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Chapter 8
Virtual Chip Mode
Fully supported by WinView/WinSpec Version 2.5 when the communication protocol is
TAXI (PCI), this feature is not supported when the protocol is USB 2.0.
Introduction
Virtual Chip mode (a WinView/32 option) is a special fast-acquisition technique that
allows frame rates in excess of 100 fps to be obtained. For the Virtual Chip selection to
be present, it is necessary that:
• the sy
stem be a 1 MHz MicroMAX,
• that the cam
era have a frame transfer chip (MicroMAX:512BFT) and,
• that the file Wxvchip.opt be present in the sam
e directory as the executable
WinView/32 program. Contact Technical Support for information regarding the
availability of Wxvchip.opt.
This method of data acquisition requires that the chip be masked as shown in Figure 58.
Masking can be achieved by
applying a mechanical or optical mask or by positioning a
bright image at the ROI against a dark background on the remainder of the array.
In operation, images are continually piped
down the CCD at extraordinarily
high frames
per second (FPS). The mini-frame transfer
region is defined by an ROI as illustrated in
Figure 58. The charge from this ROI is
shifted under the fram
e-transfer mask,
followed by a readout cycle of an ROI-sized
region under the mask. Since the ROI is far
from the serial register, the stored image is
just shifted repeatedly with the readout and
the first few images collected will not contain
useful data. After the readout period, the next
frame is shifted under the mask and another
ROI sized frame is read out. The net result is
a series of images, separated by spacer
regions, streaming up the CCD under the
mask.
Shift Register
ROI
Virtual
Chip
Frame Transfer Mask
Virtual Chip Mask
Virtual
Chip
Mask
Figure 58. Virtual Chip Functional Diagram
The table below shows the minimum exposure time per frame (msec/Frame) and the
number of frames per second (FPS) for several ROIs. Note that these numbers are
provided for the 1 MHz and the 100 kHz readout rates.
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