CN107092752A - A kind of optical camera simulation imaging method and system based on ray tracing - Google Patents

Abstract

The present invention proposes an optical camera simulation imaging method and system based on ray tracing, the method includes: optical system simulation and imaging and photoelectric system simulation; optical system simulation includes: optical system modeling, camera distortion modeling simulation, camera dispersion Spot modeling and simulation and camera stray light modeling and simulation; imaging and photoelectric system simulation includes spectral response analysis module, CCD photoelectric conversion modeling and simulation, analog circuit modeling and simulation, and digital-analog quantization modeling and simulation. The invention comprehensively considers the influence factors of the remote sensing camera optical system and the CCD imaging system on the imaging result, establishes a detailed and complete remote sensing camera parameter database, makes the simulation image and the real image have a higher degree of closeness, and has higher simulation accuracy.

Description

A ray tracing-based optical camera simulation imaging method and system

technical field

The present invention relates to the technical field of optical system simulation imaging, and more particularly, to a modeling and simulation imaging method and system of an optical camera based on ray tracing.

Background technique

Satellite remote sensing imaging technology is an important technology in the field of remote sensing, and it is widely used in military and national economic fields, such as military reconnaissance, missile early warning, environmental monitoring, resource investigation, etc. The research and development of satellite remote sensing imaging technology has a strong demand and application background in both civilian and military fields. As an important part of the remote sensing satellite, the optical system can simulate the optical system of the remote sensing satellite. At the beginning of the satellite design, a reliable and scientific imaging simulation system can be established, and it will move towards high precision, high performance and high Development in the direction of expansion.

In order to obtain a complete satellite simulation system with high simulation accuracy, it is necessary to perform corresponding simulations on different links of the simulation system in turn, analyze the influencing factors of each link of the imaging simulation system in depth, and establish a scientific and perfect simulation with high accuracy. Model.

The traditional optical system imaging simulation imaging method is based on the mutual conversion relationship between the modulation transfer function MTF, the line spread function LSF, and the point spread function PSF. The two-dimensional PSF matrix is calculated through the optical system MTF. Degradation processing to obtain a simulated image.

However, MTF and PSF describe the frequency or spatial response characteristics of CCD (charge-coupled device) imaging. However, in the imaging process, there are also radiation response characteristics, such as the responsivity and non-uniformity of the detector. Only use MTF or The way PSF is described is incomplete. Therefore, the traditional simulation imaging methods based on MTF or PSF cannot realize comprehensive and systematic simulation of the photoelectric conversion system of remote sensing cameras.

Therefore, an optical camera simulation imaging method and system based on ray tracing is provided, combined with the physical mechanism of ray tracing and modeling simulation, to obtain high-precision degradation simulation images, and provide the most realistic remote sensing data for the scientific research field.

Contents of the invention

In view of this, the present invention provides an optical camera simulation imaging method and system based on ray tracing. On the basis of considering the optical system aberration and the influence of the CCD sensor, the degradation simulation image is obtained, and the remote sensing camera optical system and imaging are realized. Simulation of the system.

In order to solve the above technical problems, the present invention proposes a ray tracing-based optical camera simulation imaging method, including: optical system simulation and imaging and photoelectric system simulation; optical system simulation is based on ray tracing optical system modeling, Realize the optical system modeling calculation, wherein the optical system simulation includes: optical system modeling: according to the design parameters of the optical system, the optical system model is established in the optical design software, and the optical system file is obtained; the camera distortion modeling simulation: through the optical system The file, combined with the CCD image position, establishes the camera distortion parameters, and takes the camera entrance pupil radiance image as input, and obtains the distorted image on the image plane after the distortion model degenerates; the camera diffuse spot modeling simulation: through the light of the optical system Tracking, combined with the optical system file, obtains the diffuse spots of the object points on the imaging plane on the entrance pupil plane, obtains the diffuse spot matrix, and performs diffusion degradation processing on the distorted image on the image plane to obtain the Diffuse speckle images; camera stray light modeling and simulation: ray tracing with the help of stray light simulation analysis software, simulate the suppression of stray light by the optical system under different fields of view, and obtain the stray light irradiance distribution data. The diffuse spot image is degraded by stray light to obtain the stray light irradiance image on the image plane; the imaging and photoelectric system simulation is used to degrade the stray irradiance image on the image plane to obtain the imaging image. Among them, the imaging and photoelectric system simulation includes: spectral response analysis module: calculate the responsivity of the corresponding band according to the band of the entrance pupil radiance image and the spectral response curve of the CCD; CCD photoelectric conversion modeling and simulation: according to the parameter file and circuit of the CCD Parameter file, conduct photoelectric conversion and integral imaging simulation on the stray irradiance image on the image surface, and obtain CCD photoelectric conversion simulation image; analog circuit modeling and simulation: according to the response data of the analog voltage signal in the designed circuit after passing through the circuit device, Obtain the analog circuit simulation file; and degrade the CCD photoelectric conversion simulation image to obtain the analog circuit simulation image; digital-analog quantitative modeling simulation: degrade the input analog circuit simulation image through the digital image file to obtain the analog and quantitative simulation The image is the digital image output from the camera.

