Optimal pruning for selecting LEDs to synthesize tunable illumination spectra

Calibration of an illuminance meter is indispensable for accurate measurement of the illuminance of indoor lighting and daylight. In recent years, because of the phasing-out of incandescent lamps and their replacement with LED lamps, it has become difficult to obtain an incandescent type standard lamp to calibrate an illuminance meter. To replace the standard lamp method, we constructed an illuminance meter calibration system based on an LED-based spectrally tunable light source. The approximate CIE Illuminant A spectrum realized by the LED-based spectrally tunable light source was controlled at various illuminance values (800–10,000 lx). A test illuminance meter was calibrated by comparison against a reference photometer with the realized approximate Illuminant A spectrum. The illuminance values measured using the reference photometer and using the test illuminance meter in the calibration system agreed within 2.5% without reference plane correction of the test illuminance meter, and within 1% with reference plane correction. Reference plane correction depends strongly on the measurement distance and the illuminance meter structure. This study demonstrated that it can be improved. Therefore, we infer that an illuminance meter calibration method using an LED-based spectrally tunable light source is a promising means of overcoming difficulties posed by the phasing-out of incandescent standard lamps.

Section: Introductionmentioning

confidence: 99%

Illuminance meter calibration with an LED spectrally tunable light source

Godo

Tamura²,

Watari³

2020

“…This research has attracted more attention recently. [1][2][3][4] Several kinds of lamps have been used as light sources to simulate sunlight, such as halogen lamps and gas discharge lamps.…”

Section: Introductionmentioning

confidence: 99%

Solar spectrum matching using monochromatic LEDs

Jing-hui

Cao

et al. 2016

The possibility of a spectrally tunable solar-like light source is drawing attention with the development of LEDs. We researched the market of high-power, monochromatic LEDs and established a database with 103 kinds of LED by a new model. We used the database to match the solar spectrum in the wavelength range 380-780 nm. The optimal combination maximising the fit to the solar spectral curve was obtained. The trade-off relationship between the selection of LEDs and the fit was investigated in detail. The results show that the optimal combination contains 34 types of LED with a maximum correlation index R 2 of 88.67%. The value of R 2 reduces to 85.06% when the number of LED types is reduced to 20, but the R 2 value decreases sharply if the number of LED types is decreased to 16, with a R 2 of 79.97%.

“…The optimal selection of LEDs from a stack of commercially available LEDs, emphasising the selection method of optimal LEDs for realising the CIE standard illuminants and blackbody radiation at different colour temperatures, has also been discussed. 11 This is based on minimising the mean-squared-error of the synthesised SPDs and the SPDs of the standard illuminants. The norms of these SPDs are assumed to be 1.…”

Section: Introductionmentioning

confidence: 99%

Optimal radiant flux selection for multi-channel light-emitting diodes for spectrum-tunable lighting

Feng

et al. 2013

Self Cite

To synthesise a spectrum with a given radiant flux by multi-channel light-emitting diodes, different light-emitting diodes should have different radiant fluxes to maximise the light-emitting diode flux utilisation rate defined by the radiant flux of the light-emitting diode's contribution to the synthesised spectrum divided by the rated radiant flux of this light-emitting diode. The optimal rating radiant flux algorithm for each light-emitting diode is achieved by applying the normreducing process and full-search method to the norm region of the spectra. As a result, light-emitting diodes with a broader full-width half maximum, such as phosphor-converted light-emitting diodes, are usually set at a high power level and the rest of the light-emitting diodes can be set to either medium or low power levels. Furthermore, the high-power light-emitting diode can be decomposed to some low-power light-emitting diodes to reduce both heat generated and lightemitting diode price.