CN114565664B - Centering method and system based on modulation - Google Patents

Abstract

The invention discloses a modulation-based centering method and system. The method includes: fixing a detector on a multi-degree-of-freedom displacement platform so that a point light source forms an image on the image plane of the detector; Apply displacement modulation in the x direction and y direction, so that the multi-degree-of-freedom displacement platform moves in the x-direction and y-direction; wherein, the detector moves with the movement of the multi-degree-of-freedom displacement platform; Frame image; according to the obtained frame images, calculate the average neutral position of several light spots; perform circle fitting on the average neutral position of several light spots obtained from the calculation, and obtain the circle fitting result; according to the circle fitting result , to obtain the position of the center of the circle, that is, the static center position of the light spot on the image surface under the state of no modulation of the detector. The invention reduces random errors and systematic errors, and improves centering precision.

Description

A modulation-based centering method and system

technical field

The invention belongs to the technical field of image processing, in particular to a modulation-based centering method and system.

Background technique

Scientific-grade optical image detectors, such as CCD or CMOS APS, are widely used in astronomy, biology, ultraviolet imaging, power line detection, night vision imaging, low-light safety and other scientific research as mainstream optical image conversion equipment. middle. In the current space missions, satellites, intercontinental strategic missiles, spaceships and other aerospace vehicles, for their own attitude determination and control, as well as the optical axis pointing or target pointing of specific tasks, most of them use the attitude of star sensors and other optical image detectors sensor.

Centering refers to the high-precision positioning of the image spot center under the agreed center definition conditions, which is a basic problem in many fields such as astrometry, microscopic imaging, and deep space exploration. Studying the centering method of the light spot in the imaging process is the basis for realizing high-precision detector calibration and improving the measurement accuracy of the attitude sensor. Existing technologies mainly include centroid method, threshold centroid method, and parameter estimation. These methods are based on the research of centering methods of static light spots, and the random error and systematic error restrict the centering accuracy.

Contents of the invention

The technical solution of the present invention is to overcome the deficiencies of the prior art, provide a modulation-based centering method and system, reduce random errors and systematic errors, and improve centering accuracy.

In order to solve the above technical problems, the present invention discloses a modulation-based centering method, including:

Fix the detector on a multi-degree-of-freedom displacement platform to make the point light source image on the image plane of the detector;

Apply displacement modulation in the x direction and y direction on the multi-degree-of-freedom displacement platform, so that the multi-degree-of-freedom displacement platform moves in the x-direction and y-direction; wherein, the detector moves with the movement of the multi-degree-of-freedom displacement platform;

Obtain several frames of images during the movement of the multi-degree-of-freedom displacement platform;

According to several frames of images acquired, the average neutral position of several light spots is obtained through calculation;

Perform circular fitting on the average neutral positions of several light spots obtained from the calculation, and obtain the circular fitting result;

According to the fitting result of the circle, the position of the center of the circle is obtained, that is, the position of the static center of the light spot on the image surface under the state of no modulation of the detector.

In the above modulation-based centering method, several frames of images during the movement of the multi-degree-of-freedom displacement platform are obtained, including:

During the n+1 steps of the multi-degree-of-freedom displacement platform, the detector is exposed m times for each step of the multi-degree-of-freedom displacement platform; then a total of (n+1)*m frames of images are obtained.

In the above modulation-based centering method, the average neutral positions of several light spots are calculated according to the acquired frames of images, including:

For m frames of images in the first step: calculate and obtain the center position of the light spot on each frame of image (x ₁₁ ,y ₁₁ ), (x ₂₁ ,y ₂₁ ),..., (x _m1 ,y _m1 ), (x ₁₁ ,y ₁₁ ), (x ₂₁ ,y ₂₁ ), ..., (x _m1 ,y _m1 ) are averaged to obtain the average neutral position of the first spot (x ₁ ,y ₁ );

For the m frames of images in the second step: calculate the center position of the light spot on each frame image (x ₁₂ , y ₁₂ ), (x ₂₂ , y ₂₂ ), ..., (x _m2 , y _m2 ), Average (x ₁₂ , y ₁₂ ), (x ₂₂ , y ₂₂ ), ..., (x _m2 , y _m2 ) to get the average neutral position of the second spot (x ₂ , y ₂ );

...And so on,

For the m-frame image in the n+1th step: calculate the center position of the spot on each frame image (x _1(n+1) , y _1(n+1) ), (x _{2(n+ 1)} ,y _2(n+1) ),..., (x _m(n+1) ,y _m(n+1) ), for (x ₁₁ ,y ₁₁ ), (x ₂₁ ,y ₂₁ ) , ..., (x _m1 , y _m1 ) are averaged to obtain the average neutral position (x _n+1 , y _n+1 ) of the n+1th light spot.

In the above-mentioned centering method based on modulation, the circle fitting is performed on the average neutral positions of several light spots obtained from the calculation, and the circle fitting results are obtained, including:

Perform circle fitting on (x ₁ , y ₁ ), (x ₂ , y ₂ ), ..., (x _n+1 , y _n+1 ), and obtain the circle fitting result.

In the above-mentioned centering method based on modulation, it also includes: placing the multi-degree-of-freedom displacement platform fixed with the detector in the darkroom cabin to isolate stray light from the external environment and improve measurement accuracy.

In the above-mentioned modulation-based centering method, the displacement modulations in the x-direction and y-direction applied to the multi-degree-of-freedom displacement platform are displacement modulations in the form of sine and cosine.

In the above modulation-based centering method, the displacement modulations in the x-direction and y-direction are:

Wherein, SX _i represents the displacement modulation in the x direction applied for the ith time, SY _i represents the displacement modulation in the y direction applied for the ith time, i=0, 1, 2, . . . , n, and V represents a voltage value.

In the above modulation-based centering method, the step size of the multi-degree-of-freedom displacement platform is

In the modulation-based centering method described above, the detector is an optical image detector.

Correspondingly, the present invention also discloses a centering system based on modulation, including: a detector, a multi-degree-of-freedom displacement platform and a computer controller; wherein, the detector is fixed on the multi-degree-of-freedom displacement platform, and the point light source Imaging on the image plane; the computer controller is connected to the detector and the multi-degree-of-freedom displacement platform through data lines;

A computer controller is used to apply displacement modulation in the x direction and the y direction on the multi-degree-of-freedom displacement platform, so that the multi-degree-of-freedom displacement platform moves in the x direction and the y direction;

The multi-degree-of-freedom displacement platform is used to drive the detector to move accordingly;

The detector is used to acquire several frames of images during the movement;

The computer controller is also used to calculate and obtain the average neutral positions of several light spots according to the frames of images obtained by the detector; perform circle fitting on the average neutral positions of the several light spots obtained through the calculation, and obtain a circle approximation According to the result of the circle fitting, the position of the center of the circle is obtained, that is, the static center position of the light spot on the image surface when the detector is not modulated.

The present invention has the following advantages:

(1) The present invention discloses a modulation-based centering scheme, which reduces the random error and systematic error in the traditional single-point centering method, improves the centering accuracy, and can realize higher-precision centering and detector calibration .

(2) The present invention discloses a modulation-based centering scheme, which is simple in calculation, high in efficiency, convenient in operation, and can be applied to high-precision centering in various fields.

(3) The present invention discloses a modulation-based centering scheme, which is helpful for researchers to evaluate and study the scientific imaging capabilities of image detectors, and can provide detectors for scientific applications such as optical measurement and astronomical measurement Calibration requirements, applicable to practical engineering applications, the prospects are very broad.

Description of drawings

Fig. 1 is a flow chart of steps of a modulation-based centering method in an embodiment of the present invention;

Fig. 2 is a structural block diagram of a modulation-based centering system in an embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the embodiments disclosed in the present invention will be further described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, in this embodiment, the modulation-based centering method includes:

In step 101, the detector is fixed on a multi-degree-of-freedom displacement platform, so that a point light source forms an image on the image plane of the detector.