Further, the specific method of camera distortion modeling and simulation includes: calculating the minimum sampling interval according to the data such as the entrance pupil diameter; determining the sampling area according to the position on the CCD image, and determining the sampling points in the sampling area in combination with the minimum sampling interval; calling Optical system software, input the coordinate data of the sampling point, determine the distortion value of the sampling point according to the ideal image height and actual image height of the sampling point, and establish the distortion model according to the distortion value of each sampling point; the entrance pupil radiance image of the camera is used as input , after the field of view distortion model degenerates, the camera distortion simulation is completed.

Further, the specific method for modeling and simulating camera speckles includes: generating a camera speckle modeling and simulation input file by inputting parameters of sampling points in CCD imaging; calling optical design software according to the parameters of the camera speckle modeling and simulation file, Track the position of the light emitted by the object point on the image plane, obtain the diffuse spots of the object point on the imaging plane on each field of view on the entrance pupil plane, and obtain the point spread function on the sampling point; for each selected point Point spread function, select a predetermined sampling scale for detailed statistics, and obtain the diffuse speckle matrix centered on the chief ray at the sampling point; perform convolution operation on the distorted image on the image plane and the diffuse class matrix to obtain the diffuse speckle on the image plane image.

Further, specific methods for modeling and simulating camera stray light include:

Import the optical system file of the optical design software into the ray simulation software, and perform ray tracing without other settings to obtain the image plane irradiance file without stray light, and obtain the imaging light source image plane irradiance data E _i ;

Import the optical system file of the optical design software into the light simulation software, complete the light source modeling setting and then perform ray tracing to obtain the stray light image plane irradiance file, and obtain the image plane irradiance data E including stray light and imaging light _h ;

The obtained image plane irradiance data E _h including stray light and imaging light is subtracted from the imaging light source image plane irradiance data E _i , and the matrix subtraction can be calculated to obtain the image plane stray light irradiance distribution data E _s :

E _s =E _h -E _i

According to the stray light irradiance distribution data E _s , calculate the image plane stray light relative irradiance data E _r :

E _r [i, j] = E _s [i, j] / StryMax

In the formula, E _r [i, j] and E _s [i, j] respectively represent the relative irradiance of stray light and the data of stray light irradiance at a certain point on the image plane; StryMax represents the maximum irradiance data of the image plane of the imaging light source .

According to the relative irradiance data of stray light on the image plane and the diffuse spot image on the image plane, the stray light irradiance image E _f on the image plane is obtained;

E _f [i,j]=E _img [i,j]+IMax E _r [i,j]

In the formula, E _img [i, j] represents the gray value of the diffuse light image at point (i, j); IMax represents the maximum gray value of the image. By superimposing the stray light irradiance data into the diffuse light image, the simulation calculation of the image plane stray light image is realized.

Further, the specific method of CCD photoelectric conversion modeling and simulation includes:

Calculate the coordinate position of each sampling point of the CCD on the stray light irradiance image on the image plane, determine the boundary position of the sampling pixel, and re-divide the image pixel;

Calculate the illuminance actually received by the CCD detector through the stray light irradiance data and the CCD duty cycle:

E _real = E × MSR

In the formula, MSR is the CCD duty cycle, and E is the stray light irradiance.

Calculate the output voltage corresponding to each band λ;

Then when the exposure time is , the output voltage corresponding to a single band is:

V _λ =R _λ ×E _real,λ ×τ

In the formula, R _λ is the CCD responsivity, τ is the CCD integration time, E _{resl, λ} is the voltage value of a single band.

Compute the output voltage for n input bands:

Calculate the inconsistency of the brightness of the detector image;

y[i]=k[i]×x[i]+b[i]

Among them, x[i] is the output voltage value of the i-th probe, y[i] is the output of the corresponding probe, k[i] is the inconsistency response coefficient of the i-th probe; b[i] is the Inconsistency bias coefficient of i probes.

Superimpose the noise signal to obtain the real output voltage signal;

V _real = V + V _noise

where V _noise is the noise voltage.

According to the influence of the dynamic range of the CCD on the output voltage of a single detector, the voltage image file V _out of the photoelectric conversion output of the single detector of the CCD is saved.

The stray light irradiance image on the input image plane is degraded according to the voltage image file, and the CCD photoelectric conversion simulation image is obtained.

The present invention also proposes an optical camera simulation imaging system based on ray tracing, including: an optical system simulation unit and an imaging and photoelectric system simulation unit; wherein, the optical system simulation unit includes: an optical system modeling module for The optical system model is established in the design software, and the optical system file is obtained; the camera distortion simulation module is used to establish the geometric distortion parameters of the camera, and the entrance pupil radiance image of the camera is used as input, and the distorted image on the image plane is obtained after the distortion model is degraded; The camera speckle simulation module is used to calculate the speckle situation on the imaging surface of each object point on the entrance pupil plane, obtain the speckle matrix, and perform diffusion degradation processing on the distorted image on the image plane to obtain the speckle on the image plane. Diffuse spot image; camera stray light simulation module, used to simulate the suppression of stray light by the optical system under different fields of view, and obtain the stray light irradiance distribution data. The diffuse speckle image on the image plane is subjected to stray degradation processing, and the stray light irradiance image on the image plane is obtained.

Further, the imaging and optoelectronic system simulation unit includes: a spectral response analysis module, which is used to calculate the responsivity of the corresponding band according to the band of the entrance pupil radiance image and the spectral response curve of the CCD; the CCD photoelectric conversion simulation module is used to establish the CCD The photoelectric conversion model, according to the CCD parameter file and the circuit parameter file, performs photoelectric conversion and integral imaging simulation on the stray light irradiance image, and obtains the CCD photoelectric conversion simulation image; After the response data of the circuit device, the analog circuit simulation file is obtained; and the CCD photoelectric conversion simulation image is degraded to obtain the analog circuit simulation image; the digital-analog quantization simulation module degrades the input analog circuit simulation image through the digital image file , to obtain the analog and quantized simulation image, which is the digital image of the output camera.

