CN116193253A - Automatic focusing method, device, medium and equipment - Google Patents

Abstract

The application relates to an automatic focusing method, an automatic focusing device, a medium and equipment, wherein the method is applied to a camera module, and the method comprises the following steps: acquiring image data acquired by the camera module at a plurality of focusing positions; processing the image data based on a preset focusing evaluation function to generate focusing evaluation values corresponding to the focusing positions; and determining a target focusing position from the plurality of focusing positions according to the focusing evaluation values corresponding to the plurality of focusing positions and a preset threshold value, acquiring the focusing evaluation values corresponding to the plurality of focusing positions, and screening the focusing evaluation values corresponding to the plurality of focusing positions according to the preset threshold value, so that the target focusing position is rapidly determined from the plurality of focusing positions, and rapid focusing is realized.

Description

Automatic focusing method, device, medium and equipment

Technical Field

The present application relates to the field of control of image capturing apparatuses, and in particular, to an automatic focusing method, device, medium, and apparatus.

Background

Most of the current methods used in contrast focus (CAF, contrast Auto Focus) are hill-climbing search algorithms: firstly, calculating the magnitude of an evaluation function value at a starting position, then starting a large-step-size driving motor to search, in the searching process, simultaneously comparing the magnitude of the evaluation function value of a front step and a rear step, if the evaluation function value of a currently acquired image is larger than the evaluation function value obtained in the previous step, continuing to move forward, otherwise, moving in the opposite direction, and moving forward, namely, a climbing process and a climbing stage in a graph, wherein when the difference value sign of the searching process changes, and the evaluation function value of the currently acquired image is smaller than the evaluation function value obtained in the previous step, at the moment, the current acquired image is indicated to pass through an extreme point and is in a downhill stage, at the moment, searching in the opposite direction is performed, the searching step is reduced, and the steps are repeated until the step size of the motor is smaller than a set value. In practical application, the focusing position is generally determined after one-time reverse search, and the focusing search speed is accelerated without searching until the motor step length is smaller than the set value.

The hill-climbing searching algorithm has higher accuracy in searching extreme values of the unimodal curves, has higher searching efficiency when processing ideal focusing evaluation functions, but has a relatively slow change of function values and has no obvious extreme value when actually photographing, and is a flat area which is the scene which is commonly known by me.

Disclosure of Invention

In order to solve at least one technical problem in the prior art, an object of the present application is to provide an auto-focusing method, an auto-focusing device, a medium and an apparatus.

The first aspect of the present application provides an auto-focusing method, which is applied to a camera module, and the method includes: acquiring image data acquired by the camera module at a plurality of focusing positions; based on

Processing the image data by a preset focusing evaluation function to generate focusing evaluation values corresponding to the focusing positions 5; based on the focus evaluation values corresponding to the plurality of focus positions and a preset threshold value,

a target focus position is determined from the plurality of focus positions.

Optionally, the determining the target focusing position from the plurality of focusing positions according to the focusing evaluation values corresponding to the plurality of focusing positions and a preset threshold value includes: if the preset threshold is a focusing evaluation

A threshold value of the value, the target focusing evaluation value of the target focusing position is larger than the preset threshold value; or, if the preset threshold is 0, the target focusing position is determined to be the threshold of the difference between the two focusing evaluation values

And the target difference value of the focusing evaluation value between the focusing evaluation value and the adjacent focusing position is larger than the preset threshold value.

Optionally, the preset threshold is a threshold of focus evaluation values, and the target focus is determined from the plurality of focus positions according to the focus evaluation values corresponding to the plurality of focus positions and the preset threshold

The location, comprising: sequentially comparing the 5-magnitude relation between the plurality of focusing evaluation values and the preset threshold along a first direction, wherein the first direction is a direction in which the camera module moves between the plurality of focusing positions

Orientation; determining a plurality of first candidate focusing positions which are continuous in the first direction according to the size relation, wherein the focusing evaluation value of at least one first candidate focusing position in the plurality of first candidate focusing positions is larger than or equal to the preset threshold value; according to focus evaluation corresponding to the plurality of first candidate focus positions

A value determining a focusing position 0 corresponding to an extreme point of focusing evaluation values of the plurality of first candidate focusing positions; and determining the target focusing position as the focusing position corresponding to the extreme point.

Optionally, after the sequentially comparing the magnitude relation of the plurality of focus evaluation values and the preset threshold, the method further includes: determining a plurality of second candidate focusing positions which are continuous in the first direction according to the size relation, wherein the focusing evaluation value of each of the plurality of second candidate focusing positions is smaller than the preset threshold value; amplifying a plurality of focusing evaluation values of the plurality of second candidate focusing positions to obtain a plurality of amplified focusing evaluation values; and determining the target focusing position as the focusing position corresponding to the extreme points of the plurality of amplified focusing evaluation values.

Optionally, the preset threshold is a threshold of a difference between two focus evaluation values, and the determining, according to the focus evaluation values corresponding to the plurality of focus positions and the preset threshold, the target focus position from the plurality of focus positions includes: sequentially acquiring evaluation differences between two adjacent focusing evaluation values in the plurality of focusing evaluation values along a first direction, wherein the first direction is the direction in which the camera module moves between the plurality of focusing positions; determining a plurality of third candidate focusing positions which are continuous in the first direction according to the evaluation difference value between two adjacent focusing evaluation values in the plurality of focusing evaluation values, wherein the evaluation difference value of at least one pair of adjacent third candidate focusing positions in the plurality of third candidate focusing positions is larger than or equal to the preset threshold value; determining focusing positions corresponding to extreme points of focusing evaluation values of the plurality of third candidate focusing positions according to focusing evaluation values corresponding to the plurality of third candidate focusing positions; and determining the target focusing position as the focusing position corresponding to the extreme point.

Optionally, after the sequentially acquiring the evaluation differences between two adjacent focus evaluation values in the plurality of focus evaluation values according to the acquisition order, the method further includes: determining a plurality of fourth candidate focusing positions which are continuous in the first direction according to the evaluation difference value between two adjacent focusing evaluation values in the plurality of focusing evaluation values, wherein the evaluation difference value of each pair of adjacent fourth candidate focusing positions in the plurality of fourth candidate focusing positions is smaller than the preset threshold value; amplifying a plurality of focusing evaluation values of the fourth candidate focusing positions to obtain a plurality of amplified focusing evaluation values; and determining the target focusing position as the focusing position corresponding to the extreme points of the plurality of amplified focusing evaluation values.

