Method and system for image stabilization

• US 20070296821A1
• Filed: 06/22/2006
• Published: 12/27/2007
• Est. Priority Date: 06/22/2006
• Status: Active Grant

• Current Assignee: 2011 Intellectual Property Asset Trust (Nokia Corporation)
• Original Assignee: Nokia Corporation
• Inventors: Kakkori, Hannu
• Granted Patent: US 7,952,612 B2
• Time in Patent Office: Days
• US Class Current: 348/208.6
• CPC Class Codes: H04N 2007/145 Handheld terminals
• CPC Class Codes: H04N 23/68 for stable pick-up of the scene, e.g. compensating for camera body vibrations
• CPC Class Codes: H04N 23/6812 based on additional sensors, e.g. acceleration sensors
• CPC Class Codes: H04N 23/6845 by combination of a plurality of images sequentially taken
• CPC Class Codes: H04N 23/951 by using two or more images to influence resolution, frame rate or aspect ratio

Abstract

A motion sensor is used to sense the movement of the camera during an exposure period. The camera has an image sensor to form one or more exposures. When the movement is within a certain range, the exposures are used to provide one or more frames so that an image can be constructed based on the frames. In one embodiment, the exposure period is divided into several short intervals in order to capture several image frames and only the image frames captured when the position of the camera is within a predetermined range are used to form the final image. The exposure time for each frame is small in order to reduce the motion blur degradation of the individual frames. If the camera is stable and substantially stationary relative to the scene, then all or many of the shorter frames are used to form the final image.

Claims

1. A method comprising:

exposing a projected image on an image sensor of an imaging system at least part of an exposure period for attaining one or more exposures;

sensing movement of the imaging system during the exposure period for obtaining a movement amount relative to an initial position of the imaging system in the exposure period; and

constructing the acquired image based on one or more exposures attained when the movement amount is within a predetermined movement range in the exposure period.

2. The method of claim 1, wherein said one or more exposures attained when the movement amount is within the predetermined movement range form a single image frame during the exposure period, said method further comprising:

capturing the single image frame after the exposure period for constructing the acquired image.

3. The method of claim 1, wherein said one or more exposures attained when the movement amount is within the predetermined movement range separately form one or more image frames during the exposure period, said method further comprising:

capturing the image frames at least during the exposure period for constructing the acquired image.

4. The method of claim 1, wherein the exposure period is divided into a plurality of shorter time periods and said one or more exposures attained during at least part of the exposure period form one or more image frames, each image frame for one shorter time period, said method further comprising:

capturing said one or more image frames at least during the exposure period; and

selecting the captured image frames formed from the one or more exposures when the movement amount is within the predetermined movement range for constructing the acquired image.

5. The method of claim 1, further comprising

preventing the projected image from reaching the image sensor when the movement amount is outside the predetermined movement range.

6. The method of claim 1, wherein the image sensor comprises an array of pixels, each pixel having a pixel area, and the predetermined movement range is determined based on one or more pixel areas.

7. The method of claim 1, wherein the imaging system comprises an optical system for providing the projected image on the image sensor, and the predetermined movement range is determined based a focal distance of the optical system.

8. The method of claim 1, wherein the predetermined movement range is determined based on brightness of at least part of light forming the projected image.

9. An imaging system comprising:

an image sensor for attaining one or more exposures during an exposure period;

a movement sensor for sensing movement of the imaging system during the exposure period for obtaining a movement amount relative to an initial position of the imaging system in the exposure period; and

a processor, operatively connected to the image sensor, for constructing an image based on one or more exposures attained when the movement amount is within a predetermined movement range.

10. The imaging system of claim 9, wherein said one or more exposures attained when the movement amount is within the predetermined movement range form a single image frame during the exposure period, and wherein the image is constructed based on the single image frame captured after the exposure period.

11. The imaging system of claim 9, wherein said one or more exposures attained when the movement amount is within the predetermined movement range separately form one or more image frames during the exposure period, and wherein the image is constructed based on the one or more image frames captured at least during the exposure period.

12. The imaging system of claim 9, wherein the image sensor is configured to divide the exposure period into a plurality of shorter time periods and said one or more exposures attained during at least part of the exposure period form one or more image frames, each image frame for one shorter time period, and wherein the processor is configured to capture said one or more image frames at least during the exposure period and to select the captured image frames formed from the one or more exposures when the movement amount is within the predetermined movement range for constructing the image.

13. The imaging system of claim 9, further comprising

an optical system for providing a projected image on the image sensor so as to allow the image sensor to attain the one or more exposures during the exposure period.

14. The imaging system of claim 13, further comprising

a shutter, positioned in relationship to the optical system, for preventing the projected image from reaching the image sensor when the movement amount is outside the predetermined movement range

15. The imaging system of claim 9, further comprising

an electronic circuit operatively connected to the image sensor for preventing the image sensor from attaining an exposure when the movement amount is outside the predetermined movement range.

16. The imaging system of claim 9, wherein the movement sensor provides a signal to indicate whether the movement amount is within the predetermined movement range so as to allow the image sensor to attain said one or more exposures only when the movement amount is within the predetermined range.

17. The imaging system of claim 9, wherein the movement sensor comprises an accelerometer.

18. An image stabilization module for use in an imaging system, the imaging system comprising an image sensor, an optical module for projecting an image on the image sensor so as to allow the image sensor to attain one or more exposures during an exposure period, and a processor, operatively connected to the image sensor, for constructing an image based on one or more exposures, said image stabilization module comprising:

a movement sensor for sensing movement of the imaging system during the exposure period; and

a processor, operatively connected to the movement sensor, for determining a movement amount of the imaging system relative to an initial position of the imaging system in the exposure period, and for providing a signal indicative of wherein the movement amount is within a predetermined movement range to the processor so that the processor attains the one or more exposures only when the movement amount is within the predetermined range.

19. The image stabilization module of claim 18, further comprising

a light shutter, operatively connected to the signal providing means, for preventing the projected image from reaching the image sensor when the movement amount is out of the predetermined movement range.

20. An imaging system, comprising:

means for sensing an image;

means for exposing a projected image on the image sensing means during an exposure period so as to allow the image sensing means to attain one or more exposures;

means for sensing movement of the imaging system during the exposure period for obtaining a movement amount relative to an initial position of the imaging system in the exposure period; and

means for constructing the acquired image based on one or more exposures attained when the movement amount is within a predetermined movement range in the exposure period.

21. The imaging system of claim 20, further comprising

means for capturing one or more image frames for constructing the acquired image.

22. The imaging system of claim 21, further comprising:

means for selecting the captured image frames for constructing the acquired image.

23. The imaging system of claim 20, further comprising:

means for preventing the projected image from forming an exposure when the movement amount is outside the predetermined movement range.