Inter-car distance detecting device for tracking a car running ahead

• US 5,381,173 A
• Filed: 08/25/1992
• Issued: 01/10/1995
• Est. Priority Date: 08/28/1991
• Status: Expired due to Term

• Current Assignee: Nippondenso Co., Ltd. (DENSO Corporation), Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Asayama, Yoshiaki
• Primary Examiner(s): Chin, Tommy P.
• Assistant Examiner(s): LEE, RICHARD J
• Application Number:
  US07/934,215
• Time in Patent Office: 868 Days
• Field of Search: 358/103, 358/105, 358/107, 358/125, 358/126
• US Class Current: 348/170
• CPC Class Codes: B60R 1/00 Optical viewing arrangements; Real-time viewing arrangements for drivers or passengers using optical image capturing systems, e.g. cameras or video systems specially adapted for use in or on vehicles
• CPC Class Codes: B60R 2300/105 using multiple cameras
• CPC Class Codes: B60R 2300/30 characterised by the type of image processing
• CPC Class Codes: G01S 11/12 using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 3/7865 using correlation of the live video image with a stored image

Abstract

An inter-car distance detecting device for tracking a car running ahead, and automatically setting a tracking window in a display screen. The inter-car distance detecting device has a pair of image sensors which pick up the image of a car running ahead. A window setting section sets a plurality of windows, so that the distances from objects contained in those windows are detected and a position of the car running ahead is detected by comparing the distances corresponding to the windows between containing the car running ahead and un-containing. Thereby, a position and a size of a tracking window is set in the display screen at the position of the car running ahead thus detected.

Claims

1. An inter-car distance detecting device installed on a first car for tracking a second car running ahead of said first car, said inter-car distance detecting device comprising:

a pair of image sensors each for picking up an image of objects including said second car and background;

window setting means for setting a plurality of distance measuring windows in predetermined positions in the image picked up by one of said image sensors, respectively;

distance detecting means for comparing the image contained within each of said distance measuring windows with a corresponding image picked up by the other of said image sensors, to detect distances from said first car to parts of said objects contained within each of said distance measuring windows;

window selecting means for selecting said distance measuring windows which contain the image of said second car according to a detection value of said distance detecting means;

tracking window setting means for automatically setting a tracking window for tracking the image of said second car with reference to said distance measuring windows selected by said window selecting means; and

tracking distance detecting means for detecting a distance to said second car in the image contained within said tracking window,

wherein said window selecting means compares said distances detected by said distance detecting means with each other to select said distance measuring windows which are adjacent to one another and contain the image of the second car having distances which are equal and shorter than those of nonselected distance measuring windows.

2. An inter-car distance detecting device according to claim 1, further comprising display means for displaying said image picked up by one of said sensors, distance measuring windows and tracking windows.

3. An inter-car distance detecting device according to claim 1, wherein said image sensors are positioned along a vertical direction.

4. An inter-car distance detecting device according to claim 1, wherein said tracking window setting means sets a position of said tracking window with reference to a center window of said distance measuring windows selected by said window selecting means.

5. An inter-car distance detecting device according to claim 1, wherein said tracking window setting means sets a size thereof with reference to the number of said distance measuring windows selected by said window selecting means.

6. An inter-car distance detecting device according to claim 1, further comprising an optical system including a pair of lenses corresponding to said pair of image sensors, respectively, wherein said distance detecting means superposes the image contained in one of said distance measuring windows with the image of the other sensor along the position of this window while shifting one pixel element by one pixel element, and detects the amount of shift l when the two images are most closely aligned according to the following equations:

space="preserve" listing-type="equation">R=f×

L/n×

P

space="preserve" listing-type="equation">R=f×

L/l

where R is a distance from the second car running ahead;

P is the pitch of the picture elements;

L is base length of said optical system; and

f is focal distance of said lenses.