- Technology |
- ICR Function
Infrared light
The portion of light visible to the human eye lies in a wavelength range from approx. 380 to 780 nano metres (nm), whereas the infrared light (IR radiation) lies in a wavelength range from the visible light (780nm) up to the long wave rays. Infrared light is not visible to the human eye.
ICR Function
This means:
For daylight mode: The infrared light has an interfering effect on the image quality of the camera, leading to corruption of colours and contrasts as well as blurring.
For night mode: In night mode, the infrared light is used to achieve detailed images in darkness or with low ambient light.
IR Cut Filter
In order to avoid unwanted side-effects caused by infrared light (as part of the natural ambient light) during image recordings in daylight mode, an IR Cut Filter is installed in front of the sensor. The filter is meant to prevent the incidence of light onto the image sensor. Also, there is the IR Cut coating. This method realises the IR Cut Filter by applying a special coating to the lens.
ICR function for Day/Night switching
(ICR = IR Cut Filter mechanically removable)
Through the use of the ICR function a real* Day/Night functionality of the camera can be realised.
Using a so-called filter shifter, the IR Cut Filter can be swivelled in, which means that in day mode the IR Cut Filter is moved in front of the sensor in order to block out the interfering infrared light. In night mode the IR Cut Filter is moved away so that IR light may pass through.
IR correction
With IR corrected optical assembly, the lens is developed and manufactured so that the IR radiation is corrected before hitting the sensor.
This means that in daylight mode, IR corrected lenses also need an IR Cut Filter. Since even the best IR Cut Filters are not able to block all the IR radiation, the remaining IR rays that strike the sensor are corrected, hence an optimal image quality can be achieved.
NOTE: Only IR corrected lenses are suitable for use with IR lighting!
* There are cameras with an electronic (virtual) Day/Night functionality. Thereby, switching from day to night mode is only done virtually by adjusting some parameters of the AE (»Automatic Exposure«) Presets. The image is displayed in black and white. The IR Cut Filter cannot be removed on cameras with electronic Day/Night function. Therefore, the filter blocks out the IR light in night mode, when it is actually needed.
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