Shutter speed control method and system

• US 5,650,944 A
• Filed: 02/13/1996
• Issued: 07/22/1997
• Est. Priority Date: 03/24/1993
• Status: Expired due to Term

• Current Assignee: Hoechst Aktiengesellschaft (Sanofi )
• Original Assignee: Fuji Heavy Industries Limited (Subaru Corp.)
• Inventors: Kise, Katsuyuki
• Primary Examiner(s): Trammell, James P.
• Application Number:
  US08/598,637
• Time in Patent Office: 525 Days
• Field of Search: 364/561, 364/424.01, 364/424.02, 348/113, 348/116, 348/118, 348/143, 348/148, 348/42-50, 382/106, 382/280, 382/168, 396/169, 396/246, 396/324, 33/20.4
• US Class Current: 700/304
• CPC Class Codes: B60K 31/0008 including means for detecting potential obstacles in vehicle path
• CPC Class Codes: B60Q 9/008 for anti-collision purposes
• CPC Class Codes: G01C 3/08 Use of electric radiation detectors
• CPC Class Codes: G01S 1/753 Signal details
• CPC Class Codes: G01S 11/12 using electromagnetic waves other than radio waves
• CPC Class Codes: G05D 1/0251 extracting 3D information from a plurality of images taken from different locations, e.g. stereo vision stereoscopic image analysis H04N13/00; depth recovery from images G06T7/593
• CPC Class Codes: G06T 2207/10012 Stereo images
• CPC Class Codes: G06T 2207/30252 Vehicle exterior; Vicinity of vehicle
• CPC Class Codes: G06T 2207/30261 Obstacle
• CPC Class Codes: G06T 7/593 from stereo images
• CPC Class Codes: H04N 13/133 Equalising the characteristics of different image components, e.g. their average brightness or colour balance
• CPC Class Codes: H04N 13/167 Synchronising or controlling image signals
• CPC Class Codes: H04N 13/189 Recording image signals; Reproducing recorded image signals
• CPC Class Codes: H04N 13/239 using two 2D image sensors having a relative position equal to or related to the interocular distance H04N13/243 takes precedence
• CPC Class Codes: H04N 13/243 using three or more 2D image sensors
• CPC Class Codes: H04N 13/246 Calibration of cameras
• CPC Class Codes: H04N 13/25 using two or more image sensors with different characteristics other than in their location or field of view, e.g. having different resolutions or colour pickup characteristics; using image signals from one sensor to control the characteristics of another sensor
• CPC Class Codes: H04N 13/296 Synchronisation thereof; Control thereof
• CPC Class Codes: H04N 2013/0077 Colour aspects
• CPC Class Codes: H04N 2013/0081 Depth or disparity estimation from stereoscopic image signals
• CPC Class Codes: H04N 2013/0092 : Image segmentation from stereoscopic image signals
• CPC Class Codes: H04N 2013/0096 : Synchronisation or controlling aspects

Abstract

A distance detecting system for detecting a distance to an object from a moving body such an automobile by means of imaging pictures by an imaging apparatus and processing pictures into distance distribution information, the imaging apparatus having a capability of always providing proper image pictures under rapidly changing illuminance conditions, whereby securing an accuracy in the distance detecting system.

Claims

1. A shutter speed control method for controlling a shutter speed of a stereoscopical imaging apparatus which images an object from a plurality of different directions, the method comprising the steps of:

dividing the image of the object produced by the imaging apparatus into a plurality of zones;

averaging a brightness for each zone to produce an average brightness value for each zone;

for each zone, determining a zone correction level with respect to a present shutter speed of the imaging apparatus, based upon the average brightness value for the zone;

producing a shutter speed correction level based upon the determined zone correction levels; and

correcting said present shutter speed of the imaging apparatus based on the shutter speed correction level, to thereby obtain a new shutter speed for the imaging apparatus.

2. A shutter speed control method according to claim 1, wherein the determined zone correction level for each zone is determined from a zone correction level map, the zone correction level map identifying a zone correction level for each of a predetermined number of combinations of a current shutter speed of the imaging apparatus and an average brightness value for the zone.

3. A shutter speed control method according to claim 1, wherein the shutter speed correction level is obtained by adding the determined zone correction levels.

4. A shutter speed control method for controlling a shutter speed of a stereoscopical imaging apparatus which images an object from a plurality of different directions, the method comprising the steps of:

designating at least one particular zone of the image of the object produced by the imaging apparatus;

calculating a frequency distribution of brightness levels in the particular zone;

producing a brightness histogram for the particular zone from the calculated frequency distribution of brightness levels;

calculating a correction level with respect to a present shutter speed of the imaging apparatus based upon the brightness histogram; and

correcting the present shutter speed of the imaging apparatus based upon the correction level, to thereby produce a new shutter speed for the imaging apparatus.

5. A shutter speed control method according to claim 4, wherein the correction level is calculated based upon a difference (F_i-j (t)) between a frequency of a highest brightness level in the particular zone and a frequency of a lowest brightness level in the particular zone.

6. A shutter speed control method according to claim 5, wherein the correction level (Δ

SSL(t)) is calculated according to a set of rules including the following;

when F_i-j (t)<

-n/2, then Δ

SSL(t)=SSL(t)/2;

when -n/2≦

F_i-j (t)<

-n/4, then Δ

SSL(t)=SSL(t)/4;

when -n/4≦

F_i-j (t)<

-n/8, then Δ

SSL(t)=SSL(t)/8;

when n/8≦

F_i-j (t)<

n/4, then Δ

SSL(t)=-SSL(t)/8;

when n/4≦

F_i-j (t)<

n/2, then Δ

SSL(t)=-SSL(t)/4; and

when n/2≦

F_i-j (t), then Δ

SSL(t)=-SSL(t)/2;

where SSL(t) is the current shutter speed for the imaging apparatus and n is the number of samples of brightness levels obtained from the image for the brightness histogram, and wherein

the new shutter speed SSL(t+1)=SSL(t)+Δ

SSL(t).

7. A shutter speed control system for controlling a shutter speed of a stereoscopical imaging apparatus which images an object from a plurality of different directions, the system comprising:

zone dividing means for dividing the image of the object produced by the imaging apparatus into a plurality of zones;

brightness averaging means for averaging a brightness of each zone and for producing an average brightness value for each zone; and

correction level determining means for determining a zone correction level with respect to a present shutter speed of the imaging apparatus for each zone, in response to the average brightness value for the zone, and for producing a shutter speed correction level based upon the determined zone correction levels.

8. A shutter speed control system according to claim 7, further including memory means for storing at least one zone correction level map, each zone correction level map identifying a correction level for each of a predetermined number of combinations of a current shutter speed of the imaging apparatus and an average brightness value for the zone, whereby the correction level determining means determines each determined zone correction level from a zone correction level map stored in the memory means.

9. An imaging system according to claim 7, wherein the correction level determining means includes addition means for adding the determined zone correction levels to obtain the shutter speed correction level.

10. An imaging system comprising:

an imaging apparatus for imaging an object from a plurality of different directions; and

a shutter speed control system as set forth in claim 7.

11. An imaging system according to claim 10, wherein the imaging apparatus is provided with two image cameras having solid state camera elements for imaging an object at a short distance.

12. An imaging system according to claim 10, wherein the imaging apparatus is provided with two image cameras having solid state camera elements for imaging an object at a long distance.

13. A shutter speed control system for controlling a shutter speed of a stereoscopical imaging apparatus which images an object from a plurality of different directions, the system comprising:

zone designating means for designating at least one particular zone of the image of the object produced by the imaging apparatus;

frequency distribution producing means for calculating a frequency distribution of brightness in the particular zone and for producing a brightness histogram for the particular zone from the calculated frequency distribution of brightness;

correction level calculating means for calculating a correction level with respect to a present shutter speed of the imaging apparatus in response to the brightness histogram; and

shutter speed correcting means for correcting the present shutter speed of the imaging apparatus in response to the calculated correction level, to thereby produce a new shutter speed for the imaging apparatus.

14. The shutter speed control system according to claim 13, wherein the correction level calculating means calculates the correction level based upon a difference (F_i-j (t)) between a frequency of a highest brightness level in the particular zone and a frequency of a lowest brightness level in the particular zone.

15. The shutter speed control system according to claim 14, wherein the correction level calculating means calculates the correction level (Δ

SSL(t)) according to a set of rules including the following;

when F_i-j (t)<

-n/2, then Δ

SSL(t)=SSL(t)/2;

when -n/2≦

F_i-j (t)<

-n/4, then Δ

SSL(t)=SSL(t)/4;

when -n/4≦

F_i-j (t)<

-n/8, then Δ

SSL(t)=SSL(t)/8;

when n/8≦

F_i-j (t)<

n/4, then Δ

SSL(t)=-SSL(t)/8;

when n/4≦

F_i-j (t)<

n/2, then Δ

SSL(t)=-SSL(t)/4; and

when n/2≦

F_i-j (t), then Δ

SSL(t)=-SSL(t)/2;

where SSL(t) is the current shutter speed for the imaging apparatus and n is the number of samples of brightness levels obtained from the image for the brightness histogram, and wherein

the new shutter speed SSL(t+1)=SSL(t)+Δ

SSL(t).

16. An imaging system comprising:

an imaging apparatus for imaging an object from a plurality of different directions; and

a shutter speed control system as set forth in claim 13.

17. An imaging system according to claim 16, wherein the imaging apparatus is provided with two image cameras having solid state camera elements for imaging an object at a short distance.

18. An imaging system according to claim 16, wherein the imaging apparatus is provided with two image cameras having solid state camera elements for imaging an object at a long distance.