Incremental measuring system with selectively designated reference marks
AssigneeDr. Johannes Heidenhain GmbH
InventorWalter Schmitt
Life of this patent
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Abstract
An incremental measuring instrument having a series of fixed reference marks along one edge of the grid scale is disclosed in which a series of movable magnets or occluding screens are located along the opposite edge of the grid scale so that any subset of the total set of reference marks may be designated for control purposes. A scanning unit is provided to scan the scale, and this scanning unit includes a first photosensitive element responsive to the fixed reference marks, and a second photosensitive element mounted in anti-parallel with the first photosensitive element. This second photosensitve element is illuminated by light which varies in intensity according to whether or not the respective reference mark has a magnet or occluding screen associated therewith.
Claims10
In an incremental measuring system including a grid scale;
- an electronic counter;
- a plurality of fixed reference marks along the grid scale;
- a movable scanning unit;
- sensor means, included in the scanning unit, for generating an electrical impulse in conjunction with the reference marks for control of the electronic counter;
- at least one switching member mounted adjacent the scale for selectively designating a subset of the fixed reference marks needed for control purposes;
- and means, responsive to the at least one switching member, for selectively enabling the sensor means only for the designated subset of the reference marks, the improvement comprising:
- an impulse generating circuit, connected to the sensor means for generating the electrical impulse, said impulse generating circuit having two input terminals;
- a first photosensitive element included in the sensor means and connected across the two input terminals of the impulse generating circuit, said first photosensitive element positioned to scan the plurality of fixed reference marks;
- a second photosensitive element, included in the enabling means and connected in parallel with the first photosensitive element;
- and
- means for illuminating the second photosensitive element;
- said switching member operating selectively to alter illumination of the second photosensitive element by the illuminating means in order selectively to enable the sensor means only for the designated subset of the reference marks.
Dependencies are inferred from the claim text.