Luoyang Yuboo Testing Technology Co., Ltd.
Eight common optical parameter detection techniques for LED lamps。
Release Time:
2023-06-18 23:54
Optical parameter detection of LED light sources
Optical parameter detection of LED light sources
1. Photometry
The intensity of light, also known as the intensity of light, refers to the amount of light emitted at a certain angle. According to the CIE127 standard, the inverse square law is not applicable to light-emitting diodes due to the concentration of light. CIE127 proposes two conditions for measuring the average normal light intensity: measurement condition A (far-field condition) and measurement condition B (near-field condition), both of which are 1cm2. Generally speaking, the luminous intensity is measured using standard condition B.
2. Luminous flux and luminous efficiency detection
Light flux is the total amount of light emitted by a light source, which is the amount of light emitted. There are mainly two types of inspection methods:
(1) Integrated methods
And ignite the standard lamp and the tested lamp in sequence in the integrating sphere, and the readings on the photoelectric converter are Es and ED, respectively. Known standard light source flux Φ At s, the flux of the measured lamp Φ D=ED ×Φ S/Es. The integration method adopts the principle of "point light source", which is easy to operate, but is affected by the deviation of standard and measured lamp color temperature, resulting in significant measurement errors.
(2) Spectral method
Using spectral energy P（ λ) The distribution calculates the luminous flux. Using a monochromator, measure the spectrum of the light bulb from 380 nm to 780 nm in an integrating sphere, and then measure the spectrum of the measured light under the same conditions, comparing and calculating the luminous flux of the measured light bulb.
Luminescence efficiency is the ratio of the luminous flux emitted by a light source to the power consumed, and is often measured using a constant current method for LED luminous efficiency.
3. Spectral characteristic detection
The detection of its spectral characteristics includes spectral power distribution, color coordinates, color temperature, color rendering index, and other content.
The spectral power distribution represents that the light of a light source is composed of multiple wavelengths of color radiation, and the radiation power of each wavelength is also different. This difference in order with the wavelength is called the spectral power distribution of the light source. Obtained by comparing the light source with a spectrophotometer (monochromator) and a standard lamp.
Color coordinates represent the number of luminous colors of a light source in a numerical way on a coordinate map. There are many coordinate systems for color coordinate maps, commonly using X and Y coordinate systems.
Color temperature is a measure of the number of colors (appearance colors) that a person sees on a light source's color chart. When the light emitted by a light source has the same color as the light emitted by a blackbody at a certain temperature, it is called color temperature. Color temperature in light is an important parameter that describes the optical properties of a light source. The relevant theory of color temperature originates from blackbody radiation, and the color coordinates of the light source can be obtained from the color coordinates containing blackbody trajectories.
The color rendering index represents the amount of light emitted by a light source that accurately reflects the color of the object being illuminated, usually represented by Ra, which is the arithmetic mean of the color rendering index of the light source for eight color samples. The color rendering index is an important indicator of the quality of light sources, which determines the application range of light sources. Improving the color rendering index of white LED is an important issue in the research and development of LED.
4. Strength distribution determination
The relationship between the variation of light intensity with spatial angle (direction) is called the false light intensity distribution, and the closed curve connected by this distribution is called the light intensity distribution curve. Due to the large number of measurement points, each point needs to undergo data processing, and automatic distribution photometers are generally used for measurement.
5. The influence of temperature on the optical properties of LED
Temperature has an impact on the optical performance of LEDs. Many experiments have shown that temperature has an impact on the emission spectrum and color coordinates of LEDs.
6. Ground brightness measurement
The brightness of a light source in a certain direction is the luminous intensity per unit projected area in that direction. Generally, surface brightness is measured using a surface brightness meter or a aiming type brightness meter, which has two parts: the aiming light path and the measuring light path.
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