VX6953CB datasheet(86/107 Pages) STMICROELECTRONICS

86 / 107 page

Image optimization

VX6953CB

86/107

8209023 Rev 5

9.5

Lens shading correction

The sensor has an onboard 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 nine parameterization term

(DC offset, x, y, xy, X2, y2, xy2, x2y, x2y2).

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, TL83 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 profile2 scaler and with crop

and subsampling.

The lens shading correction is controlled by register 0x0B00:

0 - Disable

1 - Enable

The correction applied is 75%.

This is meaning image corner relative illumination = 0.75 * image centre relative illumination.

Figure 46. Lens shading images

Original image

Corrected image

VX6953CB датащи(PDF) 86 Page - STMicroelectronics