Solid-state imaging device and camera system

• US 20110025871A1
• Filed: 06/21/2010
• Published: 02/03/2011
• Est. Priority Date: 07/30/2009
• Status: Active Grant

• Current Assignee: Sony Semiconductor Solutions Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Yoshioka, Daisuke
• Granted Patent: US 8,537,252 B2
• Time in Patent Office: Days
• US Class Current: 348/222.1
• CPC Class Codes: H04N 25/589 with different integration times, e.g. short and long exposures
• CPC Class Codes: H04N 25/63 applied to dark current
• CPC Class Codes: H04N 25/633 by using optical black pixels
• CPC Class Codes: H04N 25/68 applied to defects
• CPC Class Codes: H04N 25/76 Addressed sensors, e.g. MOS or CMOS sensors

Abstract

A solid-state imaging device includes: a pixel unit in which pixels that perform photoelectric conversion are arranged in an optical black region and a valid pixel region; a readout processing unit that applies, to a readout signal of the pixel unit, readout processing corresponding to a reference signal subjected to clamp processing; and a clamp processing unit that clamps, referring to a readout signal level in the optical black region, a reference signal in the valid pixel region with an acquired clamp value, which is a value with which the signal level is reduced to zero. The clamp processing unit acquires, when information concerning readout is changed, a clamp value predicted from the clamp value before the change and a ratio of charge accumulation times before and after the change, and the readout processing unit performs first signal readout processing after the change with a reference signal clamped by the predicted clamp value.

Claims

1. A solid-state imaging device comprising:

a pixel unit in which pixels that perform photoelectric conversion are arranged in an optical black region and a valid pixel region;

a readout processing unit that applies, to a readout signal of the pixel unit, readout processing corresponding to a reference signal subjected to clamp processing; and

a clamp processing unit that clamps, referring to a readout signal level in the optical black region, a reference signal in the valid pixel region with an acquired clamp value, which is a value with which the signal level is reduced to zero, wherein

the clamp processing unit acquires, when information concerning readout is changed, a clamp value predicted from the clamp value before the change and a ratio of charge accumulation times before and after the change, and

the readout processing unit performs first signal readout processing after the change with a reference signal clamped by the predicted clamp value.

2. A solid-state imaging device according to claim 1, wherein

the clamp processing unit acquires, when a set value of accumulation time is changed, a clamp value predicted from the clamp value before the change and the ratio of charge accumulation times before and after the change, and

the readout processing unit performs first signal readout processing after the setting change with the reference signal clamped by the predicted clamp value.

3. A solid-state imaging device according to claim 1, wherein

the solid-state imaging device has a single frame mode and a plural frame driving mode for combining plural frames having different accumulation times to perform driving for expanding a dynamic range, and

the clamp processing unit acquires, when a mode of the solid-state imaging device is transitioned from single frame driving to plural frame driving, a clamp value of a frame operating before the mode transition as an initial clamp value of a frame started anew.

4. A solid-state imaging device according to claim 3, wherein the clamp processing unit acquires, in acquiring the clamp value of the frame operating before the mode transition as the initial clamp value of the frame started anew, a coefficient corresponding to an accumulation time ratio of the frames in association with the clamp value.

5. A solid-state imaging device according to any one of claim 1, wherein

a plurality of the pixels are arrayed in a matrix shape in the pixel unit,

the readout processing unit includes:

a reference-signal generating unit that generates the reference signal;

plural comparators that are arranged to correspond to column arrays of the pixels and compare readout signal potential and the reference signal, an output level of the comparators being inverted when the readout signal potential and a level of the reference signal coincide with each other; and

plural counters that count comparison time of the comparators corresponding to the counters, operation of the counters being controlled according to outputs of the comparators, and

the clamp processing unit clamps the reference signal with the acquired clamp value.

6. A camera system comprising:

a solid-state imaging device;

an optical system that focuses a subject image on the solid-state imaging device; and

a signal processing circuit that processes an output image signal of the solid-state imaging device, wherein

the solid-state imaging device includes

a pixel unit in which pixels including photoelectric conversion elements are arranged in an optical black region and a valid pixel region,

a readout processing unit that applies, to a readout signal of the pixel unit, readout processing corresponding to a reference signal subjected to clamp processing, and

a clamp processing unit that clamps, referring to a readout signal level in the optical black region, a reference signal in the valid pixel region with an acquired clamp value, which is a value with which the signal level is reduced to zero, and

the clamp processing unit acquires, when information concerning readout is changed, a clamp value predicted from the clamp value before the change and a ratio of charge accumulation times before and after the change, and

the readout processing unit performs first signal readout processing after the change with a reference signal clamped by the predicted clamp value.

7. A camera system according to claim 6, wherein

the clamp processing unit acquires, when a set value of accumulation time is changed, a clamp value predicted from the clamp value before the change and the ratio of charge accumulation times before and after the change, and

the readout processing unit performs first signal readout processing after the setting change with the reference signal clamped by the predicted clamp value.

8. A camera system according to claim 6, wherein

the camera system has a single frame mode and a plural frame driving mode for combining plural frames having different accumulation times to perform driving for expanding a dynamic range, and

the clamp processing unit acquires, when a mode of the camera system is transitioned from single frame driving to plural frame driving, a clamp value of a frame operating before the mode transition as an initial clamp value of a frame started anew.