Cheetah KAC Camera User Manual | Camera Link (CLF) Interface
October 1, 2019
Page
10
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135
Rev 7.2
1.2 Cheetah Specifications
1.2.1 General Information
A CMOS camera is an electronic device for converting light into an electrical signal. The
camera contains a light sensitive element CMOS (Charge Coupled Device) where an
electronic representation of the image is formed. The CMOS image sensor consists of a
two-dimensional array of sensitive elements – silicon photodiodes, also known as pixels.
The photons falling on the CMOS surface create photoelectrons within the pixels, where
the number of photoelectrons is linearly proportional to the light level. Although the
number of electrons collected in each pixel is linearly proportional to the light level and
exposure time, the number of electrons varies with the wavelength of the incident light.
1.2.1.1 Global and Rolling Operations
Cheetah C4080 and C2880 cameras support both global and rolling 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.
In Rolling Shutter (RS) mode, each line of the image sensor is captured at a slightly
different time. This can cause distortions in the image, if an object is moving very quickly
and the integration time is short with respect to the frame readout time. In rolling shutter
mode, pixels in a row are cleared of charge, allowed to integrate for the required
exposure time and then the entire line is readout. The resetting of each line ripples
through the array and each line is exposed with a slight time delay (equal to the line
readout time) relative to the previous line. In RS mode, the transistor within each pixel
used to provide global shutter capability is used to provide noise reduction.
Figure 1: Global Shutter Description.
