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

• US 20100256940A1
• Filed: 12/11/2009
• Published: 10/07/2010
• Est. Priority Date: 12/25/2008
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Topcon
• Original Assignee: Kabushiki Kaisha Topcon
• Inventors: Konno, Hiroyuki, Shibuya, Hiroto, DeBoer, Jeffrey Robert, Sasaki, You, Yamaguchi, Shigeyuki, Miyoshi, Ryousuke, Ogawa, Kazuhiro
• Granted Patent: US 8,310,653 B2
• Time in Patent Office: Days
• US Class Current: 702/97
• 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

According to the present invention, a laser scanner measuring system, which has a laser scanner and a calibration target, wherein the 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 the light emitting element and the distance measuring unit, and wherein the calibration target has a reflection sector with a known shape and with high reflectance and is installed at a known position, comprising a step for judging a reflected pulsed laser beam from the reflection sector as received by the distance measuring light receiving unit 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 laser scanner, comprising a light emitting element for emitting a pulsed laser beam, a rotary projecting unit for projecting said 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,

wherein said control unit judges said object to be measured by detecting a level of light quantity of a reflected pulsed laser beam as received by said distance measuring light receiving unit.

2. A laser scanner measuring system, comprising a laser scanner and a calibration target,

wherein said laser scanner comprises a light emitting element for emitting a pulsed laser beam, a rotary projecting unit for projecting said 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 calibration target has a reflection sector with a known shape and with high reflectance,

wherein said control unit judges 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 and determines a center position of said reflection sector based on the result of the judgment.

3. A laser scanner measuring system according to claim 2, wherein said calibration target is installed at a position to be measured, and by measuring a center position of said calibration target by said laser scanner, the position to be measured is determined.

4. A calibration method for calibrating a laser scanner measuring system, which has a laser scanner and a calibration target,

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 calibration target has a reflection sector with a known shape and with high reflectance and is installed at a known position,

comprising 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, a step for determining a center position of said reflection sector based on the result of the judgment, and a step for calibrating said laser scanner measuring system based on the determined center position and on said known position.

5. A calibration method for calibrating a laser scanner measuring system, which has a laser scanner, 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 at a known position, comprising 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, a step for determining a center position of said reflection sector of each of the calibration targets based on the result of the judgment, a step for calculating a distance between said two calibration targets based on the determined center position 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 distance between calibration targets already known.

6. A target for calibration, which is used for a laser scanner to acquire a point group data by projecting a pulsed laser beam for scanning over a predetermined range and by receiving a reflection light of each pulsed beam, comprising a reflection sector with a known shape and with high reflectance, wherein 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.

7. A target for calibration according to claim 6, wherein said target for calibration has a reflection sector formed on a board in form of a flat plate.

8. A target for calibration according to claim 7, wherein said reflection sector is in circular shape.

9. A target for calibration according to claim 7, wherein said reflection sector is in concentric and multi-circular shape.

10. A target for calibration according to claim 6, wherein said target for calibration is a conical member in form of a cone, and a forward end thereof is used as a target.

11. A target for calibration according to claim 10, wherein a coating material with high reflectance factor is coated on a forward end thereof or a member with high reflectance is provided.

12. A target for calibration according to claim 11, wherein a high reflection member in conical shape is removably attached on a forward end thereof.