Distance measurement method and device

• US 7,145,502 B2
• Filed: 06/04/2003
• Issued: 12/05/2006
• Est. Priority Date: 06/07/2002
• Status: Expired due to Fees

• Current Assignee: Shima Seiki Manufacturing Limited
• Original Assignee: Shima Seiki Manufacturing Limited
• Inventors: Uebo, Tetsuji, Iritani, Tadamitsu
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US10/506,014
• Publication Number:
  US 20060023571A1
• Time in Patent Office: 1,280 Days
• Field of Search: 180167-169, 701/300, 701/301, 342/27, 342/28, 342 70- 72, 342/175, 342/176, 342/179, 342195-197, 342118-145, 342165-174
• US Class Current: 342/131
• CPC Class Codes: G01S 13/32 using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
• CPC Class Codes: G01S 13/887 for detection of concealed objects, e.g. contraband or weapons

Abstract

A distance can be measured with high resolution. A frequency controller (7) controls a voltage control oscillator (2) so as to change a signal source frequency f in a range containing two center frequencies f1 and f2 and transmits it as a traveling wave from an antenna (4) to a target (5). A reflected wave reflected by the target (5) and the traveling wave interfere each other and form a standing wave. A power detector (6) detects power corresponding to the amplitude of the standing wave and performs Fourier transform based on the two center frequencies f1 and f2 in Fourier transform means (11, 12), respectively, thereby calculating radar image functions P1(x), P2(x). The distance d to the target (5) satisfies the conditions that the phase difference of the two radar image functions zero-crosses and the amplitude of the radar image functions becomes maximum. The zero cross point of the phase difference is a zero cross point of a linear function and can be identified with high resolution.

Claims

1. A distance measuring method for measuring a distance from a reference position to an object to be measured, comprising the steps of:

a standing wave generating step for generating traveling waves that travel from the reference position to the object to be measured in a propagation medium existing surrounding the reference position and the object to be measured while varying the frequency, and causing the generated traveling waves to interfere with the waves reflected by the object to be measured to thereby generate standing waves;

a standing wave detecting step for detecting the standing waves generated in the standing wave generating step;

a radar image calculating step for calculating a plurality of radar image functions from the standing waves detected in the standing wave detecting step based on a plurality of different center frequencies in which radar image functions a variable is a distance from the reference position to a point on an imaginary linear axis passing through the object to be measured; and

a distance judging step for judging, as the distance from the reference position to the object to be measured, a distance in which predetermined conditions are satisfied by phase differences among a plurality of radar image functions calculated in the radar image calculating step and by an amplitude of any of the radar image functions.

2. The distance measuring method of claim 1, wherein an object to be measured for which a distance is measured and an object to be measured that serves as a reference for measuring the distance are simultaneously measured.

3. A distance measuring apparatus for measuring a distance from a reference position to an object to be measured, comprising:

traveling wave generating means for generating traveling waves that travel from the reference position to the object to be measured in a propagation medium existing surrounding the reference position and the object to be measured while varying the frequency;

standing wave detecting means for detecting the standing waves which are generated by interference of traveling waves generated by the traveling wave generating means, with waves which are reflected by the object to be measured and return to the traveling wave generating means side, and thereby deriving signals corresponding to the standing waves;

radar image calculating means for calculating a plurality of radar image functions based on a plurality of different center frequencies by operating the signals corresponding to the standing waves derived from the standing wave detecting means in which radar image functions a variable is a distance from the reference position to a point on an imaginary linear axis passing through the object to be measured; and

distance judging means for judging, as the distance from the reference position to the object to be measured, distance in which predetermined conditions are satisfied by phase differences among a plurality of radar image functions calculated by the radar image calculating means and by the amplitude of any of radar image functions.

4. The distance measuring apparatus of claim 3, wherein the radar image calculating means calculates the plurality of radar image functions based on a Fourier transform processing;

and

the distance judging means judges, as the distance in which the above predetermined conditions are satisfied, a distance in which a phase difference between at least two radar images functions is 0 or is a radian value of an even number of times of the pi π

, and the amplitude of at least any one of the radar image functions is an extreme value.

5. The distance measuring apparatus of claim 4, wherein the radar image calculating means calculates the plurality of radar image functions by subjecting the signals corresponding to the standing waves to the Fourier transform processing with a variable common width for the plurality of different center frequencies by using a predetermined window function.

6. The distance measuring apparatus of claim 5, wherein the traveling wave generating means includes:

an oscillator capable of controlling oscillation frequency and of generating high-frequency signals;

a controller for periodically varying the oscillation frequency of the oscillator within a predetermined range; and

an antenna for transmitting high-frequency signals from the oscillator as electromagnetic traveling waves into space which the propagation medium; and

the standing wave detecting means detects the standing waves by using the antenna.

7. The distance measuring apparatus of claim 4, wherein the traveling wave generating means includes:

an oscillator capable of controlling oscillation frequency and of generating high-frequency signals;

a controller for periodically varying the oscillation frequency of the oscillator within a predetermined range; and

an antenna for transmitting high-frequency signals from the oscillator as electromagnetic traveling waves into space which the propagation medium; and

the standing wave detecting means detects the standing waves by using the antenna.

8. The distance measuring apparatus of claim 3, wherein the traveling wave generating means includes:

an oscillator capable of controlling oscillation frequency and of generating high-frequency signals;

a controller for periodically varying the oscillation frequency of the oscillator within a predetermined range; and

an antenna for transmitting high-frequency signals from the oscillator as electromagnetic traveling waves into space which the propagation medium; and

the standing wave detecting means detects the standing waves by using the antenna.