Exposure control apparatus for vehicle-mounted camera

Patent metadata

Field	Value
Publication number	US-9294681-B2
Application number	US-201113329695-A
Country	US
Kind code	B2
Filing date	Dec 19, 2011
Priority date	Dec 22, 2010
Publication date	Mar 22, 2016
Grant date	Mar 22, 2016

Abstract

The exposure control apparatus is for performing exposure control for a camera mounted on a vehicle in accordance with brightness of a recognition area set in an image ahead of the vehicle taken by the camera. The exposure control apparatus includes a measuring means for measuring brightness of a photometric area showing a landscape more distant from the vehicle than a landscape shown by the recognition area in each of images successively taken by the camera, a detection means for detecting brightness variation with time of the photometric area based on measurement results by the measuring means for images taken by the camera at different times, and a control means configured to predict a timing at which the brightness of the recognition area changes based on the brightness variation with time of the photometric area, and perform exposure control of the camera at the predicted timing.

First claim

What is claimed is:

1. An exposure control apparatus for performing exposure control for a camera mounted on a vehicle in accordance with brightness of a recognition area set in an image ahead of the vehicle taken by the camera, the exposure control apparatus comprising:
a measuring unit measuring brightness of a photometric area showing a landscape more distant from the vehicle than a landscape shown by the recognition area in each of images successively taken by the camera;
a detection unit detecting brightness variation with time of the photometric area based on measurement results by the measuring unit for images taken by the camera at different times; and
a control unit configured to predict a timing at which the brightness of the recognition area changes based on the brightness variation with time of the photometric area detected by the detection unit, and perform exposure control of the camera at the predicted timing;
wherein the control unit is configured to estimate based on a speed of the vehicle, as a next-time recognition area, an image area assumed to be included in the recognition area of an image taken by the camera next time, and determine whether or not the brightness of the recognition area will change at the time when the camera takes an image next time based on brightness variation with time of the next-time recognition area detected by the detection unit;
wherein the detection unit is configured to detect an amount of brightness variation with time of the brightness of the next-time recognition area based on the measurement results by the measuring unit for images taken by the camera at different times, and the control unit is configured to determine whether or not the brightness of the recognition area will change at the time when the camera takes an image next time by comparing the amount of brightness variation with time of the next-time recognition area detected by the detection unit with a determination threshold;
wherein the control unit is configured to make a determination whether or not the brightness of the recognition area will change when the camera takes an image next time, calculate an exposure control value used to control exposure of the camera when the determination is affirmative, and set, as the exposure control value for the time when the camera takes an image next time, the exposure control value previously calculated when the determination is negative;
wherein the photometric area is an area in which the own vehicle is assumed to run at the next image-taking cycle, and
wherein the brightness variation with time of the next-time recognition area is the difference between the brightness measured when an exposure control value was changed last time and the brightness measured this time.

2. The exposure control apparatus according to claim 1 , wherein the control unit is configured to calculate the exposure control value to be used at a time when the camera takes an image next time based on the brightness of the next-time recognition area upon determining that the brightness of the recognition area will change at the time when the camera takes an image next time.

3. The exposure control apparatus according to claim 1 , wherein the photometric area includes the recognition area and the landscape more distant from the vehicle than the landscape shown by the recognition area.

4. The exposure control apparatus according to claim 1 , wherein the measuring unit is configured to measure brightness of each of predetermined parts of the photometric area corresponding to different forward distances from the vehicle, the detection unit is configured to detect brightness variation with time of each of the predetermined parts of the photometric area based on measurement results by the measuring unit, and the control section is configured to predict the timing at which the brightness of the recognition area changes based on the brightness variations with time of the predetermined parts detected by the detection unit.

5. The exposure control apparatus according to claim 4 , wherein the predetermined parts of the photometric parts have shapes of parallel horizontal lines, and the measuring unit is configured to measure a mean value of brightnesses of pixels present on each of the horizontal lines as brightness of each of the forward distances.

6. The exposure control apparatus according to claim 1 , wherein the photometric area is a single area located within the image ahead within which both the landscape and the recognition area separate from the landscape are located.

7. The exposure control apparatus according to claim 6 , wherein the photometric area is less than a total area of the image ahead.

8. The exposure control apparatus according to claim 6 , wherein an upper edge of the photometric area is determined based upon an upper limit speed of the vehicle.

9. The exposure control apparatus according to claim 6 , wherein the landscape is located at an upper side of the photometric area and the recognition area is located at a lower side of the photometric area directly below the landscape.

10. The exposure control apparatus according to claim 9 , wherein the recognition area and the landscape encompasses the entire photometric area.

11. An exposure control apparatus comprising:
a camera mounted on a vehicle, the exposure control apparatus performing exposure control for the camera in accordance with brightness of a recognition area set in a first portion of an image ahead of the vehicle taken by the camera;
a measuring unit measuring brightness of a photometric area set in a second portion of the image ahead of the vehicle taken by the camera different than the first portion, the photometric area showing a landscape more distant from the vehicle than a landscape shown by the recognition area in each of a plurality of images successively taken by the camera;
a detection unit detecting brightness variation with time of the photometric area based on measurement results by the measuring unit for images taken by the camera at different times; and
a control unit configured to predict a timing at which the brightness of the recognition area changes based on the brightness variation with time of the photometric area detected by the detection unit, and perform exposure control of the camera at the predicted timing;
wherein the control unit is configured to estimate based on a speed of the vehicle, as a next-time recognition area, an image area assumed to be included in the recognition area of an image taken by the camera next time, and determine whether or not the brightness of the recognition area will change at the time when the camera takes an image next time based on brightness variation with time of the next-time recognition area detected by the detection unit;
wherein the detection unit is configured to detect an amount of brightness variation with time of the brightness of the next-time recognition area based on the measurement results by the measuring unit for images taken by the camera at different times, and the control unit is configured to determine whether or not the brightness of the recognition area will change at the time when the camera takes an image next time by comparing the amount of brightness variation with time of the next-time recognition area detected by the detection unit with a determination threshold;
wherein the control unit is configured to make a determination whether or not the brightness of the recognition area will change when the camera takes an image next time, calculate an exposure control value used to control exposure of the camera when the determination is affirmative, and set, as the exposure control value for the time when the camera takes

Assignees

• Murao Toshikazu
• Kimura Takayuki
• Denso Corp

Inventors

• Murao Toshikazu
• Kimura Takayuki

Classifications

• H04N23/71

  Circuitry for evaluating the brightness variation · CPC title

• G06V20/588 Primary

  Recognition of the road, e.g. of lane markings; Recognition of the vehicle driving pattern in relation to the road · CPC title

• G06V10/22

  by selection of a specific region containing or referencing a pattern; Locating or processing of specific regions to guide the detection or recognition · CPC title

• G06K9/00798

  Physics · mapped topic

• H04N5/2351 Primary

  Electricity · mapped topic