AP0202AT datasheet(21/54 Pages) ONSEMI

21 / 54 page

AP0202AT/D Rev. 4, Pub. 9/15 EN

©Semiconductor Components Industries, LLC, 2015.

AP0202AT: Image Signal Processor (ISP)

Image Flow Processor

Advance

Image Flow Processor

Image and color processing in the AP0202AT is implemented as an image flow processor

(IFP) coded in hardware logic. During normal operation, the embedded microcontroller

will automatically adjust the operating parameters. For normal operation of the

AP0202AT, streams of raw image data from the attached image sensor are fed into the

color pipeline. The AP0202AT also has the option to select from a number of test

patterns to be input instead of sensor data.

Defect Correction

Image stream processing commences with the defect correction function immediately

after data decompanding.

To obtain defect free images, the pixels marked defective during sensor readout and the

pixels determined defective by the defect correction algorithms are replaced with values

derived from the non-defective neighboring pixels.

AdaCD (Adaptive Color Difference)

The next step in the image stream process is noise reduction. The AP0202AT uses a noise

reduction filter called AdaCD which focuses on removing color noise while preserving

edge details. Automotive applications require good performance in extremely low light,

even at high temperature conditions. In these stringent conditions the image sensor is

prone to higher noise levels, and so efficient noise reduction techniques are required to

circumvent this sensor limitation and deliver a high quality image.

Black Level Subtraction and Digital Gain

After noise reduction, the pixel data goes through black level subtraction and multiplica-

tion by a programmable digital gain. Independent color channel digital gain can be

adjusted with registers. Black level subtraction (to compensate for sensor data pedestal)

is a single value applied to all color channels. If the black level subtraction produces a

negative result for a particular pixel, the value of this pixel is set to 0.

Positional Gain Adjustments (PGA)

Lenses tend to produce images whose brightness is significantly attenuated near the

edges. There are also other factors causing fixed pattern signal gradients in images

captured by image sensors. The cumulative result of all these factors is known as image

shading. The AP0202AT has an embedded shading correction module that can be

programmed to counter the shading effects on each individual R, Gb, Gr, and B color

signal.

The Correction Function

The correction functions can then be applied to each pixel value to equalize the

response across the image as follows:

(EQ 1)

where P are the pixel values and f is the color dependent correction functions for each

color channel.

Pcorrected row, col



Psensor row, col

 f(row, col)



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