the entrance pupil of the camera, and then pass through the camera with linear response to obtain the camera The output target image. the

${B B}_{W W} = = {Σ Σ}_{λ λ = = 500500}^{900900} \frac{{E E.}_{λ λ} {\times \times ρ ρ}_{Wλ Wλ}}{π π} = = {Σ Σ}_{λ λ = = 500500}^{900900} {B B}_{Wλ Wλ} - - - - - - ((11))$

λ-波长单位为nm。 λ-wavelength in nm. the

${B B}_{D D.} = = {Σ Σ}_{λ λ = = 500500}^{900900} \frac{{E E.}_{λ λ} {\times \times ρ ρ}_{Dλ Dλ}}{π π} = = {Σ Σ}_{λ λ = = 500500}^{900900} {B B}_{Dλ Dλ} - - - - - - ((22))$

式中：B_D-黑靶标的辐亮度。 In the formula: B _D - the radiance of the black target.

B_Dλ-黑靶标的光谱辐亮度 B _Dλ - Spectral radiance of black target

此时的大气光谱透过率为τ_λ，大气散射光谱辐亮度为B_SCATλ，则白靶标到达相机入瞳的辐亮度L_W为 At this time, the atmospheric spectral transmittance is τ _λ , and the atmospheric scattering spectral radiance is B _SCATλ , then the radiance L _W of the white target reaching the entrance pupil of the camera is

在图1所示的靶标中，所有白靶标的反射率相同，因而到达相机入瞳的辐亮度L_W相等，所有黑靶标的发射率相同，同样到达相机入瞳的辐亮度L_D相等。 In the targets shown in Figure 1, all white targets have the same reflectivity, so the radiance L _W reaching the camera entrance pupil is equal, all black targets have the same emissivity, and the radiance L _D reaching the camera entrance pupil is also equal.

对于相机输出DN值与入瞳处的辐射亮度L有如下关系： The relationship between the camera output DN value and the radiance L at the entrance pupil is as follows:

DN＝R×L DN=R×L

式中，DN-相机输出DN值； In the formula, DN-camera output DN value;

R-响应度； R-responsiveness;

L-相机入瞳辐亮度。 L - camera entrance pupil radiance. the

在图1中，白靶标选取1中A区域，输出DN值的均值为DN_W，黑靶标选取5中的B区域，输出DN值的均值为DN_D，A区域和B区域在空间位置上构成相机空间频率为1lp/mm的靶标，此时相机的传函为0.9999，因而在两个区域上输出的DN值几乎不受相机传函影响，于是 In Figure 1, the white target selects area A in 1, and the average output DN value is DN _W , the black target selects area B in 5, and the average output DN value is _DND , and the spatial position of A area and B area constitutes For a target whose spatial frequency of the camera is 1lp/mm, the transfer function of the camera is 0.9999 at this time, so the DN value output on the two areas is hardly affected by the transfer function of the camera, so

DN_W＝R×L_W DN _W = R×L _W

即求得：L_W＝DN_W/R That is to obtain: L _W = DN _W /R

同样可得： Also available:

L_D＝DN_D/R L _D =DN _D /R

可求得

available

M_物-相机入瞳调制度； M _object -camera entrance pupil modulation degree;

步骤三、采用步骤一所述的奈奎斯特频率纵向靶标和奈奎斯特频率的横向靶标4测试相机在空间频率为奈奎斯特频率处的像的调制度M_像，获得相机在轨动态传函； Step 3. Use the Nyquist frequency longitudinal target and the Nyquist frequency horizontal target 4 described in step 1 to test the modulation degree M _image of the image of the camera at the Nyquist frequency at the spatial frequency, and obtain the camera on-orbit Dynamic letter;

