Image pickup apparatus and method for controlling pixel reading using a shake determination

• US 7,714,890 B2
• Filed: 04/26/2006
• Issued: 05/11/2010
• Est. Priority Date: 04/26/2005
• Status: Expired due to Fees

• Current Assignee: Olympus Imaging Corporation (Olympus Corporation)
• Original Assignee: Olympus Imaging Corporation (Olympus Corporation)
• Inventors: Imai, Yuji, Okubo, Mitsumasa
• Primary Examiner(s): Henn; Timothy J
• Application Number:
  US11/412,190
• Publication Number:
  US 20060238621A1
• Time in Patent Office: 1,476 Days
• Field of Search: 34820899-2082, 348/208.4, 348/208.6, 348/208.12, 348/208.16, 348/294, 348/296, 348/297
• US Class Current: 348/208.16
• CPC Class Codes: G03B 2217/005 Blur detection
• CPC Class Codes: G03B 7/097 for control of both exposure time and aperture
• CPC Class Codes: H04N 23/68 for stable pick-up of the scene, e.g. compensating for camera body vibrations
• CPC Class Codes: H04N 23/6811 based on the image signal
• CPC Class Codes: H04N 23/6812 based on additional sensors, e.g. acceleration sensors
• CPC Class Codes: H04N 23/684 performed by controlling the image sensor readout, e.g. by controlling the integration time

Abstract

An image pickup apparatus configured to pick up a still image includes an image pickup device having a plurality of pixels to convert an object image formed by an optical system to an electric charge. A pixel reading circuit operates in either a first reading mode for reading electric charges obtained from the respective pixels of the image pickup device on a pixel by pixel basis or a second reading mode for adding and reading the electric charges obtained from the respective pixels of the image pickup device. A controller evaluates camera shake during exposure. When an evaluation level of the shake is greater than a predetermined level, this controller controls the pixel reading circuit to operate in the second reading mode. when the evaluation level is smaller than the predetermined level, the controller controls the pixel reading circuit to operate in the first reading mode.

Claims

1. An image pickup apparatus configured to pick up an image, the apparatus comprising:

an image pickup device which has a plurality of pixels to convert an object image formed by an optical system to an electric charge;

a pixel reading circuit which operates in either a first reading mode for reading electric charges obtained from respective pixels of the image pickup device on a pixel by pixel basis or a second reading mode for adding and reading the electric charges obtained from respective pixels of the image pickup device; and

a controller which evaluates a shake of the apparatus during exposure, which operates the pixel reading circuit in the second reading mode when an evaluation level of the camera shake is greater than a predetermined level, and which operates the pixel reading circuit in the first reading mode when the evaluation level is smaller than the predetermined level.

2. The image pickup apparatus according to claim 1, wherein the controller obtains the evaluation level prior to exposure of the image pickup device.

3. The image pickup apparatus according to claim 1, further comprising a shake detecting section which detects a shake of the image pickup device,

wherein the controller obtains the evaluation level based on an output from the camera shake detecting section.

4. The image pickup apparatus according to claim 3, further comprising an exposure time setting section which sets an exposure time of the image pickup device,

wherein the controller obtains the evaluation level based on the exposure time and a focal distance of the optical system in addition to an output of the shake detecting section.

5. The image pickup apparatus according to claim 3, wherein the controller obtains the evaluation level from the shake obtained by the shake detecting section during exposure of the image pickup device.

6. The image pickup apparatus according to claim 5, wherein the second reading mode is provided as an N² pixel additive reading mode for adding and reading the electric charges on an N² by N² pixel basis.

7. The image pickup apparatus according to claim 5, wherein the second reading mode includes:

an N² pixel additive reading mode for adding and reading the electric charges on an N² by N² pixel basis; and

an M² pixel additive reading mode for adding and reading the electric charges on an M² by M² pixel basis (where M is an integer of 2 or more, and has a relationship of N>

M), and

the controller controls the pixel reading circuit to operate in the N² pixel additive reading mode in the case where the evaluation level has reached a first threshold level from the time point of exposure start of the image pickup device to a first time point, and controls the pixel reading circuit to operate in the M² pixel additive reading mode in the case where the evaluation level does not reach the first threshold level from the time point of exposure start of the image pickup device to the first time point but the evaluation level has reached a second threshold level that is a predetermined level smaller than the first threshold level from the first time point to a second time point.

8. The image pickup apparatus according to claim 5, wherein the shake detecting section includes an angle velocity sensor.

9. The image pickup apparatus according to claim 5, wherein the evaluation level is obtained as an integral value of the shake obtained by the shake detecting section from a time point of exposure start of the image pickup device.

10. The image pickup apparatus according to claim 9, wherein the evaluation level is provided as a blurring diameter of a circle including a locus of the shake from a time point of exposure start of the image pickup device.

11. The image pickup apparatus according to claim 9, wherein the controller controls the pixel reading circuit to operate in the second reading mode in the case where the evaluation level has reached a first threshold level from a time point of exposure start to a first time point.

12. The image pickup apparatus according to claim 11, wherein the controller terminates the exposure of the image pickup device immediately when the evaluation level has reached the first threshold level from the time point of exposure start to the first time point, and controls the pixel reading circuit to operate in the second reading mode.

13. The image pickup apparatus according to claim 12, further comprising an amplifier circuit which amplifies an electrical signal based on the electric charges read from the image pickup device at a variable amplification rate,

wherein the controller terminates the exposure of the image pickup device, controls the pixel reading circuit to operate in the second reading mode, and then, sets the amplification rate of the amplifier circuit in accordance with a time interval from a time point of exposure start of the image pickup device to a time point of exposure termination.

