Exposure control for an image pickup apparatus that uses an electronic flash

• US 6,278,490 B1
• Filed: 05/20/1997
• Issued: 08/21/2001
• Est. Priority Date: 05/23/1996
• Status: Expired due to Fees

• Current Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Original Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Inventors: Fukuda, Hidetoshi, Inagaki, Osamu, Kakinuma, Minoru, Kamishima, Gakuji
• Primary Examiner(s): Garber, Wendy R.
• Assistant Examiner(s): NGUYEN, LUONG TRUNG
• Application Number:
  US08/859,678
• Time in Patent Office: 1,554 Days
• Field of Search: 348/227, 348/228, 348/229, 348/230, 348/241, 348/362, 348/371, 348/370, 348/294, 348/68, 348/220, 348/302, 348/303, 348/304, 348/297, 358/475, 235/462.06
• US Class Current: 348/362
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene
• CPC Class Codes: H04N 23/74 by influencing the scene brightness using illuminating means

Abstract

An image pickup apparatus including a solid-state image pickup device for photoelectrically converting incident light from an object into an electrical signal and outputting the electrical signal, an electronic flash tube for irradiating light onto the object, and a system controller for controlling the light emission timing of the electronic flash tube. The electronic flash tube is caused to emit light in the vertical blanking period of the solid-state image pickup device. The invention is to also provide an image pickup apparatus having a solid-state image pickup device capable of performing photoelectric conversion and reading out the charges accumulated for an arbitrary time, a field memory for storing image data obtained by performing predetermined processing for the readout signal, an image synthesizing unit for synthesizing an immediately preceding field image and a new image from the image pickup device, and an electronic flash unit. Even when the image is picked up using short-time light emission of the electronic flash unit or the like, two images with different exposure amounts are obtained and synthesized to generate an image having an appropriate and wide dynamic range.

Claims

1. An image pickup apparatus comprising:

an X-Y address type solid-state image pickup means for photoelectrically converting incident light from an object into an electrical signal and outputting the electrical signal;

an electronic flash means for irradiating light onto said object;

control means for causing said electronic flash means to emit light in vertical blanking periods of different field periods of said solid-state image pickup means in different light emission amounts; and

synthesizing means for synthesizing a plurality of images obtained by exposure based on light emission of said electronic flash means;

wherein said synthesizing means comprises a density connection circuit for synthesizing image data of two frames with different exposure amounts to obtain image data of one frame whose dynamic range is widened.

3. An apparatus according to claim 1, wherein said synthesizing means comprises:

detection means for detecting a light emission amount of said electronic flash means, and

correction means for correcting a video signal obtained from said image pickup means on the basis of the light emission amount detected by said detection means.

5. An apparatus according to claim 3, wherein said detection means detects variations in light emission amount on the basis of the electrical signal output by said image pickup means.

7. An apparatus according to claim 3, wherein said detection means comprises a light-receiving device for receiving the light from said object and converting the light into the electrical signal.

9. An apparatus according to claim 1, wherein said control means operates on the basis of an output from a light-receiving device for receiving the light from said object and converting the light into the electrical signal.

2. An image pickup apparatus comprising:

a solid-state image pickup means for nondestructively reading out an image signal;

an electronic flash means for irradiating light onto an object;

first control means for accumulating a solid-state image pickup means signal for a first accumulation time and thereafter nondestructively reading out the signal to obtain a first signal;

second control means for accumulating the solid-state image pickup means signal for a second accumulation time longer than the first accumulation time and thereafter reading out the signal to obtain a second image signal; and

third control means for causing said electronic flash means to emit light at an interval not longer than the first accumulation time.

4. An apparatus according to claim 2, wherein said synthesizing means comprises:

detection means for detecting a light emission amount of said electronic flash means, and

correction means for correcting a video signal obtained from said solid-state image pickup means on the basis of the light emission amount detected by said detection means.

6. An apparatus according to claim 4, wherein said detection means detects variations in light emission amount on the basis of the solid-state image pickup means signal.

