Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1995-09-14
1997-07-15
Font, Frank G.
Optics: measuring and testing
By polarized light examination
With light attenuation
250237R, G01B 1114
Patent
active
056488513
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1) Field of the Invention
The invention relates to a device for determining the position of a body to be positioned relative to a reference point.
2) Description of Related Art
Position determining devices serve, for example, for controlling measurement and production machinery, and for determining paths between longitudinally shiftable objects such as measurement heads, handles or mounting arms. For these applications the precision with which these paths can be determined is of prime importance for the manufacturing precision of the automatic machinery.
A method and a device which makes a high degree of measurement precision possible independently from an exact conduction of a sampler are already known from DE-OS 39 09 856. For this, three marks of a graduated scale are evaluated by a sampler. For two marks, the projection angle formed between a projection center and these marks is independent from the distance the projection center is located above the marks and how far the projection center is laterally displaced. For three marks, the projection center is exactly determined via the additional projection angle between the projection center, this additional mark and one of the other marks. For a combination of two combination angles, there exists only one location at which the projection center can be situated.
So that the marks on this graduated scale can be reproduced on a projection surface of the sampler, the graduated scale must be evenly lit. This could occur through vertical illumination or back lighting. However, a lighting device requires additional space which stands in opposition to aspirations of miniaturization.
SUMMARY OF THE INVENTION
The invention has the present task of improving a position determining device such that the space requirement of the graduated scale can be reduced without loss of measurement precision.
This problem is solved with the device described in the overall concept of a device for determining the position of a body to be positioned relative to a reference body, the device comprising a body bearing a graduated scale including optical samplers, a reference body including at least three projectors which form projection angles to one another and the optical axes of which form at least one projection center, the three projectors projecting at least tree projected light marks on the graduated scale of the body, and means for trigonometrically calculating the coordinates of the at least one projection center from the projection angles between the projection center and at least three projected light marks as well as from a spacing distance between said at least three projected light marks as acquired by said optical samplers.
In the present invention, light marks are projected onto the graduated scale by means of projectors from which the position coordinates of the projection center are determined. More marks of a graduated scale are not reproduced on the projection surface of a separate sampler, but rather the graduated scale is itself a projection surface and includes an optical sampler for acquiring the imaged light marks. In this way, a separate lighting device as was required for lighting the marks of the graduated scale until now is done away with. The space requirement is thus significantly reduced.
Another advantage of the device in the invention is that, due to light beams or planes transmitted by the projectors, a distance-independent imaging clarity of the light beams or light planes on the optical samplers is achieved, through which a larger distance measurement range in the direction of the Z axis is achieved than with a fixed imaging lens system.
The projectors can be diverging, converging or diverging and converging.
For a combined diverging and converging arrangement, the coordinates of two spatially separated projection centers are determined which have, however, a set spatial relationship to one another. The concurrent determination of the coordinates of both projection centers makes it possible to compensate for measurement
REFERENCES:
patent: 5017013 (1991-05-01), Kellner
patent: 5181079 (1993-01-01), Klinger
patent: 5196900 (1993-03-01), Pettersen
patent: 5404226 (1995-04-01), Kellner
E.M.S. Technik GmbH
Font Frank G.
Stafira Michael P.
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