Circuit and method providing wide dynamic-range operation of auto-focus(AF) focus state sensor elements, digital imaging device, and computer system including same

• US 9,392,160 B2
• Filed: 06/20/2014
• Issued: 07/12/2016
• Est. Priority Date: 06/20/2014
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Sfaradi, Roee, Eisenberg, Amit
• Primary Examiner(s): Henn, Timothy J
• Application Number:
  US14/310,369
• Publication Number:
  US 20150373250A1
• Time in Patent Office: 753 Days
• US Class Current: 1/1
• CPC Class Codes: G03B 13/36 Autofocus systems
• CPC Class Codes: H04N 23/672 based on the phase difference signals
• CPC Class Codes: H04N 23/741 by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors
• CPC Class Codes: H04N 25/134 based on three different wavelength filter elements
• CPC Class Codes: H04N 25/583 with different integration times
• CPC Class Codes: H04N 25/589 with different integration times, e.g. short and long exposures
• CPC Class Codes: H04N 25/704 Pixels specially adapted for focusing, e.g. phase difference pixel sets
• CPC Class Codes: H04N 25/778 comprising amplifiers shared between a plurality of pixels, i.e. at least one part of the amplifier must be on the sensor array itself

Abstract

A method and apparatus performing scene-adaptive auto-focusing for image capture with a variable-focus lens. The array of color pixels includes a array of half-covered light sensors to obtain lens-focus state information. The exposure time of the plurality of partially-covered light sensors is dynamically selected as long-exposure or short-exposure, based upon a current measurement of a property (e.g., brightness, or color-specific brightness) of a selected region of interest within a scene to be captured by the array. Then, focus state information corresponding to the selected region of interest is obtained by capturing light from the selected region of interest with first and second partially-covered light sensors. The exposure time of the partially-covered light sensors can be changed based on whether the brightness is greater than a predetermined threshold value.

Claims

1. A method of adaptive auto-focusing of an image capture device, having a lens and an array of light sensors including plurality of pixels and a plurality of focus state detecting elements (FDels) to obtain lens focus state information, the method comprising:

selecting one of a first and second modes of the image capture device based on a measurement of a currently-detected property of a selected region of interest within a scene to be captured by the array of light sensors, wherein in the first mode the FDels in the array of light sensors are exposed for a loner exposure time than the plurality of pixels, wherein in the second mode the FDels in the array of light sensors are exposed for a shorter exposure time than the plurality of pixels; and

obtaining lens focus state information corresponding to the selected region of interest by capturing light from the selected region of interest in a first and second FDels among the plurality of FDels, operated with the selected mode.

2. The method of claim 1, wherein setting the exposure time of first and second FDels, includes:

changing the mode from a default first mode to the second mode if the measurement of the currently-detected property is greater than a predetermined threshold value; and

leaving the selected mode at the default first mode if the currently-detected property is less than the predetermined threshold value.

3. The method of claim 1, further comprising:

performing an AutoFocus algorithm for focusing the lens of the image capture device upon the selected region of interest based upon obtained lens focus state information corresponding to the selected region of interest.

4. The method of claim 2, further comprising focusing the lens of the image capture device upon the selected region of interest based upon obtained lens focus state information corresponding to a defocus of the selected region of interest.

5. The method of claim 1, wherein the currently-detected property of a selected region of interest within the scene is an average brightness of the selected region of interest.

6. The method of claim 5, wherein the currently-detected property of the selected region of interest within the scene is a brightness of the selected region of interest as detected by at least one of the first and second FDels.

7. The method of claim 5, wherein the currently-detected property of the selected region of interest within the scene is a brightness of the selected region of interest as detected by at least one of a R, G or B color-filtered light sensor among the array of light sensors.

8. An imaging apparatus comprising:

an image sensor including a light sensor array including a first plurality of picture elements (pixels) and a plurality of focus state detecting elements (FDels), wherein each of the pixels and each of the FDels includes a photodiode;

a lens configured to focus light from a scene onto the light sensor array for capturing a frame;

a lens-focus controller configured to control a focus state of the lens relative to the light sensor array and relative to a first region of the scene based on a lens-control signal;

a scene-condition calculator for calculating a selected condition of a first selected portion of the frame captured from the first region of the scene; and

a mode selector for selecting one of a first and second modes of the image sensor based on a scene-condition calculation,

wherein in the first mode the FDels in the light sensor array are exposed for a longer exposure time than the first plurality of pixels, and

wherein in the second mode the FDels in the light sensor array are exposed for a shorter exposure time than the first plurality of pixels.

9. The apparatus of claim 8, further including a second plurality of picture elements (pixels).

10. The apparatus of claim 9, wherein during the first mode the FDels and the second plurality of pixels are exposed for a longer exposure time than the first plurality of pixels.

11. The apparatus of claim 9, wherein each of the first plurality of pixels and the second plurality of pixels include color-filtered pixels.

12. A computing system comprising:

a central processing unit (CPU) configured to control an imaging apparatus, wherein the imaging apparatus includes;

an image sensor including a light sensor array including a first plurality of picture elements (pixels) and a plurality of Focus state Detecting elements (FDels), wherein each of the pixels and each of the FDels includes a photodiode;

a lens configured to focus light from a scene onto the light sensor array for capturing a frame; and

a lens-focus controller configured to control a focus state of the lens relative to the light sensor array and relative to a first region of the scene based on a lens-control signal;

a scene-condition calculator for calculating a selected condition of a first selected portion of the frame captured from the first region of the scene;

a mode selector for selecting one of a first and second modes of the image sensor based on a scene-condition calculation, wherein in the first mode the FDels in the light sensor array are exposed for a longer exposure time than the first plurality of pixels, and wherein in the second mode the FDels in the light sensor array are exposed for a shorter exposure time than the first plurality of pixels.

13. The computing system of claim 12, wherein the CPU is configured to receive image data from the imaging apparatus.

14. The apparatus of claim 13, wherein a selected scene-condition is brightness, wherein the scene-condition calculator includes an exposure calculator for calculating the brightness of the first selected portion of the frame;

and wherein the mode selector selects one of the first and second modes of the image sensor based on a calculated brightness, wherein if the calculated brightness is greater than a predetermined brightness threshold, the mode selector selects the second mode.

15. The apparatus of claim 12, further including a second plurality of picture elements (pixels).

16. The apparatus of claim 15, wherein in the first mode the FDels and the second plurality of pixels are exposed for a longer exposure time than the first plurality of pixels.

17. The apparatus of claim 15, wherein each of the first plurality of pixels and the second plurality of pixels includes color-filtered pixels.

18. The apparatus of claim 17, wherein the first plurality of pixels and the second plurality of pixels and the FDels within one pair of vertically adjacent rows of the light sensor array are controlled with a 2-shared pixel wiring patter.

19. The apparatus of claim 12, wherein the FDels are read out resulting in a focus state image.

20. The apparatus of claim 12, wherein in the first mode after the first plurality of pixels have been exposed to light from the scene for a first exposure time and read out, then the FDels are read out resulting in a focus state image of a second exposure time longer than the first exposure time.