JP2002116372A - Automatic focusing device, its focusing method, and computer-readable storage medium stored with program for performing the method by computer - Google Patents

Abstract

(57) [Problem] To provide an automatic focusing device capable of performing a focusing operation at high speed with a simple configuration. SOLUTION: A digital camera to which the automatic focusing device according to the present invention is applied includes auxiliary lenses 101B each having a different refractive index in two directions orthogonal to the optical axis direction and orthogonal to each other, and forms an object. A lens system for imaging, an AF area set in at least a part of the imaging area, a color image sensor 103 for converting a subject image formed by the lens system into image data, and a blur characteristic of the image data in the AF area And a distance direction calculator 111 for estimating the direction of the focal point and the distance to the focal point based on the size and vertical / horizontal difference of the point image, and determining whether or not the object is in focus. If it is determined that the subject is not in focus, the focus adjustment driving device moves the lens system or the color image sensor 103 by the distance to the focus in the direction of the estimated focus. Device 112.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an automatic focusing device,
Regarding the focusing method and a computer-readable recording medium storing a program for executing the method on a computer, in particular, video cameras, digital cameras and other image input devices using imaging devices The present invention relates to an automatic focusing device to be applied, a focusing method thereof, and a computer-readable recording medium storing a program for executing the method by a computer.

[0002]

2. Description of the Related Art With the intensification of the digital camera market in recent years, cost reduction has been required and reduction of the number of parts has become an important issue. In such an environment, a microprocessor (including a DSP) is one of the main components of a digital camera. However, recent microprocessors have achieved performance far exceeding the processing capability of a digital camera controller at a low price. . For this reason, for example, the function of a distance measuring module (AF sensor) component of a silver halide camera is
In a digital camera, an imaging system and digital signal processing tend to substitute. The main focus methods for digital cameras are the "hill climbing method" and the "correlation method."
The “hill climbing method” and the “correlation method” will be described.

In the focusing method based on the generally known “hill climbing method”, an AF evaluation value (calculated from a high frequency component of an image) at an image capturing position can be obtained. It is difficult to detect in which direction the focal point is located and at what distance the focal point is located. Therefore, in order to detect the in-focus position while avoiding the local maximum point, the AF evaluation value of the entire lens moving range is required. In addition, there is a problem that it takes time to obtain an accurate focus position.

The "correlation method" includes an autocorrelation method and a cross-correlation method. First, in the focusing method based on the autocorrelation method, two or more different light beams are imaged in one frame. However, while focus information can be obtained from a captured image of one frame, correlation based on the same data is obtained. Therefore, the result shows a very high peak value at the origin position (focal point) of the autocorrelation coefficient. Therefore,
Since the AF information is buried by the peak value near the focal point, it is difficult to detect the focal point near the focal point, and there is a problem that the focal point must be detected by another method near the focal point.

On the other hand, in the focusing method based on the cross-correlation method, 2
Although imaging is performed for each of the AF areas for two different light beams, it is necessary to prepare two image memories, but this does not cause a very high peak value at the origin position unlike the autocorrelation method. From this, focus information can be obtained from the vicinity of the focal point to the distance without being buried in this peak value. However, in the cross-correlation method, it is necessary to prepare two different light beams with an AF diaphragm to obtain focus information, and there is a problem that the AF diaphragm is not required at the time of photographing. In addition, the aperture plate for AF has a fixed opening size, and it is difficult to optimize the amount of light received by the image sensor.

[0006] A method of detecting a focal point using a point image distribution has also been proposed. For example, JP-A-05-0226
The "autofocus device" described in JP-A-43-
A focusing lens, an auxiliary lens having different refractive indices in two axes orthogonal to the optical axis, imaging means for imaging a subject via the focusing lens and the auxiliary lens, and an image signal output from the imaging means. A storage unit for storing, and among the image signals for one frame stored in the storage unit, image signals corresponding to two axes having different refractive indexes of the auxiliary lens are extracted, and a level difference between these image signals is detected. Position detecting means for detecting the position information of the focusing lens, and a lens drive control device for moving the focusing lens based on the position information detected by the position detecting means. That is, the "autofocus device" described in Japanese Patent Application Laid-Open No. 05-022643 uses a cylindrical lens as an auxiliary lens so that the position of the horizontal focal point and the position of the vertical focal point are different. Then, the difference between the horizontal high-frequency component and the vertical high-frequency component is detected to estimate the direction of the focal point.

Further, there has been proposed a method of detecting a focal point using chromatic aberration of subject light. For example, JP
An “autofocus device” described in Japanese Patent Application Laid-Open No. 6-138362 includes a lens having a predetermined chromatic aberration, an imaging unit that captures an image of a subject via the lens, and an amplitude of a color signal output from the imaging unit. Amplitude value detection means for detecting a value; focus position information detection means for detecting focus position information when the subject is imaged by the lens based on the detection result of the amplitude value detection means; The color signal is corrected by convolving the inverse function of the point spread function of the lens to reproduce the image of the subject formed on a virtual plane separated by a predetermined distance from the imaging plane used for imaging the color signal. Means for performing the operation. That is, the “autofocus device” described in Japanese Patent Application Laid-Open No. H06-138362 makes use of chromatic aberration of a focus lens so that the focal point of each of the RGB colors is different in the optical axis direction, so that the captured RGB image is obtained. The direction of the focal point is estimated from the magnitude relationship between the high-frequency components of each color.

[0008]

However, Japanese Patent Application Laid-Open No. 05-022643 and Japanese Patent Application Laid-Open No.
"Autofocus device" described in JP 8362
In, since the distance to the focal point is not detected, it is necessary to perform imaging for focusing many times before reaching the focal point. There is a problem that it takes time to obtain a focus position.

The present invention has been made in view of the above, and has an automatic focusing apparatus capable of performing a high-speed focusing operation with a simple configuration, a focusing method thereof, and a program for executing the method by a computer. It is an object of the present invention to provide a computer-readable recording medium in which is stored.

[0010]

In order to solve the above-mentioned problems, the invention according to claim 1 is to provide an auxiliary lens having different refractive indexes in two directions orthogonal to the optical axis direction and mutually orthogonal. A lens system for forming an image of a subject, an image sensor for setting an AF area in at least a part of an imaging area, and converting a subject image formed by the lens system into image data; A focus position estimating means for obtaining a point image distribution indicating a blur characteristic of the image data and estimating a direction of a focal point and a distance to the focal point based on a size and a vertical / horizontal difference of the point image; Based on the distance of the focal point estimated by the means, a focused state determining means for determining whether or not the in-focus state, and when it is determined that the in-focus state is not in the focused state, The focus position estimating means Been by the distance to the focus point in the direction of the focus point, in which and a driving means for moving the lens system or the image pickup device.

