ITS applications require images to be captured over a range of distances from the camera. To ensure all the images are in focus needs a large depth of field which requires the camera iris to be kept small. The focus is still a compromise, and at the limits of distance the focus will not be as good as in the middle. By using a fast focus lens the image can be in sharp focus at all distances, giving better quality images and increasing recognition percentages.

To reduce motion blur it's often necessary to use a short exposure time and the combination of small aperture with short exposure means that a lot of light is needed. Some systems compensate by increasing the camera gain, which can create unacceptable noise in the image. The fast focus lens allows the camera iris to be opened, giving much brighter, better quality images.

The ability to change the focus means that images can be taken over much longer ranges. For highway systems the length of road that can be imaged is longer. For tolling and car park applications, the distance to the vehicle can vary more. When taking multiple images of a vehicle, the vehicle can be in good focus for all images by changing the focus to track its movement. When imaging a junction or multi-lane highway, there is more flexibility on camera position and where the vehicle can be located and still be in focus.

Shape-changing liquid lenses quickly adjust the camera focus using technology that is similar to the human eye. For example, where a liquid lens is used mounted behind a traditional 200mm (7.8in) macro lens, the combined focus can typically be adjusted anywhere from 100mm (3.9in) to infinity. Focus changes typically take 10ms, so after taking one image the focus can be almost immediately ready for the next image.

The TR-CL180 Lens Controller from Gardasoft provides accurate and fast control of the high-performance Optotune liquid lenses. The focus can be changed using Ethernet commands or a input signal that steps through a series of different focus positions. The Optotune lenses have individual calibration data stored within them and the TR-CL180 uses this data to precisely focus the lens, including compensating for thermal expansion.

For system integrators requiring a volume solution an embedded version of the Gardasoft lens controller is available. Please contact us for more information.