LUPA-4000_07 Datasheet, PDF (18/38 Pages) Cypress Semiconductor – 4M Pixel CMOS Image Sensor

LUPA-4000
An additional reset pulse of minimum 2 µsec can be given
during integration by asserting Reset_ds to implement the
double slope integration mode.
Read out of the image sensor
As soon as the information of the pixels is stored in to the
memory element of each pixel, this information can be readout
sequentially. As seen in the previous section, integration and
readout can also be done in parallel.
The readout timing is straightforward and is basically
controlled by means of sync and clock pulses.
Figure 14 shows the top level concept of this timing. The
readout of a frame consists of the frame overhead time, the
selection of the lines sequentially and the readout of the pixels
of the selected line
Figure 14. Readout of the image sensor. F.O.T: Frame overhead time. R.O.T: Row overhead time. L: selection of line, C:
Selection of column
Read frame I
Integration I + 2
F.O.T L1
Readout Lines
L2 L3
L2048
R.O.T C1 C2
Readout pixels
C2048
The readout of an image consists of the FOT (Frame overhead
time) and the sequential selection of all pixels. The FOT is the
overhead time between 2 frames to transfer the information on
the photodiode to the memory elements. From Figure 13 it
should be clear that this time is the time that Mem_hl is low
(typically 5 µs). After the FOT the information is stored into the
memory elements and a sequential selection of rows and
columns makes sure the frame is read.
X- and Y- addressing
To readout a frame the lines are selected sequentially.
Figure 15 gives the timing to select the lines sequentially. This
is done by means of a Clock_y and a Sync_y signal. The
Sync_y signals synchronises the y-addressing and initialises
the y-address selection registers. The start address is the
address downloaded in the SPI multiplied by 2.
On the rising edge of Clock_y the next line is selected. The
Sync_y signal is dominant and from the moment it occurs the
y-address registers are initialised. If a Sync_y pulse is given
before the end of the frame is reached, only a part of the frame
will be read. To obtain a correct initialisation Sync_y must
contain at least 1 rising edge of Clock_y when it is active.
Document Number: 38-05712 Rev. *B
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