JP5765935B2 - Focus adjustment apparatus and method - Google Patents

Description

The present invention relates to an automatic focus adjustment apparatus and method, and more particularly, an automatic focus adjustment apparatus that performs focus adjustment using an image signal acquired by an image sensor that photoelectrically converts a subject image formed by an imaging optical system, and Regarding the method.

The following documents are related to an automatic focus adjustment apparatus and an automatic focus adjustment method related to a technique for performing focus adjustment on a point light source subject and a high brightness subject in a conventional automatic focus adjustment (AF) operation (Patent Document 1, Patent). Reference 2). In the technique described in Patent Document 1, an accurate focusing operation is performed even for a high-luminance object in a contrast detection control type automatic focusing device that detects a focusing control signal based on a captured video signal and performs a focusing operation. Be able to. Here, a high-brightness subject is determined by comparing the area of the low-brightness or medium-brightness part of the video signal on the imaging screen, and the focusing operation for a general subject is performed using a contrast signal. In the case of a luminance subject, a focusing operation is performed so that the area of the high luminance signal is reduced. On the other hand, the technique described in Patent Document 2 makes it possible to obtain a focus detection device that detects the presence or absence of saturation due to a point light source subject at low cost. This focus detection apparatus uses an image pickup device that picks up a subject image, a filter unit that removes a signal component of a predetermined frequency or less, an image pickup signal from the image pickup device after the filter unit removes the signal component, and before the signal component removal. Determining means for determining the presence or absence of signal saturation in the imaging signal of

Japanese Patent No. 3105334 JP 2008-185823 A

However, in the technique disclosed in Patent Document 1, in the case of a high-luminance subject and a point light source subject, the focusing operation is performed so that the area of the high-luminance signal becomes small. For this reason, it is good that the main subject is composed of only the point light source, but when the point light source subject and the illuminated normal subject are mixed, accurate focus adjustment may not be possible. This may be due to the influence of the color of the light source, or because the illuminated portion of the normal subject is blurred, the luminance is lowered and the area of the high luminance portion is reduced. Since recent devices have high pixel count, a slight focus shift cannot be ignored, and more accurate focus adjustment is required.

In the technique disclosed in Patent Document 2, the values of the high frequency component of the image signal are integrated and a point light source subject (saturated subject) is detected based on the integrated value. For this reason, erroneous detection may occur depending on the exposure of the camera. Also, the in-focus position is obtained using the high-frequency component of the image signal divided by the integrated value of the luminance signal. If a subject other than the point light source is included in the screen, the influence of that subject In some cases, an accurate in-focus position cannot be detected.

In view of the above problems, the focus adjustment apparatus of the present invention includes an image sensor, focus adjustment means, and focus position detection means. The image sensor photoelectrically converts a subject image formed by the photographing optical system to obtain an electrical image signal. The focus adjustment unit adjusts the focus of the subject image formed on the image sensor. The in-focus position detecting unit detects the in-focus position from the image signal generated by the image sensor while driving the focus adjusting unit. Further, to detect the in-focus position by using the fluctuation amount of the maximum value of the luminance signal and the fluctuation amount of the integrated value of the luminance signal obtained from the image signal generated by the image pickup device and driven by the focus adjustment unit. It is determined whether or not there is a point light source subject within the area of the image sensor that acquires the image signal.

Moreover, in view of the said subject, the focus adjustment method of this invention has a focus position detection step and a determination step. In the in-focus position detection step, while driving a focus adjustment unit that adjusts the focus of the subject image formed on the image sensor that photoelectrically converts the subject image formed by the photographing optical system to obtain an electrical image signal, The in-focus position is detected from the image signal generated by the image sensor. In the determination step, the in-focus position is detected using the amount of fluctuation of the maximum value of the luminance signal and the amount of fluctuation of the integrated value of the luminance signal that are obtained from the image signal generated by the image sensor and are driven by the focus adjustment unit. It is determined whether or not there is a point light source subject within the area of the image sensor that acquires an image signal for the purpose. And a focus position detection step is performed in a different aspect according to the determination result of the determination step.

According to the present invention, since a determination of presence of the point light source object from the amount of change of the integrated value of the variation amount of the maximum value of the luminance signal with the drive of the focus point adjusting means and the luminance signal, it allows faster processing It is. Thereby, it is possible to determine the presence or absence of a point light source subject without extending the time required for the focus adjustment operation, and even when a point light source subject and an illuminated normal subject are mixed, more accurate focus adjustment can be performed.

FIG. 1 is a block diagram of an imaging apparatus including an embodiment of a focus adjustment apparatus of the present invention. FIG. 2 is a diagram for explaining the operation procedure of the first embodiment. FIG. 3 is a diagram for explaining the operation of the first scan AF process according to the first embodiment. FIG. 4 is a schematic explanatory diagram of a first scan AF process according to the first embodiment. FIG. 5 is an explanatory diagram of an AF evaluation value based on a focus position and a second scan AF in the case of the point light source subject of the first embodiment. FIG. 6 is an explanatory diagram of the maximum value and integrated value of the luminance signal according to the focus position in the case of the normal subject (the subject that is not the point light source subject) of the first embodiment. FIG. 7 is an explanatory diagram of the maximum value and integrated value of the luminance signal depending on the focus position in the case of the point light source subject of the first embodiment. FIG. 8 is an explanatory diagram of the operation procedure of the point light source subject determination of the embodiment of the focus adjustment apparatus of the present invention. FIG. 9 is an explanatory diagram of an operation procedure of the focus adjustment apparatus according to the second embodiment of the present invention. FIG. 10 is a diagram illustrating the operation of the third scan AF process according to the second embodiment. FIG. 11 is a schematic explanatory diagram of a fourth scan AF process according to the second embodiment.

A feature of the present invention is that the region of the image sensor that acquires the image signal for detecting the in-focus position using the variation amount of the maximum value of the luminance signal and the variation amount of the integrated value of the luminance signal due to the driving of the focus adjustment unit. It is determined whether or not there is a point light source subject inside, and in-focus position detection is performed in a different manner depending on the determination result. Based on this concept, the focus adjustment apparatus and method of the present invention have the basic configuration as described in the section for solving the above-mentioned problems. Various forms are possible within the scope of this basic configuration. For example, in the presence of a point light source subject, it can be obtained by in-focus position detection using an image signal for in-focus position detection obtained when acquiring the maximum value and integrated value of the luminance signal for performing the determination. In the vicinity of the in-focus position, the in-focus position is detected from the image signal while driving the focus adjusting unit again. In Examples 1 and 2 to be described later, the second scan AF is performed to detect the in-focus position. In this case, the interval between the plurality of drive positions of the focus adjustment unit in the second drive is the interval between the plurality of drive positions of the focus adjustment unit in the determination (that is, the interval in the first or third scan AF described later). Finer.

In addition, an instruction receiving unit such as a release switch is provided. The maximum value and integrated value can be obtained and performed. In the second embodiment to be described later, the third scan AF is performed for the above-described determination. In this case, the focus adjustment is again performed in the vicinity of the in-focus position obtained by the in-focus position detection performed using the in-focus position detection image signal acquired in the determination after the instruction accepting instruction is issued. The in-focus position is detected from the image signal while driving the means. In Example 2 to be described later, for this purpose, the fourth scan AF (when the point light source subject is not present) or the second scan AF (when the point light source subject is present) is performed. More specifically, in this embodiment, before an imaging preparation operation instruction, AF evaluation values (evaluation values obtained by performing signal processing on an image signal for detecting an in-focus position) and luminance at coarser intervals than in the first scan AF processing A third scan AF process for obtaining the maximum value and integrated value of the signal is performed. Then, it is determined whether or not a point light source subject exists in the area and adversely affects AF. When it is determined that there is no point light source subject and the AF is not adversely affected, the following is performed. That is, after instructing the shooting preparation operation, a range narrower than the scan range of the third scan AF process in the vicinity of the temporary in-focus position obtained by the third scan AF process is set at the same interval as the first scan AF process. A fourth scan AF process for acquiring the AF evaluation value is executed to obtain the in-focus position. On the other hand, if it is determined that there is a point light source subject and the AF is adversely affected, the second scan AF process is executed after the shooting preparation operation instruction and the in-focus position is obtained.

In addition, when there is no point light source subject in the area, the image signal for detecting the in-focus position acquired when acquiring the maximum value and integrated value of the luminance signal for performing the determination is used. It can be configured to detect the focal position. In Example 1 to be described later, this is configured, and the first scan AF is also used for detecting the in-focus position. This scan AF can be performed at the same interval as the conventional normal AF operation. With this determination, if it is determined that there is no point light source subject and the AF is not adversely affected, The in-focus position is obtained from the AF evaluation value obtained by the scan AF process.

With the configuration as described above, it is possible to determine whether or not the point light source subject and the illuminated normal subject are mixed without extending the time required for AF, and the point light source subject and the illuminated normal subject are mixed. Even in this case, more accurate focus adjustment is possible. Also, the appearance of the LCD during AF can be improved. In addition, when generating a point light source subject, a luminance signal histogram (a list of the number of pixels for each luminance) is not created, and point light source subject determination (points) is made based on the maximum value and integrated value of the luminance signal at different driving positions of the focus adjusting means. Determination as to whether or not the light source subject is harmful to AF). Therefore, the processing speed can be increased, and the point light source subject determination reliability is improved because the region where the point light source subject determination is performed and the region where the automatic focus adjustment is performed completely coincide with each other.

Hereinafter, specific examples will be described.
Example 1
FIG. 1 shows a block diagram of an apparatus including Embodiment 1 of the present invention. Reference numeral 1 denotes an imaging device, 2 denotes a zoom lens group, and 3 denotes a focus lens group. Reference numeral 4 denotes a light amount adjusting means for controlling the amount of light beam transmitted through the photographing optical system including the zoom lens group 2, the focus lens group 3 and the like, and a diaphragm as an exposure means. Reference numeral 31 denotes the zoom lens group 2 and the focus lens group 3. This is a taking lens barrel including an aperture 4 and the like. Reference numeral 5 denotes a solid-state image sensor (hereinafter also referred to as a CCD) that forms a subject image that has passed through the photographing optical system and photoelectrically converts it. Reference numeral 6 denotes an imaging circuit that receives an electrical signal photoelectrically converted by the CCD 5 and performs various image processing to generate a predetermined image signal. Reference numeral 7 denotes an analog image signal generated by the imaging circuit 6 as a digital image. It is an A / D conversion circuit that changes to a signal. Reference numeral 8 denotes a memory (VRAM) such as a buffer memory that receives the output of the A / D conversion circuit 7 and temporarily stores the image signal. Reference numeral 9 denotes a D / A conversion circuit that reads out an image signal stored in the VRAM 8 and converts it into an analog signal and converts it into an image signal in a form suitable for reproduction output. Reference numeral 10 denotes a liquid crystal display device that displays this image signal ( An image display device (hereinafter also referred to as LCD).

A storage memory 12 stores image data including a semiconductor memory. A compression / decompression circuit 11 includes a compression circuit and an expansion circuit. This compression circuit reads the image signal temporarily stored in the VRAM 8 and performs compression processing and encoding processing of the image data in order to make it suitable for storage in the storage memory 12. The decompression circuit performs a decoding process, a decompression process, and the like for making the image data stored in the storage memory 12 into an optimum form for reproducing and displaying. Reference numeral 13 denotes an AE processing circuit that receives an output from the A / D conversion circuit 7 and performs automatic exposure (AE) processing. Reference numeral 14 denotes an automatic focus that receives an output from the A / D conversion circuit 7 and generates an AF evaluation value. It is a scan AF processing circuit that performs adjustment (AF) processing. Reference numeral 15 denotes a CPU that includes a calculation memory that controls the image pickup apparatus 1 and that includes a focus position detection unit. Reference numeral 16 denotes a timing generator (hereinafter referred to as TG) that generates a predetermined timing signal, and reference numeral 17 denotes a CCD driver. Reference numeral 21 denotes an aperture drive motor that drives the aperture 4, and 18 denotes a first motor drive circuit that drives and controls the aperture drive motor 21. Reference numeral 22 denotes a focus drive motor that drives the focus lens group 3, and reference numeral 19 denotes a second motor drive circuit that drives and controls the focus drive motor 22. Reference numeral 23 denotes a zoom drive motor that drives the zoom lens group 2, and reference numeral 20 denotes a third motor drive circuit that drives and controls the zoom drive motor 23. 24 is an operation switch comprising various switch groups, 25 is an electrically rewritable read-only memory in which programs for performing various controls and data used for performing various operations are stored in advance It is. Reference numeral 26 denotes a battery, 28 denotes a strobe light emitting unit, and 27 denotes a switching circuit that controls flash emission of the strobe light emitting unit 28. Reference numeral 29 denotes a display element such as an LED for performing warning display, and 30 denotes a speaker for performing voice guidance or warning. Reference numeral 33 denotes AF auxiliary light composed of a light source such as an LED, which is an illuminating means for illuminating all or part of the subject when the AF evaluation value is acquired, and reference numeral 32 denotes AF auxiliary light for driving the AF auxiliary light 33. This is an optical drive circuit. Reference numeral 35 denotes a shake detection sensor that detects camera shake, 34 denotes a shake detection circuit that processes a signal of the shake detection sensor 35, and 36 receives an output from the A / D conversion circuit 7 and receives a face position on the screen. It is a face detection circuit that detects the size of a face.

As a storage memory that is a storage medium for image data or the like, a fixed type semiconductor memory such as a flash memory or a semiconductor memory such as a card type flash memory that has a card shape or a stick shape and is detachable from the device Applies. In addition, various forms such as a magnetic storage medium such as a hard disk or a floppy disk are applied. The operation switch 24 includes a main power switch for starting the imaging apparatus 1 and supplying power, and a release switch for starting a photographing operation (storage operation). In addition, there are a playback switch for starting a playback operation, a zoom switch for moving the zoom lens group 2 of the photographing optical system to perform zooming, an optical viewfinder (OVF), an electronic viewfinder (EVF) changeover switch, and the like. The release switch has a first stroke (hereinafter referred to as SW1) for generating an instruction signal for starting an AE process and an AF process performed prior to the photographing operation and a second stroke (hereinafter referred to as an instruction signal for starting an actual exposure operation). SW2) and a two-stage switch.

The operation in this embodiment configured as described above will be described below.
First, the light flux of the subject that has passed through the taking lens barrel 31 of the image pickup apparatus 1 is adjusted on the light amount by the diaphragm 4 and then imaged on the light receiving surface of the CCD 5. This subject image is converted into an electrical signal by photoelectric conversion processing by the CCD 5 and output to the imaging circuit 6. In the imaging circuit 6, various signal processing is performed on the input signal, and a predetermined image signal is generated. This image signal is output to the A / D conversion circuit 7 and converted into a digital signal (image data), and then temporarily stored in the VRAM 8. The image data stored in the VRAM 8 is output to the D / A conversion circuit 9, converted into an analog signal, converted into an image signal in a form suitable for display, and then displayed as an image on the LCD. On the other hand, the image data stored in the VRAM 8 is also output to the compression / decompression circuit 11. After compression processing is performed by the compression circuit in the compression / decompression circuit 11, it is converted into image data in a form suitable for storage and stored in the storage memory 12.

Further, for example, when a reproduction switch (not shown) of the operation switches 24 is operated and turned on, the reproduction operation is started. Then, the image data stored in the compressed form in the storage memory 12 is output to the compression / expansion circuit 11, subjected to decoding processing, expansion processing, etc. in the expansion circuit, and then output to the VRAM 8 for temporary storage. Is done. Further, the image data is output to the D / A conversion circuit 9, converted into an analog signal, converted into an image signal having a form suitable for display, and then displayed on the LCD 10 as an image. On the other hand, the image data digitized by the A / D conversion circuit 7 is also output to the AE processing circuit 13, the scan AF processing circuit 14, and the face detection circuit 36 separately from the VRAM 8 described above. First, in the AE processing circuit 13 serving as a brightness measuring means for measuring the brightness of the light beam incident from the photographing optical system, the input digital image signal is received and the brightness value of the image data for one screen is obtained. Arithmetic processing such as cumulative addition is performed. Thereby, the AE evaluation value corresponding to the brightness of the subject is calculated. This AE evaluation value is output to the CPU 15.

Further, the scan AF processing circuit 14 serving as a focus position detection means receives the input digital image signal and extracts a high frequency component of the image data through a high pass filter (HPF) or the like. Then, arithmetic processing such as cumulative addition is further performed to calculate an AF evaluation value signal corresponding to the contour component amount on the high frequency side. Specifically, in the scan AF process, high-frequency components of image data corresponding to a partial area of the screen designated as the AF area are extracted through a high-pass filter (HPF) or the like, and an arithmetic process such as cumulative addition is performed. Do. Thereby, an AF evaluation value signal corresponding to the contour component amount on the high frequency side and the like is calculated. As this AF area, when it is one place in the central part or any part on the screen, or when it is a central part or any part on the screen and a plurality of adjacent parts, a plurality of points distributed discretely are used. There are cases. In this way, the scan AF processing circuit 14 plays a role of high frequency component detection means for detecting a predetermined high frequency component from the image signal generated by the CCD 5 in the process of performing the AF processing.

The face detection circuit 36 receives the input digital image signal, searches the image for a part characterizing the face such as eyes and eyebrows, and obtains the position of the person's face on the image. Further, the size and inclination of the face are obtained from the positional relationship such as the interval between the parts characterizing the face.

On the other hand, a predetermined timing signal is output from the TG 16 to the CPU 15, the imaging circuit 6, and the CCD driver 17, and the CPU 15 performs various controls in synchronization with this timing signal. The imaging circuit 6 receives the timing signal from the TG 16 and performs various image processing such as separation of color signals in synchronization with the timing signal. Further, the CCD driver 17 receives the timing signal of the TG 16 and drives the CCD 5 in synchronization therewith. The CPU 15 controls the first motor drive circuit 18, the second motor drive circuit 19, and the third motor drive circuit 20, respectively. Thereby, the diaphragm 4, the focus lens group 3, and the zoom lens group 2 are driven and controlled via the diaphragm drive motor 21, the focus drive motor 22, and the zoom drive motor 23. That is, the CPU 15 controls the first motor drive circuit 18 based on the AE evaluation value calculated by the AE processing circuit 13 to drive the aperture drive motor 21 and adjust the aperture amount of the aperture 4 so as to be appropriate. AE control is performed. Further, the CPU 15 controls the second motor drive circuit 19 based on the AF evaluation value signal calculated by the scan AF processing circuit 14 to drive the focus drive motor 22 to move the focus lens group 3 to the in-focus position. I do. When a zoom switch (not shown) among the operation switches 24 is operated, the CPU 15 controls the zoom motor group 23 by controlling the third motor drive circuit 20 to drive the zoom motor 23. The zooming operation is performed for the photographing optical system.

Next, the actual shooting operation of the imaging apparatus will be described with reference to the flowchart shown in FIG. In this description, the operation of acquiring the AF evaluation value while driving the focus lens group 3 to a predetermined position is referred to as scanning, and the interval of the position of the focus lens for acquiring the AF evaluation value is referred to as scanning interval. Further, the position for acquiring the AF evaluation value is the scan point, the number of the AF evaluation value is acquired as the number of scan points, the range for acquiring the AF evaluation value is the scan range, and the area for acquiring the image signal for detecting the in-focus position Is referred to as an AF frame.

