Image sensor with symmetric multi-pixel phase-difference detectors, and associated methods

Patent metadata

Field	Value
Publication number	US-9807294-B2
Application number	US-201514819021-A
Country	US
Kind code	B2
Filing date	Aug 5, 2015
Priority date	Aug 5, 2015
Publication date	Oct 31, 2017
Grant date	Oct 31, 2017

Abstract

An imaging system with on-chip phase-detection includes an image sensor with symmetric multi-pixel phase-difference detectors. Each symmetric multi-pixel phase-difference detector includes (a) a plurality of pixels forming an array and each having a respective color filter thereon, each color filter having a transmission spectrum and (b) a microlens at least partially above each of the plurality of pixels and having an optical axis intersecting the array. The array, by virtue of each transmission spectrum, has reflection symmetry with respect to both (a) a first plane that includes the optical axis and (b) a second plane that is orthogonal to the first plane. The imaging system includes a phase-detection row pair, which includes a plurality of symmetric multi-pixel phase-difference detectors in a pair of adjacent pixel rows and a pair, and an analogous phase-detection column pair.

First claim

What is claimed is:

1. An image sensor with symmetric multi-pixel phase-difference detectors, each symmetric multi-pixel phase-difference detector comprising:
four pixels forming a 2×2 array and each having a respective color filter thereon, each color filter having a respective transmission spectrum; and
a microlens at least partially above each of the four pixels and having an optical axis intersecting the 2×2 array,
the 2×2 array, by virtue of the respective transmission spectra, having reflection symmetry with respect to at least one of (a) a first plane that includes the optical axis and (b) a second plane that is orthogonal to the first plane and is parallel to the optical axis.

2. The image sensor of claim 1 , the 2×2 array being a planar array.

3. The image sensor of claim 1 , the optical axis intersecting the 2×2 array at a 90-degree angle.

4. The image sensor of claim 1 , further comprising:
a phase-detection row pair that includes a plurality of the symmetric multi-pixel phase-difference detectors in a pair of adjacent pixel rows; and
a phase-detection column pair that includes a plurality of the symmetric multi-pixel phase-difference detectors in a pair of adjacent pixel columns.

5. The image sensor of claim 1 , the 2×2 array, by virtue of the respective transmission spectra having reflection symmetry with respect to both (a) a first plane that includes the optical axis and (b) a second plane that is orthogonal to the first plane.

6. The image sensor of claim 1 , the color filters on two of the four pixels each having a first transmission spectrum, the color filters on the remaining two of the of four pixels each having a second transmission spectrum.

7. The image sensor of claim 6 , the first transmission spectrum and the second transmission spectrum each corresponding to the transmission spectrum of one of a red color filter, a blue color filter, a green color filter, a cyan color filter, a magenta color filter, a yellow color filter, and a panchromatic color filter.

8. An imaging system with on-chip phase-detection, comprising:
a phase-detection row pair, for measuring a pair of horizontal line profiles for light incident from left and right directions, that includes a plurality of symmetric multi-pixel phase-difference detectors in a pair of adjacent pixel rows;
a phase-detection column pair, for measuring a pair of vertical line profiles for light incident from top and bottom directions, respectively, that includes a plurality of symmetric multi-pixel phase-difference detectors in a pair of adjacent pixel columns; and
a phase-processing module for processing the pair of horizontal line profiles and the pair of vertical line profiles to measure phase shift associated with an arbitrarily-oriented and arbitrarily-located edge in the scene,
each symmetric multi-pixel phase-difference detector including (i) four pixels forming a 2×2 array and each having a respective color filter thereon, each color filter having a respective transmission spectrum, and (ii) a microlens at least partially above each of the four pixels and having an optical axis intersecting the 2×2 array, the 2×2 array, by virtue of the respective transmission spectra, having reflection symmetry with respect to at least one of (a) a first plane that includes the optical axis and (b) a second plane that is orthogonal to the first plane and is parallel to the optical axis.

9. The imaging system of claim 8 , further comprising an autofocus module for adjusting focus of an imaging objective to reduce the phase shift.

10. A method for phase detection using an image sensor with symmetric multi-pixel phase-difference detectors, the method comprising:
generating a first line profile from an object edge imaged on a first pixel subset in each of a plurality of mutually collinear symmetric multi-pixel phase-difference detectors of the image sensor;
generating a second line profile from the object edge imaged on a second pixel subset in each of the plurality of mutually collinear symmetric multi-pixel phase-difference detectors; and
determining a first phase shift from a spatial separation between the first line profile and the second line profile,
each symmetric multi-pixel phase-difference detector including (i) four pixels forming a 2×2 array and each having a respective color filter thereon, each color filter having a respective transmission spectrum, (ii) a microlens at least partially above each of the four pixels and having an optical axis intersecting the 2×2 array, the 2×2 array, by virtue of the respective transmission spectra, having reflection symmetry with respect to at least one of (a) a first plane that includes the optical axis and (b) a second plane that is orthogonal to the first plane and is parallel to the optical axis.

11. The method of claim 10 ,
the step of generating the first line profile comprising summing pixel responses of pixels of the first pixel subset; and
the step of generating the second line profile comprising summing pixel responses of pixels of the second pixel subset.

12. The method of claim 10 , the step of summing pixel responses of pixels of the first pixel subset comprising summing pixel responses of a pair of two adjacent pixels of the first pixel subset; and the step of summing pixel responses of pixels of the second pixel subset comprising summing pixel responses of a pair of two adjacent pixels of the second pixel subset not included in the first pixel subset.

13. The method of claim 10 , the symmetric multi-pixel phase-difference detectors being mutually collinear in a first direction parallel to one of (i) pixel rows of the image sensor and (ii) pixel columns of the image sensor.

14. The method of claim 13 , further comprising:
generating a third line profile from an object edge imaged on a first pixel subset in each of a second plurality of symmetric multi-pixel phase-difference detectors of the image sensor that are mutually collinear in a second direction that is perpendicular to the first direction;
generating a fourth line profile from the object edge imaged on a second pixel subset in each of the second plurality of mutually collinear symmetric multi-pixel phase-difference detectors; and
determining a second phase shift from a spatial separation between the first line profile and the second line profile.

15. The method of claim 10 , further comprising imaging the object edge onto the image sensor with an imaging objective.

16. The method of claim 15 , further comprising reducing the first phase shift by changing a distance between the imaging objective and the image sensor.

Assignees

• Omnivision Tech Inc

Inventors

• Liu Guansong
• Shan Jizhang
• Pang Chin Poh
• Yang Xiaodong

Classifications

• H04N25/134

  based on three different wavelength filter elements · CPC title

• H04N23/672 Primary

  based on the phase difference signals · CPC title

• H04N9/045

  Electricity · mapped topic

• G03B13/36

  Autofocus systems · CPC title

• G02B5/201 Primary

  in the form of arrays · CPC title