METHOD AND APPARATUS WITH FAST CAMERA AUTO FOCUS

• US 20090167930A1
• Filed: 12/27/2007
• Published: 07/02/2009
• Est. Priority Date: 12/27/2007
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: ATI Technologies ULC (Advanced Micro Devices, Inc.)
• Inventors: Aleksic, Milivoje, Safaee-Rad, Reza
• Granted Patent: US 8,724,013 B2
• Time in Patent Office: Days
• US Class Current: 348/347
• CPC Class Codes: G02B 7/38 measured at different points on the optical axis , e.g. focussing on two or more planes and comparing image data
• 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 apparatus improves an auto focus system by altering, such as by positioning, at least one lens of a digital camera to a plurality of predetermined nonuniform lens positions corresponding to predetermined nonuniform lens position data. The method and apparatus selects a final lens position for the lens based on the predetermined nonuniform lens position data. In one example, a fixed number of predetermined nonuniform lens positions define a set of lens positions used to capture images during an auto focus operation. A final image is captured using a final lens position. The final lens position is determined by comparing focus metric information from each of the frames obtained at the various predetermined nonuniform focus lens positions and selecting the frame with, for example, the best focus metric as the lens position to be used for the final picture or image capture.

Claims

1. A method for improving an auto-focus system, comprising:

as part of an autofocus operation, altering at least one lens of a digital camera to at least one of a plurality of predetermined nonuniform lens positions corresponding to predetermined nonuniform lens position data; and

selecting a final lens position for the lens based on the predetermined nonuniform lens position data.

2. The method of claim 1 comprising obtaining the predetermined nonuniform lens position data from memory.

3. The method of claim 1 wherein the predetermined nonuniform lens position data is received from a passive component matrix.

4. The method of claim 1 wherein selecting the final lens position comprises:

selecting a preliminary predetermined nonuniform lens position based on the predetermined nonuniform lens positions;

capturing an image and determining focus metric information of the image corresponding to the preliminary lens position and storing the focus metric information as preliminary optimal focus metric information;

determining a next lens position based on the predetermined nonuniform lens positions;

capturing a next image and determining next focus metric information of the next image at the next lens position; and

comparing the preliminary optimal focus metric information and the next focus metric information and retaining preferred metric information as new preliminary optimal focus metric information.

5. The method of claim 4, wherein the next lens position is determined by moving the lens in a determined search direction from the preliminary optimal lens position.

6. The method of claim 1, wherein the predetermined nonuniform lens position data is based on optical characteristics of a fixed focal length lens and comprises data representing at least eight lens positions including a hyper-focal length lens position which has the largest depth of field. lens position

7. A circuit for improving an auto-focus system, comprising:

auto focus control logic operative to alter a lens to a plurality of predetermined nonuniform lens positions corresponding to predetermined nonuniform lens position data; and

operative to select a final lens position based on the predetermined nonuniform lens position data.

8. The circuit of claim 7 comprising memory containing the predetermined nonuniform lens position data wherein the memory is comprised of data representing a lookup table that comprises predetermined nonuniform lens positions based on a characteristic curve of the lens.

9. The circuit of claim 7 comprising:

focus metric logic operative to determine image focus metric information based on captured image pixel information;

memory operative to store the focus metric information; and

comparator logic operative to compare existing focus metric information stored in memory with new focus metric information.

10. The circuit of claim 7, wherein the auto focus circuit is operative to capture as a final image, an image at the final lens position lens position and wherein the predetermined nonuniform lens position data is based on optical characteristics of a fixed focal length lens and comprises data representing at least eight lens positions including a hyper-focal length lens position which has the largest depth of field.

11. An apparatus comprising:

a camera having a focusable lens;

memory containing predetermined nonuniform lens position data;

auto focus control logic operative to configure the lens to predetermined nonuniform lens positions corresponding to the predetermined nonuniform lens position data and to select a final lens position based on the predetermined nonuniform lens position data; and

a user interface circuit operative to activate the auto-focus circuit.

12. The apparatus of claim 11, wherein the apparatus is a handheld device.

13. The apparatus of claim 11, wherein the memory comprises data representing a lookup table that comprises predetermined nonuniform lens positions based on a characteristic curve of the lens.

14. The apparatus of claim 11, wherein the auto focus control logic comprises:

focus metric statistical logic operative to determine image focus metric information based on captured image pixel information;

memory operative to store the focus metric information; and

comparator logic operative to compare existing focus metric statistical information stored in memory with new focus metric information.

15. The apparatus of claim 11 further comprising logic operative to control the lens to capture a set of images using a plurality of lens positions based on at least one of uniform lens position data or predetermined nonuniform lens position data;

and

depth map generation logic operative to determine focus metric information for each region of interest in each image of the set and determine an optimal lens position for each of the regions of interest, based on the focus metric information and generate a depth map based on the focus metric information.

16. The apparatus of claim 15 comprising logic operative to perform an image generation operation based on the generated depth map.

17. The apparatus of claim 16 comprising a compressor operative to compress frame information of a final frame and wherein the apparatus is operative to transmit the compressed frame information and corresponding depth map to a remote device.

18. The apparatus of claim 15 wherein the depth map generation logic is operative to:

determine focus metric information for each of a plurality of regions of interest in each image of the set;

determine an optimal lens position for each of the regions of interest, based on the focus metric information from the images in the set;

and wherein the apparatus comprises logic operative to perform an image generation operation based on the generated depth map.