Rangefinder

• US 6,441,888 B1
• Filed: 03/17/2000
• Issued: 08/27/2002
• Est. Priority Date: 03/17/1999
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Azuma, Takeo, Uomori, Kenya
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): ANDREA, BRIAN K
• Application Number:
  US09/527,476
• Time in Patent Office: 893 Days
• Field of Search: 356/5.04, 356/4.01, 356/3.11, 356/4.06, 356/4.03, 356/3.02, 348/131, 348/132, 348/139, 348/455, 348/68, 354/419, 359/27, 359/32
• US Class Current: 356/4.01
• CPC Class Codes: G01S 17/08 for measuring distance only indirect measurement G01S17/46; active triangulation systems G01S17/48
• 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 7/481 Constructional features, e.g. arrangements of optical elements
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating

Abstract

A rangefinder performs highly accurate 3D measurement without being affected by any variation in intensity of projected light. A light source for projecting light onto an object is provided with a light receiver for detecting the intensity of the projected light. The intensity of a reflected part of the projected light, which has been captured by a camera as an image, is corrected using the light intensity, which has been detected by the light receiver, as correction information. And based on this corrected image, a distance calculator produces a range image. Thus, even if the intensity of the projected light has changed, a corresponding variation in intensity of the reflected light image can be compensated for.

Claims

1. A rangefinder comprising:

a light source for projecting a set of light patterns onto an object, an intensity ratio of the projected light patterns being monotonously increasing or decreasing on the object at least from place to place;

a camera for capturing a pair of images of the object by using parts of the projected light patterns, the parts having been reflected from the object; and

a three-dimensional information generator for generating three-dimensional information of the object from the reflected light images captured by the camera,

wherein the three-dimensional information generator includes a light intensity corrector, which corrects intensities of the reflected light images according to correction information representing intensities of the projected light patterns, and generates the three-dimensional using a pair of images that have been by the light intensity corrector.

2. The rangefinder of claim 1, wherein the light source projects multiple light beams with mutually different projection patterns, and

wherein the light intensity corrector corrects respective intensities of reflected light images corresponding to the projected beams, and

wherein the three-dimensional information generator generates the three-dimensional information based on a ratio of intensities of the reflected light images that have been corrected by the light intensity corrector.

3. The rangefinder of claim 1, further comprising a light receiver for detecting an intensity of the light that has been projected from the light source and outputting the intensity as the correction information.

4. The rangefinder of claim 1, wherein the light intensity corrector uses, as the correction information, brightness in a predetermined part of the image captured by the camera.

5. The rangefinder of claim 1, wherein the light intensity corrector performs offset processing on the reflected light image by subtracting black level components from image data and then makes the correction.

6. A rangefinder comprising:

a light source for projecting a set of light patterns onto an object, an intensity ratio of the projected light patterns being monotonously increasing or decreasing depending on a direction in which the light has been projected;

a camera for capturing a pair of images of the object by using parts of the projected light patterns, the parts having been reflected from the object; and

a three-dimensional information generator for generating three-dimensional information of the object from the reflected light images captured by the camera,

wherein the three-dimensional information generator includes multiple lookup tables, each describing a correspondence between the intensity ratio and the direction in which the light has been projected, selects at least one of the lookup tables for each pixel location in the images captured by the camera and generates the three-dimensional information by reference to the lookup table(s) selected.

7. A rangefinder comprising:

a light source for projecting light onto an object such that a characteristic of the projected light monotonously varies depending on a direction in which the light has been projected;

a camera for capturing an image of the object by using part of the projected light, the part having been reflected from the object; and

a three-dimensional information generator for generating three-dimensional information of the object from the reflected light image captured by the camera,

wherein the three-dimensional information generator includes multiple lookup tables, each describing a correspondence between the characteristic of the reflected light and the direction in which the light has been projected, selects at least one of the lookup tables for each pixel location in the image captured by the camera and generates the three-dimensional information by reference to the lookup table(s) selected,

wherein the lookup tables are provided for at least some epipolar lines in the image captured by the camera.

8. The rangefinder of claim 7, wherein the three-dimensional information generator newly makes a lookup table for pixels on one of the epipolar lines that is associated with none of the lookup tables by performing interpolation on at least two of the existent lookup tables associated with corresponding ones of the epipolar lines near the epipolar line on target.

9. The rangefinder of claim 7, wherein the light source and the camera are placed such that a line connecting the light source and the camera together matches an X-axis of a world coordinate system and is parallel to an x-axis of a camera coordinate system.