JP2001275033A - Digital still camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital still camera which can perform automatic focusing suitable to an object in consecutive shoots. SOLUTION: A photographer selects and sets a phase difference AF system or contrast AF system (step S10). Then a picture is taken by the selected AF system (step S13 to S17). When a shutter button is fully depressed for a specific time or longer, namely, when it is decided in a step S18 that the full depression of the shutter button is not ended yet, it is decided that consecutive shooting is selected and the processes of the steps S17 to S20 are repeated to take pictures consecutively by the selected AF system. Consequently, the automatic focusing suitable for an object is enabled even in the consecutive shooting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital still camera for obtaining an image signal from a light image by an image pickup device.

[0002]

2. Description of the Related Art Conventionally, many digital still cameras employing a contrast autofocus (AF) system have been found. That is, the digital still camera employs an AF method in which a contrast of an image is obtained from image data obtained by an image sensor, and a focusing lens is driven so that the contrast is maximized to perform focusing.

In a single-lens reflex digital still camera, the light that has passed through a photographing lens is separated by a separator lens, and the phase difference is determined by calculating the amount of lens movement based on the distance between the images. Many adopt an AF method.

The contrast AF and the phase difference A
F has advantages and disadvantages due to its principle. In general, the contrast AF has a high focusing accuracy, but takes a long time to focus (a slow focusing speed). Conversely, the phase difference AF has a short time until focusing, but the accuracy of focusing may be a problem depending on the scene to be photographed and the image sensor used.

[0005]

In recent years, the number of pixels of an image sensor of a digital still camera has increased, and therefore, a high-speed and high-precision AF system has been required. These factors become particularly important during continuous shooting (continuous shooting).

However, the contrast AF method and the phase difference AF method have the above-mentioned advantages and disadvantages. For example, if continuous shooting is performed in a digital still camera employing the contrast AF method, the precision of focusing will be improved. However, it takes time to focus and the shooting interval becomes longer. Conversely, if continuous shooting is performed in a digital still camera that employs the phase difference AF method, the shooting interval can be shortened, but the focusing accuracy is reduced.

[0007] By the way, since the subjects are various such as fast-moving subjects and slow-moving subjects, the digital still camera adopting the contrast AF method is not suitable for continuously photographing fast-moving subjects for the above reasons. Conversely, phase difference A
The digital still camera adopting the F system has a problem that the subject moves slowly, but is not suitable for continuous shooting while seeking the focusing accuracy.

An object of the present invention is to overcome the above-mentioned problems in the prior art, and to provide a digital still camera capable of selecting an autofocus method suitable for a subject during continuous shooting.

[0009]

According to a first aspect of the present invention, there is provided a digital still camera for obtaining an image signal from a light image by an image pickup device. A contrast-type focusing unit that performs auto-focusing based on the contrast of an image signal obtained by the image sensor, a continuous shooting control unit that controls a shooting unit to perform continuous shooting, and an autofocus at least during continuous shooting. As a method, there is provided a selection setting means for selecting and setting one of the phase difference detection method automatic focusing means and the contrast method focusing means.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

<1. Apparatus Configuration> FIG. 1 is a schematic configuration diagram of a main mechanism portion in a digital still camera according to an embodiment of the present invention, and FIG. 2 is an operation state diagram of the main mechanism portion during photographing.

The digital still camera 1 has a camera body 2 constructed using a silver halide single-lens reflex camera.
A photographic lens 3 is mounted on the front of the camera body 2, and the photographic lens 3 is provided with a photographic lens unit 4, an aperture 5, and the like.

A quick return mirror M1 rotatably supported by a pivot 6 above the rear of the camera body 2 is disposed behind the taking lens unit 4 in the optical path direction. Behind the optical path direction of
A focal plane shutter 7 and an image sensor 8 behind the focal plane shutter 7 are arranged.

Although the focal plane shutter 7 is also left in the camera body 2, the focal plane shutter 7 may be removed depending on the type of the image sensor 8.

