CN118338123B - Automatic focusing method and system based on binocular parallax approximate matching - Google Patents
Automatic focusing method and system based on binocular parallax approximate matching Download PDFInfo
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Abstract
The invention provides an automatic focusing method and system based on binocular parallax approximate matching, wherein the method comprises the following steps: acquiring image data of the binocular camera A, B to obtain a corresponding matrix of image pixel brightness; performing exclusive OR operation on the highest bit of each same pixel point in the matrix of the image pixel brightness to obtain a parallax binarization matrix of two frames of images; calculating parallax data of a target area to be focused according to the parallax binarization matrix; obtaining an optimal focal length position corresponding to the binocular camera A, B according to the parallax-optimal focal length position lookup table; respectively comparing the distance D between the current initial focal length position of the binocular camera A, B and the corresponding optimal focal length position; and (5) performing automatic focusing according to the distance D. The invention can quickly find the optimal focusing position of the clear image and improve the focusing speed.
Description
Technical Field
The invention relates to the field of machine vision, in particular to an automatic focusing method and system based on binocular parallax approximate matching.
Background
Binocular cameras are becoming increasingly popular for use in surveillance, augmented reality, and robotic vision. Compared with a monocular camera, the binocular camera has the advantages that the relative distance of the target can be obtained through parallax calculation of the target image on the two cameras, so that a three-dimensional visual image can be realized, or the robot can control the grabbing action according to the relative distance of the target object obtained through parallax calculation. In addition, the distance information of the target object calculated by the parallax of the binocular camera can help to determine the in-focus position information for obtaining a clear image. However, the computation of binocular camera parallax requires complex visual matching algorithms, and the accuracy of parallax is affected by image sharpness and pixel resolution. Therefore, the key of realizing automatic focusing through binocular camera image parallax is how to quickly obtain parallax data, and an effective and concise vision matching parallax calculation method for automatic focusing of a binocular camera is needed.
Disclosure of Invention
In order to solve the problems, the invention provides an automatic focusing method and an automatic focusing system based on binocular parallax approximate matching, which can quickly find the optimal focusing position of a clear image and improve the focusing speed.
In a first aspect, the present invention provides an auto-focusing method based on binocular parallax approximate matching, including:
image data of a binocular camera A, B is acquired, wherein the binocular camera A, B can automatically focus, and optical axes of the binocular camera and the binocular camera are parallel to each other;
Processing the image data of the binocular camera A, B respectively to obtain a matrix corresponding to the brightness of the pixels of the image of the binocular camera A, B;
performing exclusive OR operation on the highest bit of each same pixel point in the matrix of the pixel brightness of the binocular camera A, B to obtain a parallax binarization matrix of two frames of images, wherein i and j are row and column pixel coordinates in a target image area to be focused respectively;
calculating parallax data of a target area to be focused according to the parallax binarization matrix;
obtaining an optimal focal length position x Aest、xBest corresponding to the binocular camera A, B according to the parallax data and a parallax-optimal focal length position lookup table which is determined and established in advance;
Respectively comparing the distance D between the current initial focal length position x A、xB of the binocular camera A, B and the corresponding optimal focal length position x Aest、xBest;
according to the distance D, the binocular camera A, B performs auto-focusing.
Further, the automatic focusing performed by the binocular camera A, B according to the distance D includes:
Determining a focal length moving mode of the binocular camera A, B according to the distance D;
according to the focal length moving mode, the binocular camera A, B performs automatic focusing.
Further, the determining the focal length moving manner of the binocular camera A, B according to the distance D includes:
When (when) And (2) andAt minimum resolution, the binocular camera A, B moves the focal length in the opposite direction with the same small step S min, i.e., AB moves to x A-Smin and x B+Smin, respectively, and measures the image sharpness index Q, where；
When (when)The focal length of the binocular camera A, B is moved to two sides of the same distance d= (d A+dB)/4 from x Aest and x Best, respectively, that is, the binocular camera A, B is moved to x Aest -d and x Best +d, respectively, and the image definition index Q is measured;
When (when) The focal length of the binocular camera A is moved to x Aest -Mx and x Aest+Mx/2, the focal length of the binocular camera B is moved to x Best -Mx/2 and x Best+Mx, and the image definition index Q is measured;
and further adopting a least square method to calculate and approximate the optimal focal length position according to the image definition index Q.
Further, wherein the method comprises:
When (when) The calculating and approaching the best focus position by a least square method according to the image definition index Q comprises the following steps:
If it is Confirming that the focal length starting position of the binocular camera A, B is near the peak mountain top position, and calculating by adopting a least square method to obtain a more accurate optimal focal length position;
If it is Estimating the best focal length position by a least square method in the negative directions of x Aest and x Best of the peak value;
If it is The peak value is in the positive direction of x Aest and x Best, and the best focal length position is estimated by adopting a least square method;
If it is Then x Aest and x Best are valley point positions, then the parallax data is returned and recalculated and the best focus position x Aest、xBest corresponding to the parallax of the binocular camera A, B is determined.
