Outdoor range finder

• US 6,331,887 B1
• Filed: 09/23/1999
• Issued: 12/18/2001
• Est. Priority Date: 02/14/1997
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Yaskawa Denki, Kyushu Electric Power Company Incorporated
• Original Assignee: Kabushiki Kaisha Yaskawa Denki, Kyushu Electric Power Company Incorporated
• Inventors: Wakisako, Hitoshi, Shiraishi, Kazunari, Maruyama, Yoshinaga, Yano, Kyoji, Nakashima, Moriyuki
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US09/355,707
• Time in Patent Office: 817 Days
• Field of Search: 356/3.01-3.16, 348/135, 348/31
• US Class Current: 356/3.03
• CPC Class Codes: G01B 11/00 Measuring arrangements characterised by the use of optical techniques
• CPC Class Codes: G01B 11/026 by measuring distance between sensor and object G01B11/0608 takes precedence
• CPC Class Codes: G01C 3/085 with electronic parallax measurement

Abstract

The present invention is a distance measuring device having a low power laser for use outdoors. The distance measuring device of the invention includes a laser emitting means that emits a pulsed laser beam to an object to be measured and an image reader that takes in irradiations images and stop period images of the object synchronously with an irradiation and stop period of the laser beam. A processing device then subtracts the stop image pixel values from the emission image pixel values to produce differential images. A minimum value image of the differential images is processed and binarized using a binary threshold to produce binary data from which a position where the laser beam is received is found. A calculation apparatus then determines a distance between the laser beam receiving position and the object based on the position where the laser beam is received.

Claims

1. An outdoor range finder for finding a distance to an object, comprising:

a laser emitting means that emits a pulse laser beam to an object to be measured;

an image reading means that takes in a plurality of images of the object synchronously with emission periods and off periods of the laser beam;

a means for producing a plurality of differential images from differences between ones of the images read during the emission periods and other ones of the images read during the off periods;

a means that detects minimum value data of corresponding pixels of said plurality of differential images;

a means that determines a binary threshold from the minimum value of the differential images;

a means that makes a binary data from the minimum value data of the differential images, and detects a position where the laser beam is received; and

means for determining a distance between said laser emitting means and said object based on the position where the laser beam is received.

2. A range finder for measuring a distance to an object, comprising:

a laser emitting a pulse laser beam to the object to irradiate the object during irradiation periods and not irradiating the object during off periods;

an image reading unit imaging the object to produce irradiated images of the object during the irradiation periods and non-irradiated images of the object during the off periods;

an image processing unit for producing differential images from pairs of ones of said irradiated images and ones of said non-irradiated images;

a detecting unit detecting a minimum value of corresponding pixels of the differential images and producing minimum value image data therefrom;

a first determining unit for determining a binary threshold from the minimum value image data;

a binarizing unit for binarizing said minimum value image data using said binary threshold and detecting a received position at which the pulse laser beam is received; and

a second determining unit for determining a distance between said laser and said object based on said received position of the laser.

3. The range finder of claim 2, wherein said image processing unit produces said differential images by subtracting said ones of said non-irradiated images from said ones of said irradiated images.

4. The range finder of claim 3, wherein said pairs are sequential pairs.

5. The range finder of claim 4, wherein said differential images include at least three differential images.

6. The range finder of claim 5, wherein:

said ones of said non-irradiated images are two of said non-irradiated images; and

said ones of said irradiated images are two of said irradiated images.

7. The range finder of claim 2, wherein said differential images include at least three differential images.

8. The range finder of claim 7, wherein:

said ones of said non-irradiated images are two of said non-irradiated images; and

said ones of said irradiated images are two of said irradiated images.

9. The range finder of claim 2, wherein:

said ones of said non-irradiated images are two of said non-irradiated images; and

said ones of said irradiated images are two of said irradiated images.

10. A range finder for measuring a distance to an object, comprising:

a laser emitting a pulse laser beam to the object to irradiate the object during irradiation periods and not irradiating the object during off periods;

an image reading unit imaging the object to produce irradiated images of the object during the irradiation periods and non-irradiated images of the object during the off periods;

an image processing unit for producing differential images from pairs of ones of said irradiated images and ones of said non-irradiated images;

a detecting unit detecting a minimum value of corresponding pixels of the differential images and producing minimum value image data therefrom;

a position determining unit for calculating a received position at which the pulse laser beam is received; and

a distance calculating unit for determining a distance between the laser and said object based on said received position of the pulse laser beam.

11. The range finder of claim 10, the position determining unit includes a binarizing unit for binarizing said minimum value image data to produce binarized minimum value image data and said position determining unit determines said received position of the pulse laser beam based on said binarized minimum value image data.

12. The range finder of claim 11, wherein said image processing unit produces said differential images by subtracting said ones of said non-irradiated images from said ones of said irradiated images.

13. The range finder of claim 12, wherein said differential images included at least three differential images.

14. The range finder of claim 13, wherein:

said ones of said non-irradiated images are two of said non-irradiated images; and

said ones of said irradiated images are two of said irradiated images.

15. The range finder of claim 10, wherein said differential images include at least three differential images.

16. The range finder of claim 15, wherein:

said ones of said non-irradiated images are two of said non-irradiated images; and

said ones of said irradiated images are two of said irradiated images.

17. The range finder of claim 10, wherein:

said ones of said non-irradiated images are two of said non-irradiated images; and

said ones of said irradiated images are two of said irradiated images.

18. The range finder of claim 10, the position determining unit includes a threshold determining unit for determining a threshold value from the minimum value image data and said position determining unit determines said received position of the pulse laser beam based on said threshold value.