SW-2000M-CL-65
１０
5
Operation and functions
5.1
Introduction
5.1.1
Image sensor
The SW-2000M-CL-65 is built around a high performance CMOS line scan image sensor, which
converts the light collected by each pixel into electrical charge. The amount of charge
generated in each of the individual pixels is basically directly proportional to the amount of
light they receive.
The sensor has two options to store the charge of each pixel. These are called Quantum Wells.
The smaller well can hold about 60,000 electrons (60 ke
-
), while the larger has capacity for 360
ke
-
. The larger well should be used whenever feasible as it provides the best image quality due
to higher dynamic range and better signal-to-noise ratio (SNR).
SNR is limited by the shot noise of the light itself and thus it is beneficial to collect as many
photons (light) as possible. The smaller well can be used to provide about six times higher
response to light, but with the cost of lower SNR and dynamic range.
Correlated Double Sampling (CDS) is used for sampling the charge voltage and the reset level
to find the difference, which is then digitized into more than 12 bits and sent out of the sensor
for processing.
Fig.5. Sensor block diagram
e
-
PIXEL
SMALL
LARGE
VOLTAGE
VOLTAGE
CDS
A/D
12½ BITS
QUANTUM WELL
COMMAND: SENSOR
