JP2003289469A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of properly displaying an object image on a display means while quickly performing automatic focus control. <P>SOLUTION: A digital camera uses a CCD to acquire image data of an object. The CCD has an ordinary mode wherein all pixels of image data are outputted at 60 fps and an area limit mode wherein areas including a focus area limited in the image data are outputted at 180 fps as output modes of the image data. The ordinary mode is selected in a live view operation for the output mode of the CCD21 and the area limit mode and the ordinary mode are switched for a period of 1/60 seconds in automatic focus control. While the output mode of the CCD is set to the area limit mode, a state of a display screen of a liquid crystal monitor is maintained. Thus, an object image is properly displayed on the display screen of the liquid crystal display monitor while quickly performing automatic focus. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus control technique for an image pickup apparatus.

[0002]

2. Description of the Related Art Conventionally, a so-called contrast method is used in an image pickup apparatus such as a digital still camera (hereinafter, simply referred to as "digital camera") or a video camera which obtains image data using an image pickup device such as CCD. The technique called (or also called hill climbing method) is applied to autofocus control. The contrast method is a method in which the contrast of image data obtained in each driving step is acquired as an evaluation value while driving the focus lens, and the lens position having the highest evaluation value is set as the focus position.

Further, in an image pickup apparatus provided with a display means such as a liquid crystal monitor, image data is acquired at fixed time intervals in a photographing standby state, and a subject image is displayed on the display means based on the obtained image data. The view is displayed. With such a live view display, the user can perform framing while confirming a subject image having no parallax.

[0004]

By the way, in recent years, it has been demanded to improve the operation speed of the autofocus control in the image pickup apparatus. Generally, the evaluation value is obtained from a predetermined focus area, which is a limited area in which the main subject image in the image data is highly likely to exist, so image data including the focus area is obtained in order to perform autofocus control. It should be done. When the area of the image data output from the image sensor is limited, the image data can be acquired at a relatively high frame rate. From these things, it is expected that the speed of the autofocus control operation will be improved by outputting the image data including at least the focus area in which the area is limited.

However, when the image data of which the area is limited is output from the image pickup device, there arises a problem that the entire subject image cannot be displayed on the display means such as a liquid crystal monitor.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an image pickup apparatus capable of appropriately displaying a subject image on a display means while rapidly performing focus control.

[0007]

In order to solve the above-mentioned problems, the invention of claim 1 is an image pickup apparatus, wherein image data of a subject is acquired through an optical system and the image data is output. A first output mode for outputting first image data relating to the entire area of the image data as an output mode;
An image pickup unit having a second output mode for outputting second image data including at least a predetermined focusing target area in the image data faster than the first output mode; and the focusing target area in the image data. Focus control means for performing focus control of the optical system based on the above, display means for displaying a subject image on a display screen based on the first image data, and image pickup means when the focus control means performs focus control. The output mode of the image pickup control means for setting the output mode to the second output mode, and the state of the display screen of the display means on which the subject image is displayed when the output mode of the image pickup means is set to the second output mode. And a display control means for holding the display control means.

According to a second aspect of the present invention, in the image pickup apparatus according to the first aspect, the image pickup control unit sets the output mode of the image pickup unit to the first mode when the focus control unit performs focus control. It is characterized in that the output mode and the second output mode are switched at a predetermined cycle.

According to a third aspect of the present invention, in the image pickup apparatus according to the second aspect, there is further provided an acceptance unit that accepts an instruction to start focus control of the optical system, and the imaging control unit is the acceptance unit. In response to an instruction to start the focus control, the output mode of the image pickup unit is switched between the first output mode and the second output mode at a predetermined cycle.

According to a fourth aspect of the present invention, in the image pickup apparatus according to the second aspect, the image pickup apparatus further comprises a determination means for determining whether or not the position of the optical system is near the in-focus position. The control means, in response to the determination means determining that the position of the optical system is near the in-focus position, sets the output mode of the imaging means to the first output mode and the second output mode. And is switched at a predetermined cycle.

According to a fifth aspect of the present invention, in the image pickup apparatus according to the second aspect, the image pickup control means further includes a display switching means for switching the state of the display means between display and non-display. , When the display means is in the display state,
The output mode of the image pickup means is switched between the first output mode and the second output mode at a predetermined cycle, and when the display means is in the non-display state, the output mode of the image pickup means is changed to the first output mode. It is characterized in that it has a two-output mode.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will now be described in detail with reference to the drawings. In the following description, a digital camera will be described as an example of the imaging device.

<1. First Embodiment><1-1. Configuration of Digital Camera> First, the configuration of the digital camera 1 will be described. Figure 1 shows a digital camera 1
2 is a perspective view showing the structure of the digital camera 1 and FIG.

As shown in FIG. 1, on the front side of the digital camera 1, there are provided a taking lens 3, a flash 23 and an objective window of an optical finder 22. Shooting lens 3
Has a plurality of lens groups including a focus lens 31 (see FIG. 3) that determines the in-focus state of the subject image. A CCD 21, which is an image pickup device that acquires image data of a subject through a lens group, is provided at a proper position inside the digital camera 1 behind the taking lens 3.

On the upper surface side of the digital camera 1, a shutter button 25 and a main switch 24 for switching on / off of a power source are arranged. Shutter button 2
Reference numeral 5 denotes a button for accepting a start of autofocus control and a shooting instruction from the user, which is a two-step switch capable of detecting a half-pressed state (S1 state) and a fully-pressed state (S2 state). Further, a card slot 26 for mounting a memory card 9 which is a recording medium for recording image data and the like is formed on the side surface of the digital camera 1, and the replaceable memory card 9 can be mounted.