Further, the calculating and approximating the best focus position according to the image definition index Q by using a least square method further includes:
and (3) approximating the extreme point of the search f' (x) =0 by adopting a parabolic interpolation method, and rapidly finding the optimal focusing position of the clear image.
Further, the processing the image data of the binocular camera A, B respectively, correspondingly obtaining a matrix of the brightness of the image pixels of the binocular camera A, B, includes:
the image data of the binocular camera A, B is processed by an automatic gain Amplifier (AGC) and an analog-to-digital converter (ADC) in sequence to obtain processed image data;
From the processed image data, matrices I A (I, j) and I B (I, j) for reflecting the pixel brightness of one frame of the image of the binocular camera A, B are established.
The automatic gain amplifier AGC is used for automatically adjusting the brightness of the image pixels according to the illuminance condition; the analog-to-digital converter ADC is used for converting brightness analog signals of all pixels to obtain digital brightness values, and the digital brightness values are represented in a binary mode.
Further, wherein the method further comprises:
Respectively carrying out differential operation on each row of adjacent elements of the matrixes I A (I, j) and I B (I, j) of the image pixel brightness of the binocular camera A, B to obtain a differential result;
Calculating the absolute value of the difference result, wherein the maximum value of the absolute value in a certain area in the image is an image definition index Q Amax、QBmax of the area;
Wherein, ，。
Further, wherein the parallax-best focus position lookup table is pre-determined and established by:
Placing standard images at different distances, and adjusting the focal length of the binocular camera A, B to enable the images to reach a definition index Q Amax、QBmax respectively, and recording the numerical value of the focal length position and the corresponding parallax numerical value at the moment; wherein the corresponding parallax numerical value is calculated according to the parallax binarization matrix;
And establishing a parallax-optimal focal length position lookup table according to the values of the focal length positions recorded on the different distances and the corresponding parallax values.
Further, the performing an exclusive-or operation on the highest bit of each same pixel point in the matrix of the pixel brightness of the binocular camera A, B to obtain a parallax binarization matrix of two frames of images includes:
The brightness value of the image pixel of the binocular camera A, B is expressed by adopting 8-bit binary system;
performing exclusive OR operation on the 8 th bit of each same pixel point in the matrix of the pixel brightness of the binocular camera A, B to obtain a parallax binarization matrix of two frames of images, wherein the calculation formula is as follows:
；
Wherein BW (I, j) is a binarization matrix composed of 0 and 1, MSB [ I A(i,j)]、MSB[IB (I, j) ] represents taking the highest bit of two frames of image pixel points of the binocular camera A, B, the value of BW (I, j) is 0 or 1, and the value of BW (I, j) is exclusive OR logic operation.
In a second aspect, the present invention provides an auto-focusing system based on binocular parallax approximate matching, comprising:
the image acquisition unit is used for acquiring image data of the binocular camera A, B, wherein the binocular camera A, B can automatically focus and optical axes of the binocular camera A, B and the binocular camera are parallel to each other;
the image processing unit is used for respectively processing the image data of the binocular camera A, B to correspondingly obtain a matrix of the image pixel brightness of the binocular camera A, B;
The exclusive-or operation unit is used for carrying out exclusive-or operation on the highest bit of each same pixel point in the matrix of the pixel brightness of the binocular camera A, B to obtain a parallax binarization matrix of two frames of images, wherein i and j are row and column pixel coordinates in a target image area to be focused respectively;
the parallax calculating unit is used for calculating parallax data of the target area to be focused according to the parallax binarization matrix;
The searching unit is used for obtaining an optimal focal length position x Aest、xBest corresponding to the binocular camera A, B according to the parallax data and a parallax-optimal focal length position lookup table which is determined and established in advance;
A comparing unit, configured to compare a distance D between the current start focal length position x A、xB of the binocular camera A, B and the corresponding optimal focal length position x Aest、xBest;
And the focusing unit is used for automatically focusing the binocular camera A, B according to the distance D.
Compared with the prior art, the invention has the beneficial effects that:
The visual matching parallax calculation method is effective and simple, and parallax data can be quickly obtained; the weighted least square method can be used for fusing the measurement data of the binocular camera A, B, the measurement frequency is reduced, the focusing speed is improved, the parabolic interpolation method is adopted to approach the extreme point of searching f' (x) =0, and the optimal focusing position of the clear image is quickly found, so that automatic focusing is realized. In addition, in the singlechip processing program, the accuracy and the credibility of parallax data can be improved through corresponding regional statistical analysis and processing.
