Automatic focusing method for recording and broadcasting camera

Abstract

The invention discloses an automatic focusing method for a recording and broadcasting camera. Firstly, different focal lengths are divided according to different zoom multiples, and the optimal reset point of a motor group inside the camera is determined based on a PI group output value, and the motor group is reset; then, the movement direction and the number of steps of the motor group are adjusted based on a specific zoom multiple to complete the zoom; finally, an image at a current focal length is captured, a definition evaluation value FV of the image is calculated, the motor group is further adjusted, and a definition evaluation value comparison is performed, and an image with the highest FV value is taken as the final target; the invention can effectively reduce the movement stroke of the internal motor group at different focal lengths, thereby reducing the imaging ghost time, improving the shooting accuracy, and realizing fast macro zooming at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of intelligent zooming, and in particular relates to an automatic focusing method for a recording and broadcasting camera. Background Art

[0002] At present, the onlooker teaching solutions for vocational education and experimental teaching scenarios in the market have gradually matured, and the research and training demonstration solutions are gradually moving towards intelligence and integration. In the existing technology, intelligent recording and broadcasting teaching is generally used to solve the problem of demonstration teaching. The teacher's demonstration teaching process is filmed in real time through a high-definition recording and broadcasting camera, and the screen is projected to the group end and the student end in real time, thereby achieving the effect of multi-end demonstration.

[0003] Among the more mature products currently available, a high-definition recording and broadcasting camera is connected to a robotic arm at one end, which can automatically track the target based on target detection and target tracking algorithms. However, due to the characteristics of the recording and broadcasting camera, when the target object moves or switches, the relative distance changes, and the recording and broadcasting camera has an obvious long-term virtual image phenomenon during the zoom process, affecting the recording of the teaching process. At the same time, since the recording and broadcasting camera itself is a large-magnification zoom lens, the purpose is to obtain clearer images under high magnification conditions, so it cannot take into account the problem of clear imaging at close distances. Therefore, when shooting close-range targets, there is a lack of clarity. Summary of the invention

[0004] Purpose of the invention: In view of the problems existing in the above-mentioned background technology, the present invention provides an automatic focusing method for a recording and broadcasting camera. First, a reset method of a motor group inside the camera is given based on different zoom multiples, and the optimal reset position of the camera motor is given. Then, the zoom ring is specifically adjusted according to different zoom multiples to start zooming. Finally, the clarity evaluation value is used to finely adjust the camera motor group to obtain the clearest image under the current zoom multiple.

[0005] Technical solution: A method for automatically focusing a recording and broadcasting camera, comprising the following steps:

[0006] Step S1, dividing different focal lengths according to different zoom multiple ranges, determining the best reset point of the motor group inside the camera based on the PI group output value, and performing motor group reset;

[0007] Step S2, adjusting the movement direction and number of steps of the motor group based on the specific zoom multiple to complete the zoom;

[0008] Step S3, capturing an image at the current focal length, calculating the definition evaluation value FV of the image, further adjusting the motor group, and performing definition evaluation value comparison, with the image with the highest FV value as the final target.

[0009] Furthermore, in step S1, the zoom range is divided into macro focal length, medium focal length and long focal length in order from small to large; different motor reset procedures are performed for different focal lengths; specifically,

[0010] Step S1.1, at the macro focal length, the PI group controls the motor group to move toward the mechanical rear dead point, with the mechanical rear dead point as the optimal reset point;

[0011] Step S1.2, at the middle focal length, feedback control is performed according to the output state value PI out of the PI group; PI out includes two state values, High and Low; the critical value for jumping from the High state to the Low state is set to P1, and the critical value for jumping from the Low state to the High state is set to P2;

[0012] When the initial state of PI out is High, the PI group controls the internal motor group to run at v1 speed to Low state, and detects the PI out state value in real time; when the PI out state value is P1, the PI group controls the internal motor group to continue running in the Low direction for N steps, and runs slowly in the reverse direction at v2 speed until PI out is P2 state, which means the reset is completed; the v2 speed is lower than v1;

[0013] When the initial state of PI out is Low, the PI group controls the internal motor group to run at v1 speed to High state, and monitors the PI out output value in real time. When the output value is High, the PI group controls the internal motor group to run N steps in the Low direction and run in the reverse direction at v2 speed until PI out is P2 state, which means the reset is completed;

[0014] Step S1.3: At the long focal length, the PI group controls the motor group to move toward the mechanical front dead point, with the mechanical front dead point as the optimal reset point.