On the other hand, as shown in FIG. 2, on the back side of the digital camera 1, an eyepiece window of the optical finder 22, a mode switching lever 27 for switching the operation mode, a liquid crystal monitor 28 for performing various displays and various operations. A button group 29 for performing is provided.

The digital camera 1 has, as its operation modes, a "shooting mode" for acquiring image data of a subject,
It has a "reproduction mode" for reproducing and displaying the recorded image data, and these operation modes are switched by operating the mode switching lever 27.

The liquid crystal monitor 28 displays the acquired image data and the image data recorded in the memory card 9, and also displays a menu screen for making various settings of the digital camera 1. In the shooting standby state, the image data acquired by the CCD 21 is continuously displayed on the liquid crystal monitor 28 at regular intervals (live view display), and the user performs framing while confirming the displayed subject image. Has been made possible. At the time of this live view display, a frame 28a indicating a predetermined focus area which is a focusing target area is displayed. The user can bring the desired subject image into a focused state by performing framing so that the desired subject image is arranged in the frame 28a.

The button group 29 includes display switching buttons 29.
A, a left button 29b, a right button 29c and a menu button 29d are included.

The display switching button 29a is a button for setting whether or not to display the liquid crystal monitor 28 in the shooting standby state, and the state of the liquid crystal monitor 28 is switched between display and non-display each time the button is pressed. .

The left button 29b, the right button 29c and the menu button 29d are mainly buttons for making various settings of the digital camera 1. Menu button 29
By pressing d, a menu screen is displayed on the liquid crystal monitor 28, and while confirming this menu screen, the left button 29b
By operating the and right buttons 29c, various settings can be made.

<1-2. Internal Configuration of Digital Camera> Next, the internal configuration of the digital camera 1 will be described. FIG. 3 is a diagram showing a main internal configuration of the digital camera 1 as functional blocks.

The CCD 21 is composed of a light receiving section for exposing and accumulating signal charges, a vertical transfer section for transferring and outputting the signal charges, a horizontal transfer section and an output section. The light receiving unit has a plurality of pixels to which R (red), G (green), and B (blue) color filters are attached, and an optical image of the subject formed by the lens group of the taking lens 3. Are photoelectrically converted into signal charges (image data). The signal charge accumulated in the light receiving section is once transferred to the vertical transfer section, and then transferred to the horizontal transfer section for each line (column of horizontal pixels) and sequentially output from the output section.

The CCD 21 outputs the image data in the "normal mode" in which all the pixels of the image data are output.
And an "area limitation mode" for outputting an area including a limited focus area in the image data.

4 and 5 are views showing the image data 60 acquired by the CCD 21. As shown in these figures, the focus area FA, which is the focus target area, is assigned to the substantially central portion in the image data 60 where the main subject image is likely to exist.

When the CCD 21 is set to the normal mode,
As shown in FIG. 4, all pixels of the image data 60 are the normal image 6
It is output as 1. On the other hand, when the CCD 21 is set to the area limited mode, the signal charges in the upper and lower areas 63 in the image data 60 are swept out as unnecessary charges, and as shown in FIG. The limited image 62 is output. The area limited image 62 has a smaller number of lines to be transferred and output than the normal image 61. Therefore, when the CCD 21 is set to the area limited mode, the image data for each frame can be output at a higher speed than when the CCD 21 is set to the normal mode.
The number of image data to be output per unit time, that is, the frame rate (unit: fps) can be increased.

Here, the cycle in which the CCD 21 outputs the normal image 61 in the normal mode (the reciprocal of the frame rate)
Is T1 and the period for outputting the region limited image 62 in the region limited mode is T2, the period T1 and the period T2 are as follows: T1 = n · T2 (where n is a natural number of 2 or more) (1) That is, the period T1 is equal to the period T
It is preferably a natural number multiple of 2. In the present embodiment, the cycle T1 is 1/60 seconds and the cycle T2 is 1/180.
It is set to seconds (n = 3). That is, the CCD 21
Will output the normal image 61 at a frame rate of 60 fps in the normal mode, and will output the region limited image 62 at a frame rate of 180 fps in the region limited mode.

Returning to FIG. 3, the timing generator 20
1 is CC based on the signal input from the overall control unit 40.
Various drive control signals are transmitted to D21. For example, a vertical synchronization signal for transferring the signal charge accumulated in each pixel of the CCD 21 to the vertical transfer unit, a horizontal synchronization signal for transferring the signal charge for one line from the vertical transfer unit to the horizontal transfer unit, and an unnecessary charge of each pixel An unnecessary charge sweep signal for sweeping, an output mode switching signal for switching the output mode to the normal mode or the area limited mode, and the like are transmitted. Therefore, the output mode of the CCD 21 is switched and controlled by the timing generator 201.

The signal processing circuit 202 subjects the image data (analog signal) output from the CCD 21 to predetermined analog signal processing. The signal processing circuit 202 has a C
A DS (correlated double sampling) circuit and an AGC (auto gain control) circuit are provided inside the CDS circuit to reduce noise in the image data, and the AGC circuit adjusts the level of the image data.

The A / D converter 203 is a signal processing circuit 20.
The image data of the analog signal output from 2 is converted into a digital signal. The value of each pixel output from the A / D converter 203 is expressed as a color component value of a color composed of RGB color components.

The image memory 204 includes an A / D converter 203.
It is a memory for storing the image data output from, and has a storage capacity capable of storing at least one frame of the normal image 61.

The image processing unit 205 corrects the white balance of the image data stored in the image memory 204.
Predetermined image processing such as γ correction, resolution conversion, and compression processing is performed.

Further, the VRAM 210 is a liquid crystal monitor 28.
Is a buffer memory for storing image data to be displayed on the display screen.

