Focusing method, suitable for an image capturing apparatus using in an environment of low brightness and image capturing apparatus using the same

• US 8,139,137 B2
• Filed: 11/15/2007
• Issued: 03/20/2012
• Est. Priority Date: 06/14/2007
• Status: Expired due to Fees

• Current Assignee: Novatek Microelectronics Corporation (Novatek Microelectronics Corp Limited)
• Original Assignee: Novatek Microelectronics Corporation (Novatek Microelectronics Corp Limited)
• Inventors: Lin, Chia-Ho, Tsai, Jung-Che, Chiang, Ming-Feng
• Primary Examiner(s): Ye, Lin
• Assistant Examiner(s): COWAN, EUEL K
• Application Number:
  US11/940,324
• Publication Number:
  US 20080309779A1
• Time in Patent Office: 1,587 Days
• Field of Search: 348/220.1, 348/345, 348/349, 348/356
• US Class Current: 348/345
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method
• CPC Class Codes: H04N 23/81 for suppressing or minimising disturbance in the image signal generation

Abstract

A focusing method, suitable for an image capturing apparatus using in an environment of low brightness, is provided herein. The focusing method includes that an image sensing unit in the image capturing apparatus is wholly or partially divided into a plurality of regions, and digital image data sensed by the image sensing unit is divided into a plurality of sets corresponding to the regions of the image sensing unit. The regional image data corresponding to each of the regions are summed up during the focusing step, so as to obtain a sum of data for each region. Each sum of data is used to calculate a corresponding contrast value, and the contrast value is used to perform calculations for the focusing step, so as to obtain a focus.

Claims

1. A focusing method suitable for an image capturing apparatus in an environment of low brightness, the focusing method comprising:

a digital image processor dividing a digital image data captured by the image capturing apparatus into a plurality of regional digital image data corresponding to a plurality of regions;

said digital image processor summing up the plurality of the regional digital image data for each of the regions using digital image data from its own region to obtain a plurality of sums of data for each of the regions;

using the sums of data of each of the regions to calculate a plurality of contrast values with each contrast value corresponding to its own region; and

using the plurality of contrast to perform calculations for the focusing step to obtain a focus.

2. The focusing method as claimed in claim 1, wherein the step of summing up the plurality of the regional digital image data corresponding to each of the regions includes dividing the data in each of the regions into a plurality of sets of sub regions, and summing up all of the digital image data corresponding to the sub regions.

3. The focusing method as claimed in claim 2, wherein the step of summing up the plurality of the regional digital image data corresponding to the sub region is summing up a plurality of horizontal lines of the digital image data.

4. The focusing method as claimed in claim 2, wherein the step of summing up the plurality of the regional digital image data corresponding to the sub region is summing up a plurality of vertical lines of the digital image data.

5. The focusing method as claimed in claim 2, wherein the step of summing up the plurality of the regional digital image data corresponding to the sub region is summing up a plurality of block data of the digital image data in the sub region.

6. The focusing method as claimed in claim 1, wherein the step of summing up the plurality of the regional digital image data corresponding to each region comprises summing up the digital image data obtained by a plurality of frames in each region within a predetermined time period.

7. The focusing method as claimed in claim 6, wherein the step of summing up the plurality of the regional digital image data obtained by the plurality of frames in each region further comprises adding a motion estimation mechanism to estimate an image moving direction, so as to adjust the digital image data accordingly.

8. An image capturing apparatus suitable for focusing in an environment of low brightness, the image capturing apparatus comprising:

an image sensing unit, for sensing an object and obtaining a digital image data;

an image processing unit, for dividing the digital image data into a plurality of regional image data corresponding to a plurality of regions, and summing up the plurality of regional image data for each of the regions using digital image data from its own region, so as to obtain a plurality of sums of data for each of the regions and to calculate a plurality of contrast values with each of the contrast values corresponds to its own region according to the sums of data; and

a focus adjusting module, for performing calculations for the focusing step according to the plurality of contrast values, so as to obtain a focus.

9. The image capturing apparatus as claimed in claim 8, wherein in the image processing unit, the step of summing up the regional image data corresponding each region comprises dividing the data in each region into a plurality of sets of sub regions, and summing up the digital image data corresponding to each of the sub regions.

10. The image capturing apparatus as claimed in claim 9, wherein in the image processing unit, the step of summing up the regional image data corresponding to the sub region is summing up a plurality of horizontal lines of the digital image data.

11. The image capturing apparatus as claimed in claim 9, wherein in the image processing unit, the step of summing up the regional image data corresponding to the sub region is summing up a plurality of vertical lines of the digital image data.

12. The image capturing apparatus as claimed in claim 9, wherein in the image processing unit, the step of summing up the regional image data corresponding to the sub region is summing up a plurality of block data of the digital image data in the sub region.

13. The image capturing apparatus as claimed in claim 8, wherein in the image processing unit, the step of summing up the regional image data corresponding to each region comprises summing up the regional image data obtained by a plurality of frames in each region within a predetermined time period.

14. The image capturing apparatus as claimed in claim 13, wherein in the image processing unit, the step of summing up the regional image data obtained by the plurality of frames in each region further comprises adding a motion estimation mechanism to estimate the moving direction of the image, so as to adjust the digital image data.

15. A focusing method suitable for an image capturing apparatus in an environment of low brightness, the focusing method comprising:

a digital image processor dividing a portion of a digital image data captured by the image capturing apparatus into a plurality of regional digital image data corresponding to a plurality of predefined regions;

said digital image processor summing up the plurality of the regional digital image data for each of the predefined regions using digital image data from its own region to obtain a plurality of sums of data for each of the predefined regions;

using the sums of data of each of the regions to calculate a plurality of contrast values with each of the contrast values corresponding to its own predefined regions;

and using the plurality of contrast values to perform calculations for the focusing step to obtain a focus.

16. The focusing method as claimed in claim 15, each of the predefined regions being divided into a plurality of sets of sub regions, and the sum of data for each of the predefined regions is obtained by summing up all of the digital image data corresponding to the sub regions.

17. The focusing method as claimed in claim 16, wherein the digital image data corresponding to the sub regions is a plurality of horizontal lines of the digital image data.

18. The focusing method as claimed in claim 16, wherein the digital image data corresponding to the sub regions is summing up a plurality of vertical lines of the digital image data.

19. The focusing method as claimed in claim 16, wherein the digital image data corresponding to the sub regions is a plurality of block data of the digital image data.

20. The focusing method as claimed in claim 15, wherein the step of summing up the plurality of the regional digital image data corresponding to each predefined region comprises summing up the digital image data obtained by a plurality of frames in each region within a predetermined time period.