Optionally, the plurality of amplified focus evaluation values are obtained by amplifying a plurality of focus evaluation values by a preset multiple, and the preset multiple is positively correlated with the threshold.

A second aspect of the present application provides an autofocus device, comprising: the acquisition module is used for acquiring image data acquired by the camera module at a plurality of focusing positions; the generation module is used for processing the image data based on a preset focusing evaluation function and generating focusing evaluation values corresponding to the focusing positions; and the determining module is used for determining a target focusing position from the focusing positions according to the focusing evaluation values corresponding to the focusing positions and a preset threshold value.

A third aspect of the present application provides a computer readable storage medium having stored thereon a computer program which when executed by a processor performs the steps of the method of any of the first aspects described above.

A fourth aspect of the present application provides an electronic device, including: a memory having a computer program stored thereon; a processor for executing the computer program in the memory to implement the steps of the method of any one of the first aspect

Through the technical scheme, the focusing evaluation values corresponding to the plurality of focusing positions are obtained, and the focusing evaluation values corresponding to the plurality of focusing positions are screened according to the preset threshold, so that the target focusing position is rapidly determined in the plurality of focusing positions, and rapid focusing is realized.

Additional features and advantages of the present application will be set forth in the detailed description which follows.

Drawings

The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate the application and, together with the description, do not limit the application. In the drawings:

FIG. 1 is a flowchart illustrating an implementation of an auto-focus method according to an exemplary embodiment;

FIG. 2 is a flowchart illustrating another implementation of an auto-focus method according to an example embodiment;

FIG. 3 is a schematic diagram of a focus evaluation value distribution curve, according to an example embodiment;

FIG. 4 is a schematic diagram of another focus evaluation value distribution curve, according to an example embodiment;

FIG. 5 is a flowchart illustrating yet another implementation of an auto-focus method according to an example embodiment;

FIG. 6 is a schematic block diagram of an auto-focus system shown according to an exemplary embodiment;

fig. 7 is a schematic block diagram of an electronic device, shown in accordance with an exemplary embodiment.

Detailed Description

The following detailed description of specific embodiments of the present application refers to the accompanying drawings. It should be understood that the detailed description is presented herein for purposes of illustration and explanation only and is not intended to limit the present application.

It should be noted that, all actions for acquiring signals, information or data in the present application are performed under the condition of conforming to the corresponding data protection rule policy of the country of the location and obtaining the authorization given by the owner of the corresponding device.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of the present application only and is not intended to be limiting of the present application.

In the following description, reference is made to "some embodiments" which describe a subset of all possible embodiments, but it is to be understood that "some embodiments" can be the same subset or different subsets of all possible embodiments and can be combined with one another without conflict.

It should be noted that the term "first/second/third" in reference to the embodiments of the present application is used to distinguish similar or different objects, and does not represent a specific ordering of the objects, it being understood that the "first/second/third" may be interchanged with a specific order or sequence, as permitted, to enable the embodiments of the present application described herein to be implemented in an order other than that illustrated or described herein.

Before further describing embodiments of the present application in detail, the terms and expressions that are referred to in the embodiments of the present application are described, and are suitable for the following explanation.

In photography, the term focus refers to the process of adjusting the lens to find the maximum resolution, sharpness, and contrast of a selected subject. The manual or automatic focusing system uses the lens of the camera to make the photographed object look as detailed as possible and have a high contrast. There are many technical focus definitions in photography, which in short can be defined to find the best sharpness for a given subject. This may be performed using manual focusing or an autofocus system of the camera.

Contrast type focusing, also called contrast detection focusing, is an automatic focusing method. Contrast focus relies on implementation of a photosensitive element and an image processor, and this focusing mode is only started in the digital camera era, and one of the preconditions for its implementation is to have the photosensitive element and to be able to view in real time. The principle can be expressed as: after the surface of the object is irradiated by light, red light reflected by the object is converged at a certain point before reaching the sensor through the convex lens group, then the scattered light is distributed in a larger area of the photosensitive element, imaging pixels around the larger area are low in contrast ratio. The contrast of the whole image is very low at this time. According to the principle, the contrast ratio is lower in the defocusing state, the position of the focusing point is changed, the contrast ratio of the curve is inclined, but the algorithm cannot judge when the curve is the highest point, only the numerical value in the process can be recorded, only after the focusing point is passed, the curve is lowered and then moves back, and a larger local gradient value can be obtained after repeated movement, so that the focusing is considered to be successful.

Most of contrast type focusing is currently performed by a hill-climbing searching algorithm, and in the extremum searching of a unimodal curve, the hill-climbing searching algorithm has higher accuracy, but in actual photographing, the scene is a so-called flat area, which has relatively slow change of function values and has no obvious extremum.

In view of this, the embodiments of the present application provide an automatic focusing method, which obtains focus evaluation values corresponding to a plurality of focus positions, and screens the focus evaluation values corresponding to the plurality of focus positions according to a preset threshold, so that a target focus position is quickly determined in the plurality of focus positions, and quick focusing is realized.

The method is applied to the electronic equipment comprising the photographic assembly, wherein the electronic equipment can be a personal computer, a notebook computer, a palm computer or a server and the like comprising a photographic function; the electronic device may also be a mobile terminal with a camera function, for example, the mobile terminal may include a digital camera, a mobile phone, a vehicle-mounted computer, a tablet computer, a projector, or the like.

The photographing assembly includes an imaging optical system such as an imaging lens and an aperture, and an imaging element of a CCD type or a CMOS type or the like that photographs an object through the photographing optical system. An imaging optical system including an imaging lens and an aperture is detachable from or fixed to a camera body. The imaging lens includes a focusing lens movable in the optical axis direction.

The focus lens is a lens that adjusts the focus position of the imaging optical system by moving in the optical axis direction. The imaging lens is composed of a plurality of lens groups, and when the lens is a lens with a telescopic whole group, the whole group is a focusing lens.

A processor in the electronic device controls the lens driving section to move a focusing lens included in the imaging lens. The processor may also control the aperture amount of the diaphragm via the diaphragm driving unit, thereby adjusting the exposure amount.

The electronic device further includes an analog signal processing unit which is connected to the output of the imaging element and performs analog signal processing such as correlated double sampling processing; and an analog-to-digital conversion circuit (A/D) for converting the analog signal outputted from the analog signal processing unit into a digital signal. The analog signal processing unit and the analog-to-digital conversion circuit are controlled by the system control unit. The analog signal processing section and the analog-to-digital conversion circuit are sometimes built in the imaging element.

Fig. 1 is a schematic flowchart of an implementation of an auto-focusing method according to an embodiment of the present application, as shown in fig. 1, the method may include the following steps 110 to 130:

s110, acquiring image data acquired by the camera module at a plurality of focusing positions.

The camera module collects images at a plurality of focusing positions to obtain a plurality of different image data.

For example, the camera focusing system controls the lens driving section to move the focus lens included in the photographing assembly, and at each position where the focus lens is moved, the object is photographed with the imaging element, thereby obtaining a plurality of images.

In some embodiments of the present application, the camera module includes a plurality of focus points, which are visual representations of the in-focus content of the camera. Usually in the form of empty squares or dots on the viewfinder or LCD screen of the camera.

In a scene using autofocus, the focus is changed in a step-wise manner, at least one, and typically three, focus points are used in the step-wise manner, and images are acquired at each moved focus point, and the images acquired at each focus point are digitized to obtain a plurality of images.

S120, processing the image data based on a preset focusing evaluation function, and generating focusing evaluation values corresponding to the focusing positions.

For each image data, a preprocessing algorithm such as a Brenner gradient function, a Laplacian gradient function, a variance function, an EAV point sharpness algorithm function and the like is used for calculating the point with the highest image definition, calculating the contrast value of the image, and calculating the contrast value by using a preset evaluation value function after obtaining the contrast value to obtain the evaluation value of each image data.

And taking the evaluation value of each image data as the focusing evaluation value of the corresponding focusing position, thereby obtaining focusing evaluation values corresponding to a plurality of focusing positions.

S130, determining a target focusing position from the focusing positions according to focusing evaluation values corresponding to the focusing positions and a preset threshold value.

And screening the focusing evaluation value by using a preset threshold value, and avoiding a flat area in the focusing evaluation value, so that the target focusing position is rapidly determined from a plurality of focusing positions.

In the embodiment of the application, the focusing evaluation values corresponding to the plurality of focusing positions are obtained, and the focusing evaluation values corresponding to the plurality of focusing positions are screened according to the preset threshold, so that the target focusing position is rapidly determined in the plurality of focusing positions, and rapid focusing is realized.

Optionally, if the preset threshold is a threshold of the focusing evaluation value, the target focusing evaluation value of the target focusing position is greater than the preset threshold; or if the preset threshold is a threshold of a difference value between two focusing evaluation values, the target difference value of the focusing evaluation values between the target focusing position and the adjacent focusing position is larger than the preset threshold.

In one embodiment of the present application, the preset threshold is a threshold set for a focus evaluation value, and the target focus evaluation value is greater than the preset threshold.

As shown in fig. 2, fig. 2 is a schematic implementation flow chart of determining a target focusing position according to a preset threshold, where determining the target focusing position from the plurality of focusing positions according to focusing evaluation values corresponding to the plurality of focusing positions and the preset threshold includes:

s210, comparing the magnitude relation between the plurality of focusing evaluation values and the preset threshold value sequentially along a first direction, wherein the first direction is the direction in which the image pickup module moves among the plurality of focusing positions.

In the auto-focusing process, the camera focusing system searches along a certain direction to find an optimal focusing position, for example, the camera focusing system changes the focusing point of the photographing assembly along the direction of the axis of the photographed body to obtain image data and an evaluation value for searching. The direction of the search may be determined in other manners, such as being generated by a preset search direction determining algorithm.

And in the searching process, sequencing the moved focusing positions along the acquisition sequence of the image data, sequentially comparing the focusing evaluation values of the focusing positions with a preset threshold value in the sequence, and searching the maximum value of the focusing evaluation values in the comparing process. If there are 100 focusing positions in total, the focusing lens is moved in a certain step length along the searching direction (namely, the first direction) currently designated by the direction determining algorithm, so that the photographing assembly acquires a plurality of images. In some embodiments, the step size is not a fixed value, which may be different in each movement.

S220, determining a plurality of first candidate focusing positions which are continuous in the first direction according to the size relation, wherein the focusing evaluation value of at least one first candidate focusing position in the plurality of first candidate focusing positions is larger than or equal to the preset threshold value.

S230, determining focusing positions corresponding to extreme points of focusing evaluation values of the first candidate focusing positions according to the focusing evaluation values corresponding to the first candidate focusing positions.

In some examples, the search process described above is an iterative process, where a number of consecutive focus positions are selected along the ordering of focus positions (i.e., in the first direction) in each sub-iteration, and one or more determinations are made. And when the continuous focusing positions meet the conditions, the continuous focusing positions are used as first candidate focusing positions, and after the iteration judgment is repeatedly judged, a plurality of first candidate focusing positions are obtained. And performing a plurality of iterations until an extreme point of the focusing evaluation value of the first candidate focusing position is found, ending the iterations, and determining the focusing position corresponding to the extreme point.

For example, 10 positions are moved each time, a continuous value is judged in iteration and is set to be 5, first iterative search is carried out to obtain focusing evaluation values of 10 focusing positions, 5 continuous focusing positions are sequentially obtained from the focusing evaluation values according to the sequence of image acquisition, the focusing evaluation values of 5 continuous focusing positions are compared with a preset threshold, and when the focusing evaluation value of at least one focusing position is larger than or equal to the preset threshold, the condition is met, and the five continuous focusing positions are used as first candidate focusing positions. And sequentially acquiring the rest 5 continuous focusing positions according to the image acquisition sequence, comparing and judging whether the condition is met, and if the condition is met, taking the rest 5 continuous focusing positions as first candidate focusing positions. The first candidate focusing positions obtained through the judgment are continuous according to the image acquisition sequence, and the focusing evaluation value of at least one first candidate focusing position is larger than or equal to the preset threshold value, and the first candidate focusing positions are correspondingly marked as candidate focusing positions 1 to 10 respectively.

