Imaging System Hardware
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21
Signal amplification by the PMT is controlled by adjusting the PMT gain in
the Hardware Settings dialog box. The PMT gain is related to the PMT
voltage by a calibration constant such that:
PMT gain = PMT voltage / calibration constant
The calibration constant is derived by performing the system calibration in
Hardware Diagnostics and will ensure that the scanner performance is
matched to other calibrated scanners and is self-consistent over time. For
an uncalibrated scanner the constant will be 1.000.
Mechanical
The GenePix scanner is a mechanical device. Its laser-based scanning system uses
a patented mechanical design. The GenePix scanner operates by slowly scanning
the slide in the
y
-direction, and rapidly scanning in the
x
-direction. The design of
the GenePix Personal 4100A scanner allows a dual wavelength scan of a 26 mm ×
76 mm slide at 5-
µ
m resolution in about 25 minutes.
When using such a mechanical device, one must be able to monitor the variability
in the performance of its mechanical components. The GenePix scanner has been
designed with a number of optimizations to ensure that variability in the mechanical
performance is monitored in real time during acquisition, and corrected. The
utmost attention has been given to selecting and implementing components to
create a highly reliable, high-performance instrument.
Electronic
While the optical components of the GenePix scanner are indispensable for
generating the electrical current from PMT, the electronic components are just as
important. They govern the operation of the PMT and the conversion of its analog
current signals into a digital signal that can be processed by the host computer.
Axon Instruments is the world leader in the design and construction of low-noise
amplifiers. Our amplifiers are used around the world by researchers in the
Chapter 4