Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION:
method and apparatus for generating stereo imagery
NAME ( S ) OF INVENTOR ( S )
Anup Basu
FIELD OF THE INVENTION
The present invention relates to a method and an apparatus
for generating stereo imagery
BACKGROUND OF THE INVENTION
Most methods and apparatus for generating stereo imagery
use independent cameras rotating around vertical axes. These
systems have inherent drawbacks. One drawback lies in the
capability of acquiring a hemispherical field-of-view without
the two stereo cameras getting in the way of one another.
Another drawback lies in the need for registration of images
captured by the CCD at different rotation positions.
SUMMARY OF THE INVENTION
What is required is an alternative method and apparatus
for generating stereo imagery.
According to one aspect of the present invention there is
provided a method for generating stereo imagery. A first step
involves positioning two imaging devices on a bar in a fixed
spaced apart relation. The second step involves incrementally
rotating the bar.
According to another aspect of the present invention there
is provided an apparatus for generating stereo imagery which
includes a bar and means for supporting the bar while allowing
it to rotate freely. Two imaging devices are attached to the
bar in spaced apart relation. A high precision rotation device
controls rotation of the bar. A driver is provided for
electronically controlling the rotation device. A computer is
provided along with means for bi-directional communication
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between the driver and the computer, whereby rotational
adjustments are made in real time.
With the method and apparatus, as described above, the two
stereo cameras do not get in the way of one another and there
is no need for registration of images captured at different
rotation positions.
Although beneficial results may be obtained through the
use of the invention, as described above, in some applications
it is necessary to create a very high resolution image of a
static scene. Artistic examples of such applications include
images at historic sites such as holy sites, monuments, art
galleries, and museums. A scene from the interior of a museum
usually contains regions where brighter colors are more
prominent, regions where darker colors are more prominent,
regions with high illumination (for example, sun shining
through a window), regions with low illumination etc..
Industrial examples of such applications include images of
interiors of tunnels and pipelines as part of a program for
maintenance and repair of such structures. It is preferred
that the image provide 3-dimensional information in a scene in
order to have depth information. Depth information is useful
for observing artifacts (such as statues) and structures (such
as pillars and columns) that are not 2-dimensional. Depth
information is also useful for detecting structural defects and
cracks in tunnels, pipelines, and other industrial structures.
Even more beneficial results may, therefore, be obtained
3 0 when the imaging devices include an analog to digital converter
and means are provided for bi-directional communication between
the imaging devices and the computer, whereby adjustments are
made by the computer to the parameters of the analog to digital
converter in real time.
Even more beneficial results may, therefore, be obtained
when the imaging devices include a linear charge coupled device
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sensor and means are provided for bi-directional communication
between the imaging devices and the computer, whereby
adjustments are made by the computer to the sampling speed of
the linear charge coupled device sensor in real time.
The apparatus, described above, is able to sense when
variations in lighting conditions exist and adaptively adjust
imaging parameters such as gain to reduce or eliminate
degradation in the quality of a digital image resulting from
color saturation variations and adjust the sampling rate of the
CCD to scan faster in brighter regions or slower in darker
regions in order to capture dark and bright regions in a scene
with equal clarity.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the invention will become more
apparent from the following description in which reference is
made to the appended drawings, wherein:
FIGURE 1 is a block diagram of a high resolution stereo
camera constructed in accordance with the teachings of the
present invention.
FIGURE 2 is a block diagram of mechanical components of
the high resolution stereo camera illustrated in FIGURE 1,
FIGURE 3 is a block diagram of charge coupled device (CCD)
and analog to digital (A/D) components of the high resolution
stereo camera illustrated in FIGURE 1.
FIGURE 4 is a block diagram of a high speed communication
board of the high resolution stereo camera illustrated in
FIGURE 1.
FIGURE 5 is a block diagram illustrating bi-directional
communication between the components illustrated in FIGURE 3
and a computer via the communications board illustrated in
FIGURE 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred embodiment, a high resolution stereo camera
generally identified by reference numeral 10, will now be
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described with reference to FIGURES 1 through 5.
