CN107643578A - A kind of Atomatic focusing method, device and mobile terminal - Google Patents

Abstract

Embodiments of the present invention provide an autofocus method, device, and mobile terminal. By obtaining the number of effective white points in the focus area corresponding to different focal lengths in a dark light and point light source environment, the pixel brightness value of the effective white point is greater than or equal to the preset value. Set the brightness threshold; select the focal length corresponding to the focus area with the least number of effective white points from different focal lengths as the target focal length; adopt the above scheme, in a dark light environment, when taking pictures of point light sources, select the effective focal length from different focal lengths. The focal length corresponding to the focus area with the least number of white points is the target focal length, and the focal length corresponding to the focus area with the fewest number of effective white points is the point with the clearest focus, which ensures the accuracy of focus and prevents out-of-focus phenomena. Improve user shooting experience.

Description

An autofocus method, device and mobile terminal

technical field

The present invention relates to the communication field, in particular to an automatic focusing method, device and mobile terminal.

Background technique

In a dark light environment, when taking pictures of point light sources such as candles and neon lights, refer to Figure 1. The existing focusing method is to use the contrast of the input image as the sharpness value, the sharpness value as the vertical coordinate, and the focal length as the horizontal coordinate Create a focus curve, and use the maximum point on the focus curve as the focus point. This focus point is a false focus point. Because the point light source in a dark environment has halos, the point with the clearest focus is not at the maximum value of the focus curve. However, if you continue to use the maximum point on the focus curve as the focus point, it will cause inaccurate focus and blurred pictures, which will affect the user's shooting experience.

In view of the above problems, it is a technical problem to be solved urgently by those skilled in the art to propose a method and device that can accurately find the focusing point when taking pictures of point light sources in a dark environment.

Contents of the invention

The main technical problem to be solved by the embodiments of the present invention is to provide an autofocus method, device and mobile terminal to solve the problem of inaccurate focus and blurred photographs when photographing a point light source in a dark environment in the prior art. question.

In order to solve the above technical problems, an embodiment of the present invention provides an autofocus method, including:

In the environment of dark light and point light source, obtain the number of effective white points in the focus area corresponding to different focal lengths, and the pixel brightness value of the effective white point is greater than or equal to the preset brightness threshold;

From the different focal lengths, the focal length corresponding to the focal area with the least number of effective white points is selected as the target focal length.

In order to solve the above technical problems, an embodiment of the present invention provides an autofocus device, including:

The obtaining module is used to obtain the number of effective white points in the focus area corresponding to different focal lengths in the environment of dark light and point light source, and the pixel brightness value of the effective white point is greater than or equal to the preset brightness threshold;

The selection module is configured to select, from different focal lengths, the focal length corresponding to the focal area with the least number of effective white points as the target focal length.

In order to solve the above technical problem, an embodiment of the present invention provides a mobile terminal, including the above-mentioned autofocus device.

In order to solve the above technical problem, an embodiment of the present invention further provides a computer storage medium, in which computer executable instructions are stored, and the computer executable instructions are used to execute the aforementioned autofocus method.

The beneficial effects of the present invention are:

According to the autofocus method, device and mobile terminal provided by the embodiments of the present invention, by obtaining the number of effective white points in the focus area corresponding to different focal lengths in the dark light and point light source environment, the pixel brightness value of the effective white point is greater than or equal to the preset Set the brightness threshold; select the focal length corresponding to the focus area with the least number of effective white points from different focal lengths as the target focal length; adopt the above scheme, in a dark light environment, when taking pictures of point light sources, select the effective focal length from different focal lengths. The focal length corresponding to the focus area with the least number of white points is the target focal length, and the focal length corresponding to the focus area with the fewest number of effective white points is the point with the clearest focus, which ensures the accuracy of focus and prevents out-of-focus phenomena. Improve user shooting experience.

Description of drawings

Fig. 1 is the curve relationship diagram of focal length and sharpness value in the prior art;

FIG. 2 is a flow chart of an autofocus method provided by Embodiment 1 of the present invention;

Fig. 3 is a curve relationship diagram between a focal length and the number of effective white spots provided by Embodiments 1 and 2 of the present invention;

FIG. 4 is a schematic diagram of an autofocus device provided by Embodiment 2 of the present invention.

detailed description

Embodiments of the present invention will be further described in detail below through specific implementation methods in conjunction with the accompanying drawings.

Embodiment one

In a dark environment, in order to ensure focus accuracy and prevent out-of-focus phenomena when taking pictures of point light sources, this embodiment provides an autofocus method, as shown in Figure 2, which includes the following steps:

S101: In a dark light and point light source environment, obtain the number of effective white points in the focus area corresponding to different focal lengths, and the pixel brightness value of the effective white point is greater than or equal to a preset brightness threshold.

In order to avoid misjudgment and ensure accuracy, the scattered white points in the focus area are excluded, and the scattered white points are not effective white points; the criteria for judging effective white points include: each white point is within its m * The number of white dots in the neighborhood of n pixels is greater than or equal to a first preset number threshold.

Wherein, the first preset quantity threshold can be (m*n-1)/2 or (m*n)/2, which means that in the m*n pixel area, there are more than half of the pixel brightness values of the white points greater than or equal to the preset Set the brightness threshold.

Wherein, the value range of the pixel brightness value is 0 to 255. The preset brightness threshold is preferably 230, m and n may be equal or different, m*n is preferably 5*5, and the first preset number threshold is preferably 12.

For example, see Table 1. Table 1 shows the pixel brightness value of each white point in the 5*5 pixel neighborhood of the current white point. The pixel brightness value of the current white point is 255. The current white point is the point in the center of Table 1. , that is, the point in the third row and third column. Since the pixel brightness value 255 of the current white point is greater than the preset brightness threshold 230, and within its 5*5 pixel neighborhood, the pixel brightness values of more than half of the white points are greater than the preset brightness threshold 230, so it can be judged that the current white point is Effective white point.

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Table 1

Before obtaining the number of effective white points in the focus area corresponding to different focal lengths, it also includes: judging whether the current display screen in the focus area is a point light source environment; judging whether the current display screen in the focus area is a point light source environment includes: adjusting the focal length, and counting different focal lengths The number of effective white points in the corresponding focus area; if the number of effective white points corresponding to at least one focal length is greater than the second set number threshold, it is determined that the current display screen in the focus area is a point light source environment.

For example, the focal lengths are f1, f2, and f3 respectively, the effective number of white points corresponding to the focal length f1 is 120, the effective number of white points corresponding to the focal length f2 is 118, and the effective number of white points corresponding to the focal length f3 is 115; if the second setting The fixed quantity threshold is 116. Since the effective white points corresponding to the focal lengths f1 and f2 are greater than the second set quantity threshold of 116, it is judged that the current display screen in the focus area is a point light source environment; if the second set quantity threshold is 125. Since the number of effective white points corresponding to the focal lengths f1, f2, and f3 is less than the second set number threshold 125, it is determined that the currently displayed image in the focus area is not a point light source environment. The second set quantity threshold may be determined through statistics after testing a large number of dark point light source scenes.

The point light sources include candles, neon lights, etc., and the number of point light sources in the current display screen of the focus area can be one or more.

Wherein, before judging whether the currently displayed image in the focus area is a point light source environment, it further includes: judging whether the currently displayed image in the focus area is a dark light scene. Specifically, it may be determined according to the brightness whether the image currently displayed in the focus area is a dark scene. The brightness can be sensed by the sensor or expressed by the exposure variable in the exposure algorithm. The longer the exposure time, the darker the brightness. As long as the brightness or exposure variable exceeds a certain threshold, it can be judged as a dark scene. The threshold can be determined according to a large number of It is determined statistically after the dark-light scene test.

Wherein, in S101, obtaining the number of effective white points in the focus area corresponding to different focal lengths can be: after adjusting the focus distance, counting the number of effective white points in the focus area corresponding to different focal lengths, and judging whether the current display image in the focus area is a point light source environment Afterwards, the number of effective white points in the focus area corresponding to the different focal lengths counted above is directly obtained. Obtaining the number of effective white points in the focus area corresponding to different focal lengths in S101 can also be: after adjusting the focus distance, counting the number of effective white points in the focus area corresponding to different focal lengths, and judging whether the current display image in the focus area is a point light source environment , adjust the focal length again, re-count the number of effective white points in the focus area corresponding to different focal lengths, and then obtain the re-counted number of effective white points in the focus area corresponding to different focal lengths.

Among them, adjusting the focal length and counting the number of effective white points in the focus area corresponding to different focal lengths includes: sequentially adjusting the focal length according to the order of the focal length from large to small, or from small to large, and counting the effective white points in the focus area corresponding to each focal length in turn number.

S102: Select the focal length corresponding to the focus area with the smallest number of effective white points from different focal lengths as the target focal length.

Obtaining the number of effective white points in the focus area corresponding to different focal lengths includes: obtaining the counted number of effective white points in the focus area corresponding to each focal length, taking the focal length as the abscissa, and the number of effective white points as the ordinate, according to the statistics The time sequence of each focal length and the corresponding number of effective white points is plotted on the coordinate map, and the points are connected into a curve according to the statistical time sequence; from different focal lengths, select the corresponding focus area with the least number of effective white points The focal length as the target focal length includes: querying the point with the least number of effective white points from the curve, and using the focal length corresponding to the point as the target focal length.

For example, see Figure 3. Figure 3 is a graph showing the relationship between the focal length and the number of effective white points. The focal lengths are f1, f2, f3, f4, f5, f6, f7, f8, and f9. The number is 120, the number of effective white points corresponding to focal length f2 is 118, the number of effective white points corresponding to focal length f3 is 115, the number of effective white points corresponding to focal length f4 is 97, and the number of effective white points corresponding to focal length f5 is 86, the number of effective white points corresponding to focal length f6 is 97, the number of effective white points corresponding to focal length f7 is 115, the number of effective white points corresponding to focal length f8 is 118, and the number of effective white points corresponding to focal length f9 is 120. It can be seen from the curve that the number of effective white points corresponding to the focal length f5 is the least, so the focal length f5 is taken as the target focal length, and the focal length f5 is the point with the clearest focus.

Alternatively, obtaining the number of effective white points in the focus area corresponding to different focal lengths includes: obtaining the counted number of effective white points in the focus area corresponding to each focal length, and comparing each focal length with the corresponding number of effective white points according to the statistical time sequence The number is arranged into a correspondence table; selecting the focal length corresponding to the focus area with the least number of effective white points from different focal lengths as the target focal length includes: querying the focal length corresponding to the focus area with the minimum number of effective white points from the correspondence table, Use this focal length as the target focal length.

For example, see Table 2. Table 2 is the correspondence table between the focal length and the number of effective white dots. The focal lengths are f1, f2, f3, f4, f5, f6, f7, f8, and f9. The number is 120, the number of effective white points corresponding to focal length f2 is 118, the number of effective white points corresponding to focal length f3 is 115, the number of effective white points corresponding to focal length f4 is 97, and the number of effective white points corresponding to focal length f5 is 86, the number of effective white points corresponding to focal length f6 is 97, the number of effective white points corresponding to focal length f7 is 115, the number of effective white points corresponding to focal length f8 is 118, and the number of effective white points corresponding to focal length f9 is 120. From the correspondence table, it can be found that the number of effective white points corresponding to the focal length f5 is the least, then the focal length f5 is taken as the target focal length, and the focal length f5 is the point with the clearest focus.

Table 2

According to the auto-focus method provided by the embodiment of the present invention, by obtaining the number of effective white points in the focus area corresponding to different focal lengths in the dark light and point light source environment, the pixel brightness value of the effective white point is greater than or equal to the preset brightness threshold; from Select the focal length corresponding to the focus area with the least number of effective white points among different focal lengths as the target focal length; using the above scheme, when taking pictures of point light sources in a dark light environment, select the minimum number of effective white points from different focal lengths The focal length corresponding to the focus area is taken as the target focal length, and the focal length corresponding to the focus area with the least number of effective white points is the point with the clearest actual focus, which ensures focus accuracy, prevents out-of-focus phenomena, and improves user shooting experience.

Embodiment two

In a dark environment, in order to ensure focus accuracy and prevent out-of-focus phenomena when taking pictures of point light sources, this embodiment provides an autofocus device, as shown in Figure 4, including:

The obtaining module 201 is used to obtain the number of effective white points in the focus area corresponding to different focal lengths in the dark light and point light source environment, and the pixel brightness value of the effective white point is greater than or equal to the preset brightness threshold.

The selection module 202 is configured to select, from different focal lengths, the focal length corresponding to the focal area with the smallest number of effective white points as the target focal length.

In order to avoid misjudgment and ensure accuracy, the scattered white points in the focus area are excluded, and the scattered white points are not effective white points; the criteria for judging effective white points include: each white point is within its m * The number of white dots in the neighborhood of n pixels is greater than or equal to a first preset number threshold.

Wherein, the first preset quantity threshold can be (m*n-1)/2 or (m*n)/2, which means that in the m*n pixel area, there are more than half of the pixel brightness values of the white points greater than or equal to the preset Set the brightness threshold.