[0015] Furthermore, when the zoom ratio is 1x-3x, it is classified as a macro focal length; when the zoom ratio is 3x-13x, it is classified as a medium focal length; and when the zoom ratio is 13x-18x, it is classified as a telephoto focal length.

[0016] Furthermore, in step S2, after the motor group is reset, the zoom motor and focus motor inside the camera group are adjusted to specific positions according to the specific zoom factor, and then the focus motor is further adjusted based on the image clarity to change the distance between the lens and the image sensor to complete the image focusing.

[0017] Furthermore, in step S3, the focus motor movement direction and number of steps are adjusted based on the image clarity evaluation value FV to complete the automatic focusing; specifically,

[0018] Step S3.1, capturing a frame of image at the current focal length, and calculating the image clarity evaluation value FV1;

[0019] Step S3.2, set the initial moving direction and initial step size of the focus motor, move the lens and capture the next frame of image, calculate the clarity evaluation value FV2 of the image; when FV2>FV1, continue to move in the same direction until FV2<FV1, which means that the image clarity decreases, move the focus motor in the opposite direction of the initial moving direction, and reduce the initial step size, repeat the above operation until the FV value that meets the preset accuracy requirements is obtained, and autofocus is completed.

[0020] Compared with the prior art solutions, the technical solution adopted by the present invention has the following beneficial effects:

[0021] (1) The present invention sets different motor group reset procedures for different zoom ratio ranges, covering a variety of focal lengths from macro to long distance, and provides relatively optimal initial positions at different focal lengths. When zooming and focusing are performed subsequently, the movement of the motor group can be completed in a relatively short time, greatly reducing the ghosting time during the zooming process.

[0022] (2) During the reset process, the motor group inside the camera is controlled through the output state feedback of the PI group, and the critical point of the PI out output value jump is used as the reset position of the motor group, which makes the control more precise. In the PI group, each PI controller is responsible for controlling a specific motor movement. The PI controllers work together as a whole to achieve precise control of complex systems. Multiple lenses or optical elements work together through their respective PI controllers to achieve the best focusing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the principle of the camera automatic focusing method provided by the present invention;

[0024] Figure 2 A schematic diagram of the camera reset method provided by the present invention;

[0025] Figure 3 This is a PI group output state diagram in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In the prior art, intelligent recording and broadcasting teaching is generally used to solve the problem of demonstration teaching. The teacher’s teaching process is filmed in real time through a high-definition recording and broadcasting camera, and the screen is projected to the group end and the student end in real time, thereby achieving the effect of multi-end teaching. Among the more mature products currently available, a robotic arm is connected to one end of the high-definition recording and broadcasting camera, and the robotic arm can automatically track the target based on target detection and target tracking algorithms. However, due to the characteristics of the recording and broadcasting camera, when the target object moves or switches, due to the change in relative distance, the recording and broadcasting camera has an obvious long-term virtual image phenomenon during the zoom process, which affects the recording of the teaching process. At the same time, since the recording and broadcasting camera itself is a large-magnification zoom lens, the purpose is to obtain clearer imaging under high magnification conditions, so it cannot take into account the problem of clear imaging at close distances. Therefore, when shooting relatively close targets, there is an unclear situation.

[0027] In view of the above problems existing in actual recording, the present invention designs an automatic focusing method for a recording and broadcasting camera. First, a method for resetting the internal motor group of the camera is given based on different zoom multiples, and the optimal camera motor reset position is given. Then, the zoom ring is specifically adjusted according to different zoom multiples to start zooming. Finally, the clarity evaluation value is used to finely adjust the camera motor group to obtain the clearest image under the current zoom multiple. The automatic focusing method provided by the embodiment of the present invention is further described below in conjunction with the drawings of the specification.

[0028] In this embodiment, the internal motor group of the camera includes a zoom motor for adjusting the focal length of the lens and a focus motor for focusing the image. Both the zoom motor and the focus motor are stepping motors. Through the cooperation of the two motors, accurate imaging can be achieved. In this embodiment, a PI group is used to control the two motors. The PI group is a control system set composed of multiple PI controllers, where each PI controller is responsible for controlling a specific motor. The specific steps of the camera automatic focusing method described in this embodiment are as follows: Figure 1 As shown, including:

[0029] Step S1: Based on different zoom ratio ranges, the best reset point is selected, and the PI group controls the internal motor group of the camera to complete the reset.