According to the above invention, the lens system includes the auxiliary lenses each having a different refractive index in each of two directions orthogonal to the optical axis direction and orthogonal to each other.
The imaging device has an AF area set in at least a part of the imaging area, converts a subject image formed by the lens system into image data, and the focus position estimating means indicates a blur characteristic of the image data in the AF area. The point image distribution is obtained, and the direction of the focal point and the distance to the focal point are estimated based on the size and vertical / horizontal difference of the point image. The in-focus state determining unit determines the focal point estimated by the in-focus position estimating unit. The drive means determines whether or not the camera is in focus on the basis of the distance. If the focus state determination means determines that the camera is not in focus, the drive means determines the in-focus state estimated by the focus position estimation means. The lens system or the image sensor is moved in the direction of and the distance to the focal point.

[0012] The invention according to claim 2 is based on claim 1.
In the invention according to the invention, the in-focus position estimating means converts the image data of the AF area into two-dimensional Fourier transform into amplitude and phase in a frequency domain, and replaces all phases in a frequency domain with zero. The point image distribution is calculated by performing an inverse Fourier transform. According to the above invention, the in-focus position estimating means converts the image data of the AF area into two-dimensional Fourier transform into amplitude and phase in the frequency domain, replaces all phases in the frequency domain with zero, and then performs two-dimensional inverse A point image distribution is calculated by performing a Fourier transform.

[0013] The invention according to claim 3 is based on claim 1.
Alternatively, in the invention according to claim 2, the in-focus position estimating means calculates a threshold based on an origin peak value of the point image distribution, and calculates an X-direction radius and a Y-direction radius of a cross section of the point image distribution based on the threshold. Is calculated as the vertical and horizontal difference of the point image. According to the above invention, the focus position estimating means calculates the threshold value based on the origin peak value of the point image distribution,
The difference between the X-direction radius and the Y-direction radius of the cross section of the point image distribution based on the threshold value is calculated as the vertical and horizontal difference of the point image.

[0014] The invention according to claim 4 is based on claim 1.
The image pickup device according to any one of claims 1 to 3, wherein the image pickup device comprises a color image pickup device, and the in-focus position estimating means comprises luminance information of color image data of an AF area output from the color image pickup device. Is used to calculate the point image distribution. In the above invention, the imaging element is
The focus position estimating means includes a color image sensor, and calculates a point image distribution based on luminance information of color image data in the AF area output from the color image sensor.

[0015] The invention according to claim 5 is based on claim 1.
In the invention according to any one of the first to fourth aspects, the auxiliary lens is orthogonal to the optical axis direction and orthogonal to each other.
The concave and convex lenses were cylindrical in shape and had mutually opposite refractive indices. According to the above invention, as the auxiliary lens, a columnar concave / convex lens having mutually opposite refractive indices in two directions orthogonal to the optical axis direction and orthogonal to each other is used.

The invention according to claim 6 is based on claim 1.
The invention according to any one of claims 1 to 5, further comprising an auxiliary lens driving unit for moving the auxiliary lens, wherein the auxiliary lens driving unit is configured to light the auxiliary lens in AF imaging. On the other hand, in normal imaging, the auxiliary lens is retracted from the optical path while being arranged on the road. According to the above-described invention, the auxiliary lens driving unit arranges the auxiliary lens on the optical path in AF imaging, while retracts the auxiliary lens from the optical path in normal imaging.

According to a seventh aspect of the present invention, there is provided a focusing method of an automatic focusing apparatus for performing an automatic focusing operation by moving a lens system or an image pickup device, wherein the two directions are orthogonal to the optical axis direction and orthogonal to each other. FIG. 4 shows a step of forming subject light by the lens system including auxiliary lenses having different refractive indexes, and a blur characteristic of image data of an AF area of a subject image formed on the image sensor. Estimating the point image distribution, estimating the direction of the focal point and the distance to the focal point based on the size and vertical / horizontal difference of the point image, and focusing on the basis of the estimated distance to the focal point. A focus determination step of determining whether or not there is, and in the focus determination step, when it is determined that the subject is not in focus, only the distance to the focus in the direction of the estimated focus, , The lens system The other is intended to include, a moving step of moving the imaging element.

According to the present invention, the lens system including the auxiliary lenses each having a different refractive index forms an image of the subject light, and the blur characteristics of the image data of the AF area of the subject image formed on the image sensor. Is obtained, the direction of the focal point and the distance to the focal point are estimated based on the size and vertical / horizontal difference of the point image, and the in-focus state is obtained based on the estimated distance to the focal point. Then, if it is determined that the subject is not in focus, the lens system or the imaging device is moved in the direction of the estimated focus by the distance to the focus.

According to an eighth aspect of the present invention, there is provided a focusing method for an automatic focusing device for performing an automatic focusing operation by moving a lens system or an image pickup device, wherein the two directions are orthogonal to the optical axis direction and orthogonal to each other. For arranging auxiliary lenses each having a different refractive index on the optical path, forming subject light by the lens system including the auxiliary lens, and forming a subject formed on the image sensor. Image AF
Find a point image distribution indicating the blur characteristics of the image data of the area,
An estimation step of estimating the direction of the focal point and the distance to the focal point based on the size and the vertical / horizontal difference of the point image, and determining whether the object is in focus based on the estimated distance to the focal point. In the in-focus determination step of determining, and in the in-focus determination step, when it is determined that the in-focus state is not in focus, only the distance to the in-focus point in the direction of the estimated in-focus point, the lens system or the A moving step of moving the image sensor, and in the focusing determination step, when it is determined that the in-focus state, the auxiliary lens is retracted from the optical path,
Performing a normal photographing.

According to the above invention, auxiliary lenses having different refractive indexes are arranged on the optical path in two directions orthogonal to the optical axis direction and orthogonal to each other, and the object light is controlled by the lens system including the auxiliary lens. Is obtained, and a point spread indicating the blur characteristics of the image data of the AF area of the subject image formed on the image sensor is obtained. Estimate the distance to the focal point, determine whether or not the in-focus state based on the estimated distance to the focal point, if it is determined that the in-focus state, if the estimated in-focus point In the direction, the lens system or the image sensor is moved by the distance to the focal point, and when it is determined that the lens is in focus, the auxiliary lens is retracted from the optical path,
Perform normal shooting.

The invention according to claim 9 is the invention according to claim 7.
Alternatively, in the invention according to claim 8, in the estimating step, the image data of the AF area is subjected to a two-dimensional Fourier transform to convert the image data into an amplitude and a phase in a frequency domain, and after replacing the phase in the entire frequency domain with zero, 2 The point image distribution is calculated by performing a dimensional inverse Fourier transform. According to the above invention, the image data in the AF area is subjected to two-dimensional Fourier transform to convert the image data into the amplitude and phase in the frequency domain, and the phases in all frequency domains are replaced with zero. Calculate the distribution.

According to a tenth aspect of the present invention, in the invention according to any one of the seventh to ninth aspects, in the estimating step, a threshold value is calculated based on an origin peak value of the point image distribution. The difference between the X-direction radius and the Y-direction radius of the cross section of the point image distribution based on the threshold value is calculated as the vertical and horizontal difference of the point image. According to the invention described above, a threshold value is calculated based on the peak value of the origin of the point image distribution, and the difference between the X-direction radius and the Y-direction radius of the cross section of the point image distribution based on the threshold value is calculated as
It is calculated as the vertical and horizontal difference of the point image.

The invention according to claim 11 is the invention according to any one of claims 7 to 10, wherein
The image sensor is a color image sensor, and in the estimating step, a point image distribution is calculated based on luminance information of color image data of an AF area output from the color image sensor. According to the above invention, the point image distribution is calculated based on the luminance information of the color image data of the AF area output from the color image sensor.

The invention according to claim 12 is the invention according to any one of claims 7 to 11, wherein
The auxiliary lens is a cylindrical concavo-convex lens having mutually opposite refractive indices in two directions orthogonal to the optical axis direction and orthogonal to each other. According to the above invention, as the auxiliary lens, a columnar concave / convex lens having mutually opposite refractive indices in two directions orthogonal to the optical axis direction and orthogonal to each other is used.

According to a thirteenth aspect of the present invention, a program for causing a computer to execute each step of the invention according to any one of the seventh to twelfth aspects is recorded. According to the above invention, by executing a program stored in a recording medium by a computer,
Each step of the invention described in any one of claims 7 to 12 is realized.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the accompanying drawings, a preferred embodiment in which an automatic focusing apparatus according to the present invention is applied to a digital camera will be described (Principle of the invention), (Digital camera of the present invention). Will be described in order.

(Principle of the Invention) First, the principle of the present invention is shown in FIG.
This will be described with reference to FIGS. FIG. 1 is an explanatory diagram for explaining the principle of the present invention, FIG. 2 is a diagram showing a configuration of an auxiliary lens,
3 is an explanatory diagram for explaining an AF area of the color image sensor, FIG. 4 is an explanatory diagram for explaining a method of determining a focus direction and a distance, and FIG. 5 is a diagram illustrating a relationship between a sensor position and a point image radius. FIG. 6 is a diagram for explaining the relationship between the sensor position and the vertical / horizontal difference of the point image.

FIG. 1 schematically shows a lens system and its luminous flux. A point shown in FIG.
Point B indicates a focus position, and point C indicates a front focus position. In the same figure, (A) shows a case where the light flux viewed from the vertical direction (Y direction) becomes the front focus (point C), and (B)
Indicates a case where the light flux viewed from the lateral direction (X direction) is the rear focus (point A).

In FIG. 1, reference numeral 101A denotes a focus lens, and 101B denotes an auxiliary lens. FIG. 2 shows FIG.
Of the auxiliary lens 101B is shown. Auxiliary lens 101
B are two directions (X) orthogonal to the optical axis direction and orthogonal to each other.
(Y-direction and Y-direction). Auxiliary lens 10
1B, the horizontal component (X-direction component) and the vertical component (Y component) at the current position of the focus lens 101A are provided.
The image data of the direction component) is different.

In FIG. 1, light incident from the left to the right passes through a focusing lens 101A and an auxiliary lens 101B, passes through an imaging stop (not shown), and is received by a color image sensor (not shown). In this case, what is required as the focus information is the imaging data of the area (AF area) to which the photographer wants to focus, and the data of all the frames is not necessary, and only the image data of the AF area is transferred.

FIG. 3 is a view showing an AF area of the color image sensor. As shown in FIG. 3, the AF area is set at the center position of the optical axis of the optical system in the frame of the color image sensor. Here, the case where the AF area is arranged at the center position of the frame is shown, but this AF area can be set arbitrarily. In the present invention, since the color image sensor is configured to enable random access of pixels, the transfer target is only the data of the AF area, and the transfer time is greatly reduced.

Thereafter, for the RGB image data separated for each color by the color filter of the color image sensor, a point spread coefficient of the image data of the AF area of each color is obtained. FIG. 4 is a diagram for explaining the determination of the direction of the focal point, and shows image data and the like when a perfectly circular subject is imaged at each lens position when the focus lens 101A is moved. In the figure, (A) shows a focus lens 101.
The image (luminance information) of the AF area when passing only A, (B) is the image (luminance information) of the AF area when passing through the focusing lens 101A and the auxiliary lens 101B, and (C) is the focusing lens 101A and Auxiliary lens 1
1B shows a point image distribution shape of an image (luminance information) when the image passes through 01B, and is in front focus (point A in FIG. 1), in focus (point B in FIG. 1), and after focus (point B in FIG. 1). (Point C).

As shown in FIG.
If there is no 1B, the image will be a circle in any of front focus, focus, and back focus. On the other hand, as shown in FIG. 3B, when the auxiliary lens 101B is provided, the shape becomes a horizontally long circle at the time of front focus, a circle at the time of focus, and a vertically long circle at the time of focus back.

FIG. 6 is a diagram showing the relationship between the sensor position and the vertical / horizontal difference (radius in X direction−radius in Y direction) of the point image. In the figure, the horizontal axis represents the color image sensor position (or lens position), and the vertical axis represents the vertical and horizontal difference of the point image. Focus lens 10
The luminous fluxes that have passed through 1A and the auxiliary lens 101B are shifted from the true in-focus position (the focal point only by the focusing lens) forward and backward between the light flux viewed from the vertical direction and the light flux viewed from the horizontal direction. Therefore, as described above, the point image distribution has a shape that is long in the vertical or horizontal direction except for the true focal point. Therefore, the point image distribution of the AF area image is obtained, and the direction (the front focus or the rear focus) with the focal point can be estimated from the vertical / horizontal difference of the point image radius (radius in the X direction−radius in the Y direction).

