Method for determining the position of an object

• US 6,031,600 A
• Filed: 10/20/1998
• Issued: 02/29/2000
• Est. Priority Date: 04/23/1996
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Gaillard, Alain, Winner, Hermann, Uhler, Werner
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US09/171,515
• Time in Patent Office: 497 Days
• Field of Search: 356/5.1, 356/3.01, 356/3.1, 396/106, 180/169
• US Class Current: 356/3.01
• CPC Class Codes: G01S 17/003 Bistatic lidar systems; Multistatic lidar systems
• CPC Class Codes: G01S 17/06 Systems determining position data of a target
• CPC Class Codes: G01S 17/36 with phase comparison between the received signal and the contemporaneously transmitted signal
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/87 Combinations of systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 7/491 Details of non-pulse systems

Abstract

In a method for determining the position of an object with reference to a measurement device having an optical transmitter which emits a light beam at a varying transmission angle, and having an angularly resolving optical receiver spaced away from the transmitter, a conclusion being drawn, from the respective transmission angle and from the respective angle at which the receiver receives radiation reflected from the object (reception angle), as to the resolution cell, defined by the angular resolution of the transmitter and the receiver, in which the object is located, the light beam emitted from the transmitter is modulated. The phase difference between the modulation of the transmitted light beam and the modulation of the received radiation is measured. From the phase difference, the position of the object within the respective resolution cell is calculated.

Claims

1. A method for determining a position of an object using a measurement device, the measurement device including an optical transmitter and an angularly resolving optical receiver situated at a predetermined distance from the optical transmitter, the method comprising the steps of:

defining each of a plurality of resolution cells as a function of a respective set of discrete predetermined transmission and reception angles, the discrete predetermined transmission and reception angles providing an angular resolution of the optical transmitter and the angularly resolving optical receiver;

for each respective set of the discrete predetermined transmission and reception angles, allocating an address in a memory device for storing a corresponding predetermined phase difference and a corresponding predetermined distance from the measurement device to a corresponding cell of the resolution cells;

emitting a light beam, using the optical transmitter, at a particular varying transmission angle;

modulating the light beam to generate a first modulated signal;

receiving a radiation reflected from the object, using the angularly resolving optical receiver, at a particular reception angle;

modulating the received radiation to generate a second modulated signal;

determining a phase difference between the first modulated signal and the second modulated signal;

identifying a particular cell of the resolution cells as a function of the particular varying transmission angle and the particular reception angle, wherein the object is located in the particular cell; and

determining the position of the object within the particular cell as a function of;

the determined phase difference,

the predetermined phase differences, stored in the memory device, which correspond to the particular cell, and

the predetermined distances, stored in the memory device, which correspond to the particular cell.

2. The method according to claim 1, further comprising the steps of:

for the particular cell, retrieving a first distance d₁ and a second distance d₂ of the predetermined distances from the memory device;

for the particular cell, retrieving a first phase difference y₁ and a second phase difference y₂ of the predetermined phase differences from the memory device,

wherein the first distance d₁ and the first phase difference y₁ correspond to a first point of the particular cell which is closest to the measurement device, and the second distance d₂ and the second phase difference y₂ correspond to a second point of the particular cell which is farthest from the measurement device, and

wherein the position determining step includes the substep of;

calculating a particular distance d from the object to the measurement device according to the following equation;

space="preserve" listing-type="equation">d=d.sub.1 +(d.sub.2 -d.sub.1)·

(y-y.sub.1)/(y.sub.2 -y.sub.1),

where y is the determined phase difference.

3. The method according to claim 1, further comprising the step of:

for the particular cell, retrieving a particular distance d₁ of the predetermined distances and a particular phase difference y₁ of the predetermined phase difference from the memory device;

wherein the first distance d₁ and the phase difference y₁ correspond to a point of the particular cell which is closest to the measurement device, and

wherein the position determining step includes the substep of;

calculating a particular distance d from the object to the measurement device according to the following equation;

space="preserve" listing-type="equation">d=d.sub.1 +(y-y.sub.1)*c/(4 π

×

f),

where c is a speed of light, f is a modulation frequency, and y is the determined phase difference.

4. The method according to claim 1, wherein the light beam and the received radiation are modulated using a frequency which corresponds to a wavelength of at least four times a length of a longest cell of the resolution cells.