Linear variable optical filter-based ultraviolet microspectrometer

Abstract

An IC-compatible linear variable optical filter (LVOF) for application in the UV spectral range between 310 and 400 nm has been fabricated using resist reflow and an optimized dry-etching. The LVOF is mounted on the top of a commercially available CMOS camera to result in a UV microspectrometer. A special calibration technique has been employed that is based on an initial spectral measurement on a xenon lamp. The image recorded on the camera during calibration is used in a signal processing algorithm to reconstruct the spectrum of the mercury lamp and the calibration data is subsequently used in UV spectral measurements. Experiments on a fabricated LVOF-based microspectrometer with this calibration approach implemented reveal a spectral resolution of 0.5 nm.

Two-groove narrowband transmission filter integrated into a slab waveguide

“…LVF is a bandpass filter that is intentionally wedged in one direction, providing a position-dependent dispersive optical element. Typically, LVF corresponds to a Fabry-Pérot etalon with varying thickness between two Bragg reflectors [21][22][23][24]. On the basis of the proposed TGPF, a waveguide-integrated LVF can be created, in which the spectral shift of the transmittance peak can be achieved by changing one of the parameters of the structure, e.g.…”

Simulation of spectral filters used in hyperspectrometer by decomposition on vector Bessel modes

“…In this paper a hyperspectrometer based on the use of spectral filters is considered [7]. Hyperspectrometers containing filters with variable spectral characteristics are discussed in [8][9][10][11].…”

Bandwidth-variable tunable optical filter unit for illumination and spectral imaging systems using thin-film optical band-pass filters

“…1,2 For this type of monochromator, the transmitted intensity decreases with decreasing bandwidth in a greater than linear manner that is approximately proportional to the square of the bandwidth for a given light source diameter, 1 limiting its applicability to high intensity illumination systems. For spectral imaging, diffraction-based monochromators require a scanning unit, 2 which is a limitation that can be overcome by using other filter types such as acousto-optic tunable filters, 2,5,6 linear variable optical filters, 2,5,7,8 or liquid-crystal tunable filters. 2,5,9,10 For most of these filter types, however, either bandwidth or central wavelength can be adjusted, but not both, 6, 11 the tuning range of the bandwidth or central wavelength may be limited, 7,12 or the transmission characteristics depend on the position of the incident light on the filter.…”

“…2,5,9,10 For most of these filter types, however, either bandwidth or central wavelength can be adjusted, but not both, 6, 11 the tuning range of the bandwidth or central wavelength may be limited, 7,12 or the transmission characteristics depend on the position of the incident light on the filter. 7,8 Cholesteric liquid crystals (CLCs) exhibit reflection properties that depend on the angle of incidence, polarization, electrical or magnetic field, temperature, radiation, or mechanical pressure. [13][14][15][16][17][18] CLCs were used to demonstrate a) Author to whom correspondence should be addressed.…”