AR0141CS datasheet(19/48 Pages) ONSEMI

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AR0141CS

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SENSOR READOUT

Image Acquisition Modes

The AR0141CS supports two image acquisition modes:

• Electronic rolling shutter (ERS) mode

This is the normal mode of operation. When the

AR0141CS 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 the same, 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

AR0141CS switches cleanly from the old integration

time to the new while only generating frames with

uniform integration. See “Changes to Integration Time”

in the AR0141CS Register Reference.

• 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 AR0141CS provides

control signals to interface to that shutter.

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.

Readout Modes

Horizontal Mirror

When the horiz_mirror bit (R0x3040[14]) is set in the

read_mode register, the order of pixel readout within a row

is reversed, so that readout starts from x_addr_end + 1 and

ends at x_addr_start. Figure 21 shows a sequence of 6 pixels

being read out with R0x3040[14] = 0 and R0x3040[14] = 1.

Figure 21. Effect of Horizontal Mirror on Readout Order

G0[11:0] R0[11:0] G1[11:0] R1[11:0] G2[11:0] R2[11:0]

R2[11:0] G2[11:0] R1[11:0] G1[11:0] R0[11:0]

G3[11:0]

LINE_VALID

horizontal_mirror = 0

horizontal_mirror = 1

DOUT[11:0]

Vertical Flip

When the vert_flip bit (R0x3040[15]) is set in the

read_mode 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 30 shows a sequence of 6

rows being read out with R0x3040[15] = 0 and R0x3040[15]

= 1.

Figure 22. Effect of Vertical Flip on Readout Order

Row0[11:0] Row1[11:0] Row2[11:0] Row3[11:0] Row4[11:0] Row5[11:0]

Row5[11:0] Row4[11:0] Row3[11:0] Row2[11:0]

FRAME_VALID

vertical_flip = 0

vertical_flip = 1

Row1[11:0]

DOUT[11:0]

Row6[11:0]

Row2[11:0]

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