GB2174491A - A displacement measuring system - Google Patents
A displacement measuring system Download PDFInfo
- Publication number
- GB2174491A GB2174491A GB08510415A GB8510415A GB2174491A GB 2174491 A GB2174491 A GB 2174491A GB 08510415 A GB08510415 A GB 08510415A GB 8510415 A GB8510415 A GB 8510415A GB 2174491 A GB2174491 A GB 2174491A
- Authority
- GB
- United Kingdom
- Prior art keywords
- light
- steering unit
- beam steering
- optical
- detector
- 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- Withdrawn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 25
- 230000003287 optical effect Effects 0.000 claims abstract description 56
- 239000004973 liquid crystal related substance Substances 0.000 claims description 5
- 238000010586 diagram Methods 0.000 description 5
- 230000005540 biological transmission Effects 0.000 description 2
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 238000001514 detection 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
- G01D5/266—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 by interferometric means
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Length Measuring Devices By Optical Means (AREA)
Abstract
Displacement of an elongate surface (6) is monitored by a plurality of beam steering units (2,3,4) mounted on the surface (6), each beam steering unit (2,3,4) being interrogated by a beam of light (8) delivered from an optical source (1). Each beam steering unit (2,3,4) includes an optical arrangement (7,9,10) which re-directs the beam of light from its initial path of a path (11) incorporating a light detector (15). The optical arrangement includes a pair of beamsplitters (7,9) and an optical switch (10). The individual switches (10) of the various beamsplitting units (2,3,4) are sequentially opened to enable interrogation of only one beam steering unit (2,3,4) at a time. <IMAGE>
Description
SPECIFICATION
A displacement measuring system
The present invention relates to a displacement measuring system and in particular to a system for measuring lateral and/or angular displacement of a surface.
According to the present invention there is provided a system for measuring the displacement of a surface, comprising an optical source which provides a beam of light, a beam steering unit which is intended in use to be secured to a surface to be monitored and which comprises at least one optical element which redirects the beam of light from said optical source, and a position sensitive detector upon which the redirected beam of light is incident for detecting any change in the position of the beam thereon.
Preferably, the optical source comprises a He-Ne laser the output of which passes through a collimator.
Preferably, the detector comprises two position sensitive photodiodes each located at different distances from the beam steering unit. The position sensitive photodiodes may be disposed at an angle with respect to each other and a beam splitter may be provided therebetween to split the beam of light output from said beam steering unit therebetween. Alternatively, the position sensitive photodiodes may be axially aligned on the beam output from said beam steering unit, the forward photodiode being partially transparent to allow transmission of the beam of light to the rearward photodiode.
Preferably, the detector comprises a demagnifier positioned in the path of the beam of light from the beam steering unit.
Preferably, the displacement measuring system comprises a plurality of beam steering units which are each secured to a respective portion of an elongate surface and are axially aligned between the optical source and the detector, and means for individually interrogating each beam steering unit.
Preferably, said interrogation means comprises an optical switch located in the path of the redirected beam of light, and means for turning the optical switch on or off to allow or to prevent the passage of light to said detector.
Preferably, the optical switch comprises a liquid crystal switch and a source of electrical power, and the means for turning the switch on or off comprises an individually addressable switching device which connects or disconnects the source of power to the liquid crystal switch.
Preferably, each individually addressable switching device is addressed by providing a predetermined number of pulses of light from the optical source thereto.
Preferably, the source of electrical power is provided by a photocell located in the path of the redirected beam of light immediately before the liquid crystal switch.
Preferably, the surface of each beam steering unit upon which light from said optical source is incident comprises a beam splitter which directs one beam of light towards the optical elements comprising said beam steering unit and the other beam of light towards the next beam steering unit.
An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings: in which
Figure 1 shows a schematic diagram of a displacement measuring system according to the present invention;
Figure 2 shows a diagrammatic view of a beam steering unit for use in the system of Figure 1;
Figure 3(a) and (b) show schematic diagrams of a multi-beam steering unit displacement measuring system in interrogation mode and measuring mode respectively.
Figures 4(at, (b) and (c) show schematic diagrams of the detection system of the displacement measuring system of Figure 1.
