AR0331 datasheet(26/52 Pages) ONSEMI

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AR0331

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SENSOR READOUT

Image Acquisition Modes

The AR0331 supports two image acquisition modes:

• Electronic rolling shutter (ERS) mode:

This is the normal mode of operation. When the

AR0331 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

AR0331 switches cleanly from the old integration time

to the new while only generating frames with uniform

integration. See “Changes to Integration Time” in the

AR0331 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 AR0331 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 24 shows a sequence of 6 pixels

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

Figure 24. 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 25. 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]

AR0331 Datasheet(PDF) 26 Page - ON Semiconductor

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