Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1999-12-22
2000-09-19
Font, Frank G.
Optics: measuring and testing
By polarized light examination
With light attenuation
356378, 356372, 356379, G01B 1124
Patent
active
061220639
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a measuring system for the non-contacting detection of the three-dimensional shape of a groove peripherally extending in a spectacle frame, comprising a light whose directing its light beam onto the groove, an optical imaging system which projects the light reflected at the groove onto an optical detector unit and which is disposed in a largely centred position relative to the groove to be measured on the spectacle frame, a holding means supporting the spectacle frame, which is supported for rotation relative to the light source, the detector system and the optical imaging system about a centring axis of a surface inscribed by the peripheral groove of the spectacle frame, as well as an evaluation unit for determining the three-dimensional shape of the groove.
PRIOR ART
In ophthalmic optics measuring devices with tactile measuring sensors are used in the majority of cases for measuring the three-dimensional course of the groove in the frame. For instance a testing device is known from the German Patent DE 41 31 331 for sensing the contour of the openings in spectacle frames or of templates for grinding the periphery of spectacle lenses. The testing device according to the German Patent 41 31 331 consists of a holder for the spectacle frame or the template, a sensing pin which engages into the groove of the opening of the spectacle frame by a sensor head and which can be brought to bear against the periphery of the template, moreover of a straight guide for the sensing pin which is mobile only in the x- and y-directions in parallel with the plane of the opening of the spectacle frame or the temple and which prevents a rotational movement, and finally of a path transducer for the x-direction and a path transducer for the y-direction.
The system described in the German Patent 41 31 331 furnishes, however, only an approximate three-dimensional curve of the frame groove because the detection is performed by physical contact with the rigid sensing body, which may be designed, for instance, as pin or ball, along the frame groove. The three-dimensional curve of the course of the frame groove, which is recorded in this manner, is determined, for example, through the course of a defined point on the testing body. The correct image of all the fine details of the curve proper cannot be detected, and hence the complementary glass facet associated with the groove can be correctly ground or produced only in approximation. Variations in shape between the precise course of the frame groove and the glass facet of the spectacle lens provoke, however, strain in the spectacle lens, which may easily result in a crack or break of the glass. The subject matter of the German Patent 41 31 331 moreover entails the disadvantage that the sensing device for sensing the contour by direct mechanical contact requires a holder for the spectacle frame, which clamps the frame in opposition to the force produced thereon by the sensing device. As a result, the clamping device as such as well as the sensing pin may deform the spectacle frame component, which results in a further inaccuracy in measurement. Furthermore, the tactile measuring devices present the disadvantage that they have been designed only for the detection of the rough course of the frame groove and that they are not suitable to furnish data on the entire three-dimensional geometry of both the frame component as such and the other components of the spectacle frame.
Moreover, sensing devices of the aforedescribed general type are also referred to as tracers involving measuring periods for the detection of the course of the groove in a spectacle frame which range at roughly 12 seconds. During this period 512 shape data is detected and stored for further processing, as a rule. The measuring accuracy amounts to approximately 0.01 mm. What is problematic is the correct recording of the spectacle shape. The devices so far developed are not suitable and in a position to detect the entire spectrum of spectacle shapes. "Extreme" radii o
REFERENCES:
patent: 5760889 (1998-06-01), Manning
patent: 5870191 (1999-02-01), Shirley et al.
patent: 6043891 (2000-03-01), Hartrumpf et al.
Berndt Dirk
Steinmann Christian
Font Frank G.
Fraunhofer-Gesellschaft zur Forderung der ange-wandten Forschung
Ratliff Reginald A.
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