ISSN:1071-0922    

DOI:10.1889/1.1984946

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract—A methodology is demonstrated for evaluating dynamic visual performance by comparing a helmet‐mounted cathode‐ray‐tube (CRT) display with a liquid‐crystal display (LCD). The miniature CRT contained in the Integrated Helmet and Display Sighting System (IHADSS) used in the AH‐64 Apache helicopter was compared to a head‐mounted active‐matrix LCD (AMLCD) currently under development. Dynamic visual performance was assessed by measuring flicker detection, target recognition vs. duration, and target recognition vs. velocity in five subjects tested with each display (two‐way repeated measures design). At low‐to‐moderate rates of stimulus presentation, there was no significant difference in dynamic visual performance between displays. However, at higher rates of presentation (flicker frequency greater than 4 Hz, target velocity greater than 4 deg/s, target duration less than 250 ms), dynamic visual performance was significantly reduced when using an LCD compared to a CRT (p<0.01). These visual‐performance differences, which were not explicable by display differences in luminance, color, or spatial resolution, reflect differences in the capacity of each system to generate imagery of sufficient contrast at high rates of presentation. Implications for selection and development of visual displays for use in aviation and relate

ISSN:1071-0922    

DOI:10.1889/1.1984947

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract—A wide range of binocular disparity (0–140 arcmin) and depth‐of‐focus (DOF) conditions (resolution of non‐fixated motif, 1–23 cpd) were presented via stereoscopic slides to 12 non‐expert subjects. Viewing comfort was evaluated by a standardized assessment procedure (CCIR Recommendation 500). Results confirm the traditional threshold of 70 arcmin for disparities. Larger disparities lead to a marked drop in comfort ratings unless critical parts of the image are heavily blurred. In this case, even disparities of 140 arcmin are tolerated. Picture luminance (47 vs. 17 cd/m2) had no influence. The high consistency of the observed response patterns suggests a stable percept

ISSN:1071-0922    

DOI:10.1889/1.1984948

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract—Relationships between spot size, pixel spacing, and shadow‐mask pitch are presented that ensure suppression of aliasing artifacts in digitally addressed CRTs. The suppression is effective not only at low spatial frequencies (moiré), but at all spatial frequencies up to the useful limit of the display (the Nyquist freque

ISSN:1071-0922    

DOI:10.1889/1.1984949

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract—This paper presents an approach for the compression of mixed‐image data (images which include text) using a segmentation‐based image representation. The mixed image to be compressed is approximated as a set of uniform regions encoded as a set of region boundaries (contours) and descriptions of the region interiors. In order to improve the visual quality of textual portions in the image approximation, coarsely quantized approximation error (corresponding only to the textual portions) is also encoded. The segmentation method used to form this representation combines a Gaussian texture model and a Gibbs‐Markov contour model in order to find regions with boundaries which correspond closely to the objects in the image. A mixed image, in general, is difficult for conventional transform coding methods because these methods typically discard high‐frequency components or quantize them coarsely. Structures such as edges in the image, however, are dependent upon these high‐frequency components. Therefore, the visual quality of structures such as text (which consists mostly of high‐contrast edges) in the image is severely degraded by conventional transform coding methods. Due to its ability to capture the semantically important structure in the image, segmentation‐based coding is a promising approach for these images. The effectiveness of the proposed approach for the compression of mixed images is demonstrated through exper

ISSN:1071-0922    

DOI:10.1889/1.1984950

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract—A new, semi‐empirical model that describes TFTs in all operating regions with only one dynamic and five static parameters is proposed. This model can easily be implemented in most simulation programs and used to predict TFT circuit behavior. The five static parameters can automatically be extracted from current measurements and form a very compact yet adequate representation of the TFT characteristics. This proves especially useful when storing and statistically processing measurement results for a large number of devices, such as the pixel TFTs in an active mat

ISSN:1071-0922    

DOI:10.1889/1.1984951

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract—Using a simple scaling analysis, we predict the limitations of TFT‐LCDs. HDTVs with 40 in. diagonals and good aperture ratios should be possible, and even larger displays can be made if the aperture ratio is compromised. Although present trilayer a‐Si:H TFTs have problems with voltage errors due to the circuit capacitances, these can be reduced by advanced fabrication techniques, which will be used in future displays. Very large displays may have to use fabrication methods which will reduce the sensitivity to pinholes, but yields for 14–17‐in. workstation displays should be adequate. Displays with integrated drivers will see strong competition from displays with outboard silicon drivers as the cost of the latter comes down; displays with integrated TFT drivers will be confined to niche markets where their size and other advantages compensate for their hig

ISSN:1071-0922    

DOI:10.1889/1.1984952

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract—A wide‐viewing‐angle video display has been realized using a deformed‐helix ferroelectric liquid crystal (DHF‐LC) in combination with a diode active matrix. The DHF‐LC is operated in the symmetric mode (ac driving), preventing the occurrence of image sticking. The application of a reset pulse before the select pulse results in a much better step response of the display and in lower drive voltages. These effects have also been calculated by making use of the electronic equivalent circuit of DHF‐LC. The display has a contrast ratio of 25 and a transmission 55% that of a twisted

ISSN:1071-0922    

DOI:10.1889/1.1984953

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract—Novel UV‐curable liquid crystals showing nematic phases at room temperature have been developed. The liquid crystals can be utilized to create retardation films with high quality and good thermal stability. The properties of novel UV‐curable liquid crystals and the fabrication of various kinds of retardation films using them are disc

ISSN:1071-0922    

DOI:10.1889/1.1984954

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY