US 5,808,730 AGranted

Fiber optic displacement sensor

AssigneeCeramOptec Industries, Inc.

InventorsGeorge Danielian, Alexej Avacian

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Abstract

A device is provided for measuring angular displacement and rotational movement of a shaft or linear displacement of an object comprising a light source, a Multichannel Fiber Optic Bundle, an optical code wheel or linear scale with optical tracks for light modulation, including typically a raster and a reference mark, a system of photodetectors, amplifiers, comparators of analog signals and a digital electronic block. The device forms a sequence of electric pulses whose number is proportional to displacement, a set of pulses indicating zero position of the disk, and also a logic signal indicating the direction of the displacement. A multichannel fiber optic bundle provides channels for the transmission and collection of light from the light source to the sensing site and back to the photodetectors and for light intensity monitoring of the source. Special randomization of the fibers at the sensing element end of the multichannel fiber optic bundle into two or more channels and modulating the collected light signals by a raster splits the collected light signal into at least two channels and introduces a phase difference of 90.degree. between the split channels. The electronic components of the device are connected with the sensing element with a multichannel fiber optic cable or the directly by the multichannel fiber optic bundle, which removes them from the often harsh environments surrounding the sensing element. This provides an important advantage for many practical applications over the prior art.

Claims9

Dependent claims

A fiber optic displacement sensor for indicating the angle displacement and the rotational movement of a shaft or linear displacement of an object, comprising:

a first multichannel fiber optic bundle (MFOB A) for light transmission, which is split at one end into at least two channels, with at least one Reference Fiber Optic Channel for monitoring light intensity level of a light source;
two optical tracks for light modulation, a first optical track having means for displacement modulation, and a second optical track having at least one section for detecting a reference position;
a second multichannel fiber optic bundle (MFOB B) for receiving modulated light having at least two channels to split said received light and to introduce a phase difference of about 90 degrees between said light in said at least two channels;
light detectors for receiving a modulated light and converting it into an electrical signal, said light detectors being connected to individual ends of said at least two channels of said second multichannel fiber optic bundle;
and
wherein said second Multichannel Fiber Optic Bundle for receiving modulated light further comprises groups of optical fibers within each of said at least two channels, said fibers each having a fiber core with a diameter, D.sub.1, such that D.sub.1 <W/2, where W is a period of modulation of said first type of optical track;
fiber core centers of said fibers are placed with spacing L.sub.1 =m(W/4), m taking on integer values;
within one group (row) of fibers, fiber core centers of said fibers are placed within a light path of said optical track and have spacing between centers L.sub.2 =n(W/2), n taking on integer values independently of m;
and distance L.sub.3 between centers of said fibers included in different groups (rows) being given by L.sub.3 =m(W/4).

6 more elements

Dependencies are inferred from the claim text.