Varex Imaging 2315NDT, Руководство пользователя

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USER
M
ANUAL
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2315NDT v2 CMOS X-ray Detector User Manual
14.4 Powering-down the Detector
To power down the detector:
1
Close SCap.
2
Unplug the AC cable of the power supply to turn off the detector.
15.0 Calibration and Image Quality Guidelines
SCap provides image processing stages that compensate for the following imperfections of
the X-Ray system and detector:
•
Beam flatness and heel effect
•
Scintillator grain
•
Visible structures in the protective cover and fiber optic plate
•
Pixel voltage offset and gain variation
•
Pixel non-linear response
•
Defective lines and pixels
15.1 SCap Image Correction Functions
The following image correction functions are provided in SCap:
•
Dark Correction : The dark image is the mean of several dark frames. Dark correction
removes static offsets between pixels so that a dark image is presented as an approximately
uniform grey value. The dark correction is sensitive to changes in integration time and
temperature. The averaged dark image should be acquired shortly before or after the
acquisition of the image to be corrected and with the same integration time.
•
Linearity Correction : Detector pixels have a slightly non-linear response to light, which
corresponds to about 2% deviation from the linear response at mid-scale. To ensure that the
flood calibration works accurately over the dynamic range of the detector, both the raw
image and the flood image are corrected for non-linearity.
•
Gain Correction : The flood calibration image can be inspected by using the View menu, and
is a floating-point multiplication matrix normalized to 1. The calibration image is created
from the mean of several flood images, which are also dark corrected. Multiplying by the
flood calibration image has the effect of reversing the variation in X-ray conversion gain
between pixels or regions so that a corrected open field X-ray image will have near-constant
grey levels across the FoV.
•
Defect Correction : Some defective lines and pixels may be present on the sensor. These are
defined as having a response that deviates by a specified amount from the ideal. A defect
map is created during factory testing of the detector and is distributed with the detector.