Compared with the prior art, the ray tracing-based optical camera simulation imaging method and system of the present invention achieve the following beneficial effects:

(1) The optical camera simulation imaging method and system based on ray tracing of the present invention comprehensively consider the influence factors of the remote sensing camera optical system and the CCD imaging system on the imaging results, and set up a detailed and complete remote sensing camera parameter database, so that the simulation image and The real image has a higher degree of closeness and a higher simulation accuracy.

(2) The optical camera simulation imaging method and system based on ray tracing of the present invention include the optical camera imaging simulation method of camera optical system distortion, diffuse spots and stray light, and realize the calculation of the optical system simulation model; On the basis of tracing the modeling of the optical system, the precision adaptive calculation model is designed, and on the basis of meeting the precision requirements, the calculation speed is improved, and the short-time optical system modeling calculation is realized.

(3) The optical camera simulation imaging method and system based on ray tracing of the present invention carry out mathematical modeling to each subsystem in the CCD camera imaging process on the basis of detailed CCD camera design parameters, and each subsystem is On the basis of modeling, an end-to-end system input and output connection is used for the entire remote sensing camera to realize the simulation of the camera CCD imaging system, a complete simulation technical framework is established, and an accurate model is established for the subsystem.

Of course, any product implementing the present invention does not necessarily need to achieve all the above-mentioned technical effects at the same time.

Other features of the present invention and advantages thereof will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

Fig. 1 is a schematic flow chart of a simulation imaging method for an optical camera based on ray tracing shown in an embodiment of the present invention;

FIG. 2 is a schematic flowchart of a camera distortion modeling and simulation method shown in an embodiment of the present invention;

FIG. 3 is a schematic flowchart of a modeling and simulation method for camera stray light shown in an embodiment of the present invention;

Fig. 4 is the schematic flow chart of CCD photoelectric conversion modeling simulation method shown in the embodiment of the present invention;

FIG. 5 is a structural diagram of an optical camera simulation imaging system based on ray tracing shown in an embodiment of the present invention.

detailed description

Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangements of components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.

The following description of at least one exemplary embodiment is merely illustrative in nature and in no way taken as limiting the invention, its application or uses.

Techniques, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such techniques, methods and devices should be considered part of the description.

In all examples shown and discussed herein, any specific values should be construed as exemplary only, and not as limitations. Therefore, other instances of the exemplary embodiment may have different values.

It should be noted that like numerals and letters denote like items in the following figures, therefore, once an item is defined in one figure, it does not require further discussion in subsequent figures.

In order to solve the problems existing in traditional optical system imaging simulation, the present invention provides an optical camera simulation imaging method and system based on ray tracing, and establishes a high-precision simulation system for remote sensing images. Considering optical system aberration, CCD sensor On the basis of the impact, the entrance pupil radiance image of the optical system is used as the input image to be simulated, and the degradation simulation image is obtained through the simulation of each module in turn. Based on the existing optical camera modeling, the simulation of remote sensing camera optical system and photoelectric conversion system is realized.

Figure 1 is a schematic flowchart of a ray tracing-based optical camera simulation imaging method provided by an embodiment of the present invention, the method includes optical system simulation and imaging and optoelectronic system simulation, wherein the optical system simulation is based on ray tracing optical system modeling On the basis of , realize the modeling calculation of the optical system, including the following steps:

Step 101, optical system modeling: according to the design parameters of the optical system, the optical system model is established in the optical design software, and the optical system file is obtained;

According to the design parameters of the optical system (such as: material and surface type of the mirror, focal length, radius of curvature, etc.), input them into the interface of the optical system design software (such as ZEMAX) in sequence, establish the optical system model, and obtain the ideal optical system file for use Subsequent camera imaging modeling simulation.

Step 102, camera distortion modeling and simulation: through the optical system file, combined with the CCD image position, establish camera distortion parameters, and use the camera entrance pupil radiance image as input, after the distortion model degenerates, obtain the distorted image on the image plane;

In an actual optical system, when the field of view is large, the magnification of a pair of conjugate surfaces will vary with the field of view, which will cause the image to lose its similarity to the real object. This defect that deforms the image is called for distortion.

According to the optical system file obtained by the optical system modeling, combined with the position of the CCD on the image plane, the geometric distortion parameters of the camera are established, and the entrance pupil radiance image of the camera is used as input. After the distortion model is degraded, the distorted image on the image plane is obtained. .

In some optional embodiments, the specific method of camera distortion modeling and simulation is shown in Figure 2, including the following steps:

Step 201, calculating the minimum sampling interval according to data such as the entrance pupil diameter;

According to the diameter of the entrance pupil and the distance from the ground target to the satellite camera, the imaging resolution of the ground target is calculated according to the following formula:

Among them, D is the diameter of the entrance pupil, H is the distance from the ground target to the satellite camera, so that the ideal imaging of the optical system can be obtained, and λ is the center wavelength of the camera imaging.

Input the imaging resolution in the optical system to get the sampling interval;

Among them, f is the focal length of the camera.

