subject: Principle And Application Of Infrared Light [print this page] I. Principle and application of infrared light
(A) of the infrared light emitting diode (LED) principle
Infrared light is infrared light emitting diode (LED) matrix. Infrared light-emitting diodes by the infrared radiation radio efficient material PN junction, plus the forward bias injection current to the PN junction infrared light excitation. Spectral power distribution for the center wavelength of 830 - 950nm, about half-peak bandwidth is about 40nm. It is the narrow distribution, as an ordinary CCD camera can feel the range of black and white. The biggest advantage is completely non-red violence, (with 940 ~ 950nm wavelength infrared tube) or only weak red bursts (using 850nm wavelength infrared control); also has long life characteristics.
The infrared light using light-controlled soft-switching circuit, to reduce the impact of state transition of its work to extend the life of infrared light.
(C) constant current regulator circuit
To compensate for winter and summer, infrared light infrared light radiated power differences, the infrared light used constant current regulator circuit, so that infrared light-emitting diode optical power and stability, to improve the use of infrared light effect, prolonging the service life.
(D) the selection and use of infrared light
Infrared lamps to choose the most important question is infrared light and cameras, lenses, protective cover, such as sets of power supply. Some people buy a finished camera, lens, protective cover, power supply, even after installation before considering to buy infrared light, which is not correct, when should design comprehensive consideration of all equipment, infrared illumination it as a night control systems engineering design, as. When considering the complete sets, with particular attention to the following questions:
1. Use of black and white camera or a special color camera
CCD image sensor with a wide light-sensitive spectral range, including not only the visible spectrum of its light-sensitive area, but also extend to the infrared region, using this feature, you can no visible light at night where, with auxiliary IR illumination for CCD image sensor clear imaging device. Ordinary color camera to be able to transmit color signals, the output signal from the CCD device to separate green, blue and red color video signal, composing the color television signal, its spectrum is only sensitive in the visible region, therefore does not apply infrared light . Day & Night Camera (color day / night, black and white) is also possible to use one type of infrared light, which uses two CCD switch or using a CCD using digital circuit switching to achieve, but generally have high black and white illumination, or color on the color adversely affect the other shortcomings. As for the infrared camera infrared illumination color sensitivity 4 times higher than the average over the camera, higher manufacturing costs and the lower will be the night trends.
2. Requested to use low-light cameras
The most low-light camera photo scene when the brightness is low to a certain extent, Er Shi camera video signal output level
Low to a specified value when the scene brightness value. Determination of this parameter, but also specified the size of the lens aperture F. To use the F1.2 lens, for example, when photography was the scene illumination values as low as 0.02Lux, the camera outputs a standard video signal amplitude 700mv amplitude of 50% -33%, claimed that the best illumination for the camera 0.02Lux/F1.2. Some camera manufacturers will be clearly set out the most when different illumination aperture F value of the selected camera when the minimum illumination requirements than infrared light, infrared light of the effective distance will be some impact. To remind the user that the camera technology on the market performance marked the most illumination, there are two anomalies, one is the subject of camera manufacturers the most illumination is called the "target surface illumination," that CCD image sensor The light intensity, lower than the scene illumination is about 10 times; the other is, some camera manufacturers or vendors false minimum illumination.
