GB2191855A - Method and apparatus for detecting reflection sites - Google Patents
Method and apparatus for detecting reflection sites Download PDFInfo
- Publication number
- GB2191855A GB2191855A GB8611055A GB8611055A GB2191855A GB 2191855 A GB2191855 A GB 2191855A GB 8611055 A GB8611055 A GB 8611055A GB 8611055 A GB8611055 A GB 8611055A GB 2191855 A GB2191855 A GB 2191855A
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- GB
- United Kingdom
- Prior art keywords
- reflector
- light
- detecting
- source
- reflection sites
- 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.)
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- 238000000034 method Methods 0.000 title claims description 14
- 230000003287 optical effect Effects 0.000 claims description 9
- 239000000835 fiber Substances 0.000 claims description 3
- 238000002474 experimental method Methods 0.000 description 4
- 238000012545 processing Methods 0.000 description 3
- 238000013459 approach Methods 0.000 description 2
- 230000001427 coherent effect Effects 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000009533 lab test Methods 0.000 description 1
- HFGPZNIAWCZYJU-UHFFFAOYSA-N lead zirconate titanate Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ti+4].[Zr+4].[Pb+2] HFGPZNIAWCZYJU-UHFFFAOYSA-N 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
- G01N21/45—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N2021/1757—Time modulation of light being essential to the method of light modification, e.g. using single detector
- G01N2021/1759—Jittering, dithering, optical path modulation
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N2021/178—Methods for obtaining spatial resolution of the property being measured
- G01N2021/1782—In-depth resolution
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- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Length Measuring Devices By Optical Means (AREA)
Abstract
Reflection sites within a structure are detected using a source of light (1), a single reflector (4), means (6) for supporting a structure to be tested, means (2) for directing the light onto the reflector and towards the structure, means (7) for moving either the reflector or the supporting means, and means (5) for detecting the interference of light reflected off the reflector and off the structure. <IMAGE>
Description
SPECIFICATION
Method and apparatus for detecting reflection sites
The present invention relates to a method and apparatus for detecting reflection sites, in particular, but not exclusively, the internal reflections of an integrated optic chip.
In recent years, and particularly in the field of fibre optic communications, there has been a growing demand for integrated optic components with which to perform amplitude modulation, polarization control, phase modulation etc. The art of integrated optics is extending out of the research area and into industry.
With this move, there has been an increasing demand for a method and apparatus which could be used for testing integrated optic components.
There have been a number of attempts at creating a practical testing technique, but a satisfactory way of detecting reflection sites within for example, an integrated optic chip has not yet been found.
In order to explain the present invention, it may be helpful to discribe a known laboratory experiment using a Michelson interferometer.
In Fig. 1 of the accompanying drawings is shown an optical source 1, a beamsplitter 2, a fixed mirror 3, a movable mirror 4, and a detector 5.
Assume that light from an optical source is collimated and launched into the Michelson interferometer as shown. Part of the light will be turned by the beamsplitter 2, reflected off the fixed reflector 3, passed back through the beamsplitter, and into the detector 5. Another path for part of the input light will be to pass through the beamsplitter 2, reflect off the movable reflector 4, be turned by the beamsplitter, and then reach the detector 5. It is a well known and basic result that when the two light paths are of equal length (i.e. x = 0) that fringes will appear on the detector because the two optical beams will be able to add constructively or destructively depending on their relative phase.If the length mismatch of the two paths is sufficiently large then the two optical beams will not be able to interfere, i.e. they will not be coherent, and no fringes will appear on the detector.
It must, however, be exphasised that this experiment has had no practical application and has only been of theoretical interest to scientists. In particular, it must be emphasised that the experiment is not used to detect the position of any mirror. Further, it should be noted that some of those who have tried, but not succeeded, to develop a practical technique for detecting reflection sites have been quite aware of this experiment.
According to the invention there is provided a method of detecting reflection sites within a structure including the steps of directing light towards the structure and towards a reflecting surface, moving either the reflecting surface or the structure and detecting the interference of the light reflecting off the structure and the movable reflecting surface.
The invention also provides an apparatus for detecting reflection sites within a structure comprising a source of light,for a single reflector, means for supporting a structure to be tested, means for directing the light onto the reflector and towards the structure, means for moving either the reflector or the supporting means, and means for detecting the interference of light reflected off the reflector and off the structure.
The accuracy of the detecting technique depends upon the bandwidth of the source, i.e.
it depends on the frequency spectrum of the source. A broadband source will only have a small region where the fringe pattern appears, while a narrowband source will have a large region of fringe visibility. The size of this region of fringes visibilty determines the accuracy and, consequently, a broadband source will be much more sensitive than a narrowband source. For example, a single singlemode diode laser at 830 nm will typically have a measurement accuracy of several meters while a light emitting diode (an LED, a much broader source) will have an accuracy of 10's of microns, or less. A diode laser operating below threshold is a convenient source since its accuracy is similar to that of an LED while maintaining an output which is compatible with an integrated optic waveguide, i.e. it is spatially coherent.
