Liquid crystal cells – elements and systems – Particular structure – Interconnection of plural cells in series
Patent
1996-05-24
1998-08-04
Sikes, William L.
Liquid crystal cells, elements and systems
Particular structure
Interconnection of plural cells in series
40361, 40362, G02F 11347, G02B 2702
Patent
active
057902160
DESCRIPTION:
BRIEF SUMMARY
RELATED APPLICATION
This application is the U.S. National filing of PCT/EP94/03968, which was filed on Nov. 28, 1994.
FIELD OF THE INVENTION
The present invention relates to viewing apparatus in general and, more particularly, to medical viewing and display apparatus including a light-modulated viewing device for X-ray film.
BACKGROUND OF THE INVENTION
Transparencies such as medical X-ray transparencies are usually examined by placing them over the viewing surface of a device commonly known as an illuminator. Conventional illuminators normally comprise a box-like structure enclosing fluorescent lighting tubes behind a light-diffusing plate which defines the viewing area. Commonly, transparencies are attached to the viewing surface by pushing the upper edge of the transparencies under spring-loaded film-holder clips located along the top edge of the viewing surface.
Standard size illuminators have a viewing surface seventeen inches high and fourteen inches or multiples of fourteen inches (i.e., 28 or 56 inches) wide. Usually, each fourteen inch width of viewing surface has its own fluorescent tubes and control switch. Such a viewing surface enables the viewing of standard size X-ray films which measure up to seventeen inches by fourteen inches.
It is well known that, when the viewed transparencies do not completely cover the viewing surface, undesired glare is generated from areas of the viewing surface not covered by the transparencies. This commonly occurs when transparencies smaller than fourteen inches by seventeen inches are to be examined while being typically retained on the display area in the same manner as full size transparencies as described above. Furthermore, even if the viewing area is fully covered with transparencies, slight dislocation of the transparencies on the viewing surface usually results in glaring light streaks at the edges of the transparencies. In practice, annoying glare is almost constantly generated from the viewing surface since viewing surfaces are typically quite large (thus, they are seldom completely covered) and since viewing surfaces (typically illuminated by slow-starting fluorescent light) are normally continuously lit while transparencies are changed.
Often, transparencies contain very transparent regions and very dense regions, which may be adjacent to each other and, frequently, the transparencies examined by radiologists are overexposed or underexposed or both. In these cases, considerable glare (and therefore deviation in adaptation levels) emanates through areas of the transparencies themselves.
The glare from uncovered areas detracts from the visual perception of the person "reading" the transparencies and assess the information contained thereon. Specifically, the ability of the eye to discern between close gray levels is reduced when the light adaption level based on the surroundings is different from the light level of the detail. This phenomenon was noted by E. W. Weber who found that "the minimum perceptible difference in illumination stimulus is proportional to the level of the light stimulus". This can be stated in terms of vision by: .delta.L/L=K (K is a constant designated the Weber constant); wherein L is the adaptation level luminance and .delta.L is the minimum detectable difference in luminance. See, for example, "Elemente der Psychophysic", G. T. Fechner, Leipzig, 1860, and "Visual Psychophysics", D. Jameson and L. M. Hurvich (ed.), Berlin, 1972.
Attempts have been made in the past to provide viewing devices for X-ray transparencies which shield the eyes of the observer from light emanating from light sources other than the light passing through the transparencies, in order to obscure light in parts of the transparencies and to reduce the contrast in transparencies when so required.
Flat panel spatial light modulators such as liquid crystal devices (LCD) are well known. Such devices are used extensively for visual display in applications such as car dashboards, instrumentation panels, household devices, sign posts, etc. Liquid crystal arra
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Inbar Dan
Wolf Hanan
Sikes William L.
SmartLight Ltd.
Ton Toan
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