When the main power switch of the image pickup apparatus 1 is in the on state and the operation mode of the image pickup apparatus is in the shooting (recording) mode, a shooting processing sequence is executed and imaging is performed by supplying power to the CCD 5 or the like. Enable. First, in step S1, the CPU 15 displays an image formed on the CCD 5 through the photographing lens barrel 31 as an image on the LCD. That is, the subject image formed on the CCD 5 is photoelectrically converted by the CCD 5 and converted into an electrical signal, and then output to the imaging circuit 6. Therefore, various signal processing is performed on the input signal to generate a predetermined image signal, which is then output to the A / D conversion circuit 7 to be converted into a digital signal (image data) and temporarily stored in the VRAM 8. Is done. The image data stored in the VRAM 8 is output to the D / A conversion circuit 9, converted into an analog signal, converted into an image signal in a form suitable for display, and then displayed as an image on the LCD.

Next, in step S2, the state of the release switch is confirmed. When the release switch is operated by the photographer and the CPU 15 confirms that SW1 (first stroke of the release switch) is turned on, the shooting preparation operation is started. That is, the process proceeds to the next step S3, and normal AE processing is executed. Subsequently, a first scan AF process is performed in step S4. In step S5, it is determined whether or not the subject is a point light source subject from the integrated value and maximum value of the luminance signal at the positions of the plurality of focus lens groups 3 acquired in the first scan AF process. If it is determined in step S5 that the subject is a point light source subject, the second scan AF process in step S6 is executed. Steps S4, S5, and S6 will be described later.

In step S7, the focus possibility is determined and the focus position is calculated. For a case where it is determined that the subject is a normal subject (a subject that is not a saturated subject such as a point light source), a specific method for determining the possibility of focusing is described in, for example, Japanese Patent No. 4235422, and a specific method for calculating a focusing position is described. Such a method is described in, for example, Japanese Patent No. 2620235. Since these methods are not directly related to the present invention, description thereof is omitted. A case where the point light source subject is determined will be described later. A case where it is determined as a point light source and the second scan AF process of step S6 is executed will also be described later.

If it is determined in step S7 that focusing is possible, AFOK display is performed in step S8. This is performed by, for example, turning on the display element 29 and simultaneously displaying a green frame on the LCD. Conversely, if it is not determined that focusing is possible, AFNG display is performed in step S8. This is performed by, for example, displaying the blinking display element 29 and simultaneously displaying a yellow frame on the LCD. If it is determined in the first scan AF process in step S4 that focusing is impossible, the processes in steps S5 to S7 are not performed, and AFNG display is performed in step S8. In step S9, the CPU 15 checks SW2 (second stroke of the release switch). If SW2 is on, the CPU 15 proceeds to step S10 and executes actual exposure processing.

The first scan AF process performed in step S4 will be described with reference to FIG. The first scan AF process includes an AF evaluation value, a maximum value of the output (luminance signal) of all pixels in the AF frame of the image signal generated by the CCD 5, and an integrated value of the output (luminance signal) of all pixels of the AF frame. Is obtained by moving the focus lens group 3 at a predetermined scan interval. The AF evaluation value is a signal value of a high frequency component output from the image signal generated by the CCD 5. This scan interval is set to about 3 to 5 times the open depth, and is an interval suitable for detecting the peak of the AF evaluation value. The scan range is, in principle, from a position corresponding to infinity (for example, “A” in FIG. 4) to a position corresponding to the closest distance set in each photographing mode (“B” in FIG. 4). .

First, in step S301, the CPU 15 controls the motor 22 via the second motor drive circuit 19 that drives and controls the focus drive motor 22, and moves the focus lens group 3 to a position corresponding to infinity ("A" in FIG. 4). Drive to. This drive speed is the maximum speed of the focus drive motor 22 or a speed close to the maximum speed. In step S302, the AF evaluation value of the area corresponding to the AF frame set in the photographing area and the position of the focus lens group 3 are stored in a calculation memory (not shown) built in the CPU 15. In step S303, the maximum value, minimum value, and integrated value of the signal output (luminance signal) in the area corresponding to the AF frame set in the photographing area are obtained, and the calculation memory built in the CPU 15 together with the position of the focus lens group 3 is obtained. To remember. In step S304, it is checked whether or not the lens position is at the scan end position. If it is the end position, the process proceeds to step S306, and if not, the process proceeds to step S305. The scan end position is a position (“B” in FIG. 4) corresponding to the closest distance set in each photographing mode. In step S305, the focus lens group 3 is driven and moved in a predetermined direction by a predetermined amount. In step S306, the position of the focus lens group 3 corresponding to the position where the AF evaluation value is maximized is calculated from the AF evaluation value stored in step S302 and its lens position. Acquisition of the output of the AF processing circuit is not performed for all the stop positions of the focus lens group 3 but for each predetermined step for speeding up the scan AF. For example, the AF evaluation value signal may be acquired at points a1, a2, and a3 shown in FIG. Note that the scan points such as a1, a2, and a3 shown in FIG. 4 are drawn accurately in the interval in the horizontal axis direction, but the values in the vertical axis direction are rough and only show a substantial change (this point). The same applies to scan points drawn in the drawings described later).

In such a case, the in-focus position C is obtained by calculation from the point where the AF evaluation value signal becomes the maximum value and the points before and after the point. In this way, the reliability of the AF evaluation value signal can be evaluated before the point (C in FIG. 4) where the AF evaluation value signal has the maximum value is obtained by performing the interpolation calculation. This specific method is described in, for example, Japanese Patent No. 4235422. The reliability of the focus evaluation value is determined based on, for example, whether or not the shape of the focus evaluation value for each imaging position is a mountain shape.

If the reliability is sufficient, a point at which the AF evaluation value signal becomes the maximum value is obtained. If the reliability is not sufficient, the process for obtaining the point at which the AF evaluation value signal becomes the maximum value is not performed. As described above, the processes in steps S5 to S7 in FIG. 2 are not performed, and the AFNG display is performed in step S8 in FIG. I do. When the position of the focus lens group 3 corresponding to the position where the AF evaluation value is maximum is obtained in the first scan AF process, the point light source determination is performed in step S5 of FIG.

The point light source determination performed in step S5 of FIG. 2 will be described. FIG. 4 shows AF evaluation values based on the focus position in the case of a normal subject. FIG. 5 shows AF evaluation values according to the focus position in the case of a point light source subject. FIG. 6 shows the maximum value and integrated value of the luminance signal depending on the focus position in the case of a normal subject. FIG. 7 shows the maximum value and integrated value of the luminance signal depending on the focus position in the case of the point light source subject. As shown in FIG. 4, in the case of a normal subject, the AF evaluation value is maximized at the in-focus position, but as shown in FIG. 5, in the point light source subject, the AF evaluation value is not maximized at the in-focus position. The local minimum value in the vicinity is the in-focus position. Therefore, it is necessary to determine whether or not the point light source subject exists within the AF frame and to use different scanning methods for searching for the in-focus position according to the result. Therefore, it is determined whether a saturated subject such as a point light source exists in the AF frame as follows.

The point light source subject determination uses the following characteristics that accompany changes in focus between the point light source subject and the normal subject. As shown in FIG. 6, in the case of a normal subject, the maximum value of the luminance signal in the screen is maximized at the in-focus position. This is due to the following reason. In a state where the high luminance portion (white portion) of the subject is not in focus (blurred), the luminance signal value decreases due to mixing with other surrounding colors. However, focusing is used to eliminate mixing with other colors, resulting in higher contrast, so that the white portion with higher luminance becomes whiter and the luminance signal value becomes higher.

Further, the integrated value of the luminance signal of all the pixels in the AF frame hardly changes as shown in FIG. 6 in the case of a normal subject without saturation. In principle, the amount of light is constant regardless of the focus state, so there is no difference depending on the focus position. However, in practice, some variation occurs due to changes in the subject in the AF frame due to flickering of the light source, noise on the signal, camera shake during the scanning operation, and the like. As shown in FIG. 7, in the case of a point light source subject, the maximum value of the luminance signal in the screen hardly changes as shown. This is because the high luminance part of the subject is saturated due to a point light source, and even if the focus is blurred and the luminance signal value decreases, the output from the CCD remains saturated. This is because the observed luminance signal values are the same. In addition, the integrated value of the luminance signal in the AF frame has a high portion of the output luminance signal from the saturated CCD because the saturated point light source spreads around when it is out of focus (blurred). Become bigger. On the other hand, since the point light source is not spread by focusing, the high portion of the output luminance signal from the saturated CCD is reduced, and the integrated value of the luminance signal is reduced.

The operation procedure of the point light source determination is shown in FIG. First, in step S801, it is checked from the face detection result whether the detection is successful and a face is detected. If the detection is successful and a face larger than a predetermined size is detected, the process advances to step S809 to determine that the subject is a normal subject. Even if a face is detected, if the face is small, a point light source subject may enter the AF frame. In this case, the subject is not determined as a normal subject. Since the size of the AF frame when a face is detected matches the size of the face, the point light source subject does not normally enter the AF frame, but when the AF frame becomes smaller, the AF evaluation value is obtained. Since the signal amount decreases and AF with high accuracy cannot be expected, a lower limit is set for the size of the AF frame. Therefore, when the detected face size is small, there is a possibility that the point light source subject enters the AF frame.

In step S802, it is determined from the result of the AE process in step S3 in FIG. If it is brighter than the predetermined luminance, the process proceeds to step S809 and is determined to be a normal subject. If it is darker than the predetermined brightness, the process proceeds to step S803. In step S803, it is determined whether or not the variation of the luminance signal with the focus movement of the maximum value within the screen is small. This is done by referring to the maximum value in the screen of the luminance signal and the position of the focus lens group 3 that acquired the value in step S303 in FIG. The maximum value of the maximum value of the luminance signal acquired during the driving of the focus lens group 3 in the screen is compared with the minimum value of the maximum value of the luminance signal acquired during the driving of the focus lens group 3 in the screen. For example, in FIG. 6, the maximum value is the maximum value of the luminance signal in the screen at the focus position a2, and the minimum value is the maximum value of the luminance signal in the screen at the focus position a0. In FIG. 7, the maximum value is the maximum value within the screen of the luminance signal at the focus position a2, and the minimum value is the maximum value within the screen of the luminance signal at the focus position a4. When the maximum value and the minimum value in the screen of the luminance signal acquired during driving of the focus lens group 3 are obtained, the difference is calculated and compared with a predetermined value. If the difference is smaller than the predetermined value, the process proceeds to step S804. If it is equal to or greater than the predetermined value, the process proceeds to step S809, where it is determined as a normal subject.

In step S804, it is determined whether the maximum value of the luminance signal is bright. This is also performed by referring to the maximum value in the screen of the luminance signal stored in step S303 in FIG. The maximum value in the screen of the luminance signal at the peak position obtained in S306 of FIG. 3 is compared with a predetermined value. If it is larger than the predetermined value, the process proceeds to step S805. If it is equal to or smaller than the predetermined value, the process proceeds to step S809 and is determined to be a normal subject.

In step S805, it is determined whether or not the minimum value of the luminance signal is dark. This is also performed by referring to the minimum value in the screen of the luminance signal stored in step S303 in FIG. The minimum value in the screen of the luminance signal at the peak position obtained in S306 of FIG. 3 is compared with a predetermined value, and if it is smaller than the predetermined value, the process proceeds to step S806. If it is equal to or greater than the predetermined value, the process proceeds to step S809, where it is determined as a normal subject. A subject including a point light source such as a night view is characterized by a dark overall light source and a high contrast. In the processing of steps S805 and S806, it is checked whether or not the subject is such a subject. In the processes in steps S805 and S806, a signal other than the peak position of the focus lens group 3 may be used.

In step S806, it is determined whether or not there is a large variation in the integrated value in the screen of the luminance signal due to the focus movement. This is also performed by referring to the integrated value within the AF frame of the luminance signal for each position of the focus lens group 3 stored in step S303 in FIG. The maximum value of the integrated value of the luminance signal acquired during the driving of the focus lens group 3 in the screen is compared with the minimum value of the integrated value of the luminance signal acquired during the driving of the focus lens group 3 in the screen. For example, in FIG. 6, the maximum value is the integrated value of the luminance signal in the AF frame at the focus position a2, and the minimum value is the integrated value of the luminance signal in the AF frame at the focus position a4. In FIG. 7, the maximum value is the integrated value of the luminance signal in the AF frame at the focus position a0, and the minimum value is the integrated value of the luminance signal in the AF frame at the focus a2. When the maximum value and the minimum value of the integrated value within the AF frame of the luminance signal acquired during driving of the focus lens group 3 are obtained, the difference is calculated and compared with a predetermined value. If the difference is greater than the predetermined value, the process proceeds to step S807. If it is equal to or smaller than the predetermined value, the process proceeds to step S809 and is determined to be a normal subject.

In step S807, it is checked whether or not the focus position at which the minimum value of the integrated value of the luminance signal output as the focus position moves is near the focus position where the AF evaluation value is maximized. For example, in FIG. 6, the focus position at which the minimum value of the integrated value of the luminance signal is obtained is the focus position a4, and in FIG. 7, the minimum value is the focus position a2. The focus position is compared with the peak position obtained in step S306 in FIG. 3 (for example, “C” in FIGS. 4 and 5). If the difference is within a predetermined value, the process proceeds to step S808, where the point light source subject is detected. judge. If the difference is larger than the predetermined value, the process proceeds to step S809 and is determined to be a normal subject.

