JP2005345877A - Focus-detecting device and focus-detecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make the detecting of a focus to be performed appropriately in photographing in dark environment. <P>SOLUTION: In an arithmetic processing circuit 7, the brightness of an image obtained by an imaging device 2 via a photographic lens 1 is detected according to the positions of the photographing lens 1 and a focusing position being the position of the photographing lens 1, when the image of an object which is displayed in the image is focused, is detected based on the minimum dot of the brightness. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an automatic focusing technique used in an imaging apparatus, and more particularly to an automatic focusing technique in imaging in a dark environment such as night scene photography.

  As one of conventional automatic focusing methods in an imaging apparatus, there is a contrast detection method. This is because an imaging device using an imaging device obtains a high-frequency component amount (contrast value) of a subject indicating the degree of focusing based on a video signal when the focusing lens is extended or retracted, and the value There is a system in which the position where the peak is (maximum contrast position) is determined as the in-focus position, and the focusing lens is driven to that position. This focusing method is also called “mountain climbing method” or the like, and is described in detail in Non-Patent Document 1, for example.

The automatic focusing by this contrast detection method will be further described with reference to FIG.
6A is a flowchart showing the processing procedure of the contrast detection method, and FIG. 6B is a diagram showing an example of the relationship between the lens position and the AF evaluation value in this processing. The horizontal axis in (b) indicates the lens position, and the change in the position of the focusing lens when the focal point is changed from the infinity side to the close side is the change from the left to the right in FIG. Become. Further, the AF (Auto Focus) evaluation value on the vertical axis in (b) is an integral value of the above-described contrast value over the entire captured image area to be automatically focused, and the contrast is higher toward the upper side in FIG. Is shown.

  In FIG. 6A, first, a direction determination process is performed in S1001. This process obtains the tendency of increase / decrease of the contrast value when the focusing lens is moved so that the focal point moves toward the infinity side or the near side, and the contrast value shows an increasing tendency at this time. This is a process for determining the moving direction of the focusing lens. In the example of FIG. 6B, it is determined that the moving direction of the focusing lens in which the AF evaluation value increases at the position (1) is the near side direction indicated by the solid line arrow.

  In the subsequent S1002, focus position excess determination processing is performed. In this process, when the focusing lens is moved in the movement direction according to the determination result of the above-described movement direction determination process, it is determined that the increase / decrease tendency of the contrast value has changed from an increase tendency to a decrease tendency, This is a process of detecting the position of the focusing lens when this tendency changes as the focusing position. In the example of FIG. 6B, since the AF evaluation value for the lens position changes as indicated by the arrow in (2), it is detected that the AF evaluation value has changed from an increasing trend to a decreasing trend. Then, it is determined that the in-focus position of the focusing lens is exceeded, and the in-focus position is detected.

  In S1003, focus position return processing is performed. In this process, the focusing lens is moved in the reverse direction to return to the focus position detected by the above-described focus position determination process. In the example of FIG. 6B, as indicated by the arrow in (3), the focusing lens is returned to the position where the AF evaluation value is maximized, so that the focusing lens is moved to the focusing position. Placed in.

A method for performing automatic focusing as described above is a contrast detection method.
By the way, the focus detection by the above-described contrast detection method may not be sufficiently focused when shooting in a dark environment such as a night view. This case will be described.
FIG. 7 shows an image of a point light source. FIG. 7A shows an image of the point light source when not focused, and FIG. 7B shows an image of the point light source when focused. A white frame shown in these images is an AF area (an area in an image including a subject to be focused automatically).

  In the point light source image at the time of out-of-focus as shown in (a), there is a luminance change in a wide range in the AF area, so the total amount of high-frequency components (that is, AF evaluation values) in the entire AF area is large. . On the other hand, in the point light source image at the time of focusing as shown in (a), the luminance change exists in the AF area only in a very narrow range. Therefore, the total amount of high-frequency components in the entire AF area is This is rather less than in (a). That is, the change in the AF evaluation value with respect to the change in the focusing lens position in such a case is as shown by the solid curve in FIG. 8, so that even if the focusing lens is located at the focusing position, AF The evaluation value will not be the maximum. As a result, focusing becomes inappropriate.

  Incidentally, in FIG. 8, the change of the value value in the entire AF area with respect to the change of the focusing lens position in the case where the subject is a point light source is also shown by a dashed line curve. When the focusing lens is positioned at the in-focus position, the brightness of the subject image itself is increased, but the blur of the subject image is reduced due to focusing, so the proportion of the area occupied by the subject image in the AF area is reduced. The value value in the entire AF area exhibits a local minimum at that position, as shown by this curve.

Several techniques have been proposed in the past for enabling focus detection in the contrast detection method to be performed appropriately even in shooting in such a dark environment.
For example, in Patent Document 1, it is considered that night scene shooting is performed when the aperture is in an open state and the focal length of the photographing lens is set to the vicinity of the wide end during low-luminance photographing. A technique for automatically fixing the distance to infinity is disclosed.

Further, for example, in Patent Document 2, in the case of low-luminance shooting, if the in-focus position cannot be detected by detecting the in-focus position with proper exposure, the in-focus position is detected with an exposure amount lower than the appropriate exposure. Subsequently, a technique is disclosed in which focus position detection is repeated while gradually reducing the exposure amount until the focus position is detected.
JP-A-9-179014 JP 2002-196220 A NHK Technical Research Report, 1965, Vol. 17, No. 1, Total No. 86, p. 21-37

Since the technique disclosed in Patent Document 1 described above automatically fixes the focal length of the photographing lens to infinity, a subject image represented in an image obtained by photographing a subject near the imaging device. Can be out of focus.
Further, since the technique disclosed in Patent Document 2 listed above repeatedly detects the focus position while gradually reducing the exposure amount, it may take a considerable amount of time to detect the focus position. It is done. For this reason, it is considered that the vibration of the imaging device (for example, the shaking of the hand of the user holding the imaging device) during the detection of the in-focus position may be affected.

  The present invention has been made in view of the above-described problems, and a problem to be solved is to appropriately perform focus detection in photographing in a dark environment.

  A focus detection apparatus according to one aspect of the present invention includes a brightness detection unit that detects the brightness of an image obtained through a photographing lens according to the position of the photographing lens, and a subject image represented by the image. And a focus detection means for detecting a focus position, which is the position when the lens is in focus, based on the minimum point of the brightness. Solve.

In the focus detection apparatus according to the present invention described above, the focus detection unit may be configured to calculate the minimum point by an interpolation calculation based on the detection result of the brightness detection unit.
According to another aspect of the present invention, a focus detection apparatus includes a brightness detection unit that detects the brightness of an image obtained through a photographing lens according to the position of the photographing lens, and the contrast of the image. Contrast detection means for detecting according to the position, comparison means for comparing the brightness of the image with a predetermined brightness, brightness of the image selected according to the result of the comparison, and contrast of the image Focusing detection means for detecting a focusing position, which is the position when the subject image represented in the image is focused, based on any one of them, This feature solves the aforementioned problems.

  In the above-described focus detection device according to the present invention, the focus detection unit determines the maximum point of the contrast of the image when the brightness of the image is higher than the predetermined brightness according to the comparison result. The focus position is detected based on the image, and when the brightness of the image is darker than the predetermined brightness, the focus position is detected based on a minimum point of the brightness of the image. Also good.

At this time, the focus detection unit may be configured to calculate the minimum point by an interpolation calculation based on the detection result of the brightness detection unit.
According to another aspect of the present invention, a focus detection apparatus includes a brightness detection unit configured to detect brightness of an image obtained via a photographing lens according to a position of the photographing lens, and contrast of the image. Contrast detection means for detecting the image according to the position, and an interval between the position of the photographing lens when the brightness of the image is minimized and the position of the photographing lens when the contrast of the image is maximized. In-focus, which is the position of the photographing lens when the subject image represented in the image is in focus, based on at least one of the brightness of the image and the contrast of the image Detecting means, and the above-described problems are solved by this feature.

In the above-described focus detection device according to the present invention, the focus detection unit is configured to detect the focus position based on the minimum point of the brightness of the image when the interval is longer than a predetermined interval. You may comprise so that it may detect.
At this time, when the interval is closer than the predetermined interval and the brightness of the image is darker than the predetermined brightness, the focus detection unit is configured to minimize the brightness of the image. The in-focus position may be detected based on the above.

In the above-described focus detection device according to the present invention, the focus detection unit detects the focus position based on the maximum point of contrast of the image when the interval is closer than a predetermined interval. You may comprise as follows.
The focus detection unit described above may be configured to calculate the minimum point by an interpolation calculation based on the detection result of the brightness detection unit.

  According to still another aspect of the present invention, a focus detection device includes an acquisition unit that acquires an instruction of an operation mode, and detects the brightness of an image obtained through the photographing lens according to the position of the photographing lens. Brightness detection means for detecting, contrast detection means for detecting the contrast of the image according to the position, and when the acquisition means acquires an instruction of an operation mode suitable for night scene shooting, Focusing detection means for detecting a focusing position that is a position of the photographing lens when a subject image represented in the image is focused based on at least one of the contrasts of the image. The above-described problems are solved by this feature.

In the focus detection apparatus according to the present invention described above, the focus detection unit is configured to detect the focus based on a minimum point of the brightness of the image calculated by an interpolation calculation based on the detection result of the brightness detection unit. You may comprise so that a focal position may be detected.
According to another aspect of the present invention, a focus detection method detects the brightness of an image obtained through a photographic lens in accordance with the position of the photographic lens, and a subject image represented in the image is detected. The in-focus position, which is the position at the time of focusing, is detected based on the minimum point of the brightness, and the above-described problems are solved by this characteristic.

  According to another aspect of the present invention, a focus detection method detects the brightness of an image obtained through a photographing lens according to the position of the photographing lens, and determines the contrast of the image according to the position. And comparing the brightness of the image with a predetermined brightness, and based on one of the brightness of the image and the contrast of the image selected according to the result of the comparison, The present invention is characterized in that an in-focus position, which is the position when the subject image represented in the image is in focus, is detected, and the above-described problem is solved by this feature.

  According to another aspect of the present invention, a focus detection method detects the brightness of an image obtained through a photographing lens according to the position of the photographing lens, and determines the contrast of the image according to the position. The distance between the position of the photographing lens when the brightness of the image is minimized and the position of the photographing lens when the contrast of the image is maximized, the brightness of the image, and the image A focusing position that is a position of the photographing lens when the subject image represented in the image is focused is detected based on at least one of the contrasts of The above-mentioned problems are solved by the characteristics.

  As described above, the present invention has the above-described characteristics, and thus has an effect that the focus detection can be appropriately performed in photographing in a dark environment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the configuration of an imaging apparatus equipped with a focus detection apparatus for carrying out the present invention.
As shown in the figure, this apparatus mainly uses a lens driving motor 8, a photographing lens 1 driven by the lens driving motor 8, and a subject image formed on the light receiving surface via the photographing lens 1 as an electric signal. An image pickup device 2 for converting into (image pickup signal), an image pickup processing circuit 3 for performing amplification and sample hold of the image pickup signal, A / D conversion, luminance / color conversion processing, and the like, and a video signal in each block constituting this apparatus An SG (Signal Generator) circuit (pulse generation circuit) 4 for generating reference signals (various pulses such as horizontal and vertical synchronization signals) necessary for processing and a video signal output from the imaging processing circuit 3 are not shown. An output terminal unit 5 that outputs to a video recording / reproducing system, and a BPF circuit (band pass filter) that extracts a high-frequency component for evaluating the degree of focusing from a luminance signal among video signals output from the imaging processing circuit 3 6), a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a timer for timing, and the like. And an arithmetic processing circuit 7 for managing the operation of the entire apparatus and a motor drive circuit 9 for controlling the driving of the lens drive motor 8.