Step 202, select a sampling area according to the position on the CCD image, and determine the sampling points in the sampling area in combination with the minimum sampling interval;

Wherein, the minimum sampling interval refers to the preset distance between two adjacent sampling points, and the preset distance is determined by the resolution of the satellite remote sensing camera.

Step 203, call the ZEMAX optical system software, input the coordinate data of the sampling point, determine the distortion value of the sampling point according to the ideal image height and the actual image height of the sampling point, and establish the distortion model according to the distortion value of each sampling point;

Step 204: Taking the entrance pupil radiance image of the camera as input, after the distortion model is degraded, the camera distortion simulation is completed, and the distorted image on the image plane is obtained.

Step 103. Modeling and simulation of camera blur spots: by tracing the rays of the optical system and combining with the optical system files, calculate the diffuse spot conditions of the object points on the imaging plane in each field of view on the entrance pupil plane, and obtain the diffuse spot matrix. The distorted image on the image plane is processed by diffusion degeneration to obtain the image of diffuse spots on the image plane;

In the optical system, there are not only distortion aberrations, but also due to aberrations such as spherical aberration and coma, the imaging of the object point on the image plane is no longer a convergent point, but a diffuse spot. Therefore, for the simulation of aberrations other than camera distortion, a speckle model is established. The model can be calculated by ZEMAX software by tracing the rays of the optical system. The specific simulation method is as follows:

By inputting the parameters of the sampling points in the CCD imaging, the camera dispersion modeling simulation input file is generated; according to the parameters of the camera dispersion spot modeling simulation file, the ZEMAX optical system software is invoked, and the light emitted by the object point is traced according to the ray tracing theory of the optical system. On the position on the image plane, obtain the diffuse spots of the object points on the imaging plane on each field of view on the entrance pupil plane, and obtain the point spread function (PSF) on the sampling point;

For the point spread function of each selected point, select an appropriate sampling scale for detailed statistics, and obtain the diffuse speckle matrix centered on the chief ray at the sampling point;

A convolution operation is performed on the distorted image on the image surface obtained in step 102 and the diffusion spot matrix to obtain a diffusion spot image on the image surface.

Step 104, camera stray light modeling and simulation: use light simulation software (TracePro) to perform ray tracing, simulate the suppression of stray light by the optical system under different fields of view, obtain the stray light irradiance distribution data, and compare the The diffuse speckle image is subjected to stray degradation processing to obtain the stray light irradiance image on the image plane;

Stray light refers to the incident light of other wavelengths away from the absorbed light. Since the light emitted by the light source will reflect when it passes through the surface of the optical element, it can also be scattered from the surface of the optical element and dust in the atmosphere, which will generate stray light, which will affect Image clarity.

According to the needs of stray light simulation, by modeling the structure of the optical system and the hood, a stray light modeling and simulation based on the TracePro model based on the ray tracing algorithm is used to calculate the irradiance image of the image plane, so that the accuracy of the image simulation is high. increase in magnitude.

In some optional embodiments, the specific method of modeling and simulating camera stray light is shown in Figure 3:

Step 301, import the optical system file of the ZAMAX optical design software into the TracePro software, perform ray tracing without other settings, obtain the image plane irradiance file without stray light, and obtain the image plane irradiance of the imaging light source Data E _i .

Step 302, import the optical system file of ZAMAX optical design software into TracePro software, complete the light source modeling setting and then perform ray tracing to obtain the stray light image plane irradiance file, and obtain the image plane irradiance including stray light and imaging light degree data E _i ;

Specifically, the optical system file of the ZAMAX optical design software is imported into the TracePro software as the original optical system, and the material and surface type of the mirror surface in the optical path are set according to the camera parameters; Simulate the real model; set the type of simulated light source, set the radius and range of the grid light source according to the optical system optical path, input the parameters of the incident direction of the light source, set the wavelength of the incident light source, and complete the light source modeling settings. Then ray tracing is performed to obtain the stray light image plane irradiance file, which is the image plane irradiance data E _h including stray light and imaging light.

As an example, a grid point light source may be selected as the simulated light source.

Step 303, matrix subtracting the obtained image plane irradiance data E _h including stray light and imaging light from the imaging light source image plane irradiance data E _i , can be calculated to obtain the image plane stray light irradiance distribution data E _s ;

E _s =E _h -E _i

Step 304. According to the stray light irradiance distribution data E _s , calculate the image plane stray light relative irradiance data E _r ;

E _r [i, j] = E _s [i, j] / StryMax

In the formula, E _r [i,j] and E _s [i,j] respectively represent the relative irradiance of stray light and the data of stray light irradiance at a certain point on the image plane; StryMax represents the maximum irradiance of the imaging light source on the image plane data.

Step 305. Obtain the stray light irradiance image E _f on the image plane according to the relative irradiance data of stray light on the image plane and the diffuse spot image on the image plane;

E _f [i,j]=E _img [i,j]+IMax E _r [i,j]

In the formula, E _img [i, j] represents the gray value of the diffuse light image at point (i, j); IMax represents the maximum gray value of the image. By superimposing the stray light irradiance data into the diffuse light image, the simulation calculation of the image plane stray light image is realized.