8. An apparatus according to claim 4, wherein said detection means comprises a light-receiving device for receiving the light from said object and converting the light into the solid-state image pickup means signal.

10. An apparatus according to claim 2, wherein said first, second and third control means operate on the basis of an output from a light-receiving device for receiving the light from said object and converting the light into the solid-state image pickup means signal.

11. An image pickup apparatus comprising:

an image pickup means for obtaining an image signal corresponding to a self image pickup field;

exposure time control means for controlling an effective exposure time for said image pickup means to give effective exposure to said image pickup means during a relatively long first time interval so as to pick up an image of a portion having a relatively low luminance in said image pickup field, and to give effective exposure to said image pickup means during a relatively short second time interval adjacent to the first time interval so as to pick up an image of a portion having a relatively high luminance in said image pickup field;

synthesizing means for synthesizing image data representing one image on the basis of first image signal data and second image signal data so as to represent the image of said portion having the relatively low luminance on the basis of the first image signal data obtained in correspondence with the first time interval for said image pickup means, and to represent the image of said portion having the relatively high luminance on the basis of the second image signal data obtained in correspondence with the second time interval;

flash light-emitting means for controlling a light emission form; and

light emission control means for controlling the light emission form of said flash light-emitting means so as to prevent a total exposure amount in the second time interval from exceeding that in the first time interval when said flash light-emitting means is caused to emit light for the first and second time intervals, and wherein said light emission control means controls the light emission form so as to select a ratio of light emission amounts between light emission of said flash light-emitting means in the first time interval and that in second time interval, said ratio of light emission amounts being substantially equal to a ratio of the first time interval to the second time interval.

12. An apparatus according to claim 11, wherein said light emission control means controls an exposure amount of light emission by controlling a light emission amount per unit time for each light emission of said flash light-emitting means.

13. An apparatus according to claim 11, wherein said light emission control means controls an exposure amount of light emission by controlling a light emission amount per unit time for each light emission of said flash light-emitting means.

14. An apparatus according to claim 11, wherein said light emission control means controls an exposure amount of light emission by controlling a light emission time for each light emission of said flash light-emitting means while setting a predetermined light emission amount per unit time.

15. An apparatus according to claim 11, wherein said light emission control means controls an exposure amount of light emission by controlling a light emission time for each light emission of said flash light-emitting means while setting a predetermined light emission amount per unit time.

16. An apparatus according to claim 11, wherein said light emission control means controls an exposure amount of light emission by controlling the number of times of light-emitting operations for each light emission of said flash light-emitting means while setting a predetermined light emission amount per unit time.

17. An apparatus according to claim 11, wherein said light emission control means controls an exposure amount of light emission by controlling the number of times of light-emitting operations for each light emission of said flash light-emitting means while setting a predetermined light emission amount per unit time.

18. An apparatus according to claim 12, wherein said light emission control means controls the light emission form so as to make said flash light-emitting means emit light in a time period of the first time interval, which is close to the second time interval, and in a time period of the second time interval, which is close to the first time interval.

19. An apparatus according to claim 13, wherein said light emission control means controls the light emission form so as to make said flash light-emitting means emit light in a time period of the first time interval, which is close to the second time interval, and in a time period of,the second time interval, which is close to the first time interval.

20. An apparatus according to claim 14, wherein said light emission control means controls the light emission form so as to make said flash light-emitting means emit light in a time period of the first time interval, which is close to the second time interval, and in a time period of the second time interval, which is close to the first time interval.

21. An apparatus according to claim 13, wherein said light emission control means controls the light emission form so as to make said flash light-emitting means substantially continuously emit light in a time period of the first time interval, which is close to the second time interval, and in a time period of the second time interval, which is close to the first time interval.

22. An apparatus according to claim 14, wherein said light emission control means controls the light emission form so as to make said flash light-emitting means substantially continuously emit light in a time period of the first time interval, which is close to the second time interval, and in a time period of the second time interval, which is close to the first time interval.