Image sensor having an extended dynamic range upper limit

• US 9,591,247 B2
• Filed: 12/22/2014
• Issued: 03/07/2017
• Est. Priority Date: 12/22/2014
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Wan, Chung Chun
• Primary Examiner(s): Henn, Timothy J
• Application Number:
  US14/579,940
• Publication Number:
  US 20160182847A1
• Time in Patent Office: 806 Days
• US Class Current: 1/1
• CPC Class Codes: G01J 1/46 using a capacitor
• CPC Class Codes: G01J 2001/446 Photodiode
• CPC Class Codes: G01S 17/36 with phase comparison between the received signal and the contemporaneously transmitted signal
• CPC Class Codes: G01S 17/894 3D imaging with simultaneous measurement of time-of-flight at a 2D array of receiver pixels, e.g. time-of-flight cameras or flash lidar
• CPC Class Codes: G01S 7/4914 of detector arrays, e.g. charge-transfer gates
• CPC Class Codes: G01S 7/4915 Time delay measurement, e.g. operational details for pixel components signal extraction and conditioning G01S7/493; Phase measurement
• CPC Class Codes: H04N 13/271 wherein the generated image signals comprise depth maps or disparity maps
• CPC Class Codes: H04N 23/56 provided with illuminating means
• 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 25/134 based on three different wavelength filter elements
• CPC Class Codes: H04N 25/53 Control of the integration time
• CPC Class Codes: H04N 25/575 with a response composed of multiple slopes
• CPC Class Codes: H04N 25/587 acquired sequentially, e.g. using the combination of odd and even image fields
• CPC Class Codes: H04N 25/705 Pixels for depth measurement, e.g. RGBZ
• CPC Class Codes: H04N 25/745 Circuitry for generating timing or clock signals
• CPC Class Codes: H04N 25/75 Circuitry for providing, modifying or processing image signals from the pixel array

Abstract

An apparatus is described that includes an image sensor having timing and control circuitry and threshold circuitry. The timing and control circuitry is to generate signals to cause multiple transfers of charge from a photo-diode to a storage capacitor within a pixel cell during an image capture sequence. The threshold circuitry is to track the storage capacitor'"'"'s voltage over the course of the multiple transfers and recognize when the storage capacitor'"'"'s voltage reaches a threshold.

Claims

1. An apparatus, comprising:

an image sensor comprising;

timing and control circuitry to generate signals to cause multiple transfers of charge from a photo-diode to a storage capacitor within a pixel cell during an image capture sequence;

threshold circuitry to track said storage capacitor'"'"'s voltage over the course of said multiple transfers and recognize when said storage capacitor'"'"'s voltage reaches a threshold, wherein said threshold circuitry is coupled to said timing and control circuitry, said timing and control circuitry to cease additional transfers of charge within an image capture sequence in response to said threshold circuitry'"'"'s recognition that said storage capacitor'"'"'s voltage has reached a threshold;

circuitry to perform one of the following;

a time-of-flight calculation that accounts for said storage capacitor'"'"'s voltage reaching said threshold;

extrapolate an optical intensity received by said photo-diode based on when said storage capacitor'"'"'s voltage reached said threshold.

2. The apparatus of claim 1 wherein said timing and control circuitry is coupled to a transfer gate of said pixel cell and controls said transfers of charge through said transfer gate.

3. The apparatus of claim 1 wherein said pixel cell is a visible light pixel cell.

4. The apparatus of claim 1 wherein said pixel cell is a time-of-flight pixel cell.

5. The apparatus of claim 1 wherein said pixel cell includes both visible light and time-of-flight pixel circuitry.

6. A method, comprising:

performing the following by an image sensor;

generating signals to cause multiple transfers of charge from a photo-diode to a storage capacitor within a pixel cell during an image capture sequence;

tracking said storage capacitor'"'"'s voltage over the course of said multiple transfers and recognizing when said storage capacitor'"'"'s voltage reaches a threshold;

performing one of i) and ii) below;

i) calculating a time-of-flight value that accounts for said storage capacitor'"'"'s voltage reaching said threshold;

ii) extrapolating an optical intensity received by said photo-diode based on when said storage capacitor'"'"'s voltage reached said threshold;

ceasing additional transfers of charge within an image capture sequence in response to said threshold circuitry'"'"'s recognition that said storage capacitor'"'"'s voltage has reached a threshold.

7. The method of claim 6 wherein said pixel cell is a visible light pixel cell.

8. The method of claim 6 wherein said pixel cell is a time-of-flight pixel cell.

9. The method of claim 6 wherein said pixel cell includes both visible light and time-of-flight pixel circuitry.

10. A computing system, comprising:

an applications processor having a plurality of processing cores and a memory controller;

a camera system coupled to said applications processor, said camera system having an image sensor comprising;

timing and control circuitry to generate signals to cause multiple transfers of charge from a photo-diode to a storage capacitor within a pixel cell during an image capture sequence;

threshold circuitry to track said storage capacitor'"'"'s voltage over the course of said multiple transfers and recognize when said storage capacitor'"'"'s voltage reaches a threshold, wherein said threshold circuitry is coupled to said timing and control circuitry, said timing and control circuitry to cease additional transfers of charge within an image capture sequence in response to said threshold circuitry'"'"'s recognition that said storage capacitor'"'"'s voltage has reached a threshold;

circuitry to perform one of the following;

a time-of-flight calculation that accounts for said storage capacitor'"'"'s voltage reaching said threshold;

extrapolate an optical intensity received by said photo-diode based on when said storage capacitor'"'"'s voltage reached said threshold.

11. The computing system of claim 10 wherein said timing and control circuitry is coupled to a transfer gate of said pixel cell and controls said transfers of charge through said transfer gate.

12. The computing system of claim 10 wherein said pixel cell is a visible light pixel cell.

13. The computing system of claim 10 wherein said pixel cell is a time-of-flight pixel cell.

14. The computing system of claim 10 wherein said pixel cell includes both visible light and time-of-flight pixel circuitry.