The working principle of the camera with infrared light
Infrared emission diode (IR LED) infrared lamp principle is: by the infrared light-emitting diode matrix composed of light. Infrared emission diode from the infrared radiation efficiency of high materials (commonly used gallium arsenide GaAs) made PN junction, plus forward bias voltage to the PN junction injection current excitation infrared light. Spectral power distribution for the central wavelength of 830 ~ 950nm, half-peak bandwidth of about 40nm or so, it is narrowband distribution, for ordinary CCD black and white camera can feel the range. The emission power of the infrared light emitting diode is expressed by the irradiance μW / m2. The maximum radiation intensity of the infrared diode is generally in front of the optical axis and decreases with the increase of the angle between the radiation direction and the optical axis. The radiation intensity is 50% of the maximum value of the angle is called the half intensity radiation angle, that is, half power angle. The radiation angle of the infrared light emitting diodes of different packaging process models is different.
First, the characteristics of infrared and infrared light light is an electromagnetic wave, with the same nature as the radio waves. Its wavelength range is from several nanometers (1nm = 10-9m) to about 1mm (mm). The visible wavelength is from 380nm to 780nm, the wavelength of visible light from long to short into red, orange, yellow, green, blue, blue, violet, the wavelength is shorter than the purple light, the wavelength of visible light is only a part of the visible light, visible light Called ultraviolet light, the wavelength is longer than the infrared light called infrared light. Infrared light wavelength between 780nm ~ 1000μm, located between the radio and visible light. Infrared light according to its infrared radiation mechanism is divided into semiconductor solid light (infrared emission diode IR LED) infrared light and heat radiation infrared light two. At present in the CCTV infrared camera in the former use more.
Second, the infrared camera imaging principle In the night vision monitoring system, the conventional approach is to use the visible light, but this way there can not be hidden, easy to monitor the target and other shortcomings, so use less; the current hidden, scientific night vision monitoring Is the use of infrared camera technology. Infrared camera technology is divided into passive and active. Passive infrared camera technology is the use of any substance in the absolute zero (-273 ℃) are more than infrared radiation, the higher the temperature of the object, the more infrared radiation. The most typical of the cameras made with this principle is the infrared camera, but this special infrared camera is expensive and therefore limited to military or special occasions. The active infrared camera technology is the use of infrared light radiation "lighting" (mainly infrared light), the application of ordinary low-light black and white camera, color to black and white camera or infrared low-light color camera, feel around the scene and the environment reflected back to the infrared light to achieve Night vision monitoring. Active infrared camera technology is mature, stable, become the mainstream of night vision monitoring.