Next, the second scan AF process performed in step S6 of FIG. 2 will be described. The outline is the same as the first scan AF process in step S4. The point that the scan interval is about half that of the first scan AF process, the point that the scan range is limited to the vicinity of the peak position of the AF evaluation value obtained by the first scan AF process, Different from the one scan AF process. The operation will be described with reference to FIG. In the first scan AF process, scanning from “A” to “B” in FIG. 5 is performed, and “C” in FIG. 5 is obtained as the peak position of the AF evaluation value. However, this peak position is influenced by the point light source subject and may be different from the original focus position. Therefore, considering that a larger error than usual occurs in calculation of the peak position of the AF evaluation value, “a” to “b” shown in FIG. 5 are set as the scan range, and the scan interval is about half of the first scan AF processing. The scanning operation is performed. Since AF is performed on the point light source subject, when scanning is started from “a” in FIG. 5, the AF evaluation value decreases as the true focus position “c” is approached, and at the same time, the luminance within the AF frame The integrated value of the signal also decreases. After the in-focus position “c”, both the AF evaluation value and the integrated value of the luminance signal within the AF frame start to increase. Therefore, the in-focus position can be obtained by obtaining the minimum values of both in the scan range. Therefore, by referring to the AF evaluation value and the integrated value stored during the scanning operation and the position where the value is acquired, the minimum value of both is obtained.

White circles shown in FIG. 5 are scan points. Since data acquisition is started from “a” in FIG. 5, at the next scan point, the acquired AF evaluation value and the integrated value are compared with the AF evaluation value and the integrated value at the point “a”. Determine whether or not. Similar determination is performed at the next scan point. As this process is repeated, the minimum value of the AF evaluation value and the integrated value passes, and the value starts to increase. Thereafter, the comparison of the acquired values is continued. This time, we will check that the value is increasing. However, if the processing is continued, the AF evaluation value may decrease again. In this case, the value comparison process is terminated at this point.

In FIG. 5, since the local minimum value is obtained at the fourth scan point, the AF evaluation value and the integrated value are increased from the fifth scan point. The process of comparing the AF evaluation value and the integrated value is continued toward “b” in FIG. Then, at the eighth scan point, the AF evaluation value decreases again. Therefore, when the comparison of the values acquired at the eighth and seventh scan points is completed, the value comparison process is terminated. Then, the process proceeds from the second scan AF process in step S6 to the in-focus position calculation process in step S7. The process of calculating the in-focus position of step S7 when it is determined as a point light source subject is performed only when both the AF evaluation value and the minimum value of the luminance signal integrated value are found in the second scan AF process of step S6. . Interpolation calculation is performed from the result of the second scan AF process in step S6, and the true minimum value is obtained by calculation in the focus position calculation process in step S7.

In FIG. 5, the AF evaluation value and the integrated value take the minimum value at the fifth scan point. However, the scanning performed here is not performed for the stop positions of all the focus lens groups 3 in order to increase the AF speed, but is performed at predetermined steps as shown in FIG. For this reason, there may be a focus position whose value is smaller than the scan point from which the minimum value is acquired. Therefore, the true minimum value (“c” in FIG. 5) is obtained by calculation from the point where the minimum value is obtained and the points before and after the minimum value. Since this method is publicly known, a detailed description is omitted.

When the in-focus position calculation is completed, AFOK display is performed in step S8 in FIG. If the local minimum value of either the AF evaluation value or the integrated value is not found in the process of step S6, the in-focus position cannot be found, so it is determined as AFNG. Then, the calculation of the in-focus position in step S7 in FIG. 2 is not performed, and AFNG display is performed in step S8 in FIG. By doing this, the AF time can be made the same as in the conventional case for a normal subject, and accurate focus adjustment can be performed without making the exposure amount below the appropriate value even when a point light source subject exists. Is possible.

(Example 2)
A second embodiment of the present invention will be described. The difference between the second embodiment and the first embodiment is that a point light source subject exists in the AF frame, and data acquisition processing for determining whether or not it adversely affects AF is performed before SW1 is turned on. That is, a third scan AF process is performed to acquire the AF evaluation value and the maximum value and integrated value of the luminance signal at coarser intervals before SW1 is turned on, and a point light source subject exists in the AF frame after SW1 is turned on, which is harmful to AF. It is a point to determine whether or not to give. Note that since the number and position of AF frames in the third scan AF performed before SW1 is turned on are determined by the photographer, the number of AF frames for performing point light source determination may be one at a minimum.

The operation will be described with reference to the flowchart shown in FIG. As in the first embodiment, when the main power switch of the imaging apparatus 1 is in the ON state and the operation mode of the imaging apparatus is in the shooting (recording) mode, a shooting process sequence is executed and the power to the CCD 5 and the like is To enable imaging. First, in step S901, normal AE processing is executed so that an image displayed on the LCD becomes appropriate. Next, in step S902, as in the first embodiment, the CPU 15 displays an image formed on the CCD 5 through the photographing lens barrel 31 as an image on the LCD. In step S903, a third scan AF process is performed to drive the focus lens group 3 to an approximate focus position. This process will be described later. In step S904, the state of the release switch is confirmed. When the photographer operates the release switch and the CPU 15 confirms that SW1 (the first stroke of the release switch) is turned on, the process proceeds to the next step S905, and normal AE processing is executed.

In step S906, it is determined whether or not a point light source subject exists within the AF frame. The contents will be described later. If it is determined that the subject is a point light source subject, a second scan AF process is performed in step S907. If it is determined that the subject is a normal subject, a fourth scan AF process is performed in step S908. These processes will be described later. Thereafter, the process proceeds to step S7, and thereafter the same processing as in the first embodiment is performed. In step S7, an in-focus position calculation process is executed. In step S8, an AF in-focus / in-focus display process is executed. In step S9, confirmation of SW2 is executed. If SW2 is on, the process proceeds to step S10 and actual exposure processing is executed.

The third scan AF process executed in step S903 will be described. FIG. 10 shows the operation procedure. When the third scan AF process is started, a minute driving operation is performed in step S1001, and it is determined whether or not it is in focus. If not in focus, it is determined in which direction the focus is in focus. The minute driving means that the focus lens group 3 is driven by a minute amount (an amount in which a focus change cannot be confirmed on the LCD) in the near direction or the infinity direction, and focusing / non-focusing and focusing are performed from the AF evaluation value obtained as a result. This is an operation for detecting the direction in which the focus lens group 3 should be driven.

