User`s manual

STOC USER’S MANUAL ©2005 VIDERE DESIGN
3 Hardware Overview
Figure 3-1 shows the hardware configuration of the STOC/-C.
The imager module has a milled aluminum alloy frame that rigidly holds
two VGA imagers, separated by a fixed distance of 9 cm. Lens mounts are
an integral part of the frame, and miniature 12 mm diameter lenses are
screwed into these holders. There is an IR cutoff filter, with a knee at
approximately 680 nm, permanently mounted inside the lens holder. See
Section
6 for appropriate lens characteristics.
The interface module is mounted on the back of the stereo head. One IEEE
1394 port is placed at the back of the module; it is inset so that the IEEE
1394 plug does not stick out from the device.
A status LED indicates video imager activity. When the device is powered
and connected to an IEEE 1394 card on the host computer, it will flash
slowly during the initialization of the STOC board, for about 40 seconds.
At the end of this time, it will stay on if the device has been recognized by
the host PC. The LED will begin flashing again as soon as images are
being acquired by the host computer, at ½ the frame rate. Changing the
video modes (frame size, decimation) will cause the frame rate to change,
and this will be reflected in the LED flash rate.
There are no user-settable switches on the STOC/-C.
3.1 Hardware Schematic
Figure 3-2 shows the design of the internal hardware of the STOC/-C. In
the stereo imager module, two CMOS imagers, each of size 640x480 pixels,
digitize incoming light into a digital stream. The imagers operate in
progressive mode only, that is, each line is output in succession from the
full frame.
The maximum video rate is 12 megapixels per second from each imager,
which produces 640x480 at 30 Hz. The imagers are synchronized to a
common clock, so that the corresponding pixels from each imager are
output at precisely the same time.
The two digital streams are fed into the STOC board. There, they are first
rectified to eliminate lens distortion and mechanical misalignment. Then,
the rectified images are processed to extract disparity (range) information at
each pixel. The disparity image and the left rectified image are interlaced,
pixel by pixel, and sent to the interface board.
On the interface board, the interlaced video stream is transferred to the
IEEE 1394 interface module, which communicates to the host PC over an
IEEE 1394 digital cable. The module also accepts commands from the host
PC over the cable, and uses these commands to control imaging modes such
as exposure.
The IEEE 1394 interface module can communicate at the maximum IEEE
1394 data rate, 400 MBps. Of this, the maximum data rate for video
transfer is 32 MB/s.
3.2 Frame Formats and Rates
The IEEE 1394 interface electronics on the STOC supports a maximum rate
of 32 megapixels per second. At this rate, there is no need for large buffer
memories to hold video data on the stereo device. The STOC/-C conforms
IEEE 1394
port on back
Right
miniature
lens
Left
miniature
lens
LED
indicato
r
Figure 3-1. Physical layout of the STOC/-C stereo head.
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