[0030] like Figure 1 As shown, in this embodiment, the zoom ratio is divided into three zoom ratio ranges of 1x-3x, 3x-13x and 13x-18x, corresponding to the macro focal length, medium focal length and long focal length respectively. Since the starting movement position of the motor group inside the camera is not fixed during the zooming process, the traditional motor group movement method has obvious ghost images during the zooming process due to the long motor movement stroke, and it is impossible to focus accurately in a short time, which has a significant impact on the recording of the teaching process. To address this problem, this embodiment proposes a PI control group control method under different zoom ratios to achieve rapid resetting of the camera motor group, such as Figure 2shown.

[0031] Step S1.1, when the zoom ratio is 1x-3x, it represents macro shooting. At this time, the PI group controls the motor group inside the camera to move to the mechanical rear dead point, and uses the mechanical rear dead point as the reset point.

[0032] Step S1.2: When the zoom ratio is 3x-13x, feedback control is performed based on the PI group output state. The output state PI out of the PI group is as follows: Figure 3 As shown, PI out includes two state values, High and Low. The critical value for jumping from the High state to the Low state is set to P1, and the critical value for jumping from the Low state to the High state is set to P2. When executing the reset program, feedback control is performed based on PI out. Specifically, when the initial state of PI out is High, the PI group controls the internal motor group to run to the Low state at a speed of v1. During the running, the PI out state value is detected in real time. When the PI out state value is P1, the PI group controls the internal motor group to continue running in the Low direction for N steps, and runs slowly in the reverse direction at a speed of v2 until PI out is in the P2 state, which means that the reset is completed. The v2 speed is lower than v1.

[0033] When the initial state of PI out is Low, the PI group controls the internal motor group to run at v1 speed toward High state, and monitors the PI out output value in real time. When the output value is High, the PI group controls the internal motor group to run N steps in the Low direction and run in the opposite direction at v2 speed until PI out is in P2 state, which means the reset is completed.

[0034] In this embodiment, the PI out state value jump point, that is, point P2, is used as the reset point. According to the different PI out states, the motor group is normally moved to the Low state for N steps, and then moved in the reverse direction at a slow speed to the P2 state. Since the initial running speed v1 is generally fast, the P2 state cannot be accurately captured. Therefore, in order to complete the reset under different PI out states, after moving from the High state to the Low state, the reverse direction is slowly run, thereby achieving accurate running to the P2 state.

[0035] Step S1.3: When the zoom ratio is 13x-18x, it represents long-distance shooting. At this time, the PI group controls the motor group inside the camera to move to the mechanical front dead point, and uses the mechanical front dead point as the reset point.

[0036] Step S2: After completing the above reset procedure, the internal motor group is located at the optimal initial position. When performing subsequent precise focusing, the zoom motor can be controlled to complete the position movement of the lens in a relatively short time. After obtaining the accurate zoom multiple instruction, the zoom motor moves a certain number of steps to complete the precise zoom.

[0037] Step S3, controlling the focus motor to move, further adjusting the image clarity, and obtaining an image with the highest clarity.

[0038] After the zoom motor completes the zoom, it is necessary to further control the focus motor to adjust the distance between the lens and the image sensor to obtain the clearest image. This embodiment uses a contrast detection method for automatic focusing. Specifically,

[0039] Step S3.1, capture a frame of image at the current focal length, and calculate the image clarity evaluation value FV1.

[0040] Step S3.2, set the initial moving direction and initial step size of the focus motor, move the lens and capture the next frame of image, and calculate the clarity evaluation value FV2 of the image. When FV2>FV1, continue to move in the same direction until FV2<FV1, which means that the image clarity decreases, move the focus motor in the opposite direction of the initial moving direction, and reduce the initial step size, repeat the above operation until the FV value that meets the preset accuracy requirements is obtained, and the autofocus is completed.