Imaging and optoelectronic system simulation is used to degrade the stray light irradiance image on the image plane to obtain imaging images. Among them, imaging and optoelectronic system simulation includes:

Step 105, spectral response analysis module: calculate the responsivity of the corresponding band according to the band of the entrance pupil radiance image and the spectral response curve of the CCD;

According to the wavelength of the entrance pupil radiance image and the spectral response curve of the CCD, the spectral responsivity (R _λi ) corresponding to the imaging band range of λ _i ~ λ _j (i<j) is calculated, and the spectral responsivity of the CCD is:

Step 106, CCD photoelectric conversion modeling and simulation: according to the CCD parameter file and the circuit parameter file, perform photoelectric conversion and integral imaging simulation on the stray irradiance image, and obtain the voltage simulation image output by the CCD;

The photoelectric conversion process of the CCD is mainly the process of converting the optical signal incident on the photosensitive element into an electrical signal. The main factors to be considered in the simulation degradation calculation process of image information processing by CCD photoelectric conversion include duty cycle, responsivity, noise, dark current, and inconsistency of CCD device probes.

In some optional embodiments, the specific steps of CCD photoelectric conversion modeling and simulation are as shown in Figure 4:

Step 401: Calculate the coordinate position of each sampling point of the CCD on the spurious simulation image, determine the boundary position of the sampling pixel, and re-divide the image pixels.

Step 402, calculate the illuminance actually received by the CCD detector through the stray light irradiance data and the CCD duty cycle;

E _real = E × MSR

In the formula, MSR is the CCD duty cycle, and E is the stray light irradiance.

Step 403, calculating the output voltage corresponding to each band λ;

When the exposure time is τ, the output voltage corresponding to a single band is:

V _λ =R _λ ×E _real,λ ×τ

In the formula, R _λ is the CCD responsivity, τ is the CCD integration time, E _{resl, λ} is the voltage value of a single band.

Step 404, calculating the output voltages of n input bands;

Step 405, calculating the inconsistency of the brightness of the detector image;

Due to the inconsistency of the detector response, under uniform illumination, each detector generates different charges, resulting in different image brightness of each detector.

y[i]=k[i]×x[i]+b[i]

Among them, x[i] is the output voltage value of the i-th probe, y[i] is the output of the corresponding probe, k[i] is the inconsistency response coefficient of the i-th probe; b[i] is the Inconsistency bias coefficient of i probes.

In the CCD device manual, PRNU (photoresponse inconsistency) and FPN (fixed pattern noise) are usually given, where the main component of FPN is b[i], and PRNU-FPN is the distribution intensity of k[i]. The distribution of each parameter obeys the normal distribution, and the standard deviation is determined by the two parameters of FPN and PRNU.

In this embodiment, k[i] and b[i] are given probe by probe by the probe non-uniformity parameter.

In a specific embodiment, the inconsistency of the probe response can be characterized by a linear function.

Step 406, superimposing the noise signal to obtain the real output voltage signal;

In the process of storing and transferring information charges, CCD has superposition of noise, which affects the true reproduction of the signal, so the real output voltage signal is:

V _real = V + V _noise

where V _noise is the noise voltage.

Step 407 , according to the influence of the dynamic range of the CCD on the output voltage of the single detector, save the voltage image file V _out output by the photoelectric conversion of the single detector of the CCD.

Wherein, V _{dark current} is the dark current, that is, the output signal of the CCD imaging device under the condition of no light injection and no electricity injection.

V _sat is the saturation output voltage, that is, the signal voltage value output by the device when the exposure incident on the photosensitive element is greater than a certain limit, and the output of the device no longer changes with the increase of the exposure.

Step 408 , input the stray light irradiance image on the image plane, perform degeneration processing on the stray simulation image according to the voltage image file, and obtain the CCD photoelectric conversion simulation image.

Step 107, analog circuit modeling and simulation: according to the response data of the analog voltage signal in the designed circuit after passing through the circuit device, the analog circuit simulation file is obtained; and the CCD photoelectric conversion simulation image is degraded to obtain the analog circuit simulation image;

Analog circuit simulation is to simulate the response of each link of the analog circuit to the analog voltage signal. According to the characteristic parameters of the circuit, the response data of the simulated signal after passing through these circuit modules includes:

According to the amplification factor of the pre-amplification circuit, the impedance matching and amplification of the analog voltage signal output by the CCD sensor are performed;

Perform low-pass filtering on the analog voltage signal output by the pre-amplification circuit according to the frequency of the low-pass filter;

Adjust the analog voltage output by the filter circuit according to the gain magnification and bias magnification of the post amplifier;

According to the circuit noise generated by the camera noise simulation module, the analog circuit noise is superimposed on the voltage signal output by the post amplifier circuit, and finally the output analog circuit simulation file is saved;

The CCD photoelectric conversion simulation image is input, the CCD photoelectric conversion simulation image is degraded according to the voltage image file, and the CCD analog circuit simulation image is obtained.

Step 108, digital-analog quantization modeling and simulation: performing degeneration processing on the input analog circuit simulation image through the digital image file to obtain the analog and quantization simulation image, which is the digital image of the output camera.

In the embodiment of the present invention, comprehensive consideration is given to the simulation of the optical system of the remote sensing camera and the influencing factors of the simulation of the imaging and photoelectric system on the imaging results, and a detailed and complete parameter database of the remote sensing camera is established, so that the simulated image and the real image have a higher degree of closeness, and have a higher degree of accuracy. Simulation accuracy.

FIG. 5 is a structural diagram of an optical camera simulation imaging system based on ray tracing shown in an embodiment of the present invention; the simulation imaging system includes: an optical system simulation unit 51 and an imaging and photoelectric system simulation unit 52 . Wherein, the optical system simulation unit 51 includes: an optical system modeling module 511 , a camera distortion simulation module 512 , a camera speckle simulation module 513 and a camera stray light simulation module 514 .

The optical system simulation unit 51 is based on the modeling of the ray tracing optical system, and designs a precision adaptive calculation model to quickly realize the simulation calculation of the degradation of the entrance pupil radiance image.

The optical system modeling module 511 is used to establish an optical system model in the optical design software to obtain an optical system file.

The camera distortion simulation module 512 is connected with the optical system modeling module 511, and is used to establish geometric distortion parameters of the camera, and takes the radiance image at the entrance pupil of the camera as input, and obtains the distorted image on the image plane after the distortion model degenerates.

The camera distortion simulation module 512 determines the sampling area according to the position on the CCD image, and determines the coordinates of the sampling points in combination with the minimum sampling interval; calls the ZEMAX optical system software, inputs the coordinate data of the sampling points, and obtains the distortion data of the field of view; As input, after the field of view distortion model degenerates, the camera distortion simulation is completed to obtain the distorted image on the image plane. The system directly transmits the camera distortion image to the camera speckle simulation module 513 .

The camera speckle simulation module 513 is connected with the camera distortion simulation module 512, and is used to calculate the speckle situation of the object points on the imaging plane on each field of view on the entrance pupil plane, obtain the speckle matrix, and perform a process on the distorted image on the image plane. Diffuse degeneration processing to obtain the image of diffuse spots on the image plane.

The camera speckle simulation module 513 tracks the position of the light emitted by the object point on the image plane according to the ray tracing and the optical system file, and obtains the speckle situation; calls the ZEMAX optical system software to obtain the matrix of the diffuser plate. The camera distortion image output by the camera distortion simulation module 512 is subjected to a diffuse degradation process to obtain a diffuse speckle image on the image plane. The system transmits the speckle image to the camera stray light simulation unit 514 .

The camera stray light simulation module 514 is connected with the camera speckle simulation module 513, and is used to simulate the suppression of stray light by the optical system under different fields of view, and obtain the stray light irradiance distribution data. The diffuse speckle image on the image plane is subjected to stray degradation processing, and the stray light irradiance image on the image plane is obtained.

The camera stray light simulation module 514 simulates different optical markets by modeling the optical system structure and the hood, and traces rays with the help of the stray light simulation analysis software (TracePro) to obtain the imaging light source image surface irradiance data E _i and The image plane irradiance data E _h including stray light and imaging light, the image plane stray light irradiance data can be obtained through the matrix of the two; by superimposing with the diffuse speckle image output by the camera speckle simulation module 513, the image plane The stray light irradiance image on . The system directly transmits the stray light irradiance image on the image plane to the imaging and optoelectronic system simulation unit 52 .

The imaging and optoelectronic system simulation unit 52 includes: a spectral response analysis module 521 , a CCD photoelectric conversion simulation module 522 , an analog circuit simulation module 523 and a digital-to-analog quantization simulation module 524 .

The imaging and optoelectronic system simulation unit 52 is used to degrade the stray light irradiance image on the image plane to obtain an imaging image.

The spectral response analysis module 521 is used to calculate the responsivity of the corresponding band according to the band of the entrance pupil radiance image and the spectral response curve of the CCD.

The CCD photoelectric conversion simulation module 522 is connected with the camera stray light simulation module 513 and the spectral response analysis module 521 of the optical system simulation unit 51, and is used to set up the CCD photoelectric conversion model, according to the parameter file of CCD and the circuit parameter file to stray light irradiation The simulation of photoelectric conversion and integral imaging is carried out on the high-degree image, and the simulation image of CCD photoelectric conversion is obtained.

The CCD photoelectric conversion simulation module 522 mainly converts the optical signal incident on the photosensitive element into an electrical signal, combined with the duty cycle, responsivity, noise, dark current, inconsistency of the CCD device detector element and integration time of the CCD sensor and other influencing factors , simulating CCD photoelectric conversion to degrade the stray light irradiance image output by the camera stray light simulation module 514 to obtain a CCD photoelectric conversion simulation image. The system directly transmits the photoelectric conversion simulation image to the analog circuit simulation module 523 .

The analog circuit simulation module 523 is connected with the CCD photoelectric conversion simulation module 522, and is used to obtain the analog circuit simulation file according to the response data after the analog voltage signal in the design circuit passes through the circuit device; and degrades the CCD photoelectric conversion simulation image to obtain Analog circuit simulation image.

The analog circuit simulation unit 523 is used to obtain an analog circuit simulation file after the analog voltage signal in the circuit undergoes impedance matching and amplification of circuit devices, low-pass filtering, voltage adjustment and noise superposition processing. Degradation processing is performed on the CCD photoelectric conversion simulation image output by the CCD photoelectric conversion simulation module 522 to obtain a CCD analog circuit simulation image. The system directly transmits the simulation image of the CCD analog circuit to the digital-analog quantization simulation module 524 .

The digital-analog quantization simulation module 524 is connected with the analog circuit simulation module 523, and degrades the input analog circuit simulation image through the digital image file to obtain the analog and quantization simulation image, which is the digital image of the output camera.

