Television – Video display – Cathode-ray tube
Reexamination Certificate
1998-04-21
2002-07-09
Diep, Nhon (Department: 2613)
Television
Video display
Cathode-ray tube
C359S819000
Reexamination Certificate
active
06417894
ABSTRACT:
FIELD OF THE INVENTION
An optical device for use at a computer work station enables a worker to magnify visual displays on a computer screen. The optical device helps workers to view a screen more easily, in greater detail, or from a more distant location, thereby preventing or reducing eyestrain, back pain, and other problems caused by extensive use of computer screens. The optical device is especially useful for helping workers with presbyopic eyesight to see computer screens.
BACKGROUND OF THE INVENTION
It is well known that the operation of computer monitors, video terminals, and the like in which the operator is required to view a screen for extended periods of time may cause operator eyestrain. The operation of computers has often been the source of back problems, headaches, and other ailments. This is especially true for computer operators, including word processors, secretaries, data processors, designers, financial professionals, or others who spend a considerable amount of time working at computer screens.
Maintaining an ergonomically correct posture may help avoid physical ailments associated with the use of computer screens. An ergonomically correct position, however, may be difficult to maintain under typical circumstances. For example, computer operators must simultaneously view a monitor screen, operate a computer key board and periodically view or write on various documents or files. Computer operators may need to move about and chance work positions or engage in diverse tasks, such as working at an adjacent desk or answering a phone. Such movement may require increased separation from the computer screen and/or a change in the viewing angle. These circumstances can be challenging in terms of maintaining an ergonomically correct position.
Even when maintaining an ergonomically correct position, any difficulty or deficiency in seeing the screen can lead to ailments such as eyestrain or headaches. Yet any visual problems in seeing the screen is likely to make it more difficulty to maintain an ergonomically correct position which will worsen such ailments or potentially lead to additional ailments such as backache or other musculoskeletal disorders or conditions. Moreover, it is not uncommon for such a disorder to insidiously develop over time, even over a period of years, becoming apparent only after the disorder has progressed to a point where it has become serious in nature and/or is difficult to reverse.
Persons who are presbyopic (“presbyopes”) have special problems in seeing computer screens. Everyone becomes presbyopic with after, usually beginning after a person reaches the mid forties. Presbyopia is when a person's eyes lose their natural flexibility for focusing on near objects, also referred to as a decline in accommodative ability. The range of accommodation is the distance (measured from the eye) to which an object can be carried toward the eye and kept in focus, and the power of accommodation is the dioptric equivalent of this distance, a standard unit of measurement in the ophthalmic field.
This loss of accommodation is believed due, at least partly, to a hardening of the lens of the eye with age. Normal eyesight can deteriorate to the point where at age 55, sharply focusing on anything within three feet is not possible without aid. As a consequence, most older people eventually require spectacles to assist them in short-distance vision, in order to see clearly when reading or doing close work. Several products are available for this purpose, including reading spectacles, bi-focals, and multi-focal or progressively graded spectacles. Each of these approaches has its own drawbacks or limitations while working with computers.
The nature of a computer work station is such that the computer monitor screen is usually located within the area a person with presbyopia would need bifocals, but is higher in the viewing plane than is corrected by such lenses. This leads to repeated head bobbing, as well as leaning forwards or backwards, in order to focus on the monitor, the key board, and possibly even a copy stand or document holder. Moreover, reading spectacles or bi-focals are limited to a single diopter power optimally designed for reading at a single predetermined distance. Computer screens may be positioned at a different distance (often a greater distance) from the eye than the distance a book is typically placed, particularly at certain moments when the computer operator increases his or her distance from the computer in order to view another object, such as a document or file on an adjacent desk. Moreover, the stronger the lens in bifocals or reading spectacles, the shorter will be the patient's range of focus. The loss of range can present difficulties to the computer operator who must see the computer screen, the keyboard and a documents at various distances.
Progressively graded spectacles allow correction for a continuum of distances, and have the advantage of permitting the user to instantaneously change focus in accordance with a change in viewing angle. With progressively graded lenses, however, focal distance strictly depends on the direction of viewing which is not necessarily commensurate with environmental requirements. The largest power grading typically starts at low angles for reading, and becomes gradually lower for higher angles and thus longer distances. In general, the extent of such a power variation is about 2.5-3 diopters from the lowest to the highest viewing angle. This variation of power as a function of viewing angle, as dictated by any progressive grading technique, is restrictive because the objects in an environment viewed by an observer rarely exhibit a spatial positioning that is exactly complementary to the grading. In most scenarios, the line of sight of a near object is lower than that of more distant objects, but this is not always the case. Consequently, viewing a computer screen at the same time as a document at a lower position may not be possible without an unnatural or inconvenient tilting of the head of the wearer, and this may increase the chances of an ergonomically poor posture or movement.
Various types of optical apparatus have been proposed to alleviate or reduce the eyesight difficulties of presbyopic and non-presbyopic individuals involved in working with computer screens. Such optical apparatus are commonly placed between the operator and the computer screen in order to magnify the screen. For example, U.S. Pat. No. 4,712,870 to Robinson and U.S. Pat. No. 4,577,928 to Brown disclose the use of Fresnel lenses that are interposed between the monitor and the operator to magnify the monitor screen image. An adjustable lens holder for a magnifying lens in the context of a computer screen is also disclosed in U.S. Pat. No. 4,529,268 to Brown, and U.S. Pat. No. 4,958,907 to Davis.
Although such prior-art image magnification devices may provide certain benefits, they suffer from serious deficiencies and limitations which have certainly limited their popularity. One problem with such prior-art magnifiers is that they employ Fresnel lenses. While having the advantage of being lightweight and inexpensive, Fresnel lenses have the disadvantage of exhibiting a pattern of fine concentric circles or the like that is cut into the surface of the lens in order to flatten the lens shape, which pattern is unattractive and detracts from the clarity of detail seen through the lens. Furthermore, a Fresnel lens placed relatively close to a computer screen does not adequately help presbyopes, because although the lens enlarges the lettering, the lettering remains fuzzy and cannot be brought into sharp focus. While a Fresnel lens with a larger focal distance may be placed a greater distance from the computer screen, the clarity of a Fresnel lens tends to decrease with increasing distance from the screen or object being magnified.
Another problem with prior-art computer magnifiers has been that they do not adjust very well to the changing positions of a computer operator and/or to the changing visual needs of the operat
Carlson Paul Eric
Fisherman Carl
Goff James A.
Ryan Howard Scott
Bausch & Lomb Incorporated
Diep Nhon
McGuire Katherine
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