  In the imaging apparatus of FIG. 1 configured as described above, first, subject light is captured through the imaging lens 1 and formed on the light receiving surface of the imaging device 2 as a subject image. The image pickup signal output from the image pickup device 2 is subjected to signal amplification, sample hold, A / D conversion, luminance / color conversion processing, and the like in the image pickup processing circuit 3, and then the output terminal unit 5, the BPF circuit 6, And output to the arithmetic processing circuit 7. Among these, the video signal sent to the output terminal unit 5 is then output to a video recording / reproducing system circuit.

In the BPF circuit 6, a high frequency component is extracted from the luminance (Y) signal of the video signal sent from the imaging processing circuit 3. The amount of the high frequency component extracted here is the contrast value.
The arithmetic processing circuit 7 performs photometry (AE) processing by obtaining an integral value (AE evaluation value) of a luminance (Y) signal in the video signal directly transmitted from the imaging processing circuit 3. Further, white balance (WB) processing is performed based on the color (C) signal of the video signal.

  The arithmetic processing circuit 7 integrates the contrast value extracted by the BPF circuit 6 and performs an automatic focusing (AF) process based on the obtained integrated value (AF evaluation value). Here, it is possible to limit the range (AF area) of the captured image to be integrated using the vertical synchronization signal (VD) and the horizontal synchronization signal (HD), or to change the position of the range. In addition, a plurality of ranges to be integrated can be set in the captured image.

Note that, by using the same method as described above, it is possible to limit the range of captured images to be subjected to AE processing or WB processing, to change the position, and to set a plurality of settings. VD and HD are respectively connected to CPU interrupt terminals of the arithmetic processing circuit 7 and are used for processing of AF, AE, WB, and the like.
In addition to this, the arithmetic processing circuit 7 performs in-focus determination and management of the position of the photographing lens 1, and in addition to detecting the in-focus position, drives the lens driving motor 8 via the motor drive circuit 9 during AF processing. Then, control for moving the photographing lens 1 to a predetermined position, control of an element shutter for changing the accumulation integration time of the image sensor 2 according to the result of AE processing, and the like are also performed.

Next, control processing performed by the CPU included in the arithmetic processing circuit 7 will be described. The CPU can execute these control processes by reading and executing the control program stored in advance in the ROM of the arithmetic processing circuit 7.
First, FIG. 2 will be described. This figure is a flowchart showing the processing contents of the first example of the automatic focusing control processing. This process enables automatic focusing suitable for the imaging apparatus of FIG. 1 when it is known in advance that the subject can be regarded as a point light source.

The processing in FIG. 2 is started, for example, when an automatic focusing instruction from the user by a half-press operation of a release button (not shown) is detected.
When this process is started in S101, first, in S102, the luminance value of the entire image represented by the video signal output from the image sensor 2 at this time is measured (the photometric process described above). To determine whether or not the luminance value (measurement BV (Brightness Value) value) is equal to or less than a preset value (reference BV value). Here, when it is determined that the measured BV value is equal to or less than the reference BV value (when the determination result is Yes), the process proceeds to S103. On the other hand, when it is determined that the measured BV value is larger than the reference BV value (when the determination result is No), the process proceeds to S105.

In S103 and S104, a process for automatically focusing a subject that is a point light source in a dark shooting environment (a shooting environment in which the brightness of an image obtained by the image sensor 2 is darker than a predetermined brightness) is performed. Is called.
That is, in S103, an instruction is given to the motor drive circuit 9 to operate the lens driving motor 8, and the photographing lens 1 is moved in the same manner as the processing of S1001 and S1002 in FIG. However, in the in-focus position determination process in S1002, the change of the AE evaluation value is observed instead of the AF evaluation value, and the position of the photographing lens 1 when the AE evaluation value becomes minimum is detected. The position detected at this time is defined as AE_step.

In subsequent S104, the motor drive circuit 9 is further instructed to operate the lens drive motor 8, and the photographing lens 1 is moved to the position of AE_step. Thereafter, in S107, the automatic focusing control process is completed.
Here, FIG. 3 will be described. This figure shows an example of changes in the AE evaluation value and the AF evaluation value with respect to the change in the focusing lens position when the subject is a point light source in a dark photographing environment. As can be seen from the figure, under such conditions, the position of the photographic lens 1 when the AE evaluation value is minimized is the proper in-focus position.

