AP0101CS datasheet(21/42 Pages) ONSEMI

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AP0101CS/D Rev. 7, 1/16 EN

©Semiconductor Components Industries, LLC,2016.

AP0101CS HDR: Image Signal Processor (ISP)

Camera Control and Auto Functions

Auto Exposure

The auto exposure algorithm optimizes scene exposure to minimize clipping and satu-

ration in critical areas of the image. This is achieved by controlling exposure time and

analog gains of the sensor core as well as digital gains applied to the image.

The auto exposure module analyzes image statistics collected by the exposure measure-

ment engine, makes a decision, and programs the sensor and color pipeline to achieve

the desired exposure. The measurement engine subdivides the image into 25 windows

organized as a 5 x 5 grid.

Figure 11:

5 x 5 Grid

AE Track Driver

Other algorithm features include the rejection of fast fluctuations in illumination (time

averaging), control of speed of response, and control of the sensitivity to small changes.

While the default settings are adequate in most situations, the user can program target

brightness, measurement window, and other parameters described above.

The driver changes AE parameters (integration time, gains, and so on) to drive scene

brightness to the programmable target.

To avoid unwanted reaction of AE on small fluctuations of scene brightness or momen-

tary scene changes, the AE track driver uses a temporal filter for luma and a threshold

around the AE luma target. The driver changes AE parameters only if the difference

between the AE luma target and the filtered luma is larger than the AE target step and

pushes the luma beyond the threshold.

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