Systems and methods for detecting light-emitting diode without flickering

Patent metadata

Field	Value
Publication number	US-10044960-B2
Application number	US-201615164276-A
Country	US
Kind code	B2
Filing date	May 25, 2016
Priority date	May 25, 2016
Publication date	Aug 7, 2018
Grant date	Aug 7, 2018

Abstract

An image sensor for detecting light-emitting diode (LED) without flickering includes a pixel array with pixels. Each pixel including subpixels including a first and a second subpixel, dual floating diffusion (DFD) transistor, and a capacitor coupled to the DFD transistor. First subpixel includes a first photosensitive element to acquire a first image charge, and a first transfer gate transistor to selectively transfer the first image charge from the first photosensitive element to a first floating diffusion (FD) node. Second subpixel includes a second photosensitive element to acquire a second image charge, and a second transfer gate transistor to selectively transfer the second image charge from the second photosensitive element to a second FD node. DFD transistor coupled to the first and the second FD nodes. Other embodiments are also described.

First claim

What is claimed is:

1. An image sensor to detect a high illumination element without flickering, comprising:
a pixel array including a plurality of pixels, each of the pixels including:
(i) a plurality of subpixels including a first, a second, and third, and a fourth subpixel,
the first subpixel including a first photosensitive element to acquire a first image charge, a first transfer gate transistor to selectively transfer the first image charge from the first photosensitive element to a first floating diffusion (FD) node, and a first anti-blooming (AB) gate coupled to the first photosensitive element,
the second subpixel including a second photosensitive element to acquire a second image charge, a second transfer gate transistor to selectively transfer the second image charge from the second photosensitive element to a second FD node, and a second AB gate coupled to the second photosensitive element,
the third subpixel including a third photosensitive element to acquire a third image charge, a third transfer gate transistor to selectively transfer the third image charge from the third photosensitive element to a third FD node, and a third AB gate coupled to the third photosensitive element, and
the fourth subpixel including a fourth photosensitive element to acquire a fourth image charge, a fourth transfer gate transistor to selectively transfer the fourth image charge from the fourth photosensitive element to a fourth FD node, and a fourth AB gate coupled to the fourth photosensitive element,

(ii) a dual floating diffusion (DFD) transistor coupled to the first, the second, the third, and the fourth FD nodes, wherein the DFD transistor is selectively coupled to the first, the second, the third, and the fourth AB gates via the first, the second, the third, and the fourth transfer gate transistors, and
(iii) a capacitor coupled to the DFD transistor,

wherein the first AB gate is biased to leak less than the first transfer gate transistor, wherein the second, third, and fourth AB gates are biased to leak more than the second, third, and fourth transfer gate transistors, and
wherein during signal integration, the DFD transistor selectively couples to the first AB gate via the first transfer gate transistor and the capacitor stores a bloomed charge from the first photosensitive element.

2. The image sensor in claim 1 , wherein, at the end of integration, the bloomed charge stored on the capacitor is read out, and the first, second, third, and fourth image charges are subsequently readout as photosensitive element signals, respectively.

3. The image sensor in claim 1 , wherein the first photosensitive element includes one color filter from a Bayer color pattern and the second, third and fourth photosensitive elements includes a clear color filter.

4. The image sensor in claim 3 , wherein signals from first, the second, the third, and the fourth photosensitive elements are combined in image signal processing (ISP) to produce a final image charge.

5. An image sensor to detect a high illumination element without flickering, comprising:
a pixel array including a plurality of pixels, each of the pixels including:
(i) a plurality of subpixels including a first and a second subpixel,
the first subpixel including a first photosensitive element to acquire a first image charge, and a first transfer gate transistor to selectively transfer the first image charge from the first photosensitive element to a first floating diffusion (FD) node, and
the second subpixel including a second photosensitive element to acquire a second image charge, and a second transfer gate transistor to selectively transfer the second image charge from the second photosensitive element to a second FD node,

(ii) a dual floating diffusion (DFD) transistor coupled to the first and the second FD nodes, and
(iii) a capacitor coupled to the DFD transistor;

a source follower (SF) transistor coupled to the second FD node and the DFD transistor to output a charge from at least one of the first or the second FD nodes; and
a reset transistor coupled to a power rail and the second FD node,
wherein the first photosensitive element performs detection of the high illumination element, wherein the capacitor is coupled to the first transfer gate transistor to store excess first image charge, wherein the excess first image charge is image charge from the first photosensitive element that is leaking through the first transfer gate transistor,
wherein the second photosensitive element is larger than the first photosensitive element,
wherein the subpixels, the DFD transistor, the SF transistor and the reset transistor are disposed on a first semiconductor die, and the capacitor is disposed on a second semiconductor die, wherein the first and the second semiconductor dies are stacked to form a stacked image sensor.

6. The image sensor in claim 5 , wherein the plurality of subpixels further include a third and a fourth subpixel,
the third subpixel including a third photosensitive element to acquire a third image charge, and a third transfer gate transistor to selectively transfer the third image charge from the third photosensitive element to the second FD node, and
the fourth subpixel including a fourth photosensitive element to acquire a fourth image charge, and a fourth transfer gate transistor to selectively transfer the fourth image charge from the fourth photosensitive element to the second FD node.

7. The image sensor in claim 6 , wherein the first image charge stored on the first photosensitive element and the excess first image charge stored on the capacitor are read out, and the second, third, and fourth image charges are binned together and subsequently readout by Correlated Double Sampling (CDS).

8. The image sensor in claim 7 , wherein the image charges are readout three times, wherein
(i) the first image charge and the excess first image charge are readout,
(ii) the second, third, and fourth image charges that are binned together are then readout, and
(iii) the second, third, and fourth image charges that are binned together and the excess first image charge are then readout.

9. An image sensor to detect a high illumination element without flickering comprising:
a pixel array including a plurality of pixels, each of the pixels including:
a plurality of subpixels disposed on a first semiconductor die including a first subpixel, the first subpixel including a first photosensitive element to acquire a first image charge, and a first transfer gate transistor to selectively transfer the first image charge from the first photosensitive element to a first floating diffusion (FD) node,
a first dual floating diffusion (DFD) transistor coupled to the FD node, wherein the first DFD transistor is disposed on the first semiconductor die,
a first capacitor coupled to the first DFD transistor and a second DFD transistor, and
a second capacitor coupled to the second DFD transistor,
wherein the first capacitor, the second capacitor and the second DFD transistor are disposed on a second semiconductor die, wherein the first and the second semiconductor dies are stacked to form a stacked image sensor.

10. The image sensor of claim 9 , further comprising:
a source follower (SF) transistor coupled to the first FD node and the DFD transistor to output a charge from the first FD node; and
a reset transistor coupled to a power rail and the first FD node.

11. A method to detect a high illumination element without flickering comprising:
capturing by a pixel array including a plurality of pixels an image frame, each of the pixels including a dual floating diffusion (DFD) transistor, a capacitor coupled to the DFD transistor, and a

Assignees

• Omnivision Tech Inc

Inventors

• Mao Duli
• Willassen Trygve
• Solhusvik Johannes
• Mabuchi Keiji
• Chen Gang
• Manabe Sohei
• Tai Dyson H
• Phan Bill
• Cellek Oray Orkun
• Lin Zhiqiang
• Ma Siguang
• Yang Dajiang
• Fowler Boyd Albert

Classifications

• H04N25/622

  by controlling anti-blooming drains · CPC title

• H04N25/778

  comprising amplifiers shared between a plurality of pixels, i.e. at least one part of the amplifier must be on the sensor array itself · CPC title

• H04N25/621

  for the control of blooming · CPC title

• H04N25/59

  by controlling the amount of charge storable in the pixel, e.g. modification of the charge conversion ratio of the floating node capacitance · CPC title

• H04N25/771

  comprising storage means other than floating diffusion · CPC title