In the photographing standby state, the cycle T1 (1/60
The image data (normal image 61) output from the CCD 21 in a second is the signal processing circuit 202 and the A / D converter 20.
Predetermined signal processing is performed at 3 and stored in the image memory 204. Then, the image processing unit 205 thins out the pixels at a predetermined interval to form a live view image, and the VRAM 2
Stored in 10. The live view image stored in the VRAM 210 is read by the overall control unit 40 at a predetermined cycle, converted into a video signal, and transmitted to the liquid crystal monitor 28. As a result, the subject image is displayed on the display screen of the liquid crystal monitor 28 (live view display). The refresh rate (the number of times the display screen is rewritten per unit time) of the liquid crystal monitor 28 is set to 60 fps so as to match the frame rate at which the CCD 21 outputs the normal image 61. That is, the live view image stored in the VRAM 210 is transmitted to the liquid crystal monitor 28 every 1/60 seconds. Therefore, on the display screen of the liquid crystal monitor 28, C
The image data obtained on the CD 21 is sequentially and smoothly displayed. The area limited image 62 is not image data showing the entire area of the subject image, and therefore cannot be used for such live view display.

On the other hand, the image data (normal image 61) output from the CCD 21 as the image data for recording after the photographing instruction by the shutter button 25 is similarly supplied to the signal processing circuit 202 and the A / D converter 203. Then, predetermined signal processing is performed and stored in the image memory 204. Then, the image processing unit 205 performs compression processing by the JPEG method or the like to form a compressed image, and then the card I / F 206
Is recorded on the memory card 9 via the.

The image data output from the CCD 21 in the shooting standby state is also input to the AF calculation unit 207 and the brightness calculation unit 208 and used for exposure control and focus control.

The AF calculation unit 207 uses the image data of both the normal image 61 and the area-limited image 62 to derive the focus evaluation value used for autofocus control. Specifically, the pixel in the focus area in the image data is used as the calculation target, and the contrast value is obtained from the pixel in this focus area and used as the focus evaluation value.
The obtained focus evaluation value is input to the overall control unit 40.

Further, the brightness calculation unit 208 uses the normal image 61.
Is used to derive the brightness value of the subject used for exposure control. Specifically, the brightness component value of the pixel in the input image data is obtained, and the average value of the obtained brightness component values in all the pixels is obtained as the brightness value of the subject. The obtained brightness value of the subject is input to the overall control unit 40.

The lens driving section 209 drives the focus lens 31 in the taking lens 3, the diaphragm in the taking lens 3 which determines the amount of incident light, and the like. The lens driving unit 209 is electrically connected to the overall control unit 40, and drives the focus lens 31 and the like of the taking lens 3 based on a signal input from the overall control unit 40.

The operation input section 20 shows an operation member including the shutter button 25, the main switch 24, the mode switching lever 27, the button group 29 and the like as one functional block. The operation of the operation input unit 20 is input as a signal to the overall control unit 40.

The overall control unit 40 controls the operations of the above-mentioned members of the digital camera 1 in a centralized manner, and includes a CPU 41 for performing various arithmetic processes, a RAM 42 serving as a work area for performing arithmetic operations, and a control. A ROM 43 in which programs and the like are stored is provided.

Various functions of the overall control unit 40 are stored in the ROM 4
This is realized by the CPU 41 performing arithmetic processing according to the control program stored in 3. Such a control program is stored in the ROM 43 in advance, but a new control program can be stored in the ROM 43 by reading it from the memory card 9 or the like. In FIG. 3, the exposure control unit 51, the display control unit 52, and the AF control unit 53 schematically represent, as functional blocks, some of the functions realized by the CPU 41 performing arithmetic operations according to the control program.

The exposure control unit 51 controls the exposure. Specifically, the shutter speed (corresponding to the charge accumulation time of the CCD 21) and the aperture value (corresponding to the aperture diameter of the diaphragm) are determined based on the brightness value of the subject and a predetermined program diagram input from the brightness calculation unit 208. Then, a signal is transmitted to the timing generator 201 and the lens drive unit 209 so that the shutter speed and aperture value are determined. When the subject has low brightness and insufficient exposure, the signal processing circuit 202 is caused to adjust the level of the image data output from the CCD 21 to correct the inappropriate exposure due to insufficient exposure.

The display control section 52 controls the state of the display screen of the liquid crystal monitor 28, and reads the image data (live view image or the like) stored in the VRAM 210 at a predetermined cycle and converts it into a video signal. LCD monitor 28
Send to. Further, a predetermined menu screen is displayed on the liquid crystal monitor 28 according to the operation of the menu button 29d, and the state of the liquid crystal monitor 28 is switched between display and non-display according to the operation of the display switching button 29a. Also controls.

The AF control unit 53 monitors the focus evaluation value input from the AF calculation unit 207 and adjusts the focus lens in the taking lens 3 so that the subject image in the focus area in the image data is in focus. Auto focus control for driving 31 is performed. AF control unit 53
Controls the drive of the focus lens 31 by transmitting a predetermined signal to the lens driving unit 209.

FIG. 6 shows the lens position (focus lens 3
It is a figure which shows an example of the relationship between the focus evaluation value (contrast) and the position (1). As shown in the figure, the focus evaluation value changes depending on the lens position, and has a maximum value at any lens position. The AF controller 53
The lens position where this evaluation value is the maximum value is obtained as the focus position FP, and the focus lens 31 is moved to this focus position FP.

Specifically, assuming that the lens position before autofocus control (hereinafter referred to as "initial position") is the position indicated by reference numeral IP, first, the focus lens 31 is slightly driven from the initial position IP. (Arrow AR1), the magnitude of the evaluation value obtained at each of the plurality of positions of the focus lens 31 is determined. The drive direction of the focus lens 31 is determined from the determination result of this evaluation value, and the focus lens 3 is moved in the determined drive direction (direction of arrow AR2).
1 is driven at a relatively high speed. Then, the evaluation values sequentially obtained during this driving are monitored, and it is determined whether or not the monitored evaluation values have decreased.

