Distance measurement apparatus and distance measurement method

Patent metadata

Field	Value
Publication number	US-2018372484-A1
Application number	US-201716062069-A
Country	US
Kind code	A1
Filing date	Jan 6, 2017
Priority date	Mar 22, 2016
Publication date	Dec 27, 2018
Grant date	—

Abstract

A distance measurement apparatus includes: a control unit that makes an imaging unit acquire a plurality of first captured images corresponding to light patterns when making an optical system set the focal length to a first focal length, and that makes the imaging unit acquire second captured images corresponding to the light patterns when making the optical system set the focal length to a second focal length; a first distance measurement unit that determines presence or absence of an image blur and acquires a first distance to a subject from an image blur index value indicating an extent of the image blur; a second distance measurement unit that acquires a second distance to the subject based on triangulation; and a measurement result synthesis unit that outputs the first distance for a pixel with the image blur and that outputs the second distance for a pixel with no image blur.

First claim

1 . A distance measurement apparatus comprising:
a projection unit that projects a plurality of light patterns to a subject; an optical system including a mechanism that changes a focal length; an imaging unit that photographs the subject via the optical system; a control unit that makes the projection unit project the plurality of light patterns sequentially and makes the imaging unit acquire a plurality of first captured images corresponding to the plurality of light patterns when making the optical system set the focal length to a first focal length, and that makes the projection unit project the plurality of light patterns sequentially and makes the imaging unit acquire a plurality of second captured images corresponding to the plurality of light patterns when making the optical system set the focal length to a second focal length which is longer than the first focal length; a first distance measurement unit that determines presence or absence of an image blur per pixel from the plurality of first captured images and the plurality of second captured images and acquires a first distance, which is a distance to the subject, per pixel, from an image blur index value indicating an extent of the image blur; a second distance measurement unit that acquires a second distance, which is a distance to the subject, per pixel, based on triangulation from the plurality of first captured images and the plurality of second captured images; and a measurement result synthesis unit that outputs the first distance for a pixel determined by the first distance measurement unit to be a pixel with the image blur and that outputs the second distance for a pixel determined to be a pixel with no image blur.

2 . The distance measurement apparatus according to claim 1 , wherein the plurality of light patterns projected by the projection unit include:
a first light pattern including a first bright area and a first dark area which are alternately arranged regularly in one direction and have a same width in a direction of the arrangement, and a second light pattern including a second dark area and a second bright area which are reverse of the first bright area and the first dark area in the first light pattern.

3 . The distance measurement apparatus according to claim 2 , wherein the image blur index value is a difference between a maximum value and a minimum value of a normalized difference value obtained by normalizing a difference value between a luminance value of a target pixel in the first captured image obtained when the first light pattern is projected and a luminance value of the target pixel in the second captured image obtained when the second light pattern is projected.

4 . The distance measurement apparatus according to claim 1 ,
wherein the second distance measurement unit performs a distance measurement based on triangulation by using a near-focal-position image data acquired by photographing when the focal length is set to the first focal length and a far-focal-position image data acquired by photographing when the focal length is set to the second focal length, and the measurement result synthesis unit outputs, regarding a portion on which the first distance measurement unit determines that one image of the near-focal-position image data and the far-focal-position image data have no image blur and another image has the image blur, a distance measurement result of the image with no image blur, the distance measurement result being obtained by the second distance measurement unit, and outputs, regarding a portion on which the first distance measurement unit determines that neither the near-focal-position image data nor the far-focal-position image data have the image blur, another distance measurement result of one image with a larger image blur index value indicating an image blur amount, the another distance measurement result being obtained by the second distance measurement unit.

5 . The distance measurement apparatus according to any one of claim 1 , further comprising a camera arm unit that changes positions of the projection unit, the optical system and the imaging unit, and a photographing direction of the imaging unit, with respect to the subject,
wherein, after a first distance measurement is performed by the first distance measurement unit, the second distance measurement unit and the measurement result synthesis unit, intensity of the light patterns from the projection unit, and the photographing position and the photographing direction of the imaging unit are changed, and then second and subsequent distance measurements are performed by the first distance measurement unit, the second distance measurement unit and the measurement result synthesis unit, and the measurement result synthesis unit synthesizes results obtained by performing of the first and second and subsequent distance measurements and outputs the synthesized results.

6 . The distance measurement apparatus according to claim 5 , wherein distance measurement results on an upper side and a lower side of an error occurrence area, in which an error occurs in the first distance measurement by the first distance measurement unit, the second distance measurement unit and the measurement result synthesis unit, are compared with each other, distance measurement results on a left side and a right side of the error occurrence area are compared with each other, and, based on comparison results of the distance measurement results, the camera arm unit moves the projection unit, the optical system, and the imaging unit and changes the photographing direction of the imaging unit.

7 . The distance measurement apparatus according to claim 5 ,
wherein the measurement result synthesis unit performs processing of plotting a point indicated by a subject distance measured before the projection unit, the optical system and the imaging unit are moved, as a point indicating a measurement distance to be outputted, on a three-dimensional space, and in subject distances measured by moving the projection unit, the optical system and the imaging unit and by changing the photographing direction of the imaging unit, if a point indicated by a subject distance measured before the imaging unit is moved does not exist on a line connecting a previously plotted point and the imaging unit, additional plotting is performed, and if a point indicated by a subject distance measured before the imaging unit is moved exists on a line connecting a previously plotted point and the imaging unit, additional plotting is not performed.

8 . A distance measurement method performed by an apparatus including a projection unit that projects a plurality of light patterns to a subject, an optical system including a mechanism that changes a focal length, and an imaging unit that photographs the subject via the optical system, the distance measurement method comprising:
a step of making the projection unit project the plurality of light patterns sequentially and making the imaging unit acquire a plurality of first captured images corresponding to the plurality of light patterns when the focal length of the optical system is set to a first focal length; a step of making the projection unit project the plurality of light patterns sequentially and making the imaging unit acquire a plurality of second captured images corresponding to the plurality of light patterns when the focal length of the optical system is set to a second focal length longer than the first focal length; a step of determining presence or absence of an image blur per pixel from the plurality of first captured images and the plurality of second captured images and acquiring a first distance, which is a distance to the subject, per pixel, from an image blur index value indicating a

Assignees

• Mitsubishi Electric Corp

Inventors

• Fujita Takeo
• Yamashita Koichi
• Matoba Narihiro

Classifications

• G01B11/2513 Primary

  with several lines being projected in more than one direction, e.g. grids, patterns · CPC title

• G01C3/10

  using a parallactic triangle with variable angles and a base of fixed length in the observation station, e.g. in the instrument · CPC title

• G01B11/25 Primary

  by projecting a pattern, e.g. {one or more lines,} moiré fringes on the object (G01B11/255 takes precedence {; image analysis for depth or shape recovery G06T7/50}) · CPC title

• G06T7/571

  from focus · CPC title

• G06T7/521

  from laser ranging, e.g. using interferometry; from the projection of structured light · CPC title