Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Patent
1996-02-16
1998-09-22
Dang, Hung X.
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
351216, 351235, A61B 3100
Patent
active
058122419
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a phoropter according to the kind of art as disclosed in the claims for testing the human eye for determining vision aids.
Various modifications of phoropters are conventionally employed for subjectively determining the refraction of the human eye. Typically, they consist of a number of disks for supporting optical elements which permit various combinations of elements for determining the deficiency of sight of the human eye. A known phoropter is constituted of two lens supporting disks which are arranged for rotation about at least one axis (common axis) in a housing (refer to DE 3524498 A1), one disk being provided with a large number of lenses and the other disk with a low number of lenses, located at definite sites of elements. Since the disk comprising the large number of lenses has to be of large diameter, due to the geometrical and optical conditions, and since the lenses of both disks have to cooperate in the common observation path the diameter of the disk supporting the lower number of elements is determined accordingly. Hence, a phoropter of considerable dimensions and expenditures for material results.
This proves to be a considerable disadvantage when such a phoropter has to be mechanized or automated since the drive and scanning means require additional space in the vicinity of the disks (refer to EP 0 070 333 A2 and DE 30 37 466 A1).
To avoid that the patient is subject to disturbances the phoropters are generally required to have a housing width at the dioptric passage, i.e. the length of the observation channels, as short as possible. For example, with a leading phoropter producer this length is 27 mm, otherwise the housing width is 100 mm. On the one hand, this condition requires a considerable low number of lens and prism disks and an increase of their diameters. On the other hand, a considerably large part of the face of the patient should be visible to involve the patient's features in the course of an examination. Furthermore, mechanized and automated phoropters are generally required to be of compact construction at low expenditures for material. An optical instrument for manual determination of a patient's deficiencies of sight as disclosed in the U.S. Pat. No. 1,666,406 is an approach to these requirements in which three lens mounting disks are provided with six element sites each. By means of an adding drive the disks are displaced mutually in such a manner that a patient's deficiency of sight can be determined over a wide range in 0.25 dioptre steps. It is, however, not feasible to operate said instrument automatically and, owing to the restricted number of element sites, it is not very versatile.
SUMMARY OF THE INVENTION
It is an object of the present invention to achieve compatibility of partially contradictory requirements such as compactness, scope of application, housing width at the dioptric passage, efficiency and precision of a phoropter in addition to satisfying the kinematic requirements when rotating the lens and prism disks as well as other disks.
BRIEF DESCRIPTIONS OF THE INVENTION
According to the invention this is realized by the features of the first claim. The diameter of the disks supporting spherical and cylindrical lenses, cylinders and optical accessories is substantially the sum of the diameter of the second drive wheel and of twice the diameter of the first drive wheels. When the diameters of the first and the second drive wheels are equal the disk diameters are equal to three-fold the diameter of the drive wheels. Said diameter, in turn, is determined by the free passage of vision and the latter by the eyes under examination. Thus it is feasible to reduce the lens disk diameters by a half without reducing the phoropter efficiency which, on the one hand, involves a lower covering of a patient's face and, on the other hand, favorable kinematic conditions when pivoting the lens and the prism disks. The moment of rotation and the affects of impact and tumbling errors as well as of surface roughnesses
REFERENCES:
patent: 1666406 (1928-04-01), Clement et al.
patent: 2968213 (1961-01-01), Wright et al.
patent: 3498699 (1970-03-01), Wilkinson
patent: 4606624 (1986-08-01), Wood
Doms Manfred
Fischer Ulrich
Block Medizintechnik GmbH
Dang Hung X.
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