GB2130364A - Position detecting apparatus - Google Patents
Position detecting apparatus Download PDFInfo
- Publication number
- GB2130364A GB2130364A GB08327764A GB8327764A GB2130364A GB 2130364 A GB2130364 A GB 2130364A GB 08327764 A GB08327764 A GB 08327764A GB 8327764 A GB8327764 A GB 8327764A GB 2130364 A GB2130364 A GB 2130364A
- Authority
- GB
- United Kingdom
- Prior art keywords
- light
- light sources
- position detecting
- windows
- detecting apparatus
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 230000001419 dependent effect Effects 0.000 claims description 3
- 238000003491 array Methods 0.000 description 11
- 238000000034 method Methods 0.000 description 3
- 230000003287 optical effect Effects 0.000 description 3
- 239000000428 dust Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/36—Forming the light into pulses
- G01D5/363—Direction discrimination
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optical Transform (AREA)
- Length Measuring Devices By Optical Means (AREA)
Abstract
Position detecting apparatus for determining the position of, for example, a rotatable shaft comprises two spaced light sources, a light detector and an array of regularly spaced light transmitting windows located between them and moved by the shaft. The two light sources are spaced apart by a distance which is a multiple of the distance between adjacent windows the multiple not being a whole number. The two light sources produce alternate pulses of light and the light detector receives these pulses and decodes their intensities to determine the position of the array of windows, and hence the position of the shaft. The light sources are preferably each an array of L.E.D.'s with regular spacing equal to that of the windows. <IMAGE>
Description
SPECIFICATION
Position detecting apparatus
This invention relates to position detecting appar atus for two relatively movable bodies and more particularly to position detecting apparatus which uses an optical encoder system for determining the relative positions of the bodies.
In most optical encoders the ultimate accuracy of the encoder is determined by both the accuracy of the code and the critical mechanical alignment ofthe components. Mechanical alignment can be consider ablyfacilitated if the number of movable components is minimal, and by using edge emitting light emitting diode arrays and special code layouts only one component needs to be critically adjusted to achieve maximum accuracy.
With optical encoders utilising the diffraction princi plethere is often a necessityto extend the direct reading accuracy ofthe encoder beyond the limits set by diffraction. This is possible if interpolation methods are used when relatively large lighttransmitting areas are involved.
It is an object of the present invention therefore to provide position detecting apparatus which uses simple relatively large area light sources in combination with an encoder device to substantially increase the accuracyofthe apparatus.
According to the present invention position detecting apparatusfortwo relatively movable bodies comprises two spaced light sources connected to one body and a light transmitting memberhavinga plurality of regularly spaced windows connected to the other body, the lighttransmitting member of the two light sources being located adjacentto each other and in alignment, light detecting means located to received light from the two light sources through the lighttransmitting member, the spacing ofthetwo light sources being a multiple, which is not a whole number, ofthe spacing of the windows in the light transmitting member and the two light sources being adapted to produce light pulses alternately such that the intensity of each light pulse received by the light detecting means is dependent upon the relative position ofthetwo light sources and the light transmitting member, there being provided decoding meansfordetermining the relative position ofthetwo bodies according to the intensities of each pair of pulses.
Preferably the windows and the two light sources are parallel and adapted to relatively move on parallel paths.
Thewindows maybearranged in a lineararrayand be adapted to move along a straight line relative to the two light sources, or the windows can be arranged in an arcuate array and be adapted to move along an arcuate path relative to the two light sources.
Thelightsources preferably comprise lightemitting diodes and each light source preferably comprises a regularly spaced array of light emitting diodes, the light emitting diodes in each array having thesame shape and spacing as the piurality of windows.
An embodiment ofthe invention will now be described by way of example only with reference to the accompanying drawing which is a pictorial view of a position detecting apparatus according to the invention.
This apparatus consists of a first body having connected to it a monolithic multi-element LED array fabricated on a single semiconductor chip 10 such that it consists of a linear array 12 of light emitting elements 14 of regular spacing x, separated by a distance y such thaty = (n + 1/4) X, in which n is awhole number, from a similar linear array 16 again of the same regular spacing Xwhich is colinearwith the first array. The distance x and the shape of the light emitting elements 14 is the same as the separation and shape of a plurality of lighttransparentwindows 20 formed in a linear array on a lighttransmitting member 18 connected to a second body.
