Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1993-11-14
1995-09-26
Pham, Hoa Q.
Optics: measuring and testing
By polarized light examination
With light attenuation
250237G, 33707, G01B 1114
Patent
active
054538394
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention pertains to a measuring instrument, and more particularly relates to an optoelectronic measuring scale which is constructed to determine and to indicate the exact position at which a beam of light emitted from a radiation source, for instance a laser projector, impinges thereon through a window or an opening.
BRIEF DESCRIPTION OF RELATED PRIOR ART
When detecting optical radiation, it is normal to use light detecting components generally in the form of semiconductors. Optoelectronic integrated circuits are used in the form of detector matrices equipped with so-called CCD-devices. Such devices (charge coupled devices) are normally very small (10-15.mu.m) and despite the fact that each separate matrix may include a large number of elements, about 2,000 elements, the total geometric extension of such a matrix is relatively short. Matrices which comprise charge coupled devices cannot therefore be used for measuring scales of relatively long lengths. This would require the matrices to be disposed in mutually sequential rows, but since the matrices are not equipped with CCD-devices right out to their extremities, the detection gaps between the matrices would reduce the detecting ability of such a linear measuring scale.
Neither is it possible to use matrices that are equipped with other forms of integrated circuits, since these would render the construction of remaining electronics in the measuring scale far too complicated for the intended purpose.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an optoelectronic measuring scale of relatively short extension, about 0.5 meters, and the invention is mainly characterized, to this end, in that the measuring scale includes a row of discrete photoelements firmly mounted on a circuit board or the like and connected conductively to a microprocessor attached to the circuit board; in that firmly mounted in the measuring-scale is a diffuser which functions to distribute radiation intensity of incident light in the measuring scale over a plurality of mutually adjacent photoelements; and in that the microprocessor functions to compare the intensity of the light emitted by respective photoelements and, subsequent to calculating the center-of-gravity of the broadened intensity curve, to produce signals which cause the exact position of the light beam on the measuring scale to be displayed on a display device connected to said scale.
The use of a diffusor in the beam path of the measuring scale is justified because the light beam emitted, for instance, by a laser projector has a small beam divergence and a small degree of intensity distribution. The pitch or spacing of the photoelements mounted on a circuit board in the measuring scale is greater than the intensity distribution of the light beam. With a diffusor placed in the beam path of the measuring scale, the radiation intensity of the light beam is distributed in a manner such that a plurality of mutually adjacent photoelements will be irradiated within the measuring scale and therewith deliver output currents that are proportional to the degree of illumination or irradiation.
DESCRIPTION OF THE DRAWING
Other characteristic features of the invention are evident from the following description and claims. The invention will now be described in more detail with reference to exemplifying embodiments thereof and also with reference to the accompanying drawings, in which
FIG. 1 is a schematic, longitudinal view of an inventive measuring scale including a row of photoelements and a microprocessor;
FIG. 2 is a cross-sectional view of the measuring scale shown in FIG. 1; and
FIGS. 3(a), 3(b), and 3(c) illustrates the detection principles of the measuring scale.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The inventive measuring scale has the form of an optoelectronic detector unit. It comprises an elongated profiled body 19 which is enclosed by walls 20, 21, 22 on three sides thereof. A fourth side, the upper si
REFERENCES:
patent: 3100846 (1963-08-01), Burkhardt
patent: 3369444 (1968-02-01), Patrignani
patent: 3865492 (1975-02-01), Butler
patent: 4135086 (1979-01-01), Baba
patent: 4490608 (1984-12-01), Yeadon et al.
patent: 4898464 (1990-02-01), Thorne et al.
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