Referring to Figure 1 of the accompanying drawings there is shown a schematic diagram of a displacement measuring system according to the present invention, comprising an optical source 1, a plurality of identical beam steering units 2, 3 and 4, and a light sensitive position detector 5. The optical source 1 is required to produce a fairly collimated beam over a distance of several tens of meters, and to this end it comprises a He-Ne laser, the output of which is directed through a collimator. The beam steering units 2, 3 and 4 are aligned between the optical source 1 and the detector 5 and are secured to a surface 6 which it is intended to monitor the displacement of. Each of the beam steering units 2, 3 and 4 comprises a beam splitter 7 which lies in the path of a beam 8 output from the optical source 1.Each beam splitter 7 splits off a part of the beam 8 and directs it via a series of optical elements 9, discussed in greater detail with reference to Figure 2, and an optical switch 10 towards the detector 5. Only one of the optical switches 10 is turned on at any one time and hence only one of the beam steering units 2, 3 and 4 is able to transmit light to the detector 5 at any one time. The direction and position of the beam 11 to the detector 5 are determined by the orientation of the optical elements 9 comprising the beam steering unit. Thus, any change in the orientation of these elements 9 gives rise to a corresponding change in the direction and position of the beam 11 and hence of the point at which it is incident on the detector 5. The detector 5 is capable of detecting any change in the position at which the beam 11 is incident on the detector 5.The detector 5 is capable of detecting any change in the position at which the beam 11 is incident thereon and of providing a monitorable output proportional thereto.
Any change in position of a particular beam steering unit can thus be monitored by switching the optical switch 10 associated therewith on and determining the extent to which the beam 11 incident on the detector 5 has changed its position from a pre-established reference. By determining the distance of the beam steering unit from the de vector 5 it is possible to calculate the exact distance by which the point at which the beam steering unit is attached has moved. This will be elaborated upon further with reference to Figure 4.
Referring to Figure 2 there is shown a diagrammatic view of a beam steering unit comprising a beam splitter 7 which in use is positioned in the path of the beam 8 output from the optical source.
That portion 12 of the beam 8 which does not pass on to the next beam steering unit (not shown) is turned through 90 degrees in the horizontal plane and is incident upon an optical switch 10. The switch 10 is turned on by the application of a small electrical voltage thereto and when turned on it allows the passage of light therethrough. This voltage may be supplied by a photocell located at an appropriate port of the beam steering unit or by a battery pack. The advantage of using a photocell is that it can be charged by the optical source making the displacement measuring system independent of external sources of power. After the switch 10 the beam 12 is turned through a further 90 degrees in the vertical plane by a right angled prism 14.
Thereafter, the beam 12 is incident on a beam splitter 15 which turns it through a further 90 degrees in the horizontal plane and directs it towards the detector (not shown). The beam 11 output from the beam splitter 15 runs substantially parallel to the beam 8 output from the optical source and as such passes through the corresponding beam splitter 15 of each of the beam steering units aligned between it and the detector.
Referring now to Figure 3(a) there is shown an embodiment of the displacement measuring system according to the present invention comprising four beam steering units 16 which are each individually addressable to facilitate interrogation thereof. In order to interrogate a particular beam steering unit 16 the beam of light from the optical source (not shown) is directed via an optical modulator 17 which modulates the beam of light to carry a series of coded pulses which represent the address of the beam steering unit 16 which it is intended to interrogate. The modulated beam of light from the modulator 17 is incident upon a light activated switch 18 associated with each of the beam steering units 16. The light activated switches 18 each convert the optical pulses into electrical pulses, which are then applied to an associated logic circuit 19.The logic circuits 19 are each preprogrammed with a specific address and when that address is detected by the logic circuit 19 for which it is intended a voltage is output from the logic circuit 19 to an optical switch 20 associated therewith. This voltage causes the optical switch 20 to turn on and allows the beam steering unit 16 associated therewith to be interrogated.
Once the optical switch 20 is turned on the beam of light from the optical source (not shown) is free to pass through the associated beam steering unit 16 to the detector 21, as shown in Figure 3(b).
However, because the optical switches 20-associated with the other beam steering units 16 remain off transmission of the beam of light therethrough is prevented.
It will be apparent that the optical interrogation system requires electrical power to operate the optical switches 20. This electrical power can be provided from a dry cell battery pack, but ideally is provided by a solar cell provided in the beam steering unit 16. The position of the solar cell is not crucial, but it must be positioned before the optical switch 20 so that it is effectively "on' at all times that optical energy is entering the beam steering unit 16.
Referring now to Figures 4(a), (b) and (c) there are shown schematic diagrams of a detector for use in the displacement measuring system of the present invention, each illustrating a different form of displacement of the surface to be monitored. In the drawings the initial position of the beam of light is shown by the dotted lines, whilst the position of the deflected beam of light is shown by the full lines. The purpose of the detector is to determine the magnitude of any displacement, and whether the displacement is translational, angular or a combination of both. It will be appreciated that the distance of each beam steering unit from the detector is known.
The detector comprises a beam splitter 22 aligned at 45 degrees to the path of the beam of light output from the beam steering unit currently being interrogated and two position sensitive photodiodes 23 and 24 which are each located in the path of a respective one of the two beams output from the beam splitter 22 and hence from the beam steering unit. The position sensitive photodiodes 23 and 24 provide an output which is a function of the position of a beam of light on the surface thereof. As such they provide a change in output if the position of the beam of light thereon changes. The position sensitive photodiodes 23 and 24 are located at unequal distances from the beam splitter 22. These distances are known and fixed. In addition, the detector comprises a beam reducer 25.The beam reducer 25 is comprised of a demagnifying combination of lenses:
In Figure 4(a) there is shown a case of lateral displacement of the surface to be monitored. In th s instance the distances by which the beams of light incident on the position sensitive photodiode 23 and 24 are displaced are equal. This being the case the distances by which the incident beams are displaced will be equal to the distance by which the surface being monitored is displaced.
In Figure 4(b) there is shown a case of angular displacement of the surface to be monitored. In this instance the distances by which the beams of light incident on the position sensitive photodiodes are displaced are unequal. By using some simple trigonometry the angle of displacement can be calculated.
In Figure 4(c) there is shown a case of both translational and angular displacement. In this instance the distances by which the beams of light incident on the position sensitive photodiodes are displaced are again unequal. By extrapolating back to the beam steering unit and using some simple trigonometry the translational and angular displacement can be simply calculated.
Whilst the detector has been described as comprising a beam splitter which splits the beam from the beam steering unit under interrogation between the two position sensitive photodiodes it is possible to dispense with the beam splitter. In this instance the position sensitive photodiodes are aligned one behind the other, and the forward one of the two is made partially transparent. In this way the beam of light is still incident on both position sensitive photodiodes, which are both unequal distances from the beam steering unit.
Whilst the beam steering unit has been described as comprising a plurality of optical elements it will be appreciated that it may only comprise one optical element, provided that the optical element is capable of reflecting the incident beam of light.
In order to reduce the offset of the beams of light output from the optical source and from the beam steering unit under interrogation as they pass through the optical elements comprising the other beam steering units the thickness of these optical elements may be kept to the absolute minimum.
Claims (9)
1. A system for measuring the displacement of a surface comprising an optical source which provides a beam of light, a beam steering unit which is intended in use to be secured to a surface to be monitored and which comprises at least one optical element which redirects the beam of light from said optical source, and a position sensitive detector upon which the redirected beam of light is incident for detecting any change in the position of the beam thereon.
2. A system as claimed in claim 1, wherein the optical source comprises a He-Ne laser the output of which passes through a collimator.
3. A system as claimed in claim 1 or claim 2, wherein the detector comprises two position sensitive photodiodes each located at different distances from the beam steering unit.
4. A system as claimed in claim 3, wherein the detector comprises a demagnifier positioned in the path of the beam of light from the beam steering unit.
5. A system as claimed in claim 1, wherein the displacement measuring system comprises a plurality of beam steering units which are each secured to a respective portion of a elongate surface and are axially aligned between the optical source and the detector, and means for individually interrogating each beam steering unit.
6. A system as claimed in claim 5, wherein the interrogation means comprises an optical switch located in the path of the redirected beam of light, and means for turning the optical switch on or off to allow or to prevent the passage of light to said detector.
7. A claim as claimed in claim 6, wherein the optical switch comprises a liquid crystal switch and a source of electrical power, and the means for turning the switch on or off comprises an individually addressable switching device which connects or disconnects the source of power to the liquid crystal switch.
8. A system as claimed in any preceding claim, wherein the surface of each beam steering unit upon which light from said optical source is incident comprises a beam splitter which directs one beam of light towards the optical elements comprising said beam steering unit and the other beam of light towards the next beam steering unit.
