Princeton Instruments NIRvana-LN, User Manual, Page: 69 / 122

Chapter 7 Exposure and Signal 69
7.11 Digitization
After gain has been applied to a signal, the Analog-to-Digital Converter (ADC) converts
that analog information (i.e., continuous amplitudes,) into a digital data (i.e., quantified,
discrete steps,) that can be read, displayed, and stored by the application software. The
number of bits per pixel is based both on the hardware and the settings programmed into the
detector through the software.
REFERENCES:
For additional information, refer to Section 7.10, Readout , on
page 68.
Factors associated with digitization include the digitization rate and baseline signal.
Depending on the detector model, it may be possible to change the speed at which
digitization occurs and/or offset the baseline. These factors are discussed in the following
sections.
7.11.1 Digitization Rate
After readout, an analog signal representing the charge of each pixel is digitized. The
number of bits per pixel is based on both the hardware and the settings programmed into the
detector through the software.
7.11.2 ADC Offset (Baseline Offset)
ADC offset, also known as baseline offset, provides another way of dealing with dark
signal. By offsetting the baseline signal, much of the background is ignored during
conversion. For the NIRvana-LN, this offset is set at the factory and is not configurable.
REFERENCES:
For additional information, refer to Section 7.8, Dark Signal ,
on page 67.
During the exposure time, in addition to the signal of interest, the array collects a charge
pattern and an IR signal. The longer the exposure time and the warmer the
detector/environment, the larger and less uniform this background will appear.
CAUTION!
!
If a sudden change in the baseline signal is observed, there may
be excessive humidity in the vacuum enclosure of the detector.
Immediately turn off the controller, and if using an LN-cooled
camera, remove the liquid nitrogen.
Contact Princeton Instruments Customer Support for further
instructions. Refer to
Contact Information on page 120 for
complete contact information.