JP2004334072A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus whose focus can efficiently be adjusted while unnecessary driving of a photography optical system is suppressed. <P>SOLUTION: When data showing the luminance in a focus area 94 of a photographed image are larger than a specified value, detailed search processing is carried out after rough search processing, but when not, only the detailed search process is performed without performing the rough search processing. Consequently, unnecessary lens driving can be suppressed to realize efficient focus adjustment. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image pickup apparatus, and more particularly to an image pickup apparatus having a function of adjusting a focus.
[0002]
[Prior art]
In recent years, many image pickup apparatuses, particularly digital cameras, equipped with an image pickup device such as a CCD have been distributed. In such a digital camera, at the time of shooting, a subject image is formed on the light receiving surface of the CCD, and the formed subject image is converted into signal charges of an amount corresponding to the amount of incident light by each sensor of the CCD. The signal charge accumulated in the CCD is read for each pixel and converted into image data, and this image data is recorded on a recording medium such as a memory card.
[0003]
Similar to the silver salt camera, this digital camera is known to have an autofocus function for automatically adjusting the focus with the subject. The autofocus function is a function for forming a subject image on an image sensor such as a CCD while moving a lens. For example, there is a method for performing this function, in which auto focus processing is performed by moving a lens from a predetermined initial position and setting a lens position at which the contrast value is maximum as a focus position. In the autofocus process, when the in-focus position is obtained by the maximum contrast value, the SN ratio of the contrast value is lowered and the in-focus position cannot be specified unless the subject is bright to some extent. For this reason, the lens movement may be repeatedly executed.
[0004]
In order to solve this problem, if the contrast value obtained from the difference between the maximum value and the minimum value of the luminance signal of the video signal is smaller than a predetermined threshold value, the lens drive is stopped and the autofocus operation is prohibited. A technique is known (for example, refer to Patent Document 1). As another technique, a technique for determining whether or not a subject has low brightness (low contrast) and determining that distance measurement is impossible when the brightness is low and prohibiting autofocus processing is known. (For example, refer to Patent Document 2).
[0005]
[Patent Document 1]
JP-A-6-67081 (pages 7-8, FIG. 1)
[Patent Document 2]
JP-A-8-43722 (pages 5-6, FIG. 1)
[0006]
[Problems to be solved by the invention]
However, in these techniques, the threshold value and the determination criterion have to be set high, and in the case of a low-contrast image (video signal), the autofocus itself is interrupted. The in-focus position could not be obtained.
[0007]
The present invention has been made to solve the above problems, and an object of the present invention is to provide an imaging apparatus capable of adjusting the focus efficiently while suppressing unnecessary driving of the photographing optical system.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, an image pickup apparatus of the present invention includes a light metering unit that measures a subject, and a driving unit that obtains a focus position by adjusting a focus on the subject by driving a photographing optical system by a predetermined driving amount. Setting means for setting a predetermined first driving amount or a second driving amount smaller than the first driving amount as the predetermined driving amount at the time of the focus adjustment, and a photometric value of the photometric means And a prohibiting unit that prohibits the setting of the first drive amount by the setting unit when it is less than a predetermined reference photometric value.
[0009]
The image pickup apparatus of the present invention includes a driving unit, and at the time of shooting, a photographing optical system including an imaging lens and the like is driven by a predetermined driving amount to adjust the focus on the subject and obtain a focus position. As an example of this focus adjustment, there is calculation of a contrast value, brightness, etc. at the position of each photographing optical system in which the photographing optical system is moved from a predetermined initial position. The in-focus position is obtained, for example, by setting the position of the photographing optical system where the calculated contrast value, brightness, etc. are the maximum value. In this case, the maximum and minimum differences and ratios of contrast values, and the amount of variation in brightness can be used.
