CHARACTERIZATION AND ANALYSIS OF SPECTRAL REFLECTANCE OF VARIOUS INTERIOR MATERIALS DUE TO LED LIGHTING WITH COLOR TEMPERATURE VARIATIONS

• Main Author: Ajrina, Zhafirah
• Format: Theses
• Language: Indonesia
• Subjects: Teknik (Rekayasa, enjinering dan kegiatan berkaitan)
• Online Access: https://digilib.itb.ac.id/gdl/view/56837
• Institution: Institut Teknologi Bandung

The current 4.0 industrial revolution, which is related with the era of the Internet of Things (IoT), also affects LED-based lighting systems. Wireless networks allow people to be connected, remotely managing indoor lighting scenes via tunable LEDs. Meanwhile, the appearance of indoor lighting is also determined by the spectral reflectance of the interior material surfaces. With tunable LEDs, it is possible to vary the correlated color temperature (CCT) of the source; however, it is relatively unknown whether the change of CCT shall also vary the spectral reflectance of materials. Therefore, this study aims to identify and analyze the spectral reflectance of various interior material samples due to various CCT from a tunable LED light source, measured with an integrating sphere. Moreover, the study also aims to recommend the most appropriate CCT value for measuring the spectral reflectance of each color sample and to determine the color samples that have the most robust appearance when illuminated by different LED spectra. The reflectance measurements were conducted using a low-cost, self-assembled integrating sphere with the diameter of 30 cm. It has 3 ports, each for the sample, the source’s entrance, and the detector (spectroradiometer). In this study, a spotlight LED with CCT of 3000K was applied to measure the reflectance of each sample. The diffuse reflectance measurement of the material is carried out by placing the sample perpendicular to the light source. The spectral reflectance value, ?(?)s of the sample can thus be determined from spectral irradiance reading on the detector port. The analysis is performed by predicting the spectral reflectance appearance by the spectral exitance Me(?), under the standard illuminant E and under Philips Hue tunable LED lamp with 10 variations of CCT values (2000-6500 K). Spectral power density (SPD) of the ten CCT variations were determined by direct measurement in a dark chamber. Ten color samples of painted 9mm plywood and ten color samples of wallpapers were introduced and analysed. Moreover, chromaticity difference in the form of ?u'v' was calculated to compare the spectral exitance of each sample under the standard illuminant E and under the ten spectra of the tunable LED. Analysis of the spectral reflectance of each sample was performed for the wavelength range of 420-740 nm. It was found that there were 5 colors for both sample groups that had the smallest changes of chromaticity difference (?u'v') at CCT below 5000 K; i.e. yellow, beige, red, pink, and brown. Moreover, there are 5 colors for both sample groups that had the smallest changes at CCT below 5000 K; i.e. dark blue, dark green, light green, gray, and light gray. Spectral reflectance of painted plywood and wallpaper of yellow, beige, red, pink, brown colors can be accurately measured under the tunable LED with CCT 5000 K. Meanwhile, dark blue, dark green, light green, gray, light gray color samples are best to be measured under the tunable LED with CCT 5500 K. Based on the plot of the chromaticity coordinate in the diagram CIE 1976, the smallest change in the chromaticity coordinate for the two materials is obtained, namely the dark green color sample and the 3D light green color sample for wall paint and wallpaper materials, respectively. The two sample colors have predictive appearances that tend to be consistent when illuminated under the tunable LED with various CCTs.