Photographic device and control method therefor

• US 20050200744A1
• Filed: 03/10/2005
• Published: 09/15/2005
• Est. Priority Date: 03/12/2004
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Kobayashi, Koji
• Granted Patent: US 7,733,414 B2
• Time in Patent Office: Days
• US Class Current: 348/362
• CPC Class Codes: H04N 2101/00 Still video cameras
• CPC Class Codes: H04N 23/667 Camera operation mode switching, e.g. between still and video, sport and normal or high- and low-resolution modes
• CPC Class Codes: H04N 23/72 Combination of two or more compensation controls
• CPC Class Codes: H04N 23/73 by influencing the exposure time

Abstract

There is disclosed a photographic device that uses an image sensor and an electronic viewfinder. When a release button is pressed halfway, an aperture value, an electronic shutter speed and a photosensitivity are decided based on the present subject brightness to provide a proper exposure value for photographing a still image. So long as the release button is kept being pressed halfway, a timing generator drives the image sensor to shoot video images at a frame rate of 20 Hz, and the aperture value decided for still image photography is fixed, whereas the electronic shutter speed and the photosensitivity are adjusted according to the subject brightness by use of an aperture-priority type video program. When the release button is pressed to the full, an exposure for a still image is done with the fixed aperture value.

Claims

1. A photographic device comprising:

a release button movable to a half-pressed position and a full-pressed position;

an image sensor having a function of an electronic shutter and converting an optical image of a subject to a still image signal, said image sensor shooting video images while said release button is not pressed or is kept in said half-pressed position, and photographing a still image when said release button is moved to the full-pressed position;

a display device for displaying images on the basis of still image signals output from said image sensor;

an exposure control device that sets an electronic shutter speed of said image sensor, an aperture value and a photosensitivity according to subject brightness based on a first program while said release button is not pressed, said first program setting the electronic shutter speed to be a value preventive against flicker in a low brightness range, said exposure control device deciding an aperture value for still image photography upon said release button being pressed halfway, and so long as said release button is kept in said half-pressed position, said exposure control device using an aperture-priority type second program for setting an electronic shutter speed and a photosensitivity according to subject brightness while applying said aperture value for still image photography to said second program; and

a frame rate setting device that sets a first frame rate as a frame rate of said image sensor while said release button is not pressed, and sets a second frame rate as the photographic frame so long as said release button is kept in the half-pressed position, said second frame rate being adapted to prevent flicker.

2. A photographic device as claimed in claim 1, wherein a lower limit of a subject brightness range covered by said second program is equal to a lower limit of a subject brightness range covered by said first program.

3. A photographic device as claimed in claim 1, further comprising:

a timing generator that drives said image sensor based on parameters set therein, and generates a vertical synchronizing signal that is synchronized with a driving cycle of said image sensor; and

a timing control device that controls timing of setting parameters for still image photography in said timing generator, depending upon when said release button is pressed to the full relative to said vertical synchronizing signal, such that said parameters for still image photography are set in said timing generator either at a time immediately after said release button is pressed to the full, or at a time when said vertical synchronizing signal is generated first after said release button is pressed to the full.

4. A photographic device as claimed in claim 3, wherein said vertical synchronizing signal is generated in a cycle determined by said frame rate of said image sensor.

5. A photographic device as claimed in claim 1, wherein said first and second frame rates are 30 frames per second and 20 frames per second respectively in an area using a commercial power source of 50 Hz or 60 Hz.

6. A photographic device comprising:

an image sensor driven either in a video exposure mode or in a still image exposure mode, said image sensor being switched over from said video exposure mode to said still image exposure mode to photograph a still image in response to a release signal that is entered through an external operation;

a timing generator generating a vertical synchronizing signal that is synchronized with a driving cycle of said image sensor, and switching said image sensor to a selected one of said exposure modes by validating parameters as set therein according to said selected exposure mode, at a time when said vertical synchronizing signal is generated first after said parameters are completely set in said timing generator; and

a control device that sets parameters for said still image exposure mode in said timing generator and initializes synchronizing operation of said timing generator to restart the synchronizing operation immediately after the entry of said release signal, thereby to cause said timing generator to generate said vertical synchronizing signal immediately after the setting of said parameters for still image photography.

7. A photographic device comprising:

an image sensor having a function of an electronic shutter that gives effect to charging from when electronic shutter pulses stop being input in said image sensor;

a drive device generating drive signals including said electronic shutter pulses for driving said image sensor in predetermined frame periods, said electronic shutter pulses being generated from the start of each frame period; and

a control device that selects from among different frame periods the shortest one of those frame periods which permit charging during an exposure time for still image photography, as determined according to a subject brightness, decides timing of stopping inputting said electronic shutter pulses so as to provide said determined exposure time, and sets the selected frame period and the decided timing in said drive device in response to a release signal entered to start photographing a still image.

8. A photographic device as claimed in claim 7, further comprising a mechanical shutter that is movable between an open position letting photographic light into said image sensor and a closed position blocking photographic light from said image sensor, and is moved from said open position to said closed position when a given time has elapsed since the start of a frame period for photographing a still image, wherein said control device selects the frame period and decides the timing of stopping inputting said electronic shutter pulses so as to make a time duration from the stop of inputting said electronic shutter pulses to the blocking of photographic light by said mechanical shutter equal to said decided exposure time.

9. A photographic device as claimed in claim 7, wherein said drive device is a timing generator that validates at the start of each frame period contents as set therein by said control device, and said control device sets up said timing generator for still image photography and initializes synchronizing operation of said timing generator immediately after the entry of said release signal, thereby to restart said synchronizing operation and start a frame period for still image photography immediately after said timing generator is set up for still image photography.

10. A photographic device comprising:

an image sensor having a function of an electronic shutter that gives effect to charging from when electronic shutter pulses stop being input in said image sensor;

a mechanical shutter that is movable between an open position letting photographic light into said image sensor and a closed position blocking photographic light from said image sensor;

a drive device generating drive signals including said electronic shutter pulses for driving said image sensor; and

a control device that sets up said drive device with timing of stopping inputting said electronic shutter pulses, so as to cause said drive device to generate only a single electronic shutter pulse at the start of a frame period for still image photography in response to a release signal entered to start photographing a still image, said control device causing said mechanical shutter to move to said closed position when an exposure time determined according to a subject brightness has elapsed since said single electronic shutter pulse.

11. A photographic device as claimed in claim 10, wherein said drive device is a timing generator that validates at the start of each frame period contents as set therein by said control device, and said control device sets up said timing generator for still image photography and initializes synchronizing operation of said timing generator immediately after the entry of said release signal, thereby to restart said synchronizing operation and start the frame period for still image photography immediately after said timing generator is set up for still image photography.

12. A control method for a photographic device that shoots video images through an image sensor and displays the shot video images while a release button is not pressed or is kept in a half-pressed position, and photographs a still image through said image sensor upon said release button being pressed fully, said control method comprising steps of:

using a first program for setting an electronic shutter speed of said image sensor, an aperture value and a photosensitivity in accordance with subject brightness while said release button is not pressed, said first program setting the electronic shutter speed to a value preventive against flicker in a low brightness range;

deciding an aperture value for still image photography upon said release button being pressed halfway; and

using while said release button is kept in said half-pressed position, an aperture-priority type second program for setting an electronic shutter speed and a photosensitivity according to subject brightness while applying said aperture value for still image photography to said second program and using a frame rate adapted to prevent flicker.

13. A control method for a photographic device that is provided with a timing generator for driving an image sensor, said timing generator generating vertical synchronizing signals in synchronism with driving cycle of said image sensor, and validating parameters set therein synchronously with said vertical synchronizing signal being generated after said parameters is completely set in said timing generator, said photographic device switching said image sensor from a video exposure mode to a still image exposure mode to photograph a still image in response to a release signal entered through an external operation, said control method comprising steps of:

setting up said timing generator with parameters for driving said image sensor in said still image exposure mode immediately after the entry of said release signal; and

immediately thereafter

initializing synchronizing operation of said timing generator to restart the synchronizing operation, thereby to generate said vertical synchronizing signal to drive said image sensor in said still image exposure mode.

14. A control method for a photographic device using an image sensor having a function of an electronic shutter wherein electronic shutter pulses are input in said image sensor from the start of each frame period, and effective charging in said image sensor starts from when said electronic shutter pulses stop being input, said control method comprising steps of:

determining an exposure time for still image photography according to a subject brightness;

selecting from among different frame periods the shortest one of those frame periods which permit charging during said exposure time;

deciding timing of stopping inputting said electronic shutter pulses so as to provide said exposure time; and

photographing a still image in the selected frame period and the decided timing in response to a release signal.

15. A control method for a photographic device using an image sensor and a mechanical shutter, said image sensor having a function of an electronic shutter that gives effect to charging from when electronic shutter pulses stop being input in said image sensor, said control method comprising steps of:

inputting only a single electronic shutter pulse in said image sensor at the start of a frame period for still image photography; and

activating said mechanical shutter to block photographic light from said image sensor when an exposure time determined according to a subject brightness has elapsed since said single electronic shutter pulse.