Referring now to FIGURE 1, a stepper motor 1 coupled with
a planetary gear head 2 is used to accurately rotate a
horizontal bar 3. The stepper motor 1 is driven by a stepper
motor driver 4. The horizontal bar 3 rests on two sets of
bearings 5 which allow the bar 3 to rotate smoothly while being
held firmly in place. Two imaging systems 6 which use a
combination of high resolution linear CCD and A/D converters
with high precision for each of the red, green, and blue pixels
are mounted on the horizontal bar 3. The two imaging systems
6 are connected to the two high speed bi-directional
communication boards 7. The bi-directional communication
boards are also connected to two IEEE 1284 compatible parallel
ports on a computer 8. One of the bi-directional communication
boards 7 is also connected to the stepper motor driver 4 to
allow the computer 8 to control the stepper motor 1 via the
communication board 7.
Referring now to FIGURE 2, the mechanical devices in the
system is shown in greater detail. The shaft 10 of the gear
head 2 is connected to the horizontal bar 3 using a connector
9. The length of the horizontal bar 3 can be selected
depending on the depth at which clarity based on stereo imaging
is required; the bar 3 has to be longer in order to allow
greater distance between the imaging systems 6 in Figure 1.
Greater distance between the imaging systems 6 in Figure 1
allow depth information to be accurately recovered at greater
distances using stereo imaging.
Referring now to FIGURE 3, the electronic components of
the imaging systems 6 in Figure 1 is described. The imaging
systems 6 consist of a printed circuit board (PCB) containing
a very high resolution linear CCD 12; a PCB containing an A/D
converter 13 and a PLD 14; and a PCB for supplying DC power at
various voltages using DC-to-DC converters 15. The PLD 14
controls sampling signals from the CCD 12, as well as several
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functions of the A/D converter 13.
Referring now to FIGURE 4, the communication board 7 is
described in greater detail. The main components of the
5 communication board 7 are a PLD 16 and two dual-port RAMs
(random access memories) 17. The dual-port RAMS 17 are used
for bi-directional communication of data and image information
between the computer 8 and the imaging systems 6 as well as
between the computer 8 and the stepper motor driver 4. The PLD
16 controls handshakes with the computer 8 following the IEEE
1284 standard. The PLD 16 is also responsible for reading and
writing into the dual-port RAMs 17 as well as directing data
from the dual-port RAMs to either the imaging systems 6 or the
stepper motor driver 4.
Referring now to FIGURE 5, the communication channels
between the computer 8 and the A/D converters 13 (in the
imaging systems) 6 via the dual-port RAMS 17 is described in
greater detail.
In operation, the computer 8 controls the rotating device
to move one step at a time to turn up to 40,000 steps per 360
degree revolution. The number of steps can be higher than
40,000 per 360 degree using a different set of stepper motor
and gear head. At each step the imaging systems 6 acquire two
high resolution linear strips of images. These images are
transmitted to the computer 8 via the communication boards 7.
The computer 8 also initializes the registers of the A/D
converters 13 via the communication boards 7. The computer 8
also adjusts various parameters of the imaging systems, such
as gain, offset, sampling speed etc., via the communication
boards 7 in real time. The invention, therefore, does not use
any on-board memory, such as, Erase Programmable Read Only
Memory (EPROM) or FLASH memory, to initialize the registers of
the imaging systems. The computer 8 can also increase the
dynamic range of the camera by sampling different regions of
the linear CCD array 12 at different clock speeds. For
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example, a bright region can be sampled with a faster clock
speed allowing a pixel of the CCD 12 to not be saturated, while
a dark region can be sampled with a slower clock speed. This
allows both bright and dark regions of a scene to be viewed
clearly in a digital picture. The advantage of this system
over existing high resolution imaging systems using independent
cameras rotating around vertical axes lies in the capability
of acquiring a hemispherical field-of-view without the two
stereo cameras getting in the way of one another. Another
advantage of this system over existing high resolution imaging
systems using rotating area CCD around vertical axes lies in
the capability of obtaining high resolution images without the
need for registration of images captured by the CCD at
different rotation positions.
In the foregoing specifications, the invention has been
described with respect to specific exemplary embodiments.
However, various modifications may be made thereto without
deviating from the broader spirit and scope of the invention
as set forth in the appended claims.
