Teledyne Princeton Instruments PI-MAX 3, Системное руководство

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70 PI-MAX
®
3 System Manual Issue 2
7.5.2 Setting the Temperature
Regardless of the type of cooling, the CCD array temperature is set via the application
software. When WinX/32 is the controlling software, temperature control is done via
the Setup
►
Detector Temperature menu choice. When LightField is being used,
temperature control is done on the Sensor expander.
Once the target (desired) array temperature {Temperature Setpoint} has been set, the
software controls the camera's cooling circuits to reach set array temperature. On
reaching that temperature, the control loop locks to that temperature for stable and
reproducible performance. When the Target Temperature {Temperature Setpoint} has
been reached, the current temperature is Locked. The on-screen indication allows easy
verification of temperature lock.
Temperature lock to a set temperature in the operating range will typically occur within
ten minutes. Another five minutes will be required for maximum temperature stability to
be achieved.
NOTE:
The WinX/32 Detector Temperature dialog will not display
temperature information while you are acquiring data.
7.6 Exposure
Data acquisition has two parts:
• Exposure;
Exposure refers to the integration of a signal of interest on the CCD array.
• Readout.
Readout is the transfer of the integrated signal from the array pixels to a shift
register and from there to a preamplifier.
During exposure, each pixel in the two-dimensional grid of individual pixels senses the
intensity of light falling on its collection area and stores a proportional amount of
charge in its associated well. Once charge accumulates for the exposure time via gating
sequences defined in the application software, the pixels are read out serially.
Because CCD arrays are always sensitive to light, light must not be allowed to fall on the
array during readout (with a few exceptions). Intensified cameras such as the PI-MAX3
rely on gating the intensifier off, to prevent light from reaching the array. During each
data acquisition, the intensifier is gated on and off (this may happen a number of times
if there are multiple gates per exposure) to allow the pixels to register light during the
on period. It is gated off for the readout period.
7.6.1 Exposure with an Image Intensifier
PI-MAX3 cameras use an image intensifier both to gate light on and off and to greatly
increase the brightness of the image. In these cameras the image intensifier detects and
amplifies the light, and the CCD is used for readout. The exposure programmed by
software in this case refers to duration of gating of the intensifier.
The MCP (microchannel plate) of the intensifier is composed of more than 10
6
individual miniature electron multipliers with an excellent input to output spatial
geometric accuracy. Intensifier gain is varied by adjusting the voltage across the MCP or
the voltage across the MCP output and the phosphor. This second parameter is a
factory adjustment, as it affects both the gain and the resolution of the intensifier.