[0041] During the experimental teaching process, the teacher's teaching process is recorded in full through the recording and broadcasting teaching terminal, and the position of the mechanical arm is adjusted according to the shooting needs to change the shooting angle and distance of the high-definition recording and broadcasting camera. The zoom factor is obtained by the distance between the camera and the target object. After the internal motor group of the camera executes the reset program based on the zoom factor range, the zoom step is completed at a relatively fast speed. Then, the image clarity evaluation value comparison method is used to accurately focus and obtain the clearest image. By adjusting the movement direction and step length of the focus motor, a high-precision image is finally obtained. The camera automatic focusing method provided by the present invention sets the initial position of the PI group in three cases of macro shooting, medium-distance shooting and long-focal-length shooting by executing the reset program. The movement stroke of the internal motor group can be effectively reduced under different focal lengths, thereby reducing the imaging ghost time, improving the shooting accuracy, and realizing fast macro zoom. In the process of precise focusing, the movement direction and step length of the focus motor are adjusted in real time through image clarity evaluation, and finally an image that meets the accuracy requirements is obtained.

[0042] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for automatically adjusting the focus of a recording and broadcasting camera, characterized in that: The following steps are involved: Step S1, dividing different focal lengths according to different zoom multiple ranges, determining the best reset point of the motor group inside the camera based on the PI group output value, and performing motor group reset; Step S2, adjusting the movement direction and number of steps of the motor group based on the specific zoom multiple to complete the zoom; Step S3, capturing an image at the current focal length, calculating the definition evaluation value FV of the image, further adjusting the motor group, and performing definition evaluation value comparison, with the image with the highest FV value as the final target.

2. The automatic focusing method for a recording and broadcasting camera according to claim 1, characterized in that: In the step S1, the zoom multiple range is divided into macro focal length, medium focal length and long focal length in sequence from small to large; different motor reset procedures are performed for different focal lengths; specifically, Step S1.1, at the macro focal length, the PI group controls the motor group to move toward the mechanical rear dead point, with the mechanical rear dead point as the optimal reset point; Step S1.2, at the middle focal length, feedback control is performed according to the output state value PI out of the PI group; PI out includes two state values, High and Low; the critical value for jumping from the High state to the Low state is set to P1, and the critical value for jumping from the Low state to the High state is set to P2; When the initial state of PI out is High, the PI group controls the internal motor group to run at v1 speed to Low state, and detects the PI out state value in real time; when the PI out state value is P1, the PI group controls the internal motor group to continue running in the Low direction for N steps, and runs slowly in the reverse direction at v2 speed until PI out is P2 state, which means the reset is completed; the v2 speed is less than v1; When the initial state of PI out is Low, the PI group controls the internal motor group to run at v1 speed to High state, and monitors the PI out output value in real time. When the output value is High, the PI group controls the internal motor group to run N steps in the Low direction and run in the reverse direction at v2 speed until PI out is P2 state, which means the reset is completed; Step S1.3: At the long focal length, the PI group controls the motor group to move toward the mechanical front dead point, with the mechanical front dead point as the optimal reset point.

3. The automatic focusing method for a recording and broadcasting camera according to claim 2, characterized in that: When the zoom ratio is 1x-3x, it is classified as a macro focal range; when the zoom ratio is 3x-13x, it is classified as a medium-range focal range; and when the zoom ratio is 13x-18x, it is classified as a telephoto focal range.

4. The automatic focusing method for a recording and broadcasting camera according to claim 1, characterized in that: In step S2, after the motor group is reset, the zoom motor and focus motor inside the camera group are adjusted to specific positions according to the specific zoom factor, and then the focus motor is further adjusted based on the image clarity to change the distance between the lens and the image sensor to complete the image focusing.

5. The automatic focusing method for a recording and broadcasting camera according to claim 4, characterized in that: In step S3, the focus motor movement direction and number of steps are adjusted based on the image clarity evaluation value FV to complete the automatic focusing; specifically, Step S3.1, capturing a frame of image at the current focal length, and calculating the image clarity evaluation value FV1; Step S3.2, set the initial moving direction and initial step size of the focus motor, move the lens and capture the next frame of image, calculate the clarity evaluation value FV2 of the image; when FV2>FV1, continue to move in the same direction until FV2<FV1, which means that the image clarity decreases, move the focus motor in the opposite direction of the initial moving direction, and reduce the initial step size, repeat the above operation until the FV value that meets the preset accuracy requirements is obtained, and autofocus is completed.

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