Distance measuring apparatus

• US 6,657,705 B2
• Filed: 06/20/2002
• Issued: 12/02/2003
• Est. Priority Date: 06/20/2001
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Sano, Naoki, Sugawara, Ryoichi, Isogai, Emiko
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US10/175,508
• Publication Number:
  US 20020196424A1
• Time in Patent Office: 530 Days
• Field of Search: 356/141.1, 356/5-1-, 356/4.01, 180/167
• US Class Current: 356/4.01
• CPC Class Codes: G01C 3/08 Use of electric radiation detectors
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/46 Indirect determination of position data
• CPC Class Codes: G01S 17/931 of land vehicles
• CPC Class Codes: G01S 7/4817 relating to scanning

Abstract

A distance measuring apparatus controls a forward laser beam to scan a detection area. A photodetector array includes a plurality of photo detecting elements. At least one is selected among the photo detecting elements as an effective element, and the effective element is changed from one to another in response to the direction of the forward laser beam. Identification is given of at least one among the photo detecting elements which receives an echo laser beam corresponding to the forward laser beam in a specified direction. An actual correspondence relation between directions of the forward laser beam and the photo detecting elements receiving corresponding echo laser beams is grasped on the basis of a relation between the identified photo detecting element and the specified direction. The selection and change of the effective element are executed according to the grasped actual correspondence relation.

Claims

1. A distance measuring apparatus comprising:

scanning and applying means for applying a forward laser beam to a prescribed detection area, and controlling the forward laser beam to scan the detection area along a scanning direction;

reflected light detecting means for receiving an echo laser beam caused by reflection of the forward laser beam at an object, the reflected light detecting means including a photodetector array in which a plurality of photo detecting elements are arranged in at least one of the scanning direction and a direction perpendicular to the scanning direction, the photodetector array having a visual field wider than a visual field corresponding to the detection area;

changing and selecting means for selecting at least one among the photo detecting elements as an effective element and changing the effective element from one to another in response to a direction of the application of the forward laser beam;

time difference measuring means for measuring a time difference between a moment of the application of the forward laser beam by the scanning and applying means and a moment of the reception of the echo laser beam by the reflected light receiving means;

distance calculating means for calculating one of (1) a distance to the object and (2) a physical quantity indicative of the distance to the object on the basis of the time difference measured by the time difference measuring means; and

correspondence relation grasping means for identifying at least one among the photo detecting elements which receives an echo laser beam corresponding to the forward laser beam applied in a specified direction, and for grasping an actual correspondence relation between directions of the application of the forward laser beam and the photo detecting elements receiving corresponding echo laser beams on the basis of a relation between the identified photo detecting element and the specified direction;

wherein the changing and selecting means includes means for selecting at least one among the photo detecting elements as an effective element and changing the effective element from one to another in response to the direction of the application of the forward laser beam according to the actual correspondence relation grasped by the correspondence relation grasping means.

2. A distance measuring apparatus as recited in claim 1, wherein the correspondence relation grasping means includes (1) means for identifying first one among the photo detecting elements which receives an echo laser beam corresponding to the forward laser beam applied in a first specified direction, (2) means for identifying second one among the photo detecting elements which receives an echo laser beam corresponding to the forward laser beam applied in a second specified direction different from the first specified direction, and (3) means for estimating one among the photo detecting elements which receives an echo laser beam corresponding to the forward laser beam applied in each of directions different from the first and second specified directions on the basis of a relation between the first and second identified photo detecting elements and the first and second specified directions.

3. A distance measuring apparatus as recited in claim 2, wherein the first and second specified directions are two among different directions of the application of the forward laser beam, and an angular difference between the two directions is a greatest.

4. A distance measuring apparatus as recited in claim 2, wherein the photodetector array includes a matrix array of photo detecting elements arranged in the scanning direction and also in the direction perpendicular to the scanning direction, wherein the scanning and applying means includes means for controlling the forward laser beam to scan the detection area along the scanning direction and also along the direction perpendicular to the scanning direction, and wherein the first and second specified directions correspond to corners of the detection area respectively.

5. A distance measuring apparatus as recited in claim 1, wherein the correspondence relation grasping means includes (1) means for identifying first one among the photo detecting elements which receives an echo laser beam corresponding to the forward laser beam applied in a first specified direction, (2) means for identifying second one among the photo detecting elements which receives an echo laser beam corresponding to the forward laser beam applied in a second specified direction different from the first specified direction, (3) means for identifying third one among the photo detecting elements which receives an echo laser beam corresponding to the forward laser beam applied in a third specified direction different from the first and second specified directions, (4) means for identifying fourth one among the photo detecting elements which receives an echo laser beam corresponding to the forward laser beam applied in a fourth specified direction different from the first, second, and third specified directions, and (5) means for estimating one among the photo detecting elements which receives an echo laser beam corresponding to the forward laser beam applied in each of directions different from the first, second, third, and fourth specified directions on the basis of a relation between the first, second, third, and fourth identified photo detecting elements and the first, second, third, and fourth specified directions, wherein the photodetector array includes a matrix array of photo detecting elements arranged in the scanning direction and also in the direction perpendicular to the scanning direction, wherein the scanning and applying means includes means for controlling the forward laser beam to scan the detection area along the scanning direction and also along the direction perpendicular to the scanning direction, and wherein the first, second, third, and fourth specified directions correspond to corners of the detection area respectively.

