AS0260CSSC28SUD20 datasheet(27/83 Pages) ONSEMI

27 / 83 page

AS0260 DS Rev. G Pub. 5/15 EN

©Semiconductor Components Industries, LLC, 2015.

AS0260: 1/6-Inch 1080P High-Definition (HD) System-On-A-Chip (SOC) Digi-

tal Image Sensor

Adaptive PGA (APGA)

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 AS0260 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.

In some cases, different illuminants can introduce different color shading response. The

APGA feature on the AS0260 will compensate for the dependency of the lens shading of

the illuminant. The AS0260 will allow for up to three different illuminants to be compen-

sated for.

Color Interpolation and Edge Detection

In the raw data stream fed by the sensor core to the IFP, each pixel is represented by a

10-bit integer, which can be considered proportional to the pixel’s response to a one-

color light stimulus, red, green, or blue, depending on the pixel’s position under the

color filter array. Initial data processing steps, up to and including the defect correction,

preserve the one-color-per-pixel nature of the data stream, but after the defect correc-

tion it must be converted to a three-colors-per-pixel stream appropriate for standard

color processing. The conversion is done by an edge-sensitive color interpolation

module. The module adds the incomplete color information available for each pixel

with information extracted from an appropriate set of neighboring pixels. The algorithm

used to select this set and extract the information seeks the best compromise between

preserving edges and filtering out high-frequency noise in flat field areas. The edge

threshold can be set through variable settings.

Color Correction and Aperture Correction

To achieve good color fidelity of the IFP output, interpolated RGB values of all pixels are

subjected to color correction. The IFP multiplies each vector of three pixel colors by a

3 x 3 color correction matrix. The three components of the resulting color vector are all

sums of three 10-bit numbers. Since such sums can have up to 12 significant bits, the bit

width of the image data stream is widened to 12 bits per color (36 bits per pixel). The

color correction matrix can either be programmed by the user or automatically selected

by the AWB algorithm implemented in the IFP. Color correction should ideally produce

output colors that are independent of the spectral sensitivity and color crosstalk charac-

teristics of the image sensor. The optimal values of the color correction matrix elements

depend on those sensor characteristics and on the spectrum of light incident on the

sensor. The color correction settings can be adjusted using variables.

To increase image sharpness, a programmable 2D aperture correction (sharpening filter)

is applied to color-corrected image data. The gain and threshold for 2D correction can

be defined through variable settings.

One-Time Programmable Memory

the AS0260 contains one-time programmable memory (OTPM), suitable for storing

separate lens shading correction settings, color calibration, external mechanisms,

initialization settings, and module identification, that can be programmed during the

module manufacturing process. Programming the OTPM requires the use of a high

voltage at the VPP pin. during normal operation, the VPP pin should be left floating. The

OTPM can be accessed through the two-wire serial interface. Refer to the AS0260 Devel-

oper Guide for programming procedures.

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