If it is determined in step 1001 that the subject is in focus, the process proceeds from step S1002 to step S1008, and processing at the time of focusing is performed. If the focus is not determined in step S1001, the process proceeds from step S1002 to step S1003. In step S1003, if the in-focus direction can be determined in step S1001, the process proceeds to step S1004 to perform a hill-climbing drive operation. If the in-focus direction cannot be determined in step S1001, the process returns to step S1001 and the minute drive operation is performed. Continue. In step S1004, the lens is hill-climbed and driven at a high speed in the direction in which the AF evaluation value increases. The hill-climbing drive is a scan for searching for an in-focus position while changing the scan interval according to the degree of focus during the hill-climbing drive. When the degree of focus is low, scanning is performed at a relatively coarse scan interval of 5 to 10 depths, and the scan interval is made finer as the degree of focus is increased, and relatively fine scan intervals of 2 to 4 depths are in the vicinity of the in-focus position. Scan with. If it is determined in step S1005 that the peak of the AF evaluation value has been exceeded, the process proceeds to step S1006. If it is not determined that the peak of the AF evaluation value has been exceeded, the process returns to step S1004 to continue hill-climbing driving. In step S1006, the AF evaluation value during hill-climbing driving is returned to the position of the focus lens group 3 at the peak. In step S1007, it is determined whether or not the AF evaluation value has returned to the position of the focus lens group 3 at the peak. If the AF evaluation value has returned, the process returns to step S1001 to perform the minute driving operation again. If the AF evaluation value has not returned to the peak position, the process returns to step S1006 to continue the operation of returning to the peak.

Next, the restart determination process at the time of focusing from step S1008 will be described. In step S1008, the AF evaluation value when it is determined that the focus is achieved is held. In step S1009, the latest various AF evaluation values are acquired. In step S1010, the AF evaluation value held in step S1008 is compared with the AF evaluation value newly acquired in step S1009. If there is a difference of a predetermined level or more, it is determined that the system is restarted, and the process proceeds to step S1001 to resume the minute driving operation. To do. If it is not determined to be restarted in step S1010, the process proceeds to step S1011, the lens is stopped, and the process returns to step S1009 to continue the restart determination.

Here, the determination of whether or not a point light source subject exists in step S906 in FIG. 9 will be described. This process is the same as in the first embodiment, but the scan operation (third scan AF process) is executed before turning on SW1, and the AF evaluation value, the maximum value of the luminance signal, and the integrated value are acquired. There is a possibility that the value has been obtained from before it was properly framing. Therefore, the output of the shake detection sensor 35 is monitored via the shake detection circuit 34, and the maximum value and integrated value of the luminance signal from the time when the output falls below a certain value are used for the point light source determination. In addition, a limit is added to the number of values used for determination. That is, only a predetermined number of values immediately before SW1 is turned on are used for determination. This is to prevent erroneous detection due to use of a lot of meaningless data. This is because, for example, when the camera main power switch is turned on for a long time, the subject may change even if the output of the shake detection sensor is small. For example, this may occur when the camera is mounted on a tripod. In this manner, whether or not the subject is a point light source subject is determined in the same manner as in the first embodiment except that the number of data used for the determination is restricted.

The point light source determination will be described with reference to FIG. Steps S801 and S802 perform the same processing as in the first embodiment. In step S <b> 803, it is determined whether or not the fluctuation associated with the focus movement of the maximum value of the luminance signal in the restricted range within the screen is small. Among the predetermined number immediately before the switch SW1 is turned on after the output of the shake detection sensor 35 becomes a certain value or less, the same as the maximum value of the maximum value in the screen of the luminance signal acquired while the focus lens group 3 is being driven. The minimum value of the maximum value in the screen of the luminance signal acquired during driving is compared. The difference is calculated and compared with a predetermined value. If the difference is smaller than the predetermined value, the process proceeds to step S804. If it is equal to or greater than the predetermined value, the process proceeds to step S809, where it is determined as a normal subject. Steps S804 and S805 are the same as those in the first embodiment.

In step S806, it is determined whether or not there is a large variation in the integrated value within the screen of the luminance signal within the restricted range due to focus movement. Of the predetermined number immediately before the switch SW1 is turned on after the output of the shake detection sensor 35 becomes a certain value or less, the same as the maximum integrated value in the screen of the luminance signal acquired while the focus lens group 3 is being driven. The minimum value of the integrated value in the screen of the luminance signal acquired during driving is compared. The difference is calculated and compared with a predetermined value. If the difference is greater than the predetermined value, the process proceeds to step S807. If it is equal to or smaller than the predetermined value, the process proceeds to step S809 and is determined to be a normal subject. In step S807, it is checked whether or not the focus position at which the minimum value of the integrated value of the luminance signal value output with the focus position movement is near the focus position where the AF evaluation value is maximized. The focus position at which the integrated value in the screen of the luminance signal acquired during the lens driving becomes the minimum among the predetermined number immediately before the switch SW1 is turned on after the output of the sensor 35 becomes a certain value or less, and the step of FIG. The peak positions obtained in the third scan AF process of S903 are compared. If the difference is within the predetermined value, the process proceeds to step S808 to determine that the subject is a point light source subject. If the difference is larger than the predetermined value, the process proceeds to step S809 and is determined to be a normal subject.

The second scan AF process performed in step S907 when it is determined as a point light source subject will be described. If the approximate focus position is detected as a result of the third scan AF process performed in step S903, the same process as the second scan AF process in step S6 of FIG. . However, if the approximate in-focus position has not been detected as a result of the third scan AF process performed in step S903, the first scan AF process in step S4 of FIG. The same process as the second scan AF process is performed.

Next, the fourth scan AF process performed in step S908 when it is determined as a normal subject will be described. If the approximate focus position is detected as a result of the third scan AF process performed in step S903, the scan interval is equal to the first scan AF process and coarser than the second scan AF process. Execute the process. The scan range is limited to the vicinity of the peak position of the AF evaluation value obtained in the third scan AF process, and is set narrower than in the second scan AF process. The method for calculating the in-focus position is the same as in the first scan AF process.

The operation will be described with reference to FIG. In the third scan AF process, scanning is performed from “A” to “B” in FIG. 11 or a partial range thereof, and “C” in FIG. 11 is obtained as the peak position of the AF evaluation value. However, since this peak position is an approximate focus position, the scan range is from “a” to “b” shown in FIG. 11, the scan interval is the same as the first scan AF process, and the second scan AF process. A scan operation with a coarse interval is performed. When scanning is started from “a” in FIG. 11, the AF evaluation value increases as the true in-focus position “c” is approached. After the in-focus position “c”, both the AF evaluation value and the integrated value of the luminance signal in the AF frame start to decrease. Therefore, the in-focus position can be obtained by obtaining the maximum value in this scan range. Therefore, the local maximum value is obtained by referring to the AF evaluation value stored during the scanning operation and the position where the value is acquired.