An optical low-pass filter 18 for preventing the influence of aliasing noise when sampling the analog image signal from the image sensor 8 is provided on the front surface of the image sensor 8.
The optical low-pass filter 18, the focal plane shutter 7, and the imaging sensor 8 constitute an imaging unit 19.

The image pickup unit 19 can be moved in the front-rear direction along the optical axis by a moving mechanism 30. Then, the imaging unit 19 moves forward in the optical axis direction until the imaging position, that is, the light receiving surface of the imaging sensor 8 reaches the lens back position, in conjunction with the upward rotation of the quick return mirror M1 during imaging, After the photographing, the quick return mirror M1 moves backward in the optical axis direction to a retreat position where mechanical interference with the quick return mirror M1 does not occur in conjunction with the downward rotation of the quick return mirror M1.

As the moving mechanism 30, a mechanism having a known structure may be adopted. For example, a mechanism that converts the rotation of a bolt driven by a motor into rotation in the axial direction of the bolt may be used. What is necessary is just to comprise.

Above the quick return mirror M1, a finder-equivalent portion 9 of the silver halide camera is formed in the camera body 2, and the finder-equivalent portion 9 is provided with a pentagonal prism through a focusing screen 10. 11 are arranged. Further, a predetermined eyepiece 12 is arranged behind the prism 11, an eyepiece 13 is arranged behind the eyepiece 12, and a photometric sensor 14 is arranged above the eyepiece 12. ing. In FIG. 2, the eyepiece is omitted. The quick return mirror M1, the prism 11, the eyepiece 12, and the eyepiece 13 form an optical finder.

When performing the phase difference autofocus, the quick return mirror M1 is used until the shutter button 24a described later is fully pressed, as shown in FIGS.
As shown in FIG. 2A, the optical path L from the photographic lens unit 4 is at a steady position inclined at an angle of 45 degrees with respect to the optical axis.
To the focusing screen 10. When the shutter button is fully pressed, as shown in FIGS. 2 (B) to 2 (D), it is pivotally displaced upward about the pivot 6 to a substantially horizontal position to move the optical path L from the taking lens unit 4. Open.

M2 is a mirror integrated with the quick return mirror M1.
The optical image transmitted through the half mirror unit partially provided in the mirror 1 is directed to the distance measuring sensor 15 by the mirror M2 and the fixed mirror M3 below. The distance measurement sensor 15 detects the distance to the subject by receiving the optical image and automatically focuses the photographing lens unit 4.

The prism 11 serves to direct the optical image formed on the focusing screen 10 to the photometric sensor 14 and the eyepiece 13. Further, based on the light amount data obtained by the camera control CPU 20 based on the image data from the photometric sensor 14 or the image sensor 8, control values of the aperture value and the shutter speed are set (AE control). Imaging sensor 8
Is set.

A focus motor 36 for driving a focus lens included in the taking lens unit 4 in the optical axis direction is provided inside the camera body 2.

On the back of the camera body 2, there is provided a display section 16 comprising a liquid crystal display (LCD) for displaying an image obtained based on the output of the image sensor 8.

On the other hand, when performing the contrast type autofocus, the quick return mirror M1 is always in a state of being displaced upwardly in this case. In this case, the subject image by the photographing lens unit 4 is formed on the image sensor 8. The subject can be confirmed by repeating the image pickup of the subject image by the image sensor 8 every 1/30 second and displaying the output on the display unit 16 (live view display).

FIG. 3 is a block diagram showing a control system of the digital still camera 1.

In FIG. 3, 3 is a photographic lens, 4 is a photographic lens unit, 5 is an aperture, M1 is a quick return mirror,
7 is a focal plane shutter, 8 is an image sensor,
11 is a prism, 13 is an eyepiece, 16 is a display,
These are the same as those shown in FIGS.