It can be seen from the above embodiments that the ray tracing-based optical camera simulation imaging method and system of the present invention achieve the following beneficial effects:

(1) The optical camera simulation imaging method and system based on ray tracing of the present invention comprehensively consider the influence factors of the remote sensing camera optical system and the CCD imaging system on the imaging results, and set up a detailed and complete remote sensing camera parameter database, so that the simulation image and The real image has a higher degree of closeness and a higher simulation accuracy.

(2) The optical camera simulation imaging method and system based on ray tracing of the present invention include the optical camera imaging simulation method of camera optical system distortion, diffuse spots and stray light, and realize the calculation of the optical system simulation model; On the basis of tracing the modeling of the optical system, the precision adaptive calculation model is designed, and on the basis of meeting the precision requirements, the calculation speed is improved, and the short-time optical system modeling calculation is realized.

(3) The optical camera simulation imaging method and system based on ray tracing of the present invention carry out mathematical modeling to each subsystem in the CCD camera imaging process on the basis of detailed CCD camera design parameters, and each subsystem is On the basis of modeling, an end-to-end system input and output connection is used for the entire remote sensing camera to realize the simulation of the camera CCD imaging system, a complete simulation technical framework is established, and an accurate model is established for the subsystem.

Those skilled in the art should understand that the embodiments of the present invention may be provided as methods, apparatuses, or computer program products. Accordingly, the present invention can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and not intended to limit the scope of the present invention. Those skilled in the art will appreciate that modifications can be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

Claims (7)

