MTF measurement method for medical displays by using a bar-pattern image

Abstract

-A modulation-transfer-function (MTF) measurement method that uses a bar-pattern image for medical displays such as liquid-crystal displays (LCDs) and cathode-ray tubes (CRTs) has been investigated. A specific bar-pattern image on the display was acquired with a high-resolution singlelens reflex-type digital camera equipped with a close-up lens. The MTF was calculated from the amplitudes of the fundamental-frequency components, which were extracted from the profile data across the bar patterns by using Fourier analysis. Actual comparisons with the conventional line technique were performed for a medical CRT. The adequate accuracy and excellent reproducibility of the method were confirmed. Furthermore, unlike the line method, an advantageous feature which can use an input signal with sufficient amplitude was theoretically proved. Horizontal and vertical MTFs at the central position of the display area were measured up to the Nyquist frequency for several medical displays. From these measurements, this method has the capability to detect slight differences between the displays measured. This proposed method is useful in understanding and quantifying the medical display's performance due to excellent reproducibility and accuracy.

Overall noise characteristics of reduced images on liquid crystal display and advantages of independent subpixel driving technology

“…The MTFs of the LCD were measured using a bar-pattern image method proposed by Ichikawa et al 2 The close-up images of the displayed bar pattern were captured by a high-resolution single-lens reflex (SLR) digital camera (D80, Nikon Corporation, Tokyo, Japan) equipped with a close-up lens (Micro-Nikkor60 mm F2.8D, Nikon Co.). The camera has a charge-coupled device (CCD)-sensor array with a 3872 × 2592 elements and a contrast resolution of 12 bits.…”

“…Several researchers have already investigated and reported inherent image characteristics of various LCDs as modulation transfer function (MTF) and noise power spectrum (NPS), which are attributed to the matrix size, pixel-structure shape, aperture ratio, screen filter, etc. [1][2][3][4][5][6] Fur-ther, Bacher et al reported the observer-performance results of image characteristics on LCDs by using window setting and magnification. 7 In this study, we performed theoretical analyses for inherent image characteristics as well as the overall noise characteristics of displayed images on a LCD for varying magnifications.…”

Visual evaluation and usefulness of medical high-resolution liquid-crystal displays with use of independent sub-pixel driving technology

“…On granularity measurement, an estimation pattern image was displayed on the monitor and photographed with a single-lens reflex digital camera, and the WS in a 100 9 100 pixel homogenous area displayed at a specific brightness was calculated from the raw CCD data. These measurement methods were adopted as simple, accurate methods for the physical evaluation of LCD panels [5,6].…”

Investigation of physical image characteristics and phenomenon of edge enhancement by phase contrast using equipment typical for mammography

“…Ichikawa et al measured the image characteristics of liquid crystal displays using a similar digital camera, and they demonstrated that the spatial resolution of the camera was sufficient to measure MTFs of objects. [18][19][20][21][22] The camera has charge coupled device ͑CCD͒, sensor arrays of 3008ϫ 2000 and a contrast resolution of 14 bits. The sampling pitch of the camera is about 0.08 mm on the plane of the film if the lens is adjusted with the highest magnification.…”