GB2194042A - Displacement measurement - Google Patents
Displacement measurement Download PDFInfo
- Publication number
- GB2194042A GB2194042A GB08619779A GB8619779A GB2194042A GB 2194042 A GB2194042 A GB 2194042A GB 08619779 A GB08619779 A GB 08619779A GB 8619779 A GB8619779 A GB 8619779A GB 2194042 A GB2194042 A GB 2194042A
- Authority
- GB
- United Kingdom
- Prior art keywords
- gratings
- detector
- source
- members
- movement
- 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- Withdrawn
Links
- 238000006073 displacement reaction Methods 0.000 title claims abstract description 20
- 238000005259 measurement Methods 0.000 title description 4
- 230000033001 locomotion Effects 0.000 claims abstract description 23
- 230000005670 electromagnetic radiation Effects 0.000 claims description 8
- 230000005855 radiation Effects 0.000 claims description 7
- 239000013307 optical fiber Substances 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 3
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000012544 monitoring process 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
- G01D5/38—Forming the light into pulses by diffraction gratings
Abstract
Moire fringe displacement measuring apparatus comprises a light source (10), a detector (13), and first and second gratings (1) (5) disposed relative one to the other such that one or more moire fringes are produced. A relative displacement between the first and second gratings (1) (5) causes a corresponding movement of the one or more moire fringes which is detected by the detector (13) and analysed by a microprocessor (15). The markings on at least one of the first and second gratings (1) (5) are reflective and the detector (13) is positioned on the same side of the first and second gratings as the source (10). <IMAGE>
Description
SPECIFICATION
Displacement measurement
This invention relates to the measurement of a relative displacement using a moire fringe measurement technique.
In known moire fringe measurement devices first and second gratings are disposed adjacent to one another such that one or more moire fringes are produced. When the gratings move relative to one another, the fringe pattern travels at right angles to the direction of movement. A beam of light is passed through the gratings and directed onto a detector such as a photo-electric sensor. By monitoring the movement of the fringes, the degree and direction of the relative movement can be established. The present invention seeks to provide an improvement to this type of displacement detector.
Accordingly, there is provided apparatus for measuring displacement between first and second members comprising first and second gratings; means for supporting the first grating for movement with the first member; means for supporting the second grating for movement with the second member, the arrangement being such that the first and second gratings are disposed relative one to the other such that one or more moire fringes are produced, a relative displacement between the first and second members causing a corresponding movement of the one or more moire fringes; a source adapted to illuminate first and second gratings with electro-magnetic radiation; a detector adapted to monitor the radiation from the source incident thereon; and an electronic processing unit adapted to receive signals from the detector and to calculate therefrom the relative displacement between the first and second members; characterised in that the markings on at least one of the first and second gratings are reflective and the detector is positioned on the same side of the first and second gratings as the source.
By positioning the detector on the same side of the gratings as the source and employing the reflection of the radiation, the occasionally difficult requirement for access to the opposite side of the gratings is avoided.
Indeed if desired, the source and detector may be located adjacent one to the other conceivably in a single integral unit. Preferably the markings on both the first and second gratings are reflective.
Conveniently the source is a light source and the detector is a photo-detector. There is conveniently provided an optical fibre between the source and the first and second gratings, adapted to transmit electro-magnetic radiation to eliminate the gratings. Additionally or alternatively, there is provided an optical fibre between first and second gratings and the detector, adapted to transmit electro-magnetic radiation thereto. Where both input and output fibres are provided, they may conveniently lie alongside one another conceivably laterally connected one to the other in the form of a ribbon.
The invention further resides in a method of measuring displacement employing the above described apparatus. In particular, a method of measuring displacement between first and second members is characterised by the steps of providing first and second gratings; supporting the first grating for movement with the first member; supporting the second grating for movement with the second member, the arrangement being such that the first and second gratings are disposed relative one to the other such that one or more moire fringes are produced, a relative displacement between the first and second members causing a corresponding movement of the one or more moire fringes; illuminating the first and second gratings with electro-magnetic radiation; detecting the radiation reflected from at least one of the first and second gratings; and calculating, from the amount of radiation reflected from the at least one of the first and second gratings, the relative displacement of the first and second members.
The invention will now be further described by way of example only, with reference to the accompanying drawing, which is a schematic diagram of apparatus according to the invention.
Referring to the drawing, an index grating 1 is attached by means of grating support 2 and cantilever arm 3 to the stationary housing 4 of a machine tool such as a hydraulic ram. A second grating in the form of a scale 5 is attached by a similar support 6 and arm 7 to the movable piston 8 of the ram. Both index grating 1 and scale 5 are ruled with reflective markings 9 in a similar parallel pattern, the pattern of the index grating 1 being at a slight angle to the pattern of the scale 5 such that moire fringes are produced.
The index grating 1 and scale 5 are illuminated with light from a source 10, transmitted by means of a input optical fibre 11. Light reflected from the reflective-markings is transmitted by means of a similar optical fibre 12, this output fibre leading to a photo-detector 13. Signals from the photo-detector 13 are fed via a line 14 to a microprocessor 15 for analysis.
Movement of the piston 8 within the housing 4 results in the scale 5 being moved laterally with respect to the index grating 1. In the illustrated arrangement, where the ruled markings are in the form of substantially vertical parallel lines, lateral movement of the scale 5 will result in a vertical movement of the moire fringe pattern. This movement of the moire fringe patent will cause a corresponding change in the light reflected from the markings 9 as detected by the photo-detector 13. The microprocessor 15 calculates, from the signals from the photo-detector 13, the change in the moire fringe pattern and hence the displacement of the piston 8 within the cylinder 4.
The direction of motion of the piston 4 may also be calculated by the microprocessor 15, typically by a calculation of the direction of movement of the moire fringes by means of analysis of whether the amount of light reaching the photo-detector 13 is increasing or decreasing. Alternatively signals may be compared with those from a second similar unit positioned elsewhere along the piston 8, to give its direction of motion.
Claims (6)
1. Apparatus for measuring displacement between first and second members comprising first and second gratings; means for supporting the first grating for movement with the first member; means for supporting the second grating for movement with the second member, the arrangement being such that the first and second gratings are disposed relative one to the other such that one or more moire fringes are produced, a relative displacement between the first and second members causing a corresponding movement of the one or more moire fringes; a source adapted to illuminate the first and second gratings with electro-magnetic radiation; a detector adapted to monitor radiation from the source incident thereon; and an electronic processing unit adapted to receive signals from the detector and to calculate-therefrom the relative displacement between the first and second members; characterised in that the markings on at least one of the first and second gratings are
reflective and the detector is positioned on the same side of the first and second gratings as the source.
2. Apparatus according to Claim 1 characterised in that the markings on both of the first and second gratings are reflective.
3. Apparatus according to Claim 1 or Claim
2 characterised in that the source is a light
source and the detector is a photo-detector.
4. Apparatus according to any of Claims 1 to 3 characterised in that there is provided an optical fibre between the source and the first and second gratings, adapted to transmit electro-magnetic radiation to illuminate the grat
ings.
5. Apparatus according to any of Claims 1 to 4 characterised in that there is provided an
optical fibre between the first and second
gratings and the detector, adapted to transmit
electro-magnetic radiation thereto.
6. A method of measuring displacement between first and second members characterised
by the steps of providing first and second
gratings; supporting the first grating for move
ment with the first member; supporting the
second grating for movement with the second
member, the arrangement being such that the first and second gratings are disposed relative one to the other such that one or more moire fringes are produced, a relative displacement between the first and second members causing a corresponding movement of the one or more moire fringes; illuminating the first and second gratings with electro-magnetic radiation; detecting the radiation reflected from at least one of the first and second gratings; and calculating, from the amount of radiation reflected from the at least one of the first and second gratings, the relative displacement of the first and second members.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08619779A GB2194042A (en) | 1986-08-14 | 1986-08-14 | Displacement measurement |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08619779A GB2194042A (en) | 1986-08-14 | 1986-08-14 | Displacement measurement |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8619779D0 GB8619779D0 (en) | 1986-09-24 |
| GB2194042A true GB2194042A (en) | 1988-02-24 |
Family
ID=10602699
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08619779A Withdrawn GB2194042A (en) | 1986-08-14 | 1986-08-14 | Displacement measurement |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2194042A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111207908B (en) * | 2018-11-21 | 2021-09-21 | 上海电缆研究所有限公司 | Calibration grating for calibrating optical fiber test instrument and calibration method |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB914438A (en) * | 1960-10-01 | 1963-01-02 | Ferranti Ltd | Improvements relating to measuring apparatus |
| GB1370307A (en) * | 1970-10-23 | 1974-10-16 | Bendix Corp | Apparatus for and method of determinging displacements using moire fringes |
| GB1456366A (en) * | 1972-12-14 | 1976-11-24 | Hawker Siddeley Dynamics Ltd | Linear displacement devices |
| GB2020012A (en) * | 1978-04-13 | 1979-11-07 | Hale K F | Strain and displacement measuring gauges |
| GB1571245A (en) * | 1976-10-15 | 1980-07-09 | Bergkvist L | Electronic measuring tape |
| EP0132978A2 (en) * | 1983-07-30 | 1985-02-13 | Dr. Johannes Heidenhain GmbH | Displacement measuring apparatus and method |
-
1986
- 1986-08-14 GB GB08619779A patent/GB2194042A/en not_active Withdrawn
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB914438A (en) * | 1960-10-01 | 1963-01-02 | Ferranti Ltd | Improvements relating to measuring apparatus |
| GB1370307A (en) * | 1970-10-23 | 1974-10-16 | Bendix Corp | Apparatus for and method of determinging displacements using moire fringes |
| GB1456366A (en) * | 1972-12-14 | 1976-11-24 | Hawker Siddeley Dynamics Ltd | Linear displacement devices |
| GB1571245A (en) * | 1976-10-15 | 1980-07-09 | Bergkvist L | Electronic measuring tape |
| GB2020012A (en) * | 1978-04-13 | 1979-11-07 | Hale K F | Strain and displacement measuring gauges |
| EP0132978A2 (en) * | 1983-07-30 | 1985-02-13 | Dr. Johannes Heidenhain GmbH | Displacement measuring apparatus and method |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8619779D0 (en) | 1986-09-24 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4570065A (en) | Robotic compensation systems | |
| EP0330429B1 (en) | Method and apparatus for monitoring the surface profile of a workpiece | |
| CN1305582A (en) | Method and arrangement for determining geometry of objects using coordinate measuring device | |
| EP0135000A3 (en) | Device for measuring length according to the double-gap laser interferometer principle | |
| JPH0628612U (en) | Multi-axis measuring instrument | |
| EP0341882A2 (en) | Optical sensors | |
| EP0629835B1 (en) | Strain measuring instrument | |
| US4836031A (en) | Method and apparatus for measuring deformations of test samples in testing machines | |
| EP0726446A2 (en) | Improvements in or relating to surface curvature measurement | |
| EP0183663A2 (en) | Sensor for measurement of the deflection and/or torsion of an oblong machine element | |
| EP0266118A1 (en) | Displacement detection | |
| GB2194042A (en) | Displacement measurement | |
| JP2002510794A (en) | Position measuring device | |
| CN114719754B (en) | High-speed rail simple beam expansion joint micrometer displacement low-coherence optical monitoring system and method | |
| US3779647A (en) | Interferometric device for indicating displacement along one dimension during motion along another dimension | |
| US5164602A (en) | Machine guidance system utilizing fiber optics | |
| US3883249A (en) | Z-factor and other diffractographic displacement and profile sensors | |
| EP0567980B1 (en) | Procedure for measuring the curved profile of edges | |
| KR0112496Y1 (en) | Measuring apparatus for surface roughness of sheet | |
| EP0272297A1 (en) | Opto-electronic scale-reading apparatus. | |
| SU954813A1 (en) | Device for measuring part deformation | |
| SE8903767D0 (en) | CONTACT-FREE MEASUREMENT PROB | |
| SU1523907A1 (en) | Spherometer | |
| Miao et al. | Active trigonometry and its application to thickness measurement on reflective surface | |
| JPH0411807B2 (en) |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |