Exposure controller

Patent metadata

Field	Value
Publication number	US-9584732-B2
Application number	US-201414469479-A
Country	US
Kind code	B2
Filing date	Aug 26, 2014
Priority date	Feb 27, 2012
Publication date	Feb 28, 2017
Grant date	Feb 28, 2017

Abstract

An image sensor provides a first image with a first exposure and a second image with a second exposure. An exposure controller sets the first exposure in dependence on pixel intensities of at least one of the images. It sets the second exposure in dependence on a factor and the first exposure. The factor is determined in dependence on pixel intensities of at least one of the images.

First claim

What is claimed is:

1. An exposure controller for controlling an exposure of a plurality of pixels of an image sensor, the image sensor providing a first image having a first exposure and a second image having a second exposure, the first image and the second image being in a time sequence of images captured by the image sensor, the exposure controller being arranged to:
set the first exposure in dependence on pixel intensities of one of the time sequence of images;
determine pixel populations in a shadows zone, a midtones zone and a highlights zone of one of the time sequence of images;
calculate a factor in dependence at least in part on the pixel populations of the shadows zone and the highlights zone relative to the pixel population of the midtones zone; and
set the second exposure in dependence on the factor and the first exposure.

2. The exposure controller according to claim 1 , wherein the factor is multiplicative and the second exposure is proportional to the first exposure and the factor.

3. The exposure controller according to claim 1 , wherein the factor and/or the first exposure is derived from an intensity histogram having a number of zones, each zone having a weighting factor for weighting the pixel population in the zone.

4. The exposure controller according to claim 3 , wherein the weighting reduces the number of pixels in the highlights zone relative to the total number of pixels.

5. The exposure controller according to claim 3 , wherein the factor is based on a sum of a fixed constant and a weighted average of the pixel populations.

6. The exposure controller according to claim 1 , wherein the first exposure is based on a weighted average of a distribution of the pixel intensities.

7. The exposure controller according to claim 1 , wherein the first exposure is a low exposure having a number of pixels clipped at a maximum intensity, the number being lower than a pre-determined threshold.

8. The exposure controller according to claim 1 , wherein the image sensor is arranged to provide a third image having a third exposure, the third exposure being between the first exposure and the second exposure.

9. A system for capturing images including an image sensor and an exposure controller according to claim 1 .

10. A method of controlling an exposure of a plurality of pixels of an image sensor, the image sensor providing a first image having a first exposure and a second image having a second, different exposure, the first image and the second image being in a time sequence of images captured by the image sensor, the method comprising:
setting the first exposure in dependence on pixel intensities of one of the time sequence of images;
determining pixel populations in a shadows zone, a midtones zone and a highlights zone of one of the time sequence of images;
calculating a factor in dependence at least in part on the pixel populations of the shadows zone and the highlights zone relative to the pixel population of the midtones zone; and
setting the second exposure in dependence on the factor and the first exposure.

11. The method of claim 10 , wherein the factor is a ratio and the second exposure is proportional to the first exposure and the ratio.

12. The method of claim 10 , including the step of deriving the factor and/or the first exposure from an intensity histogram having a number of zones, each zone having a weighting factor for weighting the pixel population in the zone.

13. A non-transitory computer-readable storage medium comprising computer-executable instructions which, when executed by a processor, cause a computing device to control an exposure of a plurality of pixels of an image sensor, the image sensor providing a first image having a first exposure and a second image having a second, different exposure, the first image and the second image being in a time sequence of images captured by the image sensor, the computing device configured to control the exposure of the plurality of pixels of the image sensor by:
setting the first exposure in dependence on pixel intensities of one of the time sequences of images;
determining pixel populations in a shadows zone, a midtones zone and a highlights zone of one of the time sequence of images;
calculating a factor in dependence at least in part on the pixel populations of the shadows zone and the highlights zone relative to the pixel population of the midtones zone; and
setting the second exposure in dependence on the factor and the first exposure.

Assignees

• Apical Ltd
• Apical Ltd

Inventors

• Romanenko Ilya

Classifications

• H04N23/741

  by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors · CPC title

• H04N23/743 Primary

  Bracketing, i.e. taking a series of images with varying exposure conditions · CPC title

• H04N23/73 Primary

  by influencing the exposure time · CPC title

• H04N23/71

  Circuitry for evaluating the brightness variation · CPC title

• H04N5/2356

  Electricity · mapped topic