CYII4SM1300AA CYPRESS [Cypress Semiconductor], CYII4SM1300AA Datasheet - Page 25

• Manufacturer Part Number: CYII4SM1300AA
• Description: IBIS4-1300 1.3 MPxl Rolling Shutter CMOS Image Sensor
• Manufacturer: CYPRESS [Cypress Semiconductor]

Example: tIming Used on IBIS4 Breadboard
The next figure is the timing as used in the IBIS4 breadboard
version 12 January 2000. In this baseline only CALIB_F is used
Illumination Control
There are two means of controlling the illumination level electri-
cally. For high light levels, there is an electronic shutter. For low
light levels, the output signal can be amplified by controlling the
output amplifier gain. The offset level of the signal can also be
controlled digitally.
“Rolling Curtain" Electronic Shutter
The electronic shutter can reduce the integration time (=
exposure time). This is achieved by an additional reset pulse
every frame. In this way, the integration time is reduced to a
fraction of the frame readout time.
There are two Y shift registers. One of them points at the row that
is currently being read out. The other shift register points at the
row that is currently being reset. Both pointers are shifted by the
same Y-clock and move over the focal plane. The integration
time is set by the delay between both pointers.
Figure 23. Schematic Representation of Curtain Type Elec-
tronic Shutter
Document Number: 38-05707 Rev. *C
Reset
pointer
CLCK_Y
SIN
CALIB_S
Or CALIB_F&UNITY GAIN
RESET
SYNC_X
CLCK_X
SYNCY_L and SYNCY_R; once per frame per register (for electronic shutter L and R at different moments)
L/R
SHY
1 usec
Figure 22. Pulse Sequence Used in IBIS4 Breadboard v. January 2000
Is calib_s is used, calib_f&unity are 0
Is calib_f&unity are used, calib_s is 0
Readout
pointer
(pulsing once per frame). CALIB_S (pulse every line) is shown
as reference, but is actually not used in the baseline. The
UNITY_GAIN pulse is identical to CALIB_F.
This is a so-called 'rolling curtain'-type shutter. It 'rolls' over the
focal plane.
The left and right shift registers can be used both for pointing to
the row that is readout or the row that is reset. The shift register
that is active for readout or reset is selected by the signal on L/R.
In the above timing diagrams, we use the R shift register for
readout, and the L shift register for electronic shutter reset. We
call them the readout shift register and reset shift register.
The integration time is controlled by the delay between the
SYNCY_L and SYNCY_R pulse. The shorter this delay, the
shorter the integration time and the smaller the output signal will
be.
If the electronic shutter is not used, the L/R signal is not pulsed.
The integration time is then equal to the frame readout time.
For proper operation of the ES, the CLOCK_Y must come as an
uninterrupted pulse train. Also during the dead time between
frames the CLOCK_Y must be clocked. The reason is that each
line should see the same elapsed time between the "ES-reset"
and the reset of the line being read-out. If the CLOCK_Y is
halted, the lines between the two pointers will have a longer
effective integration time, and appear brighter.
Gain Control
For low illumination levels, the electronic shutter is not used - or
set to its maximal value. Longer integration times can only be
obtained by decreasing the frame rate. As an alternative or in
complement, one can increase the output amplifier gain.
The gain is controlled by a 4-bit word. Gain values vary between
1.2 and 16, and on an exponential scale, as the F-stops of a lens.
Of course, increasing the signal amplitude by increasing the
gain, will also increase the noise level. The apparent increase of
sensitivity is at the cost of a lower dynamic range.
CYII4SM1300AA
Page 25 of 35
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