CHEETAH Hardware User’s Manual
Imperx, Inc.
Rev 1.7
6421 Congress Ave.
8/26/2016
Boca Raton, FL 33487
+1 (561) 989-0006
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1.3.1.1 Global Shutter Description
All Cheetah cameras support global shutter readout mode. In Global Shutter (GS)
mode every pixel starts and stops integration at the same time. This mode is excellent
for clean capture of moving scenes without the need for a mechanical shutter. When
global shutter mode is used, all pixel data is stored in light shielded regions within
each pixel and held there until readout. (Figure 1.0)
Figure 1:
Global Shutter Description
1.3.1.2 A/D architecture and frame rate controls
The C5180, C4181, C4180 and C3880 image sensors multiplex 80 (C5180), 64
(C4181 and C4180) and 60 (C3880) columns respectively into an array of 64 A/D
converters. The camera takes care of all the details of re-ordering the lines within
frame grabber memory. Unlike a CCD where digitization is performed within one
pixel time, these cameras perform digitize at 1/64
th
the pixel rate (64 A/D converters)
and the digitization has a depth of 10-bits
The image sensor provides up to thirty-two LVDS outputs and the time to readout one
line from the image sensor is much less than the time necessary to output the data
using Camera Link. The camera compensates for this mismatch in data output rate
versus data capture rate using two methods: a variable pixel clock for line readout and
the ability to add 1 micro-second of delay (row overhead) time at the end of each line
output by the camera. Slowing down the pixel line clock and adding delay (dead time)
at the end of each line allow the Camera Link grabber to keep pace with the camera
output.
