VS6724 datasheet(13/118 Pages) STMICROELECTRONICS

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VS6724

Functional description

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2.4

Recovery engine (RE)

The RE is used to process raw Bayer input from the sensor array to an intermediate Bayer

which is correctly white balanced and noise reduced, and can be supplied to the

interpolation engine.

2.4.1

Channel offsets

To achieve the desired black level of Bayer pixel data it is often necessary to apply an offset

to the data. This module provides the functionality to apply color channel dependent offset

on active pixel data, i.e. not dark or black data.

2.4.2

Channel gains

Color dependent gains are applied to active pixel data within this module as part of the

automatic white balance function. The gain inputs are re-synchronized to the first active line.

2.4.3

Lens shading compensation

The lens shading is used to compensate for attenuation in the optical signal caused by

primary and micro lens roll off. The module uses internal counters to determine the input

pixel position in terms of imaging array, to which it applies a simple polynomial gain function.

This gain is dependent on two coefficients which are system specific.

2.4.4

Bayer scaling

The RE architecture includes an optional Bayer scaler/smoothing module which produces a

Bayer image fully compatible with existing image reconstruction techniques.

The scaling factor is fixed at downscale-by-3 (in both x & y), with the basic principle of sub-

sampling from successive 3x3 blocks to produce a pseudo-Bayer pattern (2x2 Bayer pattern

generated from 6x6 Bayer input as illustrated in

Figure 4).

This module is intended for use during viewfinder modes to provide a lower power (and

reduced quality) image for display on LCD.

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