An embodiment of the invention is described in more detail below, by example only and with reference to the accompanying drawings, wherein:
Fig. 1 is a diagram of a known experiment already discussed; and
Fig. 2 is a schematic diagram of an apparatus for detecting reflection sites within a structure according to the invention.
Fig. 2 shows a light source 1, a single reflector 4, means 6 for supporting a structure to be tested, means 2 for directing the light onto the reflector and towards the structure 3 on the support means 6, means 7 for moving the single reflector 4, and a detector 5 for detecting the interference of light reflected off the reflector 4 and off the reflection sites within the structure 3.
The light source 1 is preferably a diode laser driven below reflection. Experimental results with such a source indicate that a threshold site resolution of 10 microns can be achieved. The structure 2 is, in the illustrated example, an integrated optic chip having multiple reflection sites.
The directing means 2 comprises a beamsplitter which reflects the light in perpendicular directions or allows it to pass straight through, as described in relation to Fig. 1.
A lead zirconium titanate (PZT) piezoelectric modulator 10 may be placed behind the moveable mirror 4 so that the fringes seen at the detector 5 will be jitterred at multiples of the frequency f. This jitterring effect coupled with a notch filter and ac to dc conversion 8 should result in a high sensitivity device since all the processing will be moved away from the noise inherent in a dc measurement.
A motorized positioner can be used to scan the moveable mirror to look for fringes due to reflection sites and to output a voltage proportional to the location of the moveable mirror.
These two outputs, the mirror position voltage and the fringe height can then be fed into a plotter to give a hard copy of the reflection profile of the integrated optic chip (shown at 9 in Fig. 2). The height of the fringes will be an indication of the size of the reflection with current dc results indicating that a reflection due to an index difference of .001 can be observed (a very useful regime will be reached when index differences of .0001 can be seen and this shuld be easily reached with the ac system). Due to loss accumulation and dispersion effects in the chip, scaling of the output signal may be necessary.
As shown in Fig. 2 also, a collimating lens
11 and a focussing lens 12 can be positioned between the light source 1 and the beams splitter 2 and between the beamsplitter and the structure 3, respectively.
Obviously, other embodiments are also possible. Other sources could be used as well as other signal processing approaches. An interesting approach which could result in a device with a tuneable resolution would be to use a frequency modulateable optical source. If an optical source's frequency can be modulated at a rate much faster than the detection bandwidth of the signal processing area then the detection system will only see the envelope of the source's frequency modulation.
This envelope will become the source's effective bandwidth and will determine the resolution of the coherence ranging system. Consequently, by varying the amount of frequency modulation in the optical source the resolution can be tuned.
The apparatus and method of the invention can be used in other areas besides integrated optics. For example, the structure of thick film devices, small optical components, and some fibre optic components can be characterized using it.
Claims (14)
1. A method of detecting reflection sites within a structure including the steps of directing light towards the structure and towards a reflecting surface, moving either the reflecting surface or the structure and detecting the interference of the light reflecting off the structure and the movable reflecting surface.
2. A method according to claim 1, wherein the structure is an integrated optic chip, a thick film device, an optical component or a fibre optic component.
3. A method according to claim 1 or 2, wherein the reflecting surface is moved and jittered at the same time.
4. A method according to any preceding claim, wherein the light source's frequency is modulatable.
5. A method of detecting reflection sites within a structure, substantially as herein described.
6. An apparatus for detecting reflection sites within a structure comprising a source of light, a single reflector, means for supporting a structure to be tested, means for directing the light onto the reflector and towards the structure, means for moving either the reflector or the supporting means, and means for detecting the interference of light reflected off the reflector and off the structure.
7. An apparatus according to claim 6, wherein the light source is a broadband source.
8. An apparatus according to claim 7, wherein the light source is a diode laser driven below threshold.
9. An apparatus according to any of claims 6 to 8, further comprising a modulator connected to the reflector.
10. An apparatus according to claim 9, further comprising a notch filter and an AC to
DC converter.
