CCD181 Datasheet, PDF (4/11 Pages) Seme LAB – Variable-Element High-Speed Linear Image Sensor

CCD181
Integration Control Operation:
Variable integration times which are less than the CCD exposure
time may be attained by supplying a clock to the integration control
gate. Clocking φIC reduces the integration time from tEXPOSURE to
tINT (Fig. 3). This reduces the photosite signal in all photosites by
the ratio EXPOSURE to tINT. Greater than 10:1 reduction in average
photosite signal can be achieved with integration control.
The integration-control and anti-blooming features can be imple-
mented simultaneously. This is done by setting the φIC, clock-low
level to approximately 5 to 7 volts.
DEFINITION OF TERMS
Charge-Coupled Device — A Charge-coupled device is a semi-
conductor device in which finite isolated charge-packets are trans-
ported from one position in the semiconductor to an adjacent posi-
tion by sequential clocking of an array of gates. The charge-packets
are minority carriers with respect to the semiconductor substrate.
Sample -and Hold Clock φSHA, φSHB) — The voltage waveform
applied to the sample-and-hold gates in the output amplifiers to cre-
ate a continuous sampled video signal at the output. The sample-
and-hold feature may be defeated by connecting φSHA and φSHB to
VDD.
Dark Reference — Video output level generated from sensing
elements covered with opaque metallization which provides a refer-
ence voltage equivalent to device operation in the dark. This per-
mits use of external DC restoration circuitry.
Isolation Cell — This is a site on-chip producing an element in the
video output that serves as a buffer between valid video data and
dark reference signals. The output from an isolation cell contains
no valid information and should be ignored.
Dynamic Range — The saturation exposure divided by the RMS
temporal noise equivalent exposure. Dynamic range is sometimes
defined in terms of peak-to-peak noise. To compare the two defini-
tions a factor of four to six is generally appropriate in that peak-to-
peak noise is approximately equal to four to six times RMS noise.
RMS Noise Equivalent Exposure — The exposure level that
gives an output signal to the RMS noise level at the output in the
dark.
Saturation Exposure — The minimum exposure level that will
provide a saturation output signal. Exposure is equal to the light
intensity times the photosites integration time.
Charge Transfer Efficiency — Percentage of valid charge in-
formation that is transferred between each successive stage of the
transport registers.
Responsivity — The output signal voltage per unit exposure for a
specified spectral type of radiation. Responsivity equals output volt-
age divided by exposure.
Total Photoresponse Non-uniformity — The difference of the
response levels of the most and the least sensitive element under
uniform illumination. Measurement of PRNU excludes first and last
elements.
Dark Signal — The output signal in the dark caused by thermally
generated electrons that is a linear function of the integration time
and highly sensitive to temperature.
Saturation Output Voltage — The maximum usable signal out-
put voltage. Charge transfer efficiency decreases sharply when the
saturation output voltage is exceeded.
Integration Time — The time interval between the falling edge of
any two successive transfer pulses (φX). The integration is the time
allowed for the photosites to collect charge.
Exposure Time - The time interval between the falling edge of the
two transfer pulses (φX) shown in the timing diagram. The exposure
time is the time between transfers of signal charge from the photosites
into the transport registers.
Pixel - A picture element (photosite).
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