Lenses for network video cameras

P-Iris

P-Iris is an automatic, precise iris control developed by Axis Communications of Sweden and Kowa Company of Japan. It involves a P-Iris lens with a motor and specialized software. The system addresses the shortcomings of an auto-iris lens, and provides improvements in contrast, clarity, resolution and depth of field.

In bright situations, the P-Iris limits the closing of the iris to avoid blurring (diffraction) caused when the iris opening becomes too small. This can typically happen in cameras that use DC-iris lenses in combination with megapixel sensors, which have small pixels. Being able to avoid diffraction and at the same time benefit from an automatically controlled iris is of great value in outdoor video surveillance applications.

A P-iris lens

Figure 6: A P-iris lens.

The motor in the P-Iris lens precisely controls the position of the iris opening. Together with the software for optimizing the performance of the lens and image sensor, the P-Iris automatically provides the best iris position for optimal image quality in all lighting conditions.

In Axis network cameras with P-Iris, the user interface provides a scale of f-numbers ranging from the widest to the smallest iris opening. This feature allows the user to adjust the preferred iris position, which is the position used by the automatic control for most lighting conditions.