Measuring arrangement for the clear scanning of at least one reference mark allocated to a graduation
First Claim
1. In a measuring system for measuring the relative position of two objects, of the type comprising:
- a scale which defines a graduation and at least one reference mark absolutely positioned with respect to the graduation;
a scanning unit which includes at least one scanning plate for scanning the graduation and the reference mark along respective optical paths and for generating reference pulses in response to the reference marks; and
means for utilizing the reference pulses as an indication of absolute position;
wherein the scale and the scanning plate are shiftable with respect to one another at a predetermined spacing therebetween;
the improvement comprising;
at least one graduation scanning field defined by the at least one scanning plate;
at least one reference mark scanning field defined by the at least one scanning plate; and
means for providing a phase difference between (1) the optical path length between the graduation and the graduation scanning field and (2) the optical path length between the reference mark and the reference mark scanning field.
1 Assignment
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Accused Products
Abstract
A measuring system for measuring the relative position of two objects is provided with a scale which defines reference marks absolutely allocated to a graduation. The graduation and the reference marks are scanned in a scanning unit by associated scanning fields of a scanning plate. For the clear and unambiguous scanning of the reference marks, and for the optimal scanning of the graduation, (1) the optical path length of the light rays between the graduation and the associated scanning fields and (2) the optical path length of the light rays between the reference marks and the associated scanning fields are provided with a phase difference. In this way, the optical path length for multiple scanning paths can be individually optimized.
16 Citations
11 Claims
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1. In a measuring system for measuring the relative position of two objects, of the type comprising:
- a scale which defines a graduation and at least one reference mark absolutely positioned with respect to the graduation;
a scanning unit which includes at least one scanning plate for scanning the graduation and the reference mark along respective optical paths and for generating reference pulses in response to the reference marks; and
means for utilizing the reference pulses as an indication of absolute position;
wherein the scale and the scanning plate are shiftable with respect to one another at a predetermined spacing therebetween;
the improvement comprising;at least one graduation scanning field defined by the at least one scanning plate; at least one reference mark scanning field defined by the at least one scanning plate; and means for providing a phase difference between (1) the optical path length between the graduation and the graduation scanning field and (2) the optical path length between the reference mark and the reference mark scanning field. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
- a scale which defines a graduation and at least one reference mark absolutely positioned with respect to the graduation;
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10. In a measuring system for measuring the relative position of two objects, of the type comprising:
- a scale which defines a graduation and at least one reference mark absolutely positioned with respect to the graduation, the at least one reference mark defining a reference mark field;
a scanning unit which includes at least one scanning plate for scanning the graduation and the reference mark along respective optical paths and for generating reference pulses in response to the reference marks; and
means for utilizing the reference pulses as an indication of absolute position;
wherein the scale and scanning plate are shiftable with respect to one another at a predetermined spacing therebetween;
the improvement comprising;at least one graduation scanning field defined by the at least one scanning plate; at least one reference mark scanning field defined by the at least one scanning plate such that the separation between the graduation and the graduation scanning field is equal to the separation between the reference mark and the reference mark scanning field; and an imaging optic positioned between the scanning plate and the scale and aligned with the reference mark scanning field, said optic comprising an imaging acceptance region, said optic operative to image the portion of the reference mark field within the imaging acceptance region onto the reference mark scanning field, said optic configured to provide reliable scanning of the reference mark at the separation between the reference mark and the reference mark scanning field.
- a scale which defines a graduation and at least one reference mark absolutely positioned with respect to the graduation, the at least one reference mark defining a reference mark field;
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11. In a measuring system for measuring the relative position of two objects, of the type comprising:
- a scale which defines a graduation of grid constant PM and at least one reference mark comprising at least one line graduation, the narrowest line graduation of width d, the at least one reference mark absolutely positioned with respect to the graduation;
a scanning unit which includes at least one scanning plate for scanning the graduation along a first optical path and for scanning the at least one reference mark along a second optical path wherein the light traversing the optical paths comprises a center of gravity wavelength λ
, the scanning unit generating reference pulses in response to the reference marks; and
means for utilizing the reference pulses as an indication of absolute position;
wherein the scale and the scanning plate are shiftable with respect to one another at a predetermined spacing therebetween;
the improvement comprising;at least one graduation scanning field defined by the at least one scanning plate; at least one reference mark scanning field defined by the at least one scanning plate; and means for providing a phase difference h between the first and second optical paths to provide for substantially optimal scanning of the graduation and reference marks by adjusting at least one of the grid constant PM, the line width d and the center of gravity wavelength λ
according to the relation h=n·
PM2 /λ
-4d2 /λ
(n=1, 2, 3 . . .).
- a scale which defines a graduation of grid constant PM and at least one reference mark comprising at least one line graduation, the narrowest line graduation of width d, the at least one reference mark absolutely positioned with respect to the graduation;
Specification