AR0132AT datasheet(21/56 Pages) ONSEMI

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AR0132AT/D Rev. 9, 2/16 EN

©Semiconductor Components Industries, LLC, 2016.

AR0132AT: 1/3-Inch CMOS Digital Image Sensor

High Dynamic Range Mode

HDR Specific Exposure Settings

In HDR mode, pixel values are stored in line buffers while waiting for all 3 exposures to

be available for final pixel data combination. There are 42 line buffers used to store inter-

mediate T1 data. Due to this limitation, the maximum coarse integration time possible is

equal to 42*T1/T2 lines.

For example, if R0x3082[3:2] = 2, the sensor is set to have T1/T2 ratio = 16x. Therefore the

maximum number of integration lines is 42*16 = 672 lines. If coarse integration time is

greater than this, the T2 integration time will stay at 42 lines. The sensor calculates the

ratio internally, enabling the linearization to be performed. If companding is being used

then relinearization would still follow the programmed ratio. For example, if the T1/T2

ratio was programmed to 16x but coarse integration was increased beyond 672 then one

would still use the 16x relinearization formulas.

An additional limitation is the maximum number of exposure lines in relation to the

frame_length_lines register. In Linear mode, as described on page 20, maximum

coarse_integration_time = frame_length_lines - 1. However in HDR mode, since the

coarse integration time register controls T1, the max coarse_integration time is

frame_length_lines - 45.

Putting the two criteria listed above together, it can be summarized as follows:

(EQ 3)

In HDR mode, subline integration is not utilized. As such, fine integration time register

changes will have no effect on the image.

There is also a limitation of the minimum number of exposure lines that can be used.

This is summarized in the following formula:

(EQ 4)

Due to limitation on the internal floating point calculation, the exact ratio specified by

the RATIO_T2_T3 (R0x3082[5:4]) may not be achievable.

Motion Compensation

In typical multi-exposure HDR systems, motion artifacts can be created when objects

move during the T1, T2 or T3 integration time. When this happens, edge artifacts can

potentially be visible and might look like a ghosting effect.

To correct this feature, the AR0132AT has special 2D motion compensation circuitry that

detects motion artifacts and corrects the image accordingly.

There are two motion compensation options available. One using the default HDR

motion compensation feature can be enabled by setting R0x318C[14] = 1. Additional

parameters are available to control the extent of motion detection and correction as per

the requirements of the specific application. These can be set in R0x318C–R0x3190. The

other is using the DLO method of HDR combination. When using DLO, R0x318C[14] is

ignored. DLO is enabled by setting R0x3190[13] = 1. Noise filtering is enabled by setting

R0x3190[14] = 1. For more information, please refer to the AR0132AT Register Reference

document.

maximum coarse_integration_time

minimum 42 T1 T2, frame_length_lines 45

–







minimum coarse_integration_time

0.5

*T1 T2



 T2 T3





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