Reference numeral 20 denotes a camera control CPU, which controls each part of the camera body 2. Specifically, the aperture 5 is changed to the aperture driver 2
1, and controls the image sensor 8 via a timing generator (sensor drive) 22. Also,
The actuator 17 of the quick return mirror M1 and the moving mechanism 30 of the imaging unit 19 are controlled via a mirror / imaging unit drive circuit 23, and the focal plane shutter 7 is controlled via a shutter driver 25. Further, the focus motor 36 is connected to the motor driver 2.
6 is controlled.

A camera operation switch 24 is connected to the camera control CPU 20. The camera operation switch 24 includes a shutter button 24a, a power switch, and the like.

The image sensor 8 comprises a charge-coupled device (CCD) in this embodiment. The imaging sensor 8 is
(Red), G (green), and B (blue) primary color transmission filters are area sensors in which pixels are arranged in a checkered pattern, and optical images of a subject by the photographing lens unit 4 are converted into R, G, and B colors. The signal is photoelectrically converted into a component image signal (a signal composed of a signal sequence of pixel signals received by each pixel) and output.

The timing generator 22 generates and outputs a drive control signal for the image sensor 8 based on a reference clock transmitted from the camera control CPU 20. The timing generator 22 generates clock signals such as integration start / end (exposure start / end) timing signals, readout control signals (horizontal synchronizing signal, vertical synchronizing signal, transfer signal, etc.) of the light receiving signal of each pixel, and the like. Output to the image sensor 8 via the driver.

The outputs of the image sensor 8 are CDS
Signal processing is performed by a (correlated double sampling) circuit 81, an AGC (auto gain control) circuit 82, and an A / D converter 83. The CDS circuit 81 reduces the noise of the image signal, and the AGC circuit 82 adjusts the level of the image signal by adjusting the gain. The A / D converter 83 is an AGC
It converts the analog signal normalized by the circuit 82 into a 10-bit digital signal.

The image processing section 40 is an image processing section for forming an image file by performing image processing on the output of the A / D converter, and is controlled by an image processing CPU.

At the time of photographing, image data from the image sensor 8 is taken into the image processing section 40 and various processing is performed.

The signal from the A / D converter 83 taken into the image processing unit 40 is written into the image memory 61 in synchronization with the reading from the image sensor 8, and the data in the image memory 61 is accessed thereafter. Each block is processed.

In the image processing section 40, a pixel interpolation block 41 is a block for performing pixel interpolation with a predetermined interpolation pattern. In this embodiment, after each of R, G, and B pixels is masked with each filter pattern, For G having pixels up to the high band, the median (intermediate value) filter replaces the average value of the intermediate values of the four peripheral pixels with R,
For B, average interpolation is performed to obtain respective outputs.

The color balance control block 42 calculates R, R,
The G and B outputs are independently subjected to gain correction to perform R, G, and B color correction. About color balance,
Camera control C for the average of each of the R, G, and B outputs
R / G and B / G are calculated by the PU 20 to obtain R and B correction gains.

The gamma correction block 43 performs non-linear conversion on the R, G, and B outputs in which the color balance has been normalized, and performs gradation conversion suitable for the display unit 16. The gamma-corrected image data is stored in the image memory 61.

The video encoder 44 includes an image memory 61
Calls the above data stored in NTSC / PAL
And displays it on the display unit 16.

The image compression block 45 calls up image data from the image memory 61 and performs a compression process on the captured image obtained from the image sensor 8. The compressed image is stored in the memory via the memory card driver 46 after compression. It is recorded on the card 62.

Note that the memory card 62 is
At a predetermined position.

FIG. 4 is a diagram showing a state of the back of the digital still camera.

On the back of the camera body 2, the display unit 1
In addition to the button 6, a four-way switch 35 is provided on the right side thereof, and various operations such as selection of a selection item corresponding to the display on the display unit 16 can be performed with the buttons U, D, L, and R. .

Also, a quad switch 3 on the back of the camera body 2
5, an LCD button 31, a confirm button 32, a cancel button 33, and a menu button 34 are provided. Among them, the LCD button 31 is a button for turning on and off the display of the display unit 16, and the display unit 16 is switched on and off each time the LCD button 31 is pressed. A confirm button 32 and a cancel button 33 are switches for inputting an instruction to confirm or cancel the selection at the time of selecting an item in various settings. A menu button 34 switches and displays various setting screens such as a menu selection screen described later. Switch.