FIG. 5 is a diagram showing the relationship between the sensor position and the point image radius. In the figure, the horizontal axis indicates the color image sensor position (or lens position), and the vertical axis indicates the point image radius. As shown in the figure, the point image radius increases as the aperture opening diameter increases, and becomes minimum at the in-focus position. Further, the point image radius changes in size in proportion to the degree of stop.

Therefore, information on the aperture diameter of the stop and the distance of the light receiving surface of the stop surface, the point image radius R when the circle is approximated, and the distance from the vertical / horizontal difference (radius in the X direction−radius in the Y direction) of the point image radius to the distance from the vicinity of the focal point. Can be estimated.

(Digital Camera of the Present Invention) FIG. 7 shows a configuration diagram of an AF processing system of the digital camera according to the present embodiment. 7, the same parts as those in FIG. 1 are denoted by the same reference numerals. In the figure, reference numeral 101A denotes a focus lens for forming a subject image of a subject to be focused on the color image sensor 103. 10
Reference numeral 1B denotes an auxiliary lens.
01A is a lens for obtaining the moving direction and the moving amount of 01A,
This is a means for positively blurring the horizontal and vertical components of the subject image. Reference numeral 102 denotes an imaging stop, which is disposed behind the focus lens 101A and the auxiliary lens 101B, and serves to limit a light flux (light amount) passing through the focus lens 101A and the auxiliary lens 101B.

Reference numeral 103 denotes a color image sensor (primary color type) comprising a color CCD or the like which converts an image of a subject to be formed into an electric signal and outputs it as image data. The color image sensor 103 can perform random access of pixels, and can transfer image data of an arbitrary area in an image frame. These focus lens 101A, auxiliary lens 101B, imaging diaphragm 10
2, and the color image sensor 103 constitute an imaging optical system. An automatic exposure control unit 104 performs automatic exposure control by adjusting the aperture of the imaging aperture 102.

Reference numeral 115 denotes a brightness conversion unit for converting the captured image data into brightness information. Reference numeral 105 denotes an AF area image data memory that stores luminance information (image data) of an AF area in an image frame captured by the imaging for AF. Reference numeral 106 denotes an AF area image data memory 105
In the brightness information (image data) of the AF area stored in
5 shows a window function multiplication unit that multiplies a dimensional window function. 107 is
2 shows a two-dimensional FFT unit that performs two-dimensional Fourier transform on luminance information multiplied by a two-dimensional window function by a window function multiplication unit 106. 1
A phase operation unit 08 performs a phase operation on the data that has been Fourier transformed by the two-dimensional FFT unit 107. Reference numeral 109 denotes a two-dimensional IFFT for performing a two-dimensional inverse Fourier transform on the data subjected to the phase operation in the phase operation unit 108 to calculate a point spread coefficient.
Indicates a part.

Numeral 110 denotes a point spread coefficient memory for storing the point spread coefficients calculated by the two-dimensional IFFT unit 109. 111 is a color image sensor 103 based on the point spread coefficient stored in the point spread coefficient memory 110.
4 shows a distance direction calculation unit that calculates the direction and the distance to the in-focus position.

Reference numeral 112 denotes a focus adjustment driving device for moving the color image sensor 103 back and forth based on the calculation result of the distance direction calculation unit 111. Reference numeral 113 denotes a photographing device for switching a lens between AF and normal photographing. / AF switching device. Reference numeral 114 denotes a frame image memory in which image data for one frame that has been imaged is stored for each color in normal shooting.

Although the focus adjustment is performed by moving the color image sensor 103 in the optical axis direction, the focus adjustment is performed by moving the focus lens 101A instead of moving the color image sensor 103. A configuration for performing the operation may be adopted.

Next, the AF of the digital camera shown in FIG.
The operation and the photographing operation will be described with reference to FIGS. 11 to 16 in accordance with the flowcharts of FIGS. FIG. 8 is a flowchart for explaining the AF operation and the photographing operation, FIG. 9 is a flowchart for explaining the point image radius calculation processing of the AF operation in FIG. 8 in detail, and FIG. 10 is the AF in FIG.
4 is a flowchart for explaining in detail a focal direction and a focal length calculation process of the operation.

FIG. 11 is an explanatory view for explaining a two-dimensional Hamming window function, FIG. 12 is an explanatory view for explaining a point spread coefficient at the time of focusing, and FIG. 13 is an explanatory view of a point spread coefficient at the time of out-of-focus. FIG. 14 is an explanatory diagram for explaining a method of calculating a point image radius, and FIG. 15 is a focal length L at the time of back focus.
FIG. 16 is an explanatory diagram for explaining the focal length L at the time of front focus.

In the flow chart of FIG. 8, first, in the digital camera shown in FIG.
When a shutter button (not shown) is half-pressed, the imaging optical system of the digital camera operates as an AF sensor. Then, when the AF sensor is operating, the photographing / AF switching device 113 moves the auxiliary lens 101B and arranges it on the optical axis (step S101). Further, the exposure control unit 104 controls the exposure using the imaging stop 102 of the optical system so that the light amount of the subject incident on the image sensor from the outside is always optimized. In this state, photographing for AF is performed (step S102), and the subject image via the focus lens 101A and the auxiliary lens 101B is taken into the color image sensor 103, and the AF area on the color image sensor 103 (see FIG. 2) Is input to the luminance conversion unit 115. Brightness converter 11
5 converts the color image data in the AF area into luminance information and transfers the luminance information to the AF area image data memory 105;
Brightness information (image data) of the AF area is stored in the F area image data memory 105 (step S10).
3).

Next, a point image radius R is calculated based on the luminance information stored in the image memory 105 for the AF area.
(Steps S104 to S108). Here, the point image radius R
In the following, a method of calculating using the Fourier transform will be described.

First, the AF area image data memory 105
The point image distribution coefficient is calculated based on the image data of the AF area stored in. Specifically, the window function multiplication unit 106
Is the image data f of the AF area as shown in the following equation (1).
_In order to reduce the influence of high frequency components on the image boundary, ₀ (u, v) is multiplied by a two-dimensional window function w (u, v) such as a Hamming window as shown in FIG. 11 (step S10).
4).

F (u, v) = w (u, v) · f ₀ (u, v) (1) where w (u, v) = w (u) · w (v) w ( u) = 0.54 + 0.46 · cos (2πu / N) w (v) = 0.54 + 0.46 · cos (2πv / N) N: Image size

Next, the two-dimensional FFT unit 107
A two-dimensional discrete Fourier transform DFT (actually, a fast Fourier transform FFT is performed) is performed on (u, v) to obtain frequency domain data F (U, V) (step S105).

When the point spread coefficient in the frequency domain is a complex number H (U, V), the phase operation unit 108 calculates the image data in the frequency domain in order to obtain the H (U, V). Each phase of F (U, V) is replaced with zero (step S106). That is, as shown in the following equations (2) and (3), the amplitude of F (U, V) is set to the real part of H (U, V) and H (U, V).
The imaginary part of V) is set to zero.

Re {H (U, V)} = | F (U, V) | (2) Im {H (U, V)} = 0 (3) where | F (U , V) | = {[Re {F (U, V)} ² + Im
{F (U, V)} ² ]

The two-dimensional IFFT unit 109 performs a two-dimensional inverse discrete Fourier transform IDFT (actually, performs an inverse fast Fourier transform IFFT) on the result to obtain a point image distribution coefficient h (u, v). ) (Step S1)
07). Then, the calculated point spread coefficient h (u, v)
Are stored in the point spread coefficient memory 110.

Then, the distance direction calculation unit 111 calculates the point image radius R based on the point image distribution coefficient h (u, v) (step S108). Here, a specific method of calculating the point image radius R will be described with reference to the flowchart of FIG. The point spread coefficient h (u, v) shows a peak value at the origin. FIG. 11 shows an example of a point spread coefficient obtained from a focused image.
FIG. 12 shows an example of a point spread coefficient obtained from a focused image.
FIG. 13 shows an example of the point spread coefficient obtained from the blurred image.
As shown in FIGS. 11 and 12, the distribution of the point spread function of the focused image has an impulse shape, and the distribution of the point spread function of the blurred image has a gentle conical shape according to the degree of blur.

In FIG. 9, the origin peak value of, for example, an impulse shape or a conical shape is input (step S201).
A sectional threshold is calculated based on the peak value of the origin (step S202). For example, as shown in FIG. 14, the sectional area of the point spread coefficient obtained by slicing the point spread coefficient by the calculated sectional threshold (cross sectional pixel) Calculate S) (Step S20)
3). Specifically, as shown in FIG. 14A, the cross-sectional area S is calculated by counting the number of pixels corresponding to the cross-sectional portion. Also, at this time, the X direction radius and the Y direction radius of the point image are calculated by counting the number of pixels in the horizontal direction (X direction) and the vertical direction (Y direction) of the cross section.
In the example shown in the figure, the cross-sectional area S is “52”.
Then, a point image radius R is calculated by performing the calculation of the following equation (4) based on the calculated cross-sectional area S (step S20).
4) Output the calculated point image radius R (Step S20)
5). In the example shown in FIG. 14B, the point image radius R is “4”.
It has become.

R = √ (S / π) (4) where π: pi

Subsequently, in FIG. 8, after calculating the point image radius R for each color, the distance direction calculator 111 determines the focal direction and calculates the focal length L (step S10).
9). The method of determining the focal direction and calculating the focal length will be specifically described with reference to the flowchart of FIG. Here, the case where the focal position of the G color image is selected as the target focal length will be described.

The distance direction calculator 111 calculates the direction and distance to the focal point based on the size of the point image radius Rg of the G color image (luminance information) and the vertical / horizontal difference of the point image (the difference between the radius in the X direction and the radius in the Y direction). Is estimated.

Specifically, in FIG. 10, the vertical radius X of the point image, the horizontal radius Y of the point image, the point image radius Rg of the G color,
When the stop aperture Ro and the stop light receiving surface distance Lo are input (step S301), the size of the vertical radius X of the point image and the size of the horizontal radius Y of the point image are compared in order to obtain a focus position. (Step S302) If the vertical radius X of the point image is smaller than the horizontal radius Y of the point image, the process shifts to Step S303 to estimate the front focus. Then, the focal length L is defined as the aperture opening diameter Ro, the information on the aperture light receiving surface distance Lo, the point image radius Rg of the G color image, the vertical / horizontal difference of the point image (the vertical radius X of the point image−the horizontal radius Y of the point image Y). ), The focal length L (the distance to the focal point of the color G of the color image sensor 103) is calculated by the following equation (5) (step S306). FIG. 16 is a diagram illustrating an example of the focal length L at the time of front focus.

L = Lo · Rg / (Ro + Rg) + K (XY) (5) where K is a constant

In step S302, X = Y
In the case of, the process moves to step S304, and it is estimated that focus is achieved. Then, it is estimated that the focal length L = 0 (step S
307).

If it is determined in step S302 that the vertical radius X of the point image is larger than the horizontal radius Y of the point image, the process proceeds to step S305 to estimate the back focus. Then, the focal length L is defined as the aperture opening diameter Ro, the information on the aperture light receiving surface distance Lo, the point image radius Rg of the G color image, the vertical / horizontal difference of the point image (the vertical radius X of the point image−the horizontal radius Y of the point image Y). ), The focal length L (color image sensor 1)
The distance to the focal point of the 03 G color is calculated (step S308). FIG. 15 is a diagram illustrating an example of the focal length L at the time of back focus.

L = Lo · Rg / (Ro−Rg) + K (XY) (6) where K is a constant

Then, the calculated focal length L is output (step S309). Subsequently, the process proceeds to step S110 in FIG. 8, and the focus adjustment driving device 112 determines whether or not the subject is in focus based on the calculated focal length L (the light receiving position of the color image sensor 103 and the focus lens 1).
It is determined whether or not the focal point of the focal point 01A coincides.) If not, the color image sensor 103 (or the focal lens 101A) is moved to the focal position (the focal length L in the calculated focal position direction). After quickly moving (step S111), the process returns to step S102, and repeats the same AF process again to determine whether the camera has reached the true focus position (focused state). Is determined, and the same AF processing is performed until the focusing state is achieved (step S10).
2 to step S111) are repeated.

