Will my camera see infrared illumination?
If your camera is B&W or has a B&W mode it will see infrared illumination to some degree. The quality of the images will depend on the camera’s capability of reading the specific IR wavelength on the scene. Do not be misled by lux level specifications. Not all low lux cameras are efficient at reading the infrared part of the ‘electromagnetic spectrum’. Ensure that you determine the ‘spectral response’ of the camera to confirm its capabilities for viewing infrared. If your camera has an adequate spectral response at 950nm then you can be assured it will see infrared up to this wavelength. Most infrared illuminators emit IR light in the 730nm to 950nm range.
How do I stop my camera from switching back to colour when the infrared illumination activates?
By using a connection in the illuminator power supply called the ‘photocell relay output’. This sends a signal to the camera to override its automatic switching level. The camera will then switch on and off at the same time as the illuminator.
My image is blurred when I use infrared illumination at night but is sharply focused during the day. How can I remedy this problem?
The lens used on the camera focuses different wavelengths of light through a range of distances back toward the camera sensor. As infrared illumination is further from the central part of the visible spectrum, most standard lenses have not been designed to cope with this wider range. To eliminate this problem use a zero focus shift or IR corrected lens, which has a coating applied to the optic to allow both the colour and infrared wavelengths to be focused correctly on the sensor.
Is it possible to remotely trigger infrared illumination?
If continuous night-time surveillance of an area is not required, most infrared illuminators can be triggered via alarm outputs from the likes of contact and PIR sensors to give illumination only when required. This can considerably reduce the lamp’s power consumption and extend its operational life.
If my camera has frame integration, do I need additional infrared illumination?
Frame integration involves the addition of frames of video on top of each other, essentially allowing more photons to land on the camera sensor. However as the camera’s exposure time is increased, it becomes more difficult for the camera to image moving objects. A good example of this is when a compact digital camera is used without a flash at night. The image is usually very blurred due to the photographer’s hand shaking. If infrared illumination is used with a security camera, this is essentially the same as using the compact digital camera with a flash – the camera will no longer need to integrate, hence objects moving in the scene can be resolved without motion blur.
Why should I use infrared lighting instead of conventional visible lighting?
Infrared illumination can provide unobtrusive, even illumination which dramatically improves the performance of CCTV systems during the vulnerable hours of darkness, without drawing attention to the location or disturbing the surrounding area with unwanted light pollution. Visible lighting systems have not been designed to provide “even illumination” and therefore make it very difficult to get a clear picture or to use motion detection. Infrared illumination has much lower operating costs than equivalent conventional lighting and can illuminate further. A single 220W UF500 infrared lamp will effectively illuminate distances to 170m,and a dual system provides even illumination to 240m. Conventional street lamps throw 80 per cent of their light to within 12m of the base of the pole. It would be cost prohibitive to attempt to achieve even illumination with conventional street lamps or metal halide security lamps.
When should I use an Integrated Day Night camera (IDN)?
Integrated Day Night cameras are particularly effective for shorter range projects (up to 70m), applications with short separation installation points, or where the installer does not want to have to integrate camera, lens and illumination himself. It is also advisable to use IDN when the visual impact of the surveillance equipment is required to be minimal, or where installation space is at a premium. The components of IDN products have been specifically designed to work together. This usually means bringing together an infrared sensitive camera and illumination array, incorporating a zero focus shift lens and putting the full package together in an IP rated and cable managed housing. Use of IDN products can significantly reduce the installation and set-up time of a CCTV system.
Which wavelength of infrared illumination should I use?
Infrared illumination used within the security industry is available in three variations of wavelength, 730, 850 and 950nm. The 730nm wavelength produces a red glow similar to that given off by a traffic light and should be used when maximum range is required. Most day/night and monochrome cameras are sensitive to this wavelength. 850nm illumination is described as ‘semi-covert’ infrared and produces a very dull red glow. Some day/night and monochrome security cameras are sensitive to this wavelength although the more cost-effective sensors will struggle. Finally, 950nm is completely covert, ie invisible to the human eye. This form of infrared illumination requires a very sensitive camera with a high spectral response in the infrared region of the sensor’s quantum efficiency curve.
Why can’t colour cameras see infrared illumination?
Colour cameras have what is known as a ‘mosaic’ or ‘Bayer filter’ in front of the camera sensor. This filter is made up of three colours – red, green and blue, or, more usually, yellow, cyan and magenta. Each pixel is covered by one of these coloured panels and as such will only allow light of that particular colour to pass through to the sensing device. As infrared illumination does not fall into these particular colour bands, most is discarded. Dual mode ‘movable filter’ cameras navigate this problem by having the ‘Bayer filter’ removed from the front of the sensor when the video signal falls below a threshold value.
Should I specify bulb-based or LED illumination?
Bulb-based illuminators are usually the best option for large projects requiring multiple lamps. LED based lamps will eventually burn out meaning the entire unit needs to be replaced. This is an issue rarely considered prior to installation but which on large projects can lead to a massive cost when all the lamps on site need to be replaced. Bulb-based illuminators have an indefinite lifetime as the bulb can be replaced as part of a customer’s annual service contract. The housing and expensive filtering systems do not need to be replaced. LED illuminators have a typical lifetime in excess of five years and should be used where regular servicing may not be possible or wanted. Small LED units can also cover short distances where bulb based units may be too powerful.
