다색광전달함수를 사용한 컬러 LCD 모니터의 광학적 상평가법

To compare the modified signal-to-noise ratio (SNR*) of multifocal visual evoked potential (mfVEP) responses elicited by a cathode ray tube (CRT) and liquid crystal display (LCD) monitor in normal subjects. An LCD monitor and CRT monitor were luminance and contrast matched. Luminance stability and the effect of viewing angle on luminance and contrast was measured for both screens. The SNR* of mfVEP responses from 15 normal subjects was compared between the stimulators using repeated measures analysis of variance. The CRT monitor took 10 min from switch on to reach the desired luminance compared to 60 min for the LCD monitor. LCD luminance was sensitive to variations in ambient temperature, fluctuating by 10 cd/m(-2) over approximately 20-27 °C, whereas CRT luminance was stable. Luminance variation from the centre to the edge of the CRT screen was 8 % when viewed perpendicularly and 28 % when viewed at an angle of 25°, compared to 24 and 46 %, respectively, for the LCD screen. Contrast was >94 % and varied by <3 % across both monitors for both viewing conditions. There was no significant difference in SNR* between responses elicited by the two stimulators (p = 0.76). CRT and LCD stimulators elicited mfVEP responses with similar SNR* in normal subjects. This study highlighted practical issues with the use of LCD monitors as visual stimulators, particularly with regard to warm-up time, luminance stability and luminance uniformity.

The aim of this study was to examine whether 20-cm field-of-view (FOV) targeted reconstruction (TR) on contrast-enhanced (CE) chest computed tomography (CT) might improve the diagnostic value compared with simple zooming (SZ) from whole-thorax FOV images using a 2 million (2M)-pixel liquid crystal display (LCD) monitor. We prospectively evaluated 44 patients. SZ images were magnified from a FOV of 26-34 cm (mean 29.7 cm). Parameters were 512 x 512 matrix and 3 mm thickness and interval. Images were reconstructed using a soft-tissue kernel. Three radiologists evaluated contour, spiculation, notch, pleural tag, invasion, and internal characteristics of the lesions using 5-scale scores. We also performed a phantom study to evaluate the spatial resolution of images. The diagnostic value of the TR images was similar to that of the SZ images, with the findings identified in 88%-100% of the cases. Artifacts from high-density structures deteriorated the image quality in six (14%), and the SZ images were judged to be preferable in five of them. In the phantom study, there was little difference in spatial resolution between the two images. The SZ images from whole-thorax FOV on CE chest CT were similar in quality to TR images using a 2M-pixel LCD monitor.

Purpose: Liquid‐crystal display (LCD) monitors for medical use may not be always used under the same ambient lighting condition for calibration of the grayscale standard display function (GSDF). The purpose of this study is to clarify need for recalibration to the GSDF in different ambient lighting conditions. Method and Materials: An LCD monitor (two‐mega pixels, Radiforce GS220, Eizo, Japan) was used in this study. The calculated diffuse reflection coefficient of this LCD monitor was 0.0026 sr−1. This LCD monitor was calibrated to the GSDF including four ambient lighting conditions such as typical diagnostic reading stations (10 lx and 60 lx), hospital clinical viewing stations (250 lx), and operating rooms (400 lx) levels based on guidelines of the American Association of Physicists in Medicine task group (AAPM TG) 18. The maximum deviation from the contrast response was calculated at various tentative changes in ambient lighting conditions. Results: When the ambient lighting condition changed, the maximum deviation of contrast responses increased. The degree of the effect of the change of ambient lighting depended on the ambient lighting conditions used for the calibration to the GSDF. The darker the ambient lighting condition for calibration was, the greater the variation in the contrast response was. If 50 lx and 100 lx were added to typical diagnostic reading stations (10 lx), the maximum deviations of the contrast response were −10.3% and −18.5%, respectively. Those maximum deviations of the contrast response were beyond an acceptable range (±10%) of AAPM TG18. Thus, the contrast in especially dark regions of medical images will be decreased. Conclusion: As the LCD monitor calibrated included typical diagnostic reading stations (10 lx), the need for recalibration to the GSDF with ambient lighting conditions increased over 50 lx to maintain imagecontrast.

The image quality of pseudophakic eyes with intraocular lenses in high myopia was studied by applying geometric and wave optics. Two types of intraocular lenses (IOL) were compared—one that was meniscus shaped and the other either planoconcave or planoconvex [bending factor (X)511]. A geometric study of image quality was used to analyze the transverse spherical aberration (TA) and the chromatic aberration (chromatic difference of the blur circles, CDBC). The loss of image quality and visual acuity increases as the TA and CDBC increase. The polychromatic modulation transfer function (MTF) was obtained using the point-spread function (PSF), taking into account spherical aberration and defocus coefficients. Finally, for chromatic and spherical aberrations and polychromatic MTF, the type of IOL that would best improve image quality for a given patient can be established.

