GB2338549A - A Rotary Encoder - Google Patents

A Rotary Encoder Download PDF

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Publication number
GB2338549A
GB2338549A GB9812912A GB9812912A GB2338549A GB 2338549 A GB2338549 A GB 2338549A GB 9812912 A GB9812912 A GB 9812912A GB 9812912 A GB9812912 A GB 9812912A GB 2338549 A GB2338549 A GB 2338549A
Authority
GB
United Kingdom
Prior art keywords
focusing
calculating means
tooth
grating
shaped lens
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.)
Withdrawn
Application number
GB9812912A
Other versions
GB9812912D0 (en
Inventor
Ching Shun Wang
Cheng-Liang Hsieh
Shu Fang Lu
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mi-Jung Wang
Liu Yu Shian
Original Assignee
Mi-Jung Wang
Liu Yu Shian
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority to CA002236772A priority Critical patent/CA2236772C/en
Priority to FR9807290A priority patent/FR2779815A1/en
Priority to DE19826009A priority patent/DE19826009C2/en
Application filed by Mi-Jung Wang, Liu Yu Shian filed Critical Mi-Jung Wang
Priority to GB9812912A priority patent/GB2338549A/en
Publication of GB9812912D0 publication Critical patent/GB9812912D0/en
Publication of GB2338549A publication Critical patent/GB2338549A/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M1/00—Analogue/digital conversion; Digital/analogue conversion
    • H03M1/12—Analogue/digital converters
    • H03M1/22—Analogue/digital converters pattern-reading type
    • H03M1/24—Analogue/digital converters pattern-reading type using relatively movable reader and disc or strip
    • H03M1/28—Analogue/digital converters pattern-reading type using relatively movable reader and disc or strip with non-weighted coding
    • H03M1/30—Analogue/digital converters pattern-reading type using relatively movable reader and disc or strip with non-weighted coding incremental
    • H03M1/301—Constructional details of parts relevant to the encoding mechanism, e.g. pattern carriers, pattern sensors
    • 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
    • G01D5/347—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 using displacement encoding scales
    • 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
    • G01D5/38—Forming the light into pulses by diffraction gratings

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Optical Transform (AREA)
  • Photometry And Measurement Of Optical Pulse Characteristics (AREA)
  • Position Input By Displaying (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

A rotary encoder comprising a grating disk disposed between a light source (1) and detector (3) and lens means associated with the slits of the grating in order to focus the light so that light from a first slit, at the detector, does not interfere with light from an adjacent slit. A grating wheel with focussing-type means rather than silts may be used instead; comprising a ring-shaped lens (24) on the input plane and a plurality of tooth-shaped lenses (25) on the output plane, perpendicular to the ring-shaped lens, so that the interfernce of light is minimised.