Drawings
FIG. 1 is a schematic block diagram of an auto-focus system based on binocular disparity approximation matching of the present invention;
FIG. 2 is a schematic diagram of the calculated effects according to the technical principles of the present invention;
fig. 3 is a flowchart of an auto-focusing method based on binocular parallax approximate matching according to an embodiment of the present invention;
Fig. 4 is a schematic diagram of a maximum value position estimated by a weighted least square method in case 1 in an auto-focusing method based on binocular parallax approximate matching according to an embodiment of the present invention;
fig. 5 is a schematic diagram of a maximum value position estimated by a weighted least square method in case 1 in case 2 in an auto-focusing method based on binocular parallax approximate matching according to an embodiment of the present invention;
Fig. 6 is a schematic diagram of a maximum value position estimated by a weighted least square method in case 2 in the binocular parallax approximate matching-based auto focusing method according to an embodiment of the present invention;
fig. 7 is a schematic diagram of a maximum value position estimated by a weighted least square method in case 3 in an auto-focusing method based on binocular parallax approximate matching according to an embodiment of the present invention;
Fig. 8 is a schematic diagram of a unit module of an auto-focusing system based on binocular parallax approximate matching according to another embodiment of the present invention.
Detailed Description
In order that the objects and advantages of the invention will become more apparent, the invention will be further described with reference to the following examples; it should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are merely for explaining the technical principles of the present invention, and are not intended to limit the scope of the present invention.
It should be noted that, in the description of the present invention, terms such as "upper," "lower," "left," "right," "inner," "outer," and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, which are merely for convenience of description, and do not indicate or imply that the apparatus or elements must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.
Furthermore, it should be noted that, in the description of the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those skilled in the art according to the specific circumstances.
The invention adopts the highest order of two brightness matrix elements of the binocular image to carry out exclusive OR operation, thus obtaining the approximate parallax binarization image. According to the width of the parallax image row in the x direction, a parallax approximate value of a parallax target object can be obtained, so that the relative distance of the target object can be judged, and the preliminary focusing position of the lens is determined according to the calibrated focusing position during initialization. Further, the parabolic interpolation method is adopted to approach the extreme point of f' (x) =0, so that the best focusing position of the clear image is quickly found.
Fig. 1 is a schematic block diagram of an auto-focusing system based on binocular parallax approximate matching according to the present invention, and first, the technical principle of the present invention is described as follows:
According to the epipolar geometry principle of the binocular camera, as shown in fig. 1, when the binocular camera is installed, the optical axes are set to be parallel to each other, so that the corresponding polar lines between the left image and the right image are ensured to be parallel to each other and positioned on the same horizontal scanning line of the image. At this time, the binocular camera is a parallel stereoscopic model, so the disparity vector is parallel to the horizontal scan line of the image, and the disparity vector is actually degraded to a scalar, i.e.: Wherein Z is the distance between the target and the base line; x A、xB is the horizontal coordinate of the A, B binocular camera; d is parallax equal to the difference of two coordinates; b is the distance of A, B binocular cameras on the base line, and f i is the imaging image distance of A, B two identical binocular cameras, i.e. the optimal image distance in focusing. When the binocular camera position is fixed, B is a fixed value. Therefore, the parallax is inversely proportional to the target distance. In addition, the relation of the lenses Wherein f is the focal length, f i is the image distance, Z is the target distance, and the former formula is substituted into the latter formula to obtain。
Therefore, different target distances correspond to different parallaxes d, and different optimal focusing image distances f i.fi are parameters to be approximated by the invention. However, since the quantization error of the image is a quantization error brought by the pixels and a calculation error caused by the blurred image when not focusing, the calculation of f i by d only causes a large error, so d can only be used as a preliminary estimation of f i, and then further focusing is performed by combining other methods.
The binocular camera parallax calculation requires a complex visual matching algorithm, so that automatic focusing is realized through binocular camera image parallax, and the key is how to quickly obtain parallax data, namely an effective and simple visual matching parallax calculation method for binocular camera automatic focusing is needed.
Therefore, the invention adopts the exclusive OR operation of the highest position of each pixel in the two brightness matrixes of the binocular image to obtain a binary matrix BW (i, j) reflecting the parallax of the binocular image, the width interval of the area with the value of '1' in the row direction reflects the approximate value of the parallax, and the unit is the number of pixel points. The disparity value and the corresponding preliminary estimated value of focal length or lens position can be measured by using a standard graph on a standard distance in the production line or initialization, and are stored in a designated area of a read-only memory space of the system in the form of a lookup table.
When the method is used, the corresponding focal distance or lens position is found from the parallax-focal distance corresponding relation table of the read-only memory space according to the parallax approximate values of different areas on the image, and the lens is adjusted and moved to the initially estimated position. The distance distribution condition of the target object in the image can be directly known from the point width of the binarized image BW (i, j), so that the target objects at different distances can be focused according to the requirements. If only the focus center area target is required, the lens can be further adjusted to the optimal position of the focus center area target by the parabolic interpolation method described below. If it is also desired to focus on targets in other areas and distances, the above process may be repeated, moving the lens adjustment to a position that focuses on a preliminary estimate of the area target based on the parallax data for that area.
Fig. 2 shows an effect schematic diagram calculated based on the above principle, 1) and 2) in fig. 2 are two images obtained by a A, B camera, 3) is a binary image BW (i, j) reflecting binocular image parallax obtained by the above method, and 4) is an image in which three images reflecting the relation between A, B brightness and parallax image BW are superimposed. 3) A, B in fig. 2, the width of the area of white being '1' in the parallax binarized image BW (i, j) reflects the magnitude of parallax, and as can be seen from 3) in fig. 2, the width of the image with the center area being far from the camera is the narrowest, and the width of the image with the peripheral edge area being closer to the camera is the wider gradually. Because the influence of illumination and reflectivity can cause A, B parallax binarized image BW to generate certain error, the accurate focusing position of the image BW needs a subsequent parabolic interpolation method to carry out checksum approximation. As can be seen from 3) in fig. 2, the width of the continuous connected region in the vertical y direction is kept, and the error of A, B parallax data reflected by the continuous connected region is smaller, so that the accuracy and the reliability of the parallax data can be improved through corresponding region statistical analysis processing in the singlechip processing program.
Fig. 3 is a flowchart of an auto-focusing method 100 based on binocular parallax approximate matching according to an embodiment of the present invention, referring to fig. 3, the method 100 includes:
s110: image data of a binocular camera A, B is acquired, wherein the binocular camera A, B can automatically focus, and optical axes of the binocular camera and the binocular camera are parallel to each other;
S120: processing the image data of the binocular camera A, B respectively to obtain a matrix corresponding to the brightness of the pixels of the image of the binocular camera A, B;
In the step S120, specifically, both the auto-focusing binocular camera A, B are internally provided with an AGCA, an AGCB automatic gain amplifier, an ADCA and an ADCB analog-to-digital converter, and the collected image data of the binocular camera A, B is processed by the automatic gain amplifier AGC and the analog-to-digital converter ADC in sequence to obtain processed image data; according to the processed image data, a matrix I A (I, j) and a matrix I B (I, j) for reflecting the pixel brightness of one frame of image of the binocular camera A, B are established;
The automatic gain amplifier AGC is used for automatically adjusting the brightness of the image pixels according to the illuminance condition; the analog-to-digital converter ADC is configured to convert analog luminance values of all pixels to obtain a digital luminance value, where the digital luminance value is represented by a binary system, and the luminance value falls within a range that can be represented by the binary system, typically, the binary system is 8 bits, that is, the luminance value should fall within a range of 0 to 255.
S130: performing exclusive OR operation on the highest bit of each same pixel point in the matrix of the pixel brightness of the binocular camera A, B to obtain a parallax binarization matrix of two frames of images, wherein i and j are row and column pixel coordinates in a target image area to be focused respectively;
In this step S130, the brightness value of the image pixel of the binocular camera A, B is represented by 8-bit binary;
Performing exclusive or operation on the 8 th bit of each same pixel point in the matrix of the pixel brightness of the corresponding binocular camera A, B image to obtain a parallax binarization matrix of two frames of images, wherein the calculation formula is as follows:
；
Wherein BW (I, j) is a binarization matrix composed of 0 and 1, MSB [ I A(i,j)]、MSB[IB (I, j) ] represents taking the highest bit of two frames of image pixel points of the binocular camera A, B, the value of BW (I, j) is 0 or 1, and the value of BW (I, j) is exclusive OR logic operation.
The binary image BW (i, j) consisting of 0 and 1, which is obtained after the exclusive OR of the most significant bits of the two images, actually represents parallax images of the two images, and when the brightness values of corresponding pixels of the AB two images are smaller than 128 or larger than 128, the corresponding point is 0, which indicates that the two images are approximately the same on the corresponding pixels; if one of the images AB corresponds to a pixel with a luminance value greater than 128 and the other image AB is less than 128, the corresponding point is 1, and vice versa, i.e. the two images differ in the pixel.
S140: calculating parallax data of a target area to be focused according to the parallax binarization matrix;
In step S140, the lateral ordinate distance of the image edge according to the parallax binarization matrix BW (i, j) obtained in step S130 represents parallax, and the preliminary best focus position, i.e. the current start focus position x A、xB, can be obtained from the parallax information at the beginning of focusing.
S150: obtaining an optimal focal length position x Aest、xBest corresponding to the binocular camera A, B according to the parallax data and a parallax-optimal focal length position lookup table which is determined and established in advance;
this step S150 includes:
S151: calculating an image definition index, specifically including:
S1511: respectively carrying out differential operation on each row of adjacent elements of the matrixes I A (I, j) and I B (I, j) of the image pixel brightness of the binocular camera A, B to obtain a differential result;
S1512: calculating an absolute value of the difference result, wherein the maximum value of the absolute value in a certain area in the image is an image definition index Q Amax、QBmax of the area:
，
；
S152: the parallax-best focus position lookup table is pre-determined and established, and specifically comprises the following steps:
S1521: placing standard images at different distances, and adjusting the focal length of the binocular camera A, B to enable the images to reach a definition index Q Amax、QBmax respectively, and recording the numerical value of the focal length position and the corresponding parallax numerical value at the moment; the corresponding parallax numerical value is further calculated according to the parallax binarization matrix obtained in the steps S110-S130;
s1522: and establishing a parallax-optimal focal length position lookup table according to the values of the focal length positions recorded on the different distances and the corresponding parallax values.