On the other hand, if it is determined in step S110 that the subject is in focus, the photographing / AF switching device 113 retracts the auxiliary lens 101B from the optical path (step S11).
2) The preparation for photographing the subject is completed, and a state where the shutter button is fully pressed is awaited. Thereafter, when the shutter button is fully pressed, the shutter is opened for a certain period of time in conjunction therewith, and light from the subject is received by the color image sensor 103. Then, the image data from the image sensor 103 is stored in each frame image memory (R /
G / B) 114, and these data are stored or displayed on a monitor after image processing such as white balance (step S113).

The number of AF operations is determined by the color image sensor 103 (or the focusing lens 101A).
In the case where the movement start position is near the in-focus position, the point spread coefficient shows a sharp peak as shown in FIG. The focus position is reached within the allowable range by the AF operation. On the other hand, when the movement start position of the color image sensor 103 (or the focus lens 101A) is far from the focus position, in order to obtain focus information from a blurred image,
The point spread coefficient shows a gradual peak as shown in FIG. 13, and reaches the allowable range of the focus position by a plurality of AF operations.

As described above, in the present embodiment, in imaging for AF, different refractive indexes are used in two directions (X direction and Y direction) orthogonal to the optical axis direction and orthogonal to each other. Image sensor 103 via a focusing lens 101A having an
A point image distribution indicating the blur characteristic of the image data of the AF area of the subject image formed above is obtained, and the focal point is determined based on the size of the point image and the vertical / horizontal difference (the difference between the radius in the X direction and the radius in the Y direction). The direction and the distance to the focal point are estimated, and it is determined whether or not the subject is in focus based on the estimated distance to the focal point,
When it is determined that the camera is not in focus, the lens system or the color image sensor 103 is moved in the direction of the estimated focus by the distance to the focus, while it is determined that the camera is in focus In addition, since the auxiliary lens 101B is retracted from the optical path and normal photographing is performed, it is possible to obtain information on the distance to the focal position and the direction only by performing imaging for one AF operation, and a simple configuration. And a high-speed focusing operation can be performed.

In this embodiment, the image data in the AF area is subjected to two-dimensional Fourier transform to convert the data into amplitude and phase in the frequency domain, and the phases in all frequency domains are replaced with zero. Since the point image distribution is calculated by performing the transformation, DFT (Discrete Fourier Transform) or FFT (Fast Fourier Transform) can be applied, which is suitable for a digital integrated circuit such as a DSP.

In the present embodiment, a threshold value is calculated based on the peak value of the origin of the point image distribution, and the difference between the X-direction radius and the Y-direction radius of the cross section of the point image distribution based on the threshold value is calculated.
Since the vertical and horizontal difference of the point image is calculated, the stereoscopic data of the point image distribution can be converted into plane data, and the amount of calculation for estimating the vertical and horizontal difference of the point image distribution can be reduced.

In this embodiment, the point image distribution is calculated based on the luminance information of the color image data in the AF area output from the color image sensor 103. Therefore, the point image distribution is obtained for each color. The AF operation can be performed with a smaller number of calculations than in the case.

In the present embodiment, as the auxiliary lens, cylindrical irregularities having mutually opposite refractive indexes in two directions (X direction and Y direction) orthogonal to the optical axis direction and mutually orthogonal. Since I decided to use a lens,
Auxiliary lenses having different refractive indexes in the directions (X direction and Y direction) can be realized with a simple configuration.

In the focusing method of the digital camera according to the above-described embodiment, a prepared program may be executed by a computer such as a personal computer or a workstation. This program includes a hard disk, floppy (registered trademark) disk, CD-RO
It is executed by being read from a computer-readable recording medium such as M, MO, and DVD. Further, this program can be distributed via the recording medium and as a transmission medium via a network such as the Internet.

It should be noted that the present invention is not limited to the above-described embodiment, but can be appropriately changed without changing the gist of the invention.

For example, in the above-described embodiment, a digital camera has been described as an example. However, in principle, the present invention provides information on the distance to the focus position and the direction to the in-focus position only once at an arbitrary focus lens position. Can be obtained, and can be used as a tracking servo. Therefore, the present invention can be applied to a digital video camera.

In the above-described embodiment, digital signal processing by two-dimensional discrete Fourier transform (DFT) or fast Fourier transform (FFT) is applied to obtain a point spread coefficient for focus control. However, these calculations may be performed by utilizing the surplus capacity of the camera controller processor or by providing a calculation circuit in an integrated circuit such as an IPP (Image Pre Processor).
For the window function, a part of w (u, v) may be stored as a table in order to save the calculation, and only the coefficient multiplication may be performed.

[0075]

As described above, according to the automatic focusing apparatus of the first aspect, the lens system has different refractive indexes in two directions orthogonal to the optical axis direction and orthogonal to each other. The image pickup device includes an auxiliary lens, forms an image of a subject, the image pickup device has an AF area set in at least a part of the image pickup area, converts a subject image formed by a lens system into image data, and A point image distribution indicating a blur characteristic of the image data of the AF area is obtained, and a direction of a focal point and a distance to the focal point are estimated based on the size and the vertical / horizontal difference of the point image. Based on the distance of the focal point estimated by the in-focus position estimating means, it is determined whether or not the camera is in focus, and when the driving means determines that the in-focus state is not in focus by the in-focus state determining means, In the direction of the focal point estimated by the focus position estimating means Distance to the focal point, so it was decided to move the lens system or the imaging device, a single AF
The information on the distance to the focal position and the direction can be obtained only by imaging for the purpose, and a high-speed focusing operation can be performed with a simple configuration.

According to the automatic focusing device of the second aspect, in the automatic focusing device of the first aspect, the focus position estimating means performs two-dimensional Fourier transform of the image data of the AF area to obtain a frequency domain. After converting the amplitude and the phase into zero and replacing the phase in the entire frequency domain with zero, a two-dimensional inverse Fourier transform is performed to calculate the point spread, so that in addition to the effect of the invention according to claim 1, , DFT (Discrete Fourier Transform) and FFT (Fast Fourier Transform)
Suitable for digital integrated circuits such as P.