具体计算过程为：所述奈奎斯特频率的纵向靶标2和奈奎斯特频率的横向靶标4到相机入瞳的调制度M_物与步骤二中第一直角靶标1和第二直角靶标5获得到相机入瞳的调制度M_物相等；图像是受奈奎斯特频率空间频率影响，由于奈奎斯特频率的纵向靶标2和奈奎斯特频率的横向靶标4上的白靶标的材料与第一直角靶标1和第二直角靶标5中白靶标材料一致，该奈奎斯特频率的纵向靶标2和奈奎斯特频率的横向靶标4上的黑靶标的材料与第一直角靶标1和第二直角靶标5中的黑靶标材料一致，即分别具有相同的反射率，因而到达相机入瞳的M_物为 The specific calculation process is: the longitudinal target 2 of the Nyquist frequency and the horizontal target 4 of the Nyquist frequency to the modulation degree M of the camera entrance _pupil and the first right-angle target 1 and the second right-angle target 5 in step 2 The modulation _degree M obtained to the camera entrance pupil is equal; the image is affected by the Nyquist frequency spatial frequency, due to the material of the white target on the vertical target 2 of the Nyquist frequency and the horizontal target 4 of the Nyquist frequency Consistent with the material of the white target in the first rectangular target 1 and the second rectangular target 5, the material of the black target on the vertical target 2 of the Nyquist frequency and the horizontal target 4 of the Nyquist frequency is consistent with that of the first rectangular target 1 It is consistent with the black target material in the second right-angle target 5, that is, has the same reflectivity respectively, so the M _object reaching the entrance pupil of the camera is

利用奈奎斯特频率的纵向靶标2和奈奎斯特频率的横向靶标4中的靶标图像，可以计算出相机垂直轨道方向的像的调制度M_像V和沿轨方向的像的调制度M_像H Using the target images in the longitudinal target 2 of the Nyquist frequency and the horizontal target 4 of the Nyquist frequency, the modulation degree M of the image in the vertical track direction of the camera and the modulation degree _M of the image along the track direction can be calculated _{like H}

于是求得相机的在垂直轨道方向的动态传函MTF_V和沿轨方向的动态传函MTF_H Then the dynamic transfer function MTF _V of the camera in the direction of the vertical track and the dynamic transfer function MTF _H of the direction along the track are obtained

结合图1，本实施方式所述的所有白色区域都是有同一种材料制成的高漫反射率白靶标，所有黑色区域有另外一种相同的材料制成的低漫反射率黑靶标，黑、白靶标具有相同的对比度；其中第一直角靶标1和第二直角靶标5中白色区域和黑色区域大小为20倍的地面象元分辨力的正方形，第一直角靶标1和第二直角靶标5构成对应空间相机1lp/mm空间频率的靶标，用于获得相机入瞳处的包含大气影响在内的调制度M_物；3是纵向靶标单元，2是由N个奈奎斯频率靶标单元3组成的具有1/N位错的纵向靶标，即相邻的两个纵向靶标单元3在空间位置上摆放时之间的距离为（N-1）/N的靶条宽度，所述每个靶条宽度为1倍地面象元分辨力，每个靶条长度为8倍地面象元分辨力，用于测量垂直轨道方向的动态传递函数；4是由N个奈奎斯频率的靶标单元3组成的具有1/N位错的横向靶标，即将与2相同的靶标转90度放置，成为横向靶标，用于测量沿轨道方向的动态传递函数；所述N为大于等于5的正整数。 With reference to Figure 1, all white areas described in this embodiment are white targets with high diffuse reflectance made of the same material, and all black areas have black targets with low diffuse reflectance made of the same material. , white targets have the same contrast; wherein the white area and black area in the first rectangular target 1 and the second rectangular target 5 are squares whose size is 20 times the ground pixel resolution, the first rectangular target 1 and the second rectangular target 5 Constitute a target corresponding to the spatial frequency of 1 lp/mm of the space camera, which is used to obtain the modulation degree M _object at the entrance pupil of the camera including the influence of the atmosphere; 3 is a longitudinal target unit, and 2 is composed of N Nyquis frequency target units 3 The vertical target with 1/N dislocation, that is, the distance between two adjacent vertical target units 3 when placed in space is (N-1)/N target strip width, and each target The bar width is 1 times the resolution of the ground pixel, and the length of each target bar is 8 times the resolution of the ground pixel, which is used to measure the dynamic transfer function in the vertical orbit direction; 4 is composed of N Nyquis frequency target units 3 The horizontal target with 1/N dislocations, that is, the same target as 2 is turned 90 degrees to become a horizontal target for measuring the dynamic transfer function along the track direction; the N is a positive integer greater than or equal to 5.