Wherein, the value range of the pixel brightness value is 0 to 255. The preset brightness threshold is preferably 230, m and n may be equal or different, m*n is preferably 5*5, and the first preset number threshold is preferably 12.

For example, see Table 1. Table 1 shows the pixel brightness value of each white point in the 5*5 pixel neighborhood of the current white point. The pixel brightness value of the current white point is 255. The current white point is the point in the center of Table 1. , that is, the point in the third row and third column. Since the pixel brightness value 255 of the current white point is greater than the preset brightness threshold 230, and within its 5*5 pixel neighborhood, the pixel brightness values of more than half of the white points are greater than the preset brightness threshold 230, so it can be judged that the current white point is Effective white point.

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Table 1

It also includes a judging module 203, which is used to judge whether the current display image in the focused area is a point light source environment before the acquiring module 201 acquires the number of effective white points in the focused area corresponding to different focal lengths;

The judging module 203 includes a processing sub-module 2031 and a judging sub-module 2032. The processing sub-module 2031 is used to adjust the focal length and count the number of effective white points in the focus area corresponding to different focal lengths; If the number of white dots is greater than the second set number threshold, it is determined that the currently displayed image in the focus area is a point light source environment.

For example, the focal lengths are f1, f2, and f3 respectively, the number of effective white points corresponding to the focal length f1 counted by the processing sub-module 2031 is 120, the effective number of white points corresponding to the focal length f2 is 118, and the effective number of white points corresponding to the focal length f3 is 115; if the second set number threshold is 116, since the effective white dot numbers corresponding to the focal lengths f1 and f2 are greater than the second set number threshold 116, then the judging submodule 2032 judges that the current display screen of the focus area is a dot Light source environment; if the second set number threshold is 125, since the effective white points corresponding to the focal lengths f1, f2, and f3 are all less than the second set number threshold 125, then the judging submodule 2032 judges the current display screen of the focus area Not a point light environment. The second set quantity threshold may be determined through statistics after testing a large number of dark point light source scenes.

The point light sources include candles, neon lights, etc., and the number of point light sources in the current display screen of the focus area can be one or more.

Wherein, the determining module 203 is further configured to determine whether the currently displayed image in the focused area is a dark scene before determining whether the currently displayed image in the focused area is a point light source environment. Specifically, it may be determined according to the brightness whether the image currently displayed in the focus area is a dark scene. The brightness can be sensed by the sensor or expressed by the exposure variable in the exposure algorithm. The longer the exposure time, the darker the brightness. As long as the brightness or exposure variable exceeds a certain threshold, it can be judged as a dark scene. The threshold can be determined according to a large number of It is determined statistically after the low-light scene test.

Wherein, the obtaining module 201 obtains the number of effective white points in the focus area corresponding to different focal lengths may be: adjust the focal length in the processing sub-module 2031, count the number of effective white points in the focus area corresponding to different focal lengths, and judge the sub-module 2032 to determine the focus After whether the currently displayed image in the area is a point light source environment, the acquisition module 201 directly acquires the number of effective white points in the focus area corresponding to the different focal lengths counted above. The acquisition module 201 may acquire the number of effective white points in the focus area corresponding to different focal lengths: the processing sub-module 2031 adjusts the focus, counts the number of effective white points in the focus area corresponding to different focal lengths, and the determination sub-module 2032 determines the focus area After whether the current display screen is a point light source environment, the processing sub-module 2031 adjusts the focal length again, and re-counts the number of effective white points in the focus area corresponding to different focal lengths, and then the acquisition module 201 acquires the re-counted number of effective white points in the focus area corresponding to different focal lengths. Number of white points.

Wherein, the processing sub-module 2031 is specifically configured to sequentially adjust the focal length according to the order of the focal length from large to small, or from small to large, and sequentially count the number of effective white points in the focus area corresponding to each focal length.

Wherein, the obtaining module 201 is specifically used to: obtain the counted number of valid white spots in the focus area corresponding to each focal length, take the focal length as the abscissa, and the number of valid white spots as the vertical coordinate, and divide each focal length according to the statistical time sequence Draw points on the coordinate map with the corresponding number of effective white points, and connect each point into a curve according to the statistical time order; the selection module 202 is specifically used to: query the point with the least number of effective white points from the curve, and the point The corresponding focal length is taken as the target focal length.

For example, referring to FIG. 3, FIG. 3 is a graph showing the relationship between the focal length and the number of effective white points. The focal lengths are respectively f1, f2, f3, f4, f5, f6, f7, f8, and f9. The focal length f1 acquired by the acquisition module 201 The corresponding number of effective white points is 120, the number of effective white points corresponding to focal length f2 is 118, the number of effective white points corresponding to focal length f3 is 115, the number of effective white points corresponding to focal length f4 is 97, and the number of effective white points corresponding to focal length f5 is The number of effective white points is 86, the number of effective white points corresponding to focal length f6 is 97, the number of effective white points corresponding to focal length f7 is 115, the number of effective white points corresponding to focal length f8 is 118, and the effective number of white points corresponding to focal length f9 is The number of points is 120. The selection module 202 can inquire from the curve that the number of effective white points corresponding to the focal length f5 is the least, and taking the focal length f5 as the target focal length, the focal length f5 is the point with the clearest focus.

Alternatively, the obtaining module 201 is specifically configured to: obtain the counted number of effective white points in the focus area corresponding to each focal length, and list each focal length and the corresponding number of effective white points into a correspondence table according to the statistical time order; select The module 202 is specifically configured to: query the focal length corresponding to the focus area with the least number of effective white points from the correspondence table, and use the focal length as the target focal length.

For example, refer to Table 2. Table 2 is a table of correspondence between focal lengths and the number of effective white points. The focal lengths are respectively f1, f2, f3, f4, f5, f6, f7, f8, and f9. The focal length f1 obtained by the acquisition module 201 The corresponding number of effective white points is 120, the number of effective white points corresponding to focal length f2 is 118, the number of effective white points corresponding to focal length f3 is 115, the number of effective white points corresponding to focal length f4 is 97, and the number of effective white points corresponding to focal length f5 is The number of effective white points is 86, the number of effective white points corresponding to focal length f6 is 97, the number of effective white points corresponding to focal length f7 is 115, the number of effective white points corresponding to focal length f8 is 118, and the effective number of white points corresponding to focal length f9 is The number of points is 120. The selection module 202 can find out from the correspondence table that the number of effective white points corresponding to the focal length f5 is the least, so the focal length f5 is taken as the target focal length, and the focal length f5 is the point with the clearest focus.

Table 2

According to the autofocus device provided by the embodiment of the present invention, the number of effective white points in the focus area corresponding to different focal lengths is obtained through the acquisition module 201 in the environment of dark light and point light source, and the pixel brightness value of the effective white point is greater than or equal to the preset brightness Threshold; the selection module 202 selects the focal length corresponding to the focal area with the least number of effective white points from different focal lengths as the target focal length; using the above-mentioned scheme, in a dark light environment, when taking pictures of point light sources, select from different focal lengths The focal length corresponding to the focus area with the least number of effective white points is the target focal length, and the focal length corresponding to the focus area with the fewest number of effective white points is the point with the clearest actual focus, which ensures the accuracy of focus and prevents out-of-focus phenomena , to improve user shooting experience.

Another embodiment also provides a mobile terminal, including the autofocus device in the second embodiment.

In another embodiment, a computer storage medium is also provided, and computer executable instructions are stored in the computer storage medium, and the computer executable instructions are used to execute the autofocus method in any one of the first embodiment.

Obviously, those skilled in the art should understand that each module or each step of the above-mentioned embodiments of the present invention can be realized by a general-purpose computing device, and they can be concentrated on a single computing device, or distributed across multiple computing devices. On the network, optionally, they can be implemented with program codes executable by a computing device, thereby, they can be stored in a storage medium (ROM/RAM, magnetic disk, optical disk) to be executed by a computing device, and in some In some cases, the steps shown or described may be performed in a different order than here, or they may be implemented as individual integrated circuit modules, or multiple modules or steps thereof may be implemented as a single integrated circuit module. Therefore, the present invention is not limited to any specific combination of hardware and software.

The above content is a further detailed description of the embodiments of the present invention in conjunction with specific implementation modes, and it cannot be assumed that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field of the present invention, without departing from the concept of the present invention, some simple deduction or replacement can be made, which should be regarded as belonging to the protection scope of the present invention.

Claims (10)

1. a kind of Atomatic focusing method, including：

Under half-light and spot light environment, effective white point number in focusing area corresponding to different focal is obtained, it is described effectively white The pixel brightness value of point is more than or equal to predetermined luminance threshold value；

The focal length corresponding to the minimum focusing area of effective white point number is selected from the different focal as target focal length.

2. Atomatic focusing method as claimed in claim 1, it is characterised in that the criterion of the effective white point includes：Often White point number of the individual white point in the neighborhood of its m*n pixel is more than or equal to the first predetermined number threshold value.

3. Atomatic focusing method as claimed in claim 1 or 2, it is characterised in that right corresponding to the acquisition different focal In burnt region before effective white point number, in addition to：Judge whether the current display picture of focusing area is spot light environment, wrap Include：

Focus, count effective white point number in focusing area corresponding to different focal；

In the case where effective white point number corresponding at least one focal length is more than the second setting amount threshold, then focusing area is judged The current display picture in domain is spot light environment.

4. Atomatic focusing method as claimed in claim 3, it is characterised in that

Described to focus, counting effective white point number in focusing area corresponding to different focal includes：According to focal length from greatly to Order small or from small to large focuses successively, counts effective white point number in focusing area corresponding to each focal length successively；

Effective white point number includes in focusing area corresponding to the acquisition different focal：It is corresponding to obtain each focal length counted on Focusing area in effective white point number, using focal length as abscissa, effective white point number as ordinate, according to statistics when Between order each focal length is subjected to described point with corresponding effective white point number in coordinate diagram, the time sequencing by each point according to statistics Connect into curve；

The focal length selected from the different focal corresponding to the minimum focusing area of effective white point number is as target Jiao Away from including：The minimum point of effective white point number is inquired about from the curve, using focal length corresponding to this is put as target focal length；

Or effective white point number includes in focusing area corresponding to the acquisition different focal：Obtain each Jiao counted on Away from effective white point number in corresponding focusing area, according to the time sequencing of statistics by each focal length and corresponding effective white point number Arrange into a mapping table；

The focal length selected from the different focal corresponding to the minimum focusing area of effective white point number is as target Jiao Away from including：The focal length corresponding to the minimum focusing area of effective white point number is inquired about from the mapping table, by the focal length As target focal length.

5. Atomatic focusing method as claimed in claim 2, it is characterised in that the predetermined luminance threshold value is 230, m*n 5* 5, the first predetermined number threshold value is 12.

6. a kind of automatic focusing mechanism, including：

Acquisition module, under half-light and spot light environment, obtaining effective white point in focusing area corresponding to different focal Number, the pixel brightness value of the effective white point are more than or equal to predetermined luminance threshold value；

Selecting module, for selecting the focal length corresponding to the minimum focusing area of effective white point number to make from the different focal For target focal length.

7. automatic focusing mechanism as claimed in claim 6, it is characterised in that the criterion of the effective white point includes：Often White point number of the individual white point in the neighborhood of its m*n pixel is more than or equal to the first predetermined number threshold value.

8. automatic focusing mechanism as claimed in claims 6 or 7, it is characterised in that also including judge module, for being obtained described In focusing area corresponding to modulus block acquisition different focal before effective white point number, judge that the current display picture of focusing area is No is spot light environment；

The judge module includes processing submodule and judging submodule, and the processing submodule is used to focus, and statistics is not With effective white point number in focusing area corresponding to focal length；The judging submodule is used for effective corresponding at least one focal length In the case that white point number is more than the second setting amount threshold, then it is spot light environment to judge the current display picture of focusing area.

9. automatic focusing mechanism as claimed in claim 8, it is characterised in that the processing submodule is specifically used for：According to Jiao Focus, count successively in focusing area corresponding to each focal length effectively successively away from order from big to small or from small to large White point number；

The acquisition module is specifically used for：Effective white point number in focusing area corresponding to each focal length counted on is obtained, Focal length as abscissa, effective white point number as ordinate, according to statistics time sequencing by each focal length with it is corresponding effectively White point number carries out described point in coordinate diagram, and each point is connected into curve according to the time sequencing of statistics；

The selecting module is specifically used for：The minimum point of effective white point number is inquired about from the curve, by this put corresponding to it is burnt Away from as target focal length；

Or the acquisition module is specifically used for：Obtain effective white point in focusing area corresponding to each focal length counted on Number, according to the time sequencing of statistics by each focal length and corresponding effective white point ordered series of numbers into a mapping table；

The selecting module is specifically used for：It is right that the minimum focusing area institute of effective white point number is inquired about from the mapping table The focal length answered, using the focal length as target focal length.

10. a kind of mobile terminal, including the automatic focusing mechanism as described in claim any one of 6-9.