The complete assembly is aligned so that the arrays 12 and 16 are parallel to the member 18 and separated by a distnce 22 and the combined arrays 12 and 16 can movetogetherin either direction along the arrow 24 relative to the member 18. The LED elements 14 in the arrays 12 and 16 together pass in and out of coincidence with the lighttransparentwindows 20 in the member 18 but 1/4 of the distance x out of phase with each other. By rapidly alternately switching the light output from the arrays 12 and 16 a single detector 26 located on the opposite side ofthe member 18 receives pulses of light alternately from the arrays 12 and 16. The strength ofthese pulses of light relate directly to the degree of coincidence of the arrays 12 and 16 with the windows 20.By decoding the strength ofthesetransmitted light signals from the analogue to a digital form the position ofthe arrays 12 and 16 relative to the member 18 can be accurately determined to a fraction ofthe distance x, and if the arrays 12 and 16 are moving relative to the member 18 the direction and speed of relative movement can be measured. Hence the position, direction and speed of movement ofthe first body relative to the second body can be determined. The arrays 12 and 16 and the member 18 may also be fashioned to form arcs of circular arrays suitableforshaft encoders. Thetransmitted light signals could then be processed to subdivide the fine track divisions of the shaft encoder giving added resolution.
With this arrangementthere is only one component that needs to be critically aligned to achieve the maximum accuracy, i.e. the chip 10 or the member 18 and all critical dimensions and other alignments are assigned to standard mask making and photolithic processes. Because of the multiple apertues used, the whole arrangement is less dependent upon the
perfection of individual elements and spurious
pinholes and dust effects. Since the multiple LED elements are small (typically 1 x 20 m) the physical dimensions of any device using this technique can be smallerthanencodersystemsusing largerarea LED
arrangements and masks to define the emitting areas.
Claims (8)
1. Position detecting apparatusfortwo relatively movable bodies comprising two spaced light sources connected to one body and a lighttransmitting member having a plurality of regularly spaced windows connected to the other body, the light transmit- ting member having a plurality of regularly spaced windows connected to the other body, the light transmitting member and the two light sources being located adjacent to each other and in alignment, light detecting means located to receive light from the two light sources through the lighttransmitting member, thespacing ofthetwo lightsourcesbeing multiple, which is not a whole number, ofthe spacing ofthe windows in the light transmitting member and the two lightsources being adapted to produce light pulses alternately such that the intensity of each light pulse received bythe light detecting means is dependent upon the relative position ofthe two light sources and the lighttransmitting member, there being provided decoding means for determining the relative position ofthe two bodies according to the intensities of each pair of pulses.
2. Position detecting apparatus as claimed in claim 1 in which the windows and the two light sources are parallel and adapted to relatively move on parallel paths.
3. Position detecting apparatus as claimed in claim 2 in which the windows are arranged in a linear array and are adapted to move along a straight line relative to the two light sources.
4. Position detecting apparatus as claimed in claim 2 in which thewindows are arranged in anarcuate array and are adapted to move along an arcuate path relative to the two light sources.
5. Position detecting apparatus as claimed in any preceding claim in which the light sources comprise light emitting diodes.
6. Position detecting apparatus as claimed in claim 5 in which each light source comprises a regularly spaced array of light emitting diodes.
7. Position detecting apparatus as claimed in claim 6 in which the light emitting diodes in each array have the same shape and spacing as the plurality of windows.
8. Position detecting apparatus constructed and adapted to operate substantially as hereinbefore described with reference to the accompanying drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08327764A GB2130364B (en) | 1982-10-29 | 1983-10-17 | Position detecting apparatus |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8231037 | 1982-10-29 | ||
| GB08327764A GB2130364B (en) | 1982-10-29 | 1983-10-17 | Position detecting apparatus |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8327764D0 GB8327764D0 (en) | 1983-11-16 |
| GB2130364A true GB2130364A (en) | 1984-05-31 |
| GB2130364B GB2130364B (en) | 1986-02-19 |
Family
ID=26284267
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08327764A Expired GB2130364B (en) | 1982-10-29 | 1983-10-17 | Position detecting apparatus |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2130364B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2465372A (en) * | 2008-11-14 | 2010-05-19 | Nicholas James Adkins | Optical displacement transducer |
| EP2647966A1 (en) * | 2012-04-04 | 2013-10-09 | Siemens Aktiengesellschaft | Data encoder for receiving position information and method for operating same |
-
1983
- 1983-10-17 GB GB08327764A patent/GB2130364B/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2465372A (en) * | 2008-11-14 | 2010-05-19 | Nicholas James Adkins | Optical displacement transducer |
| GB2465372B (en) * | 2008-11-14 | 2013-10-30 | Nicholas James Adkins | Optical displacement transducer |
| EP2647966A1 (en) * | 2012-04-04 | 2013-10-09 | Siemens Aktiengesellschaft | Data encoder for receiving position information and method for operating same |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2130364B (en) | 1986-02-19 |
| GB8327764D0 (en) | 1983-11-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |