Electro-optical distance measuring method and electro-optical distance measuring device

• US 8,781,780 B2
• Filed: 12/25/2009
• Issued: 07/15/2014
• Est. Priority Date: 01/22/2009
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Topcon
• Original Assignee: Kabushiki Kaisha Topcon
• Inventors: Kanokogi, Mitsuru, Ohishi, Masahiro
• Primary Examiner(s): Kundu, Sujoy
• Assistant Examiner(s): FORTICH, ALVARO E
• Application Number:
  US13/144,196
• Publication Number:
  US 20110270563A1
• Time in Patent Office: 1,663 Days
• Field of Search: 702/97
• US Class Current: 702/97
• CPC Class Codes: G01C 15/002 Active optical surveying means optical plumbing G01C15/105
• CPC Class Codes: G01S 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating

Abstract

The present invention provides an electro-optical distance measurement, wherein a light from a light source (6) is projected toward an object to be measured (2), a reflection light reflected by the object to be measured is received at a photodetection unit (8), the light from the light source is received by the photodetection unit as an inner light via an inner optical path (11), and a distance to the object to be measured is measured according to the result of photodetection of the reflection light and the inner light of the photodetection unit, and wherein a correction information is acquired based on the inner light, the acquired correction information is stored, a correction value is obtained from the correction information based on the reflection light and the inner light, and a distance is calculated from the correction value and the result of photodetection of the reflection light and the inner light.

Claims

1. An electro-optical distance measuring method for projecting a light from a light source toward an object to be measured, for receiving a reflection light from the object to be measured at a photodetection unit, for receiving the light from said light source as an inner light via an inner optical path by said photodetection unit, and for measuring a distance to the object to be measured according to the result of photodetection of said reflection light and said inner light of said photodetection unit, wherein said method comprises a correction information acquiring step where a reference light quantity is set with respect to a light quantity of said inner light, and the change in photodetection signal is detected from said photodetection unit when said light quantity of said inner light is changed, and the relation between light quantity change and phase change is acquired as correction information, and a calculating step, wherein said calculating step is to obtain the deviation of phase from said correction information based on the difference in the light quantity between the light quantity of said reflection light and said reference light quantity, said deviation is set as a correction value and to calculate a distance from said correction value and the result of photodetection of said reflection light and said inner light of said photodetection unit.

2. An electro-optical distance measuring method according to claim 1, wherein said calculating step changes the light quantity of said inner light and performs the calculation a plurality of times and further comprises an updating step for updating said correction information based on a first photodetection signal acquired from said photodetection unit on a first light quantity and on a second photodetection signal acquired from said photodetection unit on a second light quantity.

3. An electro-optical distance measuring method according to claim 2, wherein said first light quantity is a preset reference light quantity and said second light quantity is gradually changed.

4. An electro-optical distance measuring method according to claim 1, wherein said correction information acquiring step is executed when power is turned on to an electro-optical distance measuring device for performing electro-optical distance measurement.

5. An electro-optical distance measuring method according to claim 1, wherein said inner optical path includes a first inner optical path and a second inner optical path being different in optical length, and wherein said correction information acquiring step is to acquire said correction information according to a first inner light passing via said first inner optical path and to a second inner light passing via said second inner optical path.

6. An electro-optical distance measuring method according to claim 1, wherein said inner optical path includes a first inner optical path and a second inner optical path being different in optical length, and wherein said calculating step comprises a calculating prior to correction step for calculating a distance prior to correction based on said reflection light and based on a first inner light passing via said first inner optical path or based on a second inner light passing via said second inner optical path, and an updating step for updating said correction information based on said first inner light and said second inner light.

7. An electro-optical distance measuring method according to claim 5 or 6, wherein said first inner light is set to a reference light quantity, and the light quantity of said second inner light is gradually changed.

8. An electro-optical distance measuring method according to claim 5 or 6, wherein said second inner optical path has an optical fiber of a predetermined length.

9. An electro-optical distance measuring method according to claim 6, wherein said calculating step further comprises a preliminary measurement step for measuring a distance to the object to be measured only by said reflection light, and a selecting step for selecting the calculation of a distance according to which of said first inner light or said second inner light based on the result obtained in said preliminary measurement step.

10. An electro-optical distance measuring device, comprising a light source, a photodetection unit, an outer optical path for guiding a light from said light source reflected by an object to be measured toward said photodetection unit as a reflection light, an inner optical path for guiding a light from said light source toward said photodetection unit as an inner light, an inner light quantity changing unit for changing light quantity of said inner light, and a control unit including an arithmetic unit for calculating a distance to said object to be measured according to a photodetection signal from said photodetection unit, wherein said control unit receives said inner light by said photodetection unit while changing the light quantity of said inner light by said inner light quantity changing unit and acquires the relation between a change in light quantity and a change in phase of a photodetection signal from said photodetection unit as a correction information.

11. An electro-optical distance measuring device according to claim 10, wherein said control unit comprises a storage unit for storing said correction information, and wherein said arithmetic unit sets a reference light quantity with respect to a light quantity of an inner light, obtains a deviation of phase from said correction information based on the difference in light quantity between the light quantity of said reflection light and said reference light quantity, and sets said deviation as the correction value, calculates a distance based on a photodetection signal of said reflection light, based on a photodetection signal of said inner light, and based on said correction value.

12. An electro-optical distance measuring device according to claim 10, wherein said inner optical path has a first inner optical path and a second inner optical path being different in optical length, wherein said inner light quantity changing unit is provided on one of said first inner optical path or said second inner optical path, and wherein said control unit acquires said correction information based on a signal of a light passing via said first inner optical path and said second inner optical path among the signals received by said photodetection unit.

13. An electro-optical distance measuring device according to claim 11, wherein said inner optical path has a first inner optical path and a second inner optical path being different in optical length, wherein said inner light quantity changing unit is provided on one of said first inner optical path or said second inner optical path, and wherein said control unit acquires said correction information based on a signal of a light passing via said first inner optical path and said second inner optical path among the signals received by said photodetection unit and updates said correction information stored by said updated correction information.