具体实施方式二、空间相机在轨动态传函测试装置，该装置包括第一直角靶标1、第二直角靶标5、奈奎斯特频率的纵向靶标2和奈奎斯特频率的横向靶标4；所述奈奎斯特频率的纵向靶标2与卫星飞行轨道平行，奈奎斯特频率的横向靶标4与卫星飞行轨道垂直，所述第一直角靶标1、第二直角靶标5、奈奎斯特频率的纵向靶标2和奈奎斯特频率的横向靶标4分别由白靶标和黑靶标组成；所述黑靶标与白靶标的对比度相同。 Embodiment 2. Space camera on-orbit dynamic transmission test device, which includes a first right-angle target 1, a second right-angle target 5, a longitudinal target 2 of the Nyquist frequency and a horizontal target 4 of the Nyquist frequency; The vertical target 2 of the Nyquist frequency is parallel to the satellite flight track, the horizontal target 4 of the Nyquist frequency is perpendicular to the satellite flight track, and the first right-angle target 1, the second right-angle target 5, the Nyquist The longitudinal target 2 of frequency and the transverse target 4 of Nyquist frequency consist of a white target and a black target, respectively; the black target has the same contrast as the white target. the

本实施方式所述的所述的第一直角靶标1和第二直角靶标5构成对应空间相机1lp/mm空间频率的靶标。 The first right-angle target 1 and the second right-angle target 5 described in this embodiment form a target corresponding to the spatial frequency of the space camera 1 lp/mm. the

本实施方式所述的奈奎斯特频率的纵向靶标2和奈奎斯特频率的横向靶分别由N个奈奎斯特频率靶标单元3组成的具有1/N位错的纵向靶标单元和N个奈奎斯频率靶标单元3组成的具有1/N位错的横向靶标单元组成，所述N为大于等于5的正整数。 The Nyquist frequency longitudinal target 2 and the Nyquist frequency transverse target described in this embodiment are respectively composed of N Nyquist frequency target units 3 and a longitudinal target unit with 1/N dislocations and N Nyquis frequency target units 3 are composed of lateral target units with 1/N dislocations, where N is a positive integer greater than or equal to 5. the

本发明通过空间相机作为光学遥感器，直接获得包含大气透过率和大气后向散射在内的地面靶标到达相机入瞳处的包含大气影响在内的调制度M_物，避免了因地面测量不准确和用大气软件计算引入的误差，能通过相机获得靶标图像更准确方便的获得相机在轨动态传函。 In the present invention, the space camera is used as an optical remote sensor to directly obtain the modulation degree M _object including the influence of the atmosphere when the ground target including the atmospheric transmittance and atmospheric backscatter reaches the entrance pupil of the camera, avoiding the inaccurate measurement caused by the ground. Accurate and the error introduced by atmospheric software calculation can obtain the target image through the camera more accurately and conveniently obtain the camera's on-orbit dynamic transmission.

Claims

1. space camera on-orbit dynamic transmission test method, it is characterized in that, the method comprises the following steps:

Step 1. The first right-angle target (1), the second right-angle target (5), the Nyquist frequency longitudinal target (2) and the Nyquist frequency horizontal target (4) are placed on the same level ground;

Step 2. Using the first rectangular target (1) and the second rectangular target (5) described in step 1 to obtain the modulation degree M _object including the atmospheric influence at the entrance pupil of the camera,

The specific calculation process is: the black and white targets in the first rectangular target (1) and the black and white targets in the second rectangular target (5) have the same reflectivity on the ground under the same high sun angle and the same radiance;

White targets with the same reflectivity _ρWλ on the ground have the same radiance _BW ,

In the formula: B _W - the radiance of the white target;

B _Wλ - the spectral radiance of the white target;

E _λ - the spectral irradiance of the sun reaching the ground;

_ρWλ - the spectral reflectance of the white target;

λ-wavelength, the unit is nm;

A black target with the same reflectivity ρ _Dλ on the ground has the same radiance B _D ,

In the formula: B _D - the radiance of the black target;

B _Dλ - the spectral radiance of the black target;

ρ _Dλ - the spectral reflectance of the black target;

The atmospheric spectral transmittance is τ _λ , the atmospheric scattering spectral radiance is B _SCATλ , and the radiance L _W of the white target reaching the entrance pupil of the camera is

In the formula: B _SCAT - atmospheric backscattering integrated radiance; the radiance L _D of the black target reaching the entrance pupil of the camera is

The camera output DN value is:

DN=R×L

In the formula, DN-image gray value;

R-responsiveness;

L-camera entrance pupil radiance;