<2. Processing and Operation> Next, the processing and operation of the digital still camera 1 will be described. The digital still camera 1 mainly has two modes, a “photographing mode” and a “playback mode”. Among them, the photographing mode is a mode for performing processing relating to photographing, and the reproduction mode is a mode for performing processing relating to a photographed image, such as reproducing and displaying a photographed image recorded on the memory card 62 on the display unit 16. In particular, in the digital still camera 1 according to the present embodiment, one of single shooting and continuous shooting (continuous shooting) can be performed by the photographer in the shooting mode.

Switching between the photographing mode and the reproduction mode is performed by operating the menu button 34 or the like.
Displays the mode selection screen.
The operation can be performed by operating the continuous switch 35, the confirmation button 32, and the cancel button 33.

The processing and operation in the photographing mode will be described below. FIG. 5 is a control flowchart of the digital still camera 1 in a shooting mode. Unless otherwise specified, the operation of each unit is controlled by the camera control CPU 20.
Done by

First, prior to actual photographing, the photographer sets and selects an AF method to be used in advance (step S10). As a result, the quick return mirror M1 moves up and down as described above.

FIG. 4 shows a state where the menu setting screen is displayed on the screen of the display unit 16. As shown in FIG. 4, in the digital still camera 1, on the menu setting screen, an AF method to be performed when the camera is half-pressed is selectively designated. By pressing either the button U or the button D of the quad switch 35, it is possible to select between the contrast AF method and the phase difference AF method when the AF is pressed halfway. ing.

Next, at the time of actual photographing, the shutter button 24a is half-pressed by the photographer (step S1).
1). Then, automatic exposure (AE) is performed (step S12). At the time of AE when the phase difference AF method is selected in step S10, as shown in FIG. 2A, light incident through the photographing lens unit 4 and the aperture 5 is used as a quick return in the camera body 2. The optical path L is changed upward by the mirror M <b> 1, forms an image on the focusing screen 10, and then enters the photometric sensor 14 via the pentagonal prism 11. The photometric sensor 14 measures the amount of light.

At the time of AE when the contrast AF method is selected in step S10, the camera control CPU 20 obtains the light amount from the image data obtained by the image sensor 8.

Then, no matter which AF method is selected, the camera control CP based on the obtained light amount data is used.
Exposure control data is calculated in U20, and based on the calculated exposure control data, the aperture 5 is controlled via the aperture driver 21 so that the amount of exposure to the image sensor 8 becomes an appropriate value.
Is controlled, and the timing generator 22 that supplies a drive control signal to the image sensor 8 is controlled.

At this time, the image pickup unit 19 is at the rear retract position to avoid mechanical interference with the quick return mirror M1, and the light receiving surface of the image sensor 8 is located behind the lens back position. .

Next, the AF method is determined (step S13), and if the phase difference AF method is selected,
The phase difference AF is executed (Step S14).

At the time of executing the phase difference AF, a part of the light incident from the photographing lens unit 4 and the aperture 5 passes through the quick return mirror M1, and then travels to the distance measuring sensor 15 via the mirror M2 and the fixed mirror M3. Distance sensor 15
Receives the light, detects the distance to the object, and drives the focus motor 36 based on the detected distance.
Is automatically focused.

At the same time as the photometry and distance measurement operations described above, the optical image whose optical path L has been converted by the quick return mirror M1 is reduced by the prism 11 and the eyepiece 12, and then reaches the eyepiece 13. Therefore, the photographer can visually recognize the subject through the eyepiece 13.

Conversely, if it is determined in step S13 that the contrast AF method has been selected, contrast AF is executed (step S15).

