
MT9F002
www.onsemi.com
25
SENSOR READOUT CONFIGURATION
Image Acquisition Modes
The MT9F002 supports two image acquisition modes:
1. Electronic rolling shutter (ERS) mode
This is the normal mode of operation. When the
MT9F002 is streaming; it generates frames at a
fixed rate, and each frame is integrated (exposed)
using the ERS. When the ERS is in use, timing
and control logic within the sensor sequences
through the rows of the array, resetting and then
reading each row in turn. In the time interval
between resetting a row and subsequently reading
that row, the pixels in the row integrate incident
light. The integration (exposure) time is controlled
by varying the time between row reset and row
readout. For each row in a frame, the time between
row reset and row readout is fixed, leading to a
uniform integration time across the frame. When
the integration time is changed (by using the
two−wire serial interface to change register
settings), the timing and control logic controls the
transition from old to new integration time in such
a way that the stream of output frames from the
MT9F002 switches cleanly from the old
integration time to the new while only generating
frames with uniform integration. See “Changes to
Integration Time” in the MT9F002 Register
Reference.
2. Global reset mode
This mode can be used to acquire a single image at
the current resolution. In this mode, the end point
of the pixel integration time is controlled by an
external electromechanical shutter, and the
MT9F002 provides control signals to interface to
that shutter. The operation of this mode is
described in detail in “Global Reset”.
The benefit of using an external electromechanical shutter
is that it eliminates the visual artifacts associated with ERS
operation. Visual artifacts arise in ERS operation,
particularly at low frame rates, because an ERS image
effectively integrates each row of the pixel array at a
different point in time.
Window Control
The sequencing of the pixel array is controlled by the
x_addr_start, y_addr_start, x_addr_end, and y_addr_end
registers. For both parallel and serial HiSPi interfaces, the
output image size is controlled by the x_output_size and
y_output_size registers.
Pixel Border
The default settings of the sensor provide a 4608H
x3288V image. A border of up to 8 pixels (4 in binning) on
each edge can be enabled by reprogramming the
x_addr_start, y_addr_start, x_addr_end, y_addr_end,
x_output_size, and y_output_size registers accordingly.
This provides a total active pixel array of 4640H x 3320V
including border pixels.
Readout Modes
Horizontal Mirror
When the horizontal_mirror bit is set in the
image_orientation register, the order of pixel readout within
a row is reversed, so that readout starts from x_addr_end and
ends at x_addr_start. Figure 28 shows a sequence of 6 pixels
being read out with horizontal_mirror = 0 and
horizontal_mirror = 1. Changing horizontal_mirror causes
the Bayer order of the output image to change; the new
Bayer order is reflected in the value of the pixel_order
register.
Figure 28. Effect of Horizontal Mirror on Readout Order
G0[11:0]
R2[11:0]
LINE_VALID
horizontal_mirror = 0
horizontal_mirror = 1
DOUT[11:0]
DOUT[11:0]
R0[11:0] G1[11:0] R1[11:0] G2[11:0] R2[11:0]
G2[11:0] R1[11:0] G1[11:0] R0[11:0] G0[11:0]
To enable image horizontal mirror mode, set register bit
R0x3040[14]=1.
•0 = Normal readout
•1 = Readout is mirrored horizontally so that the column
specified by x_addr_end_ is read out of the sensor first.
Vertical Flip
When the vertical_flip bit is set in the image_orientation
register, the order in which pixel rows are read out is
reversed, so that row readout starts from y_addr_end and
ends at y_addr_start. Figure 29 shows a sequence of 6 rows
being read out with vertical_flip = 0 and vertical_flip = 1.
Changing vertical_flip causes the Bayer order of the output
image to change; the new Bayer order is reflected in the
value of the pixel_order register.