GB2055193A - Measuring optical interference - Google Patents
Measuring optical interference Download PDFInfo
- Publication number
- GB2055193A GB2055193A GB7926976A GB7926976A GB2055193A GB 2055193 A GB2055193 A GB 2055193A GB 7926976 A GB7926976 A GB 7926976A GB 7926976 A GB7926976 A GB 7926976A GB 2055193 A GB2055193 A GB 2055193A
- Authority
- GB
- United Kingdom
- Prior art keywords
- waveguide
- modes
- measuring
- photodetectors
- photodetector
- 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- Withdrawn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
- 230000003287 optical effect Effects 0.000 title claims abstract description 20
- 230000008878 coupling Effects 0.000 claims abstract description 8
- 238000010168 coupling process Methods 0.000 claims abstract description 8
- 238000005859 coupling reaction Methods 0.000 claims abstract description 8
- 238000000034 method Methods 0.000 claims abstract description 8
- 238000006073 displacement reaction Methods 0.000 claims abstract description 3
- 230000010363 phase shift Effects 0.000 claims abstract description 3
- 238000005259 measurement Methods 0.000 abstract description 4
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000035945 sensitivity Effects 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
- G01D5/353—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 influencing the transmission properties of an optical fibre
- G01D5/35303—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 influencing the transmission properties of an optical fibre using a reference fibre, e.g. interferometric devices
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Length Measuring Devices By Optical Means (AREA)
Abstract
A method of measuring optical interference for use in incremental lengths and angular measurement, using an integrated optical arrangement, comprises the steps of coupling two modes 5, 6 (first and second laser beams) to a waveguide 2. The modes interfere within the waveguide 2, and the relative phase positions of both modes varied through a measuring operation is measured. An integrated optical arrangement for carrying out the method is characterised in that a multi-mode waveguide 2 is arranged between a carrier 1 and a cover layer 3. The effective refractive indices of the waveguide 2 differ with respect to two coupled modes comprising laser beams 5 and 6 such that an interference period results. The individual maxima of the modes are detected by a sequence of photodetectors 7 to 16 disposed upon the cover layer 3 and which are energetically connected to the waveguide 2 via coupling gratings (not shown). A first photodetector 7 of the sequence serves for measuring the resulting phase shift in lambda /2 steps. A second photodetector (not shown), staggered relative to the first photodetector 7 at half an interference period, is provided to detect the direction of phase variation. The remaining photodetectors of the. sequence act as an optical vernier. The detectors detect the displacements in lambda /2 diversion steps in dependence on the number of photodetectors. <IMAGE>
Description
SPECIFICATION -Method of and arrangement for measuring optical interference
This invention relates to a method of and an arrangement for measuring optical interference, particularly for use in incremental lengths and angular measurements.
In a known integrated optical arrangement for interference measurements a light beam is decomposed in a waveguide layer in two portions through a first partially transmissive element. The two portions are directed by means of reflecting elements to a second partially transmissive element which combines the two beam portions, thus enabling interferences.
The production costs of such an arrangement which satisfies the required reflective and transmissive properties are considerable.
Furthermore, the position of the reflecting elements relative to the partial transmissive elements is of importance to the function of the measuring arrangement, which involves considerable technological problems.
It is an object of the invention to obviate the foregoing disadvantages. It is a further object of the invention to provide a method of and an integrated optical arrangement for interference measurements which have the advantage of a compact design, low production costs, low sensitivity towards vibration and temperature, and low energy requirements.
Accordingly, the present invention consists in a method of measuring optical interference by means of an integrated optical arrangement, comprising the steps of coupling two modes to a waveguide, which modes interfere within said waveguide, and measuring the relative phase positions of both modes varied through a measuring operation.
The present invention also consists in an arrangement for measuring optical interference, characterised in that a multi-mode waveguide is arranged between a carrier and a cover layer, the effective refractive indices of which waveguide differ in such a way with respect to two coupled modes that an interference period results, the individual maxima of said modes being detected by a sequence of photocells disposed upon the cover layer and energetically connected to the waveguide, and in that a first photocell of said sequence of photodetectors serves for measuring the resulting phase shifts in A/2 steps, a second photodetector, staggered relative to the first by half an interference period, is provided to detect the direction of the phase change, and the remaining photocells of said sequence detect the displacements in A/2 division units in dependence
on the number of photocells.
In order that the invention may be more readily
understood, reference is made to the accompanying drawing which illustrates diagrammatically and by way of example one embodiment of an arrangement in accordance with the invention. In the Figure a two-modes waveguide 2 covered by a dielectric layer 3 of lower refractive index than that of the waveguide 2 is arranged upon a carrier 1. A coupling grate 4 is arranged at one end of the waveguide 2. A first laser beam 5 comprising the TEo mode impinges upon the coupling grate 4 under the synchronizing angle with respect to this mode so that the TEo mode is excited in the waveguide 2. A second laser beam 6 comprising the TEt mode is directed to the coupling grate 4 under the respective synchronizing angle.
