Axis P-Iris White Paper

WHITE PAPER

P-Iris.

New iris control improves image quality in megapixel and HDTV network cameras.

Table of contents

1. Introduction 3

2. The role of an iris 3

3. Existing lens options 4

4. How P-Iris works 4

5. Redening video quality 6

3

Introduction

The introduction of megapixel or HDTV xed network cameras
has meant greater resolution images but not always better
image quality. Maintaining image sharpness, particularly in
varying outdoor lighting conditions, has proved challenging. It
is a problem that has highlighted the limitations of existing
lens alternatives and the need for a better solution.

Axis Communications’ search for a solution has now led to the
introduction of a new and revolutionary precise iris control,
P-Iris.

P-Iris not only benets megapixel cameras but all xed network cameras. The system optimizes the iris
opening under all lighting conditions and the result is images with better contrast, clarity, resolution and
depth of eld. In short, P-Iris means improved image sharpness and increased image usability for net­work video surveillance operators.

The role of an iris

The P-Iris system involves a new approach to looking at the role of an iris and is the result of a joint
development eort between Axis Communications of Sweden and the Japanese lens manufacturer
Kowa.

The system comprises of a P-Iris lens and specialized software in the camera. The software steers a
motor in the P-Iris lens, enabling automatic and precise control of the iris opening. The key to under­standing P-Iris is to look at how the iris aects image quality.

The iris of a lens regulates the size of a lens’ aperture or opening and the amount of light that passes
through it so that an image can be correctly exposed. Without an iris, an image can become too light in
a very bright environment, or it can be dark if the lens opening is not big enough to let available light in.

The size of the iris opening also has an eect on image sharpness and depth of eld. Depth of eld refers
to the distance in front of and beyond the point of focus where objects appear to be sharp simultane­ously. A wide iris opening reduces depth of eld while a smaller opening increases it. Having good depth
of eld is important in many surveillance applications as it allows more of a scene to be clearly visible.
It is particularly useful in the video monitoring of, for example, a long corridor or parking lot. Image
sharpness generally improves with a smaller iris opening because optical errors can often be reduced. All
lenses create some form of image aberrations when the full lens surface is used.

Fig. 1 Having good depth of eld—where objects at dierent distances from the camera are in focus simultaneously—is important
in many surveillance applications as it allows more of a scene to be clearly visible.

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