11. An apparatus according to any of claims 6 to 10, wherein the reflector is connected to a motorized positioner.
12. An apparatus according to claim 11, wherein output of the positioner and the detecting means are fed into a plotter.
13. An apparatus according to any of claims 6 to 12, wherein the light source is frequency modulatable.
14. An apparatus for detecting reflection sites within a structure, substantially as herein described with reference to Figs. 2 of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8611055A GB2191855A (en) | 1986-05-07 | 1986-05-07 | Method and apparatus for detecting reflection sites |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8611055A GB2191855A (en) | 1986-05-07 | 1986-05-07 | Method and apparatus for detecting reflection sites |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8611055D0 GB8611055D0 (en) | 1986-06-11 |
| GB2191855A true GB2191855A (en) | 1987-12-23 |
Family
ID=10597418
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8611055A Withdrawn GB2191855A (en) | 1986-05-07 | 1986-05-07 | Method and apparatus for detecting reflection sites |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2191855A (en) |
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0458601A1 (en) * | 1990-05-22 | 1991-11-27 | Research Development Corporation Of Japan | Method of and apparatus for measuring spectral absorption in opaque specimens and method of and apparatus for measuring microscopic absorption distribution |
| WO1994000733A1 (en) * | 1992-06-22 | 1994-01-06 | British Technology Group Ltd. | Method of an apparatus for interferometrically inspecting a surface of an object |
| US5459570A (en) * | 1991-04-29 | 1995-10-17 | Massachusetts Institute Of Technology | Method and apparatus for performing optical measurements |
| US6111645A (en) * | 1991-04-29 | 2000-08-29 | Massachusetts Institute Of Technology | Grating based phase control optical delay line |
| US6134003A (en) * | 1991-04-29 | 2000-10-17 | Massachusetts Institute Of Technology | Method and apparatus for performing optical measurements using a fiber optic imaging guidewire, catheter or endoscope |
| US6445939B1 (en) | 1999-08-09 | 2002-09-03 | Lightlab Imaging, Llc | Ultra-small optical probes, imaging optics, and methods for using same |
| US6485413B1 (en) | 1991-04-29 | 2002-11-26 | The General Hospital Corporation | Methods and apparatus for forward-directed optical scanning instruments |
| US6501551B1 (en) | 1991-04-29 | 2002-12-31 | Massachusetts Institute Of Technology | Fiber optic imaging endoscope interferometer with at least one faraday rotator |
| US6564087B1 (en) | 1991-04-29 | 2003-05-13 | Massachusetts Institute Of Technology | Fiber optic needle probes for optical coherence tomography imaging |
| US7198623B2 (en) | 2003-01-10 | 2007-04-03 | Ultradent Products, Inc. | Fiber-coated dental infusor systems and methods of use |
| US7304735B2 (en) | 2004-04-02 | 2007-12-04 | Kla-Tencor Technologies | Broadband wavelength selective filter |
| US8046057B2 (en) | 2001-04-11 | 2011-10-25 | Clarke Dana S | Tissue structure identification in advance of instrument |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2084315A (en) * | 1980-09-22 | 1982-04-07 | Philips Nv | Interferometer |
-
1986
- 1986-05-07 GB GB8611055A patent/GB2191855A/en not_active Withdrawn
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2084315A (en) * | 1980-09-22 | 1982-04-07 | Philips Nv | Interferometer |
Non-Patent Citations (1)
| Title |
|---|
| WO A1 84/04810 * |
Cited By (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5345306A (en) * | 1990-05-22 | 1994-09-06 | Research Development Corporation Of Japan | Method and apparatus for measuring spectral absorption in an opaque specimen and method and apparatus for measuring the microscopic absorption distribution |
| EP0458601A1 (en) * | 1990-05-22 | 1991-11-27 | Research Development Corporation Of Japan | Method of and apparatus for measuring spectral absorption in opaque specimens and method of and apparatus for measuring microscopic absorption distribution |
| US6421164B2 (en) | 1991-04-29 | 2002-07-16 | Massachusetts Institute Of Technology | Interferometeric imaging with a grating based phase control optical delay line |
| US6564087B1 (en) | 1991-04-29 | 2003-05-13 | Massachusetts Institute Of Technology | Fiber optic needle probes for optical coherence tomography imaging |
| EP0581871B1 (en) * | 1991-04-29 | 1998-12-16 | Massachusetts Institute Of Technology | Apparatus for optical imaging and measurement |
| US6111645A (en) * | 1991-04-29 | 2000-08-29 | Massachusetts Institute Of Technology | Grating based phase control optical delay line |
| US6134003A (en) * | 1991-04-29 | 2000-10-17 | Massachusetts Institute Of Technology | Method and apparatus for performing optical measurements using a fiber optic imaging guidewire, catheter or endoscope |
| US6282011B1 (en) | 1991-04-29 | 2001-08-28 | Massachusetts Institute Of Technology | Grating based phase control optical delay line |
| US5459570A (en) * | 1991-04-29 | 1995-10-17 | Massachusetts Institute Of Technology | Method and apparatus for performing optical measurements |
| US6501551B1 (en) | 1991-04-29 | 2002-12-31 | Massachusetts Institute Of Technology | Fiber optic imaging endoscope interferometer with at least one faraday rotator |
| US6485413B1 (en) | 1991-04-29 | 2002-11-26 | The General Hospital Corporation | Methods and apparatus for forward-directed optical scanning instruments |
| WO1994000733A1 (en) * | 1992-06-22 | 1994-01-06 | British Technology Group Ltd. | Method of an apparatus for interferometrically inspecting a surface of an object |
| US6445939B1 (en) | 1999-08-09 | 2002-09-03 | Lightlab Imaging, Llc | Ultra-small optical probes, imaging optics, and methods for using same |
| US8046057B2 (en) | 2001-04-11 | 2011-10-25 | Clarke Dana S | Tissue structure identification in advance of instrument |
| US7198623B2 (en) | 2003-01-10 | 2007-04-03 | Ultradent Products, Inc. | Fiber-coated dental infusor systems and methods of use |
| US7304735B2 (en) | 2004-04-02 | 2007-12-04 | Kla-Tencor Technologies | Broadband wavelength selective filter |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8611055D0 (en) | 1986-06-11 |
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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) |