When the evaluation value decreases (arrow AR3),
The lens position passes the focus position FP and the focus position F
Since it is in the vicinity of P, the drive direction of the focus lens 31 is switched to the opposite direction (direction of arrow AR4) to drive the focus lens 31. After the lens position is near the in-focus position FP, the focus lens 31 is driven at a relatively low speed. In order to adjust the focus lens 31 to the focus position FP with high accuracy,
This is because it is necessary to obtain a change in evaluation value due to a minute difference in lens position. After that, while switching the drive direction of the focus lens 31 as needed (arrow AR5), the focus evaluation value is monitored, and the focus lens 31 is finally moved to the position FP where the evaluation value becomes the maximum value. Let

Further, the AF control section 53 sends a switching instruction signal for switching the output mode of the CCD 21 to the timing generator 201 in order to speedily perform the autofocus control operation.
The details will be described later.

<1-3. Overview of digital camera operation>
Next, the operation of the digital camera 1 in the shooting mode will be described. FIG. 7 is a diagram showing an outline of the operation of the digital camera 1 in the shooting mode.

When the digital camera 1 is set in the photographing mode, it is in a photographing standby state, and the CCD 21 is set to 60 fp.
A live view operation for displaying the image data output in s on the liquid crystal monitor 28 is performed.

First, the output mode of the CCD 21 is set to the normal mode for outputting the normal image 61 (step ST
11). Subsequently, exposure for the live view image is performed in the CCD 21 (step ST12), and the normal image 61 is output (step ST13). The output normal image 61 is subjected to predetermined processing by the signal processing circuit 202 to the image processing unit 205 to be a live view image, and then displayed on the liquid crystal monitor 28 (step ST14).

On the other hand, the normal image 61 is displayed in the brightness calculation unit 2
It is also input to 08 to derive the brightness value of the subject. The derived brightness value of the subject is input to the overall control unit 40,
The exposure control unit 51 determines the shutter speed and the aperture value based on the brightness value (step ST1).
5).

The above-described operation of steps ST12 to ST15 (live view operation) is 1/6 until the shutter button 25 is pressed halfway (No in step ST16).
It is repeated every 0 seconds. That is, the normal image 61 is C
It is output from the CD21 at a cycle of 1/60 seconds, and VRAM2
The live view image stored in 10 is also updated at a cycle of 1/60 seconds.

When the shutter button 25 is half-depressed in such a shooting standby state (Yes in step ST16), the AF controller 53 performs autofocus control in response to the half-depression of the shutter button 25. ,
The focus lens 31 is moved to the focus position FP (step ST17).

When the autofocus control is completed, the shutter button 25 is fully pressed (step ST18). Then, when the shutter button 25 is fully pressed, the output mode of the CCD 21 is set to the normal mode for outputting the normal image 61 (step ST19).
Exposure for recording is performed in the CCD 21 (step S
T20) The normal image 61 is output (step ST2)
1). The output normal image 61 is the signal processing circuit 202.
~ After the image processing unit 205 performs a predetermined process to form a compressed image, it is recorded in the memory card 9 (step S
T22).

After the end of photographing or the shutter button 2
If there is no full-press after the half-press of 5 (No in step ST18), the step ST12 is executed again.
Then, the camera returns to the standby state for shooting.

<1-4. Autofocus control> Next,
Autofocus control operation of the digital camera 1 (FIG. 7:
Details of step ST17) will be described. 8 to 10 are diagrams showing the flow of the autofocus control operation.

In the digital camera 1, the method of autofocus control differs depending on the brightness of the subject. Therefore, when performing the autofocus control, the AF control unit 53 determines whether or not the brightness value of the subject input from the brightness calculation unit 208 is equal to or larger than a predetermined reference value (step ST31). Then, when the brightness value of the subject is equal to or larger than the predetermined reference value, the operation after step ST32 is performed, and when it is less than the predetermined reference value, step ST5 of FIG.
Operations after 1 are performed.

Further, in the digital camera 1, when the brightness value of the subject is equal to or larger than a predetermined reference value, the method of autofocus control is different depending on whether the state of the liquid crystal monitor 28 is display or non-display. Therefore, when the brightness value of the subject is equal to or greater than the predetermined reference value, the AF control unit 53 further determines whether the state of the liquid crystal monitor 28 is display or non-display based on the signal from the display control unit 52. Is determined (step ST32). Then, when the liquid crystal monitor 28 is in the display state, the operation after step ST33 is performed, and when it is not displayed, the operation after step ST61 in FIG. 10 is performed.

The operation of the autofocus control (step ST33 and thereafter) when the brightness value of the subject is equal to or greater than a predetermined reference value and the state of the liquid crystal monitor 28 is display will be described below.

First, the internal counter C is initialized to "0".
Is set (step ST33). The internal counter C indicates the number of times the focus evaluation value is derived (= the number of exposures of image data for deriving the evaluation value) during autofocus control. In this autofocus control, the processes of steps ST35 to ST44 are repeated until the lens position reaches the in-focus position (No in step ST45), but the internal counter C is executed before each of these series of processes. Is incremented (step ST34).

Next, the internal counter C is a multiple of 4 (C = 4
It is determined whether or not k and k are natural numbers (step ST35).

When the internal counter C is a multiple of 4 (No in step ST35), the CCD from the signals from the AF controller 53 and the timing generator 201 is used.
The output mode 21 is set to the normal mode. That is, similarly to the live view operation, the setting for outputting the normal image 61 in 1/60 seconds is made (step ST36).