A white circle shown in FIG. 11 is a scan point. Since data acquisition starts from “a” in FIG. 11, at the next scan point, the acquired AF evaluation value is compared with the AF evaluation value at the point “a” to determine whether or not it has increased. . Similar determination is performed at the next scan point. While this process is repeated, the maximum value of the AF evaluation value is passed, and the value starts to decrease. Thereafter, the comparison of the acquired values is continued. This time, we will check that the value is decreasing. In FIG. 11, since the maximum value is obtained at the third scan point, the AF evaluation value is decreased from the fourth scan point. The AF evaluation value comparison process is continued until “b” in FIG. Then, the process proceeds to the focus position calculation process in step S7 in FIG. Interpolation calculation is performed from the result of the fourth scan AF process in step S908, and the true maximum value is obtained by calculation in the focus position calculation process in step S7.

In FIG. 11, the AF evaluation value takes the minimum value at the third scan point. However, the scanning performed here is not performed for the stop positions of all the focus lens groups 3 in order to increase the AF speed, but is performed at predetermined steps as shown in FIG. For this reason, there is a possibility that there is a focus position whose value is larger than the scan point from which the maximum value is acquired. Therefore, the true maximum value (“c” in FIG. 11) is obtained by calculation from the point where the maximum value is reached and the points before and after that point.

When the in-focus position calculation is completed, AFOK display is performed in step S8 in FIG. If the local maximum value of the AF evaluation value is not found in the process of step S908, the in-focus position cannot be found. Therefore, it is determined as AFNG, and the in-focus position is not calculated in step S7 in FIG. The display is performed in step S8 of FIG. As a result of the third scan AF process performed in step S903, if the approximate focus position is not detected, the first scan AF process in step S4 of FIG.

In this way, even when a point light source subject and an illuminated normal subject are mixed, more accurate focus adjustment is possible.

Although the first embodiment and the second embodiment have been described using a compact digital camera as an example, the present invention can also be applied to AF during live view such as a digital video camera or a digital single lens reflex camera. In the first and second embodiments, the CCD is described as an example of the image pickup device. However, the present invention can be applied to other image pickup devices such as CMOS.

DESCRIPTION OF SYMBOLS 1 ... Imaging device, 3 ... Focus lens group (focus adjustment means), 5 ... Imaging element (CCD, CMOS), 13 ... AE processing circuit (brightness measurement means), 14 ... Scan AF processing circuit ( Focusing position detection means), 15... CPU (focusing position detection means), 24... Operation switch (instruction receiving means)

Claims (9)

An image sensor that photoelectrically converts a subject image formed by a photographing optical system to obtain an electrical image signal; and
Focus adjusting means for adjusting the focus of the subject image formed on the image sensor;
An in-focus position detecting means for detecting an in-focus position from an image signal generated by the image sensor while driving the focus adjusting means;
Have
The in-focus position is detected by using a fluctuation amount of the maximum value of the luminance signal and a fluctuation amount of the integrated value of the luminance signal, which are obtained from the image signal generated by the image sensor and are driven by the focus adjustment unit. A focus adjustment apparatus that determines whether or not a point light source subject is present within an area of the image sensor that acquires an image signal for the purpose. Brightness measuring means for measuring the brightness of a light beam incident from the photographing optical system;
The focus adjustment apparatus according to claim 1, wherein the determination is performed when the brightness of the light beam measured by the brightness measuring unit is darker than a predetermined value. When a point light source subject exists inside the area,
The in-focus position detection means detects the in-focus position using an image signal for detecting the in-focus position acquired when acquiring the maximum value and integrated value of the luminance signal for performing the determination. 3. The focus position is detected from the image signal generated by the image sensor while driving the focus adjustment unit again in the vicinity of the focus position obtained in step 1. The focus adjusting apparatus described. When a point light source subject exists inside the area,
4. The focus adjustment apparatus according to claim 3, wherein an interval between the plurality of drive positions of the focus adjustment unit in the second driving is smaller than an interval between the plurality of drive positions of the focus adjustment unit in the determination. Having instruction receiving means for receiving an instruction to start shooting preparation;
In the determination, before the instruction receiving unit is instructed to prepare for photographing, the luminance signal is detected at an interval coarser than the interval between the plurality of driving positions of the focus adjusting unit in the detection of the in-focus position by the in-focus position detecting unit. 5. The method according to claim 1, wherein a fluctuation amount of a maximum value and a fluctuation amount of an integrated value of the luminance signal are acquired and the preparation for photographing is instructed by the instruction receiving unit. 6. Focus adjustment device. The in-focus position detecting means detects the in-focus position acquired when the maximum value and integrated value of the luminance signal are acquired in order to make the determination after the preparation for photographing is instructed by the instruction receiving means. In the vicinity of the in-focus position obtained by detecting the in-focus position performed using the image signal, the in-focus position is determined from the image signal generated by the image sensor while driving the focus adjusting unit again. The focus adjusting apparatus according to claim 5, wherein the focus adjusting apparatus detects the focus. When no point light source subject exists within the area,
The in-focus position detecting means detects the in-focus position using an image signal for detecting the in-focus position acquired when acquiring the maximum value and the integrated value of the luminance signal for performing the determination. The focus adjusting apparatus according to any one of claims 1 to 4, wherein When the fluctuation amount of the maximum value of the luminance signal, which is obtained from the image signal generated by the imaging device, is smaller than a predetermined amount, and the fluctuation amount of the integrated value of the luminance signal is larger than the predetermined amount. The focus according to any one of claims 1 to 7, wherein it is determined that a point light source subject is present in an area of the image sensor that acquires an image signal for detecting the in-focus position. Adjustment device. The image generated by the image sensor is driven while driving a focus adjusting unit that adjusts the focus of the object image formed on the image sensor that photoelectrically converts the subject image formed by the photographing optical system to obtain an electrical image signal. A focus position detecting step for detecting a focus position from the image signal;
The in-focus position is detected by using a fluctuation amount of the maximum value of the luminance signal and a fluctuation amount of the integrated value of the luminance signal, which are obtained from the image signal generated by the image sensor and are driven by the focus adjustment unit. A determination step of determining whether or not a point light source subject is present within the area of the image sensor for acquiring an image signal for;
Have
The focus adjustment method, wherein the focus position detection step is performed in a different manner according to the determination result of the determination step.

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