WO2016161734A1

WO2016161734A1 - Autofocusing method and device

Info

Publication number: WO2016161734A1
Application number: PCT/CN2015/086686
Authority: WO
Inventors: 慕千里
Original assignee: 中兴通讯股份有限公司
Priority date: 2015-04-07
Filing date: 2015-08-11
Publication date: 2016-10-13
Also published as: CN106154688A; CN106154688B

Abstract

An autofocusing method and device. The autofocusing method comprises: acquiring a blurring diameter value of an image sensor of a terminal, an aperture value of a lens and a motion parameter of a motor (S401); calculating object distance ranges of various steps of the motor according to the blurring diameter value, the aperture value of the lens and the motion parameter of the motor (S402); eliminating a step of which the object distance range is within object distance ranges of other steps from the steps (S403); acquiring grey contrast values of locations corresponding to the remaining steps after the elimination (S407); and determining, according to the grey contrast values, the location of a step as a focused focus point from the remaining steps after the elimination (S406). The invention solves the problem in the relevant art that the imaging quality is poor caused by an inaccurate focusing due to a fixed speed and step of a motor, and realizes a rapid autofocusing without affecting the imaging quality, thereby improving the user experience.

Description

Method and device for autofocus

Technical field

The present invention relates to the field of digital image processing technologies, and in particular, to a method and apparatus for autofocus.

Background technique

In recent years, with the advancement and development of technology, camera electronic devices (terminals) have become an indispensable part of people's lives, especially smartphone tablet computers, which have changed people's lifestyles. Among them, the method and device for terminal autofocus is one of the most important factors determining the image quality of the terminal.

According to the optical principle, to capture a clear image, the focal length (f), object distance (u) and image distance (v) of the lens need to meet:

When the image is clear, the sharpness and detail of the image are rich, and in the spatial domain, the grayscale contrast value of the adjacent pixel points is the largest. According to this principle, the grayscale contrast value of the image in the in-focus state is maximized by extracting the contour of the focus window of the image and the grayscale contrast value of the edge. Therefore, the lens is moved by the motor to change the image distance, and the grayscale contrast value of the acquired image is calculated in real time, and the position where the grayscale contrast value is the largest is the focus position.

As shown in FIG. 1 , a two-dimensional map of gray contrast and image distance in the related art can be obtained from FIG. 1 , and the gray contrast curve has three characteristics, 1) unimodality, that is, only one gray contrast maximum; 2) Monotonicity, that is, on both sides of the grayscale contrast maximum, the grayscale contrast curve monotonically decreases or decreases; 3) polarity, it can be judged whether the current focus position is before or after the focus.

In the related art, to achieve focusing, the lens moves from the starting position to the ending position, and the entire stroke is completed according to a fixed speed, a fixed step size, and a fixed step number, since the object distance and the image distance of the lens are not linear, as shown in the figure. 2 is shown. This method has the following drawbacks: if the step size is small, the number of steps increases, causing the focusing time to be too long, and if the step size is large, the focus is inaccurate and unstable.

Summary of the invention

The embodiment of the invention provides a method and a device for autofocusing, which solves the problem that the image quality is poor due to the fixed speed and step size of the motor cannot be accurately focused in the related art.

In order to solve the above problem, the embodiment of the present invention adopts the following technical solution: a method for autofocusing, comprising: acquiring a blur diameter value of an image sensor of a terminal, an aperture value of a lens, and a motion parameter of the motor; according to the blur diameter value, The aperture value of the lens and the motion parameter of the motor calculate a range of object distances of the steps of the motor; in the stepping step, the step of the object distance range in the range of the object distance of other steps is removed; The grayscale contrast value of the corresponding position of each step is determined; a step position is determined as the focus of the focus from the step remaining after the culling according to the gradation contrast value.

Optionally, determining a position of the step from the remaining steps according to the grayscale contrast value as a focus of focus includes: selecting to satisfy the following formula:

When n ² >i, A _n =X _i , the remaining step after culling is used as the first focus step; by controlling the motor motion to push the focus window from near to far to the position corresponding to the first focus step Focusing separately, when an inflection point occurs in the gradation contrast value of the position corresponding to three consecutive steps in the first focus step, selecting two of the positions corresponding to the consecutive three steps are larger Any position corresponding to the step is used as the focus of the focus; otherwise, the position corresponding to the step with the largest gray contrast value is selected as the focus of the focus; X _i is the remaining step, and A _n is the first focus step , i, n are positive integers.

Optionally, when the gray contrast value of the position corresponding to the three consecutive steps in the first focus step has an inflection point, the method further includes: selecting to satisfy the following formula: B _n =X _(NA-3n) , when 3n≤N _A , B _n = X ₁ , the remaining step after culling as the second focus step; by controlling the motor motion to push the focus window from far to near to focus on the position corresponding to the second focus step, when An inflection point occurs in a grayscale contrast value of a position corresponding to three consecutive steps in the second focus step, and then a step in which the gray contrast value is larger in the position corresponding to the three consecutive steps is selected. Corresponding any position as the focus of focus; otherwise, the position corresponding to the step with the largest grayscale contrast value is selected as the focus of focus; N _A is the number of the farthest step determined in the first focus step , B _n is the second focus step.

Optionally, after the inflection point occurs in the grayscale contrast value of the position corresponding to the three consecutive steps in the second focus step, the method further includes: selecting to satisfy: C _n =X _(NB+n) , after the culling is left Stepping as a third focusing step; pushing the focusing window by motor motion to focus on the third focusing step from near to far, respectively, when the third focusing step is grayed out corresponding to three consecutive steps If an inflection point occurs in the degree contrast value, the position corresponding to the step with the largest gray contrast value in the position corresponding to the three consecutive steps is selected as the focus of the focus; otherwise, the position corresponding to the step with the largest gray contrast value is selected as the position Focus of focus; C _n is a third focus step, and N _B is the number of the most recent step determined in the second focus step.

Optionally, determining a grayscale contrast value of one of the inflection points of the grayscale contrast value of the position corresponding to three consecutive steps in the first focusing step as the first threshold, and the second focusing step The grayscale contrast value of one of the inflection points of the grayscale contrast value corresponding to the three consecutive steps is determined as a second threshold, and the grayscale contrast value of the focus is greater than the second threshold, the second threshold And greater than the first threshold; acquiring a grayscale contrast value of the current focus window, if the current grayscale contrast value is greater than the second threshold, less than the grayscale contrast value of the focus, performing the step of selecting the third focus step; if the current gray If the degree contrast value is greater than the first threshold, less than the second threshold, the step of selecting the second focus step is performed; if the current gray level contrast value is less than the first threshold, the step of selecting the first focus step is performed.

Optionally, the speed of movement of the motor is greater according to a distance between two adjacent focal points Small control.

An apparatus for autofocusing, comprising: a parameter acquisition module, configured to acquire a blur diameter value of an image sensor in the terminal, an aperture value of the lens, and a motion parameter of the motor; and a distance range calculation module configured to be based on the blur diameter value, The aperture value of the lens and the motion parameter of the motor calculate a range of object distances of the various steps of the motor; the step culling module is configured to remove the object distance range in the step by other distances in the stepping distance Stepping; a grayscale contrast obtaining module, configured to obtain a grayscale contrast value of a corresponding position of each step remaining after the culling; the focus determining module is set to a step that is left after the culling according to the grayscale contrast value Determines the position of a step as the focus of focus.

Optionally, the focus determining module comprises: a first focus step selection sub-module, configured to select the following formula:

When n ² >i, A _n =X _i , the remaining step after culling is used as the first focus step; the first focus determination sub-module is set to push the focus window from near to far by controlling motor motion The positions corresponding to the first focus step are respectively focused, and when an inflection point occurs in the gray contrast value of the position corresponding to three consecutive steps in the first focus step, the position corresponding to the three consecutive steps is selected. Any position corresponding to the two steps with a large grayscale contrast value is used as the focus of focus; otherwise, the position corresponding to the step with the largest grayscale contrast value is selected as the focus of focus; X _i is the remaining step In, A _n is the first focus step, and i and n are positive integers.

Optionally, the focus determining module further includes: a second focus step selection sub-module, configured to select an inflection point after the gray-scale contrast value of the position corresponding to three consecutive steps in the first focus step The following formula is satisfied: B _n =X _(NA-3n) , when 3n≤N _A , B _n =X ₁ , the remaining step after culling is used as the second focus step; the second focus determination sub-module, setting In order to control the movement of the motor to push the focus window to focus on the position corresponding to the second focus step from far to near, when the gray contrast value of the position corresponding to three consecutive steps in the second focus step has an inflection point And selecting any position corresponding to the two steps with the larger gray contrast value in the position corresponding to the three consecutive steps as the focus of the focus; otherwise, selecting the step corresponding to the maximum gray contrast value The position is the focus of focus; N _A is the number of the farthest step determined in the first focus step, and B _n is the second focus step.

Optionally, the focus determining module further includes: a third focus step selection sub-module, configured to select an inflection point after the gray-scale contrast value of the position corresponding to three consecutive steps in the second focus step Satisfying: C _n =X _(NB+n) , the remaining step after culling is used as the third focus step; the third focus determining sub-module is set to push the focus window from near to far by the motor motion to the first The three focus steps are separately focused, and when the gray contrast value of the position corresponding to the three consecutive steps in the third focus step has an inflection point, the gray contrast value of the position corresponding to the three consecutive steps is selected to be the largest. The corresponding position of the step is used as the focus of focus; otherwise, the position corresponding to the step with the largest gray contrast value is selected as the focus of focus; C _n is the third focus step, and N _B is the second focus step Determine the number of the most recent step.

Optionally, the method further includes: a threshold determining module, configured to determine a grayscale contrast value of one of the inflection points of the grayscale contrast value corresponding to the position corresponding to three consecutive steps in the first focusing step as the first a threshold value, where a grayscale contrast value of one of the inflection points of the grayscale contrast value of the position corresponding to three consecutive steps in the second focus step is determined as a second threshold, and the grayscale contrast value of the focus is greater than a second threshold, the second threshold is greater than the first threshold; the processing module is configured to obtain a grayscale contrast value of the current focus window, and if the current grayscale contrast value is greater than the second threshold, less than the grayscale contrast value of the focus, Sending a trigger start command to the third focus step selection submodule; if the current gray scale contrast value is greater than the first threshold and less than the second threshold, sending a trigger start command to the second focus step selection submodule; Such as If the current grayscale contrast value is less than the first threshold, a triggering start command is sent to the first focus step selection submodule.

Advantageous effects of embodiments of the present invention:

Embodiments of the present invention provide a method and apparatus for autofocusing, which are obtained by acquiring a blur diameter value of an image sensor of a terminal, an aperture value of a lens, and a motion parameter of a motor, and calculating a range of object distances of each step of the motor, and rejecting a step of the object distance in the range of the object distance of the other steps, and then obtaining the gray contrast value of the corresponding position of each step remaining after the culling; the remaining steps after the gradation according to the gradation value Into the middle to determine a step position as the focus of focus. The scheme eliminates the steps in the object distance range of other steps, so that the newly obtained stepping object distance range does not overlap, the number of motor movements is reduced, and the moving step of the motor is also performed. The change has been made to achieve fast autofocus without affecting its image quality and improving the user experience.

DRAWINGS

The drawings described herein are intended to provide a further understanding of the invention, and are intended to be a part of the invention. In the drawing:

Figure 1 is a two-dimensional map of gray scale contrast and image distance in the terminal;

Figure 2 is a graph of image distance and object distance;

3 is a flowchart of a method for autofocus according to Embodiment 1 of the present invention;

4 is a detailed flowchart of a method for automatic multiple focus according to Embodiment 1 of the present invention;

FIG. 5 is a graph of image distance and gray scale contrast according to Embodiment 1 of the present invention; FIG.

FIG. 6 is a schematic structural diagram of an apparatus for autofocus according to Embodiment 2 of the present invention.

detailed description

The present invention will be further described in detail below with reference to the accompanying drawings.

Embodiment 1:

As shown in FIG. 3 , a flowchart of a method for autofocus according to Embodiment 1 of the present invention is shown in FIG. 3 .

S301: Acquire a blur diameter value of an image sensor of the terminal, an aperture value of the lens, and a motion parameter of the motor;

The terminal in the embodiment of the present invention includes: a mobile phone, a tablet, a palmtop computer, a camera, a camera, etc.; the motion parameters of the motor include: the motor stroke and the oscillation frequency and the oscillation time when the motor drives the lens to move; in this embodiment, by reading The parameters written in the terminal memory are taken to obtain the blur diameter value of the image sensor, the aperture value of the lens, the motor stroke, and the oscillation frequency and the oscillation time when the motor drives the lens movement; the oscillation frequency and the oscillation time for the motor motion can also be Measured by a special measuring instrument;

S302: Calculate a range of object distances of each step of the motor according to the fuzzy diameter value, the aperture value of the lens, and the motion parameter of the motor;

It should be noted that, in the image sensor of the terminal, the length and speed of each step of the motor are set according to the blur diameter value, the aperture value of the lens, and the motion parameter of the motor; the length of the motor stroke and the stepping speed The relationship is:

Where S is the motor stroke and u is the length of the step; different motors are matched with different lenses, the motor oscillation frequency and the oscillation time are different; the relationship between the motor speed and the oscillation time is v _i =f'.F(t _f ), v _i is the motion speed, t _f is the oscillation time, and f′ is the oscillation frequency; for each step of moving in the motor, the object distance range corresponding to each step includes: Near Focus Limit:

And Far Focus Limit:

Where H is the hyperfocal distance,

A is the lens aperture value, and d is the image sensor blur diameter; the corresponding u _N and u _F after each step movement of the motor are calculated by the above method;

S303: Stepping out the step of the object distance range in the stepping distance of the other step in the stepping;

Alternatively, it can be obtained by comparing the object distance ranges of adjacent steps by comparing the values of u _N and u _F in adjacent steps, and selecting a step that can cover other focus objects, that is, The object distance range is eliminated in steps of other object distances, so that in the remaining steps, the distances of adjacent steps are no longer the same, so that the distance of each step of the motor is no longer the same, but It is also possible to cover the range of object distances that it can cover, and in this step, the extra steps are eliminated; for example, in this embodiment, it is assumed that the new moving step of the motor is X _i , where X _i is After the culling, the step remaining, i is a positive integer, that is, the motor will move according to the position corresponding to the new step X _i , and the number of steps for completing the formation of the entire motor will be reduced;

S304: Obtain a grayscale contrast value of a corresponding position of each step remaining after the culling;

Each time the motor moves one step, there is a corresponding grayscale contrast value in the corresponding position of the step; the grayscale contrast value corresponding to each step corresponding position is obtained, usually by controlling the motor to move to the stepping Corresponding position, and focusing on the position, thereby obtaining a grayscale contrast value of the pixel in the focus window;

S305: determining, according to the grayscale contrast value, a step position from the step remaining after the culling as a focus of focusing;

In this embodiment, by controlling the motor to focus on the corresponding positions of the steps remaining after each culling, the gradation contrast values corresponding to the respective steps are obtained, and the maximum gradation contrast value is selected among the obtained gradation contrast values. The position of the corresponding step is used as the focus of the focus, or the position where the gradation contrast value is selected to be in the range of the image in which the high-definition imaging is satisfied is determined as the focus of the focus. In this embodiment, by removing the range of object distances from other steps The repeated stepping reduces the number of movements of the motor, and the quality of the imaging is not degraded, and the possibility of fast focusing can be achieved, thereby improving the user experience.

Preferably, step S104 determines a position of the step from the remaining steps according to the grayscale contrast value as the focus of the focus includes: selecting to satisfy the following formula:

When n ² >i, A _n =X _i , the remaining step after culling is used as the first focus step; by controlling the motor motion, pushing the focus window from near to far to the position corresponding to the first focus step respectively Focusing, when an inflection point occurs in the grayscale contrast value of the position corresponding to three consecutive steps in the first focusing step, the corresponding two steps of the grayscale contrast value corresponding to the position corresponding to three consecutive steps are selected. Any position is the focus of focus; otherwise, the position corresponding to the step with the largest gray contrast value is selected as the focus of focus; X _i is the remaining step, A _n is the first focus step, i, n are A positive integer; in this embodiment, by selecting a step that satisfies the above formula as the first focus step, and focusing only on the selected first focus step, calculating the corresponding step from near to far The grayscale contrast value of the position, after the inflection point occurs in the grayscale contrast value of the position corresponding to three consecutive steps in the first focus step, the focus processing of the other first focus step positions is not required, only in the The position corresponding to three consecutive steps Any position corresponding between two steps with a large gray-scale contrast value as a focus of focus; any position includes a position corresponding to any step between two steps with a large gray-scale contrast value, Or the position corresponding to the remaining step after any culling between the two steps with a large grayscale contrast value; selecting any of the positions as the focus of the focus can not only achieve accurate focus, but also clear imaging, and In the process of focusing, it is only necessary to continue the focus after the inflection point of the gray contrast value of the corresponding position of three consecutive steps, so that the focus can be found more quickly and the focus can be achieved.

In this embodiment, since the position between the two steps obtained by the first focus is large, the relative error of the focus of the focus obtained by the selection is also large, in order to obtain the position of the focus focus more accurately, thereby requiring The range of the selection is reduced, and the step of narrowing the selection range includes: when an inflection point occurs in the gray contrast value of the position corresponding to three consecutive steps in the first focus step, the following formula is satisfied: B _n =X _{(NA- 3n)} , when _3n ≤ N _A , B _n = X ₁ , the remaining step after culling as the second focus step; by controlling the motor motion to push the focus window from far to near corresponding to the second focus step The position is respectively focused, that is, during the current focusing process, after the focus of the first focus step is stopped, that is, when the gradation contrast value in the first focus step has an inflection point; when the second focus step is in progress If an inflection point occurs in the gray contrast value of the position corresponding to the three consecutive steps, any position corresponding to the two steps with the larger gray contrast value in the position corresponding to the three consecutive steps is selected as the focus of the focus; Otherwise, choose The position corresponding to the step with the largest gray scale contrast value is taken as the focus of the focus; N _A is the number of the farthest step determined in the first focus step, and B _n is the second focus step; in this embodiment In the middle, by selecting the step that satisfies the above formula as the second focus step, and focusing only on the selected second focus step, calculating the gray contrast value of the corresponding step position from far to near, when After the inflection point occurs in the gray contrast value of the position corresponding to the three consecutive steps in the second focus step, the position of the other second focus step is not required to be focused, and only needs to be in the position corresponding to three consecutive steps. Any position corresponding to the two steps with a large grayscale contrast value is used as the focus of the focus; likewise, any position includes any step between the two steps with a large grayscale contrast value. Position, or the position corresponding to the remaining step after any culling between the two steps with a large grayscale contrast value; selecting any of the positions as the focus of the focus more selectively achieves the accuracy of the focus may.

Optionally, in order to make the range of the determined focus of the focus more accurate, after the inflection point occurs in the gray contrast value of the position corresponding to the three consecutive steps in the second focus step, the selection further includes: C _n = X _(NB+n) , the remaining step after culling is used as the third focus step; the focus window is pushed by the motor motion to focus on the third focus step from near to far, and the third focus step is three consecutively If the grayscale contrast value of the corresponding position of the step has an inflection point, the position corresponding to the step with the largest gray contrast value among the positions corresponding to the three consecutive steps is selected as the focus of the focus; otherwise, the grayscale contrast value is selected to be the largest. The corresponding position of the step is used as the focus of focus; C _n is the third focus step, and N _B is the number of the nearest step determined in the second focus step; through the above three steps, from near to far, from far Control the motor to move to the near and then from near to far, and separately focus to obtain the gray contrast value of each step position, and finally obtain the most accurate step position of the gray contrast value in the terminal. , Compared with the gradation current contrast value acquired by the gradation contrast value, how to obtain a controlled movement of the motor current so that the quality of the resulting photographs captured best.

Optionally, the method for focusing on a target that needs to be photographed currently includes: first, determining a grayscale contrast value of one of the inflection points of the grayscale contrast value of the position corresponding to three consecutive steps in the first focus step as the first a threshold value, determining a grayscale contrast value of one of the inflection points of the grayscale contrast value corresponding to the three consecutive steps in the second focus step as a second threshold, and three consecutive steps in the third step The grayscale contrast value of the corresponding position appears as the grayscale contrast value of the focus of the inflection point, the grayscale contrast value of the focus is greater than the second threshold, and the second threshold is greater than the first threshold; acquiring the current focus The grayscale contrast value of the window, if the current grayscale contrast value is greater than the second threshold and less than the grayscale contrast value of the focus, the step of selecting the third focus step is performed, thereby obtaining an accurate focus of the current target; if current The grayscale contrast value is greater than the first threshold, and less than the second threshold, the step of selecting the second focus step is performed, and similarly, the execution is performed. After the step of the second focus step, in order to focus the accuracy, it is necessary to continue the step of performing the third one-step step, so that the determined focus focus will be more accurate; if the current gray scale contrast value is less than the first threshold, Then, the step of selecting the first focus step is performed, and the situation is similar to the above case, and will not be described here.

It should be noted that in the terminal, the speed of the motor movement is controlled according to the distance between two adjacent steps. In order to reduce the interference caused by the inertia and the motor's own oscillation, the speed of the motor also changes during the above-described determination of the grayscale contrast value of each focus step. For example, for the determination of the position gradation contrast value of the first focus step, the scanning speed is x ₁ , and for the determination of the position gradation contrast value of the second focus step, the scanning speed is x ₂ , for the first The determination of the position gray scale contrast value of the three focus step is that the scanning speed is x ₃ ; wherein the following condition exists: x ₁ = x ₂ k ₁ = x ₃ k ₂ , 0 < k ₂ < k ₁ < 1.

For example, the following describes in detail a specific embodiment to describe a method for automatically performing multiple times of focusing in the present solution. As shown in FIG. 4 , a detailed flowchart of a method for automatic multiple focus according to Embodiment 1 of the present invention is shown in FIG. 4 . And Figure 5,

S401: reading a blur diameter of an image sensor written in a memory of the terminal, an aperture of the lens, a motor stroke, and an oscillation frequency and an oscillation time when the motor drives the lens to move;

S402: calculating a corresponding object distance range after each step movement of the motor according to the blur diameter, the aperture of the lens, the motor stroke, and the oscillation frequency and the oscillation time when the motor drives the lens to move;

S403: Comparing the object distance range of the position of the adjacent step, and removing the object distance range from the step included in the object distance range of the other step, and obtaining the step remaining after the culling, the corresponding position of the step Set to X _i ;

S404: Select to satisfy the following formula:

When n ² >i, A _n =X _i , the remaining step after culling is taken as the first focus step; and the focus corresponding to the first focus step is respectively focused from near to far, when the first focus is When the gray contrast value of the position corresponding to three consecutive steps in the step has an inflection point, the position corresponding to the two steps with the larger gray contrast value in the position corresponding to the three consecutive steps is determined as the focus range. And selecting one of the larger step corresponding positions of the gray scale contrast value as the first threshold Y1;

S405: The selection satisfies the following formula: B _n =X _(NA-3n) , when 3n≤N _A , B _n =X ₁ , the remaining step after the culling is taken as the second focus step, and from far to near Selecting the position corresponding to the second focus step respectively, and when the inflection point occurs in the gray contrast value of the position corresponding to the three consecutive steps in the second focus step, selecting the gray contrast value in the position corresponding to the three consecutive steps The corresponding position between the two larger steps is taken as the focus range, and the gray contrast value of one of the larger step corresponding positions is selected as the second threshold Y2;

S406: Selecting the following formula: C _n =X _(NB+n) , the remaining step after the culling is used as the third focus step, and respectively focusing on the position corresponding to the third focus step from near to far, when In the third focus step, the inflection point appears in the gray contrast value of the position corresponding to the three consecutive steps, and the position corresponding to the step with the largest gray contrast value in the position corresponding to the three consecutive steps is selected as the focus of the focus, and The grayscale contrast value corresponding to the focus is Yf, and the focus is completed;

S407: After t ms, obtaining the gray contrast value Y of the current focus window;

S408: determining whether Y2 < Y1 < Yf is satisfied, if yes, then go to S206; if not, then go to S209;

S409: It is judged whether Y1<Y1<Y2 is satisfied, and if yes, the process goes to S205; if not, the process goes to S204.

The embodiment realizes the possibility of continuous focusing, and can realize focusing relatively quickly and accurately, not only improving the imaging quality, but also saving the focusing time and improving the user experience.

Embodiment 2:

FIG. 6 is a schematic structural diagram of an apparatus for autofocus according to Embodiment 2 of the present invention. Referring to FIG. 6, the autofocus apparatus 60 includes: a parameter acquisition module 601, an object distance range calculation module 602, and a step rejection module. 603, a grayscale contrast acquisition module 604 and a focus determination module 605; the parameter acquisition module 601 is configured to acquire a blur diameter value of the image sensor in the terminal, an aperture value of the lens, and a motion parameter of the motor; the object distance range calculation module 602 is configured to be based on the blur The diameter value, the aperture value of the lens, and the motion parameter of the motor calculate the object distance range of each step of the motor; the step culling module 603 is configured to remove the step of the object distance range within the step distance of the other step in the stepping Grayscale contrast acquisition module 604 is set to obtain each of the remaining after culling The grayscale contrast value of the corresponding position of the step; the focus determining module 605 is configured to determine a position of the step as the focus of the focus from the step remaining after the culling according to the gradation contrast value. In this embodiment, by eliminating the step repeated with the other stepped object distance range, the number of movements of the motor is reduced, and the quality of the imaging is not degraded, and the possibility of fast focusing can be achieved, and the user's Use experience.

In an embodiment, the focus determination module 605 includes a first focus step selection sub-module configured to select the following formula:

When n ² >i, A _n =X _i , the remaining step after culling is used as the first focus step; the first focus determination sub-module is set to push the focus window from near to far by controlling motor motion The positions corresponding to the first focus step are respectively focused. When the gray contrast value of the position corresponding to three consecutive steps in the first focus step has an inflection point, the gray contrast value in the position corresponding to the three consecutive steps is selected. Any position corresponding to the two large steps is used as the focus of focus; otherwise, the position corresponding to the step with the largest gray contrast value is selected as the focus of focus; X _i is the remaining step, A _n is the first A focus step, i, n is a positive integer.

Optionally, the focus determining module 605 further includes: a second focus step selection sub-module, configured to meet the following formula after the inflection point occurs in the gray-scale contrast value of the position corresponding to three consecutive steps in the first focus step; :B _n =X _(NA-3n) , when 3n≤N _A , B _n =X ₁ , the remaining step after culling is used as the second focus step; the second focus determination sub-module is set to pass the control The motor motion pushes the focus window to focus on the position corresponding to the second focus step from far to near. When the gray contrast value of the position corresponding to three consecutive steps in the second focus step has an inflection point, three consecutive steps are selected. Enter any position corresponding to the two steps with a large grayscale contrast value in the corresponding position as the focus of focus; otherwise, select the position corresponding to the step with the largest grayscale contrast value as the focus of focus; N _A is The number of the farthest step determined in the first focus step, B _n is the second focus step;

Preferably, the focus determining module 605 further includes: a third focus step selection sub-module configured to: when the inflection point of the gray-scale contrast value of the position corresponding to three consecutive steps in the second focus step occurs, the selection is satisfied: C _n =X _(NB+n) , the remaining step after culling is used as the third focus step; the third focus determination sub-module is set to push the focus window by motor motion to focus on the third focus step from near to far respectively. When an inflection point occurs in the gray contrast value of the position corresponding to three consecutive steps in the third focus step, the position corresponding to the step with the largest gray contrast value in the position corresponding to the three consecutive steps is selected as the focus of the focus. ; otherwise, the position corresponding to the step with the largest gray contrast value is selected as the focus of focus; C _n is the third focus step, and N _B is the number of the nearest step determined in the second focus step;

The autofocus device 60 further includes: a threshold determining module configured to determine a grayscale contrast value of one of the inflection points of the grayscale contrast value of the position corresponding to three consecutive steps in the first focusing step as the first threshold a grayscale contrast value of one of the inflection points of the grayscale contrast value corresponding to the position of the three consecutive steps in the second focus step is determined as a second threshold, and the grayscale contrast value of the focus is greater than the second threshold, The second threshold is greater than the first threshold; the processing module is configured to obtain the grayscale contrast value of the current focus window, and if the current grayscale contrast value is greater than the second threshold and less than the focus grayscale contrast value, the third focus step is selected. The submodule sends a trigger start command; if the current grayscale contrast value is greater than the first threshold and less than the second threshold, sending a trigger start command to the second focus step selection submodule; if the current grayscale contrast value is less than the first threshold , the trigger start command is sent to the first focus step selection sub-module.

Embodiments of the present invention provide a method and apparatus for autofocusing, which eliminates steps of a stepped object distance range within a range of other stepped object distances, and then obtains the remaining steps after the rejection. The grayscale contrast value of the corresponding position; the position of one step is determined as the focus of the focus from the step remaining after the culling according to the gradation contrast value. The scheme eliminates the step in the object distance range of other steps, so that the newly obtained stepping object distance ranges do not coincide, reducing the number of motor movements and the stepping distance of the motor movement. It has also been changed to achieve fast autofocus without affecting its image quality and improving the user experience.

The above is a further detailed description of the present invention in connection with the specific embodiments, and the specific embodiments of the present invention are not limited to the description. It will be apparent to those skilled in the art that the present invention may be made without departing from the spirit and scope of the invention.

Industrial applicability

As described above, by the above-described embodiments and preferred embodiments, by stepping out the steps in the range of the other stepped objects, the newly obtained stepped object distance ranges do not coincide, reducing motor movement. The number of times, and the moving step size of the motor have also been changed, thereby achieving fast autofocus without affecting the image quality and improving the user experience.

Claims

A method of autofocus, comprising the following steps:

Obtaining a fuzzy diameter value of the image sensor of the terminal, an aperture value of the lens, and a motion parameter of the motor;

Calculating an object distance range of each step of the motor according to the blur diameter value, the aperture value of the lens, and the motion parameter of the motor;

Stepping out the range of object distances within the range of object distances of other steps in the stepping;

Obtaining a grayscale contrast value of a corresponding position of each step remaining after the culling;

A position of one step is determined as a focus of focus from the step of remaining after the culling according to the gradation contrast value.
The method of autofocusing according to claim 1, wherein determining a position of one step from the remaining steps based on the gradation contrast value as a focus of focus comprises: selecting to satisfy the following formula:
When n 2 >i, A n =X i , the remaining step after culling is used as the first focus step; by controlling the motor motion to push the focus window from near to far to the position corresponding to the first focus step Focusing separately, when an inflection point occurs in the gradation contrast value of the position corresponding to three consecutive steps in the first focus step, selecting two of the positions corresponding to the consecutive three steps are larger Any position corresponding to the step is used as the focus of the focus; otherwise, the position corresponding to the step with the largest gray contrast value is selected as the focus of the focus; X i is the remaining step, and A n is the first focus step , i, n are positive integers.
The method of autofocusing according to claim 2, wherein the inflection point of the grayscale contrast value of the position corresponding to three consecutive steps in the first focus step further comprises: selecting to satisfy the following formula:
When 3n ≤ N A , B n = X 1 , the remaining step after culling is used as the second focus step; by controlling the motor motion to push the focus window from far to near to the position corresponding to the second focus step Focusing separately, when an inflection point occurs in the gradation contrast value of the position corresponding to three consecutive steps in the second focus step, selecting two of the positions corresponding to the consecutive three steps are larger Any position corresponding to the step is the focus of the focus; otherwise, the position corresponding to the step with the largest gray contrast value is selected as the focus of the focus; N A is the farthest determined in the first focus step The number of the step, B n is the second focus step.
The method of autofocusing according to claim 3, wherein after the inflection point occurs in the grayscale contrast value of the position corresponding to the three consecutive steps in the second focus step, the method further comprises: selecting to satisfy:
The remaining step after the culling is used as the third focus step; the focus window is pushed by the motor motion to focus on the third focus step from near to far, and three consecutive steps in the third focus step If an inflection point occurs in the grayscale contrast value of the corresponding position, the position corresponding to the step with the largest gray contrast value among the positions corresponding to the three consecutive steps is selected as the focus of the focus; otherwise, the step with the largest grayscale contrast value is selected. The corresponding position is taken as the focus of focus; C n is the third focus step, and N B is the number of the most recent step determined in the second focus step.
The method of autofocusing according to claim 4, wherein the gradation contrast value of one of the inflection points of the gradation contrast value of the position corresponding to three consecutive steps in the first focus step is determined as the first a threshold value, wherein a grayscale contrast value of one of the inflection points of the grayscale contrast value of the position corresponding to three consecutive steps in the second focus step is determined as a second threshold, and the grayscale contrast value of the focus The second threshold is greater than the first threshold; the second threshold is greater than the first threshold; the grayscale contrast value of the current focus window is obtained, and if the current grayscale contrast value is greater than the second threshold and less than the grayscale contrast value of the focus, the third selection is performed. a step of focusing stepping; if the current grayscale contrast value is greater than the first threshold, less than the second threshold, performing the step of selecting the second focus step; if the current grayscale contrast value is less than the first threshold, performing The step of selecting the first focus step.
A method of autofocusing according to any one of claims 2 to 5, wherein the magnitude of the speed of movement of the motor is controlled according to the distance between adjacent two steps.
An autofocus device comprising:

a parameter acquisition module, configured to acquire a fuzzy diameter value of the image sensor in the terminal, an aperture value of the lens, and a motion parameter of the motor;

a object distance range calculation module, configured to calculate a range of object distances of the motor steps according to the blur diameter value, the aperture value of the lens, and the motion parameter of the motor;

a step culling module configured to remove a step in the step of the object distance range within the other step of the object distance;

a grayscale contrast obtaining module configured to obtain a grayscale contrast value of a corresponding position of each step remaining after the culling;

The focus determination module is configured to determine a position of the step as the focus of the focus from the step of the grayscale contrast value remaining after the culling.
The autofocus apparatus of claim 7, wherein the focus determination module comprises: a first focus step selection sub-module configured to select the following formula:
When n 2 >i, A n =X i , the remaining step after culling is used as the first focus step; the first focus determination sub-module is set to push the focus window from near to far by controlling motor motion Positions corresponding to the first focus step are respectively focused, and when an inflection point occurs in the gray contrast value of the position corresponding to three consecutive steps in the first focus step, the position corresponding to the three consecutive steps is selected. Any position corresponding to the two steps with a large grayscale contrast value is used as the focus of the focus; otherwise, the position corresponding to the step with the largest grayscale contrast value is selected as the focus of the focus; X i is the remaining step , A n is the first focus step, and i and n are positive integers.
The apparatus according to claim 8, wherein the focus determining module further comprises: a second focus step selection sub-module configured to be a position corresponding to three consecutive steps in the first focus step After the inflection point appears for the grayscale contrast value, the selection satisfies the following formula:
When 3n≤N A , B n =X 1 , the remaining step after culling is used as the second focus step; the second focus determination sub-module is set to push the focus window from far to near by controlling the motor motion Positions corresponding to the second focus step are respectively focused, and when an inflection point occurs in the gray contrast value of the position corresponding to three consecutive steps in the second focus step, the position corresponding to the three consecutive steps is selected Any position corresponding to the two steps with a large gray contrast value is used as the focus of the focus; otherwise, the position corresponding to the step with the largest gray contrast value is selected as the focus of the focus; N A is the first focus The number of the farthest step determined in the step, B n is the second focus step.
The apparatus of claim 9, wherein the focus determining module further comprises: a third focus step selection sub-module configured to be a position corresponding to three consecutive steps in the second focus step After the inflection point occurs for the grayscale contrast value, the selection is satisfied:
The remaining step after the culling is used as the third focus step; the third focus determining sub-module is configured to respectively push the focus window by the motor motion to focus on the third focus step from near to far, when the third If an inflection point occurs in the gray contrast value of the position corresponding to three consecutive steps in the focusing step, the position corresponding to the step with the largest gray contrast value in the position corresponding to the three consecutive steps is selected as the focus of the focus; otherwise The position corresponding to the step with the largest gray scale contrast value is selected as the focus of focus; C n is the third focus step, and N B is the number of the most recent step determined in the second focus step.
The apparatus of claim 10, further comprising: a threshold determination module configured to grayscale the position corresponding to three consecutive steps in the first focus step The grayscale contrast value of one of the inflection points of the contrast value is determined as a first threshold, and the grayscale contrast value of the position corresponding to three consecutive steps in the second focus step is grayscale of one of the inflection points The contrast value is determined to be a second threshold, the grayscale contrast value of the focus is greater than a second threshold, the second threshold is greater than the first threshold; and the processing module is configured to obtain a grayscale contrast value of the current focus window, if the current gray If the degree of contrast is greater than the second threshold, less than the grayscale contrast value of the focus, the triggering start command is sent to the third focus step selection submodule; if the current grayscale contrast value is greater than the first threshold, less than the second threshold, And sending a trigger start instruction to the second focus step selection submodule; if the current gray scale contrast value is less than the first threshold, sending a trigger start instruction to the first focus step selection submodule.