WO1996012304A1 - Optical potentiometer - Google Patents
Optical potentiometer Download PDFInfo
- Publication number
- WO1996012304A1 WO1996012304A1 PCT/GB1995/002401 GB9502401W WO9612304A1 WO 1996012304 A1 WO1996012304 A1 WO 1996012304A1 GB 9502401 W GB9502401 W GB 9502401W WO 9612304 A1 WO9612304 A1 WO 9612304A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- gap
- tracks
- light source
- optical potentiometer
- light
- Prior art date
Links
- 230000003287 optical effect Effects 0.000 title claims abstract description 36
- 229910021417 amorphous silicon Inorganic materials 0.000 claims abstract description 13
- WYTGDNHDOZPMIW-RCBQFDQVSA-N alstonine Natural products C1=CC2=C3C=CC=CC3=NC2=C2N1C[C@H]1[C@H](C)OC=C(C(=O)OC)[C@H]1C2 WYTGDNHDOZPMIW-RCBQFDQVSA-N 0.000 claims description 4
- 239000012141 concentrate Substances 0.000 claims description 2
- 239000000126 substance Substances 0.000 claims 1
- 239000012780 transparent material Substances 0.000 claims 1
- 229910052751 metal Inorganic materials 0.000 description 7
- 239000002184 metal Substances 0.000 description 7
- 238000005229 chemical vapour deposition Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 229920003023 plastic Polymers 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 239000011651 chromium Substances 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 125000006850 spacer group Chemical group 0.000 description 2
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052793 cadmium Inorganic materials 0.000 description 1
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 1
- CJOBVZJTOIVNNF-UHFFFAOYSA-N cadmium sulfide Chemical compound [Cd]=S CJOBVZJTOIVNNF-UHFFFAOYSA-N 0.000 description 1
- 229910052980 cadmium sulfide Inorganic materials 0.000 description 1
- UHYPYGJEEGLRJD-UHFFFAOYSA-N cadmium(2+);selenium(2-) Chemical compound [Se-2].[Cd+2] UHYPYGJEEGLRJD-UHFFFAOYSA-N 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000005137 deposition process Methods 0.000 description 1
- 239000002019 doping agent Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 231100000614 poison Toxicity 0.000 description 1
- 230000007096 poisonous effect Effects 0.000 description 1
- 239000004417 polycarbonate Substances 0.000 description 1
- 229920000515 polycarbonate Polymers 0.000 description 1
- 238000004382 potting Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 239000011669 selenium Substances 0.000 description 1
- 229910052711 selenium Inorganic materials 0.000 description 1
- 238000007738 vacuum evaporation Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/12—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof structurally associated with, e.g. formed in or on a common substrate with, one or more electric light sources, e.g. electroluminescent light sources, and electrically or optically coupled thereto
- H01L31/16—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof structurally associated with, e.g. formed in or on a common substrate with, one or more electric light sources, e.g. electroluminescent light sources, and electrically or optically coupled thereto the semiconductor device sensitive to radiation being controlled by the light source or sources
- H01L31/161—Semiconductor device sensitive to radiation without a potential-jump or surface barrier, e.g. photoresistors
- H01L31/164—Optical potentiometers
Definitions
- This invention relates to an optical potentiometer.
- Optical potentiometers have the advantage over mechanical potentiometers that there is no wear of the electrically resistive track because there is no moving element in mechanical contact with the track.
- cadmium sulphide or cadmium selenide is screen printed onto an insulating substrate to act as a photoconductive layer, and resistive metal (e.g. chromium) contacts are provided over the photoconductive layer and etched to define a pair of mutually parallel, electrically resistive tracks separated by a gap typically having a width of about 20//m.
- resistive metal e.g. chromium
- the resultant light beam is focused on the gap between the tracks so that the photoconductive layer become electrically conducting at the location of light incidence and electrically bridges the tracks.
- One disadvantage of such an arrangement is that the screen printed photosensitive layer does not have consistent photoconductive properties and so it can be difficult to achieve a smooth and accurately proportional change in electrical output as relative movement between the control element and the tracks takes place.
