Lenses for network video cameras

Lenses for network video cameras

i-CS lens - a new industry standard

An i-CS lens is an intelligent CS-mount lens that contains information about, among other things, its own geometrical distortion and the exact position of its zoom, focus, and iris opening. By reading this information from the lens, the camera discovers the type of lens mounted on it.

i-CS lenses use an open protocol developed jointly by Axis Communications and Computar®. Thanks to the information from the lens and the use of the protocol, the camera can optimize its image quality at all times. Using data from the lens about geometrical distortion, it can perform BDC (Barrel Distortion Correction). The lens also contains information that enables the camera to stabilize the image automatically using EIS (Electronic Image Stabilization).

The open communication standard used in i-CS lenses means that other manufacturers can develop and manufacture their own i-CS lenses, with other features, and these lenses will still be interchangeable.

Figure 7: An i-CS lens.

How an i-CS lens works

An i-CS lens contains data about its own characteristics, for example:

  • Model and manufacturer.
  • Geometrical distortion.
  • The focal length at a given zoom and focus position.
  • The F-number at a given zoom and iris position.
  • Trace, that is, data describing the required position of the focus lens in relation to the zoom lens to get a sharp image of an object at a certain distance. 

The lens also contains a temperature sensor, to provide information about its operating tem-perature range. The current range of Axis network cameras with support for i-CS lenses makes use of all these char¬acteristics. Other data in the i-CS lens may also be available.

An i-CS lens has three motors that enable automatic and remote control of all the features of the lens, for example, zoom, focus, and iris opening. In turn, this control enables camera features such as BDC and EIS.

A camera can use the motors in the lens to set generic features, which makes it possible to use an i-CS lens for different purposes. For example, the same i-CS lens can be used on one camera where the focus and iris opening are automatically controlled, but also on another camera where the zoom needs to be readjusted regularly. Thanks to the open protocol, an i-CS lens can be used on different cam¬eras with different capabilities.

Most of the lens adjustments in an i-CS lens are automatic. The user sets the required zoom, and the camera then maintains the focus independently and sets the iris control. If BDC and EIS are enabled, the camera sets these features automatically. Since the camera has information about the setup of the i-CS lens, it can optimize the iris opening for all light conditions.