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Cheetah Pregius Camera with Camera Link – User Manual
4.7 Color Control
The camera provides white balance options for controlling image color under different
lighting conditions. White balance control options are Off, Once, Auto, Manual, Indoor
3200K, and Outdoor 5600K.
4.8 Image Sensor Technology
A CMOS camera is an electronic device for converting light into an electrical signal. The
C2020, C2420, C2420Z, C4020, and C4120 cameras contains the latest Sony Pregius CMOS
(Complementary Metal-Oxide Semiconductor) image sensors with 3.45-micron square
pixels. The Pregius sensors have groundbreaking performance with sensitivity better than
many traditional Charge Coupled Device (CCD) image sensors. The sensors have extremely
low dark current and no visible fixed pattern noise, which has been the bane of traditional
CMOS image sensors.
The Sony CMOS sensor consists of a two-dimensional array of sensitive elements called
silicon photodiodes, also known as pixels. The photons falling on the CMOS surface create
photoelectrons within the pixels. 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.
When the camera reaches the desired exposure time, it shifts the charges from each pixel
photodiode onto a storage register within the pixel, reads out one row at a time, and then
digitizes each pixel at either 8, 10 or12 bits as selected by the user. Frame time, or read-
out time, is the time interval required for all the pixels to be read out of the image sensor.
While reading out the image from the storage registers within each pixel, the camera
captures the next image. The exposure ends just as the readout of the previous frame
ends and the next frame begins.
Unlike traditional CCD image sensors, the Sony CMOS image sensor digitizes each pixel
within a row simultaneously. This allows for more settling time, which lowers the overall
noise floor and provides improved sensitivity. The low noise floor, combined with a
reasonably large pixel charge capacity and extremely low dark current, translates into a
large dynamic range of 71 dB (12-bits) or 12 F-stops.
The sensor allows you to apply up to 48 dB of gain to the image. The first 24 dB of gain is
analog gain and some improvement in noise performance may result. The camera applies
the last 24 dB of gain digitally, which affects both signal and noise equally.
A set of color filters (red, green, and blue) arranged in a Bayer pattern over the pixels
generates color images. The starting color is Red for SONY Pregius image sensors. The
following figure shows the sensor's color response (Figure 34).
July 6, 2018
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