LUPA-4000 Datasheet, PDF (29/49 Pages) Cypress Semiconductor – 4M Pixel CMOS Image Sensor

LUPA-4000
Data Sheet
4.2 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.
Read frame I
Integration I + 2
F.O.T L1
Readout Lines
L2 L3
L2048
R.O.T C1 C2
Readout pixels
C2048
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.
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.
4.2.1 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.
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Contact: [e-mail] Document #: 38-05712 Rev.**(Revision 1.2 )
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