At present, high-power white LEDs are generally used in LED lighting products, which mainly use blue LED chips and yellow phosphors for light conversion, that is, directly coat the surface of the chip with a mixture of phosphors and silica gel. The layer thickness is difficult to control, so the spatial color distribution of the outgoing light is not uniform, that is, the luminous color is different in different directions. LED lamps are generally composed of multiple LEDs, and the phosphor is close to the core.
The temperature rise leads to the deterioration of the performance of the phosphor, and the uneven heat dissipation of the lamps will also make the temperature of each area inconsistent, which will lead to differences in the color of the LED light in each area, and there will be obvious spatial color unevenness. This phenomenon will seriously affect The lighting effect has a particularly serious impact on indoor lighting. Therefore, it is necessary to characterize and measure the spatial color non-uniformity of LED lamps. With the development of LEDs, outdoor lighting gradually enters indoor lighting and enters the application field. It is necessary to have a small-scale distributed photometric and colorimetric measurement instrument, which can quickly and synchronously measure the photometric and colorimetric space distribution of LED light sources.
Measurement principle
Traditional horizontal goniocolorimeter, in testing the (spatial) intensity distribution of a luminaire or light source. It is widely used in the total luminous flux and the photometric probe. The light source or lamp to be tested rotates around its own photometric center, and selects appropriate angular intervals to measure in the area where the emitted light reaches the entire angle, as shown in the figure. The chromaticity distribution measurement of the caliber 4mm pocket colorimeter in this paper is to install a chromaticity measurement device on the original distribution colorimeter Integrate the photometric chromaticity probe to replace the original photometric probe to realize the function of measuring light intensity distribution and chromaticity distribution synchronously.

System design
Use the absolute method to measure the total luminous flux, light intensity distribution, and chromaticity distribution of the light source.
The location requirements for LED light sources are very strict. Because of the more precise distributed photometric color. The degree measurement system is based on the measured light source according to the established light incident direction. Designed, assuming that the position of the lamp under test is not installed properly, it will inevitably lead to the actual light. The incident direction deviates from the set ray incident direction, which inevitably leads to the final number of tests deviations occurring. Therefore, the position of the light source has a significant effect on the whole test system and the experimental results. It must be ensured that the geometrical optical path is consistent with the actual optical path under test. The laser positioning technology is used in the test system to ensure the collimation characteristics of the optical path.
The handheld color meter simultaneously measures the photometric and chromatic signals of the LED light source, the system software can not only display the light intensity distribution curve and illuminance curve, but also calculate and display. It measures the distribution characteristics of the chromaticity coordinates and correlated color temperature of the LED light source, so its intuitive photometric and chromaticity characteristics are beneficial to the user’s analysis and sorting of the LED light source.
In conclusion
- For the design of small and low-power LED light sources, the tested sample can be measured from a single LED package to an LED module, as well as small LED lamps. The required test space is small. The optical path distance of the basic configuration is about 3 m, and the cost is relatively low. Reduced, simple test hardware requirements, ideal for enterprise use.
- Effectively integrate photometric and colorimetric probes, and keep the size of the integrated probe consistent with the original photometric probe, realize simultaneous parallel measurement of distributed photometric and distributed colorimetric data, and effectively improve test efficiency.
- The test device avoids the use of a reflective mirror, which can eliminate the measurement error caused by the mirror polarization of the general distributed colorimeter, and is especially suitable for the measurement requirements of polarized lamps and light sources.