Distance measurement method and apparatus, and relative position measurement apparatus

• US 5,128,961 A
• Filed: 11/26/1990
• Issued: 07/07/1992
• Est. Priority Date: 11/24/1989
• Status: Expired due to Term

• Current Assignee: Daikin Industries Ltd
• Original Assignee: Daikin Industries Ltd
• Inventors: Ueda, Tomoaki, Obata, Koei
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): CAIN, DAVID C
• Application Number:
  US07/617,769
• Time in Patent Office: 589 Days
• Field of Search: 375/1, 342/458, 342/378, 380/48, 380/34, 364/717
• US Class Current: 375/142
• CPC Class Codes: G01S 15/325 using transmission of coded signals, e.g. of phase-shift keyed [PSK] signals
• CPC Class Codes: G01S 5/22 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/28 takes precedence
• CPC Class Codes: G01S 5/30 Determining absolute distances from a plurality of spaced points of known location

Abstract

A distance measurement apparatus receives pseudo noise reflected from a target object. The apparatus then obtains a cross-correlation value from cross-correlation of the received pseudo noise with pseudo noise which has been convoluted with expected measurement values. The apparatus measures a distance to the target object based upon the cross-correlation value. Also, a relative position measurement apparatus measures distances to an operator from plural points on the apparatus and then measures a relative position of the operator with respect to the apparatus based upon the plural distances.

Claims

1. A distance measurement method comprising the steps of:

radiating pseudo noise which has significant auto-correlation characteristics to a target object;

receiving pseudo noise reflected from the target object;

cross-correlating received reflected pseudo noise with convolution noise which is obtained by convoluting pseudo noises which are multiplied by different corresponding coefficients to obtain a cross-correlation value; and

measuring the distance based upon said obtained cross-correlation value.

2. A distance measurement method as set forth in claim 1, wherein said pseudo noise is a maximal-sequence code and said convolution noise is obtained by convoluting expected values as coefficients with the pseudo noise.

3. A distance measurement method as set forth in claim 1, wherein said expected values have monotonously varying values other than 0 within a permitted measurement range and have 0 value outside the permitted range.

4. A distance measurement apparatus comprising;

transmission means for modulating a carrier signal with pseudo noise to obtain a modulated signal and for radiating said modulated signal to a target object; and

receiving means for receiving a signal reflected from the target object and for obtaining a distance to the target object,

said receiving means includes convolution code output means for outputting a convolution code which is obtained by convoluting expected values which are different from one another with every shifted pseudo noise bit, said transmission means having a sequence code which is the same as a sequence code used for convolution by said convolution code output means, cross-correlation means for cross-correlating the received pseudo noise with said convolution code to obtain a cross-correlation value, and distance calculation means for calculating the distance based upon said cross-correlation value.

5. A distance measurement apparatus as set forth in claim 4, wherein said pseudo noise is a maximal-sequence code and said convolution code is obtained by convoluting expected values as coefficients with said pseudo noise.

6. A distance measurement apparatus as set forth in claim 4, wherein said expected values have montonously varying values other than 0 within a permitted measurement range and have 0 value outside the permitted range.

7. A relative position measurement apparatus comprising;

a pseudo noise radiation source means for radiating pseudo noise worn to an operator of an apparatus;

plural pseudo noise receiving means for obtaining distances to the operator, the receiving means being attached to the apparatus of predetermined positions which are apart from one another; and

relative position obtaining means for obtaining a relative position of the operator based on the distances obtained by said pseudo noise receiving means,

wherein said pseudo noise receiving means includes convolution code output means for outputting a convolution code which is obtained by convoluting expected values which are different from one another with every bit of shifted pseudo noise, said radiated pseudo noise being a sequence code for convolution by said convolution code output means, cross-correlation means for cross-correlating the received pseudo noise with said convolution code to obtained 0 cross-correlation value, and distance calculation means for calculating the distance based upon said cross-correlation value.

8. A relative position measurement apparatus as set forth in claim 7, wherein said pseudo noise radiation source means is a maximal-sequence sound source, said apparatus is a three-dimensional graphics display apparatus, and said three-dimensional graphics display apparatus determines a viewing direction based upon the calculated relative position.

9. A relative position measurement apparatus as set forth in claim 7, wherein said convolution code output means outputts a convolution code which is obtained by convoluting expeected values having monotonously varying values other than 0 within a permitted measurement range and having 0 value outside the permitted range.