VX6854LC datasheet(86/114 Pages) STMICROELECTRONICS

86 / 114 page

EDoF control

VX6854LC

86/114

DocID027110 Rev 2

The relative sharpness among channel varies with the object distance but also in the field of

the image (field curvature), so the votes are then weighted by calibration data in order to

obtain the most appropriate mode or distance at the output.

Note:

The aim of the distance estimation is not to obtain a precise distance but to select the best

parameterization for the correction to be applied in capture, therefore the returned distance

or specified distances range is indicative only.

Like an auto-focus module:

•

The algorithm has failure cases, but the correction is constrained in order to always

have acceptable image quality even if not optimal.

•

For a single image several modes are often possible and giving same level of image

quality.

–

For overlap distances (between macro and portrait modes, or between portrait and

landscape modes), two of the channels may have the same level of sharpness, so

any of the two corresponding distances could be returned, depending on scene

content and field curvature of the module.

–

For scenes with objects at different distances, any of the three distances could be

returned depending on content of the scene, field curvature of the module and

spatial weights used for estimation (edof_estimation_control).

Supermacro mode is used for bar code and business card reading. Supermacro mode uses

a monochrome image. Below 30 cm distance, the MTF is lost and there is too little green

and red pixel information to build a colorized image. However, the blue pixel has enough

MTF to reconstruct a monochrome image.

10.2

Control interface

The modules have a 100 kHz/400 kHz I2C compatible 2-wire control interface. It uses the

SMIA 16-bit index, 8-bit data message format. The CCI interfaces allows the programming

of the EDoF control registers.

VX6854LC датащи(PDF) 86 Page - STMicroelectronics