S160: respectively comparing the distance D between the current initial focal length position x A、xB of the binocular camera A, B and the corresponding optimal focal length position x Aest、xBest;
In step S160, since the camera records the position of the stepper motor in real time in the memory of the singlechip, and further records the current focal length position, the current start focal length position at any focusing time can be determined based on the current start focal length position, and then the focal length movement mode of the subsequent binocular camera A, B is further determined according to the distance by comparing the current start focal length position x A,xB (i.e. the initial position at the beginning of focusing) with the corresponding binocular camera A, B obtained in step S150.
S170: according to the distance D, the binocular camera A, B performs auto-focusing.
The step S170 specifically includes:
According to the distance D, a focal length moving mode of the binocular camera A, B is determined, and according to the focal length moving mode, the binocular camera A, B performs automatic focusing, and the specific situations are as follows:
Case 1: when (when) And (2) andFor minimum resolution, it is indicated that binocular camera A, B is currently in the vicinity of the predetermined best focus position, or that binocular camera A, B is currently in the peak mountain top position of the focus-image sharpness index curve, then binocular camera A, B moves the focus in the opposite direction with the same small step S min, i.e., binocular camera A, B moves to x A-Smin and x B+Smin, respectively, and measures the image sharpness index Q, where; And measuring an image definition index Q, and carrying out further operation according to different measurement results:
1.1: if it is Confirming that the focal length starting position of the binocular camera A, B is near the peak mountain top position, and calculating by adopting a subsequent least square method to obtain a more accurate optimal focal length position;
1.2: if it is Estimating the best focal length position by a least square method in the negative directions of x Aest and x Best of the peak value;
1.3: if it is The peak value is in the positive direction of x Aest and x Best, and the best focal length position is estimated by adopting a least square method;
1.4: if it is Then x Aest and x Best are valley point positions and it is necessary to go back to the first step S110 to recalculate the parallax value to the parallax best focus positions x Aest and x Best.
Case 2: when (when)When the binocular camera A, B is currently located at the peak mountain position of the focus-image definition index curve, the focus of the binocular camera A, B is respectively moved to two sides with the same distance d= (d A+dB)/4 from x Aest and x Best, namely, the binocular camera A, B is respectively moved to x Aest -d and x Best +d, the image definition index Q is measured, and the position approaching to the optimal focus is calculated by adopting the subsequent least square method;
Case 3: when (when) When the binocular camera A, B is currently positioned at the peak mountain position of the focus-image definition index curve, the focus of the binocular camera A is moved to x Aest -Mx and x Aest+Mx/2, the focus of the binocular camera B is moved to x Best -Mx/2 and x Best+Mx, and the image definition index Q is measured; and according to the 4 measured values, calculating an approximate optimal focal length position by adopting a subsequent least square method.
Under the above conditions, the binocular camera A, B measures the image definition index Q at different positions, and even if the data of the binocular camera A, B are different but have strong correlation, the weighted least square method can be used for fusing the AB measurement data to reduce the measurement times and improve the focusing speed.
Further, the calculating and approximating the best focus position according to the image definition index Q by using a least square method further includes:
and (3) approximating the extreme point of the search f' (x) =0 by adopting a parabolic interpolation method, and rapidly finding the optimal focusing position of the clear image.
Further, for 1.1, 1.2 and 1.3 in case 1, the camera a measures the image sharpness index on x A and x A-smin, the binocular camera B measures the image sharpness index on x B and x B+smin, the binocular camera A, B uses x A and x B as central origins, s min as normalized distance units, converts the position coordinates into normalized coordinates, the self-measured data weight is 1, the non-self-measured data weight is 1/2, and a weighted least squares method is adopted to fit the quadratic parabolic curve:。
According to the above settings, the measurement matrix H and the weight matrix of the binocular camera A, B are W A and W B, the fitting matrices M A and M B are obtained by a weighted least squares method, the corresponding parabolic curve coefficients are obtained after substituting the measured data, and the estimated maximum positions x Amax and x Bmax are finally calculated. As shown in fig. 4, it shows the normalized coordinate positions of the maximum values of Q (x A-smin)=4,Q(xA)=9,Q(xB) =10 and Q (x B+smin) =3, where the circle is the position of the maximum value obtained by the weighted least square method, x is the measured image index, the left side is a, and the right side is B.
；
；
；
For case 2, d may be set as the normalized distance unit, d A≈2d,dB ≡2d, if the binocular camera A is pre-determined, b corresponds to the right positive direction of the parallax best focus positions x Aest and x Best at the initial positions x A and x B, As shown in fig. 5, the performance difference of the binocular camera A, B is small, i.e., d A≈dB, so x A-xAest=-dA≈-2d,xB-xBest=-dB is approximately equal to-2 d. The binocular cameras A, B use x Aest and x Best as the center origins, the normalized coordinates of the initial positions x A and x B are both-2, The normalized coordinates of the positions x Aest -d and x Best +d after the movement are-1 and +1. According to the above setting, the measurement matrix H and the weight matrix of the binocular camera A, B are W A and W B, the fitting matrices M A and M B are obtained by a weighted least squares method, Substituting the measured data to obtain corresponding parabolic curve coefficients, and finally calculating estimated maximum positions x Amax and x Bmax.
