CN105376493B - The method and its focusing system of camera focusing in rail space based on view data - Google Patents

Abstract

The present invention provides the methods and its focusing system of camera focusing in a kind of rail space based on view data, wherein focusing system includes：Data processing unit (1), focusing encoder (2), system controller (3) and focusing execution unit (4), its image restoration based on phase difference is theoretical, simplify the judgement to camera optical system defocusing amount, avoid by ground staff's active interpretation camera optical system whether defocus, optical design and phase difference Image Restoration Algorithm are organically blended, solve the problems, such as a series of key problem in technology and difficult point of space camera focusing, with accuracy of detection height, measurement cost is low, the feature that stability is good and application field is extensive, focusing especially suitable for in-orbit space camera.

Description

Camera focus method and focus system in orbital space based on image data

technical field

The invention relates to the technical field of focusing control of aerospace cameras, and in particular provides a method for focusing a camera in orbital space based on image data and a focusing system thereof.

Background technique

In recent years, aerospace technology has developed very rapidly, and the application of space-borne space cameras has become more and more extensive. The key task of space cameras is to obtain and provide clear and complete images. In order to obtain high-definition images, when the camera is shooting, the ground The scene should be accurately imaged on the photosensitive surface of the CCD. However, with the development of science and technology, the reliability and accuracy requirements of space cameras are getting higher and higher in the harsh launch environment and space environment. Space cameras will be subject to vibration and shock during transportation and launch, and the space temperature is complex when working in orbit. Changeable, the space gravity field is different from the microgravity environment on the earth's surface. These factors may cause the imaging plane of the camera to not coincide with the focal plane, that is, produce different degrees of defocus, resulting in a decrease in imaging quality.

In order to ensure the imaging quality of the camera, the camera is required to have good adaptability to changes in environmental factors. When designing the optical system, structural support and electronic control system of the camera, it is necessary to add a focusing mechanism to the camera system, and use the corresponding focusing mechanism To fine-tune the position of light imaging in the optical system, compensate the defocus amount of CCD, and make the sub-satellite point target accurately image on the CCD photosensitive surface, so as to correct this defocus. The focus adjustment amount of the focusing mechanism depends on the environmental conditions and control accuracy The requirements are determined so that the camera can obtain high-definition images. In addition, the use of space focusing can also relax the requirements on the installation position and accuracy of each optical mirror in the optical system, which is conducive to the reliable operation of the optical remote sensor in harsh environments.

The traditional focus plane detection system needs the autocollimation focus light signal as a reference light to calculate the defocus amount, which can only be realized on the ground, while the focus plane adjustment of the space camera in orbit is determined by the ground personnel to determine whether the camera is out of focus, and Estimate the defocusing amount of the camera, and transmit the defocusing amount and focusing control command of the camera to the camera focusing control system through the satellite payload data processing unit, and the camera focusing control system will adjust the camera focal plane to the best shooting Location. The disadvantage is that the judgment of camera defocus is complicated and needs to be interpreted by ground personnel, which has a certain degree of subjectivity and is easy to cause errors.

Therefore, it is imperative to develop a new type of easy-to-operate on-orbit space camera detection and focusing system.

Contents of the invention

In view of this, the object of the present invention is to provide a camera focusing method and its focusing system in orbital space based on image data, to at least solve the problem that the previous focusing system requires ground personnel to judge whether the focal plane of the camera is out of focus, There is subjectivity and it is easy to cause errors and other problems.

One aspect of the present invention provides a method for focusing a camera in orbital space based on image data, which is characterized in that it includes:

Obtain two images taken by the camera at the same position with different defocus states;

According to the above two images, calculate and obtain the encoder value corresponding to the best focal plane position of the camera;

Obtain the encoder value corresponding to the current focal plane position of the camera;

A corresponding focusing operation is performed according to an error between the encoder value corresponding to the current focal plane position and the encoder value corresponding to the best focal plane position.

