VX6854LC datasheet(91/114 Pages) STMICROELECTRONICS

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VX6854LC

EDoF control

102

10.3.5

EDoF estimation control (0x0B8A)

This register selects the region of interest (ROI) on which to apply the distance estimation

processing. Four different ROIs are available:

0 or 1: uniform

2: center-weighted

4: spot- large

8: spot narrow

Considering the above order, with increasing values, the estimation will increasingly focus

on objects in the centre of the image. The processing time is identical for all cases.

Figure 36. Focus strategy weightings

10.4

Super macro mode

Unlike the other modes (macro, portrait and landscape), super macro mode cannot be

managed by the automated distance range estimator. The reason is that at distances below

30 cm, there is very little information in green and red channels though there is a significant

energy in the blue channel. The distance estimator needs the four color channel information

to estimate the distance. Below 30 cm, unless the distance is manually programmed using

For text or bar code reading, a monochromatic image can be used. EDoF super macro

mode can be used for that purpose as the EDoF reconstruction engine would use the blue

channel information to calculate the suitable sharpness and denoising.

To enable super macro mode, the user has to program manually the register 0x0B88 to set

a value for distances below 30 cm. The register value being the value of the distance in cm.

It is important to note that as the super macro mode uses one color channel, the HOST has

to consider using only the blue channel information to build a monochromatic image and the

following features need to be disabled or restricted:

•

lens shading correction: only apply blue channel correction

•

disable white balance correction in the host: the white balance gains must still be

calculated and written to the sensor

•

no demosaicing

•

disable any 4 channel gain dependant block in the HOST

•

apply black and white matrix, rather than color matrix. (0 1 0, 0 1 0, 0 1 0)

Narrow spot

Large spot

Center

2 22

1 1 1 1 1

0 0 00 0

0 0 0 0 0

0 0

0 0 0 0 0

00 00 0

0 0 00 0

00 00 0

1 1 1

Uniform

1 1 1 1 1

11 11 1

11 1 11

11 1 1 1

11 1 11

The image is arranged as 5x5 regions for the weightings.

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