；
；
；
If a binocular camera A is determined in advance, b corresponds to the left negative direction of the parallax best focus positions x Aest and x Best at the initial positions x A and x B, as shown in fig. 6, the binocular camera A, B has a small difference in performance, i.e., d A≈dB, so x A-xAest=dA≈2d,xB-xBest=dB ≡2d. The binocular cameras A, B use x Aest and x Best as the center origins, the normalized coordinates of the initial positions x A and x B are both 2, The normalized coordinates of the positions x Aest -d and x Best +d after the movement are-1 and +1. According to the above setting, the measurement matrix H and the weight matrix of the binocular camera A, B are W A and W B, the fitting matrices M A and M B are obtained by a weighted least squares method, Substituting the measured data to obtain corresponding parabolic curve coefficients, and finally calculating estimated maximum positions x Amax and x Bmax.
；
；；
For case 3, M x/2 may be set as a normalized distance unit, and the predetermined parallax-best focal length positions x Aest and x Best of the binocular cameras a and B are set as origins, as shown in fig. 7, and accordingly, normalized coordinates of the focal length positions x Aest - Mx and x Aest+Mx/2 of the binocular camera a are set to-2 and 1, and normalized coordinates of the focal length positions x Best -Mx/2 and x Best+Mx of the binocular camera B are set to-1 and 2. According to the setting, the measurement matrix H and the weight matrix of the binocular cameras A and B are W A and W B, the fitting matrices M A and M B are obtained by a weighted least squares method, the corresponding parabolic curve coefficients are obtained after substituting the measured data, and finally estimated maximum value positions x Amax and x Bmax are calculated.
；
；；
According to the embodiment of the invention, the visual matching parallax calculation method is effective and simple, and parallax data can be quickly obtained; the weighted least square method can be used for fusing the measurement data of the binocular camera A, B, the measurement frequency is reduced, the focusing speed is improved, the parabolic interpolation method is adopted to approach the extreme point of searching f' (x) =0, and the optimal focusing position of the clear image is quickly found, so that automatic focusing is realized.
Fig. 8 is a schematic diagram of unit modules of an auto-focusing system 200 based on binocular parallax approximate matching according to an embodiment of the present invention, as shown in fig. 8, the system 200 includes:
The image acquisition unit 210 is configured to acquire image data of the binocular camera A, B, where the binocular camera A, B is capable of automatically focusing and optical axes of the binocular camera and the binocular camera are parallel to each other;
The image processing unit 220 is configured to process the image data of the binocular camera A, B respectively, and correspondingly obtain a matrix of the image pixel brightness of the binocular camera A, B;
As shown in fig. 1, both auto-focusing binocular cameras A, B have AGCA, AGCB automatic gain amplifiers and ADCA, ADCB analog-to-digital converters inside, whereby matrices IA (i, j) and IB (i, j) reflecting the brightness of one frame (frame) of image pixels of the A, B camera can be generated. The main function of the AGCA and AGCB automatic gain amplifier is to automatically adjust the brightness of the image pixels according to the illumination condition, so that the brightness of all the pixels after analog-digital conversion is within the range which can be represented by binary system, and the binary system is 8 bits, namely the brightness value is within the range of 0 to 255.
The exclusive-or operation unit 230 is configured to perform exclusive-or operation on the highest bit of each same pixel point in the matrix of the pixel brightness of the binocular camera A, B to obtain a parallax binarization matrix of two frames of images, where i and j are row and column pixel coordinates in the target image area to be focused respectively;
a parallax calculating unit 240, configured to calculate parallax data of a target area to be focused according to the parallax binarization matrix;
The searching unit 250 is configured to obtain an optimal focal length position x Aest、xBest corresponding to the binocular camera A, B according to the parallax data and a parallax-optimal focal length position lookup table that is determined and established in advance;
A comparing unit 260, configured to compare the distance D between the current start focal length position x A、xB of the binocular camera A, B and the corresponding optimal focal length position x Aest、xBest;
And a focusing unit 270, configured to perform automatic focusing by using the binocular camera A, B according to the distance D.
It will be clear to those skilled in the art that, for convenience and brevity of description, specific working procedures of the described modules may refer to corresponding procedures in the foregoing method embodiments, which are not described herein again.
In addition, the embodiment of the invention also provides electronic equipment, which comprises: a processor, memory, system bus; the processor and the memory are connected through the system bus; the memory is used to store one or more programs, which include instructions that, when executed by the processor, cause the processor to perform the auto-focus method 100 described above based on binocular disparity approximation matching.
Further, an embodiment of the present invention provides a computer program product, which when run on a terminal device, causes the terminal device to perform the above-mentioned auto-focus 100 based on binocular disparity approximate matching.