According to a third aspect of the present invention, in the automatic focusing apparatus according to the first or second aspect, the in-focus position estimating means includes an origin peak value of the point image distribution. , And the difference between the X-direction radius and the Y-direction radius of the cross section of the point image distribution based on the threshold value is calculated as the vertical and horizontal difference of the point image. According to the above invention, the in-focus position estimating means calculates the threshold value based on the origin peak value of the point image distribution, and calculates the difference between the X direction radius and the Y direction radius of the cross section of the point image distribution based on the threshold value. 3. The method according to claim 1, wherein the difference is calculated as a vertical and horizontal difference between the images.
In addition to the effects of the present invention, the three-dimensional data of the point image distribution can be converted into plane data, and the amount of calculation for estimating the vertical and horizontal difference of the point image distribution can be reduced.

According to the automatic focusing apparatus of the fourth aspect, in the automatic focusing apparatus of any one of the first to third aspects, the image pickup device comprises a color image pickup device, and The invention according to any one of claims 1 to 3, wherein the position estimating means calculates the point spread based on the luminance information of the color image data of the AF area output from the color image sensor. In addition to the above-mentioned effect, the number of operations is smaller than the number of calculations in comparison with the case where a point image distribution is obtained for each color.
The F operation can be performed.

Further, according to the automatic focusing apparatus of the fifth aspect, in the automatic focusing apparatus of any one of the first to fourth aspects, as an auxiliary lens, the auxiliary lenses are orthogonal to the optical axis direction and are mutually orthogonal. Since cylindrical concave and convex lenses having different refractive indices are used for two orthogonal directions, in addition to the effect of the invention according to any one of claims 1 to 4, two directions are provided. However, auxiliary lenses having different refractive indexes can be realized with a simple configuration.

According to the automatic focusing apparatus of the sixth aspect, in the automatic focusing apparatus of any one of the first to fifth aspects, the auxiliary lens driving means is provided with an image pickup device for AF. Since the auxiliary lens is disposed on the optical path while the auxiliary lens is retracted from the optical path in normal imaging, in addition to the effect of the invention according to any one of claims 1 to 5, Imaging for AF and normal imaging can be performed.

Further, according to the focusing method of the automatic focusing apparatus according to the seventh aspect, the subject light is imaged by the lens system including the auxiliary lenses having different refractive indexes, and the image is formed on the image pickup device. The point image distribution indicating the blur characteristic of the image data of the AF area of the subject image to be obtained is obtained, and the direction of the focal point and the distance to the focal point are estimated based on the size and vertical / horizontal difference of the point image. It is determined whether or not the camera is in focus based on the distance to the focal point.If it is determined that the camera is not in focus, the lens is moved by the distance to the focal point in the estimated direction of the focal point. Since the system or the imaging element is moved, information on the distance and direction to the focal position can be obtained only by one imaging for AF, and a high-speed focusing operation can be performed with a simple configuration. It becomes possible.

Further, according to the focusing method of the automatic focusing apparatus according to the eighth aspect, the auxiliary lenses having different refractive indexes are provided on the optical path in two directions orthogonal to the optical axis direction and orthogonal to each other. With the lens system including the auxiliary lens
Obtains a point image distribution indicating the blur characteristics of image data of the AF area of the object image formed on the image sensor by imaging the object light, and determines the direction of the focal point based on the size and vertical / horizontal difference of the point image. And the distance to the in-focus point is estimated. Based on the estimated distance to the in-focus point, it is determined whether or not the subject is in focus. The lens system or the image sensor is moved by the distance to the focal point in the direction of the focal point. On the other hand, if it is determined that the lens is in a focused state, the auxiliary lens is retracted from the optical path to perform normal photographing. Therefore, it is possible to obtain information on the distance to the focus position and the direction only by performing imaging for one AF, and to perform a high-speed focusing operation with a simple configuration. It is also possible to perform normal shooting.

According to the focusing method of the automatic focusing apparatus according to the ninth aspect, in the focusing method of the automatic focusing apparatus according to the seventh or eighth aspect, the image data of the AF area is two-dimensionally Fourier-transformed. Claim 7 or Claim 7, in which the point image distribution is calculated by performing a two-dimensional inverse Fourier transform after converting the amplitude and phase in the frequency domain to zero and replacing the phase in all frequency domains with zero. In addition to the effects of the invention of FIG. 8, DFT (Discrete Fourier Transform) and FFT (Fast Fourier Transform) can be applied, and are suitable for digital integrated circuits such as DSP.

According to the focusing method of the automatic focusing apparatus according to the tenth aspect, in the focusing method of the automatic focusing apparatus according to any one of the seventh to ninth aspects, the point image distribution of the A threshold value is calculated based on the peak value of the origin, and a difference between a radius in the X direction and a radius in the Y direction of a cross section of the point image distribution based on the threshold value is calculated as a vertical and horizontal difference of the point image. The data can be converted into plane data, and the amount of calculation for estimating the vertical and horizontal difference of the point image distribution can be reduced.

Further, according to the focusing method of the automatic focusing device according to the eleventh aspect, any one of the seventh to tenth aspects.
In the focusing method of the automatic focusing device, the point image distribution is calculated based on the luminance information of the color image data in the AF area output from the color imaging device. In addition to the effect of the invention according to any one of the above, the AF operation can be performed with a smaller number of calculations than in the case where a point image distribution is obtained for each color.

Further, according to the focusing method of the automatic focusing device according to the twelfth aspect, any one of the seventh to eleventh aspects is provided.
In the focusing method of the automatic focusing device according to the first aspect, as the auxiliary lens, a cylindrical concave-convex lens having a refractive index opposite to each other in two directions orthogonal to the optical axis direction and mutually orthogonal to each other, Therefore, it is possible to realize auxiliary lenses having different refractive indexes in two directions with a simple configuration.

According to the computer-readable recording medium of the present invention, the computer executes a program stored in the recording medium to execute the program. Since each step of the invention of the present invention is realized, it is possible to obtain information on the distance and direction to the focus position only by one imaging for AF, and to perform a high-speed focusing operation with a simple configuration. Becomes possible.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining the principle of the present invention.

FIG. 2 is a diagram illustrating a configuration of an auxiliary lens.

FIG. 3 is an explanatory diagram for explaining an AF area of a color image sensor.

FIG. 4 is an explanatory diagram for explaining a method of determining the direction and distance of a focal point.

FIG. 5 is a diagram for explaining a relationship between a sensor position and a point image radius.

FIG. 6 is a diagram for explaining a relationship between a sensor position and a vertical / horizontal difference of a point image.

FIG. 7 is a configuration diagram of an AF processing system of the digital camera according to the present invention.

