Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Patent
1999-11-16
2000-11-14
Manuel, George
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
A61B 310
Patent
active
061459895
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a lens meter capable of turning a lens to be tested, or a test lens, around a center of a turning movement corresponding to that of a turning movement of an eyeball in a spectacle lens-worn state.
BACKGROUND ART
Heretofore there has been known a lens meter provided with a projection light source for projecting a measuring beam onto a test lens and a light receiving element for receiving the measuring beam which has passed through the test lens, the lens meter measuring optical characteristics of the test lens on the basis of a position in which the light receiving element receives the measuring beam after passage through the test lens.
According to this conventional lens meter, with the test lens set in a lens receptacle, the measuring beam is projected onto the test lens and optical characteristics of the test lens such as spherical degree S, cylindrical degree C, axial angle A, and prism quantity Pr, at central and peripheral portions of the test lens are measured.
In this conventional lens meter, when optical characteristics are to be measured at the peripheral portion other than the central portion of the test lens, the test lens is moved while allowing the back of the lens to follow the lens receptacle .
In this connection, consideration will now be given about a spectacle lens-worn state. As shown in FIG. 1, when a person tries to see far, the man mainly uses a light ray P1 which passes through a central position of a spectacle lens 1, but for seeing near, the person uses a light ray P2 which passes through a peripheral position of the spectacle lens 1 and the light ray incident on the lens 1 is oblique to a back 1a of the spectacle lens 1. In FIG. 1 being referred to, the reference numeral 2 denotes an eyeball and the reference mark OL denotes a center of a turning movement of the eyeball 2.
In the conventional lens meter, as shown in FIG. 2, a test lens 3 is measured at a peripheral position thereof while allowing a back 3a of the lens to follow a lens receptacle 4. Thus, optical characteristics of the test lens 3 are measured at a peripheral position under the condition that a measuring beam P3 is incident perpendicularly to the back 3a of the lens 3. Therefore, the optical characteristics measured at a peripheral position of the test lens 3 by the conventional lens meter are not always considered to reflect an actual spectacle lens-worn state.
Particularly, today, with the advent of an aging society, the use of a progressive multi-focus lens is increasing, and in spectacle shops the opportunity of measuring optical characteristics of a progressive multi-focus lens is increasing. In the progressive multi-focus lens, the measurement is made for at least a far-sight portion and a near-sight portion and it is necessary that optical characteristics of the test lens 3 be measured at various positions. However, if the way of light ray passage in an actual spectacle lens-worn state and the way of light ray passage in the measurement using the conventional lens meter are different from each other, it is difficult to exactly evaluate optical characteristics of the progressive multi-focus lens.
There has been proposed a construction in which a turning bench adapted to turn around a center of a turning movement of an eyeball is attached to a lens meter different in measurement principle from the above lens meter.
FIG. 3 shows an example of an optical system in such a lens meter. In the same figure, the reference numeral 1A denotes an LED as a projection light source for the projection of a measuring light beam, 1B denotes a projection lens, 1C denotes a relay lens, 1D denotes a light receiving lens, and 1E a light receiving element, with a measurement target 1F being disposed between the projection lens 1B and the relay lens 1C. For example, four LEDs 1A are disposed around a measuring optical axis OA. A disposed plane 1G of the LED 1A and a disposed position 1H of the test lens are conjugate with respect to the projection lens 1B and the relay lens 1C. Th
REFERENCES:
patent: 4588270 (1986-05-01), Hiroshi
Ikezawa Yukio
Kato Takeyuki
Yanagi Eiichi
Kabushiki Kaisha TOPCOM
Manuel George
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