From the above description of embodiments, it will be apparent to those skilled in the art that all or part of the steps of the above described example methods may be implemented in software plus necessary general purpose hardware platforms. Based on such understanding, the technical solution of the present application may be embodied essentially or in a part contributing to the prior art in the form of a software product, which may be stored in a storage medium, such as ROM/RAM, a magnetic disk, an optical disk, etc., including several instructions for causing a computer device (which may be a personal computer, a server, or a network communication device such as a media gateway, etc.) to execute the method described in the embodiments or some parts of the embodiments of the present application.
It should be noted that, in the present description, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different manner from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.
It is further noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (4)
1. The automatic focusing method based on binocular parallax approximate matching is characterized by comprising the following steps of:
image data of a binocular camera A, B is acquired, wherein the binocular camera A, B can automatically focus, and optical axes of the binocular camera and the binocular camera are parallel to each other;
Processing the image data of the binocular camera A, B to obtain a matrix of image pixel brightness corresponding to the binocular camera A, B, including:
the image data of the binocular camera A, B is processed by an automatic gain Amplifier (AGC) and an analog-to-digital converter (ADC) in sequence to obtain processed image data;
According to the processed image data, a matrix I A (I, j) and a matrix I B (I, j) for reflecting the pixel brightness of one frame of image of the binocular camera A, B are established;
The automatic gain amplifier AGC is used for automatically adjusting the brightness of the image pixels according to the illuminance condition; the analog-to-digital converter ADC is used for converting brightness analog signals of all pixels to obtain digital brightness values, and the digital brightness values are represented by binary;
Respectively carrying out differential operation on each row of adjacent elements of the matrixes I A (I, j) and I B (I, j) of the image pixel brightness of the binocular camera A, B to obtain a differential result;
Calculating the absolute value of the difference result, wherein the maximum value of the absolute value in a certain area in the image is an image definition index Q Amax、QBmax of the area;
Wherein, ，；
Performing exclusive OR operation on the highest bit of each same pixel point in the matrix of the pixel brightness of the binocular camera A, B to obtain a parallax binarization matrix of two frames of images, wherein i and j are row and column pixel coordinates in a target image area to be focused respectively;
calculating parallax data of a target area to be focused according to the parallax binarization matrix;
obtaining an optimal focal length position x Aest、xBest corresponding to the binocular camera A, B according to the parallax data and a parallax-optimal focal length position lookup table which is determined and established in advance;
Respectively comparing the distance D between the current initial focal length position x A、xB of the binocular camera A, B and the corresponding optimal focal length position x Aest、xBest;
according to the distance D, the binocular camera A, B performs automatic focusing;
wherein, according to the distance D, the binocular camera A, B performs automatic focusing, including:
Determining a focal length moving mode of the binocular camera A, B according to the distance D;
according to the focal length moving mode, the binocular camera A, B performs automatic focusing;
Wherein, the determining the focal length moving mode of the binocular camera A, B according to the distance D includes:
When (when) And (2) andAt minimum resolution, the binocular camera A, B moves the focal length in the opposite direction by the same small step S min, i.e., A, B moves to x A-Smin and x B+Smin, respectively, and measures the image sharpness index Q, where；
When (when)The focal length of the binocular camera A, B is moved to two sides of the same distance d= (d A+dB)/4 from x Aest and x Best, respectively, that is, the binocular camera A, B is moved to x Aest -d and x Best +d, respectively, and the image definition index Q is measured;
When (when) The focal length of the binocular camera A is moved to x Aest -Mx and x Aest+Mx/2, the focal length of the binocular camera B is moved to x Best -Mx/2 and x Best+Mx, and the image definition index Q is measured;
according to the image definition index Q, further adopting a least square method to calculate and approximate the optimal focal length position;
Wherein when The calculating and approaching the best focus position by a least square method according to the image definition index Q comprises the following steps:
If it is Confirming that the focal length starting position of the binocular camera A, B is near the peak mountain top position, and calculating by adopting a least square method to obtain a more accurate optimal focal length position;
If it is Estimating the best focal length position by a least square method in the negative directions of x Aest and x Best of the peak value;
If it is The peak value is in the positive direction of x Aest and x Best, and the best focal length position is estimated by adopting a least square method;
If it is Then x Aest and x Best are valley point positions, then return and recalculate the parallax data and determine the best focus position x Aest、xBest corresponding to the parallax of the binocular camera A, B;
wherein, according to the image definition index Q, further adopting a least square method to calculate and approximate an optimal focal length position, including:
and (3) approximating the extreme point of the search f' (x) =0 by adopting a parabolic interpolation method, and rapidly finding the optimal focusing position of the clear image.
2. The binocular disparity approximate matching-based auto-focusing method according to claim 1, wherein the disparity-best focus position lookup table is previously determined and established by:
Placing standard images at different distances, and adjusting the focal length of the binocular camera A, B to enable the images to reach a definition index Q Amax、QBmax respectively, and recording the numerical value of the focal length position and the corresponding parallax numerical value at the moment; wherein the corresponding parallax numerical value is calculated according to the parallax binarization matrix;
And establishing a parallax-optimal focal length position lookup table according to the values of the focal length positions recorded on the different distances and the corresponding parallax values.
