Optics: measuring and testing – Lens or reflective image former testing – For optical transfer function
Patent
1988-04-29
1991-04-16
Turner, Samuel
Optics: measuring and testing
Lens or reflective image former testing
For optical transfer function
G01M 1102
Patent
active
050077341
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an apparatus for measuring the refraction characteristics of ophthalmological lenses, in which a projection optic projects the light of a light source via a field aperture with a measuring figure and the ophthalmological lens, which is arranged on a lens support, onto a light reception device and the refraction characteristics are determined from the image site of the measuring figure in the lateral and/or longitudinal direction.
Such apparatuses are also called apex refracting power gauges and are known in various designs, by way of illustration as automatic apex refracting power gauges, with which a test object is imaged, as projection or telescope apex refracting power gauges, etc. A not-all-encompassing survey of the different possible designs is given by the article "Gerate zur Messung des Scheitel-brechwertes" in Augenoptik, 1984, pp 67-70 and the article "Aufbau und Funktion von Me.beta.geraten zur automatischen Messung des Scheitelbrechwerts" in Deutsche Ootiker-Zeitung 3/1980 pp. 9-21.
Prior art apex refracting power gauges usually operate with parallel beam paths and determine the so-called distance apex refracting power. A principle measurement error arises when measuring multi-focal lenses with apex refracting power gauges of this type. With regard to this, reference is made to Dr. W. Roos' articles, by way of illustration, in the Suddeutsche Optiker Zeitung, 1953, or his special print "Uber den Strahlengang im Nahteilvon Zweistarkenglasern". In order to eliminate this principle measurement error, an apex refracting power gauge has been suggested in which the lens can be rotated about an axial point located 25 mm behind the eye-facing surface. This apex refracting power gauge is briefly mentioned in the article "Brillenglaser mit gleitender optischer Wirkung" by Dr. Josef Reiner, in the Suudd Ootikerzeitung, 1961, pp 114 ff and, in particular, on p. 116. Such apex refracting power gauges with a rotatable lens arrangement have not made a significant impact in practice.
One reason for this is probably the complicated assembly plus the unaltered beam path, still yielding systematical measurement errors, which is intended for measuring the distance apex refracting power.
The object of the present invention is to provide an apparatus for measuring the refraction characteristics of ophthalmological lenses, which also permits determining the so-called near apex refracting power, to put it more precisely, the effective use-value.
A solution to this object, in accordance with the present invention, and further embodiments thereof is defined in the patent claims hereto.
An inventive element is that the beam path of the apparatus can be altered corresponding to the desired distanCe from the object. When the "distance from the object is infinite", the beam path in most apparatuses is, however, not necessarily a parallel beam path. For measuring the near apex refractive power or the effective use-value, the vergency of the beam path is altered for the infinite distance from the object in such a manner that it corresponds to the use position. By way of illustration, in the case of a specific optical build-up of the invented apparatus, the parallel beam path may be converted into a divergent beam path (near vergency) by moving the projection optic and/or adding supplementary lenses.
In order to hit the ophthalmological lens with this beam path, which corresponds to the use-position, the stationary lens support is designed in such a manner that the ophthalmological lens is positioned "diagonally to the beam path" in the beam path corresponding to the use-position.
The divergence resulting from positioning the ophthalmological lens "diagonally" in the beam path in near apex measurement is compensated for by dioptric and/or prism compensation, by way of illustration, a lens or a small additional prism.
By this means, without a rotation device, i.e. without moving parts, the effective use-value of ophthalmological lenses for near distances can be determined with an apparatus for m
REFERENCES:
patent: 1542112 (1925-06-01), Tillyer
patent: 1726820 (1929-09-01), Glancy
patent: 3019708 (1962-02-01), French et al.
patent: 3445169 (1969-05-01), Lueck
patent: 3519357 (1970-07-01), Davis
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