US 4,792,678 A · Photoelectric angle measuring device

Abstract

In a photoelectric measuring device for measuring the position of two objects which can be rotated relative to each other, a grid located on a graduation support, which is connected with one of the objects, is scanned by a scanning device connected with the other object. To eliminate the eccentricity between the grid and the rotational axis of the graduation support, the light beam emitted by a light source is split in a first graduation area of the grid into two first order diffraction beams, at two diffraction angles. After two-fold deviation by two parallel mirrors, the first order diffraction beams are again joined, in a second graduation area of the grid that lies diametrically opposite the first graduation area. The first order diffraction beams join at the same diffraction angles at which they were emitted from the first graduation area of the grid. Consequently, the beams at the second graduation area are parallel to themselves as they were emitted at the first graduation area.

Claims15

Dependent claims

A photoelectric measuring device for measuring the position of a first object rotatably movable with respect to a second object comprising:

a graduation support connected to said first object;
a grid located on said graduation support;
a scanning unit connected to said second object and positioned to scan said grid by means of light diffraction;
a first graduation area of said grid, adapted to emit, when scanned by said scanning unit, first and second light beams of a selected diffraction order at first and second angles, respectively, to a normal axis which is defined perpendicular to said first graduation area;
and
a second graduation area of said grid, diametrically opposite said first graduation area, adapted to interact with said first and second light beams such that said first and second light beams strike said second graduation area at the same said first and second angles, respectively, to a normal axis which is defined perpendicular to said second graduation area, such that said light beams are parallel to said light beams as they were emitted at said first graduation area.

3 more elements

Dependencies are inferred from the claim text.

Photoelectric angle measuring device

Life of this patent

Photoelectric angle measuring device

Life of this patent

Abstract

Claims15