A new synthetic evaluation method for the color display is studied. A testing system to measure the luminance, chromaticity, contrast ratio, uniformity, viewing angle as well as the PMTF (polychromatic modulation transfer function) is presented. The PMTF is calculated from the values of the monochromatic MTFs weighted by the CIE photopic luminous efficiency function of the human visual system. A high-precision XYZ translation stage to move the testing system and a two-axis goniometer to tip and turn the display under test to the desired viewing angle are used.

The cathode-ray tube (CRT) screen has recently been replaced by liquid crystal display (LCD) screens as visual stimulators for pattern-reversal visually evoked potentials (p-VEPs). The aim of the study was to evaluate the usefulness of LCD screen to elicit p-VEPs. The waveforms of the p-VEPs elicited by a LCD panel were compared with those elicited by a conventional CRT screen. The changes in the luminance of each screen were measured with a photodiode, and the mean luminance change was measured with a luminance meter. VEPs and electroretinograms (ERGs) were also recorded when the monitor was covered by a diffuser. The p-VEPs elicited by the LCD consisted of the N75 and P100 components of the conventional VEPs and had good reproducibility. The average latency of these components was significantly delayed by 9.8ms for N75 and 10.2ms for P100, and the N75-P100 amplitude was significantly larger than the conventional p-VEP elicited by the CRT screen. During the reversal phase, especially from black-to-white, the luminance of the LCD screen was transiently reduced, and it elicited a flash VEP and ERG. A reduction in the contrast of the checks minimized the transient change in the luminance, and the VEP waveform was more similar to that elicited by the CRT screen. The results suggest that when an LCD monitor is used as an alternative visual stimulator to elicit p-VEPs, the delay in the luminance change and the flash effect needs to be taken into account.

Evaluation of a new test pattern for daily quality assurance of medical display monitors

The color characteristics of medical liquid-crystal displays (LCDs) have become one of the main interests in quality assurance and quality control of medical display devices. It is necessary to evaluate variations of the color characteristics in medical LCDs in order to provide consistent color characteristics for image reading. In this study, we characterize the color characteristics in grayscale images displayed on medical LCDs. Eight medical color LCDs and eight medical monochrome LCDs were used in this study with operating times ranging from 800 to 25 000 h. Default settings of correlated color temperature (CCT) of white points for all color LCDs were set at 7500 K. We measured chromaticity in the Commission Internationale de l'Éclairage (CIE) u'v' color space and CCT of the white point at 18 luminance levels. A colorimeter and grayscale test patterns with various luminance levels were used for the measurements. First, we examined differences in chromaticity and CCT at 18 luminance levels for each LCD. Second, we compared chromaticities of the different LCDs. Then, chromaticity and CCT of LCDs were measured at different ambient light conditions (30 and 560 lux) and compared to those measured in a dark room. Finally, the relationship between operating times and CCT was evaluated. The chromaticities of monochrome LCDs changed toward the blue and CCT increased as luminance decreased. In color LCDs, the chromaticity and CCT of the white point except at the minimum luminance were nearly constant to those measured at the maximum luminance. We observed differences in chromaticity between color and monochrome LCDs because of the nonadjustable white point of monochrome LCDs. When the ambient light increased, chromaticity varied, and CCT decreased on every LCD. Ambient light had a much greater impact on chromaticity and CCT at lower luminance levels. The CCT of LCDs decreased in longer operating times. The grayscale of LCDs with longer operating times was measured to be more yellowish due to the degradation of cold cathode fluorescent lamps. Our results clearly indicate that the white point in grayscale images displayed on medical LCDs changes depending on luminance levels, color or monochrome LCDs, ambient light conditions, and operating times. These data provide useful information to understand color characteristics of LCD for image reading, especially for quality assurance and quality control of LCDs.

We report on the development of an automated visual inspection system for liquid crystal display (LCD) modules. The system comprises a highly graphical software program, a unique image processing algorithm, a PC interface card for driving different types of LCD modules, and a universal test jig for holding these modules. The system is able to detect faulty or malfunctioning LCD modules with minimum intervention from human operator; allows testing to be carried out for evaluating the display quality such as contrast ratio; is able to create new test databases for new LCD modules; allows permanent storage/backup of test databases for each individual LCD module; and provides a friendly user interface for ease of operation. In addition, the system has the following features: different access levels for different users; an editor for creating software drivers for driving different types of LCD modules; and a graphical help facility.

The aim of this study is to propose a method for the quantitative evaluation of image quality of both monochrome and color liquid-crystal displays (LCDs) using a commercially available color digital camera. The intensities of the unprocessed red (R), green (G), and blue (B) signals of a camera vary depending on the spectral sensitivity of the image sensor used in the camera. For consistent evaluation of image quality for both monochrome and color LCDs, the unprocessed RGB signals of the camera were converted into gray scale signals that corresponded to the luminance of the LCD. Gray scale signals for the monochrome LCD were evaluated by using only the green channel signals of the camera. For the color LCD, the RGB signals of the camera were converted into gray scale signals by employing weighting factors (WFs) for each RGB channel. A line image displayed on the color LCD was simulated on the monochrome LCD by using a software application for subpixel driving in order to verify the WF-based conversion method. Furthermore, the results obtained by different types of commercially available color cameras and a photometric camera were compared to examine the consistency of the authors' method. Finally, image quality for both the monochrome and color LCDs was assessed by measuring modulation transfer functions (MTFs) and Wiener spectra (WS). The authors' results demonstrated that the proposed method for calibrating the spectral sensitivity of the camera resulted in a consistent and reliable evaluation of the luminance of monochrome and color LCDs. The MTFs and WS showed different characteristics for the two LCD types owing to difference in the subpixel structure. The MTF in the vertical direction of the color LCD was superior to that of the monochrome LCD, although the WS in the vertical direction of the color LCD was inferior to that of the monochrome LCD as a result of luminance fluctuations in RGB subpixels. The authors' method based on the use of a commercially available color camera is useful to evaluate and understand the display performances of both monochrome and color LCDs in radiology departments.

ObjectiveTo compare observer performance using liquid-crystal display (LCD) and cathode-ray tube (CRT) monitors in the interpretation of soft-copy chest radiographs for the detection of small solitary pulmonary nodules.Materials and MethodsBy reviewing our Medical Center's radiologic information system, the eight radiologists participating in this study (three board-certified and five resident) retrospectively collected 40 chest radiographs showing a solitary noncalcified pulmonary nodule approximately 1 cm in diameter, and 40 normal chest radiographs. All were obtained using a storage-phosphor system, and CT scans of the same patients served as the gold standard for the presence of a pulmonary nodule. Digital images were displayed on both high-resolution LCD and CRT monitors. The readers were requested to rank each image using a five-point scale (1 = definitely negative, 3 = equivocal or indeterminate, 5 = definitely positive), and the data were interpreted using receiver operating characteristic (ROC) analysis.ResultsThe mean area under the ROC curve was 0.8901±0.0259 for the LCD session, and 0.8716±0.0266 for the CRT session (p > 0.05). The reading time for the LCD session was not significantly different from that for the CRT session (37.12 and 41.46 minutes, respectively; p = 0.889).ConclusionFor detecting small solitary pulmonary nodules, an LCD monitor and a CRT monitor are comparable.

Reviewed by: The TVs of Tomorrow: How RCA's Flat-screen Dreams Led to the First LCDs by Benjamin Gross Michael Aaron Dennis (bio) The TVs of Tomorrow: How RCA's Flat-screen Dreams Led to the First LCDs By Benjamin Gross. Chicago: University of Chicago Press, 2019. Pp. 288. We live surrounded by LCD (liquid crystal display) screens; Ben Gross's volume explains the origins of this technology at RCA and how the iconic American firm failed to deliver it to the world. This fascinating story of industrial research, corporate politics, and technological change blends science, technology, and business histories. Gross locates the emergence, efflorescence, and decline of LCD screens at the intersection of three distinct axes—the material logic of LCDs, that is their physical chemistry and often recalcitrant behavior plus the infrastructure for their creation and use; RCA's strategic goals as well as the Sarnoff Laboratory's role in fulfilling them; and the interactions among researchers, their managers, and other RCA divisions. One of the many interesting things readers learn is that the technology dominating our lives received so little support from RCA management. Indeed, they ultimately seemed to value LCD patents more than developing televisions based on this novel display technology. Noteworthy are Gross's discussions about the problem of finding the sources needed to write the history of late twentieth-century corporate R&D. RCA's quest for a follow-up to its color television came in 1951, with legendary founder David Sarnoff's challenge to develop a light amplifier. Efforts ensued to find alternatives to the standard display technology, the CRT (cathode ray tube). RCA pioneered the mass production of these glass bubbles, and it proved hard to break from this anchoring technology. Only after it became clear that CRTs could not be flattened in order to hang from walls and display a quality picture did researchers and management explore and develop alternatives. By 1964, the company's research included liquid crystals and their chemistry; however, as Gross points out, it was never really a large research group. Compared to the well-studied RCA video disc, called a "Manhattan Project," RCA's work on LCDs was a modest effort. Although [End Page 1240] public relations people hyped the research and its potential, this was never a corporate moon shot. Gross rightly highlights the problems in manufacturing the new technology once researchers overcame problems at the bench. Using laboratory notebooks, he delineates how researchers solved the issue of LCDs working at room temperature. Building bridges with RCA's manufacturing divisions became as vital as laboratory research to keep LCD work alive, while management paid more attention to a struggling computer effort and the firm's traditional color television business. Even once the multiple manufacturing problems were solved, the LCDs produced by RCA were for watch displays, not the wall-hanging televisions of the future. The initial secrecy surrounding LCD research demonstrated how highly it was valued, yet RCA soon viewed patents as the real source of value compared to physical products, given the costs and difficulties of profitably manufacturing LCDs in America. Gross's interviews and archival work display the full range of skills required to move lab products to the factory, including individuals with the requisite social skills to borrow resources from other groups. This social aspect of intra-laboratory relations is especially well portrayed. Gross plays with Clayton Christensen's ideas of disruptive innovation in explaining why RCA failed to capitalize on its role as a pioneer in LCD research. He follows LCD researchers at RCA to a new start-up, Optel that fails to take advantage of new LCD chemistry, instead sticking to RCA-based technologies. Small size did not prevent an aversion to change. In his final eloquent chapter, Gross explains that it was only once LCD technology had left RCA that it really grew and developed—as multiple firms, first on the West Coast and then in Japan, invested in significant R&D with specific products in mind. Seiko developed a watch-sized LCD television more advanced than Dick Tracy's, while Sharp demonstrated a fourteen-inch color display in 1988. Ironically, Sharp had approached RCA in 1970 about...

