Optical waveguides – Planar optical waveguide
Patent
1994-09-28
1996-10-01
Ngo, John
Optical waveguides
Planar optical waveguide
25022718, 385 1, 385901, G02B 600
Patent
active
055617328
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to data transmission by means of electromagnetic radiation and is applicable by way of example to position encoders.
Data transmission by means of electromagnetic radiation, e.g. light, is a useful technique in cases where data has to be transferred across a gap and/or between relatively movable parts. As a special case, a digital position encoder modulates the radiation with a code dependent upon the relative positions of two parts, one of which carries code elements which are able to modulate the radiation, e.g. by reflection or transmissivity.
According to a first aspect of the invention there is provided a device for data transmission by electromagnetic radiation comprising a member constituting a waveguide, means for providing pulsed or modulated radiation comprising a first frequency to enter the waveguide and means for detecting radiation at a second frequency at an end surface of the waveguide, the member having within it fluorescent material responsive to radiation at the first frequency to emit radiation at the second frequency, the emitted radiation being guided by the waveguide to the end surface.
According to a second aspect of the invention there is provided a position detector for detecting the relative positions of two parts comprising a data transmission device according to the above first aspect.
In one embodiment the means for providing modulated radiation comprises a plurality of portions relatively opaque to radiation at the first frequency and disposed between the waveguide and the source of radiation so that the radiation will be modulated by the pattern of said portions.
According to a third aspect of the invention there is provided an infusion pump transmission comprising a position detector according to the above second aspect, one of said parts being means for operating a syringe infusion pump plunger and the second being means arranged to be connected to the syringe infusion pump body.
According to a fourth aspect of the invention, there is provided a device for data transmission by electromagnetic radiation comprising a waveguide for the radiation, the waveguide having two, opposed, major surfaces, one of which provides an input for the radiation to the waveguide, an end or edge surface of the waveguide providing for output of radiation, there being source means of radiation for supplying radiation to said one major surface, detector means responsive to the directed radiation emitted from said end or edge surface, and means in the waveguide and responsive to input radiation for directing radiation towards the end or edge surface, that radiation being guided between the major surfaces.
In one example, the waveguide may be of a type containing fluorescent material having a maximum of absorption in the region of the frequency of the input radiation and a maximum of emission at a frequency to which the detector means is responsive.
There may be a plurality of elements relatively opaque to said pulsed radiation between the source and the waveguide, said elements being arranged according to an n-bit digital position code. The source means may comprise n individual sources for illuminating the respective bits in sequence, the device being arranged so that a single detector can be used to receive a series of bits defining the relative position of the source means and the code.
A waveguide doped or loaded with fluorescent material is readily obtainable at low cost. By virtue of its ability to emit light at a specific frequency when subjected to light at another, it proves to have a relatively good output light intensity compared with the incident intensity, i.e. good transfer properties.
For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:
FIG. 1 illustrates a data transmission device having a waveguide;
FIG. 2 illustrates a linear position detector;
FIG. 3 illustrates the drive and detector circuits for the detector of FIG. 2;
REFERENCES:
patent: 4650992 (1987-03-01), Ruhrmann
patent: 4818710 (1989-04-01), Sutherland et al.
patent: 4870292 (1989-09-01), Alpert et al.
Coventry Univ. Enterprises & Welmed Ltd.
Ngo John
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