- Another disadvantage is that cadmium and selenium are both poisonous.
- an optical potentiometer comprising a pair of mutually spaced electrically resistive tracks defining a gap, a photoconductive layer exposed in the gap between the tracks, a light source, and means for directing light from the light source to the gap between the tracks, the tracks and the directing means being relatively movable to vary the location at which the gap between the tracks is illuminated by the light source in use, characterised in that the photoconductive layer is a photosensitive amorphous silicon layer.
- the photosensitive amorphous silicon layer can be applied by chemical vapour deposition with very consistent photoconductive properties.
- the tracks will normally be formed of metal.
- the use of metal tracks may cause non-linearities in the output signal as a result of photovoltaic effects due to the formation of an electronic junction between the tracks and the photoconductive layer. It is therefore a object of a second aspect of the present invention to obviate or mitigate this disadvantage.
- an optical potentiometer comprising a pair of mutually spaced electrically resistive tracks defining a gap, a photoconductive layer exposed in the gap between the tracks, a light source, and means for directing light from the light source to the gap between the tracks, the tracks and the directing means being relatively movable to vary the location at which the gap between the tracks is illuminated by the light source in use, characterised in that there is provided a respective ohmic contact layer separating the photoconductive layer from each track.
- the photoconductive layer is a photosensitive amorphous silicon layer in accordance with said first aspect of the present invention.
- the tracks are preferably electrically resistive metal tracks.
- the ohmic contact layer is defined by an n + interface having a thickness of 20 to 200A.
- an optical potentiometer comprising a pair of mutually spaced electrically resistive tracks defining a gap, a photoconductive layer exposed in the gap between the tracks, a light source, and means for directing light from the light source into the gap between the tracks, characterised in that the directing means includes a reflector arrangement which is shaped and disposed so as to concentrate light from the light source into the gap.
- the optical potentiometer according to said third aspect of the present invention is most preferably a rotary potentiometer where at least part of the reflector arrangement is mounted for rotary movement on a shaft, the tracks and gap being arcuate and centred upon the axis of rotation of the shaft.
- said reflector arrangement includes a reflective surface lying on the surface of at least one conic section.
- the conic section is an ellipse. Concentration of the light may be effected by locating the reflecting surface so that the light source and the gap lie at respective focal points of the ellipse.
- a more compact arrangement can be achieved by positioning at least one mirror (e.g. a planar or conic section mirror) relative to the elliptical reflecting surface and to the light source in such a way that at least one of the light source and the gap is disposed at a, or a respective, virtual focal point of the ellipse, e.g. so that light from the light source which has reflected off the mirror appears to have emanated from the actual focal point.
- This principle is illustrated in Figs 2a and 2b where light source L is disposed at the virtual focal point F v corresponding to focus F 2 .
- the cross-sectional shape i.e. the shape ir, any plane perpendicular to the elliptical section illustrated in Fig 2b
- the mirror (mirror M) forms part of the reflector arrangement.
- At least one, and preferably both, of the form of the reflective surface and the form of the mirror are defined by a body which is preferably formed of plastics material and which has an appropriately shaped surface or surfaces rendered suitably reflective, e.g. by deposition of a reflective film, such as by a vacuum evaporation process.
- the body has a hole therein which receives the rotor shaft and which has an inclined surface defining the mirror. It may not be necessary for a reflective film to be provided on such inclined surface since it may be inherently reflective due to total internal reflection.
- the body may be solid and in which case it should be transparent and rendered suitably reflective as necessary by provision of a suitably reflective film.
- a surface of the body through which light passes in use is shaped so as to permit light reflected off at least one internal reflective surface in the body to be concentrated in the gap between the tracks.
- Such surface through which light passes may be planar or non-planar.
- the body may be of shell-like construction with an internally dished form defining at least one of the shape of the reflective surface and the shape of the mirror.
- the material of construction may be opaque (e.g. metallic) provided that the surface is highly reflective or has a highly reflective coating thereon.
- the gap between the tracks is typically about 20 ⁇ m.
- the light beam which is incident upon the gap typically has a diameter of about 0.5 to 1mm. This may not enable particularly effective use of the light beam.
- an optical potentiometer wherein the gap is of serpentine shape, and the arrangement is such that, in use, the beam of light from the light source is scanned along the direction of longitudinal extent of the serpentine gap.
- the serpentine gap is defined between interdigitated fingers on the respective tracks.
- Fig 3 is an axial section through an optical potentiometer according to the present invention
- Fig 4 is a plan view of a substrate disk carrying the potentiometer tracks
- Fig 5 is a scrap section on the line A-A of Fig 4, and
- Fig 6 is a much enlarged plan view showing a small part of a preferred design of tracks.
- the optical potentiometer comprises a housing 10 with lid 12 carrying bearings 14 in which an operating shaft 16 is rotatably mounted.
- the lower end of the shaft 16 carries a shaped reflector body 18 which, in this embodiment, is formed of a solid transparent plastics (eg a polycarbonate plastic material) moulded with an accurately chamfered recess 20 therein to receive the correspondingly chamfered lower end of shaft 16.
- a solid transparent plastics eg a polycarbonate plastic material
- an upper surface 24 of the body 18 is elliptically curved and has focal points F, and F 2 .
- the upper surface 24 is arcuately curved, with the arcs being centred on the focal axis of the ellipse.
- the chamfered surface 22 is planar and acts as a mirror.
- the surface 24 may be provided with a vacuum evaporated film of aluminium thereon to render it internally reflective.
- the same film may be provided within the recess 18 over the chamfered surface 22.
- the surface 22 is so inclined and positioned relative to surface 24 and the axis of rotation R that light rays passing along the axis of rotation R and incident upon the surface 22 are reflected towards the surface 24 to be re-reflected so as to pass through the focal point F,.
- point F v on axis R is the virtual focus of F 2 .
- the lower surface of the body 18 is planar and is disposed a short distance above a fixed, circular glass plate 26 defining a transparent substrate.
- the plate 26 is disposed perpendicularly to the axis of rotation R and is retained against an annular mounting flange 28 by means of a retaining plate 30 and intervening annular spacer 32.
- the retaining plate 30 has a central holder 34 which holds a light- emitting diode 36 in alignment with the axis of rotation R.
- the light emitting diode has a relatively narrow cone of emission (about 20°) which is directed along the axis of rotation R towards the mirror 22.
- the tracks 40 and 42 and the gap 44 are centred on the axis of rotation R.
- the focal point F lies substantially in the gap 44.
- the tracks 40 and 42 are formed on an amorphous silicon layer 46 provided on undersurface of the plate 26, there being an n + doped layer 48 between the amorphous silicon layer 46 and the tracks 40 and 42.
- the amorphous silicon layer 46 is exposed in the gap 44 between the tracks 40 and 42.
- the amorphous silicon layer 46 is applied to the glass plate 26 by chemical vapour deposition in a per se known manner to a depth which is typically about 1 ⁇ m.
- an n + dopant e.g. phosphinc
- the layer 40 which typically has a thickness of 20 to 200A.
- the resultant layers are then masked and etched to produce an annular shape where the centre of the plate 26 is left clear for light transmission therethrough.
- a resistive metal e.g.
- chromium film is deposited on the n + doped layer 48 and then masked and etched to define the tracks 40 and 42 with intervening gap 44, the latter extending through the layer 48 so that the amorphous silicon layer 46 is exposed within the gap 44.
- the etching of the n + layer and the resistive metal track can both be carried out after the whole deposition process is complete.
- Leads 50 are then attached to adjacent ends of the tracks 40 and 42.
- the tracks 40 and 42 which are delicate items, can then be protected against ingress of moisture and other contamination by potting them in a suitable resin together with the LED 36 and amplifier electronics (not shown) provided in the cavity defined within the spacer 32.
- the reflector 24 causes the conical I y expanding light beam emanating from the light emitting diode 36 to be concentrated by being brought partly to a focus within the gap 44.
- the diameter of the beam incident upon the gap 44 is about 1 mm, whilst the gap 44 has a width of 20/ m.
