SPECTRAL MEASUREMENT AND CLASSIFICATION IN THE ERA OF BIG DATA

The measurement and classification of light is essential across many scientific disciplines. Devices used to measure light range from the highly precise scanning spectroradiometers to the more practical compact multichannel filter-array type imaging sensors and the ubiquitous RGB pixel. While there have been numerous successful efforts to reconstruct spectrum from RGB, RGB-to-spectrum reconstruction has historically been limited to natural scenes and other edge cases under strict constraints. However, information theory and recent advances in deep learning have shed new light on the vast amount of redundancy contained within data collected in the natural world, including light. In this paper, we will investigate how analytic methods can help map high dimensional spectra data to a low-dimensional feature space with minimal inductive bias. Through a better understanding of the intrinsic dimension of the data, we can use the features expressed in this representation to exploit regularities and make tasks like data compression, measurement and classification more efficient. The aim of this analysis is to help inform how and when low-dimensional representation of spectra is useful in practice for designing compact sensors as well as for lossy data compression and robust classification.

TiO2/ZnO PHOTONIC CRYSTAL PREPARED BY SPRAY PYROLYSIS METHOD: APPLICATION TO MULTICHANNEL FILTER

Single-layer titanium dioxide (TiO2, ZnO, double-layer TiO2/ZnO and multilayer TiO2/ZnO/TiO2/ZnO were grown on ordinary glass substrate by ultrasonic spray deposition at 300∘C. Titanium chloride, zinc acetate and deionized water were employed as precursors. The ultraviolet–visible spectrometer spectra show that the quality of optical transmittance in visible wavelength range decreases as the number of bilayers increases. The crystalline phase of the thin films was identified through X-ray diffraction method with diffraction patterns scan used at 2[Formula: see text] from 10∘ to 90∘. From the DRX results, it is found that the crystallinity is enhanced when the number of TiO2/ZnO layers increased. From the 2D/3D atomic force microscopy (AFM) analysis, it is found that the surface of the films was covered by triangle-like particles. However, bilayer and multilayer TiO2/ZnO thin films show smooth and compacted surface roughnesses compared to single-layer TiO2 and ZnO, respectively. In addition to this experimental work, a multichannel filter based on TiO2/ZnO subphotonic crystals is suggested. The transmission properties of this filter have been investigated by means of the transfer-matrix method (TMM). The idea is to import a wedge of air with an apex angle as the defect layer to disturb the original periodicity of the oxide photonic crystal and generate some new kind of multichannel filtering properties.