Infrared light according to its infrared light radiation mechanism is divided into semiconductor solid light (infrared emitting diode) infrared light and heat radiation infrared light two. Its principle and characteristics we introduce as follows:
(I) Infrared emitting diode (LED) infrared lamp
The light emitting body is composed of an infrared light emitting diode matrix. The infrared emitting diode is made of a material with high infrared radiation efficiency (commonly used gallium arsenide GaAs) to form a PN junction, and a forward bias is applied to inject the current into the PN junction to excite the infrared light. Spectral power distribution is center wavelength 830 -- 950nm, and the half-peak bandwidth is about 40nm. It is a narrow-band distribution, which is the range that a common CMOS black-and-white camera can experience. Its greatest advantage is that it can be completely free of red storms (using infrared tubes at 940 to 950 nm wavelengths) or only weak red storms (red storms have visible red light) and long life.
The emission power of infrared light emitting diodes is expressed in terms of irradiance μW/m2. In general, the infrared radiant power is proportional to the forward operating current, but near the maximum rated value of the forward current, the temperature of the device rises due to the heat loss of the current, and the optical emission power decreases. Infrared diode current is too small, it will affect the radiated power to play, but the operating current is too large will affect its life, and even make the infrared diode burned.
Infrared light-emitting diodes have very similar volt-ampere characteristics to ordinary silicon diodes. When the voltage crosses the positive threshold voltage (approximately 0.8V), the current begins to flow and is a very steep curve, indicating that its operating current is very sensitive to the operating voltage. Therefore, it is required that the working voltage is accurate and stable, otherwise it will affect the performance and reliability of the radiation power.
The increase in the radiated power of the infrared light emitting diode with the ambient temperature (increased ambient temperature caused by its own heat generation) will reduce its radiated power. Infrared lamps are particularly long-range infrared lamps. Heat consumption is a problem that should be considered when designing and selecting.
The maximum radiation intensity of the infrared light emitting 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 angle at which the radiation intensity is 50% of the maximum is called the half-intensity radiation angle. The infrared emitting diodes of different package process models have different radiation angles.
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