9. A system as claimed in claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08510415A GB2174491A (en) | 1985-04-24 | 1985-04-24 | A displacement measuring system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08510415A GB2174491A (en) | 1985-04-24 | 1985-04-24 | A displacement measuring system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8510415D0 GB8510415D0 (en) | 1985-05-30 |
| GB2174491A true GB2174491A (en) | 1986-11-05 |
Family
ID=10578116
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08510415A Withdrawn GB2174491A (en) | 1985-04-24 | 1985-04-24 | A displacement measuring system |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2174491A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2652414A1 (en) * | 1989-09-26 | 1991-03-29 | Enea | IMPROVEMENT CONCERNING DEVICES FOR MEASURING OPTICAL ABSORPTION IN MATERIALS IN THIN LAYERS USING PHOTOTHERMAL DEVIATION SPECTROSCOPY. |
| US5268746A (en) * | 1989-09-26 | 1993-12-07 | Ente Per Le Nuove Tecnologie, L'energia E L'ambiente (Enea) | Devices for measuring the optical absorption in thin layer materials by using the photothermal deflection spectroscopy |
| WO2019105881A1 (en) | 2017-12-01 | 2019-06-06 | Bayer Pharma Aktiengesellschaft | Method for producing (3s)-3-(4-chlor-3-{[(2s,3r)-2-(4-chlorphenyl)-4,4,4-trifluor-3-methylbutanoyl]amino}phenyl)-3-cyclo-propylpropanoic acid and the crystalline form thereof for use as a pharmaceutical ingredient |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1338167A (en) * | 1971-02-10 | 1973-11-21 | Bauakademie Ddr | Optical guide beam system for locating reference points at various levels of an extensive structure |
| GB1354597A (en) * | 1970-08-13 | 1974-06-05 | Rheinmetall Gmbh | Process and device for determining the angle of jump of a projectile leaving a gun barriel |
| GB1386994A (en) * | 1971-07-07 | 1975-03-12 | Asea Ab | Apparatus for determingin the variation in distance between two points |
| EP0067531A2 (en) * | 1981-05-18 | 1982-12-22 | David R. Scott | System for assessing the effect of forces acting on a structure, and detectors and optical sensors for use in such systems |
| GB2133572A (en) * | 1983-01-12 | 1984-07-25 | South Yorkshire County Council | A laser optical projection system for balances and fine weighing instruments |
-
1985
- 1985-04-24 GB GB08510415A patent/GB2174491A/en not_active Withdrawn
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1354597A (en) * | 1970-08-13 | 1974-06-05 | Rheinmetall Gmbh | Process and device for determining the angle of jump of a projectile leaving a gun barriel |
| GB1338167A (en) * | 1971-02-10 | 1973-11-21 | Bauakademie Ddr | Optical guide beam system for locating reference points at various levels of an extensive structure |
| GB1386994A (en) * | 1971-07-07 | 1975-03-12 | Asea Ab | Apparatus for determingin the variation in distance between two points |
| EP0067531A2 (en) * | 1981-05-18 | 1982-12-22 | David R. Scott | System for assessing the effect of forces acting on a structure, and detectors and optical sensors for use in such systems |
| GB2133572A (en) * | 1983-01-12 | 1984-07-25 | South Yorkshire County Council | A laser optical projection system for balances and fine weighing instruments |
Non-Patent Citations (1)
| Title |
|---|
| WO A1 85/33222 * |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2652414A1 (en) * | 1989-09-26 | 1991-03-29 | Enea | IMPROVEMENT CONCERNING DEVICES FOR MEASURING OPTICAL ABSORPTION IN MATERIALS IN THIN LAYERS USING PHOTOTHERMAL DEVIATION SPECTROSCOPY. |
| GB2237382A (en) * | 1989-09-26 | 1991-05-01 | Enea | Photothermal deflection spectroscopy |
| US5268746A (en) * | 1989-09-26 | 1993-12-07 | Ente Per Le Nuove Tecnologie, L'energia E L'ambiente (Enea) | Devices for measuring the optical absorption in thin layer materials by using the photothermal deflection spectroscopy |
| GB2237382B (en) * | 1989-09-26 | 1994-01-12 | Enea | Optoelectronic devices |
| WO2019105881A1 (en) | 2017-12-01 | 2019-06-06 | Bayer Pharma Aktiengesellschaft | Method for producing (3s)-3-(4-chlor-3-{[(2s,3r)-2-(4-chlorphenyl)-4,4,4-trifluor-3-methylbutanoyl]amino}phenyl)-3-cyclo-propylpropanoic acid and the crystalline form thereof for use as a pharmaceutical ingredient |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8510415D0 (en) | 1985-05-30 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |