Image sensor and control method therefor, and image capturing apparatus

Patent metadata

Field	Value
Publication number	US-10834353-B2
Application number	US-201916387665-A
Country	US
Kind code	B2
Filing date	Apr 18, 2019
Priority date	Apr 24, 2018
Publication date	Nov 10, 2020
Grant date	Nov 10, 2020

Abstract

An image sensor comprising: a generator that generates a plurality of reference signals having different slopes of potential change; a selector that selects one of the reference signals; and an analog/digital converter that converts an analog signal output from a pixel unit by first or second driving using the selected reference signal into a digital signal. In the first driving, a noise signal is converted into a plurality of first digital signals using the reference signals and a photoelectric conversion signal is converted into a second digital signal using one of the reference signals. In the second driving, the noise signal is converted into the first digital signal using a predetermined one of the reference signals and the photoelectric conversion signal is converted into the second digital signal using one of the reference signals. The first driving is performed intermittently.

First claim

What is claimed is:

1. An image sensor comprising:
a generator that generates and outputs a plurality of reference signals whose slopes of potential change per predetermined time are different from each other;
a selector that selects one of the plurality of reference signals; and
an analog/digital converter that converts an analog signal output from a pixel unit row by row by first driving or second driving using the reference signal selected by the selector into a digital signal,
wherein in the first driving, a noise signal output from the pixel unit is converted into a plurality of first digital signals using the plurality of reference signals and a photoelectric conversion signal obtained by performing photoelectric conversion on incident light and output from the pixel unit is converted into a second digital signal using one of the plurality of reference signals,
in the second driving, the noise signal is converted into the first digital signal using a predetermined one of the plurality of reference signals and the photoelectric conversion signal is converted into the second digital signal using one of the plurality of reference signals, and
the first driving is performed intermittently.

2. The image sensor according to claim 1 further comprising:
a holding unit that holds a digital signal converted by the analog/digital converter; and
a processor that processes the digital signal held in the holding unit,
wherein in the first driving, the processor subtracts, from the second digital signal, one of the plurality of first digital signals that is converted using the reference signal having the same slope as the reference signal used for converting the second digital signal, and
in the second driving, the processor subtracts the first digital signal from the second digital signal in a case where the first digital signal and the second digital signal are converted using the reference signals having the same slope, and subtracts the first digital signal held in the holding unit that is converted using the reference signal having the same slope as the reference signal used for converting the second digital signal in a case where the first digital signal and the second digital signal are converted using the reference signals having different slopes.

3. The image sensor according to claim 2 , wherein the holding unit updates the first digital signal each time the noise signal is newly converted using one of the plurality of reference signals except for the predetermined reference signal.

4. The image sensor according to claim 2 , wherein the holding unit averages the first digital signals each time the noise signal is newly converted using one of the plurality of reference signals except for the predetermined reference signal.

5. The image sensor according to claim 1 , wherein, in a case where a temperature of the image sensor is a second temperature that is higher than a first temperature, a frequency of performing the first driving is higher than in a case where the temperature of the image sensor is the first temperature.

6. The image sensor according to claim 1 further comprising an amplifier that applies a gain to the analog signal output from the pixel unit and outputs the amplified analog signal to the analog/digital converter,
wherein in case where the gain is a second gain that is higher than a first gain, a frequency of performing the first driving is higher than in a case where the gain is the first gain.

7. The image sensor according to claim 1 , wherein a signal from a row included in the top region of a frame is converted by the first driving.

8. The image sensor according to claim 1 , wherein the plurality of reference signals are two reference signals of two different slopes, and the predetermined reference signal is the reference signal having a gentler slope.

9. The image sensor according to claim 8 , wherein the analog/digital converter compares the photoelectric conversion signal and a predetermined signal level before converting the photoelectric conversion signal, and in a case where the photoelectric conversion signal is greater than the predetermined signal level, the reference signal having a steeper slope is used to convert the photoelectric conversion signal, and in a case where the photoelectric conversion signal is equal to or less than the predetermined signal level, the reference signal having the gentler slope is used to convert the photoelectric conversion signal.

10. An image sensor comprising:
a pixel unit including pixels each having a plurality of photoelectric conversion portions and corresponding to each of a plurality of microlenses arranged in matrix;
a generator that generates and outputs a plurality of reference signals whose slopes of potential change per predetermined time are different from each other;
a selector that selects one of the plurality of reference signals; and
an analog/digital converter that converts an analog signal output from a pixel unit row by row in a first mode or second mode using the reference signal selected by the selector into a digital signal,
wherein in the first mode, a noise signal output from the pixel unit is converted into a first digital signal using a predetermined one of the plurality of reference signals and a first photoelectric conversion signal obtained by performing photoelectric conversion on incident light and output from the pixel unit is converted into a second digital signal using one of the plurality of reference signals,
in the second mode, the noise signal is converted into a plurality of first digital signals using the plurality of reference signals and third and fourth photoelectric conversion signals that are read out from the pixel unit so as to be able to obtain a pair of focus detection signals having parallax are converted into third and fourth digital signals, respectively, using one of the plurality of reference signals, and
signals from a row including an area in which focus detection is performed are processed in the second mode.

11. The image sensor according to claim 10 further comprising:
a holding unit that holds a digital signal converted by the analog/digital converter; and
a processor that processes the digital signal held in the holding unit,
wherein in the first mode, the processor subtracts the first digital signal from the second digital signal in a case where the first digital signal and the second digital signal are converted using the reference signals having the same slope, and subtracts the first digital signal held in the holding unit that is converted using the reference signal having the same slope as the reference signal used for converting the second digital signal in a case where the first digital signal and the second digital signal are converted using the reference signals having different slopes, and
in the second mode, the processor subtracts, from the third and fourth digital signals, the first digital signal/signals among the plurality of first digital signals that is/are converted using the reference signal/signals having the same slope/slopes as the reference signals used for converting the third and fourth digital signals.

12. The image sensor according to claim 11 , wherein the holding unit updates the first digital signal each time the noise signal is newly converted using one of the plurality of reference signals except for the predetermined reference signal.

13. The image sensor according to claim 11 , wherein the holding unit averages the first digital signals each time the noise signal is newly converted using one of the plurality of reference signals except for the predetermined reference signal.

Assignees

• Canon Kk

Inventors

• Ohshitanai Kazuki

Classifications

• H04N25/704 Primary

  Pixels specially adapted for focusing, e.g. phase difference pixel sets · CPC title

• H04N25/78

  Readout circuits for addressed sensors, e.g. output amplifiers or A/D converters · CPC title

• H04N25/61

  the noise originating only from the lens unit, e.g. flare, shading, vignetting or "cos4" · CPC title

• H04N25/772

  comprising A/D, V/T, V/F, I/T or I/F converters · CPC title

• H04N25/616 Primary

  involving a correlated sampling function, e.g. correlated double sampling [CDS] or triple sampling · CPC title