When executing the contrast AF, the camera control CPU 20 reads out the image data stored in the image memory 61, obtains an AF evaluation value (contrast) of the image, and sets the focus motor 36 so that the AF evaluation value becomes maximum. Is driven to move the focus lens to perform focusing. In this case, a known technique such as a hill-climbing method can be used as a control method for maximizing the contrast.

Next, the shutter button 24a is further depressed and fully depressed by the photographer (step S).
16). Then, shooting is performed (step S1).
7).

The photographing operation when the phase difference AF method is selected is as follows. When the shutter button 24a is fully pressed, the aperture 5 is stopped down by a predetermined amount, and at the same time, the quick return mirror M1 rotates upward via the pivot 6 as shown by a white arrow in FIG. Start the displacement. In conjunction with this, the imaging unit 19 moves forward in the optical axis direction of the photographing lens unit 4 via the moving mechanism 30. In FIG. 2, the quick return mirror M1 is used.
The moving mechanism 30 for moving the imaging unit 19 and the actuator 17 for driving the imaging unit 19 are omitted.

The quick return mirror M1 is shown in FIG.
When the mirror up operation is completed by reaching the lower portion of the focusing screen 10, the forward movement of the imaging unit 19 also stops, and the light receiving surface of the imaging sensor 8 is set to the lens back position.

Then, as shown in FIG. 2D, the focal plane shutter 7 opens and closes at a predetermined speed,
The optical image that has passed through the photographing lens unit 4 and the aperture 5 is formed as it is on the image sensor 8 and photoelectrically converted here. The photoelectrically converted signal is output via a buffer.

After the photographing, the quick return mirror M1 returns to the original position, and the optical path L moves toward the focusing screen 10 again, and enters a photographing standby state. In conjunction with the rotation return operation of the quick return mirror M1, the imaging unit 19 moves to the retracted position rearward in the optical axis direction to avoid interference with the quick return mirror M1 that rotates and returns.

The image data output from the image sensor 8 is supplied to a CDS circuit 81, an AGC circuit 82, an A / D converter 8
3 is subjected to predetermined signal processing, and then the image processing unit 4
At the same time, it is written into the image memory 61 in synchronization with the reading of the image sensor 8.

The image data written in the image memory 61 is subjected to the above-described pixel interpolation processing, color balance control, and gamma correction processing in the image processing section 40, and is stored again in the image memory 61. Memory 6
1 and is displayed on the display unit 16 as a photographed image. At the same time, after the image is compressed by the image compression block 45, the memory card 6
2 is recorded.

The photographing operation when the contrast AF method is selected is as follows. Shutter button 24
When “a” is fully pressed by the photographer, the aperture 5 becomes a predetermined amount,
It is narrowed down. Then, as shown in FIG. 2D, the focal plane shutter 7 opens and closes at a predetermined speed, and the optical image that has passed through the photographing lens unit 4 and the aperture 5 is formed as it is on the image sensor 8, where the photoelectric conversion is performed. Is done. The photoelectrically converted signal is output via a buffer.

The image data output from the image sensor 8 is subjected to predetermined signal processing and then taken into the image processing section 40 as in the case where the phase difference AF method is selected. The data is written to the image memory 61 in synchronization with the reading. The image data written in the image memory 61 is subjected to the same image processing as in the case where the phase difference AF method is selected by the image processing unit 40, stored again in the image memory 61, and read from the image memory 61. The displayed image is displayed on the display unit 16 as a captured image. The data is recorded on the memory card 62 in the same manner as when the phase difference AF method is selected.

Next, it is determined whether or not the shutter button 24a is not fully pressed (step S1).
8). In the digital still camera 1, when the full-press state of the shutter button is instantaneously terminated, it is determined that the image is a single shot. It is determined to be continuous shooting.

