Microe, Inc.

Gsi Group Corporation

Microe Systems Corporation

Donald K Mitchell

William G Thorburn

Andrew M Goldman

Donald L Grimes

Keith M Hinrichs

Joel Mikael Petersen

Bruce A Horwitz

Christopher Chapman Rich

Stuart Eric Schechter

Stuart A Dodson, Ii

A flexible optical marker is applied to an optical scale substrate to make an optical scale assembly for an optical position encoder. The marker may be a limit marker, index marker, or other type of marker. The marker substrate may be a plastic film such as polyester, singulated from a 'recombine' roll created by a web process. The marker has a microstructured pattern on one surface that is covered with a reflective metal coating. The marker also has an adhesive layer and is affixed to the optical scale substrate by a process of aligning the marker to an edge of the scale and then applying pressure to the upper surface of the marker. The marker may be applied with a handle portion that is separated from the marker after the marker is affixed. The marker may be especially useful with a flexible scale substrate such as a metal tape substrate. By affixing the marker to the scale substrate as a separate step of making an encoder scale, various benefits such as reduced inventory, cost, and lead time may be achieved.

Scale assembly for optical encoder having affixed optical reference markers

An optical encoder includes a source of a light beam, an optical grating that generates a spatial pattern of interference fringes, and an optical detector which includes generally elongated detector elements that sample the interference fringe pattern at spatially separated locations along the direction of motion of the grating. Each detector element has one or more segments slanted along the direction of motion of the grating by an integer multiple of the period of an undesirable harmonic component of the fringe pattern, thereby spatially integrating the harmonic component and suppressing its contribution to an output of the detector. One specific detector type includes parallel elongated rectangular elements in a rectangular array that is rotated slightly about a Z axis; another type includes detector elements arranged to form a non-rectangular parallelogram. Another type of detector includes detector elements that each have multiple elongated rectangular segments which may be arranged into two non-parallel sets. The two sets can be further arranged in an alternating fashion so as to impart a zig-zag or chevron shape to each detector element.

Optical encoder having slanted optical detector elements for harmonic suppression

An optical encoder includes a sensor head, an encoder scale, and an optical wavefront dividing element. The sensor head includes a substrate, a light source, a first optical detector, and a second optical detector. The light source, the first optical detector, and the second optical detector are disposed on the substrate. The scale includes a first track and a second track. The optical wavefront dividing element is disposed between the sensor head and the scale. A light beam emitted by the light source is divided into a first beam and a second beam by the wavefront dividing element. The first beam is incident on the first track and the second beam is incident on the second track. Light from the first beam diffracted by the first track is incident on the first optical detector. Light from the second beam diffracted by the second track is incident on the second optical detector.

Multi-track optical encoder employing beam divider

An optical encoder includes an optical source, a scale, an optical detector and signal processing circuitry. The scale is operative with a light beam from the source to generate an optical pattern such as a line pattern extending in an X direction of relative movement between the scale and the source. The detector generates analog detector output signals indicative of the location of the optical pattern on the detector in an alignment direction orthogonal to the X direction. The detector may include two bi-cell elements spaced apart in the X direction, each element including two cells of complementary shape, such as a sharks-tooth. The signal processing circuitry operates in response to the detector output signals to generate an alignment value indicating a polarity and a magnitude of misalignment between the detector and the scale in the alignment direction. A method of providing information to a user regarding alignment of a detector and an encoder scale employs a graphical alignment indicator displayed on a computer display. The graphical alignment indicator has a bipolar indicator scale and a marker whose location on the scale is based on the alignment values such that the magnitude and polarity of misalignment is indicated.

Optical position encoder having alignment indicators providing quantitative alignment indications

There is provided a measurement system in which the calibration data is easily incorporated into or obtained by the position sensing and/or displacement sensing system's processing unit. A scale-based encoder has a signal processor that corrects for scale inaccuracy based on a limited set of correction coefficients. The correction coefficients are the slopes and offsets that define a piecewise linear correction curve corresponding to the errors inherent in the scale. Several ways for communicating the coefficients to the processor are envisioned. Correction is applicable to linear or rotary encoders.

Position encoder with scale calibration

Position of a diffusely scattering surface is detected by interfering backscattered light from respective input beams which illuminate a common spot. Through polarization of the input beams and appropriate filtering, backscattered light is isolated from specularly reflected light and interfered to form a fringe pattern on a detector. The position sensor has particular applicability as a push pin sensor in a hard disk servo system.

Diffuse surface interference position sensor

A displacement measuring apparatus is disclosed, one embodiment of which employs two diffractive code disks, attached to a shaft, and a sensing head which need not contact the shaft. The head includes a light source with beam shaping optics, which creates two individual beamlets and pre-cranks the beamlets so that they reach the first grating at proscribed angles. Two diffracted orders from the first grating are allowed, preferably through free space propagation, to strike the second grating and to be rediffracted by the second grating. A phased-array detector, or equivalent array of detecting elements, are positioned beyond the second grating and in a region of natural interference between rediffracted orders of the incident diffracted orders, to detect the interference fringes which are generated there. The change in phase of the fringes is proportional to the relative displacement between the first and second gratings.

Non-contacting torque sensor and displacement measuring apparatus and

The apparatus disclosed herein employs a grating (13) which concentrates light at a preselected wavelength into the positive (33) and negative (35) first orders while minimizing the zeroth order (31). The grating (13) is illuminated with monochromatic light of the selected wavelength and a poly-phase periodic detector (25) has its sensing plane spaced from the grating a distance less than ##EQU1## where W is the width of the illuminated region of the grating. The period of the poly-phase detector is equal to P/2 so that each detector element (51) or phase responds principally to the natural interference between the positive and negative first orders without requiring magnification or redirection of the diffracted light. Preferably, the distance of the sensing plane from the grating (13) is greater than ##EQU2## so that the detector response does not include substantial components from diffraction orders higher than the first. Various embodiments of the invention are described including a wavefront compensation approach which greatly increases design freedom in the selection of grating and detector characteristics in implementing the present invention in practical and manufacturable devices.

Relative movement detecting apparatus using a detector positioned in a

The apparatus disclosed herein employs a grating or scale which concentrates light at a preselected wavelength into the positive and negative first orders while minimizing the zeroth order. The scale is illuminated with monochromatic light of the selected wavelength and a poly-phase periodic detector has its sensing plane spaced from the scale a distance less than ##EQU1## where W is the width of the illuminated region of the scale. The period of the poly-phase detector is equal to P/2 so that each detector element or phase responds principally to interference between the positive and negative first orders without requiring magnification or redirection of the diffracted light. Preferably, the distance of the sensing plane from the scale is greater than ##EQU2## so that the detector response does not include substantial components from diffraction orders higher than the first.

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Wayland, MA, United States of America

Donald K Mitchell