Preferably, performing the corresponding focusing operation according to the error between the encoder value corresponding to the current focal plane position and the encoder value corresponding to the best focal plane position includes:

comparing the error between the encoder value corresponding to the current focal plane position and the encoder value corresponding to the best focal plane position with a threshold;

When the error is less than or equal to the threshold, there is no need to start the focusing motor;

When the error is greater than the threshold, according to the encoder value corresponding to the current focal plane position and the encoder value corresponding to the optimal focal plane position, calculate and obtain the number of running steps and running direction of the focusing motor, and perform focusing operate.

Further preferably, according to the encoder value corresponding to the current focal plane position and the encoder value corresponding to the best focal plane position, the formula for calculating the number of running steps and running direction of the focusing motor is:

N＝(AA ₁ )×K ₁ ×M÷θ

Among them, N is the number of running steps of the focusing motor; A is the encoder value corresponding to the best focal plane position; A ₁ is the encoder value corresponding to the current position of the focal plane; K ₁ is the encoder value change and the code The conversion coefficient of the angular change of the encoder; M is the speed ratio of the focusing motor and the encoder; θ is the rotation angle of the motor per step; the symbol of AA ₁ indicates the running direction of the focusing motor.

Further preferably, the calculating and obtaining the encoder value corresponding to the best focal plane position of the camera according to the above two images includes:

According to the two images, the phase difference method is used to calculate and obtain the defocus amount;

calculating and obtaining the best focal plane position according to the defocus amount;

The encoder value corresponding to the best focal plane position is obtained by calculating according to the best focal plane position.

Further preferably, the calculation formula for calculating and obtaining the best focal plane position according to the defocus amount is:

S=K ₄ ×α ₄

Among them, S is the position of the best focal plane, and the unit is μm; K ₄ is the conversion coefficient between the Zernike coefficient and the position of the best focal plane; α ₄ is the fourth item in a set of Zernike coefficients, that is, the amount of defocus .

Further preferably, the calculation formula for obtaining the encoder value corresponding to the best focal plane position according to the best focal plane position is:

A＝A ₀ +(SS ₀ )×K ₂ ×K ₃

Among them, A is the encoder value corresponding to the position of the best focal plane; A ₀ is the encoder value corresponding to the zero position of the focal plane; S is the position of the best focal plane in μm; S ₀ is the zero position of the focal plane in units of μm; K ₂ is the conversion coefficient between the focal plane position change and the encoder angle change; K ₃ is the conversion coefficient between the encoder angle change and the encoder code value change; the symbol of SS ₀ indicates that the best focal plane position is relative to The orientation of the zero position of the focal plane.

Another aspect of the present invention also provides a camera focusing system in orbital space based on image data, which is characterized in that it includes:

The data processing unit 1 is configured to receive two photographed images of the same target object captured by the camera at the same position and different defocus states, and calculate the corresponding position of the best focal plane of the camera according to the received two photographed images. the encoder value;

Focusing encoder 2, used to obtain the encoder value corresponding to the current focal plane position of the camera;

The system controller 3 is connected to the data processing unit 1 and the focusing encoder 2 respectively, and is used to receive the encoder value corresponding to the best focal plane position of the camera sent by the data processing unit 1 and the focusing Encoder 2 sends the encoder value corresponding to the current focal plane position of the camera, and calculates and obtains the focusing information according to the encoder value corresponding to the best focal plane position of the camera and the encoder value corresponding to the current focal plane position of the camera;

The focus execution unit 4 is connected with the system controller 3 and configured to receive the focus information sent by the system controller 3 and adjust the focal plane of the camera according to the focus information.

Preferably, the focusing execution unit 4 includes:

A focusing motor 41 is connected with the system controller 3;

The focusing mechanism 42 is connected with the focusing motor 41 and driven by the focusing motor 41 to perform focusing operation.

Further preferably, the data processing unit 1 includes:

The defocus amount calculation unit 11 is used to receive two captured images of the same target object captured by the camera in different defocus states at the same position, and calculate the defocus amount by using the phase difference method;

The best focus plane position calculation unit 12 is connected to the defocus calculation unit 11, and is used to receive the defocus quantity sent by the defocus calculation unit 11, and calculate and obtain the camera's defocus according to the defocus quantity calculation unit 11. Best focal plane position;

Encoder value calculation unit 13, connected to the best focus plane position calculation unit 12, for receiving the best focus plane position sent by the best focus plane position calculation unit 12, and according to the best focus plane position Calculate and obtain the encoder value corresponding to the best focal plane position of the camera.

