AR0833 Datasheet, PDF (48/64 Pages) ON Semiconductor – 8 Mp CMOS Digital Image Sensor

AR0833: 1/3.2-Inch 8 Mp CMOS Digital Image Sensor
Integration Time for Interlaced HDR Readout
Control of the Electromechanical Shutter
Figure 35 on page 48 shows two different ways in which a shutter can be controlled
during the global reset sequence. In both cases, the maximum integration time is set by
the difference between global_read_start and global_rst_end. In shutter example 1, the
shutter is open during the initial ERS sequence and during the row reset phase. The
shutter closes during the integration phase. The pixel array is integrating incident light
from the start of the integration phase to the point at which the shutter closes. Finally,
the shutter opens again after the end of the readout phase. In shutter example 2, the
shutter is open during the initial ERS sequence and closes sometime during the row
reset phase. The shutter both opens and closes during the integration phase. The pixel
array is integrating incident light for the part of the integration phase during which the
shutter is open. As for the previous example, the shutter opens again after the end of the
readout phase.
Figure 35: Control of the Electromechanical Shutter
Trigger
Wait for end of current row
Automatic at end of frame readout
ERS Row Reset
Integration
Readout ERS
global_rst_end
global_read_start
maximum integration time
SHUTTER Example 1
shutter open (physical)
SHUTTER Example 2
shutter open (physical)
actual integration time
shutter closed
actual integration time
closed shutter open
shutter closed
shutter open
shutter open
It is essential that the shutter remains closed during the entire row readout phase (that
is, until FV has negated for the frame readout); otherwise, some rows of data will be
corrupted (over-integrated).
It is essential that the shutter closes before the end of the integration phase. If the row
readout phase is allowed to start before the shutter closes, each row in turn will be inte-
grated for one row-time longer than the previous row.
After FV negates to signal the completion of the readout phase, there is a time delay of
approximately (10 * line_length_pck) before the sensor starts to integrate light-sensitive
rows for the next ERS frame. It is essential that the shutter be opened at some point in
this time window; otherwise, the first ERS frame will not be uniformly integrated.
The AR0833 provides a SHUTTER output signal to control (or help the host system
control) the electromechanical shutter. The timing of the SHUTTER output is shown in
Figure 36 on page 49. SHUTTER is negated by default. The point at which it asserts is
controlled by the programming of global_shutter_start. At the end of the global reset
readout phase, SHUTTER negates approximately (2 * line_length_pck) after the negation
of FV.
AR0833_DS Rev. H Pub. 4/15 EN
48
©Semiconductor Components Industries, LLC, 2015.