Analysis method of noise power spectrum for medica

Authors: Katsuhiro Ichikawa Yoshie Kodera Aya Nishimura Mikio Hasegawa Naohiro Kimura Akihiro Takemura Kosuke Matsubara

Publish Date: 2008/07/01

Volume: 1, Issue: 2, Pages: 201-207

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Abstract

We investigated methods of analyzing the noise power spectrum NPS measurement for medical liquid crystal displays LCDs Uniform images displayed on the LCDs were imaged with a highperformance digital camera equipped with a closeup lens and then the NPSs were calculated from the image data by means of several analysis methods In a method using the 2D fast Fourier transform FFT with a 256 × 256 pixels data segment basic method we examined the efficacy of a background trend correction BTC and a Hanning windowing process used for reducing the spectral estimation errors in the Fourier analysis To improve the frequency resolution of the basic method we examined two 2D FFT methods by using 512 × 512 and 1024 × 1024 pixel segments In addition we studied a 1D FFT method with 1024point 1D noise profiles 1D method In these three methods the BTC by a secondorder polynomial fit and Hanning windowing were commonly applied A 3megapixel MP and a 5MP monochrome LCD were employed for evaluating the respective methods Also a prototype 5MP LCD equipped with a new antireflection surfacecoated panel was compared with the conventional 5MP LCD The Hanning windowing process was indispensable for avoiding the spectral leakage errors caused by the pixel structures of the LCD Sufficient frequency resolution was obtained by the 2D FFT method with the 1024 × 1024 pixels segments and the 1D method The method which provided the most reliable NPSs was the 1D method with which the BTC was achieved successfully

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