FIG. 8 is a flowchart illustrating an AF operation and a photographing operation.

FIG. 9 is a flowchart for explaining in detail a point image radius calculation process of the AF operation in FIG. 8;

FIG. 10 is a flowchart for explaining in detail a focal length direction calculation process of the AF operation in FIG. 8;

FIG. 11 is an explanatory diagram for explaining a two-dimensional Hamming window function.

FIG. 12 is an explanatory diagram for explaining a point spread coefficient at the time of focusing.

FIG. 13 is an explanatory diagram for explaining a point spread coefficient at the time of out-of-focus.

FIG. 14 is an explanatory diagram for describing a method of calculating a point image radius.

FIG. 15 is an explanatory diagram for explaining a focal length L at the time of back focus.

FIG. 16 is an explanatory diagram for explaining a focal length L at the time of front focus.

[Explanation of symbols]

 Reference Signs List 101A Focus lens 101B Auxiliary lens 101 Shooting and AF lens 102 Imaging aperture 103 Color image sensor 104 Automatic exposure control unit 105 AF area image data memory 106 Window function multiplication unit 107 2D FFT unit 108 Phase operation unit 109 2D IFFT unit 110 Point image distribution coefficient memory 111 Distance direction calculation unit 112 Focus adjustment driving device 113 Photographing / AF switching device 114 Frame image memory 115 Luminance conversion unit

Claims (13)

[Claims] 1. An optical system which is orthogonal to the optical axis direction and orthogonal to each other.
A lens system for forming an image of a subject, including an auxiliary lens having a different refractive index for each direction, and an AF area set in at least a part of an imaging area;
An image sensor for converting a subject image formed by the lens system into image data; and a point image distribution indicating a blur characteristic of the image data in the AF area, and obtaining a point image distribution based on a size and a vertical / horizontal difference of the point image. A focus position estimating means for estimating a focus direction and a distance to a focal point; and a focus for judging whether or not the subject is in focus, based on the distance of the focal point estimated by the focus position estimating means. State determining means, and when the in-focus state determining means determines that the lens is not in focus, the lens is moved by the distance to the in-focus point in the direction of the in-focus point estimated by the in-focus position estimating means. And a driving means for moving the system or the image pickup device. 2. The in-focus position estimating means converts the image data in the AF area into two-dimensional Fourier transform into amplitude and phase in a frequency domain, and replaces all phases in a frequency domain with zero. 2. The automatic focusing apparatus according to claim 1, wherein a point image distribution is calculated by performing an inverse Fourier transform. 3. The in-focus position estimating means calculates a threshold based on an origin peak value of the point image distribution,
The automatic focusing device according to claim 1, wherein a difference between a radius in the X direction and a radius in the Y direction of a cross section of the point image distribution based on the threshold value is calculated as a vertical and horizontal difference of the point image. 4. The image pickup device comprises a color image pickup device, and the focus position estimating means calculates a point image distribution based on luminance information of color image data of an AF area output from the color image pickup device. The automatic focusing device according to claim 1, wherein: 5. The auxiliary lens according to claim 1, wherein the auxiliary lens is a cylindrical concave / convex lens having mutually opposite refractive indices in two directions orthogonal to the optical axis direction and orthogonal to each other. Item 5. The automatic focusing device according to any one of Items 4. 6. An auxiliary lens driving unit for moving the auxiliary lens, wherein the auxiliary lens driving unit arranges the auxiliary lens on an optical path for imaging for AF, and performs normal imaging. 6. The automatic focusing device according to claim 1, wherein the auxiliary lens is retracted from an optical path. 7. A focusing method of an automatic focusing device for performing an automatic focusing operation by moving a lens system or an image pickup device, comprising:
Forming an image of a subject by the lens system including auxiliary lenses each having a different refractive index; obtaining a point image distribution indicating a blur characteristic of image data of an AF area of the subject image formed on the image sensor; An estimation step of estimating the direction of the focal point and the distance to the focal point based on the size and vertical / horizontal difference of the point image; and determining whether the object is in focus based on the estimated distance to the focal point. In the focusing determination step of determining, and in the focusing determination step, when it is determined that it is not in focus, by the distance to the focus in the direction of the estimated focus, the lens system or A focusing step of the automatic focusing device, comprising: a moving step of moving the imaging element. 8. A focusing method of an automatic focusing device for performing an automatic focusing operation by moving a lens system or an image sensor, wherein two directions orthogonal to an optical axis direction and orthogonal to each other are provided.
Arranging auxiliary lenses each having a different refractive index on an optical path; forming an image of a subject by the lens system including the auxiliary lens; and forming an AF area of the subject image formed on the image sensor. Estimating the point image distribution indicating the blur characteristics of the image data, based on the size and the vertical and horizontal difference of the point image, an estimation step of estimating the direction of the focal point and the distance to the focal point, and up to the estimated focal point A focus determining step of determining whether or not the subject is in focus based on the distance of the subject; and in the focusing determining step, when it is determined that the subject is not in focus, the estimated direction of the focus is determined. A moving step of moving the lens system or the imaging element by a distance to the focal point; and, if it is determined in the focusing step that the auxiliary lens is on the optical path, Are retracted, the focusing method of an automatic focusing device which comprises the steps of performing a normal photographing, the. 9. In the estimating step, two-dimensional Fourier transform is performed on the image data of the AF area to convert the image data into an amplitude and a phase in a frequency domain. 9. A focusing method for an automatic focusing device according to claim 7, wherein the point image distribution is calculated by performing the following. 10. In the estimating step, a threshold value is calculated based on an origin peak value of the point image distribution,
The difference between the X-direction radius and the Y-direction radius of the cross section of the point image distribution based on the threshold value is calculated as the vertical and horizontal difference of the point image. Focusing method for automatic focusing device. 11. The image pickup device comprises a color image pickup device, and in the estimating step, a point image distribution is calculated based on luminance information of color image data of an AF area output from the color image pickup device. The focusing method of the automatic focusing device according to any one of claims 7 to 10. 12. The auxiliary lens according to claim 7, wherein the auxiliary lens is a columnar concave / convex lens having reciprocal refractive indices in two directions orthogonal to the optical axis direction and orthogonal to each other. Item 12. The focusing method of the automatic focusing device according to any one of items 11. 13. A computer-readable recording medium on which is recorded a program for causing a computer to execute the steps of any one of claims 7 to 12.