3. The auto-focusing method based on binocular parallax approximate matching according to claim 2, wherein the performing an exclusive-or operation on the highest bit of each same pixel point in the matrix of the binocular camera A, B image pixel brightness to obtain a parallax binarization matrix of two frames of images comprises:
The brightness value of the image pixel of the binocular camera A, B is expressed by adopting 8-bit binary system;
performing exclusive OR operation on the 8 th bit of each same pixel point in the matrix of the pixel brightness of the binocular camera A, B to obtain a parallax binarization matrix of two frames of images, wherein the calculation formula is as follows:
；
Wherein BW (I, j) is a binarization matrix composed of 0 and 1, MSB [ I A(i,j)]、MSB[IB (I, j) ] represents taking the highest bit of two frames of image pixel points of the binocular camera A, B, the value of BW (I, j) is 0 or 1, and the value of BW (I, j) is exclusive OR logic operation.
4. An auto-focus system based on binocular parallax approximate matching, comprising:
the image acquisition unit is used for acquiring image data of the binocular camera A, B, wherein the binocular camera A, B can automatically focus and optical axes of the binocular camera A, B and the binocular camera are parallel to each other;
the image processing unit is configured to process the image data of the binocular camera A, B respectively, and correspondingly obtain a matrix of image pixel brightness of the binocular camera A, B, and includes:
the image data of the binocular camera A, B is processed by an automatic gain Amplifier (AGC) and an analog-to-digital converter (ADC) in sequence to obtain processed image data;
According to the processed image data, a matrix I A (I, j) and a matrix I B (I, j) for reflecting the pixel brightness of one frame of image of the binocular camera A, B are established;
The automatic gain amplifier AGC is used for automatically adjusting the brightness of the image pixels according to the illuminance condition; the analog-to-digital converter ADC is used for converting brightness analog signals of all pixels to obtain digital brightness values, and the digital brightness values are represented by binary;
Respectively carrying out differential operation on each row of adjacent elements of the matrixes I A (I, j) and I B (I, j) of the image pixel brightness of the binocular camera A, B to obtain a differential result;
Calculating the absolute value of the difference result, wherein the maximum value of the absolute value in a certain area in the image is an image definition index Q Amax、QBmax of the area;
Wherein, ，；
The exclusive-or operation unit is used for carrying out exclusive-or operation on the highest bit of each same pixel point in the matrix of the pixel brightness of the binocular camera A, B to obtain a parallax binarization matrix of two frames of images, wherein i and j are row and column pixel coordinates in a target image area to be focused respectively;
the parallax calculating unit is used for calculating parallax data of the target area to be focused according to the parallax binarization matrix;
The searching unit is used for obtaining an optimal focal length position x Aest、xBest corresponding to the binocular camera A, B according to the parallax data and a parallax-optimal focal length position lookup table which is determined and established in advance;
A comparing unit, configured to compare a distance D between the current start focal length position x A、xB of the binocular camera A, B and the corresponding optimal focal length position x Aest、xBest;
The focusing unit is used for automatically focusing the binocular camera A, B according to the distance D;
wherein, according to the distance D, the binocular camera A, B performs automatic focusing, including:
Determining a focal length moving mode of the binocular camera A, B according to the distance D;
according to the focal length moving mode, the binocular camera A, B performs automatic focusing;
Wherein, the determining the focal length moving mode of the binocular camera A, B according to the distance D includes:
When (when) And (2) andAt minimum resolution, the binocular camera A, B moves the focal length in the opposite direction by the same small step S min, i.e., A, B moves to x A-Smin and x B+Smin, respectively, and measures the image sharpness index Q, where；
When (when)The focal length of the binocular camera A, B is moved to two sides of the same distance d= (d A+dB)/4 from x Aest and x Best, respectively, that is, the binocular camera A, B is moved to x Aest -d and x Best +d, respectively, and the image definition index Q is measured;
When (when) The focal length of the binocular camera A is moved to x Aest -Mx and x Aest+Mx/2, the focal length of the binocular camera B is moved to x Best -Mx/2 and x Best+Mx, and the image definition index Q is measured;
according to the image definition index Q, further adopting a least square method to calculate and approximate the optimal focal length position;
Wherein when The calculating and approaching the best focus position by a least square method according to the image definition index Q comprises the following steps:
If it is Confirming that the focal length starting position of the binocular camera A, B is near the peak mountain top position, and calculating by adopting a least square method to obtain a more accurate optimal focal length position;
If it is Estimating the best focal length position by a least square method in the negative directions of x Aest and x Best of the peak value;
If it is The peak value is in the positive direction of x Aest and x Best, and the best focal length position is estimated by adopting a least square method;
If it is Then x Aest and x Best are valley point positions, then return and recalculate the parallax data and determine the best focus position x Aest、xBest corresponding to the parallax of the binocular camera A, B;
wherein, according to the image definition index Q, further adopting a least square method to calculate and approximate an optimal focal length position, including:
and (3) approximating the extreme point of the search f' (x) =0 by adopting a parabolic interpolation method, and rapidly finding the optimal focusing position of the clear image.
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