VX6854LC datasheet(96/114 Pages) STMICROELECTRONICS

96 / 114 page

Image optimization

VX6854LC

96/114

DocID027110 Rev 2

11.2

Mapped couplet correction (Bruce)

The mapped couplet defect correction filter is designed to intelligently correct the first defect

in a couplet thereby changing a couplet into a single pixel defect. Single pixel defects can

then be corrected using the dynamic defect correction filter.

The mapped couplet correction filter requires exact coordinate information for each of the

couplets to be repaired. The couplet coordinates are stored in non-volatile-memory (NVM)

during production test. The mapped couplet correction filter does not operate in binning

mode or in sub sample mode and is automatically disabled.

The mapped couplet correction is controlled by register 0x0B05:

0 - Disable

1 - Enable

11.3

Lens shading correction

The sensor has an adaptive (four color temperature) lens shading correction function which

can be used to reduce the effect of roll off in the optical system. Correction is carried out

individually for all four color planes, each gain is calculated based on the distance from the

image centre to the pixel in question using a two factor polynomial (R2 and R4).

In order to optimize the adaptive lens shading algorithm, the coefficients for each device are

calculated under D65 lighting conditions and programmed in the NVM memory at production

test.

Settings for three other color temperatures (Cool White, U30, and Horizon) are calculated

from characterization data and these are stored in the NVM memory. The calculation of the

color temperature is performed by the sensor using the color feedback registers. Therefore

it is necessary for the host to supply the sensor with the white balance gains.

The lens shading function can be used with the profile1 and profile 2 scaler and with crop

and sub-sampling.

The lens shading correction is controlled by register 0x0B00:

0 - Disable

1 - Enable

The correction applied is 75%.

Figure 42. Lens shading images

Original image

Corrected image

VX6854LC датащи(PDF) 96 Page - STMicroelectronics