14. The image pickup apparatus according to claim 3, wherein the shake detecting section includes an angle velocity sensor.

15. The image pickup apparatus according to claim 3, further comprising an image processing circuit which acquires image data from the electric charges read from the pixel reading circuit,

wherein the shake detecting section detects the shake from the image data.

16. The image pickup apparatus according to claim 15, wherein the shake detecting section detects the shake quantity in respective areas which is divided into a plurality of areas from a whole area of the image data, obtains a maximum value of the shake quantity detected in each area, and detects the shake from the maximum value of the image shake quantity.

17. The image pickup apparatus according to claim 15, wherein the shake detecting section compares a plurality of image data obtained from the image processing circuit in different time points from each other, thereby detecting the shake quantity and detecting the shake from the image shake quantity.

18. The image pickup apparatus according to claim 1, wherein the pixel reading circuit reads an electric charges by a first photographic sensitivity when operating in the first reading mode, and reads an electric charges by a second photographic sensitivity that is higher in sensitivity than the first imaging sensitivity when operating in the second reading mode.

19. The image pickup apparatus according to claim 1, further comprising an object luminance detecting section which detects object luminance,

wherein the controller obtains the evaluation level based on the object luminance and a focal distance of the optical system.

20. The image pickup apparatus according to claim 19, wherein the controller determines an exposure time of the image pickup device based on the object luminance detected by the object luminance detecting section and the focal distance of the optical system, and obtains the evaluation level based on the exposure time and the focal distance of the optical system.

21. The image pickup apparatus according to claim 19, wherein the predetermined level is set in accordance with the focal distance of the optical system.

22. The image pickup apparatus according to claim 19, further comprising a photographing mode selecting section which selects one photographing mode from among a plurality of photographing modes,

wherein the predetermined level is set in accordance with the photographing mode selected by the photographing mode selecting section.

23. The image pickup apparatus according to claim 19, wherein the controller provides hysteresis with respect to an object luminance value changing point between the first reading mode and the second reading mode.

24. The image pickup apparatus according to claim 23, wherein the controller determines an exposure time of the image pickup device based on the object luminance detected by the object luminance detecting section and the focal distance of the optical system, and obtains the evaluation level based on the exposure time and the focal distance of the optical system.

25. An image pickup apparatus configured to pick up an image, the apparatus comprising:

an image pickup device which has a plurality of pixels to convert an object image formed by an optical system to an electric charge;

a pixel reading circuit which operates in either a first reading mode for reading electric charges obtained form the respective pixels of the image pickup device on a pixel by pixel basis or a second reading mode for adding and reading the electric charges obtained from the respective pixels of the image pickup device;

an object shake detecting section which detects an object shake quantity generated by a motion of an object; and

a controller which operates the pixel reading circuit in the second reading mode when an object shake quantity during exposure of the image pickup device is greater than a predetermined level, and which operates the pixel reading circuit in the first reading mode when the object shake quantity is smaller than the predetermined level.

26. The image pickup apparatus according to claim 25, further comprising an image processing circuit which acquires image data from the electric charges read from the pixel reading circuit,

wherein the object shake detecting section includes:

a shake detecting sensor which detects a shake quantity of the image pickup apparatus; and

an image shake detecting circuit which detects a shake quantity of an image from the image data obtained by the image processing circuit,

wherein the object shake detecting section compares the shake quantity detected by the shake detecting sensor and the image shake detected by the image shake detecting circuit, thereby detecting the object shake.

27. A method for picking up an image, comprising:

evaluating a level of a camera shake during exposure prior to picking up an image;

starting exposure for acquiring the image;

terminating the exposure; and

adding and reading electric charges of each pixel obtained by the exposure when the evaluation level of the camera shake obtained by the evaluation is greater than a predetermined level, and reading electric charges of each pixel obtained by the exposure on a pixel by pixel basis when the evaluation level is smaller than the predetermined level.

28. The method according to claim 27, wherein a photographic sensitivity, when the evaluation level is smaller than the predetermined level, is set to a first imaging sensitivity, and an imaging sensitivity, when the evaluation level is greater than the predetermined level, is set to a second imaging sensitivity that is higher in an sensitivity than the first imaging sensitivity.

29. An image pickup apparatus configured to pick up an image, the apparatus comprising:

an image pickup device having a plurality of pixels to convert an object image formed by an optical system to an electric charge;

an electric charge adder circuit which adds electric charges obtained from respective pixels of the image pickup device on a predetermined pixel size by pixel size basis;

a controller which selects either an individual pixel reading mode for reading the electric charges obtained from the respective pixels of the image pickup device on a pixel by pixel basis, or a pixel additive reading mode for operating the electric charge adder circuit and adding and reading the electric charges obtained from the respective pixels of the image pickup device on the predetermined pixel size by pixel size basis based on a shake of the apparatus occurring during an exposure of the image pickup device.

30. A method for picking up an image, comprising:

starting exposure for acquiring an image;

evaluation a magnitude of a camera shake during the exposure;

terminating the exposure; and

when an evaluation level of the camera shake obtained by the evaluation is greater than a predetermined level, adding and reading electric charges for each pixel obtained by the exposure, and when the evaluation level is smaller than the predetermined level, reading the electric charges for each pixel obtained by the exposure on a pixel by pixel basis.