In this embodiment, the multi-degree-of-freedom displacement platform with fixed detectors can be placed in the darkroom cabin to isolate stray light from the external environment and improve measurement accuracy. Wherein, the detector may specifically be an optical image detector.

Step 102, applying displacement modulation in the x-direction and y-direction to the multi-degree-of-freedom displacement platform, so that the multi-degree-of-freedom displacement platform moves in the x-direction and y-direction.

In this embodiment, the detector moves with the movement of the multi-degree-of-freedom displacement platform. Among them, the step size of the multi-degree-of-freedom displacement platform is

Preferably, the displacement modulations in the x-direction and y-direction applied to the multi-degree-of-freedom displacement platform are displacement modulations in the form of sine and cosine.

Specifically, the displacement modulations in the x direction and the y direction are as follows:

Wherein, SX _i represents the displacement modulation in the x direction applied for the ith time, SY _i represents the displacement modulation in the y direction applied for the ith time, i=0, 1, 2, . . . , n, and V represents a voltage value.

Step 103, acquiring several frames of images during the movement of the multi-degree-of-freedom displacement platform.

In this embodiment, during the n+1 steps of the multi-degree-of-freedom displacement platform movement, the detector is exposed m times for each step of the multi-degree-of-freedom displacement platform; then a total of (n+1)*m frame image.

Step 104 , according to the acquired frames of images, calculate and obtain the average neutral position of several light spots.

In this embodiment, the specific process of calculating the average neutral position of each light spot can be as follows:

For m frames of images in the first step: calculate and obtain the center position of the light spot on each frame of image (x ₁₁ ,y ₁₁ ), (x ₂₁ ,y ₂₁ ),..., (x _m1 ,y _m1 ), (x ₁₁ ,y ₁₁ ), (x ₂₁ ,y ₂₁ ), ..., (x _m1 ,y _m1 ) are averaged to obtain the average neutral position of the first spot (x ₁ ,y ₁ ).

For m frames of images in the second step: calculate and obtain the center position of the light spot on each frame image (x ₁₂ , y ₁₂ ), (x ₂₂ , y ₂₂ ), ..., (x _m2 , y _m2 ), (x ₁₂ , y ₁₂ ), (x ₂₂ , y ₂₂ ), ..., (x _m2 , y _m2 ) are averaged to obtain the average neutral position of the second spot (x ₂ , y ₂ ).

...And so on,

For the m-frame image in the n+1th step: calculate the center position of the spot on each frame image (x _1(n+1) , y _1(n+1) ), (x _{2(n+ 1)} ,y _2(n+1) ),..., (x _m(n+1) ,y _m(n+1) ), for (x ₁₁ ,y ₁₁ ), (x ₂₁ ,y ₂₁ ) , ..., (x _m1 , y _m1 ) are averaged to obtain the average neutral position (x _n+1 , y _n+1 ) of the n+1th light spot.

Step 105 , performing circle fitting on the average neutral positions of several light spots obtained through the calculation, to obtain a circle fitting result.

In this embodiment, (x ₁ , y ₁ ), (x ₂ , y ₂ ), ..., (x _n+1 , y _n+1 ) obtained in step 104 can be connected to form an approximate circle The contour of the circle is fitted with the circle equation to obtain the circle fitting result.

In step 106, the position of the center of the circle is obtained according to the result of the circle fitting, that is, the position of the still center of the light spot on the image plane under the state of no modulation of the detector.

On the basis of the above embodiments, as shown in FIG. 2 , the present invention also discloses a modulation-based centering system, including: a detector 101 , a multi-degree-of-freedom displacement platform 102 and a computer controller 103 . Wherein, the detector 101 is fixed on the multi-degree-of-freedom displacement platform 102, and the point light source forms an image on the image plane of the detector 101; the computer controller 103 is respectively connected with the detector 101 and the multi-degree-of-freedom displacement platform 102 through data lines.

