Laser scanner, laser scanner measuring system, calibration method for laser scanner measuring system and target for calibration

• US 8,355,118 B2
• Filed: 04/18/2012
• Issued: 01/15/2013
• Est. Priority Date: 12/25/2008
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Topcon
• Original Assignee: Kabushiki Kaisha Topcon
• Inventors: Shibuya, Hiroto, Konno, Hiroyuki, DeBoer, Jeffrey Robert, Ogawa, Kazuhiro, Yamaguchi, Shigeyuki, Miyoshi, Ryousuke, Sasaki, You
• Primary Examiner(s): NGUYEN, SANG H
• Application Number:
  US13/449,389
• Publication Number:
  US 20120218546A1
• Time in Patent Office: 272 Days
• Field of Search: 356/601, 356607-608, 356/614, 356/625, 356/4.01, 356/5.01, 356/5.13, 356/141.3, 356/141.1, 356/4.07, 356/28, 250/559.19, 382/109, 382/154
• US Class Current: 356/4.07
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4812 transmitted and received beams following a coaxial path
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating

Abstract

A laser scanner measuring system is disclosed, which has a laser scanner and a calibration target. The laser scanner comprises a light emitting element for emitting a pulsed laser beam, a rotary projecting unit for projecting the pulsed laser beam, a distance measuring unit, and a control unit for driving and controlling the light emitting element and the distance measuring unit. The calibration target has a reflection sector with a known shape and with high reflectance and is installed at a known position. In use, there is a step for judging a reflected pulsed laser beam from the reflection sector by detecting a level of light quantity, a step for determining a center position of the reflection sector based on the result of the judgment, and a step for calibrating the laser scanner measuring system based on the determined center position and on the known position.

Claims

1. A calibration method for calibrating a laser scanner measuring system, which has a laser scanner, a control unit, a moving object where said laser scanner is installed and at least two calibration targets,

wherein said laser scanner comprises a light emitting element for emitting a pulsed laser beam, a rotary projecting unit for projecting the pulsed laser beam for scanning, a distance measuring unit, which has a distance measuring light receiving unit, for measuring a distance by receiving a reflection light from an object to be measured, and a control unit for driving and controlling said light emitting element and said distance measuring unit,

and wherein said at least two calibration targets have a reflection sector with a known shape and with high reflectance and are installed each along an advancing direction of said moving object at a known position and at a known interval, comprising a step for advancing said moving object at a predetermined speed while said moving object emits said pulsed laser beam, a step for judging a reflected pulsed laser beam from said reflection sector as received by said distance measuring light receiving unit by detecting a level of light quantity in a moving process of said moving object, a step for determining three-dimensional positional data of a center position of said reflection sector of each of the calibration targets based on the result of the judgment using said control unit, a step for calculating a distance between said two calibration targets based on the three-dimensional positional data of the two determined center positions using said control unit and a step for calibrating the laser scanner measuring system based on a comparison of the calculated distance between each of said calibration targets with the known interval.

2. The calibration method according to claim 1, wherein said pulsed laser beam is scanned in a vertical direction and according to the scanning in said vertical direction and the advancing of said moving object, a pulsed light is scanned over a whole surface of said target, and said reflection sector is so designed that said pulsed laser beam is projected at least three points in peripheral region of each edge opposite to each other of said reflection sector.

3. The calibration method according to claim 1 or 2, wherein said reflection sector formed on a board with low reflectance in form of a flat plate.

4. The calibration method according to claim 3, wherein said reflection sector is in circular shape.

5. The calibration method according to claim 3, wherein said reflection sector is in concentric and multi-circular shape.

6. The calibration method according to claim 1 or 2, wherein each of said calibration targets is a conical member in form of a cone, and a forward end thereof is used as a target.

7. The calibration method according to claim 6, wherein a coating material with high reflectance factor is coated on a forward end thereof or a member with high reflectance is provided.

8. The calibration method according to claim 7, wherein a high reflection member in conical shape is removably attached on a forward end thereof.