That is, if it is determined in the first determination in step S18 that the full-press state is not reached,
It is determined that single shooting has been selected, and the process proceeds to step S19.
Conversely, if it is determined in step S18 that the shutter button has been fully pressed at least once, it is determined that continuous shooting has been selected, and the AF process and the shooting process are repeated. Specifically, when the phase difference AF is selected, the phase difference AF is selected as in step S14.
Is executed (step S19), and when the contrast AF is selected, the contrast AF is executed as in step S15 (step S20). In each case, the process returns to step S17 to repeat the photographing, and the shutter button is fully pressed. Until the state disappears, the processing of steps S17 to S20 is repeated. As a result, one image data is stored in the image memory 61 in the case of single shooting, and a plurality of continuous image data is stored in the image memory 61 in the case of continuous shooting. In the case of continuous shooting, the processing of steps S17 to S20 is repeated at the shortest possible photographing time interval according to each AF method.
When the movement of the subject is large, the contrast A
F takes time. The AE control in S12 may be performed before each of the AF processes in S19 and S20.

As is clear from the above, the photographing is executed based on the selected AF method in both the single shooting and the continuous shooting.

If it is determined in step S18 that the shutter button has been fully pressed, the recording process is performed (step S19). Specifically, the image data stored in the image memory 61 is read out and displayed on the display unit 16 as a photographed image. At the same time, the image is compressed by the image compression block 45 and then recorded on the memory card 62 via the memory card driver 46. In the case of continuous shooting, this process is performed on each of the obtained plurality of image data.

Thus, the processing in the photographing mode ends.

As described above, according to this embodiment, at least the autofocus at the time of the continuous shooting is performed.
Since the user can select either the phase difference AF or the image signal AF, the photographer can select and set the AF method according to the subject, thereby performing autofocus suitable for the subject during continuous shooting.

<3. Modifications> In the above embodiment, an example of a digital still camera has been described, but the present invention is not limited to this.

For example, in the above embodiment, the selection between single shooting and continuous shooting is determined based on whether or not the shutter button is fully depressed for a predetermined time or more. However, as in FIG. As the display at 16, a shooting mode setting screen including selection items for single shooting and continuous shooting is provided, and these can be selected and set by the same operation as menu setting. In this case, when single shooting is set, the determination in step S18 in FIG. 5 and the AF processing in steps S19 and S20 are not required.

Further, in the above embodiment, the case where the present invention is applied to a single-lens reflex digital camera has been described.
The present invention can be applied to a lens shutter type digital camera using an F sensor.

[0076]

As described above, according to the first aspect of the present invention, at least one of a phase difference detection type automatic focusing unit and a contrast type focusing unit is selected as an autofocusing method at the time of continuous shooting. Since the selection setting means is provided for performing automatic setting, it is possible to perform autofocus suitable for the subject during continuous shooting.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main mechanism in a digital still camera according to an embodiment of the present invention.

FIG. 2 is an operation state diagram of a main mechanism portion during photographing.

FIG. 3 is a block diagram showing a control system of the digital still camera.

FIG. 4 is a diagram showing a state of the back of the digital still camera.

FIG. 5 is a control flowchart in a shooting mode of the digital still camera.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Digital still camera 8 Image sensor (image signal focusing means with an image sensor, 20 and 36) 15 Distance measuring sensor (phase difference focusing means with 20 and 36) 16 Display part (selection setting means with 32-35) 20 Camera Control CPU (continuous shooting control means) 32 Enter button 33 Cancel button 34 Menu button 35 Quad switch 36 Focus motor M2 Mirror M3 Fixed mirror

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // H04N 101: 00 G03B 3/00 A F term (reference) 2H011 AA03 BA21 BA31 DA00 2H051 AA00 BA02 BA47 DA02 EA21 5C022 AA13 AB27 AB29 AC02

Claims (1)

[Claims] 1. A digital still camera for obtaining an image signal from a light image by an image sensor, comprising: a phase difference detection type automatic focusing unit; and autofocusing based on a contrast of the image signal obtained by the image sensor. A contrast type focusing means for performing, a continuous shooting control means for controlling a photographing means so as to perform continuous shooting, and a phase difference detection type automatic focusing means and the contrast type focusing means at least as an auto focus method at the time of continuous shooting. And a selection setting means for selecting and setting any one of the above.