Preferably, the computer controller 103 is configured to apply displacement modulation in the x-direction and y-direction to the multi-degree-of-freedom displacement platform, so as to make the multi-degree-of-freedom displacement platform move in the x-direction and y-direction. The multi-degree-of-freedom displacement platform 102 is used to drive the detector to move accordingly. The detector 101 is used for acquiring several frames of images during motion. The computer controller 103 is also used to calculate and obtain the average neutral position of several light spots according to the several frames of images obtained by the detector; perform circle fitting on the average neutral position of several light spots obtained by the calculation to obtain the circumference Fitting result: According to the fitting result of the circle, the position of the center of the circle is obtained, that is, the static center position of the light spot on the image surface when the detector is not modulated.

As for the system embodiment, since it corresponds to the method embodiment, the description is relatively simple, and for the related parts, please refer to the description of the method embodiment.

Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention, and any person skilled in the art can use the methods disclosed above and technical content to analyze the present invention without departing from the spirit and scope of the present invention. Possible changes and modifications are made in the technical solution. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention, which do not depart from the content of the technical solution of the present invention, all belong to the technical solution of the present invention. protected range.

The content that is not described in detail in the specification of the present invention belongs to the well-known technology of those skilled in the art.

Claims (8)

1. A modulation-based centering method, comprising:

fixing the detector on a multi-degree-of-freedom displacement platform, and imaging the point light source on the image surface of the detector;

applying displacement modulation in the x direction and the y direction on the multi-degree-of-freedom displacement platform to enable the multi-degree-of-freedom displacement platform to move in the x direction and the y direction; wherein the detector moves along with the movement of the multi-degree-of-freedom displacement platform;

acquiring a plurality of frames of images in the motion process of the multi-degree-of-freedom displacement platform; comprising the following steps: in the process of n+1 step sizes of the movement of the multi-degree-of-freedom displacement platform, exposing the detector for m times when the multi-degree-of-freedom displacement platform moves for one step size; then (n+1) m frames of images are obtained in total;

according to the acquired frames of frame images, calculating to obtain the average neutral positions of the light spots;

performing circumference fitting on the average neutral positions of the plurality of light spots obtained by the calculation to obtain a circumference fitting result;

according to the circumferential fitting result, obtaining the center position of the circle, namely the static center position of the light spot on the image surface under the non-modulation state of the detector;

wherein:

according to the acquired frames of frame images, calculating to obtain a plurality of average neutral positions of light spots, wherein the method comprises the following steps:

for m frame images in step 1: resolving to obtain the central position (x ₁₁ ,y ₁₁ )、(x ₂₁ ,y ₂₁ )、...、(x _m1 ,y _m1 ) Pair (x) ₁₁ ,y ₁₁ )、(x ₂₁ ,y ₂₁ )、...、(x _m1 ,y _m1 ) Averaging to obtain the 1 st spot average neutral position (x ₁ ,y ₁ )；

For m frame images in step 2: resolving to obtain the central position (x ₁₂ ,y ₁₂ )、(x ₂₂ ,y ₂₂ )、...、(x _m2 ,y _m2 ) Pair (x) ₁₂ ,y ₁₂ )、(x ₂₂ ,y ₂₂ )、...、(x _m2 ,y _m2 ) Averaging to obtain the average neutral position (x ₂ ,y ₂ )；

By analogy with the sequence of,

for m frame images in the n+1th step: resolving to obtain the central position (x _1(n+1) ,y _1(n+1) )、(x _2(n+1) ,y _2(n+1) )、...、(x _m(n+1) ,y _m(n+1) ) Pair (x) ₁₁ ,y ₁₁ )、(x ₂₁ ,y ₂₁ )、...、(x _m1 ,y _m1 ) Averaging to obtain the average neutral position (x _n+1 ,y _n+1 )。

2. The method for centering based on modulation according to claim 1, wherein performing a circle fit on the average neutral position of the plurality of spots obtained by the calculation to obtain a circle fit result comprises:

couple (x) ₁ ,y ₁ )、(x ₂ ,y ₂ )、...、(x _n+1 ,y _n+1 ) And performing circumference fitting to obtain a circumference fitting result.