After judging 10 candidate focusing positions of the iteration, searching the candidate focusing positions, for example, comparing the differences of the focusing evaluation values corresponding to the front and rear adjacent candidate focusing positions in a progressive manner along the sequence of the focusing positions, for example, comparing the focusing evaluation values of the position 1 and the position 2, wherein the differences are smaller than zero, indicating that the latter focusing position has higher contrast, the focusing evaluation values are still rising, continuing progressive searching, comparing the focusing evaluation values of the position 2 and the position 3, judging the differences and the rising trend until the progressive position 10 is the rising trend or no continuous number such as 3 trend is reduced, and indicating that the maximum value of the focusing evaluation values is not in the iteration.

And continuously executing the next iteration, sequentially moving 10 focusing positions, acquiring a specified number (5) of continuous focusing positions from the image data along the acquisition sequence of the image data, comparing the size relation between the specified number of continuous focusing positions and a preset threshold, and taking the five continuous focusing positions as first candidate focusing positions when the focusing evaluation value of at least one focusing position in the continuous number of focusing positions is greater than or equal to the preset threshold to obtain first candidate positions 10 to 15. And sequentially acquiring the rest 5 continuous focusing positions according to the image acquisition sequence, comparing and judging whether the condition is met, and taking the condition as a first candidate focusing position if the condition is met. And finishing the comparison of the second iteration, and continuing to sort according to the image acquisition sequence on the basis of the first iteration to obtain the first candidate focusing position 16 to the first candidate focusing position 20.

And then progressively comparing the difference values of the focusing evaluation values corresponding to the front and rear adjacent candidate focusing positions, judging the difference values and the ascending trend until the ending condition is met, and continuing iteration if the ending condition is not met, wherein the ending condition is as follows: the descending position is inquired, the inquiry method for the descending position can be that the continuous number of the descending positions, such as 3 differences, are larger than zero, the trend of focusing evaluation values of the continuous 3 positions is descending, the descending position is taken as the descending position, and the forward iteration is ended.

The descending position is used as a position for reverse search, and reverse iteration is started, and is similar to forward iteration, except that the search direction is the reverse direction of the first reverse direction. And executing reverse iteration until an end condition is met, and continuing iteration if the end condition is not met, wherein the end condition is as follows: the descent position is queried.

The descent position of the reverse search may be regarded as the position of the maximum value.

Alternatively, similar to the above procedure, forward and reverse searches are performed a specified number of times, such as performing a forward search, a backward search, and a backward search again, with the position of the descent of the last backward search as the position of the maximum value.

S240, determining the target focusing position as the focusing position corresponding to the extreme point.

The maximum value of the focus evaluation value indicates that the maximum contrast value is to be obtained in the focus, and therefore the position is taken as the final target focus position.

In the above embodiment, the distribution of the focusing evaluation values is in a unimodal curve in the case that the preset threshold is satisfied, that is, the camera focusing system does not enter a flat area during the search.

However, in the case that the threshold is not satisfied, that is, the image to be photographed has a flat area, and the distribution of the focus evaluation values is a multimodal curve, the multimodal values refer to a tendency that there are a plurality of rising and falling trends in the focus evaluation values, as shown in fig. 3, by way of example, fig. 3 is a schematic diagram of a focus evaluation value distribution curve shown in the application, in fig. 3, the focus evaluation value at the position 2 is greater than the position 1 and the position 3, and the position 5 is greater than the position 4 and the position 6, and at this time, the distribution curve of the focus evaluation values has two peaks, and a flat area exists. The search for the camera is slow in this region and it is difficult to find an extremum.

The camera focusing system gradually changes the focusing point of the shooting assembly in a first direction determined by a searching direction determining algorithm in a certain step length, and each step of movement is carried out to obtain the focusing position image data and the evaluation value.

During the searching process, the focusing positions are ordered along the acquisition sequence of the image data, and the focusing evaluation values of the focusing positions are sequentially compared with the preset threshold value in the sequence.

S221, determining a plurality of second candidate focusing positions which are continuous in the first direction according to the size relation, wherein the focusing evaluation value of each of the plurality of second candidate focusing positions is smaller than the preset threshold value.

S222, amplifying the plurality of focusing evaluation values corresponding to the plurality of second candidate focusing positions to obtain a plurality of amplified focusing evaluation values.

The search process is an iterative process that will be performed between a plurality of successive focus positions in each sub-iteration. And when the continuous focusing positions do not meet the threshold condition, taking the continuous focusing positions as second candidate focusing positions, repeating a plurality of iterations to obtain a plurality of second candidate focusing positions until the extreme point of the focusing evaluation value of the second candidate focusing positions is found, ending the iterations, and determining the focusing positions corresponding to the extreme points.

For example, 10 focusing positions are moved for each iteration, a continuous value in the iteration is set to be 5, first iteration search is performed to obtain focusing evaluation values of the 10 focusing positions, 5 focusing positions are sequentially obtained from the 10 focusing positions in the iteration, the focusing evaluation values of the 5 focusing positions are compared with a preset threshold, and when the focusing evaluation value of each focusing position is smaller than the preset threshold, the condition is met, and the five continuous focusing positions are used as second candidate focusing positions. And marking the focusing positions as second candidate focusing positions 1 to 5 respectively according to the image acquisition sequence.

Sequentially acquiring the rest 5 continuous focusing positions according to the image acquisition sequence, and comparing and judging whether the condition is met: and when the focusing evaluation value of each focusing position is smaller than a preset threshold value, if the condition is met, the focusing evaluation value of each focusing position is used as a second candidate focusing position, the second candidate focusing positions obtained through the judgment are continuous in the image acquisition sequence, and the focusing evaluation value of each first candidate focusing position is smaller than the preset threshold value, and the second candidate focusing positions are correspondingly marked as candidate focusing positions 6 to 10 respectively.

And after the second candidate focusing position of the iteration is obtained, amplifying the corresponding focusing evaluation value.

Optionally, the plurality of amplified focus evaluation values are obtained by amplifying a plurality of focus evaluation values by a preset multiple, and the preset multiple is positively correlated with the threshold.

The amplification factor should be determined according to the ideal minimum difference value, and the application considers that in a flat area, the difference of the evaluation function values obtained by searching is not large, the curve extremum position is difficult to find quickly, and the problems of defocus, virtual focus, lens repeated stretching, focus searching and the like are presented in the actual focusing process. Therefore, the difference between the peak points can be amplified by amplifying the focus evaluation value, so that the determination condition can be satisfied, which corresponds to converting the multimodal curve into a unimodal curve. By way of example, the present application considers that the difference in focus evaluation values of the front-rear adjacent positions should be in the range of 200 to 1000, and predicts that the minimum difference is likely to be 100, and sets the magnification to be between 2 and 8.

The difference of the focus evaluation values of the adjacent focus positions can be enlarged by setting the magnification, thereby accelerating the search of the maximum value. As shown in fig. 4, fig. 4 is a schematic diagram of another focusing evaluation value distribution curve shown in the present application, and the focusing evaluation value in fig. 3 is enlarged three times to obtain fig. 4, and the difference value of the focusing evaluation values is increased in fig. 4 due to the enlargement of the focusing evaluation value, so that the multi-peak curve is converted into the single-peak curve.

Searching in the amplified focusing evaluation values, for example, progressively comparing the differences of the focusing evaluation values corresponding to the front and back adjacent candidate focusing positions along the sequence of the focusing positions, for example, comparing the focusing evaluation values of the position 1 and the position 2, wherein the differences are smaller than zero, which indicates that the latter focusing position has higher contrast, the focusing evaluation values are further progressively increased, comparing the focusing evaluation values of the position 2 and the position 3, judging the differences and the ascending trend until the focusing evaluation values are progressively increased until the focusing evaluation values are submitted to the position 10 or no continuous number such as 3 trends are reduced, and indicating that the maximum value of the focusing evaluation values is not in the iteration.

And continuing the second iteration of forward search, sequentially moving 10 focusing positions to obtain 5 focusing positions, comparing the focusing evaluation values of the 5 focusing positions with a preset threshold, and taking the five continuous focusing positions as second candidate focusing positions when the focusing evaluation value of each focusing position is smaller than the preset threshold. And on the basis of the second iteration, continuing to sort according to the image acquisition sequence to obtain second candidate focusing positions 11 to 15, sequentially acquiring the rest 5 continuous focusing positions according to the image acquisition sequence, comparing and judging whether the condition is met, taking the second candidate focusing positions as the second candidate focusing positions, and correspondingly marking the second candidate focusing positions as candidate focusing positions 16 to 20 respectively.

After the judgment is completed, amplifying focusing evaluation values of 10 second candidate focusing positions (second candidate focusing positions 11 to 20) of the iteration by using amplification factors, progressively comparing differences of focusing evaluation values corresponding to the candidate focusing positions which are adjacent before and after, judging the differences and the ascending trend until an ending condition is met, and continuing the iteration if the ending condition is not met, wherein the ending condition is that: the descending position is inquired, the inquiry method for the descending position can be that the continuous number of the descending positions, such as 3 differences, are larger than zero, the trend of focusing evaluation values of the continuous 3 positions is descending, the descending position is taken as the descending position, and the forward iteration is ended.

The descending position is used as a position for reverse search, and reverse iteration is started, and is similar to forward iteration, except that the search direction is the reverse direction of the first reverse direction. And executing reverse iteration until an end condition is met, and continuing iteration if the end condition is not met, wherein the end condition is as follows: the descent position is queried.

The descent position of the reverse search may be regarded as the position of the maximum value.

Alternatively, similar to the above procedure, forward and reverse searches are performed a specified number of times, such as performing a forward search and a backward search again, with the position of the descent of the last backward search as the position of the maximum value.

S223, determining the target focusing position as the focusing position corresponding to the extreme points of the plurality of amplified focusing evaluation values.

The maximum value of the focus evaluation value indicates that the maximum contrast value is to be obtained in the focus, and therefore the position is taken as the final target focus position.

In one embodiment of the present application, the preset threshold is a threshold of a difference between two focus evaluation values.

As shown in fig. 5, fig. 5 is a schematic diagram of another implementation flow chart for determining a target focusing position according to a preset threshold, where determining the target focusing position from the plurality of focusing positions according to the focusing evaluation values corresponding to the plurality of focusing positions and the preset threshold includes:

s510, sequentially acquiring evaluation difference values between two adjacent focusing evaluation values in the plurality of focusing evaluation values along a first direction, wherein the first direction is a direction in which the image pickup module moves among the plurality of focusing positions.

The camera focusing system gradually changes the focusing point of the shooting assembly in a first direction determined by a searching direction determining algorithm in a certain step length, and each step of movement is carried out to obtain the focusing position image data and the evaluation value.

The search process is an iterative process, in which each sub-iteration of the search process: the plurality of positions are moved, and the comparison of the threshold values and the search of the maximum value are continuously performed between the plurality of focusing positions.

And repeating the iteration to obtain a plurality of second candidate focusing positions until the extreme point of the focusing evaluation value of the second candidate focusing position is found, ending the iteration, and determining the focusing position corresponding to the extreme point.

During the searching process, the focusing positions are ordered along the acquisition sequence of the image data, and the difference value of the focusing evaluation values of the front focusing position and the rear focusing position is calculated sequentially on the order. For example, the continuous value in one iteration is set to be 5, forward search is performed for the first iteration, 10 focusing positions are moved, 5 continuous focusing positions are sequentially acquired along the acquisition sequence of the image data, the difference value of the focusing evaluation value of each two adjacent focusing positions is sequentially calculated, for example, the difference value of the position 1 and the position 2 is calculated, the difference value between the positions 2 and 3 is calculated, the difference value between the positions 3 and 4 is calculated, and the difference value between the positions 4 and 5 is calculated.

