Multiple image autofocus

• US 7,518,651 B2
• Filed: 05/28/2004
• Issued: 04/14/2009
• Est. Priority Date: 05/28/2004
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Inventors: Butterworth, Mark M.
• Primary Examiner(s): Ometz; David L
• Assistant Examiner(s): PRABHAKHER, PRITHAM DAVID
• Application Number:
  US10/857,050
• Publication Number:
  US 20050264678A1
• Time in Patent Office: 1,782 Days
• Field of Search: 348345-349, 396 77- 82, 359698-706
• US Class Current: 348/345
• CPC Class Codes: H04N 23/665 involving internal camera communication with the image sensor, e.g. synchronising or multiplexing SSIS control signals
• CPC Class Codes: H04N 23/676 Bracketing for image capture at varying focusing conditions

Abstract

A camera provides an autofocus function by capturing a series of images when a lens is at different positions, analyzing the images to identify a best-focused image, and outputting the best-focused image. Unselected images can be discarded. The camera can include a FIFO buffer that receives image data from an image sensor as the image sensor captures images. When a photographer activates a shutter button, an analysis system, which may be implemented in software, analyzes the images in the FIFO buffer and selects the best-focused image for output. In alternative embodiments, the movement of the lens and the capture of the images can be before or in response to activation of the shutter button.

Claims

1. A photography process using a lens drive system to change a position of a focus of a lens, comprising:

moving the focus of the lens in discrete steps to a series of positions relative to an image sensor;

capturing images respectively taken at the series of positions during an image-capture interval while synchronizing the capturing of the image with the moving of the focus of the lens such that the images are captured while the lens is stationary relative to the image sensor;

analyzing the captured images to identify a best-focused image; and

saving the best-focused image,

wherein the moving of the focus of the lens includes continuously rotating the lens drive system during the image-capture interval to cause the focus of the lens to move in discrete steps relative to the image sensor.

2. The process of claim 1, wherein the moving of the focus of the lens comprises moving the lens in response to activation of a shutter button.

3. The process of claim 1, wherein the moving of the focus of the lens comprises continuously operating a drive motor for a lens drive system on which the lens is mounted.

4. The process of claim 3, wherein the lens drive system moves the lens back and forth through a range of motion while the drive motor operates.

5. The process of claim 3, wherein the analyzing of the captured images is in response to activation of a shutter button.

6. The process of claim 3, wherein the capturing of the images comprises repeatedly capturing a new image and then storing image data in a FIFO buffer, wherein image data that is stored first in the FIFO buffer is discarded to make room for new image data when the FIFO buffer is full.

7. The process of claim 6, wherein the saving of the best-focused image comprises reading from the FIFO buffer image data corresponding to the best-focused image and storing image data corresponding to the best-focused image in a memory.

8. The process of claim 3, wherein the drive motor comprises a DC motor.

9. The process of claim 1, wherein:

the moving of the focus of the lens includes driving the lens using a motor, the motor being operated without stopping during the image-capture interval to cause the movement of the lens in discrete steps during the image-capture interval.

10. A camera comprising:

an image sensor for capturing a series of images during an image-capture interval;

a lens;

a lens drive system for moving a focus of the lens in discrete steps relative to the image sensor during the image-capture interval, the image sensor synchronizing the capturing of the images with the moving of the focus of the lens such that the images are captured while the lens is stationary relative to the image sensor; and

a selection system coupled to the image sensor to analyze image data from the image sensor, for selecting a best-focused image from among the series of images, and for outputting the best-focused image as an output photograph,

wherein the lens drive system includes a cam coupled to a motor for changing the focus of the lens relative to the image sensor, the cam being continuously rotated during the image-capture interval.

11. The camera of claim 10, further comprising a buffer connected to receive image data from the image sensor and connected to provide image data to the selection system for analysis and selection.

12. The camera of claim 11, wherein the buffer comprises a FIFO buffer.

13. The camera of claim 10, wherein the lens drive system comprises:

the motor;

the cam attached to be spun by the motor; and

a sliding lens barrel that rides on the cam.

14. The camera of claim 13, wherein the motor comprises a DC motor that is switched on to operate continuously while the image sensor captures the series of images.

15. The camera of claim 13, further comprising a switch that turns the motor on when the camera enters a ready mode and turns the motor off when the camera exits the ready mode.

16. The camera of claim 10, wherein the lens drive system comprises a mechanical system that responds to movement of a shutter button of the camera to move the lens.

17. The camera of claim 10, wherein the lens drive system comprises a lever that moves the lens as a shutter button of the camera is depressed.

18. The camera of claim 10, wherein the lens drive system includes:

the cam having a camming surface such that a displacement of the lens is controlled based on a rotation angle of the cam, wherein the camming surface includes a plurality of continuous regions such that each continuous region of the camming surface corresponds to a predetermined displacement of the lens, movement between each respective continuous region and a subsequent continuous region of the plurality of continuous regions cause a shift in the displacement of the lens relative to the image sensor.

19. A photography method, comprising:

moving a focus of a lens in a series of discrete steps to a series of positions relative to an image sensor;

capturing images, using the image sensor, while synchronizing the capturing of the image with the moving of the focus of the lens such that the images are captured while the lens is stationary relative to the image sensor, each respective captured image corresponding to a different position of the series of positions;

storing the captured images;

analyzing the stored images to identify a best-focused image; and

deleting the stored images except for the identified best-focused image

wherein the moving of the focus of the lens includes continuously rotating a lens drive system during an image-capture interval to cause the focus of the lens to move in the series of discrete steps relative to the image sensor.

20. The method of claim 19, wherein:

the storing of the captured images includes saving the captured images in a FIFO buffer; and

the deleting of the stored images except for the identified best-focused image includes;

outputting the best-focused image; and

removing the stored images from the FIFO buffer in first in first out sequence as further images are stored by the FIFO buffer.