- that region of the amorphous silicon layer 46 which is exposed in the illuminated region of the gap 44 is rendered photoconductive and electrically bridges the tracks 40 and 42 at such region. Because the tracks 40 and 42 are resistive metal tracks, it will be appreciated that the resistance across the leads 50 will depend upon the rotary position of the shaft 16 relative to the tracks 40 and 42.
- a track and gap arrangement as illustrated on a very much larger scale in Fig 6 where it will be seen that the tracks 40 and 42 are provided with respective narrow fingers 40a and 42a which are interdigitated so that the gap 44 is of locally serpentine form extending transversely of the general arcuate direction of extent of the gap 44.
- Such an arrangement reduces the resistance of the conductive path at that region of the photoconductive layer 46 which, at any instant, is being illuminated.
Landscapes
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Electromagnetism (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Optical Transform (AREA)
Abstract
Description
Claims
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP95933526A EP0787360A1 (en) | 1994-10-15 | 1995-10-11 | Optical potentiometer |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9420833.7 | 1994-10-15 | ||
GB9420833A GB9420833D0 (en) | 1994-10-15 | 1994-10-15 | Optical potentiometer |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1996012304A1 true WO1996012304A1 (en) | 1996-04-25 |
Family
ID=10762916
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB1995/002401 WO1996012304A1 (en) | 1994-10-15 | 1995-10-11 | Optical potentiometer |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0787360A1 (en) |
GB (1) | GB9420833D0 (en) |
WO (1) | WO1996012304A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE19944025A1 (en) * | 1999-09-14 | 2001-03-15 | Siemens Ag | Bipole-type variable resistance |
WO2005005937A1 (en) * | 2003-07-03 | 2005-01-20 | Robert Bosch Gmbh | Optical position sensor |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2386111A1 (en) * | 1977-04-01 | 1978-10-27 | Bonohm Sa | Photo variable potentiometer with photoresistive surface - is without positionally variable electrical contact and uses fibre or prismatic light guides |
EP0005548A1 (en) * | 1978-05-23 | 1979-11-28 | Heimann GmbH | Optoelectrial potentiometer |
JPS6266686A (en) * | 1985-09-19 | 1987-03-26 | Fujitsu Ltd | Light potentiometer and manufacture thereof |
DE3709614A1 (en) * | 1987-03-24 | 1988-10-20 | Messerschmitt Boelkow Blohm | Method and device for determining position |
-
1994
- 1994-10-15 GB GB9420833A patent/GB9420833D0/en active Pending
-
1995
- 1995-10-11 EP EP95933526A patent/EP0787360A1/en not_active Withdrawn
- 1995-10-11 WO PCT/GB1995/002401 patent/WO1996012304A1/en not_active Application Discontinuation
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2386111A1 (en) * | 1977-04-01 | 1978-10-27 | Bonohm Sa | Photo variable potentiometer with photoresistive surface - is without positionally variable electrical contact and uses fibre or prismatic light guides |
EP0005548A1 (en) * | 1978-05-23 | 1979-11-28 | Heimann GmbH | Optoelectrial potentiometer |
JPS6266686A (en) * | 1985-09-19 | 1987-03-26 | Fujitsu Ltd | Light potentiometer and manufacture thereof |
DE3709614A1 (en) * | 1987-03-24 | 1988-10-20 | Messerschmitt Boelkow Blohm | Method and device for determining position |
Non-Patent Citations (2)
Title |
---|
"Ein elektro-optisches Potentiometer", ELEKTRONIK, no. 11, pages 344 * |
PATENT ABSTRACTS OF JAPAN vol. 011, no. 257 (E - 534) 20 August 1987 (1987-08-20) * |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE19944025A1 (en) * | 1999-09-14 | 2001-03-15 | Siemens Ag | Bipole-type variable resistance |
WO2005005937A1 (en) * | 2003-07-03 | 2005-01-20 | Robert Bosch Gmbh | Optical position sensor |
Also Published As
Publication number | Publication date |
---|---|
EP0787360A1 (en) | 1997-08-06 |
GB9420833D0 (en) | 1994-11-30 |
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