Distance measuring apparatus

• US 5,131,740 A
• Filed: 11/27/1991
• Issued: 07/21/1992
• Est. Priority Date: 11/29/1990
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Maekawa, Hiroko
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US07/798,954
• Time in Patent Office: 237 Days
• Field of Search: 356/1, 356/4, 354/402-409
• US Class Current: 356/3.14
• CPC Class Codes: G01S 11/12 using electromagnetic waves other than radio waves

Abstract

A distance measuring apparatus includes a pair of first and second image sensors, and a pair of first and second memories for successively storing a pair of first and second image signals output from the first and second image sensors. A CPU sets a window for the first image signal and compares a reference image signal within the window with the second image signal while shifting these signals relative to each other to thereby arithmetically measure a distance to the object. A window memory stores the reference image signal within the window. The CPU further compares the reference image signal within the window memory with first image signals stored in the first memory after a predetermined time, so as to find the most similar first image signal and set a provisional window enclosing it. Displacing the provisional window around it initially set position, the position of the window is updated only when the image signal within the provisional window as displaced exhibits a horizontal symmetry. Thus, the process and hence time for distance measurement can significantly be simplified and reduced while ensuring high accuracy and reliability.

Claims

1. A distance measuring apparatus comprising:

a pair of first and second image sensors;

a pair of optical systems for focusing an image of an object on said image sensors, respectively;

a pair of first and second memories for storing a pair of first and second image signals output from said first and second image sensors;

window setting means for setting a window for said first image signal from said first image sensor;

arithmetic means for performing comparison between a reference image signal located within said window and said second image signal from said second image sensor while shifting these image signals relative to each other to thereby arithmetically determine a distance to said object;

a window memory for storing said reference image signal within said window;

provisional window setting means for comparing said reference image signal within said window memory with first image signals stored in said first memory after a predetermined time has elapsed from the time when said reference image signal is stored in said window memory, so as to determine an image signal in said first memory which is most similar to said reference image, said provisional window setting means being operable to set a provisional window enclosing the most similar image signal; and

window updating means for displacing said provisional window around the initially set position thereof to determine a position thereof in which said image signal within said provisional window is horizontally symmetric with respect to a vertical center line of said provisional window, said window updating means being operable to update the position of said window to be the position of said provisional window thus determined only when said image within said provisional window has a horizontal symmetry.