Aspheric Intraocular Lenses

To compare the observer performance 0f liquid crystal display (LCO) and cathode ray tube (CRT) monitors in detecting experimentally induced pulmonary edema in pigs by using soft-copy images of amorphous selenium-based flat-panel-detector radiography (OR) and storage phosphor computed radiography (CR). Oleic acid was injected intra-atrially into three pigs (weight, 20-25kg) at doses of 0.04, 0.05, and 0.06 ml/kg to induce pulmonary edema. Each set of CR, DR, and thin-section CT scans were obtained every 20-30 minutes from three pigs over 4-6hours. Thus, 37 sets (10 sets from pig-1, 11 sets from pig-2, and 16 sets from pig-3) of radiographs were obtained. Images were masked for identity. randomly sorted, and displayed on both live mega pixel (2048 x 2560 x 8 bits) LCD and CRT monitors. Eight radiologists rated each image for Ihe presence of ill-defined diffuse opacities and reticular-Iinear opacities in both lungs by using continuous rating scale of 0-100. A total of 4736 (37 sets 2 detector system 2 fields 2 lesion types 8 observers 2 monitor systems) observations were analyzed in terms of receiver operating characteristics. Average observer performance in detecting ill defined diffuse opacities, LCO and CRT monitors were not different significantly in both OR and CR images. Average performance in detecting reticular-linear opacities was significantly better with LCD than CRT. These differences were significant in evaluating DR images (AUC=.852±.038 on LCD; AUC=.785±.070 on CRT) but not significant in evaluating CR images (AUC=.795±.060 on LCD; AUC=.745±.070 on CRT) System on both LCO and CRT monitors (p=.042 on LCD; p=.044 on CRT). Moreover. with OR system. observer performance was better with LCD monitor than with CRT monitor (p=.013), whereas with CR system, observer performance was not different significantly on both monitors (p=.11 8). Overall the five-megapixel LCD monitor was equal or superior to CRT monitor of the same pixel size in detecting experimentally induced pulmonary edema. Moreover, the LCD monitor appears, to be more optimized for detecting pulmonary reticular-linear opacity, when interfaced with DR system rather than with CR system.

The Liquid Crystal Display (LCD) module in a high power TEA CO2 laser is easy to couple with electromagnetic interference, so as to affect the normal work of the laser. Therefore, this paper explores the prediction method of Electromagnetic Compatibility (EMC) for the LCD module under transient irradiation in an electromagnetic field. The coupling mechanism of electromagnetic interference received by the LCD module integrated in the laser system was analyzed. On the basis of the coupling of field and line, the field line electromagnetic interference of the LCD module was analyzed and calculated by using the BLT equation in the Taylor form, then, the prediction results were verified by several experimentally. The experimental results show that the interference voltage produced by connect cables coupled with electromagnetic fields on the data lines of LCD display module is 1 V, and exceeds the noise margin of the circuit. So the EMC control measures must be taken to ensure the performance of the LCD module. Moreover, the verification experiments indicate that prediction results for the EMC has correctly reflected the actual EMC performance of LCD module. The method has a guiding significance for prediction and design of EMC of electrical equipment in high-power TEA CO2 lasers.