The camera focusing method and its focusing system in orbital space based on image data provided by the present invention adopt the image restoration theory of phase difference, which simplifies the judgment of the defocus amount of the camera optical system and avoids the active interpretation of the camera by ground personnel. Whether the optical system is out of focus. The optical design and phase difference image restoration algorithm are organically integrated to solve a series of technical key points and difficulties in space camera focus detection.

The camera focusing method and its focusing system in the orbital space of image data provided by the present invention can greatly reduce the complexity, test time and cost of space camera equipment, as well as the cost of supporting equipment required for measurement. The focusing method and focusing system do not require any additional focusing equipment, and have the advantages of high detection accuracy, low measurement cost, good stability and wide application fields.

Description of drawings

Fig. 1 is the method flowchart of camera focusing in the track space based on image data;

Fig. 2 is the flow chart that utilizes phase difference method to calculate defocus amount;

Fig. 3 is the block diagram of the camera focusing system in the track space based on image data;

Fig. 4 is a block diagram of the data processing unit.

Detailed ways

The present invention will be further explained below with specific examples, but it is not intended to limit the protection scope of the present invention.

A preferred embodiment of the present invention provides a method for camera focusing in orbital space based on image data, see Fig. 1:

(1) The system controller (SMJ320C30) controls the CCD camera to collect aerial remote sensing images in a period of one satellite revolution, and transmits the images to the data processing unit. The data processing unit calculates the defocus amount according to the flow chart of the phase difference method. The focal amount calculates the position of the best focal plane, and then calculates the encoder value corresponding to the position of the best focal plane of the camera according to the position of the best focal plane;

(2) The system controller communicates with the focusing encoder through a serial communication protocol, and reads the encoder value corresponding to the current focal plane position (a 16-bit photoelectric shaft angle encoder is used as the side gauge of the focal plane, and the system controller communicates with the focusing encoder) The RS485 serial communication protocol is adopted between the focusing encoders, the baud rate is 62500Bps, and the DS26C31 and DS26C32 components are used to differentiate the serial communication signals to improve the anti-interference ability and reliability of the serial communication);

(3) According to the technical index requirements in the system design (when the defocus amount is greater than 20um, the focal plane needs to be adjusted), if the camera is out of focus, perform step (4), if the camera is not out of focus, return to step (1).

(4) Calculate the running direction and running steps of the focusing motor (the stepper motor is used as the driving element of the focusing mechanism, the control mode is four-phase eight-beat, and the running frequency P is 1KHz);

(5) The system controller controls the operation of the focusing motor according to the result calculated in step (4).

(6) After the focusing motor finishes running, read the encoder value corresponding to the current focal plane position again, and compare it with the encoder value corresponding to the optimal focal plane position to judge whether the focal plane adjustment error meets the system requirements (encoder code value not greater than 10).

If the error does not meet the system requirements, return to step (4); if the error meets the system requirements, return to step (1).

Wherein, referring to Fig. 2, the specific calculation process of the defocus amount is:

① Perform Fourier transform on the two images i ₁ and i ₂ respectively to obtain I ₁ and I ₂ ;

②Set normalization parameter pupil equation p(x, y)=1, {α} ₀ =0;

③Set the interruption condition, usually the maximum number of iterations or the longest iteration time is used as the stopping criterion;

④ Calculate the point spread function of the two images Wherein the phase of the original channel φ ₁ (x, y) = Z(α), the phase of the out-of-focus channel φ ₂ (x, y) = Z(α)*(x ² +y ² ); the optical transfer function

⑤ According to the formula Calculate the objective function L({α} _t );

⑥Use the L-BGFS method to optimize the objective function, and search for the minimum value of the objective function L({α} _t );

⑦ Obtain a set of estimated values of Zernike coefficient {α} _t , if the interruption condition is not met, return to ④, otherwise output the restoration result, that is, a set of Zernike polynomial coefficients, where the fourth item in the Zernike polynomial coefficient represents the distance from Focus.