S520, determining a plurality of third candidate focusing positions which are continuous in the first direction according to the evaluation difference value between two adjacent focusing evaluation values in the plurality of focusing evaluation values, wherein at least one pair of adjacent third candidate focusing positions in the plurality of third candidate focusing positions is larger than or equal to the preset threshold value.

S530, determining the focusing positions corresponding to extreme points of the focusing evaluation values of the third candidate focusing positions according to the focusing evaluation values corresponding to the third candidate focusing positions.

In the continuous focusing position, the difference value is compared with a preset threshold value. And comparing the magnitude relation between the difference value and a preset threshold value for the difference value of every two adjacent focusing positions, and when at least one pair of adjacent focusing positions in the obtained 5 focusing positions is larger than or equal to the preset threshold value, setting the 5 continuous focusing positions as third candidate focusing positions.

Sequentially acquiring the rest 5 continuous focusing positions according to the image acquisition sequence, and comparing and judging whether the condition is met: and if the condition is met, the third candidate focusing positions are used as the third candidate focusing positions, the third candidate focusing positions obtained through the judgment are continuous in the image acquisition sequence, the focusing evaluation value of each first candidate focusing position is smaller than the preset threshold, and the third candidate focusing positions are correspondingly marked as candidate focusing positions 1 to 10 respectively.

Searching in the focusing evaluation values corresponding to the third candidate focusing position, for example, comparing the difference values of the focusing evaluation values corresponding to the front and back adjacent candidate focusing positions in a progressive manner along the sequence of the focusing positions, for example, comparing the focusing evaluation values of the position 1 and the position 2, wherein the difference value is smaller than zero, indicating that the latter focusing position has higher contrast, the focusing evaluation values are still rising, continuing to progressive, comparing the focusing evaluation values of the position 2 and the position 3, judging the difference value and the rising trend until the focusing evaluation values are submitted to the position 5 and are in the rising trend or the trend that no continuous number such as 3 is present is reduced, and indicating that the maximum value of the focusing evaluation values is not in the iteration.

And continuing iteration, sequentially moving 10 focusing positions, acquiring 5 continuous focusing positions according to the image acquisition sequence, comparing the focusing evaluation values of the 5 focusing positions with a preset threshold, and taking the five continuous focusing positions as third candidate focusing positions when the focusing evaluation value of at least one focusing position is larger than or equal to the preset threshold. On the basis of the second iteration, continuing to sort according to the image acquisition sequence to obtain third candidate focusing positions 11 to 15, sequentially acquiring the rest 5 continuous focusing positions according to the image acquisition sequence, and comparing and judging whether the conditions are met: when the focusing evaluation value of each focusing position is smaller than the preset threshold value, if the condition is not met, the focusing evaluation value of each focusing position is not used as a third candidate focusing position.

Amplifying the focusing evaluation values of the 5 third candidate focusing positions (the second candidate focusing positions 6 to 10) of the iteration by using amplification factors, progressively comparing the difference values of the focusing evaluation values corresponding to the adjacent candidate focusing positions, judging the difference values and the ascending trend until the ending condition is met, and continuing the iteration if the ending condition is not met, wherein the ending condition is that: the descending position is inquired, the inquiry method for the descending position can be that the continuous number of the descending positions, such as 3 differences, are larger than zero, the trend of focusing evaluation values of the continuous 3 positions is descending, the descending position is taken as the descending position, and the forward iteration is ended.

The descending position is used as a position for reverse search, and reverse iteration is started, and is similar to forward iteration, except that the search direction is the reverse direction of the first reverse direction. And executing reverse iteration until an end condition is met, and continuing iteration if the end condition is not met, wherein the end condition is as follows: the descent position is queried.

The descent position of the reverse search may be regarded as the position of the maximum value.

Alternatively, similar to the above procedure, forward and reverse searches are performed a specified number of times, such as performing a forward search, a backward search, and a backward search again, with the position of the descent of the last backward search as the position of the maximum value.

S540, determining the target focusing position as the focusing position corresponding to the extreme point.

The maximum value of the focus evaluation value indicates that the maximum contrast value is to be obtained in the focus, and therefore the position is taken as the final target focus position.

In the case that there is a flat area for an image to be photographed, and the distribution of the focus evaluation values thereof is a multimodal curve, it will not satisfy a preset threshold:

the camera focusing system gradually changes the focusing point of the shooting assembly in a first direction determined by a searching direction determining algorithm in a certain step length, and each step of movement is carried out to obtain the focusing position image data and the evaluation value.

In the searching process, the focusing positions are ordered along the acquisition sequence of the image data, a continuous number of focusing position points such as 5 focusing position points are obtained, the difference value of the focusing evaluation values of the adjacent focusing positions is calculated sequentially along the acquisition sequence, and the difference value is compared with a preset threshold value.

S521, determining a plurality of fourth candidate focusing positions which are continuous in the first direction according to the evaluation difference value between two adjacent focusing evaluation values in the plurality of focusing evaluation values, wherein the evaluation difference value of each pair of adjacent fourth candidate focusing positions in the plurality of fourth candidate focusing positions is smaller than the preset threshold value.

And S522, amplifying the plurality of focusing evaluation values corresponding to the plurality of fourth candidate focusing positions to obtain a plurality of amplified focusing evaluation values.

In the above-mentioned continuous focusing positions, for the difference value of every two adjacent focusing positions, the magnitude relation of the difference value and the preset threshold value is compared. And when each pair of adjacent focusing positions in the obtained 5 focusing positions is smaller than the preset threshold value, taking the 5 continuous focusing positions as fourth candidate focusing positions.

And after the fourth candidate focusing position of the iteration is obtained, amplifying the corresponding focusing evaluation value.

Optionally, the plurality of amplified focus evaluation values are obtained by amplifying a plurality of focus evaluation values by a preset multiple, and the preset multiple is positively correlated with the threshold.

The amplification factor should be determined according to the ideal minimum difference value, and the application considers that in a flat area, the difference of the evaluation function values obtained by searching is not large, the curve extremum position is difficult to find quickly, and the problems of defocus, virtual focus, lens repeated stretching, focus searching and the like are presented in the actual focusing process. Therefore, the difference between the peak points can be amplified by amplifying the focus evaluation value, so that the determination condition can be satisfied, which corresponds to converting the multimodal curve into a unimodal curve. By way of example, the present application considers that the difference in focus evaluation values of the front-rear adjacent positions should be in the range of 200 to 1000, and predicts that the minimum difference is likely to be 100, and sets the magnification to be between 2 and 8.

The difference of the focus evaluation values of the adjacent focus positions can be enlarged by setting the magnification, thereby accelerating the search of the maximum value.

Searching in the amplified focusing evaluation values, for example, comparing the differences of the focusing evaluation values corresponding to the candidate focusing positions adjacent to each other in sequence along the focusing positions, for example, comparing the focusing evaluation values of the position 1 and the position 2, wherein the differences are smaller than zero, which indicates that the latter focusing position has higher contrast, the focusing evaluation values are still ascending, continuing to advance, comparing the focusing evaluation values of the position 2 and the position 3, judging the differences and the ascending trend until the focusing evaluation values are submitted to the position 5 or the ascending trend is not presented, or no continuous number such as 3 trends are presented, which indicates that the maximum value of the focusing evaluation values is not in the iteration.

And continuing iteration, moving 5 focusing positions, sequentially acquiring 5 continuous focusing positions along the image acquisition sequence, and comparing the magnitude relation between the difference value of every two adjacent focusing positions and a preset threshold value. And when each pair of adjacent focusing positions in the obtained 5 focusing positions is smaller than the preset threshold value, taking the five continuous focusing positions as fourth candidate focusing positions. On the basis of the first iteration, continuing to sort according to the image acquisition sequence to obtain second candidate focusing positions 6 to 10, amplifying focusing evaluation values of 5 second candidate focusing positions (the second candidate focusing positions 6 to 10) of the iteration by using amplification factors, progressively comparing differences of focusing evaluation values corresponding to the adjacent candidate focusing positions, judging the differences and the rising trend until an ending condition is met, continuing iteration if the ending condition is not met, wherein the ending condition is that: the descending position is inquired, the inquiry method for the descending position can be that the continuous number of the descending positions, such as 3 differences, are larger than zero, the trend of focusing evaluation values of the continuous 3 positions is descending, the descending position is taken as the descending position, and the forward iteration is ended.

The descending position is used as a position for reverse search, and reverse iteration is started, and is similar to forward iteration, except that the search direction is the reverse direction of the first reverse direction. And executing reverse iteration until an end condition is met, and continuing iteration if the end condition is not met, wherein the end condition is as follows: the descent position is queried.

The descent position of the reverse search may be regarded as the position of the maximum value.

Alternatively, similar to the above procedure, forward and reverse searches are performed a specified number of times, such as performing a forward search, a backward search, and a backward search again, with the position of the descent of the last backward search as the position of the maximum value.

S523, determining the target focusing position as the focusing position corresponding to the extreme points of the plurality of amplified focusing evaluation values.

The maximum value of the focus evaluation value indicates that the maximum contrast value is to be obtained in the focus, and therefore the position is taken as the final target focus position.

Fig. 6 is a schematic structural diagram of an autofocus device according to an embodiment of the present application, as shown in fig. 6, the device 600 includes an obtaining module 610, a generating module 620, and a determining module 630, where:

the acquisition module is used for acquiring image data acquired by the camera module at a plurality of focusing positions;

The generation module is used for processing the image data based on a preset focusing evaluation function and generating focusing evaluation values corresponding to the focusing positions;

and the determining module is used for determining a target focusing position from the focusing positions according to the focusing evaluation values corresponding to the focusing positions and a preset threshold value.

The specific manner in which the various modules perform the operations in the apparatus of the above embodiments have been described in detail in connection with the embodiments of the method, and will not be described in detail herein.

Fig. 7 is a block diagram of an electronic device 700, according to an example embodiment. As shown in fig. 7, the electronic device 700 may include: a processor 701, a memory 702. The electronic device 700 may also include one or more of a multimedia component 703, an input/output (I/O) interface 704, and a communication component 705.

The processor 701 is configured to control the overall operation of the electronic device 700 to perform all or part of the steps in the auto-focusing method described above. The memory 702 is used to store various types of data to support operation on the electronic device 700, which may include, for example, instructions for any application or method operating on the electronic device 700, as well as application-related data, such as contact data, messages sent and received, pictures, audio, video, and so forth. The Memory 702 may be implemented by any type or combination of volatile or non-volatile Memory devices, such as static random access Memory (Static Random Access Memory, SRAM for short), electrically erasable programmable Read-Only Memory (Electrically Erasable Programmable Read-Only Memory, EEPROM for short), erasable programmable Read-Only Memory (Erasable Programmable Read-Only Memory, EPROM for short), programmable Read-Only Memory (Programmable Read-Only Memory, PROM for short), read-Only Memory (ROM for short), magnetic Memory, flash Memory, magnetic disk, or optical disk. The multimedia component 703 can include a screen and an audio component. Wherein the screen may be, for example, a touch screen, the audio component being for outputting and/or inputting audio signals. For example, the audio component may include a microphone for receiving external audio signals. The received audio signals may be further stored in the memory 702 or transmitted through the communication component 705. The audio assembly further comprises at least one speaker for outputting audio signals. The I/O interface 704 provides an interface between the processor 701 and other interface modules, which may be a keyboard, mouse, buttons, etc. These buttons may be virtual buttons or physical buttons. The communication component 705 is for wired or wireless communication between the electronic device 700 and other devices. Wireless communication, such as Wi-Fi, bluetooth, near field communication (Near Field Communication, NFC for short), 2G, 3G, 4G, NB-IOT, eMTC, or other 5G, etc., or one or a combination of more of them, is not limited herein. The corresponding communication component 705 may thus comprise: wi-Fi module, bluetooth module, NFC module, etc.

In an exemplary embodiment, the electronic device 700 may be implemented by one or more application specific integrated circuits (Application Specific Integrated Circuit, abbreviated ASIC), digital signal processor (Digital Signal Processor, abbreviated DSP), digital signal processing device (Digital Signal Processing Device, abbreviated DSPD), programmable logic device (Programmable Logic Device, abbreviated PLD), field programmable gate array (Field Programmable Gate Array, abbreviated FPGA), controller, microcontroller, microprocessor, or other electronic components for performing the auto-focus method described above.

In another exemplary embodiment, a computer readable storage medium is also provided, comprising program instructions which, when executed by a processor, implement the steps of the auto-focus method described above. For example, the computer readable storage medium may be the memory 702 including program instructions described above, which are executable by the processor 701 of the electronic device 700 to perform the auto-focusing method described above.

In another exemplary embodiment, a computer program product is also provided, comprising a computer program executable by a programmable apparatus, the computer program having code portions for performing the above-described auto-focus method when executed by the programmable apparatus.

The preferred embodiments of the present application have been described in detail above with reference to the accompanying drawings, but the present application is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solutions of the present application within the scope of the technical concept of the present application, and all the simple modifications belong to the protection scope of the present application.

In addition, the specific features described in the foregoing embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, various possible combinations are not described in detail.

Moreover, any combination of the various embodiments of the present application may be made without departing from the spirit of the present application, which should also be considered as disclosed herein.

Claims (10)

1. An automatic focusing method, which is applied to an image pickup module, the method comprising:

acquiring image data acquired by the camera module at a plurality of focusing positions;

processing the image data based on a preset focusing evaluation function to generate focusing evaluation values corresponding to the focusing positions;

And determining a target focusing position from the plurality of focusing positions according to the focusing evaluation values corresponding to the plurality of focusing positions and a preset threshold value.

2. The method of claim 1, wherein the determining the target focus position from the plurality of focus positions according to the focus evaluation values corresponding to the plurality of focus positions and a preset threshold value comprises:

if the preset threshold is a threshold of the focusing evaluation value, the target focusing evaluation value of the target focusing position is larger than the preset threshold; or alternatively, the first and second heat exchangers may be,

and if the preset threshold is a threshold of the difference value between the two focusing evaluation values, the target difference value of the focusing evaluation values between the target focusing position and the adjacent focusing position is larger than the preset threshold.

3. The method according to claim 2, wherein the preset threshold is a threshold of focus evaluation values, and the determining the target focus position from the plurality of focus positions according to the focus evaluation values corresponding to the plurality of focus positions and the preset threshold includes:

sequentially comparing the magnitude relation between the plurality of focusing evaluation values and the preset threshold along a first direction, wherein the first direction is the direction in which the camera module moves among the plurality of focusing positions;

Determining a plurality of first candidate focusing positions which are continuous in the first direction according to the size relation, wherein the focusing evaluation value of at least one first candidate focusing position in the plurality of first candidate focusing positions is larger than or equal to the preset threshold value;

determining focusing positions corresponding to extreme points of focusing evaluation values of the plurality of first candidate focusing positions according to focusing evaluation values corresponding to the plurality of first candidate focusing positions;

and determining the target focusing position as the focusing position corresponding to the extreme point.

4. A method according to claim 3, wherein after said sequentially comparing the magnitude relation of the plurality of focus evaluation values with the preset threshold value, the method further comprises:

determining a plurality of second candidate focusing positions which are continuous in the first direction according to the size relation, wherein the focusing evaluation value of each of the plurality of second candidate focusing positions is smaller than the preset threshold value;

amplifying a plurality of focusing evaluation values of the plurality of second candidate focusing positions to obtain a plurality of amplified focusing evaluation values;

and determining the target focusing position as the focusing position corresponding to the extreme points of the plurality of amplified focusing evaluation values.

5. The method according to claim 2, wherein the preset threshold is a threshold of a difference between two focus evaluation values, and the determining the target focus position from the plurality of focus positions according to the focus evaluation values corresponding to the plurality of focus positions and the preset threshold includes:

sequentially acquiring evaluation differences between two adjacent focusing evaluation values in the plurality of focusing evaluation values along a first direction, wherein the first direction is the direction in which the camera module moves between the plurality of focusing positions;

determining a plurality of third candidate focusing positions which are continuous in the first direction according to the evaluation difference value between two adjacent focusing evaluation values in the plurality of focusing evaluation values, wherein the evaluation difference value of at least one pair of adjacent third candidate focusing positions in the plurality of third candidate focusing positions is larger than or equal to the preset threshold value;

determining focusing positions corresponding to extreme points of focusing evaluation values of the plurality of third candidate focusing positions according to focusing evaluation values corresponding to the plurality of third candidate focusing positions;

and determining the target focusing position as the focusing position corresponding to the extreme point.

6. The method according to claim 5, wherein after sequentially acquiring the evaluation differences between adjacent two of the plurality of focus evaluation values in the acquisition order, the method further comprises:

Determining a plurality of fourth candidate focusing positions which are continuous in the first direction according to the evaluation difference value between two adjacent focusing evaluation values in the plurality of focusing evaluation values, wherein the evaluation difference value of each pair of adjacent fourth candidate focusing positions in the plurality of fourth candidate focusing positions is smaller than the preset threshold value;

amplifying a plurality of focusing evaluation values of the fourth candidate focusing positions to obtain a plurality of amplified focusing evaluation values;

and determining the target focusing position as the focusing position corresponding to the extreme points of the plurality of amplified focusing evaluation values.

7. The method according to claim 4 or 6, wherein the plurality of amplified focus evaluation values are obtained by amplifying a plurality of focus evaluation values by a preset multiple, the preset multiple being positively correlated with the threshold value.

8. An autofocus device, the autofocus device comprising:

the acquisition module is used for acquiring image data acquired by the camera module at a plurality of focusing positions;

the generation module is used for processing the image data based on a preset focusing evaluation function and generating focusing evaluation values corresponding to the focusing positions;

And the determining module is used for determining a target focusing position from the focusing positions according to the focusing evaluation values corresponding to the focusing positions and a preset threshold value.

9. A computer readable storage medium, on which a computer program is stored, characterized in that the program, when being executed by a processor, implements the steps of the method according to any one of claims 1-7.

10. An electronic device, comprising:

a memory having a computer program stored thereon;

a processor for executing the computer program in the memory to implement the steps of the method of any one of claims 1-7.

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