VV6410 datasheet(18/105 Pages) STMICROELECTRONICS

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VV5410 & VV6410

Black Offset Cancellation

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Black Offset Cancellation

In order to produce a high quality output image from VV6410 it is important to maximise the dynamic range of the video output.

This can be achieved by accurately controlling the video signal black level. Within the sensor array of VV6410 there are a number

of lines that are specified to be black, that is they are exposed to the incident light but they are always held in minimum exposure.

VV6410 also has a number of dark lines, that is lines that are integrated for the same length of time as the visible lines but the

pixels within these dark lines are shielded from incident light by an opaque material (e.g. metal 3). The diagram below shows

where the different types of lines that appear within the full array.

VV5410/VV6410 can perform automatic black offset cancellation. VV5410/VV6410 contains an algorithm that monitors the level

of the designated black pixels and applies a correction factor, if required, to provide an ideal black level for the video stream.

The user can control the application of the offset cancellation parameter. The internally calculated offset can be applied to the

video stream or alternatively an externally calculated offset can be applied or finally there is the option of applying no offset at all.

Details of how to select the aforementioned modes can be found in subsubsection 9.5.5.

The black offset cancellation algorithm accumulates data from the centre 2 of the 4 physical black lines. The internal cancellation

algorithm uses a leaky integrator model to control the size of the calculated offset. The leaky integrator model takes as input the

current offset plus a shifted version of the error between the ideal black level and the current offset. The magnitude of the shift in

the error is programmable. It is also possible to control the range of pixel values that will inhibit a change in the calculated offset.

A narrow band (128 +/- 2 codes) or a wide band (128 +/- 4 codes) can be selected. If the latter is selected and the pixel average

Figure 11 : Physical position of Black and Dark Lines

364 pixels

Dark Lines

Black Lines

Visible Pixel Array

VV6410 Arkusz danych(PDF) 18 Page - STMicroelectronics