1. An optical camera simulation imaging method based on ray tracing, characterized in that, comprising: optical system simulation and imaging and photoelectric system simulation; The optical system simulation realizes optical system modeling calculation based on ray tracing optical system modeling, wherein the optical system simulation includes: Optical system modeling: according to the design parameters of the optical system, the optical system model is established in the optical design software, and the optical system file is obtained; Modeling and simulation of camera distortion: through the optical system file, combined with the position of the CCD image, the camera distortion parameters are established, and the entrance pupil radiance image of the camera is used as input, after the distortion model is degraded, the distorted image on the image plane is obtained; Modeling and simulation of camera speckle: through ray tracing of the optical system, combined with the optical system file, the diffuse spot situation of each object point on the imaging surface on the entrance pupil plane is obtained, and the diffuse spot matrix is obtained. The distorted image on the image plane is processed by diffusion degradation to obtain the diffuse spot image on the image plane; Modeling and simulation of camera stray light: With the help of stray light simulation analysis software, ray tracing is carried out to simulate the suppression of stray light by the optical system under different fields of view, and the stray light irradiance distribution data is obtained, and the diffuse spots on the image surface The image is subjected to stray degradation processing to obtain a stray light irradiance image on the image plane; The imaging and optoelectronic system simulation is used to degrade the stray irradiance image on the image plane to obtain imaging images; wherein the imaging and optoelectronic system simulation includes: Spectral response analysis module: Calculate the responsivity of the corresponding band according to the band of the entrance pupil radiance image and the spectral response curve of the CCD; CCD photoelectric conversion modeling and simulation: according to the CCD parameter file and circuit parameter file, perform photoelectric conversion and integral imaging simulation on the stray irradiance image on the image surface, and obtain the CCD photoelectric conversion simulation image; Analog circuit modeling and simulation: According to the response data of the analog voltage signal in the design circuit after passing through the circuit device, the analog circuit simulation file is obtained; and the CCD photoelectric conversion simulation image is degraded to obtain the analog circuit simulation image; Digital-analog quantitative modeling and simulation: performing degeneration processing on the input analog circuit simulation image through digital image files to obtain an analog and quantitative simulation image, which is the digital image of the output camera. 2. The optical camera simulation imaging method based on ray tracing according to claim 1, wherein the specific method of the camera distortion modeling simulation includes: According to the entrance pupil diameter and other data, calculate the minimum sampling interval; Determine the sampling area according to the position on the CCD image, and determine the sampling points in the sampling area in combination with the minimum sampling interval; Call the optical system software, input the coordinate data of the sampling point, determine the distortion value of the sampling point according to the ideal image height and actual image height of the sampling point, and establish the distortion model according to the distortion value of each sampling point; The entrance pupil radiance image of the camera is used as input, and the camera distortion simulation is completed after the field of view distortion model is degenerated. 3. The optical camera simulation imaging method based on ray tracing according to claim 1, characterized in that, the specific method of modeling and simulating the blurred spots of the camera comprises: By inputting the parameters of the sampling points in the CCD imaging, the camera blur spot modeling and simulation input file is generated; according to the parameters of the camera blur spot modeling and simulation file, the optical design software is called to track the position of the light emitted by the object point on the image plane, Obtaining the diffuse spots of the object points on the imaging plane on each field of view on the entrance pupil plane, and obtaining the point spread function on the sampling point; For the point spread function of each selected point, select a predetermined sampling scale to perform detailed statistics to obtain a diffuse spot matrix centered on the chief ray at the sampling point; Convolving the distorted image on the image plane with the diffusion spot matrix to obtain a diffuse spot image on the image plane. 4. The optical camera simulation imaging method based on ray tracing according to claim 1, wherein the specific method of modeling and simulating stray light of the camera comprises: Import the optical system file of the optical design software into the ray simulation software, and perform ray tracing without other settings to obtain the image plane irradiance file without stray light, and obtain the imaging light source image plane irradiance data E _i ; Import the optical system file of the optical design software into the light simulation software, complete the light source modeling setting and then perform ray tracing to obtain the stray light image plane irradiance file, and obtain the image plane irradiance data E including stray light and imaging light _h ; The obtained image plane irradiance data E _h including stray light and imaging light is subtracted from the imaging light source image plane irradiance data E _i , and the matrix subtraction can be calculated to obtain the image plane stray light irradiance distribution data E _s : E _s =E _h -E _i According to the stray light irradiance distribution data E _s , calculate the image plane stray light relative irradiance data E _r : E _r [i, j] = E _s [i, j] / StryMax In the formula, E _r [i, j] and E _s [i, j] respectively represent the relative irradiance of stray light and the data of stray light irradiance at a certain point on the image plane; StryMax represents the maximum irradiance data of the image plane of the imaging light source ; According to the relative irradiance data of stray light on the image plane and the diffuse spot image on the image plane, the stray light irradiance image E _f on the image plane is obtained; E _f [i,j]=E _img [i,j]+IMax E _r [i,j] In the formula, E _img [i, j] represents the gray value of the diffuse light image at point (i, j); IMax represents the maximum gray value of the image; by superimposing the stray light irradiance data into the diffuse light image, the The simulation calculation of the stray light image of the image plane is carried out. 5. the optical camera simulation imaging method based on ray tracing according to claim 1, is characterized in that, the concrete method of described CCD photoelectric conversion modeling simulation, comprises: Calculate the coordinate position of each sampling point of the CCD on the stray light irradiance image on the image plane, determine the boundary position of the sampling pixel, and re-divide the image pixels; Calculate the illuminance actually received by the CCD detector through the stray light irradiance data and the CCD duty cycle: E _real = E × MSR In the formula, MSR is the CCD duty cycle, E is the stray light irradiance; Calculate the output voltage corresponding to each band λ; Then when the exposure time is , the output voltage corresponding to a single band is: V _λ =R _λ ×E _real,λ ×τ In the formula, R _λ is the CCD responsivity, τ is the CCD integration time, E _{resl, λ} is the voltage value of a single band; Compute the output voltage for n input bands: <mrow> <mi>V</mi> <mo>=</mo> <munderover> <mo>&amp;Sigma;</mo> <mrow> <mi>&amp;lambda;</mi> <mo>=</mo> <mn>0</mn> </mrow> <mi>n</mi> </munderover> <msub> <mi>V</mi> <mi>&amp;lambda;</mi> </msub> <mo>=</mo> <mi>&amp;tau;</mi> <munderover> <mo>&amp;Sigma;</mo> <mrow> <mi>&amp;lambda;</mi> <mo>=</mo> <mn>0</mn> </mrow> <mi>n</mi> </munderover> <msub> <mi>R</mi> <mi>&amp;lambda;</mi> </msub> <msub> <mi>E</mi> <mrow> <mi>r</mi> <mi>e</mi> <mi>a</mi> <mi>l</mi> <mo>,</mo> <mi>&amp;lambda;</mi> </mrow> </msub> </mrow> Calculate the inconsistency of the brightness of the detector image; y[i]=k[i]×x[i]+b[i] Among them, x[i] is the output voltage value of the i-th probe, y[i] is the output of the corresponding probe, k[i] is the inconsistency response coefficient of the i-th probe; b[i] is the Inconsistency bias coefficient of i probes; Superimpose the noise signal to obtain the real output voltage signal; V _real = V + V _noise In the formula, V _noise is the noise voltage; According to the influence of the CCD dynamic range on the output voltage of a single probe, save the voltage image file V _out of the photoelectric conversion output of the CCD single probe; The stray light irradiance image on the input image plane is degraded according to the voltage image file, and the CCD photoelectric conversion simulation image is obtained. 6. An optical camera simulation imaging system based on ray tracing, characterized in that it includes: an optical system simulation unit and an imaging and photoelectric system simulation unit; wherein the optical system simulation unit includes: The optical system modeling module is used to establish the optical system model in the optical design software and obtain the optical system file; The camera distortion simulation module is used to establish the geometric distortion parameters of the camera, and the entrance pupil radiance image of the camera is used as input, and the distorted image on the image plane is obtained after the distortion model is degraded; The camera speckle simulation module is used to calculate the speckle situation on the imaging surface of each object point on the entrance pupil plane, obtain the speckle matrix, and perform diffusion degradation processing on the distorted image on the image plane to obtain the speckle on the image plane. Diffuse speckle image; The camera stray light simulation module is used to simulate the suppression of stray light by the optical system in different fields of view, and obtain the stray light irradiance distribution data; perform stray degradation processing on the diffuse spot image on the image plane, and obtain the Stray light irradiance image. 7. The optical camera simulation imaging system based on ray tracing according to claim 6, wherein the imaging and optoelectronic system simulation unit comprises: The spectral response analysis module is used to calculate the responsivity of the corresponding band according to the band of the entrance pupil radiance image and the spectral response curve of the CCD; The CCD photoelectric conversion simulation module is used to establish a CCD photoelectric conversion model, perform photoelectric conversion and integral imaging simulation on the stray light irradiance image according to the CCD parameter file and the circuit parameter file, and obtain the CCD photoelectric conversion simulation image; The analog circuit simulation module is used to obtain the analog circuit simulation file according to the response data of the analog voltage signal in the design circuit after passing through the circuit device; and degrade the CCD photoelectric conversion simulation image to obtain the analog circuit simulation image; The digital-analog quantization simulation module degrades the input analog circuit simulation image through the digital image file to obtain the analog and quantization simulation image, which is the digital image of the output camera.