3. The modulation-based centering method of claim 1, further comprising: the multi-degree-of-freedom displacement platform fixed with the detector is placed in the darkroom cabin to isolate stray light of the external environment and improve measurement accuracy.

4. The method of claim 1, wherein the x-direction and y-direction displacement modulations applied to the multi-degree of freedom displacement platform are in the form of sine-cosine displacement modulations.

5. The method of centering based on modulation of claim 4, wherein the displacement modulations in the x-direction and the y-direction are respectively:

wherein SX is _i Representing the displacement modulation in the x-direction of the ith application, SY _i The displacement modulation in the y direction for the i-th application is indicated, i=0, 1, 2.

6. The method of claim 1, wherein the step size of the multi-degree-of-freedom displacement stage is

7. The modulation-based centering method of claim 1, wherein the detector is an optical image detector.

8. A modulation-based centering system, comprising: the device comprises a detector, a multi-degree-of-freedom displacement platform and a computer controller; the detector is fixed on the multi-degree-of-freedom displacement platform, and the point light source images on the image surface of the detector; the computer controller is respectively connected with the detector and the multi-degree-of-freedom displacement platform through data lines;

the computer controller is used for applying displacement modulation in the x direction and the y direction on the multi-degree-of-freedom displacement platform so as to enable the multi-degree-of-freedom displacement platform to move in the x direction and the y direction;

the multi-degree-of-freedom displacement platform is used for driving the detector to move along with the multi-degree-of-freedom displacement platform;

the detector is used for acquiring a plurality of frames of images in the motion process; comprising the following steps: in the process of n+1 step sizes of the movement of the multi-degree-of-freedom displacement platform, exposing the detector for m times when the multi-degree-of-freedom displacement platform moves for one step size; then (n+1) m frames of images are obtained in total;

the computer controller is also used for calculating to obtain the average neutral position of the plurality of light spots according to the plurality of frame images acquired by the detector; performing circumference fitting on the average neutral positions of the plurality of light spots obtained by the calculation to obtain a circumference fitting result; according to the circumferential fitting result, obtaining the center position of the circle, namely the static center position of the light spot on the image surface under the non-modulation state of the detector;

wherein:

when the computer controller obtains the average neutral position of a plurality of light spots according to a plurality of frame images acquired by the detector, the computer controller comprises the following steps:

according to the acquired frames of frame images, calculating to obtain a plurality of average neutral positions of light spots, wherein the method comprises the following steps:

for m frame images in step 1: resolving to obtain the central position (x ₁₁ ,y ₁₁ )、(x ₂₁ ,y ₂₁ )、...、(x _m1 ,y _m1 ) Pair (x) ₁₁ ,y ₁₁ )、(x ₂₁ ,y ₂₁ )、...、(x _m1 ,y _m1 ) Averaging to obtain the 1 st spot average neutral position (x ₁ ,y ₁ )；

For m frame images in step 2: resolving to obtain the central position (x ₁₂ ,y ₁₂ )、(x ₂₂ ,y ₂₂ )、...、(x _m2 ,y _m2 ) Pair (x) ₁₂ ,y ₁₂ )、(x ₂₂ ,y ₂₂ )、...、(x _m2 ,y _m2 ) Averaging to obtain the average neutral position (x ₂ ,y ₂ )；

By analogy with the sequence of,

for m frame images in the n+1th step: resolving to obtain the central position (x _1(n+1) ,y _1(n+1) )、(x _2(n+1) ,y _2(n+1) )、...、(x _m(n+1) ,y _m(n+1) ) Pair (x) ₁₁ ,y ₁₁ )、(x ₂₁ ,y ₂₁ )、...、(x _m1 ,y _m1 ) Averaging to obtain the average neutral position (x _n+1 ,y _n+1 )。