Optics: measuring and testing – Angle measuring or angular axial alignment – Apex of angle at observing or detecting station
Reexamination Certificate
1999-02-03
2001-03-20
Buczinski, Stephen C. (Department: 3662)
Optics: measuring and testing
Angle measuring or angular axial alignment
Apex of angle at observing or detecting station
C356S141500, C356S141400, C250S206200
Reexamination Certificate
active
06204916
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a three dimensional information measurement method and apparatus for measuring three dimensional information on an object over a wide angular range, and for inputting the measured information, and more particularly to a three dimensional information measurement method and apparatus capable of making measurements over an angular range, for example, of 180 or 270 degrees, or from all directions through 360 degrees.
2. Description of Related Art
Recent years have seen rapid advances in virtual reality and mobile robot technologies. In these fields, it is required to input three dimensional information of objects that are to be captured for imaging or detection, and with this requirement, interest in and demand for three dimensional information measurement apparatuses have been increasing.
In the case of a mobile robot, when the robot moves, it is necessary to constantly monitor the surroundings for obstructions in order to avoid collisions, and to steer away from any obstructions. Whether an object located in the surrounding space is an obstruction or not is judged by measuring the distance to the object by a three dimensional information measurement apparatus mounted on the mobile robot, and by checking if the distance has decreased below a predetermined value. Such judgement must be made in real time, requiring that the distance in each direction be measured at high speed around the entire circumference.
In a known technique for measuring the distances to surrounding objects over a wide angular range, it has been practiced to rotate the camera part of the distance measurement apparatus while shooting the surroundings. If the rotational speed is slow, the time difference between the timing of the camera's line of sight capturing an object in one direction and the timing of capturing an object in the next direction increases, resulting in slow monitoring. If the rotational speed is increased, the camera's line of sight quickly scans the surroundings, so that the time difference is reduced and quick monitoring can be achieved. This, however, increases the size of the mechanism provided for that purpose, and also, rotational noise becomes a problem.
There has been proposed an omnidirectional distance detection apparatus in which, instead of rotating the camera part, two mirrors for projecting and receiving reference light for distance measuring are assembled in one unit and are rotated together (Japanese Patent Unexamined Publication No. 7-191142). However, in the omnidirectional distance detection apparatus disclosed in the above patent publication, the mirrors are housed in a cylindrically shaped casing having a transparent circumferential wall and are rotated about the axis of the casing to irradiate surrounding objects with reference light and to receive its reflected light for distance measuring. The mirrors are driven by a motor via a rotor, and the rotor, motor, etc. are all housed in the casing, providing the effect of reducing the rotational noise. The construction is complex compared with the method of rotating the camera's line of sight. Since the two mirrors for projecting and receiving the reference light are rotated together, the apparatus size increases, and the stability of the apparatus decreases when the rotational speed is increased.
OBJECTS AND SUMMARY OF THE INVENTION
The present invention has been devised in view of the above problems, and it is an object of the invention to provide a three dimensional information measurement method and apparatus capable of measuring three dimensional information of objects located in a space extending a wide angular range, at high speed and with high stability using a relatively simple configuration.
According to the invention, there is provided a three dimensional information measurement method for measuring three dimensional information on a target placed in a space surrounding a center axis of a rotator type mirror by using the rotator type mirror in combination with an imaging apparatus disposed with its light receiving axis aligned with the center axis of the rotator type mirror, comprising: scanning the target by projecting reference light from a position on the center axis; and obtaining the three dimensional information of the target, based on a physical quantity corresponding to the projection angle of the reference light and on a physical quantity corresponding to the position of a projected image obtained when the reference light reflected from the target is captured by the imaging apparatus via the rotator type mirror.
According to this invention, since driving in the main scan direction is rendered unnecessary, higher speed and higher stability can be achieved.
According to another aspect of the invention, there is provided a three dimensional information measurement apparatus, having a rotator type mirror and an imaging apparatus disposed with its light receiving axis aligned with a center axis of the rotator type mirror, for measuring three dimensional information on a target placed in a space surrounding the center axis, comprising: reference light projection means for projecting reference light in the form of a beam; main scanning means for performing a main scan by deflecting the reference light in such a manner that the direction of projection of the reference light changes in a circumferential direction centered about the center axis; sub scanning means for performing a sub scan by deflecting the reference light in such a manner that the direction of projection of the reference light changes in a direction parallel to the center axis; and three dimensional information computing means for obtaining the three dimensional information of the target, based on a physical quantity corresponding to a projection angle representing the direction of projection of the reference light in the sub scan, and on a physical quantity corresponding to the position of a projected image obtained by the imaging apparatus and representing the reference light reflected from the target.
According to still another aspect of the invention, there is provided a three dimensional information measurement apparatus, having a rotator type mirror and an imaging apparatus disposed with its light receiving axis aligned with a center axis of the rotator type mirror, for measuring three dimensional information on a target placed in a space surrounding the center axis, comprising: radiating reference light projection means, provided on the center axis, for projecting radiating reference light spreading in the form of a conical surface; sub scanning means for performing a sub scan by deflecting the reference light in such a manner as to change the projection angle of the reference light; and three dimensional information computing means for obtaining the three dimensional information of the target, based on a physical quantity corresponding to the projection angle representing the direction of projection of the reference light in the sub scan, and on a physical quantity corresponding to the position of a projected image obtained by the imaging apparatus and representing the reference light reflected from the target.
For the physical quantity corresponding to the projection angle, the projection angle itself or the physical quantity associated with the projection angle is used, such as the elapsed time from the start of the sub scan or the amount of movement of the light source, mirror, slit, or the like. For the physical quantity corresponding to the position of the projected image, the distance of the position of the projected image from a reference position, or the direction opposing the pixel on which the projected image is projected, is used.
In this specification, the term “on the center axis” in the phrase “projecting reference light from a position on the center axis” includes points on the center axis and its surroundings.
REFERENCES:
patent: 3897151 (1975-07-01), Lecroy
patent: 4457621 (1984-07-01), Harris et al.
patent: 479
Norita Toshio
Yagi Fumiya
Buczinski Stephen C.
Burns Doane , Swecker, Mathis LLP
Minolta Co. , Ltd.
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