[0010]
The setting means sets a predetermined driving amount when performing focus adjustment. The predetermined drive amount includes a first drive amount or a second drive amount smaller than the first drive amount. When the first drive amount or the second drive amount is set by the setting unit, the drive unit adjusts the focus by driving the imaging optical system by the first drive amount or the second drive amount to obtain a focus position. For this reason, when the second drive amount is set, more detailed focus adjustment of the photographing optical system is performed as compared with the case where the first drive amount is set. Therefore, for example, when the brightness of the subject is not sufficient, the in-focus position may not be obtained by driving with the first driving amount, and the in-focus position may be obtained by driving with the second driving amount.
[0011]
The photometric means measures the brightness of the subject, and the obtained data includes luminance data. The prohibiting unit prohibits the setting of the first drive amount by the setting unit when the photometric value of the photometric unit is less than a predetermined reference photometric value. The reference photometric value is a brightness threshold of the subject from which the in-focus position can be obtained by driving the imaging optical system for each first drive amount.
[0012]
Therefore, when the photometric value of the photometric means is less than a predetermined reference photometric value, the setting means can set only the second drive amount, and the drive for each first drive amount is not performed, and the drive for each second drive amount is performed. The in-focus position is obtained by driving the means. Therefore, useless lens driving can be suppressed, and efficient focus adjustment can be performed.
[0013]
The driving means can be driven by moving the lens position of the photographing optical system. Therefore, by moving the lens position of the imaging optical system such as the imaging lens, it is possible to obtain the in-focus position by adjusting the focus on the subject, so that the focus adjustment by a simple mechanism is possible.
[0014]
After setting the first drive amount in the setting unit and adjusting the focus with the first drive amount set in the drive unit, the setting unit sets the second drive amount and set in the drive unit. Further, a control means for adjusting the focus with the second drive amount can be further provided.
[0015]
The focus adjustment by the drive by the first drive amount by the drive means is coarser than the focus adjustment by the drive by the second drive amount. Therefore, in the image pickup apparatus of the present invention, when focus adjustment is performed, details are obtained by driving the second drive amount after obtaining an approximate focus position by rough focus adjustment by driving the first drive amount under the control of the control unit. An in-focus position can be obtained by performing a proper focus adjustment. For this reason, it becomes possible to obtain a highly accurate focus position efficiently.
[0016]
The photometric means includes a specific means for setting a specific area for measuring a part of the subject, and the setting means further sets the specific area in the photometric means so as to measure the specific area. Can do. When the specific area for metering a part of the subject is set by the specifying means, the setting means can further set the photometry means to measure the specific area, so that the photometry means can measure the specific area. can do. For this reason, for example, metering can be performed for a specific region intended by the user, so that metering can be performed efficiently.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a digital camera according to an imaging apparatus of the present invention will be described with reference to the drawings.
[0018]
FIG. 1 shows an example of a front view (A) and a rear view (B) of the appearance of the digital camera 10 according to the present embodiment.
[0019]
On the front surface of the housing 11 of the digital camera 10, a lens 12 for forming a subject image, a finder window 14, and a strobe light emitting unit 16 are provided. A shutter button 18 and a power switch 20 are disposed on the upper surface of the housing 11. A card slot 26 for mounting a memory card 24 is provided on the side surface of the housing 11. The shutter button 18 is configured in a two-stage manner, and the automatic focusing (auto focus) and automatic exposure processing (AE) are activated in a “half-pressed” state in which the shutter button 18 is lightly pressed and stopped to lock auto focus and AE. Then, shooting is executed in the state of “full press”, which is further pressed from “half press”. The power switch 20 is used when the user performs switching between supply / stop of supply of power to each part of the digital camera 10.
[0020]
A finder 28, an LCD (liquid crystal display device) 30, a zoom switch 32, a cross button 34, a menu button 38, an execution button 40, and a cancel button 42 are provided on the rear surface of the housing 11 of the digital camera 10. The LCD 30 can be used as an electronic viewfinder for checking the angle of view at the time of shooting, and displays various menu items, various selection items by the user, and a shot image.
[0021]
The menu button 38 is used when the user displays various menu items on the LCD 30. The cross button 34 is used when the user selects an arbitrary menu item from various menus displayed on the LCD 30. The execution button 40 is used when the user instructs the execution start of each item. The cancel button 42 is for operating when an instruction to cancel the item selected by the user is given. The zoom switch 32 is composed of a lever switch that can be operated in the vertical direction, and is operated when the user issues a zoom movement instruction in the telephoto (TELE) direction or a zoom movement instruction in the wide-angle (WIDE) direction. It is.
[0022]
FIG. 2 shows a main configuration of the digital camera 10 according to the present embodiment as a block diagram. The digital camera 10 includes a lens 12. The lens 12 includes a four-group inner focus zoom lens including a fixed lens 44, a variable power lens 46A, a correction lens 46B, and a focus lens 48. The variable magnification lens 46A and the correction lens 46B are provided so as to move along the optical axis while the positional relationship between them is regulated by a cam mechanism (not shown) so that the focal length can be changed. In the present embodiment, the variable power optical system including the variable power lens 46A and the correction lens 46B functions as the zoom lens 46.
[0023]
The light passing through the lens 12 is incident on the CCD 52 after the amount of light is adjusted by the diaphragm 50. Photosensors are arranged in a plane on the light receiving surface of the CCD 52, and the subject image formed on the light receiving surface of the CCD 52 via the lens 12 is converted into signal charges of an amount corresponding to the amount of incident light by each photosensor. Converted. The CCD 52 has a so-called electronic shutter function that controls the charge accumulation time (shutter speed) of each photosensor according to the timing of the shutter gate pulse.
[0024]
The signal charge accumulated in each photosensor is sequentially read out as a voltage signal (image data) corresponding to the signal charge based on a pulse given from the CCD driver 54. The image data output from the CCD 52 is sent to the analog processing unit 56. The analog processing unit 56 includes signal processing circuits such as a sampling hold circuit, a color separation circuit, and a gain adjustment circuit. The analog processing unit 56 performs correlated double sampling (CDS) processing and R, G, B color signals. Color separation processing is performed, and the signal level of each color signal is adjusted.
[0025]
The signal output from the analog processing unit 56 is converted into a digital signal by the A / D converter 58 and then stored in the memory 60. A timing generator (TG) 62 provides timing signals to the CCD driver 54, the analog processing unit 56, and the A / D converter 58 in accordance with instructions from the CPU 64, and the circuits are synchronized by this timing signal.
[0026]
The data stored in the memory 60 is sent to the signal processing unit 68 via the bus 66. The signal processing unit 68 is an image processing unit composed of a digital signal processor (DSP) including a luminance / color difference signal generation circuit, a gamma correction circuit, a sharpness correction circuit, a contrast correction circuit, a white balance correction circuit, and the like. Execute the process according to the command.
[0027]
The image data input to the signal processing unit 68 is converted into a luminance signal (Y signal) and a color difference signal (Cr, Cb signal) and is subjected to predetermined processing such as gamma correction and then stored in the memory 60. Is done. When the captured image is displayed and output, the image data is read from the memory 60 and transferred to the display memory 70. The data stored in the display memory 70 is converted into a predetermined signal for display and then output to the liquid crystal monitor (LCD) 30 via the D / A converter 72. For this reason, the image content of the image data is displayed on the screen of the LCD 30.
[0028]
When the user operates the zoom switch 32, the instruction signal is input to the CPU 64, and the CPU 64 controls the zoom drive unit 74 based on the signal from the zoom switch 32 to move the zoom lens 46 in the tele (TELE) direction or wide (WIDE). ) Move in the direction. The zoom driving unit 74 includes a motor (not shown), and the zoom lens 46 is driven by the driving force of the motor. The position (zoom position) of the zoom lens 46 is detected by a zoom position sensor 76, and a detection signal from the sensor 76 is input to the CPU 64.
[0029]
Similarly, the focus driving unit 78 includes a motor (not shown), and the focus lens 48 moves back and forth along the optical axis by the driving force of the motor. The position (focus position) of the focus lens 48 is detected by a focus position sensor 80, and a detection signal from the sensor 80 is input to the CPU 64.
[0030]
When an instruction to fully press the shutter button 18 is given, a shooting start instruction (release ON) signal is issued. The CPU 64 detects the release ON signal and executes a recording imaging operation. That is, the CPU 64 controls the focus drive unit 78 based on the result of evaluation value calculation described later to move the focus lens 48 to the in-focus position, and controls the aperture diameter of the diaphragm 50 and the electronic shutter of the CCD 52. Perform exposure control. Further, the CPU 64 sends a command to the strobe control circuit 82 as necessary to control the light emission of the slot light emitting unit 16.
[0031]
As described above, in response to the pressing operation of the shutter button 18, the capture of the image data is started. When the mode for compressing and recording image data is selected, the CPU 64 sends a command to the compression / decompression circuit 84. The compression / decompression circuit 84 compresses the image data taken into the memory 60 in accordance with JPEG or another predetermined format.
[0032]
The compressed image data is recorded on the memory card 24 via the card interface 86. When the mode for recording non-compressed image data (non-compression mode) is selected, the compression processing by the compression / decompression circuit 84 is omitted, and the image data is recorded on the memory card 24 without being compressed.
[0033]
The CPU 64 is a control unit that performs overall control of each circuit. The CPU 64 controls the operation of the corresponding circuit based on input signals input from the power switch 20, the shutter button 18, the zoom switch 32, and other operation units, and also performs display control on the LCD 30, auto focus processing, automatic exposure processing, and the like. I do.
[0034]
Here, the autofocus process will be described. The image data converted into a digital signal by the A / D converter 58 is stored in the memory 60 and input to the evaluation value calculation unit 88. The evaluation value calculation unit 88 includes a high frequency component extraction circuit 90 and an integration circuit 92. The evaluation value calculation unit 88 samples G component data in the input image data, and performs high frequency in an AF detection target area (hereinafter referred to as a focus area). A component is extracted and its absolute value is taken, and a value obtained by integrating the absolute value data in the focus area (hereinafter referred to as an evaluation value) is output to the CPU 64.
[0035]
In the present embodiment, it is assumed that the central area of the image 93 of the image data shown in FIG. 3A is set as the focus area 94 as the initial setting value. During the autofocus operation, the CPU 64 moves the focus lens 48 from infinity to close (or close to infinity) in the focus adjustment area, and at the center of the image at a plurality of AF detection points (hereinafter referred to as search points). The contrast is detected and an evaluation value is calculated. Then, by combining the evaluation values calculated at each point, the lens position where the evaluation value is maximum is determined as the in-focus position, and the focus driving unit 78 is moved so as to move the focus lens 48 to the obtained in-focus position. Control.
[0036]
As the focal length of the lens 12 increases, and as the aperture diameter of the diaphragm 50 increases, the depth of focus decreases, and the amount of lens driving from infinity to the nearest increases. FIG. 4 shows the relationship between the focal length of the lens 12 and the focus adjustment region 300. For example, an imaging lens 12 having a focal length that can be changed stepwise from 7 mm to 21 mm is used. As shown in FIG. 4, the focus adjustment region 300 by the focus lens 48 becomes wider as the focal length of the lens 12 becomes longer. For example, when the focal length is 7 mm, the movable range of the focus lens 48 from infinity to the nearest distance is 8.17 μm, and the focus adjustment region 300 when the focal length is 21 mm is 735 μm.
[0037]
The CPU 64 sets an AF step width 302 indicating the width of the lens position (search point) for calculating the evaluation value and the number of step steps (number of detection points) in accordance with the focus adjustment region 300 that varies according to the focal length of the lens 12. Set.
[0038]
This step step number may be obtained by equally dividing the focus adjustment region 300 at each focal length by the AF step width 302, or by reducing the AF step width 302 on the near distance (closest limit) side to be shorter than the infinity side. It may be set to increase the focus accuracy by increasing the search points on the distance side.
[0039]
In order to obtain the in-focus state, first, an AF search is executed from infinity to the closest position, and an evaluation value is acquired at each point. When the evaluation value starts to decrease beyond the peak of the evaluation value and a predetermined condition is satisfied, the AF search is interrupted. The peak of the evaluation value may be detected, for example, as the peak of the evaluation value before the decrease in the case where the obtained evaluation value continues to decrease twice. Then, the focus lens 48 is moved to a focus position (focus position) corresponding to the detected peak to obtain a focused state.
[0040]
However, as the focal length of the lens 12 increases, the amount of movement (number of pulses) of the focus lens 48 in the focus adjustment region 300 (from infinity to close) increases, so the autofocus time increases. Therefore, when a rough search process is first performed to obtain an evaluation value in the AF search step with an increased focus movement amount, and an approximate focus position is detected by the rough search process, a region near the detected approximate focus position is detected. Further, a technique for performing a detailed search process for acquiring an evaluation value in a search step in which the focus movement is further reduced is known.
[0041]
FIG. 5 shows a conceptual diagram of rough search processing and detailed search processing. In this embodiment, the amount of focus movement from infinity to the nearest is 240 pulses, the number of focus feed pulses during rough search processing is 20 pulses, and the number of focus feed pulses during detailed search processing is set to 2 pulses. And Note that the number of pulses in the rough search process and the detailed search process is not limited to the above values, but may be any value as long as the number of pulses in the rough search process is larger than the number of pulses in the detailed search process.
[0042]
According to FIG. 5, first, the rough search process is started from infinity to the closest direction. In the rough search process, the search point is changed every 20 pulses, the evaluation value is calculated at each point, and the peak detection process is performed. In the rough search process, when the evaluation value continuously decreases a predetermined number of times, it is determined that a peak has been detected, and the focus is moved to the initial position (Pds) of the detailed search. Then, the detailed search process is started in the infinity direction from the initial position. In the detailed search process, the search point is changed every two pulses, and the evaluation value is calculated at each point. If the evaluation value decreases continuously a predetermined number of times, it is determined that the peak is detected, and the focus lens 48 is set at the peak (focus position). Drive. In the rough search process, if a peak is not detected even if the search point is changed from infinity to the nearest point, the rough search process is interrupted and the detailed search process is started.
[0043]
However, in the above technique, in the rough search process, the rough search process is unconditionally executed even in a situation where a clear peak is not detected such that the brightness of the subject is lower than a predetermined value and the brightness of the focus area 94 is extremely low. Subsequently, a detailed search is subsequently performed. In other words, since no peak is detected, the detailed search is executed after the rough search process is executed from infinity to the closest direction, and the time required for the rough search process is increased, and the time required for the entire autofocus process is increased. There is a problem of becoming.
[0044]
For this reason, the digital camera 10 of the present invention further includes a photometry unit 89. The photometry unit 89 is for measuring the brightness of the subject, and the brightness of the focus area 94 (hereinafter referred to as subject brightness) of the photographed image obtained by photographing with the CCD 52 is stored in the image data stored in the memory 60. Detection is based on the luminance signal Y, and data indicating the subject luminance is output to the CPU 64. In the present embodiment, a case where data indicating subject brightness is output to the CPU 64 will be described, but data indicating subject brightness may be used.
[0045]
When the user gives an instruction to half-press the shutter button 18, the subject brightness is detected by the photometry unit 89 from the image data stored in the memory 60, and data indicating the subject brightness is output to the CPU 64. The CPU 64 executes autofocus processing based on data indicating the subject luminance input from the photometry unit 89 (details will be described later).
[0046]
In the memory 60, data indicating the brightness of the limit focus area 94 where the peak can be detected in the rough search process is stored in advance as a predetermined value. This predetermined value corresponds to the reference photometric value of the imaging apparatus of the present invention. The predetermined value stored in advance in the memory 60 is obtained by executing a rough search process under various brightness conditions by the digital camera 10 in advance, measuring data indicating luminance at which a peak can be detected in the rough search process, What is necessary is just to calculate and memorize | store the predetermined value of the limit which can detect a peak according to a measurement result.
[0047]
The photometry unit 89 corresponds to the photometry unit of the imaging apparatus of the present invention, and the zoom lens 46 corresponds to the drive unit of the present invention.
[0048]
Hereinafter, the operation of the digital camera 10 of the present embodiment will be described. FIG. 6 shows a processing routine executed by the CPU 64.
[0049]
When power is turned on to the digital camera 10 by the power switch 20, the process proceeds to step 100, and negative determination is repeated until a half-press instruction is given. The determination in step 100 can be made by determining signal reception indicating a “half-pressed” state in which the user presses the shutter button 18 lightly and stops.
[0050]
If the determination in step 100 is affirmative, the process proceeds to step 102, where focus area setting processing is executed. For example, as shown in FIG. 3B, the photographed image is divided into 8 × 8 64 blocks of equal area, and a predetermined plurality of blocks in the central portion are set as the focus area 94 to be evaluated. In the present embodiment, a predetermined plurality of blocks in the center portion are set in the focus area 94.
[0051]
Next, in step 104, photometric processing is executed. The processing in step 104 is to obtain data indicating the subject brightness from the photometry unit 89. By the processing in step 102, data indicating the brightness of the focus area 94 of the captured image is obtained. In the present embodiment, data indicating the brightness of the focus area 94 at the center of the captured image is obtained.
[0052]
Next, in step 106, it is determined whether or not the data indicating the subject brightness obtained in step 104 is a predetermined value or more. The determination in step 106 is performed by reading a predetermined value stored in advance in the memory 60 and comparing it with data indicating the subject brightness obtained in step 104.
[0053]
If the determination in step 106 is affirmative, the process proceeds to step 108, and rough search processing is executed for the focus area 94 set in step 102. As described above, by rough search processing, for example, rough search processing is started from infinity to the closest direction, search points are changed every 20 pulses, evaluation values are calculated at each point, and peak detection processing is executed. The By the process of step 108, an approximate in-focus position in the focus area 94 is detected.
[0054]
Next, in step 110, a detailed search process is executed. In the detailed search process, the search point is changed every two pulses from the initial position (Pds) to the infinity direction in the vicinity region of the approximate focus position detected by the rough search process in step 108. Then, the evaluation value is calculated at each point, and when the evaluation value continuously decreases a predetermined number of times, it is determined that the peak is detected, and the focus lens 48 is driven to the peak position (focus position).
[0055]
In the detailed search process in step 110, if no peak is detected in the focus area set in step 102, the focus area may be changed sequentially to detect the peak in the changed focus area. In this case, as shown in FIG. 3B, a plurality of focus areas (94A, 94B, 94C, 94D) are set in advance for a plurality of blocks in a predetermined area, and priorities are assigned to the set areas, The information is stored in advance in the memory 60 in association with information indicating each area. If no peak is detected in the focus area set in step 102, information indicating the area is sequentially read from the memory 60 according to the priority order, the focus area is changed to the area, and the detailed search process is performed. do it.
[0056]
Further, when the focus area is sequentially changed and the peak detection is not performed for the entire area of the photographed image, the maximum evaluation value of the evaluation value calculated in each focus area is compared, and the value of each maximum evaluation value is compared. When the two match each other, the matching maximum evaluation value may be a peak.
[0057]
On the other hand, if the determination in step 106 is negative, the process proceeds to step 114, and the detailed search process is executed in substantially the same manner as in step 110. In step 114, a detailed search process is executed for the focus area 94 set in step 102, and the search point is changed every two pulses from the infinity direction to the close direction or from the close direction to the infinity direction. The focus lens 48 is driven to the peak (focus position) according to the evaluation value of each point.
[0058]
In the detailed search process in step 114, if no peak is detected in the focus area set in step 102, the focus area is sequentially changed and the peak in the changed focus area is detected in the same manner as in step 110. You just have to do it.
[0059]
Next, in step 116, it is determined whether or not a full-press instruction has been issued. If the determination is negative, this routine is terminated. The determination in step 116 can be made by determining the reception of a signal indicating the state of the shutter button 18 being “fully pressed” by the user.
[0060]
If the determination in step 116 is affirmative, the routine proceeds to step 118, and after the photographing process is executed, this routine is terminated. The process of step 118 is to obtain a photographed image by driving the focus lens 48 to the peak position (focus position) by the detailed search process of step 110 or step 114 when photographing a subject.
[0061]
As described above, in the present embodiment, in the focus adjustment (autofocus) process of the digital camera 10, when the data indicating the brightness of the focus area 94 of the photographed image is equal to or greater than a predetermined value, details are provided after the rough search process. When the search process is executed and the value is less than the predetermined value, only the detailed search process can be executed without performing the rough search process, so that useless lens driving can be suppressed. Therefore, it is possible to efficiently perform autofocus processing while suppressing unnecessary driving of the focus lens 48. Further, it becomes possible to suppress the consumption of the power supply battery in the autofocus process.
[0062]
Note that the processing in step 104 corresponds to the function of the photometry unit of the imaging apparatus of the present invention, and the processing of step 108, step 110, and step 114 corresponds to the function of the setting unit of the present invention. Further, the processing in step 106 corresponds to the function of the prohibiting means of the image pickup apparatus of the present invention. Further, the processing from step 108 to step 110 corresponds to the function of the control means of the present invention, and the processing of step 102 corresponds to the function of the specifying means of the present invention.
[0063]
【The invention's effect】
As described above, according to the imaging apparatus of the present invention, when the photometric value obtained by photometry of the subject is less than the predetermined reference photometric value, the focus adjustment by driving each of the first drive amount larger than the second drive amount is prohibited. In addition, since only the focus adjustment by the drive for each second drive amount can be executed, it is possible to obtain an effect that the focus adjustment can be performed efficiently while suppressing unnecessary driving of the photographing optical system.
[Brief description of the drawings]
FIG. 1A is a front view of a digital camera according to the present embodiment, and FIG. 1B is a rear view of the digital camera according to the present embodiment.
FIG. 2 is a block diagram illustrating a schematic configuration of a digital camera.
FIG. 3A is a schematic diagram showing an example of a focus area set at the center of an image, and FIG. 3B shows a case where a focus area is set by dividing an image into a plurality of blocks. It is a schematic diagram which shows an example.
FIG. 4 is a diagram illustrating a change in an autofocus search step width according to a zoom position and a focus position.
FIG. 5 is a conceptual diagram of autofocus processing in which rough search processing and detailed search processing are combined.
FIG. 6 is a processing routine showing an autofocus process of the digital camera of the present embodiment.
[Explanation of symbols]
10 Digital camera
89 Metering unit

Claims (4)

A metering means for metering the subject;
Driving means for adjusting the focus on the subject to obtain the in-focus position by driving the photographing optical system by a predetermined driving amount; and
Setting means for setting a predetermined first driving amount or a second driving amount smaller than the first driving amount as the predetermined driving amount when the focus is adjusted;
Prohibiting means for prohibiting setting of the first drive amount in the setting means when the photometric value of the photometric means is less than a predetermined reference photometric value;
An imaging apparatus comprising: The imaging apparatus according to claim 1, wherein the driving unit is driven by moving a lens position of the photographing optical system. After the setting unit has the first driving amount set and the focus is adjusted by the first driving amount set by the driving unit, the setting unit sets the second driving amount and sets the driving unit. The image pickup apparatus according to claim 1, further comprising a control unit that adjusts a focus with the second driving amount. The photometric means includes a specific means for setting a specific area for measuring a part of the subject, and the setting means further sets the specific area in the photometric means so as to measure the specific area. The imaging device according to any one of claims 1 to 3, wherein

Images