Dalsa Spyder2 - CCD Handling Instructions; Electrostatic Discharge and the CCD Sensor; Protecting against Dust, Oil and Scratches

42 Spyder2 User’s Manual
03-032-10091-06 Teledyne DALSA
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5
CCD Handling
Instructions
5.1 Electrostatic Discharge and the CCD Sensor
Cameras contain charge-coupled device (CCD) i mage sensor s, w hich are metal oxide
semiconductor (MOS) devices and are susceptible to damage from electrostatic discharge
(ESD).
Electrostatic charge introduced to the sensor window surface can induce charge buildup
on the underside of the window that cannot be readily dissipated by the dry nitrogen gas
in the sensor package cavity. When charge buildup occurs, surface-gated photodiodes
(SGPDs) may exhi bi t higher image lag. Some SGPD sensor s, su ch as the IL-P3 used in the
Sp y d er 2 cameras, may also exhibit a highly non-uniform response when affected by
charge buildup, with some pixels displaying a much higher response when the sensor is
exposed to uniform illumination. The charge normally dissipates within 24 hours and the
sensor returns to normal operation.
WARNING:
Charge buildup will affect the camera’s flat-field correction calibration. To avoid
an erroneous calibration, ensure that you perform flat-field correction only after a charge
buildup has dissipated over 24 hours.
5.2 Protecting Against Dust, Oil and Scratches
The CCD window is part of the optical path and should be handled like other optical
components, w ith extreme care.
Dust can obscu r e pixels, pr oduci ng dark pat ches on the sensor response. Dust i s most
visible when the illumination is collimated. The dark patches shift position as the angle of
illumination changes. Dust is normally not visible when the sensor is positioned at the
exit port of an integrating sphere, where the illumination is diffuse.
Dust can normally be removed by blowing the window surface using a compressed air
blower, unless the dust particles are being hel d by an el ectrostatic charge, i n w hich case
either an ionized air blow er or w et cleaning is necessar y .
Oil is usually introduced during handling. Touching the surface of the window
barehanded will leave oily residues. Using rubber fingercots and rubber gloves can