The above L-BFGS algorithm:

Step 0: Select the initial point and the initial symmetric positive definite matrix Set the search accuracy ε>0 and the limited number of memories m, calculate the gradient g(x ⁰ ), and set k=0;

Step 1: If ||g(x ^k )||<ε, the algorithm is terminated and the optimal solution x ^k is obtained; otherwise, let

Step2: Use an inexact linear search strategy to determine the step size α _k , update x ^k+1 = x ^k +α _k d ^k , and calculate the gradient value g(x ^k+1) ;

Step 3: Use the initial value H ₀ or intermediate information to construct Repeatedly use formula (10) to perform m+1 corrections to obtain H _k+1 ,

Wherein, s _k =x ^k+1 -x ^k , y _k =g(x ^k+1 )-g(x ^k ).

Step4: Let k=k+1, go to Step 1.

The calculation formula for calculating the best focal plane position according to the amount of defocus is:

S=K ₄ ×α ₄ , where K ₄ is 0.21, and α ₄ is the fourth item in the Zernike coefficient above, that is, the amount of defocus.

The calculation formula for calculating the encoder value corresponding to the best focal plane position according to the best focal plane position is:

A=A ₀ +(SS ₀ )×K ₂ ×K ₃ , where A ₀ is 8000H, S ₀ is 0, K ₂ is 0.045, and K ₃ is 182.

The formula for calculating the running direction and running steps of the focusing motor is:

N=(AA ₁ )×K ₁ ×M÷θ, where K ₁ is 0.0055, M is 40, and θ is 0.9°.

The focusing method of this embodiment simplifies the judgment of the defocus of the camera optical system, realizes automatic real-time judgment, avoids the image data being sent down to the ground, and the ground personnel judge whether the camera optical system is out of focus; the defocus compensation of the optical system In time, it realizes automatic real-time compensation, which saves the processing of downloading data, judging camera defocus, calculating defocus amount, transmitting defocus amount and focusing command, and avoiding the delay of focus compensation due to untimely defocus compensation. Misadjustment that is not in the best position; the defocus compensation of the optical system has high precision, and the defocus of the camera optical system can be identified and compensated in time to realize the closed-loop adjustment of the focal plane, stepping motor and encoder.

Another preferred embodiment of the present invention provides a camera focusing system in the track space based on image data, referring to Fig. 3 , wherein the camera in the track space takes a CCD camera as an example, including:

The data processing unit 1 is used to receive two captured images of the same target object captured by the CCD camera at the same position and different defocus states, and calculate the code corresponding to the position of the best focal plane of the CCD camera based on the received two captured images device value;

Focus encoder 2, used to obtain the encoder value corresponding to the current focal plane position of the CCD camera;

System controller 3, SMJ320C30 can be selected to communicate with focusing encoder 2 through RS-485 serial communication protocol, and read the encoder value corresponding to the current focal plane position of the CCD camera. System controller 3 is also connected to data processing unit 1 , which is used to read the encoder value corresponding to the best focal plane position of the CCD camera, and calculate and obtain the focusing information according to the code corresponding to the current focal plane position and the code corresponding to the best focal plane position;

The focus execution unit 4 is connected with the system controller 3, and is used for receiving the focus information sent by the system controller 3, and adjusting the focal plane of the camera according to the focus information.

Referring to Fig. 3, the focusing execution unit 4 includes:

Focusing motor 41 is connected with system controller 3;

The focusing mechanism 42 is connected with the focusing motor 41 and driven by the focusing motor 41 to perform focusing operation.

Referring to Figure 4, the data processing unit 1 includes:

The defocus amount calculation unit 11 is used to receive two captured images of the same target object captured by the camera in different defocus states at the same position, and calculate the defocus amount by using the phase difference method;

The optimal focus plane position calculation unit 12 is connected with the defocus amount calculation unit 11 for receiving the defocus amount sent by the defocus amount calculation unit 11, and calculating and obtaining the best focus plane position of the camera according to the defocus amount calculation unit;

The encoder value calculation unit 13 is connected with the best focus plane position calculation unit 12, and is used to receive the best focus plane position sent by the best focus plane position calculation unit 12, and calculate and obtain the best focus of the camera according to the best focus plane position calculation unit 12. Encoder value corresponding to face position.

