8 common detection techniques for LED lamps
Date: 2015-11-10 08:17:56 Hits: 577

LED light source and traditional light source have great difference in physical size and luminous flux, spectrum and light intensity spatial distribution. LED inspection cannot copy the traditional light source testing standards and methods. Xiaobian below for you to introduce common LED lamps detection technology.

1, the luminescence intensity of light intensity detection

i.e.light intensity detection

LED lighting optical parameters, refers to radiation at a particular point of view in the amount of light. Because the LED light is concentrated, in close condition does not apply inverse square law, CIE127 standard measurement of light intensity is proposed to measure A (far field), B (near field measurement conditions) two measuring the average normal intensity condition detector 2 conditions are 1cm2 product. Normally, the standard conditions B are used to measure the luminous intensity.

2, luminous flux and light effect detection

flux is the sum of the amount of light emitted by the light source, the light quantity. The detection method includes the following 2 types: (1)

integral method. The standard lamp and the measured lamp are successively lit in the integrating sphere, and the readings in the photoelectric converter are Es and ED, respectively. The luminous flux of the standard lamp is known as Φ s is the luminous flux of the tested lamp; D=ED× Φ Φ s/Es. The integral method uses the principle of “ point light source ”, and the operation is simple, but the measurement error is larger due to the influence of the color temperature deviation between the standard lamp and the tested lamp.

(2) spectrophotometry. The luminous flux is calculated by spectral energy P (&lambda) distribution. The monochromator is used to measure the 380nm - 780nm spectrum of the standard lamp in the integrating sphere, then the spectrum of the lamp under test is measured under the same conditions, and the luminous flux of the measured light is calculated. Luminous flux

light effect for light and power consumption ratio, usually by constant light effect flow measurement LED. The spectral characteristics of

3 are measured by

LED, including spectral power distribution, color coordinates, color temperature, color rendering index and so on.

spectral power distribution of light source is that many different wavelength color radiation and radiation power of each wavelength is different, the different wavelength sequence is called the spectral power distribution of light source. Using spectral photometer (monochromator) and standard light, the light source was compared and measured.

color coordinate is digitally expressed in the amount of light emitting color diagram. A coordinate diagram showing colors has many coordinate systems, usually using the X and Y coordinate systems.

color temperature is said visible light color table (appearance color) amount. When the light emitted by a light source is the same as the light emitted by an absolute black body at a certain temperature, the temperature is the color temperature. In the field of illumination, color temperature is an important parameter to describe the optical characteristics of light sources. The theory of color temperature is derived from black body radiation, which can be obtained from the color coordinate of the black body trajectory through the color coordinates of the light source.

color index shows that the light emitted by the light source on the illuminated objects correctly reflect the amount of color, usually with the general color rendering index of Ra, Ra is the source of 8 color color index arithmetic mean value. Color rendering index is an important parameter of light source quality. It determines the application range of light source, and improving the color rendering index of white light LED is one of the important tasks of LED research and development.

4, the light intensity distribution test

intensity with the space angle (direction) relationship and become known as the fake intensity distribution, the distribution of which are connected by a closed curve called intensity distribution curve. Since there are many measuring points and each point is processed by data, an automatic distributed photometer is usually used for measurement.

5, the temperature effect on the optical properties of LED

temperature will affect the optical properties of LED. A large number of experiments can show that temperature affects LED emission spectrum and color coordinates. The brightness of

6, surface brightness measurement

light source in a certain direction of the luminous intensity in the direction of the unit area of the projection light source, the general use of surface brightness meter, aiming to measure the brightness of the surface brightness meter, there are 2 parts aiming light path and optical path. Measurement of electrical parameters of

LED and other

lamps performance parameter measurement of

1, LED lighting electrical parameters including positive and negative voltage and reverse current, related to the LED lamp can work, is one of the basic performance of the LED lamp decision basis. There are 2 kinds of electrical parameters measurement for LED lamps, that is, the voltage parameters are tested under certain conditions, and the current parameters are tested when the voltage is certain. Specific methods are as follows: (1)

forward voltage. A positive current is applied to the LED lamp to be detected and a voltage drop is generated at both ends. Adjust the current value to determine the power supply, record the relevant readings on the DC voltmeter, that is, the forward voltage of the LED lamps. According to relevant common sense, LED is less resistance when forward conduction, and it is more accurate using ammeter external connection method.

(2) reverse current. A reverse voltage is applied to the detected LED lamp, and the regulated power supply is regulated. The reading of the ammeter is the reverse current of the LED lamp to be measured. The same as measuring the forward voltage, because the LED has a greater resistance to reverse conduction, the ammeter is used to connect it. The thermal characteristics of

2 and LED lamps and the thermal characteristics of

LED have important influence on the optical and electrical characteristics of LED. Thermal resistance and junction temperature are the major thermal characteristics of LED2. Thermal resistance refers to the thermal resistance between PN junction and the surface of the shell, i.e., the ratio of the temperature difference between the heat flow channel and the dissipated power on the channel. The junction temperature is the temperature of the PN junction of the LED.

method for measuring LED junction temperature and thermal resistance are generally: infrared micro spectroscopy, imaging method, electrical test method, optical scanning method, thermal resistance. The surface temperature of LED chip used as the junction temperature of LED is not accurate enough by infrared temperature microscope or micro thermocouple. The electrical parameter method

is widely used by LEDPN junction forward voltage drop and PN junction temperature characteristics of linear relationship, by measuring the different temperature difference of forward voltage drop LED junction temperature.

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