Description

Title of invention 2338549
FOCUSING-TYPE CALCULATING MEANS Field of the present invention:
The present invention relates to a focusing-type calculating means, more particularly, to a encoder which can prevent the interference phenomenon when the light is emitted toward the photo detector through the grating wheel.
Background of the present invention
The conventional optical encoder is blocking-type encoder, as io shown in Fig. 1. The encoder comprises a grating wheel 60, a light source 70, and a photo detector 80. The light source 70 is an-anged at the proximity of the grating wheel 60 to emit light upon the grating wheel 60. The grating wheel 60 is centered at an axis 50 and is rotated by a driving means (not shown). The grating wheel 60 is provided with a plurality of slit 61 along the distal portion thereof. Moreover, there is an opaque part 62 arranged between two adjacent slits 61. The photo detector 80 is placed at the proximity of the grating wheel 60 and comprises a photosensitive chip 81 to receive the light emitted from the slit 60.
The light emitted from light source 70 is chopped by the slit 61 and the opaque part 62 of the grating wheel 60, and becomes a working beam, when the grating wheel 60 rotates. The working beam is detected by the photo detector 80 and converted to a sinusoidal signal on a oscilloscope. The signal is processed by a rectifier to form four signals (0,0), (0, 1), (1,1), (1,0).
However, according to the wave optics, the light emitted from two slits may interfere to each other, as shown in Fig. 2. Moreover, the interference will cause the malfunction of the photo detector 80.
To eliminate the interference of two adjacent slits, one approach is to bring the photo-sensitive chip 81 of the photo detector 80 near the slit 61, another approach is to make the area of the slit 61 larger than that of the photo-sensitive chip 81 (about larger than 1/3). However, the first approach will make the facbrication complicated, and the second s approach will make the resolution degraded.
As shown in Fig. 3A, D is the light source, C is the gting, A, B are the slits, and S is the photo detector which can move along direction T. Fig. 3B shows the distribution of light intensity wherein N is the average probability, and H is the probability. As shown in Fig. 3B, NI=(HIY is the average intensityp distribution detected by photo detector S, when the slit B is blocked. Moreovel N2=(H2)2is, the average intensity distribution detected by photo detector S, when the slit A is blocked.
If the light passing ffirough slit A and B has no interference, the light intensity distribution detected by photo detector S will be is N,,=N1+N, as shown in Fig. 3C.
However, according to the principle of wave optics, the fight intensity distribution detected by photo detector S is that shown in Fig. 4 due to the interference between two slits. To eliminate the interference, one method is to enable the light to reach the photo detector not by way of the slits; another method is to focus the light before it reaches the photo detector. As shown in Fig. 5, the photo detector can be place between the lens and the focal point of the. lens to eliminate the interference Summary of the present invention
The object of the present invention is to provide a focusing-type calculating means characterized in which a ring-shaped lens is arranged on the input plane of the grating wheel to focus the light emitted from the fight source, and a plurality of tooth-shaped lens each perpendicular to the ring-shaped lens are arranged on the output plane of the grating wheel to focus the working beam after the working beam passing throuah the output plane, therefore the interference problem will be minimized.
The another object of the present invention is to provide a focusingtype calculating means by which the photo sensitive chip can be placed at a farther place from the output plane of the grating wheel without the problem of increasing fabrication complexity and reducing resolution.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when io read in conjunction with the three'a'ppended drawings, in which: Brief dption of draw:
Fig. 1 shows the conventional blocking-type photo encoder.
Fig. 2 shows fight intensity distdbution caused by two-slit interference; Fig. 3A shows the setup of two-slit interference; Fig. 3B shows fight intensity distribution measured by setup in Fig.
3A Fig. 3C is a fictitious graph showing the light intensity distribution measured by setup in Fig. 3A when both slit are open; Fig. 4 is the realistic graph showing the light intensity distribution measured by setup in Fig. 3A when both slit are open; Fig. 5 shows focusing of the working beam according to the present invention; Fig. 6 shows the schematic diagram of the present invention; Fig. 7 shows the front view and side view of the present invention; Fig. 8 shows the four signals (0,0), (0,1), (1,1), (1,0) appearing on a oscilloscope when the wheel of the present Invention rotates; Fig. 9 shows the front view and side view of another embodiment of the present invention; Fig. 10 shows the front view and both side view of still another embodiment of the present invention; and Fig. 11 shows the front view and side view of still another embodiment of the present invention; Fig. 12 is a schematic diagram showing the tooth-shaped lens being replaced by a convex tooth-shaped lens; Fig. 13 is a schematic diagram showing the tooth-shaped lens being replaced by a strip-shaped lens; and Fig. 14 is a schematic diagram showing the tooth-shaped lens being replaced by a tapered lens. Numerals 1 2 21 22 23 24 25 251 252 light source grating wheel wds input plane output plane ring-shaped lens tooth-shaped lens convex portion concave portion 3 photo detector 31 photo sensitive chip Detailed description of the preferred embodiment:
As shown in Fig. 6 and Fig. 7, the focusing-type calculating means according to the present invention comprises a light source 1, a grating wheel 2, and a photo detector 3. The light source 1 is arranged at the proximity of the grating wheel 2, therefore, the light emitted from the lic,ht source 1 will impinge the input plane 21 of the grating wheel 2.
The grating wheel 2 is rotatably arranged on an axis 21 through the center thereo and is rotated by a driving means (tracing ball means). The grating wheel 2 is rotated when the tracing ball means moves. A ring- shaped lens 24 wth radius of curvature RI is arranged on the input plane 21 to focus the light emitted from the fight source 1 - A plurality of toothshaped lens 25 each with radius of curvature R2 are arranged on the output plane 23 of the grating wheel 2. The tooth-shaped lens 25 has a total internal reflection angle smaller than 41.8' and is perpendicular to io the ring-shaped lens 24. According to the lens formula I/f--(1/RI+ I/R2Xn-1), the focal length f depends on R1 and R2.
The photo detector 3 is made of transparent materials, and positioned between the tooth-shaped lens 25 and the focus of the tooth-shaped lens 25, and opposite to the fight source 1. The photo detector 3 comprises upper and lower photo sensitive chip 31 to receive the working beams emitted from the output plane 23.
When the working beam impinges to the input plane 22 of the wheel 2, the ring-shaped lens 24 will focus the beam. After the working beam passing through the output plane 23, the tooth-shaped lens 25 will focus the beam again. Therefore, the interference problem will be minimiZed when the working beam reaches the photo sensitive chip 31 of the photo detector 3 because it has been focused.
When the grating wheel 2 rotates, the light emitted from the light source 1 will be chopped by the grating wheel 2 and forms a working beam. The working beam is detected by the photo detector 30 and converted to a sinusoidal signal on an oscilloscope. The signal is processed by a rectifier to form four signals (0,0), (0,1), (1,1), (1,0), as shown in Fig. 1.
X,6-,k3- shown in Fig. 9, the input plane can be a planar shape, and the focusing work is achieved by the tooth-shaped lens 25.
As shown in Fig. 10, the output plane 25 can be provided with a plurality of tooth-shaped surface, the light emitted from the light source 1 is focused by the ring-shaped lens 24.
As shown in Fig. 11, the input plane can be a planar shape, and the output plane 25 can be provided with a plurality of tooth-shaped surface.
As shown in Fig. 12-14, the tooth-shaped lens 25 can be replaced by a convex tooth-shaped lens (Fig. 12), a strip-sh"d lens (Fig. 13) or a io tapered lens (Fig. 14) to focus the'working beam after the working beam passing through the output plane, therefore the interference problem will be minimized.
The convex portion 251 or concave portion 252 of the strip-shaped lens and the taper lens can be coated with reflection medium, opaque medium or ground to form ground glass to reflect the unwanted light when the working beam is in operation.
To sum up, the present invention can minimize the interference problem when the working beam reaches the photo sensitive chip of the photo detector because it has been focused.
Although the present invention has been described with reference to the two preferred embodiments thereo it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have suggested in the foregoing description, and other will occur to those of ordinary skill in the art. All such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.

Claims (14)

1. A rotary encoder comprising a grating disc interposed between a light source and a light detector, the grating being adapted axially to rotate relative to the light source and detector in a plane substantially perpendicular to a line joining the light source and detector, and lens means associated with the slits of the grating, such that light passing through the slits from the light source to the detector is so focussed that light from a first slit does not interfere,, at the detector, with light from an adjacent slit.
2. A rotary encoder as claimed in claim 1, wherein the grating is comprised of a plurality of lens means, each lens means comprising a slit of the grating.
3. A focusing-type calculating means comprises a light source, a grating wheeL and a photo detector, the fight emitted from said light source impinging the input plane of said grating wheel, said photo detector comprising a set of photo sensitive chip to receive the working beams emitted from said grating wheel, the focusing-type calculating means being characterized in that:
the input plane of said grating wheel has a ring-shaped lens to focus the light emitted from said light source, the output plane of said grating wheel has a plurality of tooth-shaed tens each perpendicular to said ring shaped lens which can focus said working beam after said working beam passing through said output plane, therefore the interference problem will 25be minimized.
4. The focusing-type calculating means as in claim 3, wherein said photodetector is positioned between said tooth-shaped lens and the focal point of said tooth-shaped lens.
5. The focusing type calculating means as in claims 3 or 4, wherein the total internal reflection angle of said tooth-shaped lens is smaller than 41.8'.
6. The focusing-type calculating means as in claims 3 to 5, wherein said input plane of said grating wheel can be planar shape.
7. The focusing-type calculating means as in claims 3 to 6, wherein said output plane of said grating wheel is provided with a plurality of toothshaped surface.
8. The focusing-type calculating means as in claims 3 to 7, wherein said input plane of said grating wheel can be planar shape, and said output plane of said grating wheel is provided with a plurality of tooth-shaped surface.
9. The focusing-type calculating means as in claims 3 to 8, wherein said 20 tooth-shaped lens is replaced by a convex tooth-shaped lens.
10. The focusing-type calculating means as in claims 3 to 8, wherein said tooth-shaped lens is replaced by a strip-shaped lens.
11. The focusing-type calculating means as in claim 10, wherein part of the convex portion or concave portion of said strip-shaped lens can be coated with photo-reflection medium, opaque medium, or ground.
12. The focusing-type calculating means as in claims 3 to 10, wherein said tooth-shaped lens is replaced by a tapered lens.
13. The focusing-type calculating means as in claim 12, wherein part of the convex portion or concave portion of said tapered lens can be coated with photo-reflection medium, opaque medium, or ground.
14. A rotary encoder as described herein with reference to and as illustrated in Figures 5 to 8 as modified by Figures 9, 10, 11, 12, 13 or 14 of the 10 accompanying drawings.
GB9812912A 1998-06-02 1998-06-15 A Rotary Encoder Withdrawn GB2338549A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
CA002236772A CA2236772C (en) 1998-06-02 1998-06-02 Focusing-type calculating means
FR9807290A FR2779815A1 (en) 1998-06-02 1998-06-10 Non-interference rotary encoder
DE19826009A DE19826009C2 (en) 1998-06-02 1998-06-10 Optical encoder
GB9812912A GB2338549A (en) 1998-06-02 1998-06-15 A Rotary Encoder

