SOYO STH-DCAM - Manual (Page 11)

STH-DCAM U SER ’ S M ANUAL 2001 V IDERE D ESIGN
Both imagers are treated in exactly the same manner. It is not possible to
set a different exposure or gain on each imager.
Figure 6-2 Frame size control in the main capture window.
Digitization control can operate in either manual or automatic mode. Refer
to Figure 6-1 for the controls in the video capture program.
In manual mode, the user program sets the exposure and gain. The
exposure and gain are based on a 0 to 100 scale. Here are some tips for
setting exposure and gain.
• In general, keep the gain as low as possible, since it introduces
additional noise into the system. Use it only if the exposure is set
to maximum, or if the exposure must be kept low to minimize
motion blur.
• Adjust the manual iris of the lens to as small an opening as
possible for your application, without having to use gain. This
will increase the depth of field and give better optical performance.
6.3 Subsampling
In many applications it is not necessary to work with the the full 640x320
pixel array. The CCD image processors are capable of reducing the amount
of information contained in the digital video stream sent back to the host.
They do this by averaging the values from neighboring pixels, giving a
higher signal-to-noise ration. This technique is called binning. Binning
occurs automatically when a smaller frame size is selected.
Figure 6-2 shows the frame size control on the video capture application.
The two frame sizes allowed are 640x480 (full frame) and 320x240 (x2
binning).
6.4 Subwindowing
The STH-DCAMs do not support subwindowing..
6.5 Frame Rates
Frame rates from the STH-DCAM depend on the frame size and color
mode. Frame rates can be set under program control with the SetRate()
function; see the Small Vision System User’s Manual. For the smallv
and smallvcap applications, frame rates are set at 30 Hz.
Frame Rates, Hz Monochrome Color
320x240 30, 15, 7.5 30, 15, 7.5
640x480 30, 15, 7.5 30, 15, 7.5
Table 6-1 Allowable frame rates for the STH-DCAM in different
modes.
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