User`s guide

APDCAM User’s Guide
Page 24/32
driven through a PID controlled. The weight factors of this can be set in the PID_P,
PID_I, PID_D registers. For strongly different temperature settings these might need to
be modified from the factory default. The actual Peltier current can be read in
PELTIER_OUT. The operation of the temperature control can be suspended if all three
PID_x registers are filled with 0. This means no current will be driven through the Peltier
element.
The camera internal temperature is controlled by three variable-speed fans located on
the top of the housing. They are controlled by the Control unit using measured tempera-
tures in the camera (TEMP_xxx registers). From the detector side the first fan cools the
detector housing and the DAQ card. The second moves air through the heatsink of the
Peltier element. It will switch on gradually when the heatsink is either cooler or warmer
than 25 degrees. The third fan cools the Control unit, power supplies and communication
cards. The actual fan speeds can be read from registers FAN_xxx.
The temperature control scheme of APDCAM is highly reconfigurable by special con-
figuration programs from the PC. If the camera is intended to be operated in an environ-
ment where the temperature is significantly different from room temperature or when the
fans need to be controlled manually please consult the manufacturer.
3.4.3. Shutter and calibration light
The shutter is mounted in front of the detector but behind the camera window. It
is operated with and electromagnet controlled from the Control unit. In its basic setup
(SHUTTER_MODE=0) the SHUTTER_STATE register opens and closes the shutter.
The drive electronics is not designed to open/close the shutter at high frequency, but it is
intended for single open/close cycles every few seconds as the shortest period time. The
shutter can be kept open or closed for any time. When the shutter is open the yellow
Shutter LED is lit on the camera backplate.
In SHUTTER_MODE=1 the shutter can be controlled externally by an electrical
signal. For this the shutter signal should be routed to the Optional signal connector in the
backplate using an internal jumper. The shutter state signal can also be output on the
same connector. Please consult the manufacturer if such operation is needed.
The aim of the calibration light is to enable verification of the detector operation,
measurement of SNR levels and noise spectra with variable light input. It is intended nei-
ther for absolute calibration of the sensitivity nor for relative calibration of the pixels.
The light source is an ultra bright red LED. To avoid any electrical interference
the LED is mounted in the Control unit and the light is coupled into the detector housing
using four 1 mm diameter optical fibres. These illuminate the detector from four direc-
tions providing more-or less uniform illumination. The current of the LED is provided by
a current generator which can be controlled digitally through the CALIB_LIGHT regis-
ter. At 0 settings there is no light emission. At about 100-200 the light saturates the detec-
tor amplifier with ~350 V detector voltage. As the detector gain is typically around 30-50
at this bias voltage the maximum light emission at 4095 approximately saturates the de-
tector with low gain around 200 V. (Below 150 V bias voltage the amplifiers show exces-
sive noise.)
When the calibration light is on at any level the yellow Calibration LED is lit on
the camera backplate.