6. A distance measuring apparatus as recited in claim 1, wherein the correspondence relation grasping means includes (1) means for identifying one among the photo detecting elements which receives an echo laser beam corresponding to the forward laser beam applied in each of all directions of the application of the forward laser beam, and (2) means for grasping the actual correspondence relation on the basis of the identified photo detecting elements.

7. A distance measuring apparatus as recited in claim 1, wherein the correspondence relation grasping means includes (1) means for storing data representing an ideal correspondence relation between directions of the application of the forward laser beam and the photo detecting elements receiving corresponding echo laser beams, (2) means for identifying one among the photo detecting elements which receives an echo laser beam corresponding to the forward laser beam applied in each of at least two different specified directions, (3) means for determining whether or not a relation between the identified photo detecting elements and the specified directions is accorded with the ideal correspondence relation, (4) means for, in cases where it is determined that the relation between the identified photo detecting elements and the specified directions is accorded with the ideal correspondence relation, setting the ideal corresponding relation as the actual correspondence relation, and (5) means for, in cases where it is determined that the relation between the identified photo detecting elements and the specified directions is not accorded with the ideal correspondence relation, grasping the actual correspondence relation on the basis of the relation between the identified photo detecting elements and the specified directions.

8. A distance measuring apparatus as recited in claim 1, wherein the correspondence relation grasping means includes means for implementing the identification of the photo detecting element in response to intensities of echo laser beams received by the respective photo detecting elements.

9. A distance measuring apparatus as recited in claim 1, wherein the correspondence relation grasping means includes means for implementing the identification of the photo detecting element in response to a center of gravity of a configuration of photo detecting elements receiving respective portions of an echo laser beam.

10. A distance measuring apparatus as recited in claim 1, wherein the photodetector array includes a matrix array of photo detecting elements arranged in the scanning direction and also in the direction perpendicular to the scanning direction, and wherein the scanning and applying means includes means for controlling the forward laser beam to scan the detection area along the scanning direction and also along the direction perpendicular to the scanning direction.

11. A distance measuring apparatus as recited in claim 1, wherein the forward laser beam is of a cross section having a first dimension along the scanning direction and a second dimension along the direction perpendicular to the scanning direction, and the second dimension is greater than the first dimension, and wherein the photodetector array includes a plurality of photo detecting elements arranged in the direction perpendicular to the scanning direction.

12. A distance measuring apparatus as recited in claim 1, wherein the changing and selecting means includes means for individually selecting one among the photo detecting elements as an effective element and changing the effective element from one to another in response to the direction of the application of the forward laser beam.

13. A distance measuring apparatus as recited in claim 1, which is mounted on a vehicle, wherein the scanning direction is equal to one of (1) a direction along a width of the vehicle and (2) a direction along a height of the vehicle.

14. A radar apparatus comprising:

a photodetector array including a plurality of photo detecting pixels;

first means for emitting a forward laser beam in specified one among prescribed forward beam directions and detecting one among the photo detecting pixels of the photodetector array which receives an echo laser beam caused by reflection of the emitted forward laser beam at an object, the prescribed forward beam directions corresponding to segments of a prescribed detection area respectively;

second means for determining a correspondence relation between the prescribed forward beam directions and the photo detecting pixels of the photodetector array on the basis of a relation between the specified forward beam direction and the photo detecting pixel detected by the first means, the determined correspondence relation indicating which of the photo detecting pixels is expected to receive an echo laser beam when the forward laser beam is emitted in each of the prescribed forward beam directions;

third means for emitting the forward laser beam and sequentially changing a direction of the emitted forward laser beam among the prescribed forward beam directions to sequentially apply the forward laser beam to the segments of the detection area and thereby scan the detection area; and

fourth means for, when the forward laser beam is emitted in each of the prescribed forward beam directions by the third means, selecting one among the photo detecting pixels of the photodetector array as an effective pixel and setting others of the photo detecting pixels as ineffective pixels in accordance with the correspondence relation determined by the second means.

15. A radar apparatus comprising:

a photodetector array including a plurality of photo detecting pixels;

first means for applying a forward laser beam to specified one among segments of a prescribed detection area and detecting one among the photo detecting pixels of the photodetector array which receives an echo laser beam caused by reflection of the emitted forward laser beam at an object;

second means for determining a correspondence relation between the segments of the detection area and the photo detecting pixels of the photodetector array on the basis of a relation between the specified segment and the photo detecting pixel detected by the first means, the determined correspondence relation indicating which of the photo detecting pixels is expected to receive an echo laser beam when the forward laser beam is applied to each of the segments of the detection area;

third means for sequentially applying the forward laser beam to the segments of the detection area to scan the detection area; and

fourth means for, when the forward laser beam is applied to each of the segments of the detection area by the third means, selecting one among the photo detecting pixels of the photodetector array as an effective pixel and setting others of the photo detecting pixels as ineffective pixels in accordance with the correspondence relation determined by the second means.