This thesis presents new designs for a linear variable filter (LVF) and discusses theirmanufacture using drum-based microwave plasma-assisted pulsed DC magnetron reactivesputtering. By using this deposition method, LVF samples for both the visible and nearinfraredbands are manufactured, and spectroscopic measurements are used to characterize theLVF samples. It is demonstrated that deposition times can be reduced to a few days ratherthan the 6 weeks of alternative designs and methods described in the literature. The drumbasedtool used here is shown to allow multiple copies of the filters to be manufactured in onerun, increasing potential throughput by at least an order of magnitude over alternativedeposition techniques.An innovative miniaturized spectrometer design is proposed using the LVFs described in thisthesis and several iterations are manufactured and tested. These miniaturized spectrometersare suitable for portable and real-time monitoring applications. Compared with traditionalspectrometers, the manufacturing cost is relatively low, and the use of advancedmicroelectronic technologies opens up applications in chemical testing, food safety, materialanalysis, energy testing and other fields.The design and analysis of the LVFs is achieved using thin film design software (TFCalc).The designs are based on narrow-bandpass filters and wide blocking filters, deposited on frontand back surfaces of suitable substrates using the drum-based microwave plasma assisted DCmagnetron sputtering thin film deposition system (Microdyn). Two particular LVFs aredesigned, one with a working range of 450 nm - 900 nm and linearity of 11.14 nm / mm foruse in the visible light band and another with a working range of 1.5 μm - 2.5 μm andlinearity of 42.68 nm / mm for use in the near-infrared band.Nb2O5 and SiO2 materials are selected as high and low refractive index materials respectivelyand their optical constants characterised by fitting to spectroscopic data for subsequent use inTFCalc.To fabricate linear variable filters, the deposited film thickness must vary linearly along thelength of the substrate. This is achieved by modelling the distribution of sputtered materialarriving at the substrate during the sputtering process used in the MicroDyn tool. Optimalmasking functions are designed using MathCad 15 scripts and successfully manufactured to fit the target holders. With this mask in place, single thin film layers of the selected materialsare shown to exhibit a linear trend in thickness over 44 mm lengths of glass and siliconsubstrates allowing the successful manufacture of the designed LVFs. Spectroscopicmeasurements at selected points along the lengths of the LVFs confirm the designedperformance, with the central wavelength deviating from linearity by less than 1% over the450 nm - 900 nm range and varying by a very satisfactory 10.8 nm/mm.The continuous nature of LVFs means that different sizes of the illuminating spot producedifferent degrees of an averaging or blurring effect on spectral results and this effect issimulated, analysed and quantified for various spot sizes using square-wave and Pearsonfunctions, with the Pearson VII function shown to give the best fit. This information can beused to improve the resolution of measurements. The full width at half maximum with anincident beam size of 0.4 mm is shown to be 11.2 nm.Solidworks is used to design a miniaturized-spectrometer device incorporating the LVF as thecore component, and 3D printing is used to manufacture practical spectrometers. An MCUcontrol module is designed for the miniaturized spectrometer and an interface program iswritten to be used in a PC with the Windows operating system. Finally, optical thin filmsamples are measured using the manufactured spectrometers and compared withmeasurements obtained with an expensive conventional spectrometer equipment. Best resultsare obtained with the third iteration of spectrometer design, based on a threaded screw insteadof 3D printed gears to scan the LVF past the single detector.Suggestions for future work and potential improvements are discussed.