Subsequently, the CCD 21 is exposed (step ST37), and the CCD 21 outputs the normal image 61 (step ST38). Similarly to the above, the output normal image 61 is subjected to predetermined processing in the signal processing circuit 202 to the image processing unit 205 to be a live view image and stored in the VRAM 210, and then the liquid crystal monitor 2
8 is displayed. That is, the live view image stored in the VRAM 210 is updated (step ST3).
9).

At the same time, the normal image 61 is also input to the AF calculation unit 207, and the focus evaluation value is derived (step ST43). The derived evaluation value is input to the overall control unit 40, and the AF control unit 53 is based on this evaluation value.
Thus, the drive of the focus lens 31 is controlled (step ST44).

On the other hand, when the internal counter C is not a multiple of 4 (No in step ST35), the signals from the AF controller 53 and the timing generator 201 cause
The output mode of the CCD 21 is set to the area limited mode. That is, the setting is made to output the area-limited image 62 in 1/180 seconds (step ST40).

Subsequently, exposure is performed by the CCD 21 (step ST41), and the area limited image 6 is read from the CCD 21.
2 is output (step ST42). The output area-limited image 62 is input to the AF calculation unit 207, and the focus evaluation value is derived (step ST43). Then, based on the derived evaluation value, the focus lens 3
The drive of No. 1 is controlled (step ST44). At this time, as described above, the area limited image 62 cannot be used as the live view image, but the live view image stored in the VRAM 210 when the output mode of the CCD 21 is the normal mode is controlled by the display control unit 52. Is kept as is. As a result, the state of the display screen of the liquid crystal monitor 28 on which the subject image is displayed is maintained, and the subject image is properly displayed on the display screen of the liquid crystal monitor 28. Therefore, even when the output mode of the CCD 21 is set to the area limited mode, the user can confirm the subject image.

The operation as described above is repeated, and the focus lens 31 is finally moved to the in-focus position (step ST45).

In FIG. 8, for convenience, the CCD 21 is
After the image data is exposed (steps ST37 and ST41), various processes are performed before the next exposure is performed, but in reality, the next exposure is performed without a time interval. Therefore, the CCD 21 outputs the output of the area limited image 62 in the area limited mode (cycle 1/180 sec) to 3 times.
The operation of repeating once (1/180 seconds × 3 = 1/60 seconds) and outputting the normal image 61 in the normal mode (cycle 1/60 seconds) once is repeated continuously in time.
That is, the output mode of the CCD 21 is switched between the area limited mode and the normal mode at a cycle of 1/60 seconds. The output mode switching cycle of 1/60 seconds corresponds to the cycle T1 in which the CCD 21 outputs the normal image 61.

When the cycle T1 and the cycle T2 have the relationship of the above expression (1), the number of times the output of the area limited image 62 in the area limited mode is repeated is n (the If “n = 3” in the embodiment), the switching cycle of the output mode of the CCD 21 matches the cycle T1. Therefore, if it is determined in step ST35 described above whether the internal counter C is a multiple of "n + 1", the output mode switching cycle of the CCD 21 coincides with the cycle T1.

FIG. 11 is a diagram showing a process when the live view operation in the shooting standby state is shifted to the autofocus control, with time in the horizontal direction. FIG. 11A shows
11 shows a process (operation of FIG. 8) when the output mode of the CCD 21 is switched at a predetermined cycle, while FIG.
(B) shows the process when the output mode of the CCD 21 remains unchanged in the normal mode. Further, in FIG. 11, PT3 indicates the time point when the shutter button 25 is half pressed.

As shown in FIGS. 11 (a) and 11 (b), in the live view operation in the shooting standby state, 1 /
The normal image 61 is output from the CCD 21 in a cycle of 60 seconds, and in response to this, the update LV of the live view image in the VRAM 210 is also performed every 1/60 seconds (time points PT1 to PT1.
PT4).

Here, for example, as shown in FIG. 11B, when the output mode of the CCD 21 is not changed to the normal mode even during the autofocus control, the time point P is set.
Even after T4, the normal image 61 is output at a cycle of 1/60 second, and the live view image update LV and focus evaluation value derivation FV are performed at the same cycle of 1/60 second.

On the other hand, like the digital camera 1, the CCD
When switching the output mode of 21 in a predetermined cycle,
As shown in FIG. 11A, when the shutter button 25 is half-pressed (time point PT3), in response to this, the next CCD
The output mode of the CCD 21 is switched to the region limited mode from the exposure start point PT4 of 21. Then, the area-limited image 62 is output for three frames every 1/180 seconds (time points PT5 to PT7), and then at the time point PT7, CC
The output mode of D21 is switched to the normal mode, and 1/60 seconds after that, the normal image 61 is output as one frame (time point PT8). After that, the area-limited image 62 is displayed in the same cycle.
And the normal image 61 is output (time points PT8 to PT1).
2 ...).

In such a case, the normal image 61 is 1/30
Printed every second. From this, the update LV of the live view image in the VRAM 210 is performed every 1/30 seconds like the output cycle of the normal image 61, and the liquid crystal monitor is provided between the update LV of the live view image and the next update LV. The state of the 28 display screens will be retained. While the live view operation in the shooting standby state or the display smoothness is slightly impaired as compared with the case of FIG. 11B, the state of the subject image can be sufficiently grasped and framing can be performed. It is possible.

Further, the derivation FV of the focus evaluation value is performed four times within 1/30 seconds of the time points PT4 to PT8, and thereafter the focus evaluation value is derived in the same cycle. On the other hand, in the synchronization periods PT4 to PT8 in FIG. 11B, the focus evaluation value derivation FV is only performed twice. That is, by switching the output mode of the CCD 21, it is possible to increase the number of times FV of derivation of the focus evaluation value per unit time. This corresponds to an increase in the number of times of grasping the change in the evaluation value per unit time, so that the drive speed of the focus lens 31 can be increased without lowering the accuracy in determining the lens position. is there. Further, since the change in the evaluation value depending on the lens position can be grasped finely, the speed of determining the lens position can be improved. Therefore, by these things, autofocus control can be performed quickly and highly accurately.

Further, since the cycle T1 and the cycle T2 have the relationship of the above equation (1) and the output mode is switched at the cycle T1, it is not necessary to change the processing synchronization for the normal image 61. That is, during the autofocus control, the normal image 61 and the area-limited image 62 are continuously output in time, while the normal image 61 requires various kinds of image processing and live view image generation. This processing can be performed at the same timing as in the normal mode. Therefore, various kinds of processing can be performed on the normal image 61 without providing a new mechanism for synchronizing the processing.

For example, in the present embodiment, the refresh rate of the liquid crystal monitor 28 is 6 according to the cycle T1.
It is 0 fps. During auto focus control,
Since the live view image is updated every 1/30 seconds, a new live view image is surely obtained once every two screen updates of the liquid crystal monitor 28. As a result, the live view display can be relatively smoothly performed without changing the refresh rate or the display timing of the liquid crystal monitor 28.

Next, the operation of the autofocus control (FIG. 9: step ST51 and thereafter) when the brightness value of the subject is less than the predetermined reference value (FIG. 8: No in step ST31) will be described.

When the brightness value of the subject is relatively low, a relatively long shutter speed is required, and this shutter speed depends on the output cycle of the image data of the CCD 21. Therefore, when the output value of the CCD 21 is switched to the area limited mode when the brightness value of the subject is relatively low, the output cycle becomes short and the exposure becomes insufficient, so that an effective focus evaluation value can be obtained. I can not do it. Also, in order to eliminate this,
When the level of image data is adjusted by the signal processing circuit 202 or the like, noise in the image data increases, and as a result, the accuracy of autofocus control decreases.

Therefore, when the brightness value of the subject is less than the predetermined reference value, CC is set even in the autofocus control.
The output mode of D21 is not switched as it is in the normal mode, and a relatively accurate focus evaluation value is obtained.

That is, the output mode of the CCD 21 is set to the normal mode (step ST51), the CCD 21 is exposed (step ST52), and the normal image 61 is output from the CCD 21 (step ST53). The output normal image 61 is subjected to predetermined processing by the signal processing circuit 202 to the image processing unit 205 in the same manner as described above, and V
The live view image in the RAM 210 is updated (step ST54).

At the same time, the normal image 61 is also input to the AF calculation unit 207, and the focus evaluation value is derived (step ST55). The derived evaluation value is input to the overall control unit 40, and the drive of the focus lens 31 is controlled by the AF control unit 53 based on the evaluation value (step ST56). Then, such processing is performed until the focus lens 31 reaches the in-focus position (N in step ST57).
will be repeated).

As described above, in the digital camera 1, only when the brightness value of the subject is equal to or greater than the predetermined reference value, the CCD 21
Since the output mode is switched, it is possible to prevent the accuracy of the autofocus control from being lowered.

Next, the operation of the autofocus control when the brightness value of the subject is equal to or greater than the predetermined reference value and the state of the liquid crystal monitor 28 is not displayed (FIG. 8: No in step ST32) (FIG. 10: Step ST61 and subsequent steps) will be described.

When the liquid crystal monitor 28 is in the non-display state, it is not necessary to output the normal image 61 for live view display from the CCD 21. Therefore, in the autofocus control, the output mode of the CCD 21 remains the area limited mode. Can be

That is, the output mode of the CCD 21 is set to the area limited mode (step ST61), and the CCD 2
1 is exposed (step ST62), CCD2
The area limited image 62 is output from 1 (step ST6).
3). The output area limited image 62 is the AF calculation unit 207.
And the focus evaluation value is derived (step ST64). Further, the drive of the focus lens 31 is controlled based on the derived evaluation value (step ST
65). Then, such processing is performed by the focus lens 3
This is repeated until 1 becomes the in-focus position (No in step ST66).

As described above, in the digital camera 1, when the liquid crystal monitor 28 is in the non-display state, the output mode of the CCD 21 is set to the area limiting mode, so that the number of times the focus evaluation value is derived per unit time is further increased. Therefore, the autofocus control can be performed more quickly.

<2. Second Embodiment> Next, a second embodiment of the present invention will be described. In the first embodiment, when the brightness value of the subject is equal to or larger than a predetermined reference value and the state of the liquid crystal monitor 28 is display, the output mode of the CCD 21 is switched in response to the half-press of the shutter button 25. However, in the present embodiment, the output mode is switched in response to the lens position being close to the in-focus position.

The configuration of the digital camera 1 of the present embodiment is the same as that shown in FIGS. 1 to 3, and the outline of the operation in the photographing mode is the same as that shown in FIG. The description is omitted.

FIG. 12 is a diagram showing the flow of the autofocus control operation of the digital camera 1 of this embodiment.
First, as in the first embodiment, whether or not the brightness value of the subject is greater than or equal to a predetermined reference value (step ST71), and whether the state of the liquid crystal monitor 28 is display or non-display. It is sequentially determined (step ST72). Similar to the first embodiment, when the brightness value of the subject is less than the predetermined reference value, the operations after step ST51 in FIG. 9 are performed,
When the liquid crystal monitor 28 is in the non-display state, the operations after step ST61 in FIG. 10 are performed.

Hereinafter, in the present embodiment, the operation of the autofocus control (step ST73 and thereafter) in the case where the brightness value of the subject is equal to or more than a predetermined reference value and the state of the liquid crystal monitor 28 is display will be described.

First, the output mode of the CCD 21 is set to the normal mode (step ST73). Next, CCD
21 is exposed (step ST74), CCD
21 outputs the normal image 61 (step ST7).
5). Similarly to the above, the output normal image 61 is subjected to predetermined processing by the signal processing circuit 202 to the image processing unit 205 to be a live view image, and the live view image in the VRAM 210 is updated (step ST76). ).

At the same time, the normal image 61 is also input to the AF calculation unit 207, and the focus evaluation value is derived (step ST77). The derived evaluation value is input to the overall control unit 40, and the drive of the focus lens 31 is controlled by the AF control unit 53 based on the evaluation value (step ST78).

Then, the AF controller 53 determines whether or not the lens position is near the in-focus position (step ST79). Specifically, it is determined whether or not the monitored evaluation value has decreased, and if it has decreased, it is determined that the lens position is near the in-focus position (see FIG. 6). If the lens position is not near the in-focus position, the process returns to step ST74 again, and the series of processes described above is repeated while the output mode of the CCD 21 remains in the normal mode.

On the other hand, if the lens position is near the in-focus position, the process proceeds to step ST33 in FIG.
The same operation as that of the above embodiment is performed. That is, AF
In response to the controller 53 determining that the lens position is in the vicinity of the in-focus position, the output mode of the CCD 21 is a predetermined cycle (1/60 seconds) between the area-limited mode and the normal mode. It will be switched.

FIG. 13 is a diagram showing the processing in the autofocus control of the digital camera 1 of the present embodiment, with the passage of time in the horizontal direction. In FIG. 13, PT11
Indicates the time when the shutter button 25 is pressed halfway, and P
T15 indicates the time when it is determined that the lens position is near the in-focus position.

In the digital camera 1 of the present embodiment, the shutter button 25 is half pressed (time point PT1).
When 1), the output mode of the CCD 21 remains in the normal mode and shifts to the autofocus control (time point PT12). Therefore, the normal image 61 from the CCD 21 at a cycle of 1/60 seconds
Is output and the live view image update LV and focus evaluation value derivation FV are performed at the same cycle of 1/60 seconds (time points PT12 to PT15).

When it is determined that the lens position is near the in-focus position (time point PT15), CC is returned in response to this determination.
The output mode of D21 is switched to the area limited mode. Then, the area-limited image 62 becomes 3 every 1/180 second.
The frame is output (time points PT16 to PT18), and then the output mode of the CCD 21 is switched to the normal mode at time point PT18, and 1/60 seconds after that, one frame of the normal image 61 is output (time point PT19). Or later,
The area limited image 62 and the normal image 61 are output in the same cycle (time point PT19 ...).

Up to the time point PT15 when it is determined that the lens position is near the in-focus position, the live view image is updated LV every 1/60 seconds, and after the time point PT15, 1 is updated.
A live view image update LV is performed every / 30 seconds. Therefore, the live view image is smoothly displayed on the liquid crystal monitor 28 until the time point PT15.
The period during which the smoothness of live view display is impaired can be shortened.

Further, the focus lens 31 moves to the time point PT1.
It is driven at a relatively high speed up to 5 and is driven at a relatively low speed after the time point PT15, while the derivation FV of the focus evaluation value is 2/30 seconds until the time point PT15.
It is performed once (every 1/60 seconds), and is 1 after time PT15
/ 4 times in 30 seconds. Therefore, time point PT15
After that, the number of times of grasping the change of the evaluation value per unit time is increased, and the focus lens 31
The lens position can be determined with high accuracy without relatively slowing down the speed of. As a result, autofocus control can be performed quickly and with high accuracy.

<3. Modifications> Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made.

For example, in the above embodiment, CC
The area limited image 62 output from D21 is the image data of the area including the row of horizontal pixels including the focus area. However, the area limited image 62 only needs to include at least the focus area. Only the image data may be the area limited image 62.

In the above embodiment, the CCD 21 is used as the image data used for live view display.
The normal image 61 for all pixels of
Image data in which pixels are thinned out at a predetermined interval at the time of outputting from 1 may be used. Even image data thinned out at a predetermined interval in this way can be used for live view display because it becomes image data for the entire area of the CCD 21. Further, by using such image data, the operation of the autofocus control can be performed more quickly.

Further, in the above embodiment, the brightness value of the subject is obtained from the image data output from the CCD 21, but the brightness value of the subject may be detected using a brightness sensor or the like. .

Further, in the above embodiment, when the output mode of the CCD 21 is set to the area limited mode, VRA is set.
By keeping the live view image in M210,
The state of the display screen of the liquid crystal monitor 28 on which the subject image is displayed is held, but the state of the display screen of the liquid crystal monitor 28 is held by not rewriting (refreshing) the display screen of the liquid crystal monitor 28. You may

Further, in the above embodiment, various functions are realized by the CPU performing arithmetic processing in accordance with the program, but all or part of these functions may be realized by a dedicated electric circuit. Good. In particular, a high-speed operation can be realized by constructing a place where a repeated operation is performed with a logic circuit. On the contrary, all or part of the function realized by the electric circuit is C
It may be realized by the PU performing arithmetic processing according to a program.

Note that the specific embodiments described above include inventions having the following configurations.

(1) The image pickup device according to claim 2, further comprising: a detection unit that detects the brightness of the subject, wherein the image pickup control unit is configured to detect the brightness of the subject when the brightness is equal to or higher than a predetermined reference value. An image pickup apparatus, wherein the output mode of the image pickup means is switched between the first output mode and the second output mode at a predetermined cycle.

According to this, it is possible to prevent the accuracy of focus control from being lowered when the subject has low luminance.

(2) In the image pickup apparatus according to the second aspect, the first image pickup means outputs the first image data.
When the output cycle is defined as T1 and the second output cycle in which the image pickup unit outputs the second image data is defined as T2, T1 and T2 are T1 = n · T2, where n is a natural number of 2 or more. , And the imaging control means switches between the first output mode and the second output mode in the first output cycle.

This facilitates the synchronization of processing when the first and second image data are processed temporally continuously.

[0114]

As described above, according to the first aspect of the present invention, even when the output mode of the image pickup means is set to the second output mode when performing the focus control, Since the state of the display screen is maintained, the subject image can be displayed on the display unit while performing the focus control quickly.

Further, according to the second aspect of the present invention, the first image data relating to the entire area is output in a predetermined cycle. Therefore, when the focus control is performed, the subject image displayed on the display means is in a predetermined cycle. Can be updated at.

According to the third aspect of the invention, the optical system can be driven at a high speed from the start of the focus control, and the focus control can be performed quickly.

Further, according to the invention of claim 4, when the position of the optical system becomes close to the in-focus position, the number of image data acquired per unit time can be increased, so that the speed can be increased. In addition, the position of the optical system can be determined with high accuracy.

Further, according to the invention of claim 5, when the display means is in the display state, the subject image can be displayed on the display means while performing the focus control quickly, and when the display means is in the non-display state. Can perform focus control more quickly.

[Brief description of drawings]

FIG. 1 is a perspective view of a digital camera as an imaging device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration on the back side of a digital camera.

FIG. 3 is a diagram showing a main internal configuration of a digital camera as functional blocks.

FIG. 4 is a diagram showing image data and a normal image acquired by a CCD 21.

FIG. 5 is a diagram showing image data and a region limited image acquired by a CCD 21.

FIG. 6 is a diagram showing an example of a relationship between a lens position and a focus evaluation value.

FIG. 7 is a diagram showing an outline of an operation in a shooting mode of the digital camera.

FIG. 8 is a diagram showing a flow of an autofocus control operation in the first embodiment.

FIG. 9 is a diagram showing a flow of an autofocus control operation according to the first embodiment.

FIG. 10 is a diagram showing a flow of an autofocus control operation according to the first embodiment.

FIG. 11 is a diagram showing processing of autofocus control in the first embodiment with time in the horizontal direction.

FIG. 12 is a diagram showing a flow of an autofocus control operation according to the second embodiment.

FIG. 13 is a diagram showing processing of autofocus control in the second embodiment with time in the horizontal direction.

[Explanation of symbols]

1 digital camera 3 shooting lens 21 CCD 25 shutter button 28 LCD monitor 29a Display switching button 31 focus lens 53 AF control unit 61 Normal image 62 area limited image 201 Timing Generator 209 Lens drive unit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // G02B 7/36 G02B 7/11 D G03B 13/36 G03B 3/00 A (72) Inventor Keiji Tamai 2-13-3 Azuchicho, Chuo-ku, Osaka-shi, Osaka Prefecture Osaka International Building Minolta Co., Ltd. (72) Inventor Motohiro Nakanishi 2-3-3 Azuchi-cho, Chuo-ku, Osaka-shi, Osaka City Osaka International Building Minolta Corporation ( 72) Inventor Toshihiro Hamamura 2-33-1 Azuchi-cho, Chuo-ku, Osaka, Osaka Prefecture Osaka International Building Minolta Co., Ltd. (72) Shinichi Fujii 2-3-3 Azuchi-cho, Chuo-ku, Osaka, Osaka Osaka International Building F term in Minolta Co., Ltd. (reference) 2H011 BA31 CA19 2H044 DA01 DC02 2H051 BA45 2H102 AA33 AA44 5C022 AA13 AB26 AC01 AC12 AC42 AC54 AC74

Claims (5)

[Claims] 1. An image pickup apparatus, wherein image data of a subject is acquired via an optical system, and first image data relating to the entire area of the image data is output as an output mode for outputting the image data. Image pickup means having a first output mode for outputting the second image data including at least a predetermined focusing target area in the image data at a higher speed than the first output mode, and the image data. Focus control means for performing focus control of the optical system based on the focusing target area therein, display means for displaying a subject image on a display screen based on the first image data, and focus control means for focus control When doing
An image pickup control means for setting the output mode of the image pickup means to the second output mode; and a display screen of the display means for displaying a subject image when the output mode of the image pickup means is set to the second output mode. And a display control unit that holds the state of. 2. The image pickup apparatus according to claim 1, wherein the image pickup control unit sets the output mode of the image pickup unit to the first output mode and the second output when the focus control unit performs focus control. An image pickup apparatus, characterized in that it is switched to and from a mode at a predetermined cycle. 3. The image pickup apparatus according to claim 2, further comprising a reception unit that receives an instruction to start focus control of the optical system, wherein the image pickup control unit is one of the focus control units that is received by the reception unit. In response to the start instruction, the output mode of the image pickup means is set to the first output mode and the second output mode.
An image pickup apparatus, characterized in that it switches between an output mode and a predetermined cycle. 4. The image pickup apparatus according to claim 2, further comprising: a determination unit that determines whether or not the position of the optical system is near the in-focus position, and the image pickup control unit includes the determination unit. In response to the determination that the position of the optical system is near the in-focus position, the output mode of the image pickup unit is set to a predetermined cycle between the first output mode and the second output mode. An imaging device characterized by being switched by. 5. The image pickup apparatus according to claim 2, further comprising a display switching unit that switches a state of the display unit between display and non-display, and the image pickup control unit includes a display state of the display unit. In the case of, the output mode of the imaging means is switched at a predetermined cycle between the first output mode and the second output mode, and when the display means is in the non-display state, the output mode of the imaging means Is set to the second output mode.