Television – Stereoscopic – Picture signal generator
Reexamination Certificate
1998-12-04
2002-06-25
Le, Vu (Department: 2613)
Television
Stereoscopic
Picture signal generator
Reexamination Certificate
active
06411327
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to a stereo camera system for obtaining a stereo image of an object to measure distance between the stereo camera system and the object using those, and more particularly, to the stereo camera system constructed to obtain the stereo image by a camera. The present invention also relates to a distance measurement system and a distance measurement method for measuring distance between the stereo camera system and an object using disparity of a stereo image of the object.
BACKGROUND ART
Disparity of a stereo image on a computer vision can be used in measuring distance between an object and a camera that obtains the stereo image by photographing the object. Disparity means distance between two homologous points on two images of an object, that is, distance between a point on a first image of a pair of stereo images and a corresponding point on a second image of the stereo images.
A conventional stereo camera system
40
used in distance measurement consists of two charge coupled device cameras (CCD camera)
41
and
42
as showed in FIG.
8
. The stereo image shown in
FIG. 9
is obtained as follows; one of the stereo images is obtained by photographing an object using a first camera
41
, and the other is obtained by photographing the object using a second camera
42
. A point
43
on the object corresponds to both a first homologous point
47
on a first image
45
and a second homologous point
48
on a second image
46
. The distance between the point
43
of the object and a stereo camera system
40
is in a functional relationship with the disparity of the stereo image, that is, the distance between the first homologous point
47
and the second homologous point
48
. Still, the focal length and other intrinsic parameters of each camera
41
or
42
can affect the distance between the point
43
of the object and the stereo camera system
40
. Furthermore, differences between intensities of the first image
45
and the second image
46
owing to a small range of variation in the irises of the first and second cameras
41
and
42
results in not only taking much time to detect the homologous points
47
and
48
but also deteriorating reliability of such detection. Meanwhile, the method for obtaining the first image
45
by exposure using the first camera
41
, and then obtaining the second image
46
by another exposure using the second camera
42
can not be applied in the dynamic situation if the object and/or the stereo camera system
40
is moved.
In consideration of the above defects of the stereo camera system, there were proposed some kinds of stereo camera systems to obtain a stereo image using only a camera, as follows.
In a paper of Y. Nishimoto and Y. Shirai which is entitled “A feature-based stereo model using small disparities” and published in Proceedings in Computer Vision and Pattern Recognition, pp. 192-196, 1987, a stereo camera system as shown in
FIG. 10
is proposed. The stereo camera system
50
comprises a camera
51
and a rotary glass plate
52
arranged at a desirable distance from the front side of the lens of the camera
51
. The rotary glass plate
52
swings between a first rotated position represented by a solid line and a second rotated position represented by a dotted line. As the glass plate
52
swings between the first rotated position and the second rotated position when the stereo camera system
50
is fixed, the optical axis of the lens of the camera
51
is moved slightly. A stereo image is obtained as follows. One of the stereo images is obtained by photographing an object by an exposure using the camera
51
with the glass plate
52
positioned at the first rotated position, and the other stereo image is obtained by photographing the object by another exposure using the camera
51
with the glass plate
52
positioned at the second rotated position. Since the range of disparity of the stereo image obtained by the stereo camera system
50
is very narrow, it is difficult to measure distance between the object and the stereo camera system
50
precisely. Furthermore, the stereo camera system
50
can not be applied in a dynamic situation due to the two different exposure times as is the in the aforementioned stereo camera system
40
.
In a paper of W. Teoh and X. D. Zhang which is entitled “An inexpensive stereoscopic vision system for robots,” published in Int. Conf. Robotics, pp. 186-189, 1984, another stereo camera system as shown in
FIG. 11
is proposed. The stereo camera system
60
comprises a camera
61
, a rotary glass plate
62
arranged at a desirable distance from the front side of the lens of the camera
61
and two fixed glass plates
63
and
64
disposed at both sides of the rotary glass plate
62
. The stereo camera system
60
operates as the aforementioned stereo camera system
50
does except that range of disparity of the stereo image obtained by the stereo camera system
60
is broader than that by the stereo camera system
50
. Accordingly, the stereo camera system
60
can not be applied at a dynamic situation due to the two different exposure times as in the aforementioned stereo camera system
40
.
In a paper of A. Goshtasby and W. A. Gruver entitled “Design of a Single-Lens Stereo camera system” and published in Pattern Recognition, vol. 26, pp. 923-936, 1993, still another stereo camera system, as shown in
FIG. 12
, is proposed. The stereo camera system
70
comprises a camera
71
and two reflectors
72
and
73
disposed in two planes crossed with each other so that the two reflectors
72
and
73
abut against each other at their sides. The two reflectors
72
and
73
are oppositely inclined so that their specular surfaces obliquely face an object. The camera
71
is disposed to simultaneously photograph two images reflected by the specular surfaces of the two reflectors
72
and
73
. Since the stereo camera system
70
photographs reflected images, that is, reversed images, any picture obtained by the stereo camera system
70
is object to an image translation process. Brightness of each image of the picture is affected by an incidence angle of a prevailing source of light to each reflector
72
or
73
because of mutual reflection between the two reflectors
72
and
73
, whereby degrees of brightness of two images in the picture are different although they are obtained at a single exposure time.
SUMMARY OF INVENTION
Therefore, the present invention is aimed to make a stereo camera system for providing a frame of picture having a stereo image of an object to be constructed by only a camera.
The present invention is also aimed to provide the stereo camera system for providing a frame of picture having a stereo image by a single exposure in a dynamic situation while all images of the picture have an equivalent brightness.
In order to accomplish the above mentioned aims, this invention provides a stereo camera system for providing a frame of picture having a stereo image of an object used in distance measurement between the stereo camera system and the object. The stereo camera system comprises a camera and a prism arranged at a desirable distance from the front side of the lens of the camera.
The prism may comprise a delta shaped biprism having a base, a first incline and a second incline, in which the first incline and the second incline obliquely face the lens of the camera.
The prism may comprise a triagonal pyramid shaped triprism having a base and three inclines, in which the three inclines obliquely face the lens of the camera.
The invention also provides a system for measuring distance between a stereo camera system and an object using disparity of a stereo image of the object obtained by the stereo camera system and the object, in which the stereo camera system comprises a camera and a prism arranged at a desirable distance from the front side of the lens of the camera. The distance measurement system comprises means for obtaining a frame of picture comprising the stereo image by a single shot using said stereo camera system; means for de
Kweon In So
Lee Doo Hyun
Graybeal Jackson Haley LLP
Korea Advanced Institute Science and Technology
Le Vu
LandOfFree
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