In contrast to machine vision applications, which make do with constant lighting and fixed focal lengths, in outdoor applications such as traffic monitoring, security or sports, brightness, field of view, zoom, focus and aperture must be able to be flexibly adjusted according to the circumstances. Motorized lenses, which are supported by the BVS CA-GX2 dual GigE camera, offer the possibility to adjust these settings remotely.

Lenses with a fixed focal length that are set manually usually have two "adjusting screws": the focus and the aperture.

These are set once, fixed and should not be changed afterwards.

With variable focal length lenses, the area of interest (AOI) can be adjusted depending on the focal length setting. If these are electrically controllable, it is even possible to set the focal length settings remotely via commands or program routines.

Depending on the motorized lens, different things can be controlled electrically and the way they are controlled also differs:

• Zoom

• focus

• Aperture

  • motor

  • video

  • DC

In addition, electrical lenses allow different voltages and are also sometimes switched differently.

They also support different control voltages (between 3 and 12 VDC) and can differ in terms of wiring. There are also lenses that have potentiometers with which the current position can be measured via a resistor. However, the BVS CA-GX2 does not support potentiometers.

The BVS CA-GX2 has two Hirose-compatible connections on the rear.

Figure 1: BVS CA-GX2 connections

The socket on the right-hand side is for connecting the lens. The pin assignment can be found in the left-hand column of the table.

Figure 2: Wiring of motorized lenses

The figure shows typical wiring.

• Connect Hirose Pin4 (Focus+) to CN Pin4.

• Connect Hirose Pin5 (Focus-) to CN Pin3.

• etc.

The BVS CA-GX2 offers a power supply of up to 100 mA, with a selectable voltage for the outputs for focus, zoom and iris. The voltage is independent of the camera's power supply. Channel 4 (Channel4) can remain open.

The BVS CA-GX2 camera generates a video-like signal with an average brightness and a sync signal to control a video iris lens.

The aperture of the lens is closed as soon as the brightness increases in order to keep the brightness on the sensor constant.

The advantage of the video iris over AutoExposure is that a larger brightness range prevents the smear effect on a CCD sensor, as the sensor cannot be overexposed; however, the video iris is slower than AutoExposure and AutoGain, both of which are also supported by the camera.

Pin assignment of a standard video iris (4 pin EIAJ).

Figure 3: Pin assignment of Video Iris

The square 4-pin connector of the camera is used to control the video iris.

There is a wizard for this in ImpactControlCenter .

Figure 4: Lens Control Wizard

The "Drive Level" voltage is selected to match the lens.

The focus, zoom and iris buttons control the respective motors at an adjustable speed.

Video iris can be selected to open or close completely (for adjustment) and for an auto mode

Note: Additional settings such as Level (sensitivity) and/or ALC (Peak or Average) can possibly be set directly on the lens using a potentiometer.

ALC settings have no effect due to the digital video signal!

Further information about your lens can be found in the lens manual. AGC/AEC in conjunction with mvIrisAuto can lead to oscillating brightness.

The aim is to bring the video iris into a range in which it opens automatically as soon as the brightness decreases and closes as soon as the brightness increases.

• Opening the iris via the mvIrisOpen command: The aperture is opened with the minimum F-number supported by the lens; e.g. f/1.2 (see lens manual)

• Set the camera's exposure time so that the image is not saturated

• Set Exp = 4 x min.

• Aperture is automatically set to f/2.4

• Set working exposure time to = 16 x min.; aperture is automatically set to f/4.8.

Although the parameters of mvLensControl are specific to Balluff, they appear in the camera XML file in accordance with the GigE Vision and SFNC (Standard Feature Naming Convention) standards. This means that they can also be used by third-party applications without any problems.

Figure 5: ImpactControlCenter - mvLensControl

The screenshot shows how the parameters appear in Halcon from MVTec:

Figure 6: mvLensControl in HALCON

The screenshot shows the corresponding Hdevelop example and Halcon with the same settings:

Figure 7: mvLensControl in Hdevelop

Electric lenses differ in terms of the maximum sensor diameter and the maximum resolution supported in each case. BVS CA-GX2 cameras, for example, use sensors with a diameter of 2/3" to 1.1". These properties must be taken into account when compiling lens/camera combinations.

The following list provides an overview of the lenses supported by the BVS CA-GX2. It is intended as a guide only. If you do not find a particular lens in the list, this does not mean that it is not supported by the camera. If you have any questions in this regard, please contact our support team.