The specific working principle of the focusing system is as follows: the system controller controls the CCD camera to collect and shoot aerial remote sensing images, and transmits the images to the data processing unit, and calculates the encoder value corresponding to the best focal plane position of the CCD camera, and the system controller Communicate with the focus encoder through the RS-485 serial communication protocol, read the encoder value corresponding to the current focal plane position of the CCD camera, and the system controller according to the encoder value of the current focal plane position and the code of the best focal plane position The encoder value calculates the number of steps and the running direction of the focus motor, and controls the operation of the focus motor. The focus motor drives the focus mechanism to move, and completes the adjustment of the focal plane position. The system controller judges the focal plane adjustment by the value of the focus encoder. Whether it meets the error requirements, a closed-loop control of the focusing motor and the focusing encoder is formed.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (4)

1. A method for camera focusing in the track space based on image data, characterized in that, comprising: Obtain two images taken by the camera at the same position with different defocus states; According to the above two images, calculate and obtain the encoder value corresponding to the best focal plane position of the camera; Obtain the encoder value corresponding to the current focal plane position of the camera; performing a corresponding focusing operation according to the error between the encoder value corresponding to the current focal plane position and the encoder value corresponding to the best focal plane position; According to the above two images, calculating and obtaining the encoder value corresponding to the best focal plane position of the camera includes: According to the two images, the phase difference method is used to calculate and obtain the defocus amount; calculating and obtaining the best focal plane position according to the defocus amount; calculating and obtaining an encoder value corresponding to the best focal plane position according to the best focal plane position; The calculation formula for calculating the best focal plane position according to the defocus amount is: S=K ₄ ×α ₄ Among them, S is the position of the best focal plane, and the unit is μm; K ₄ is the conversion coefficient between the Zernike coefficient and the position of the best focal plane; α ₄ is the fourth item in a set of Zernike coefficients, that is, the amount of defocus . 2. According to the method for adjusting camera focus in orbital space based on image data according to claim 1, it is characterized in that, the encoder value corresponding to the current focal plane position corresponds to the code corresponding to the best focal plane position The error between the value of the sensor, the corresponding focus operation includes: comparing the error between the encoder value corresponding to the current focal plane position and the encoder value corresponding to the best focal plane position with a threshold; When the error is less than or equal to the threshold, there is no need to start the focusing motor; When the error is greater than the threshold, according to the encoder value corresponding to the current focal plane position and the encoder value corresponding to the best focal plane position, calculate and obtain the number of running steps and running direction of the focusing motor, and perform focusing operate. 3. According to the method for adjusting camera focus in orbital space based on image data according to claim 2, it is characterized in that, according to the encoder value corresponding to the current focal plane position and the encoding corresponding to the best focal plane position The calculation formula for calculating the running steps and running direction of the focusing motor is: N＝(AA ₁ )×K ₁ ×M÷θ Among them, N is the number of running steps of the focusing motor; A is the encoder value corresponding to the best focal plane position; A ₁ is the encoder value corresponding to the current position of the focal plane; K ₁ is the encoder value change and the code The conversion coefficient of the angular change of the encoder; M is the speed ratio of the focusing motor and the encoder; θ is the rotation angle of the motor per step; the symbol of AA ₁ indicates the running direction of the focusing motor. 4. According to the method of camera focusing in orbital space based on image data according to claim 1, it is characterized in that the calculation formula for obtaining the encoder value corresponding to the best focal plane position is calculated according to the best focal plane position for: A＝A ₀ +(SS ₀ )×K ₂ ×K ₃ Among them, A is the encoder value corresponding to the position of the best focal plane; A ₀ is the encoder value corresponding to the zero position of the focal plane; S is the position of the best focal plane in μm; S ₀ is the zero position of the focal plane in units of μm; K ₂ is the conversion coefficient between the focal plane position change and the encoder angle change; K ₃ is the conversion coefficient between the encoder angle change and the encoder code value change; the symbol of SS ₀ indicates that the best focal plane position is relative to The orientation of the zero position of the focal plane.