Thus the TE1 mode is simultaneously excited in the waveguide 2. The properties of the waveguide 2 have to be such that the effective refractive indices of the TEo mode and of the TE1 mode do only differ insignificantly.
The following values are given as an example
Akz=00157
where neff is the effective refractive index in the propagation direction of the laser energy,
kz the wave number of the laser light, and
Akz the difference of the wave numbers in z-direction.
When, as in the above example, the kz values differ by 0.0157 an interference pattern results in the waveguide which has a period of 400 irlm in the z-direction
Minute coupling gratings (not shown) having a
width of about 20 ,t4m are arranged on the surface
of the waveguide spaced apart by 420 ,um. Said
grating are of low decoupling effectivity.
The energy decoupled through these gratings
impinges upon photodiodes 9 to 16, which are, for example, attached by adhesive means to the dielectric layer 3. In the example the detected intensity continuously decreases in z-direction due to the intensity maxima. When the laser beam 5 and the laser beam 6 are produced through the positive first deflection order and through the negative first deflection order of an illuminated grid scale then the interference pattern moves in z-direction by 2A in the waveguide 2 provided that the measuring grating is displaced about one grate period.
By means of a first photodetector 7 an incremental counting is carried out in units of half periods of the measuring grate. The photodetectors 7 to 16 are in their unity an optical vernier so that one twentieth of the measuring grate period can be given as a measuring unit.
A backward or forward movement of the measuring grating can be detected when a second photodetector (not shown in the drawing) is provided in addition to the first photodetector 7, however, staggered to the first photodetector by
A
4
The sinusoidal line shown in the waveguide 2 is a schematical representation of the intensity distribution.
Claims (4)
1. Method of measuring optical interference by means of an integrated optical arrangement, comprising the steps of coupling two modes to a waveguide, which modes interfere within said waveguide, and measuring the relative phase positions of both modes varied through a measuring operation.
2. An integrated optical arrangement for measuring optical interference characterised in that a multi-mode waveguide is arranged between a carrier and a cover layer, the effective refractive indices of which waveguide differ with respect to two coupled modes such that an interference period results, the individual maxima of said modes being detected by a sequence of photodetectors disposed upon the cover layer and energetically connected to the waveguide, and in that a first photodetector of said sequence of photodetectors serves for measuring the resulting phase shift in ; ;t/2 steps, a second photodetector, staggered relative to the first photodetector at half an interference period, is provided to detect the direction of phase variation, and the remaining photodetectors of said sequence detect the displacement in A/2 division steps in dependence on the number of photodetectors.
3. Method of measuring optical interference, substantially as herein described with reference to the accompanying drawing.
4. An integrated optical arrangement for measuring optical interference, substantially as herein described with reference to and as shown in the accompanying drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7926976A GB2055193A (en) | 1979-08-02 | 1979-08-02 | Measuring optical interference |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7926976A GB2055193A (en) | 1979-08-02 | 1979-08-02 | Measuring optical interference |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2055193A true GB2055193A (en) | 1981-02-25 |
Family
ID=10506952
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7926976A Withdrawn GB2055193A (en) | 1979-08-02 | 1979-08-02 | Measuring optical interference |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2055193A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2155623A (en) * | 1983-09-05 | 1985-09-25 | Standard Telephones Cables Ltd | Fibre optic sensor |
| US10011932B2 (en) | 2013-05-29 | 2018-07-03 | Card-Monroe Corp. | Tufting machine drive system |
| CN113358037A (en) * | 2021-08-10 | 2021-09-07 | 中国计量科学研究院 | Laser displacement measuring device and method |
-
1979
- 1979-08-02 GB GB7926976A patent/GB2055193A/en not_active Withdrawn
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2155623A (en) * | 1983-09-05 | 1985-09-25 | Standard Telephones Cables Ltd | Fibre optic sensor |
| US10011932B2 (en) | 2013-05-29 | 2018-07-03 | Card-Monroe Corp. | Tufting machine drive system |
| US10190246B2 (en) | 2013-05-29 | 2019-01-29 | Card-Monroe Corp. | Tufting machine drive system |
| CN113358037A (en) * | 2021-08-10 | 2021-09-07 | 中国计量科学研究院 | Laser displacement measuring device and method |
| CN113358037B (en) * | 2021-08-10 | 2021-11-09 | 中国计量科学研究院 | Laser displacement measuring device and method |
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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) |