DIGITAL CAMERA USING A FOCAL-PLANE SHUTTER

• US 20080252768A1
• Filed: 10/01/2007
• Published: 10/16/2008
• Est. Priority Date: 10/02/2006
• Status: Active Grant

• Current Assignee: PENTAX RICOH IMAGING COMPANY, LTD.
• Original Assignee: Pentax Corporation (Hoya Corporation)
• Inventors: SUZUKI, Shinichi
• Granted Patent: US 7,911,502 B2
• Time in Patent Office: Days
• US Class Current: 348/312
• CPC Class Codes: H04N 23/73 by influencing the exposure time
• CPC Class Codes: H04N 23/741 by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors
• CPC Class Codes: H04N 25/531 by controlling rolling shutters in CMOS SSIS
• CPC Class Codes: H04N 25/589 with different integration times, e.g. short and long exposures
• CPC Class Codes: H04N 25/70 SSIS architectures; Circuits associated therewith

Abstract

A digital camera includes an image pickup device; a focal plane shutter including a shutter leading curtain and a shutter trailing curtain; a timer for measuring exposure time; a shutter controller which commences measurement of an exposure time when the shutter leading curtain starts traveling, and drives the shutter trailing curtain upon completing the exposure time measurement; and a charge readout controller which reads out electric charges accumulated by the image pickup device during the exposure time at least twice, first before the shutter trailing curtain commences traveling upon the shutter leading curtain commencing traveling and second upon the shutter trailing curtain commencing traveling. The charge readout controller carries out the electric charge readout, before the shutter trailing curtain commences traveling, at a scanning speed in synchronization with a travel speed of the shutter leading curtain in a same direction of the traveling shutter leading curtain.

Claims

1. A digital camera comprising:

a solid-state image pickup device which includes a two-dimensional matrix of unit cells arranged in two directions and can selectively read out electric charges accumulated in said unit cells, each of said unit cells including a photoelectric conversion element;

a focal plane shutter including a shutter leading curtain and a shutter trailing curtain which move in one of said two directions;

a timer which measures an exposure time;

a shutter controller which commences measurement of an exposure time via said timer when said shutter leading curtain starts traveling, and drives said shutter trailing curtain upon said timer completing said measurement of said exposure time; and

a charge readout controller which reads out electric charges accumulated by each unit cell of said solid-state image pickup device during said exposure time at least twice, first before said shutter trailing curtain commences traveling upon said shutter leading curtain commencing traveling and second upon said shutter trailing curtain commencing traveling;

wherein said charge readout controller carries out said electric charge readout, before said shutter trailing curtain commences traveling, at a scanning speed which is in synchronization with a travel speed of said shutter leading curtain in a same direction of said traveling shutter leading curtain.

2. The digital camera according to claim 1, wherein said charge readout controller sets a readout timing of said solid-state image pickup device so as to vary in accordance with the travel speed of said shutter traveling curtain and to readout in a direction identical to said shutter traveling direction, and sequentially reads out said accumulated charges from said solid-state image pickup device at each row of said unit cells arranged along a direction orthogonal to said shutter traveling direction with said scanning speed being brought in synchronization with said travel speed of said shutter leading curtain.

3. The digital camera according to claim 2, wherein said charge readout controller comprises:

a position detector for obtaining positional information on said shutter leading curtain; and

charge-readout timing tables which associate said travel speed of said shutter leading curtain with said timing,

wherein said charge readout controller sequentially reads out said accumulated charges from said solid-state image pickup device at each row of said unit cells according to one of said charge-readout timing tables which corresponds to a travel speed of said shutter leading curtain which is calculated from said positional information on said shutter leading curtain.

4. The digital camera according to claim 1, wherein a first exposure time, in said first reading-out of said electric charges before said shutter trailing curtain commences traveling upon said shutter leading curtain commencing traveling, is different from a second exposure time in said second reading-out of said electric charges upon said trailing curtain commencing traveling.

5. The digital camera according to claim 4, wherein said first exposure time is longer than said second exposure time.

6. The digital camera according to claim 4, wherein a sum of said first exposure time and said second exposure time is greater than a correct exposure time.

7. The digital camera according to claim 1, further comprising an image synthesizing device which synthesizes a first image of said first accumulated charge with a second image of said second accumulated charge.

8. The digital camera according to claim 1, wherein when reading out accumulated charges from said solid-stage imaging device upon commencement of travel of said shutter leading curtain, said charge readout controller carries out said electric charge readout upon completion of said travel of said shutter trailing curtain.

9. The digital camera according to claim 1, wherein said charge readout controller reads out said accumulated charges from said solid-state imaging device at once upon commencement of travel of said shutter trailing curtain.

10. The digital camera according to claim 3, wherein said position detector comprises a photo-interrupter.

11. The digital camera according to claim 1, wherein said solid-state image pickup device comprises a CMOS image sensor.

12. A digital camera comprising:

a solid-state image pickup device which includes a two-dimensional matrix of unit cells arranged in two directions and can selectively read out electric charges accumulated in said unit cells, each of said unit cells including a photoelectric conversion element;

a focal plane shutter including a shutter leading curtain and a shutter trailing curtain which move in one of said two directions;

a timer which measures at least a first exposure time and subsequently a second exposure time which are different from each other;

a shutter controller which controls operations of said shutter leading curtain and said shutter trailing curtain so that said shutter leading curtain starts traveling at a commencement of measurement of said timer and so that said shutter trailing curtain starts traveling on completion of said measurement of said timer;

a mid-exposure charge readout controller which sequentially reads out a first accumulated charge accumulated in each of said unit cells for said first exposure time in order of a traveling direction of said shutter leading curtain and said shutter trailing curtain wherein a scanning speed of readout of electric charge from said solid-state image pickup device is in synchronization with a travel speed of said shutter leading curtain immediately after a lapse of said first exposure time from commencement of travel of said shutter leading curtain; and

a post-exposure charge readout controller which reads out a second accumulated charge accumulated in each of said unit cells for said second exposure time upon completion of said travel of said shutter trailing curtain.