Zoom tracking method and system with focus evaluation value feedback

Abstract

The present invention discloses a zoom tracking method and system with focus evaluation value feedback. After the zoom motor and the focus motor complete their movements, the system collects the focus evaluation values ​​of four consecutive frames of images for trend analysis. If the four frames of data show a continuously decreasing characteristic, the adjustment direction is set to the opposite direction. An adaptive compensation strategy is integrated with the dynamic feedback of the focus evaluation value. The feedback mechanism includes the object distance adjustment direction and the object distance adjustment step length. The mechanism constructs a closed-loop correction system by setting a coordinated control rule for the object distance adjustment direction and the step length.

Description

Technical Field

[0001] The present invention relates to the field of image processing, and in particular to a zoom tracking method and system with focus evaluation value feedback. Background Art

[0002] Blacklight full-color cameras feature zoom and autofocus functions. Their compact design, ease of use, and ease of assembly have made them widely used in video surveillance. Ensuring short zoom times, clear zooming throughout, and fast and accurate focusing are crucial for these cameras.

[0003] In a black-light full-color camera, the zoom lens and focus lens move independently, controlled by the zoom motor and focus motor, respectively. To ensure a clearly focused image during zooming, the zoom and focus motors must rotate in coordinated synchronization. In practical applications, due to the uncertainty of scene changes and object distance, moving the focus motor to maintain image clarity presents a significant challenge for zoom tracking algorithms. A commonly used approach in the prior art is to record the relative positions of the zoom and focus motors at different object distances, generate a group of zoom tracking curves, and then select a curve from the group that corresponds to the current object distance to drive the zoom and focus motors for zoom tracking. Most current algorithms face the challenge of selecting a curve from the group that reflects the actual object distance: multiple curves correspond to a single zoom motor position at the wide-angle end, making it difficult to select the correct tracking curve. Specifically, because depth of field is greater at the wide-angle end and smaller at the telephoto end, the curve group is denser at the wide-angle end and more dispersed at the telephoto end. Due to the error in the wide-angle curve, the error is amplified when tracking to the telephoto area, causing the image to be severely out of focus.

[0004] In summary, a zoom tracking method and system with focus evaluation value feedback is needed to address the shortcomings of the existing technology. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention provides a zoom tracking method and system with focus evaluation value feedback, aiming to solve the above problems.

[0006] To achieve the above-mentioned object, the present invention provides the following technical solution: a zoom tracking method with focus evaluation value feedback, comprising the following steps:

[0007] Step S1: System initialization and preparation: initializing the image sensor, image signal processing module, main control module, motor drive module, and zoom lens module, and pre-storing a group of zoom tracking curves at several object distances;

[0008] Step S2: Preliminary focusing and division, performing autofocus, obtaining the positions of the zoom motor and focus motor, and dividing the magnification range according to the dispersion between the zoom tracking curve corresponding to the near-end limit object distance and the zoom tracking curve corresponding to the far-end limit object distance;

[0009] Step S3: Calculate the zoom tracking curve corresponding to the actual object distance, analyze the zoom tracking curve group in the movement memory, find the two zoom tracking curves closest to the actual object distance, and calculate a new mid-range preset actual object distance zoom tracking curve;

[0010] Step S4: Dynamically adjust the focus, dynamically adjust the object distance through the focus evaluation feedback mechanism, and collect the focus evaluation values ​​of four consecutive frames of images for trend analysis after the movement of the zoom motor and the focus motor;

[0011] Step S5: Dynamically correct and adjust the step length. Calculate the step length according to the magnification range of the movement. Fine-tune the step length using the calculated step length and the focus evaluation value change rate to achieve variable magnification tracking.

[0012] Optionally, the zoom tracking curve group in step S1 includes a far-end limit object distance curve and a near-end limit object distance curve.

[0013] Optionally, step S3 is calculated in the following manner:

[0014] Set the zoom motor position x1 and the focus motor position y1 in the current clear focus state;

[0015] According to the current focus motor position, two close reference curves are selected from the pre-stored curve group. The upper preset curve is L1 and the lower preset curve is L2. The deviation degree r of the actual object distance zoom tracking curve is calculated:

[0016] r=(y1-y 12 ) / (y 11 -y 12 ),

[0017] Where y 11 is the position of the focus motor after the curve L1 is clearly focused when the zoom motor is at x1, and y 12 is the position of the focus motor after the curve L2 is clearly focused when the zoom motor is at x1;

[0018] The position of the actual object distance zoom tracking curve is determined according to the degree of deviation r, and the focus motor position corresponding to any zoom motor position is calculated by interpolation to obtain the mid-range preset actual object distance zoom tracking curve.

[0019] Optionally, the position of the actual object distance zoom tracking curve is determined according to the deviation degree r in the following manner:

[0020] If r is equal to zero, the actual object distance is the object distance corresponding to L2; if r is equal to 1, the actual object distance is the object distance corresponding to L1; if 0 < r < 1, the actual object distance is between the object distance corresponding to L1 and the object distance corresponding to L2.

[0021] Optionally, the focus motor position corresponding to any zoom motor position is calculated by interpolation in the following way:

[0022] P2 = r * (y 21 -y 22 ) + y 22 , where y 21 is the position of the focus motor after the curve L1 is in focus when the zoom motor is at x2, and y 22 is the position of the focus motor after the curve L2 is in focus when the zoom motor is at x2.

[0023] Optionally, in step S5, the step size is calculated according to the magnification range in which the movement mechanism is located in the following way:

[0024] Set the reference step size as S, the magnification of the movement mechanism as Z, the magnification of curve L1 as Z1, and the magnification of curve L2 as Z2;

[0025] If Z is less than or equal to Z1, then ;

[0026] If Z1 < Z ≤ Z2, then S(Z) = S * (1 - (Z - Z1) / (Z2 - Z1));

[0027] If Z is greater than Z2, then S(Z) = S * softmax(-γ(Z - Z2)), where γ is the attenuation coefficient.

[0028] Optionally, in step S5, the step size obtained by calculation and the change rate of the focus evaluation value are used to finely adjust the step size to achieve zoom tracking in the following way:

[0029] ,

[0030] where γ is the attenuation coefficient, is the change rate of the focus evaluation value.

[0031] Optionally, the attenuation coefficient γ is adjusted according to the zoom tracking effect in the following way: <00<

[0032] If is greater than zero and the evaluation value rises, the step size limit is relaxed to accelerate convergence; if is less than zero and the evaluation value drops, the step size is contracted in a square root relationship.

[0033] A zoom tracking system based on focus evaluation value feedback adopts the zoom tracking method based on focus evaluation value feedback, including an image sensor module, an image signal processing module, a main control module, a motor drive module and a zoom lens module.

[0034] Image sensor module, used for collecting raw image data;

[0035] An image signal processing module is used to perform denoising and sharpening processing on the image and calculate the focus evaluation value;

[0036] The main control module is the core control unit used to control other modules;

[0037] The motor drive module is used to control the zoom motor and the focus motor so that they move synchronously;

[0038] The zoom lens module is used to drive the zoom lens and focus lens to move independently to achieve optical magnification.

[0039] Optionally, the main control module includes a zoom tracking curve group acquisition unit, a focus curve partitioning and selection unit, a click control unit and a focus evaluation value feedback unit.

[0040] Zoom tracking curve group acquisition unit, used to collect and store zoom-focus motor position relationship data at different object distances;

[0041] A focus curve partitioning and selection unit, used to select or interpolate to generate a tracking curve according to the current object distance;

[0042] A motor control unit, used to send commands to drive the zoom and focus motors to move independently;

[0043] The focus evaluation value feedback unit is used to analyze the focus evaluation value trend and dynamically adjust the object distance tracking strategy.

[0044] Beneficial effects of the present invention:

[0045] 1. In the present invention, after the zoom motor and focus motor complete their movements, the system collects focus evaluation values ​​from four consecutive frames for trend analysis. If the four frames of data show a continuously decreasing characteristic, the adjustment direction is set to the opposite direction. This adaptive compensation strategy integrates dynamic feedback of the focus evaluation value. The feedback mechanism includes the object distance adjustment direction and the object distance adjustment step size. This mechanism establishes a closed-loop correction system by setting a coordinated control rule for the object distance adjustment direction and step size.

[0046] 2. In this invention, the object distance curve is dynamically adjusted by combining real-time feedback of the focus evaluation value. This ensures that even if there is a deviation in the initial curve selection, it can be quickly corrected, reducing the error rate of curve selection at the wide-angle end, improving the focusing accuracy at the telephoto end, and avoiding image blur caused by the accumulation of curve errors.

[0047] 3. In the present invention, a focus evaluation value feedback mechanism is introduced to monitor changes in image clarity in real time. When the object distance changes and the FV decreases, the tracking curve is automatically adjusted without interrupting the zoom process, thus realizing dynamic object distance tracking. Even if the target moves, the image can be kept clear, reducing the number of refocusing times caused by changes in object distance and improving zoom efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 The present invention is a flow chart of a method.

[0049] Figure 2 This is a group diagram of zoom tracking curves of the present invention.

[0050] Figure 3 This is a schematic diagram of the focus motor position calculation principle of the present invention.

[0051] Figure 4 This is a diagram of a theoretical curve and an actual motor motion curve of the present invention.

[0052] Figure 5 A schematic diagram of the system structure of the present invention. DETAILED DESCRIPTION

[0053] In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0054] like Figures 1 to 4 As shown, a zoom tracking method with focus evaluation value feedback includes the following steps:

[0055] Step S1: System initialization and preparation: initializing the image sensor, image signal processing module, main control module, motor drive module, and zoom lens module, and pre-storing a group of zoom tracking curves at several object distances;

[0056] Step S2: Preliminary focusing and division, performing autofocus, obtaining the positions of the zoom motor and focus motor, and dividing the magnification range according to the dispersion between the zoom tracking curve corresponding to the near-end limit object distance and the zoom tracking curve corresponding to the far-end limit object distance;

[0057] Step S3: Calculate the zoom tracking curve corresponding to the actual object distance, analyze the zoom tracking curve group in the movement memory, find the two zoom tracking curves closest to the actual object distance, and calculate a new mid-range preset actual object distance zoom tracking curve;

[0058] Step S4: Dynamically adjust the focus, dynamically adjust the object distance through the focus evaluation feedback mechanism, and collect the focus evaluation values ​​of four consecutive frames of images for trend analysis after the movement of the zoom motor and the focus motor;

[0059] Step S5: Dynamically correct and adjust the step length. Calculate the step length according to the magnification range of the movement. Fine-tune the step length using the calculated step length and the focus evaluation value change rate to achieve variable magnification tracking.

[0060] The method is implemented through the following specific contents:

[0061] First, the direction of the next rotation of the zoom motor is determined and the step length of the next movement of the zoom motor is calculated according to the current position of the zoom motor.

[0062] The magnification range can be divided according to the degree of dispersion between the zoom tracking curve corresponding to the near-end limit object distance and the zoom tracking curve corresponding to the far-end limit object distance in a pre-set manner. The range with a lower degree of dispersion between the zoom tracking curve corresponding to the near-end limit object distance and the zoom tracking curve corresponding to the far-end limit object distance is divided into a small magnification range, and the range with a higher degree of dispersion is divided into a large magnification range.

[0063] The greater the degree of dispersion between the zoom tracking curve corresponding to the near-end extreme object distance and the zoom tracking curve corresponding to the far-end extreme object distance, the greater the depth of field of the movement, and the larger the movement range of the focus motor. In order to ensure the time for the movement to zoom throughout the entire process and achieve a clear effect of zooming throughout the entire process, the zoom motor is moved with a larger step size in the small magnification segment, and the zoom motor is moved with a smaller step size in the large magnification segment to limit the focus motor from moving over a large range. Since the depth of field of the movement is large in the small magnification segment, moving the zoom motor with a larger step size will not cause an unacceptable degree of image blur.

[0064] Secondly, before starting the zoom, the automatic focus is successful and the zoom motor position and focus motor position of the successful focus are read. According to the zoom motor position and focus motor position, the corresponding zoom tracking curve at the current object distance is calculated as the zoom tracking curve followed by the zoom motor and focus motor for the next round of rotation.

[0065] like Figure 3 As shown, the two zoom tracking curves closest to the actual object distance are determined according to the current focus motor position, and are recorded as the upper preset zoom tracking curve L1 and the lower preset zoom tracking curve L2 respectively. Then, according to the focus motor position corresponding to the current zoom motor position in the lower preset zoom tracking curve and the degree of deviation of the current focus motor position, the zoom tracking curve followed by the zoom motor and the focus motor in the next round of rotation is fitted, and is recorded as the middle preset actual object distance zoom tracking curve L3.

[0066] Figure 3In the figure, P1 indicates that when the zoom motor is at x1, the scene with unknown object distance is photographed. After the focus is clear, the focus motor position is at y1. Curves L1 and L2 are the two preset zoom tracking curves closest to the current object distance calculated based on the focus motor position after the focus is clear. 11 、P 12 When the zoom motor is at x1, curves L1 and L2 are the positions of the focus motor after focus is clear. The following relationship can be used to express the degree of deviation between curve L3 and curves L1 and L2:

[0067] r=(y1-y 12 ) / (y 11 -y 12 ).

[0068] When the divisor is 0, it means that L1 and L2 coincide, that is, the current point is on the preset zoom tracking curve. When r = 0, it means that P1 is on curve L2. In other words, the actual object distance of the current shot is the object distance corresponding to curve L2. When r = 1, it means that P1 is on curve L1. In other words, the actual object distance of the current shot is the object distance corresponding to curve L1. When r is between 0 and 1, it means that the actual object distance of the current shot is between the object distances corresponding to curves L1 and L2. Then, the position of the focus motor when the zoom motor is at any specified position when shooting the scene at the current object distance is calculated using the following relationship:

[0069] P2=r*(y 21 -y 22 )+y 22 , where y 21 is the position of the focus motor after the curve L1 is clearly focused when the zoom motor is at x2, and y 22 The position of the focus motor after the curve L2 is clearly focused when the zoom motor is at x2.

[0070] Figure 3 The data shows that as the optical magnification increases, the deviation between the far-end limit object distance curve and the near-end limit object distance curve tends to increase. It is worth noting that the mid-range preset object distance zoom tracking curve calculated based on the extrapolation of small magnification data has a low match with the actual theoretical curve in the low magnification range. The error mainly comes from the nonlinear characteristic differences caused by the magnification change. To solve this error accumulation problem, this solution proposes a progressive approximation method based on dynamic depth of field adjustment:

[0071] 1. The far-end limit object distance curve is used as the reference tracking trajectory in the large depth of field magnification range, making full use of the allowable deviation characteristics of the large depth of field range and reducing the calculation complexity.

[0072] 2. The mid-depth of field magnification range generates a mid-range preset tracking curve by interpolating the far / near extreme object distance curves to achieve balanced control of error distribution.

[0073] 3. For the small depth-of-field magnification range, based on the real-time zoom / focus motor position parameters, select the two reference curves with the closest spatial distance for iterative calculation to ensure the tracking accuracy.

[0074] This solution innovatively introduces a range constraint mechanism for depth-of-field adaptation. By gradually shrinking the displacement tolerance interval of the focus motor in stages, it realizes the gradual approximation of the tracking curve to the theoretical clear point. This hierarchical control strategy not only ensures the system response speed but also significantly improves the focusing accuracy within the full magnification range.

[0075] Aiming at the error accumulation problem that exists when the traditional zoom system calculates the tracking curve of the preset object distance at the middle end using small magnification data, this solution proposes an adaptive compensation strategy that integrates the dynamic feedback of the focus evaluation value. The feedback mechanism includes the object distance adjustment direction and the object distance adjustment step size. By setting the coordinated control rules for the object distance adjustment direction and step size, a closed-loop correction system is constructed.

[0076] The specific implementation method is that after the zoom motor and the focus motor complete their movements, the system collects the focus evaluation values of four consecutive frames of images for trend analysis, such as quantization indexes based on gradient intensity or frequency domain energy. If the four-frame data shows a continuous decreasing characteristic, the adjustment direction is set to the opposite direction.

[0077] As Figure 4 shown, based on the depth-of-field characteristics of the optical system and the mechanical accuracy calibration, combined with the preset object distance adjustment step size parameter, a controlled oscillation trajectory of the focus motor near the theoretical clear point is formed. This solution proposes a dynamic adjustment step size model to calibrate the adjustment step size. Through the joint modeling of the optical depth-of-field constraint and the mechanical transmission characteristics, the non-linear adaptive control of the step size with respect to the magnification change is achieved.

[0078] The specific calibration steps are as follows:

[0079] Step 1: Set the reference step size S. This parameter corresponds to the minimum effective displacement that can make the focus evaluation value reach the preset threshold at a specific object distance.

[0080] Step 2: Calculate the adjustment step size according to the magnification range where the movement mechanism is located.

[0081] 1. In the low magnification range, Z ≤ Z1: The depth-of-field range is relatively wide. Use the square root decay function to expand the step size:

[0082] ,

[0083] In this stage, the focus is on optimizing the focus speed. By increasing the step size, it quickly crosses the broad blurred area.

[0084] 2. In the medium magnification transition range, Z1 < Z ≤ Z2: The depth-of-field starts to shrink significantly. Enable the linear decay mode for smooth transition:

[0085] S(Z)=S*(1-(Z-Z1) / (Z2-Z1))

[0086] This function ensures that the step reduction rate matches the depth of field change slope, avoiding the risk of defocusing.

[0087] 3. High-rate precision domain Z is greater than Z2: Use exponential decay function to enhance stability:

[0088] S(Z)=S*softmax(-γ(Z-Z2)),

[0089] The attenuation coefficient It can be adjusted according to the zoom tracking effect of the actual scene.

[0090] Step 3: Implement dynamic correction and adjust step size

[0091] Introducing the rate of change of focus evaluation value As a fine-tuning factor:

[0092] The attenuation coefficient γ can be adjusted according to the zoom tracking effect of the actual scene. When the evaluation value is greater than zero and increases, the step size limit is appropriately relaxed to accelerate convergence; when When it is less than zero and the evaluation value decreases, the step size is reduced in a square root relationship.

[0093] After the zoom motor and focus motor complete their movements, the system collects focus evaluation values ​​from four consecutive frames for trend analysis. If the four frames show a continuously decreasing characteristic, the adjustment direction is set to the opposite direction. This adaptive compensation strategy integrates dynamic feedback of the focus evaluation value. The feedback mechanism includes the object distance adjustment direction and the object distance adjustment step size. This mechanism establishes a closed-loop correction system by setting a coordinated control rule for the object distance adjustment direction and step size.

[0094] Combined with real-time feedback from focus evaluation values, the object distance curve is dynamically adjusted to ensure that even if there are deviations in the initial curve selection, they can be quickly corrected, reducing the error rate of curve selection at wide-angle end, improving focus accuracy at telephoto end, and avoiding image blur caused by accumulated curve errors.

[0095] A focus evaluation value feedback mechanism is introduced to monitor changes in image clarity in real time. When changes in object distance cause a drop in FV, the tracking curve is automatically adjusted without interrupting the zoom process, achieving dynamic object distance tracking. This keeps the image clear even when the target moves, reduces the number of refocusing times caused by changes in object distance, and improves zoom efficiency.

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A zoom tracking method based on focus evaluation value feedback, characterized in that: It includes the following steps: Step S1: System initialization and preparation. Initialize the image sensor, image signal processing module, main control module, motor drive module, and zoom lens module, and pre-store a group of zoom tracking curves at several object distances. Step S2: Preliminary focusing and division. Perform autofocus, obtain the positions of the zoom motor and focus motor, and divide the magnification range according to the dispersion degree between the zoom tracking curve corresponding to the proximal limit object distance and the zoom tracking curve corresponding to the distal limit object distance. Step S3: Calculate the zoom tracking curve corresponding to the actual object distance. By analyzing the group of zoom tracking curves in the movement mechanism memory, find the two zoom tracking curves closest to the actual object distance, and calculate a new mid-end preset actual object distance zoom tracking curve. Step S4: Dynamically adjust the focus. Dynamically adjust the object distance through the focus evaluation feedback mechanism. After the movement of the zoom motor and focus motor, collect the focus evaluation values of four consecutive frames of images for trend analysis. Step S5: Dynamically correct the adjustment step size. Calculate the step size S(Z) according to the magnification range where the movement mechanism is located, and fine-tune the step size through the calculated step size and the change rate of the focus evaluation value to achieve zoom tracking. Fine-tune the step size through the calculated step size and the change rate of the focus evaluation value to achieve zoom tracking, by the following method: ， Where γ is the attenuation coefficient, To focus on the rate of change of evaluation value; The attenuation coefficient γ is adjusted according to the zoom tracking effect, by the following method: like If the evaluation value is greater than zero, the step size limit is relaxed to accelerate convergence. If it is less than zero, the evaluation value decreases, and the step size is reduced in a square root relationship.

2. The zoom tracking method based on focus evaluation value feedback according to claim 1, characterized in that: In the said step S1, the group of zoom tracking curves includes the distal limit object distance curve and the proximal limit object distance curve.

3. The zoom tracking method based on focus evaluation value feedback according to claim 1, characterized in that: In the said step S3, it is calculated by the following method: Set the position x1 of the zoom motor and the position y1 of the focus motor in the current clear focus state; According to the current position of the focus motor, select two close reference curves from the pre-stored curve group. The upper preset curve is L1, and the lower preset curve is L2, and calculate the deviation degree r of the actual object distance zoom tracking curve: r=(y1-y 12 ) / (y 11 -y 12 ) Where y 11 is the position of the focus motor after the curve L1 is clearly focused when the zoom motor is at x1, and y 12 is the position of the focus motor after the curve L2 is clearly focused when the zoom motor is at x1; Judge the position of the actual object distance zoom tracking curve according to the deviation degree r, and calculate the position of the focus motor corresponding to any zoom motor position through interpolation to obtain the mid-end preset actual object distance zoom tracking curve.

4. The zoom tracking method based on focus evaluation value feedback according to claim 3, characterized in that: The judgment of the position of the actual object distance zoom tracking curve according to the deviation degree r is carried out by the following method: If r is equal to zero, the actual object distance is the object distance corresponding to L2; if r is equal to 1, the actual object distance is the object distance corresponding to L1; if 0 < r < 1, the actual object distance is between the object distance corresponding to L1 and the object distance corresponding to L2.

5. The zoom tracking method based on focus evaluation value feedback according to claim 4, characterized in that: The calculation of the position of the focus motor corresponding to any zoom motor position through interpolation is carried out by the following method: P2=r*(y 21 -y 22 )+y 22 , where y 21 is the position of the focus motor after the curve L1 is clearly focused when the zoom motor is at x2, and y 22 The position of the focus motor after the curve L2 is clearly focused when the zoom motor is at x2.

6. The zoom tracking method based on focus evaluation value feedback according to claim 1, characterized in that: In the said step S5, the step size S(Z) is calculated according to the magnification range where the movement mechanism is located, by the following method: Set the reference step size as S, the magnification where the movement mechanism is located as Z, the magnification of curve L1 as Z1, and the magnification of curve L2 as Z2; If Z is less than or equal to Z1, then ; If Z1 < Z ≤ Z2, then S(Z) = S * (1 - (Z - Z1) / (Z2 - Z1)); If Z is greater than Z2, then S(Z) = S * softmax(-γ(Z - Z2)), where γ is the attenuation coefficient.

7. A zoom tracking system based on focus evaluation value feedback, adopting the zoom tracking method based on focus evaluation value feedback according to any one of claims 1 to 6, characterized in that: It includes an image sensor module, an image signal processing module, a main control module, a motor drive module, and a zoom lens module, The image sensor module is used to collect raw image data; An image signal processing module is used to perform denoising and sharpening processing on the image and calculate the focus evaluation value; The main control module is the core control unit used to control other modules; The motor drive module is used to control the zoom motor and the focus motor so that they move synchronously; The zoom lens module is used to drive the zoom lens and focus lens to move independently to achieve optical magnification.

8. The zoom tracking system based on focus evaluation value feedback according to claim 7, characterized in that: The main control module includes a zoom tracking curve group acquisition unit, a focus curve partitioning and selection unit, a click control unit and a focus evaluation value feedback unit. Zoom tracking curve group acquisition unit, used to collect and store zoom-focus motor position relationship data at different object distances; A focus curve partitioning and selection unit, used to select or interpolate to generate a tracking curve according to the current object distance; A motor control unit, used to send commands to drive the zoom and focus motors to move independently; The focus evaluation value feedback unit is used to analyze the focus evaluation value trend and dynamically adjust the object distance tracking strategy.

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