• Journal of Sensor Science and Technology
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• v.16 no.5
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• pp.342-348
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• 2007

A high-speed signal processor for Fabry-Perot interferometric sensors using modified ramp modulation is implemented. The main idea for the signal processing is to find a modulation waveform that could induce a linear frequency change in a laser diode to linearize the relationship between the optical phase shift and measurand. It is found that the waveform could be modeled as the addition of a linear term and an exponential term. A signal processor adopting modified ramp modulation technique is implemented and evaluated to find linearity, drift and random walk of $<{\pm}1.5%$, $0.4^{\circ}C$, $5.28{\times}10^{-4}^{\circ}C/{\sqrt{Hz}}$.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.2 s.308
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• pp.40-47
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• 2006

This paper proposes a multitoning method using threshold modulation of MJBNM(Modified Jointly Blue Noise Mask) for banding artifacts reduction. As banding artifacts in multitoning appear as uniform dot distributions around the intermediate output levels, such multitone output results in discontinuity and visually unpleasing patterns in smooth transition regions. Therefore, to reduce these banding artifacts, the proposed method rearranges the dot distribution by introducing pixels in the neighborhood of output levels that occurs banding artifacts. First of all principal cause of banding artifacts are analyzed using mathematical description. Based on this analytical result, a threshold modulation technique of MJBNM which takes account of chrominance error and correlation between channels is applied. The original threshold range of MJBNM is first scaled linearly sot that the minimum and maximum of the scaled range include two pixel more than adjacent two output levels that cover an input value. In an input value is inside the vicinity of any intermediate output levels produce banding artifacts, the output is set to one of neighboring output levels based on the pointwise comparison result according to threshold modulation parameter that determines the dot density and distribution. In this case, adjacent pixels are introduced at the position where the scaled threshold values are located between two output levels and the minimum and maximum threshold values. Otherwise, a conventional multitoning method is applied. As a result, the proposed method effectively decreased the appearance of banding artifacts around the intermediate output levels. To evaluate the quality of the multitone result, HVS-WRMSE according to gray level for gray ramp image and S-CIELAB color difference for color ramp image are compared with other methods.