SOYO STH-DCAM user manual Hardware Overview, Hardware Schematic, Color and Monochrome, Frame Rates

STH-DCAM USER’S MANUAL 2001 VIDERE DESIGN

3 Hardware Overview

Figure 3-1shows the hardware configuration of the STH-DCAM.

The imager module has a milled Delrin frame that rigidly holds two Sony HAD CCD color imagers, separated by a fixed distance of 9 cm. Lens mounts are attached to the frame, and standard miniature lenses are screwed into these holders. There is an IR curoff filter, with a knee at approximately 700 nm, permanently mounted inside the lens holder. See Section 4 for appropriate lens characteristics.

There is a IEEE 1394 port on the left side of the device. The cable carries the data and signals for both imagers. Internally, the imagers are synchronized so that they are exposed at the same time, a requirement for stereo processing whenever there is any motion (including camera motion).

Typically, the cable is plugged into the host computer IEEE 1394 card. Power for the STH-DCAM is supplied from the card, or through a separate power supply that plugs into the power supply port of the device (7-40 VDC).

There are no user-settable switches on the STH-DCAM.

1394 cables

Right miniature

lensLeft miniature lens

Figure 3-1. Physical layout of the STH-DCAM stereo head.

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3.1Hardware Schematic

Figure 3-2shows the design of the internal hardware of the STH-DCAM. In the stereo imager module, two Sony CCD imagers, each of size 648x486 pixels, digitize incoming light into a digital stream. A full frame is captured at once, and then read out line by line. The imagers operate in progressive mode only, that is, each line is output in succession from the full frame.

The imagers are synchronized to a common clock, so that the corresponding pixels from each imager are output at the same time. Each imager sends out its own video stream, on a separate IEEE 1394 cable. There are two such cables coming out of the STH-DCAM module. Each video stream has a maximum rate of 200 Mbps; the whole IEEE 1394 bus runs at 400 Mbps.

Each imager is supplied with power from its cable. In order to synchronize correctly, power must be applied to the imagers at the same time. Typically, the two cables are connected to a small 3-port IEEE 1394 hub, which is then connected to the host IEEE 1394 port.

3.2Color and Monochrome

The Sony CCDs are color imagers, with a standard Bayer color pattern. Processing in the STH-DCAM can produce either a color or monochrome output from the imagers. Monochrome output is 1 byte/pixel, and color outputs are either 2 or 3 bytes/pixel, depending on the format. If color isn’t necessary, monochrome output should be selected, to save on movement of data.

3.3Frame Rates

The IEEE 1394 interface supports a maximum rate of 200 Mbps on each imager. The maximum frame rates depend on whether monochrome or color output is used. Frame rates up to 30 Hz at 640x480 are supported. See Table 3-1below for a complete list of frame rates.