On the other hand, the processing in S105 and S106 in FIG. 2 is processing for automatic focusing on a subject that is a point light source in a bright photographing environment. In this case, automatic focusing according to the prior art, that is, AF evaluation value is obtained. Based on automatic focusing.
That is, in S105, an instruction is given to the motor drive circuit 9 to operate the lens drive motor 8, and the photographing lens 1 is moved in the same manner as the processing of S1001 and S1002 in FIG. The position of the photographic lens 1 is detected. Then, the position detected at this time is referred to as AF_step.

In the subsequent S106, further instructions are given to the motor drive circuit 9 to operate the lens drive motor 8, and the photographing lens 1 is moved to the position of the AF_step. Thereafter, in S107, the automatic focusing control process is completed.
The above processing is the first example of the automatic focusing control processing. This processing is performed by the CPU of the arithmetic processing circuit 7 so that the image pickup apparatus in FIG. 1 can perform automatic focusing. In particular, automatic focusing in a dark environment is appropriate for a subject that is a point light source. It will be a thing.

Next, FIG. 4 will be described. This figure is a flowchart showing the processing contents of the second example of the automatic focusing control processing. In this process, the CPU determines whether or not the subject can be regarded as a point light source, and enables appropriate automatic focusing according to the determination result in the imaging apparatus of FIG.
Note that the processing of FIG. 4 is also started, for example, when an automatic focusing instruction from the user by a half-press operation of a release button (not shown) is detected.

  When this process is started in S201, first, in S202, the luminance value of the image represented by the video signal output from the image sensor 2 at this time is measured, and this luminance value (measured BV value) is measured. ) Is performed to determine whether the value is equal to or less than the reference BV value. Here, when it is determined that the measured BV value is equal to or less than the reference BV value (when the determination result is Yes), the process proceeds to S203. On the other hand, when it is determined that the measured BV value is larger than the reference BV value (when the determination result is No), the process proceeds to S207.

  In S203, the same processing as S105 in the first example shown in FIG. 2 is performed. That is, when an instruction is given to the motor drive circuit 9 to operate the lens driving motor 8 and the photographing lens 1 is moved in the same manner as the processing of S1001 and S1002 in FIG. 6A, the AF evaluation value becomes maximum. The position of the taking lens 1 is detected. Then, the position detected at this time is referred to as AF_step.

  In subsequent S204, processing similar to that in S103 in the first example shown in FIG. 2 is performed. That is, an instruction is given to the motor drive circuit 9 to operate the lens drive motor 8, and the photographing lens 1 is moved in the same manner as the processing of S1001 and S1002 in FIG. , The change of the AE evaluation value is observed instead of the AF evaluation value, and the position of the photographing lens 1 when the AE evaluation value becomes minimum is detected. The position detected at this time is defined as AE_step.

  In S205, a process for determining whether or not the absolute value obtained by subtracting AE_step from AF_step, that is, the distance between AF_step and AE_step is equal to or greater than a preset distance TH_step is performed. Here, when it is determined that the distance between AF_step and AE_step is greater than or equal to TH_step (when the determination result is Yes), the process proceeds to S206, and when it is determined that the distance does not satisfy TH_step (the determination result is No). When), the process proceeds to S208.

  The determination processing in S205 is for determining whether or not the subject can be regarded as a point light source. When the subject is a point light source in a dark environment, as shown in FIG. 5, the lens position when the AF evaluation value is maximum and the lens position when the AE evaluation value is minimum are far apart. ing. On the other hand, when the subject is not a point light source in a dark environment, the lens position when the AF evaluation value is maximized and the lens position when the AE evaluation value is minimal are essentially the same. Therefore, it is possible to determine whether or not the subject can be regarded as a point light source by determining whether or not the distance between the two lens positions is separated or close based on the threshold value TH_step.

In S206, the same processing as S104 in the first example shown in FIG. 2 is performed. Further instructions are given to the motor drive circuit 9 to operate the lens drive motor 8, and the photographing lens 1 is moved to the position of AE_step. Thereafter, in S209, the automatic focusing control process is completed.
On the other hand, in S207 and S208, processing similar to S105 and S106 in the first example shown in FIG. 2, that is, processing for automatic focusing in a bright environment with respect to a subject that is a point light source is performed.