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
CA002236772A CA2236772C (en) 1998-06-02 1998-06-02 Focusing-type calculating means
FR9807290A FR2779815A1 (en) 1998-06-02 1998-06-10 Non-interference rotary encoder
DE19826009A DE19826009C2 (en) 1998-06-02 1998-06-10 Optical encoder
GB9812912A GB2338549A (en) 1998-06-02 1998-06-15 A Rotary Encoder

Publications (2)

Publication Number Publication Date
GB9812912D0 GB9812912D0 (en) 1998-08-12
GB2338549A true GB2338549A (en) 1999-12-22

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB9812912A Withdrawn GB2338549A (en) 1998-06-02 1998-06-15 A Rotary Encoder

Country Status (4)

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CA (1) CA2236772C (en)
DE (1) DE19826009C2 (en)
FR (1) FR2779815A1 (en)
GB (1) GB2338549A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101514909B (en) * 2008-02-22 2011-07-27 鸿富锦精密工业（深圳）有限公司 Optical code disc and corresponding optical encoder

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101709982B (en) * 2009-11-05 2011-06-15 无锡鑫亚电子有限公司 Rotary encoder

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB991873A (en) * 1961-12-04 1965-05-12 Hensoldt & Soehne Optik Equipment for indicating the amount of the displacement of a moving part
GB1523287A (en) * 1974-10-10 1978-08-31 Papst Motoren Kg Incrementally controllable motor drive
US4757196A (en) * 1983-09-27 1988-07-12 Mitsubishi Denki Kabushiki Kaisha Optical encoder and method for producing same
EP0474149A2 (en) * 1990-09-05 1992-03-11 Matsushita Electric Industrial Co., Ltd. Optical encoder
JPH08201114A (en) * 1995-01-24 1996-08-09 Matsushita Electric Ind Co Ltd Optical encoder

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR77221E (en) * 1960-02-23 1962-02-02 Levallois Optique Et Prec Photoelectric camera for checking or controlling positions
GB2049165A (en) * 1979-05-08 1980-12-17 Pye Ltd Dual beam spectrophotometer
US4528448A (en) * 1982-05-13 1985-07-09 Benson, Inc. Plane linear grating for optically encoding information
JPS5963517A (en) * 1982-10-04 1984-04-11 Nippon Kogaku Kk <Nikon> Photoelectric encoder
JP3170902B2 (en) * 1992-09-30 2001-05-28 キヤノン株式会社 Signal processing method and encoder using the same
JPH10239108A (en) * 1997-02-21 1998-09-11 Fanuc Ltd Optical encoder

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB991873A (en) * 1961-12-04 1965-05-12 Hensoldt & Soehne Optik Equipment for indicating the amount of the displacement of a moving part
GB1523287A (en) * 1974-10-10 1978-08-31 Papst Motoren Kg Incrementally controllable motor drive
US4757196A (en) * 1983-09-27 1988-07-12 Mitsubishi Denki Kabushiki Kaisha Optical encoder and method for producing same
EP0474149A2 (en) * 1990-09-05 1992-03-11 Matsushita Electric Industrial Co., Ltd. Optical encoder
JPH08201114A (en) * 1995-01-24 1996-08-09 Matsushita Electric Ind Co Ltd Optical encoder

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
WPI Abstract Accession No. 96-415443 & JP8201114 (Matsushita) (09.08.96) (see abstract) *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101514909B (en) * 2008-02-22 2011-07-27 鸿富锦精密工业（深圳）有限公司 Optical code disc and corresponding optical encoder

Also Published As

Publication number Publication date
GB9812912D0 (en) 1998-08-12
FR2779815A1 (en) 1999-12-17
CA2236772C (en) 2003-07-29
DE19826009C2 (en) 2002-06-20
DE19826009A1 (en) 1999-12-16
CA2236772A1 (en) 1999-12-02

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