TH7834C Datasheet, PDF (11/13 Pages) ATMEL Corporation – Very Highresolution Linear CCD Image Sensor (12000 Pixels)

Exposure Time
Reduction (See
Figure 8)
1997A–IMAGE–05/02
TH7834C
Figure 6. Typical Spectral Responsitivity
8.0
η=0.8
η=0.7
7.2
η=0.6
6.4
5.6
4.8
4.0
3.2
2.4
1.6
0.8
0
400 500 600 700 800 900 1000 1100
Lambda (nm)
Figure 7. V_SAT versus Φ_A Low Level Typical Curve
Antiblooming
OFF
Antiblooming
ON
3600
3400
3200
3000
2800
2600
2400
2200
2000
1800
1600
1400
1200
1000
800
600
400
200
0
0
VST = 4 V
ΦR Low level = 1.5V
VA = 13V
1 2 3 4 5 6 7 8 8.5
ΦA bias (V)
TH7834 allows a reduction in the exposure time without changing the readout time. It
thus provides a function which is equivalent to an optical iris.
The exposure time reduction consists in increasing the Φ_A gate bias in order to remove
continuously, during period 2, the photoelectrons from the pixel and to inject them into
the antiblooming diode V_A. When Φ_A returns to the normal bias, electrons are integrated
in the pixel.
Only excess electrons are evacuated into V_A (blooming control). Thus, the actual inte-
gration time is ti instead of T_i, without any change in the readout sequence. Register
transfer and reset clocks (Φ_L, Φ_LS and Φ_R) must be pulsed during the T_i integration time.
11