That is, in S207, an instruction is given to the motor drive circuit 9 to operate the lens drive motor 8, and the photographing lens 1 is moved in the same manner as the processing of S1001 and S1002 in FIG. The position of the photographic lens 1 is detected. Then, the position detected at this time is referred to as AF_step.
In S208, further instructions are given to the motor drive circuit 9 to operate the lens driving motor 8, and the photographing lens 1 is moved to the position of the AF_step. Thereafter, in S209, the automatic focusing control process is completed.

The above processing is the second example of the automatic focusing control processing. This processing is performed by the CPU of the arithmetic processing circuit 7 so that the image pickup apparatus in FIG. 1 can perform automatic focusing. In particular, it is not clear whether or not a subject that is a point light source can be regarded as a point light source. However, automatic focusing in a dark environment is appropriate.
In the process of FIG. 4, in S205, the position of the photographing lens 1 when the brightness of the image obtained by the image sensor 2 is minimized and the position of the photographing lens 1 when the contrast of the image is maximized. It is determined whether or not the distance between the first lens and the second lens is equal to or greater than a predetermined value. Based on the determination result, the position of the photographing lens 1 (the position of AE_step in S206) and the contrast of the image when the brightness of the image is minimized are determined. One of the positions of the photographing lens 1 at the maximum (the position of AF_step in S207) is set as the in-focus position. Instead of this, for example, a position between the position of AE_step and the position of AF_step, which is separated from the position of AF_step by the above-described ratio of the distance to the predetermined value, may be set as the in-focus position.

In addition, the present invention is not limited to the above-described embodiments, and various improvements and changes can be made without departing from the scope of the present invention.
For example, in the embodiment described above, the position of the photographic lens 1 is continuously changed with respect to the change in the AE evaluation value and the AF evaluation value with respect to the change in the position of the photographic lens 1 shown in FIGS. All of them were obtained by actually measuring. Instead of this, for example, the position of the photographing lens 1 is discretely moved so that only the AE evaluation value and the AF evaluation value at that position are measured, and these measurement points are obtained by an interpolation operation such as Lagrange interpolation or spline interpolation, for example. An interpolated value of the AE evaluation value and the AF evaluation value between the AE evaluation value and the AF evaluation value may be calculated, and a change state of the AE evaluation value and the AF evaluation value may be obtained using the calculation result. By doing so, the number of times of actual measurement of the AE evaluation value and the AF evaluation value is reduced, so that the time required for automatic focusing is shortened.

  Further, in the above-described embodiment, by determining whether the brightness of the image obtained by the image sensor 2 is equal to or less than a predetermined value by the determination process in S102 of FIG. 2 or S202 of FIG. To determine whether the shooting environment is dark or bright. Instead of this, when an operation mode instruction of the apparatus, which is given by the user by an operation on a switch (not shown), is acquired, and the acquired instruction indicates an operation mode suitable for shooting a night view, The determination result of S102 of 2 and S202 of FIG. 4 is set to Yes, and the processing after S103 in FIG. 2 or the processing after S203 in FIG. 4 is performed, that is, for automatic focusing in a dark shooting environment. Processing may be performed.

It is a figure which shows the structure of the imaging device which implements this invention. It is a flowchart which shows the processing content of the 1st example of an automatic focusing control process. It is a figure explaining the focus position detection based on AE evaluation value. It is a flowchart which shows the processing content of the 2nd example of an automatic focusing control process. It is a figure explaining the process of FIG. It is a figure explaining the automatic focusing by a contrast detection system. It is a figure which shows the image of a point light source. It is a figure which shows the change of AF evaluation value when a point light source is made into a to-be-photographed object, and a luminance value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shooting lens 2 Imaging element 3 Imaging processing circuit 4 Pulse generation circuit 5 Output terminal part 6 BPF circuit 7 Arithmetic processing circuit 8 Lens drive motor 9 Motor drive circuit

Claims (15)