The mean value of the DN value of the white target output by the camera is DN _W , and the mean value of the DN value of the black target output by the camera is D _D , which can be obtained:

DN _W = R×L _W

Namely: L _W = DN _W /R

Also available:

L _D =DN _D /R

get:

M _object - the degree of modulation including atmospheric effects at the entrance pupil of the camera;

Step 3. Use the Nyquist frequency longitudinal target (2) and the Nyquist frequency horizontal target (4) described in step 1 to test the modulation _degree M of the image of the camera at the Nyquist frequency. , to obtain the dynamic transmission of the camera in orbit;

The specific calculation process is: the modulation degree M between the longitudinal target (2) of the Nyquist frequency and the horizontal target (4) of the Nyquist frequency to the entrance pupil of the _camera and the first rectangular target (1 ) is equal to the modulation _degree M obtained by the second right-angle target (5) to the entrance pupil of the camera, including the influence of the atmosphere; that is:

Calculate the modulation degree M _{image V} of the image perpendicular to the satellite flight track direction of the camera and the modulation degree M _{image H} of the image along the track direction as:

In the formula: DN _Vmax is the maximum gray value of the image in the direction of the vertical satellite flight orbit of the camera;

DN _Vmin is the minimum image gray value of the camera perpendicular to the satellite flight orbit;

DN _Hmax is the maximum gray value of the image along the track of the camera;

DN _Hmin is the minimum gray value of the image along the track of the camera;

Obtain the on-orbit dynamic transfer of the camera; the on-orbit dynamic transfer of the camera is respectively the dynamic transfer MTF _V of the camera in the vertical satellite flight orbit direction and the dynamic transfer MTF _H of the along-track direction:

2. The space camera on-orbit dynamic transmission test method according to claim 1, characterized in that the longitudinal target (2) of the Nyquist frequency and the horizontal target (4) of the Nyquist frequency in step 1 ) a longitudinal target with 1/N dislocations composed of N Nyquist frequency target units (3) and a transverse target with 1/N dislocations composed of N Nyquist frequency target units (3) Composition, said N is a positive integer greater than or equal to 5.

3. space camera according to claim 2 on-orbit dynamic letter test method, is characterized in that, the distance of the adjacent target unit in the longitudinal target of described 1/N dislocation and the transverse target of 1/N dislocation It is the target bar width of (N-1)/N.

4. The space camera on-orbit dynamic transmission test method according to claim 1, characterized in that the white target in the first rectangular target (1) and the black target in the second rectangular target (5) in step 1 are The spatial frequency formed at the spatial position corresponds to the spatial frequency 1 lp/mm in the spatial camera.

5. Space camera on-orbit dynamic transmission test device, the device includes the first right-angle target (1), the second right-angle target (5), the longitudinal target of the Nyquist frequency (2) and the horizontal direction of the Nyquist frequency Target (4); the longitudinal target (2) of the Nyquist frequency is parallel to the satellite flight track, the horizontal target (4) of the Nyquist frequency is perpendicular to the satellite flight track, and the first rectangular target (1) , the second right-angle target (5), the longitudinal target (2) of the Nyquist frequency and the horizontal target (4) of the Nyquist frequency are composed of a white target and a black target respectively; the contrast between the black target and the white target Similarly, the first right-angle target (1), the second right-angle target (5), the Nyquist frequency longitudinal target (2) and the Nyquist frequency horizontal target (4) are placed on the same horizontal ground, The spatial frequency formed by the first right-angle target (1) and the second right-angle target (5) at the spatial position corresponds to the spatial frequency 1lp/mm in the space camera, and all white targets are made of the same material A high diffuse reflectance white target, all black targets are made of another low diffuse reflectance black target of the same material.

6. The space camera on-orbit dynamic transmission test device according to claim 5, characterized in that the white target in the first rectangular target (1) and the black target in the second rectangular target (5) are in the spatial position The spatial frequency of the above composition corresponds to the spatial frequency 1 lp/mm in the space camera.

7. The space camera on-orbit dynamic transmission test device according to claim 5, characterized in that the longitudinal target (2) of the Nyquist frequency and the horizontal target (4) of the Nyquist frequency are respectively composed of A longitudinal target unit with 1/N dislocations composed of N Nyquist frequency units and a transverse target unit with 1/N dislocations composed of N Nyquist frequency units, where N is greater than or equal to 5 positive integer. the