SYSTEM AND METHOD FOR FOCUSING A DIGITAL CAMERA

• US 20100002126A1
• Filed: 08/25/2009
• Published: 01/07/2010
• Est. Priority Date: 11/16/2004
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Inventors: WENSTRAND, JOHN S., Baer, Richard L., Johnson, Patricia E.
• Granted Patent: US 7,990,460 B2
• Time in Patent Office: Days
• US Class Current: 348/345
• CPC Class Codes: G02B 13/001 Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras G02B23/243 takes precedence
• CPC Class Codes: G02B 27/62 Optical apparatus specially adapted for adjusting optical elements during the assembly of optical systems
• CPC Class Codes: G02B 7/005 Motorised alignment
• CPC Class Codes: G02B 7/08 adapted to co-operate with a remote control mechanism
• CPC Class Codes: H04N 17/002 for television cameras
• CPC Class Codes: H04N 23/54 Mounting of pick-up tubes, electronic image sensors, deviation or focusing coils
• CPC Class Codes: H04N 23/57 Mechanical or electrical details of cameras or camera modules specially adapted for being embedded in other devices
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method

Abstract

A method of focusing a digital camera module with an image sensor including capturing an image of a test target with the digital camera module, determining a focus quality of the image with the image sensor, outputting a signal related to the focus quality of the image from the digital camera module to a focusing station external to the digital camera module, and determining whether a position of a lens from the image sensor within the digital camera module should be altered to improve a focus quality of subsequently captured images.

Claims

1. A method of focusing a digital camera module with an image sensor, the method comprising:

capturing images of a test target with the digital camera module;

determining a focus quality of each of the respective images with the image sensor;

generating, from the digital camera module, a binary output signal, indicative of whether the focus quality is increasing as subsequent images are captured;

sending the binary output signal to a focusing station external to the digital camera module; and

changing, by the focusing station, a position of a lens from the image sensor within the digital camera module to adjust the focus quality of the subsequently captured images in accordance with the binary output signal.

2. A method according to claim 1, wherein the determining of the focus quality of each of the respective images includes determining a variance of a spatial first derivative of each of the respective images.

3. A method according to claim 2, wherein the determining of the variance of the spatial first derivative of each of the respective images includes determining the spatial first derivative of each of the respective images.

4. A method according to claim 2, wherein the variance of the spatial first derivative of a respective image is determined by analyzing only one or more regions of interest of the respective image, and wherein the one or more regions of interest collectively define less than 50% of an entirety of the respective image.

5. A method according to claim 4, wherein the respective image is a second image captured after a first image, and wherein the binary output signal indicates that the focus quality of the second image is one of an improved focus quality, a decreased focus quality, or the same focus quality relative to the focus quality of the first image based on a comparison of the variance of the spatial first derivative of the second image with a variance of a spatial first derivative of the first image.

6. A method according to claim 1, wherein the changing of the position of the lens is repeated a plurality of times, wherein each time includes moving the lens in an increment equal to a preset distance.

7. A method according to claim 6, wherein the repeated changing of the position of the lens includes positioning the lens relative to the image sensor to optimize the focus quality.

8. A method according to claim 7, wherein the changing of the position of the lens includes determining a direction the lens is to be adjusted to improve the focus quality.

9. A digital camera module for capturing images depicting a test target, the digital camera module including:

an image sensor for operating in a focus mode in which the image sensor determines a focus quality of each of the captured images and to generate a binary output signal, indicative of whether the focus quality is increasing as subsequent images are captured, sent to a focusing station external to the digital camera module; and

a lens spaced from the image sensor, wherein a distance the lens is spaced from the image sensor is adjustable, by the focusing station, based on the binary output signal.

10. A digital camera module according to claim 9, wherein the image sensor determines the focus quality of each image by determining a variance of the image.

11. A digital camera module according to claim 10, wherein the image sensor determines the variance of each image based on one or more regions of interest of the image, wherein the one or more regions of interest collectively form less than 95% of the image.

12. A digital camera module according to claim 11, wherein the one or more regions of interest are selected based on a position of test objects on the test target.

13. A digital camera module according to claim 9, wherein the digital camera module is a fixed-focus camera module.

14. A focusing station for fixing the focus of a digital camera module, the focusing station including:

an actuating assembly for interfacing with a barrel of a digital camera module;

a microcontroller for receiving a binary output signal from the digital camera module indicative of whether focus quality is increasing as subsequent images are captured by the digital camera module and for determining which direction to rotate the barrel to improve the focus quality of the subsequent images based on the binary output signal received from the digital camera module.

15. A focusing station according to claim 14, wherein the binary output signal indicates whether the focus quality of the respective image has improved since a previous rotation of the barrel.

16. A focusing station according to claim 14, wherein the microcontroller is not configured to receive video input from the digital camera module.

17. A focusing station according to claim 14, including:

a test target including a background and a plurality of discrete solid color objects, each of the discrete solid color objects being of a color contrasting with the background; and

wherein the focusing station receives the digital camera module in a position to capture the images of the test target.

18. A method of determining focus quality of a camera module, the method including:

providing a test target including a background and at least one object on the background, wherein the background and the at least one object have contrasting colors;

capturing images of the test target with the camera module having a lens barrel;

analyzing, in the camera module, regions of interest within each of the images to determine the focus quality of the camera module, wherein the regions of interest depict portions of the background and portions of the at least one object and the regions of interest for each image are collectively less than an entire captured image

outputting, by the camera module to a test station, a binary output signal indicative of whether the focus quality is increasing as subsequent images are captured by the camera module; and

determining, by the test station, which direction to rotate the lens barrel to improve the focus quality of the subsequent images based on the binary output signal received from the camera module.

19. A method according to claim 18, wherein the analyzing of the regions of interest includes determining a variance of each of the regions of interest.

20. A method according to claim 18, wherein the at least one object is a plurality of objects, and each of the regions of interest depicts a portion of the background and a portion of a different one of the objects.

21. A method according to claim 18, including:

programming an image sensor of the camera module with knowledge of positions of the regions of interest prior to capturing the images of the test target,

wherein the image sensor analyzes the regions of interest based on the programmed knowledge.