Brightness detecting means for detecting the brightness of an image obtained through the taking lens according to the position of the taking lens;
A focus detection means for detecting a focus position, which is the position when the subject image represented in the image is in focus, based on the minimum point of the brightness;
A focus detection apparatus comprising:   The focus detection apparatus according to claim 1, wherein the focus detection unit calculates the minimum point by an interpolation calculation based on a detection result of the brightness detection unit. Brightness detecting means for detecting the brightness of an image obtained through the taking lens according to the position of the taking lens;
Contrast detection means for detecting the contrast of the image according to the position;
Comparison means for comparing the brightness of the image with a predetermined brightness;
Based on either the brightness of the image selected according to the comparison result or the contrast of the image, the position at which the subject image represented by the image is in focus is adjusted. A focus detection means for detecting a focal position;
A focus detection apparatus comprising:   The focus detection unit detects the focus position based on the maximum point of contrast of the image when the brightness of the image is brighter than the predetermined brightness according to the comparison result, and the image The focus detection apparatus according to claim 3, wherein when the brightness of the image is darker than the predetermined brightness, the focus position is detected based on a minimum point of brightness of the image.   The focus detection apparatus according to claim 4, wherein the focus detection unit calculates the minimum point by an interpolation calculation based on a detection result of the brightness detection unit. Brightness detecting means for detecting the brightness of an image obtained through the taking lens according to the position of the taking lens;
Contrast detection means for detecting the contrast of the image according to the position;
Among the interval between the position of the photographing lens when the brightness of the image is minimized and the position of the photographing lens when the contrast of the image is maximized, the brightness of the image and the contrast of the image Focusing detection means for detecting a focusing position that is a position of the photographing lens when the subject image represented in the image is focused based on at least one of
A focus detection apparatus comprising:   The focus detection unit detects the focus position based on a minimum point of brightness of the image when the interval is longer than a predetermined interval. Focus detection device.   When the interval is closer than the predetermined interval and the brightness of the image is darker than the predetermined brightness, the focus detection unit is configured to adjust the focus based on a minimum point of the brightness of the image. The focus detection apparatus according to claim 7, wherein the focus position is detected.   The focus detection according to claim 6, wherein the focus detection unit detects the focus position based on a maximum point of contrast of the image when the interval is closer than a predetermined interval. apparatus.   The focus detection apparatus according to claim 7, wherein the focus detection unit calculates the minimum point by an interpolation calculation based on a detection result of the brightness detection unit. An acquisition means for acquiring an operation mode instruction;
Brightness detecting means for detecting the brightness of an image obtained through the taking lens according to the position of the taking lens;
Contrast detection means for detecting the contrast of the image according to the position;
When the acquisition unit acquires an instruction of an operation mode suitable for shooting a night scene, the subject image represented in the image is matched based on at least one of the brightness of the image and the contrast of the image. A focus detection means for detecting a focus position which is a position of the photographing lens when in focus;
A focus detection apparatus comprising:   The focus detection unit detects the focus position based on a minimum point of brightness of the image calculated by an interpolation calculation based on a detection result of the brightness detection unit. The focus detection apparatus described in 1. The brightness of the image obtained through the taking lens is detected according to the position of the taking lens,
Detecting an in-focus position, which is the position when the subject image represented in the image is in focus, based on the minimum point of the brightness;
A focus detection method characterized by the above. The brightness of the image obtained through the taking lens is detected according to the position of the taking lens,
Detecting the contrast of the image according to the position;
The brightness of the image is compared with a predetermined brightness,
Based on either the brightness of the image selected according to the comparison result or the contrast of the image, the position at which the subject image represented by the image is in focus is adjusted. Detect the focal position,
A focus detection method characterized by the above. The brightness of the image obtained through the taking lens is detected according to the position of the taking lens,
Detecting the contrast of the image according to the position;
Among the interval between the position of the photographing lens when the brightness of the image is minimized and the position of the photographing lens when the contrast of the image is maximized, the brightness of the image and the contrast of the image Based on at least one of the above, a focus position that is the position of the photographing lens when the subject image represented in the image is in focus is detected.
A focus detection method characterized by the above.

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