Method and system for automatically focusing a camera

• US 7,909,256 B2
• Filed: 12/31/2005
• Issued: 03/22/2011
• Est. Priority Date: 12/31/2005
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola Mobility, Inc. (Lenovo Group Ltd.)
• Inventors: Frenzer, Michael W., He, Fan
• Primary Examiner(s): Le; Thien M.
• Assistant Examiner(s): Mai; Thien T
• Application Number:
  US11/323,499
• Publication Number:
  US 20070152062A1
• Time in Patent Office: 1,907 Days
• Field of Search: 235/462.23, 235/462.1, 235/472.01, 235/472.02, 235/454, 348/356, 348/345, 348/223.1, 348/143, 396/121, 396/122, 359/391
• US Class Current: 235/462.23
• CPC Class Codes: G03B 13/36 Autofocus systems
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method

Abstract

A method and system for automatically focusing an image received by an image capturing unit (100) relative to a target is disclosed. The target is present in a sequence of one or more scanned frames. The method includes dividing (302) each frame from the sequence of one or more scanned frames in a plurality of sections. The method further includes iteratively determining (304) a relative focus of the target within each section of the plurality of sections. The method further includes adjustment (306) of a position of at least a first light path adjustment element in response to the determined relative focus.

Claims

1. A method in an image capture unit having at least a first light path adjustment element for automatically focusing an image received by the image capture unit relative to a target, the target being present in a sequence of multiple scanned frames, the method comprising:

dividing into a plurality of sections, each frame from the sequence of multiple scanned frames; and

iteratively performing a plurality of times in connection with each frame as the frame is scanned from the image capture unit, wherein each iteration is performed relative to alternate sections of the frame,

a determination of a relative focus of the target within the corresponding section of the frame, and

an adjustment of a position of at least the first light path adjustment element in response to the determined relative focus.

2. A method in accordance with claim 1, wherein the sections correspond to sequentially scanned portions of the respective frame.

3. A method in accordance with claim 2, wherein each section includes a first part and a second part;

and the determination is performed during the scanning of the first part of the section, and the adjustment is performed during the scanning of the second part of the section.

4. A method in accordance with claim 1, wherein the determination of a relative focus includes measuring a contrast value of the corresponding section.

5. A method in accordance with claim 4, wherein measuring a contrast is incorporated as part of measuring a modulation transfer function.

6. A method in accordance with claim 1, wherein each frame of multiple different frames is divided in an equivalent manner, thereby resulting in associated sections in multiple different frames, and wherein an adjustment of a position of at least a first light path adjustment element is based on a comparison of the relative focus of a plurality of associated sections from different frames.

7. A method in accordance with claim 6, wherein the comparison is made relative to an average of the relative focus determined for the associated sections from a predefined number of earlier frames in the sequence of frames.

8. A method in accordance with claim 1, wherein an initial starting position of at least the first light path adjustment element is determined based upon a comparison of the relative focus of the plurality of sections of a common frame.

9. A method in accordance with claim 8, wherein the initial starting position of at least the first light path adjustment element, corresponds to a focal distance, which is a more proximal one of two predetermined focal distances relative to the image capture unit, when the relative focus of the plurality of sections of a common frame, are less than a predetermined difference.

10. A method in accordance with claim 8, wherein the initial starting position of at least the first light path adjustment element, corresponds to a focal distance, which is a more distal one of two predetermined focal distances relative to the image capture unit, when the relative focus of the plurality of sections of a common frame, are greater than a predetermined difference.

11. A method in accordance with claim 1, further comprising determining the color content of one or more sections, wherein an initial starting position of at least the first light path adjustment element is based upon the determined color content of the one or more sections.

12. A method in accordance with claim 11, wherein the determined color content includes a determination of an amount of each primary color of light.

13. A method in accordance with claim 12, wherein the primary colors include red, green and blue.

14. A method in accordance with claim 12, wherein the primary colors include magenta, cyan and yellow.

15. A method in accordance with claim 12, wherein the initial starting position of at least the first light path adjustment element, corresponds to a focal distance, which is a more proximal one of two predetermined focal distances relative to the image capture unit, when a ratio of the amount of color of a first primary color relative to the amount of color of a second primary color different from the first primary color selected from a plurality of primary colors for each of two or more distinct pairings of different primary colors has a value, which is approximately equivalent to 1.

16. A method in accordance with claim 12, wherein the initial starting position of at least the first light path adjustment element, corresponds to a focal distance, which is a more distal one of two predetermined focal distances relative to the image capture unit, when a ratio of the amount of color of a first primary color relative to the amount of color of a second primary color different from the first primary color selected from a plurality of primary colors for at least one of two or more distinct pairings of different primary colors does not have a value, which is approximately equivalent to 1.

17. A method in accordance with claim 1, wherein the at least first light path adjustment element includes one or more elements selected from a group comprising lenses and reflectors.

18. A method in accordance with claim 1, wherein the image capture unit is incorporated as part of a wireless communication device.

19. A method in an image capture unit having at least a first light path adjustment element for determining an initial starting position of at least the first light path adjustment element, in conjunction with automatically focusing an image received by the image capture unit relative to a target, the method comprising:

capturing an image by the image capture unit;

dividing a captured image into a plurality of sections;

determining a relative focus for alternate sections of the captured image;

comparing the relative focus for the alternate sections of the captured images; and

if the relative focus for the alternate sections are within a predetermined tolerance, then the initial starting position of at least the first light path adjustment element, corresponds to a focal distance, which is a more proximal one of two predetermined focal distances relative to the image capture unit, otherwise

if the relative focus for the alternate sections are not within a predetermined tolerance, then the initial starting position of at least the first light path adjustment element corresponds to a focal distance, which is a more distal one of the two predetermined focal distances relative to the image capture unit.

20. A method in an image capture unit having at least a first light path adjustment element for determining an initial starting position of at least the first light path adjustment element, in conjunction with automatically focusing an image received by the image capture unit relative to a target, the method comprising:

capturing an image by the image capture unit;

determining a color content of the captured image;

if the image includes monochromatic content, then the initial starting position of at least the first light path adjustment element, corresponds to a focal distance, which is a more proximal one of two predetermined focal distances relative to the image capture unit, otherwise

if the image includes non-monochromatic content, then the initial starting position of at least the first light path adjustment element corresponds to a focal distance, which is a more distal one of the two predetermined focal distances relative to the image capture unit.