GB2192454A - System for measuring optical coatings - Google Patents
System for measuring optical coatings Download PDFInfo
- Publication number
- GB2192454A GB2192454A GB08714264A GB8714264A GB2192454A GB 2192454 A GB2192454 A GB 2192454A GB 08714264 A GB08714264 A GB 08714264A GB 8714264 A GB8714264 A GB 8714264A GB 2192454 A GB2192454 A GB 2192454A
- Authority
- GB
- United Kingdom
- Prior art keywords
- coatings
- reference beam
- measurement
- vacuum chamber
- beams
- 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- Withdrawn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
- 238000000576 coating method Methods 0.000 title claims abstract description 32
- 230000003287 optical effect Effects 0.000 title claims abstract description 23
- 238000005259 measurement Methods 0.000 claims abstract description 13
- 239000011248 coating agent Substances 0.000 claims abstract description 8
- 239000013307 optical fiber Substances 0.000 claims abstract description 3
- 238000000034 method Methods 0.000 claims description 5
- 238000012544 monitoring process Methods 0.000 claims description 5
- 238000012937 correction Methods 0.000 abstract description 2
- 238000012360 testing method Methods 0.000 abstract description 2
- 230000015572 biosynthetic process Effects 0.000 abstract 1
- 238000001914 filtration Methods 0.000 abstract 1
- 230000006798 recombination Effects 0.000 abstract 1
- 238000005215 recombination Methods 0.000 abstract 1
- 238000012545 processing Methods 0.000 description 5
- 239000000758 substrate Substances 0.000 description 3
- 230000008020 evaporation Effects 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 239000011521 glass Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000011896 sensitive detection 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
- G01N21/84—Systems specially adapted for particular applications
- G01N21/8422—Investigating thin films, e.g. matrix isolation method
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J1/00—Photometry, e.g. photographic exposure meter
- G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
- G01J2001/4242—Modulated light, e.g. for synchronizing source and detector circuit
-
- 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
- G01N2021/1748—Comparative step being essential in the method
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2201/00—Features of devices classified in G01N21/00
- G01N2201/08—Optical fibres; light guides
- G01N2201/082—Fibres for a reference path
Landscapes
- Physics & Mathematics (AREA)
- Mathematical Physics (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)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
Optical characteristics of optical coatings are monitored by measuring variations in a beam of light that has encountered said coatings. A beam of light is split into a measurement beam which encounters the coatings and a reference beam which does not encounter the coating, the reference beam and measurement beam being compared in a single detector. Preferably the measurement is performed during formation of the coating in a vacuum chamber. As shown, light from source 5 is filtered, chopped and separated at 8 into measuring beam 9 which is reflected from the coating on test object 15, and reference beam 21 which is passed along optical fibre 23. The beams are recombined and fed via spatial or rotating aperture filter 25 to single detector 19, the outputs of which are processed by phase sensitive detector 20 and sample and hold circuits 26. Alternatively the reference beam may pass through the vacuum chamber 18. In another embodiment, the two beams are differently modulated and, after recombination are passed through a scanning monochromator before electronic filtering to separate the beams. This embodiment enables noise correction across different wavelengths. <IMAGE>
Description
SPECIFICATION
System for measuring optical coatings
The present invention relates to a system for measuring optical coatings.
It is common practice to measuretheoptical characteristics of an optical coating whilst it is being deposited on an optical device. The measurement technique involves measuring the intensity modulation of a beam of light, such modulation arising from the optical properties ofthefilm that is gradually being deposited. The measurement may be made on either a reflected beam or a transmitted beam, and taken either from an optical device or substrate or else from individual films or groups of coatings deposited on separate pieces of material commonly known as witness plates.
This is a sensitive measurement and thus generally the incoming beam is modulated and the signal processing technique of phase sensitive detection is then used to improve the signal to noise ratio. Afurther known improvement to the technique is to detect changes in the light source intensity so that they may be removed from the measurement by the process known as comparison. This is achieved by splitting the beam from the light source to obtain a reference light beam and measuring the reference light beam using an additional detector. However, this introduces the problem of noise in the additional detector and also the duplication of components which increase the cost of the monitoring equipment.
According to the present invention there is provided a system for measuring optical coatings by monitoring variations in a beam of light that has encountered the said coatings, the beam having been split, one part of which being a measurement beam encounters the said coatings, a second part of which being a reference beam, wherein said measurement beam and said reference beam are measured using a single detector.
The reference beam may pass through an optical fibrewhilstthe measurement beam passes through a vacuum chamber of a coating unit. The reference beam may also travel within the vacuum chamber, beam splitting means being either within our without the chamber.
The beams may be intermittent and alteratively received by the single detector, or the signals may be received simultaneously with the beams being indentified by differences in their modulation.
The detector may either be a simple light power sensitive device combined with a single optical wavelength selective unit or it may consist of a single or multiplicity of light power sensitive devices combined with fixed or continuously scanning wavelength selective elements.
Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which Figure lisa schematic illustration of a hitherto employed system for measuring optical coatings;
Figure2 is a schematic illustration of one embodiment of a system for measuring optical coatings according to the invention; Figure 3 is a schematic illustration of a second embodiment of a system for measuring optical coatings; and
Figure 4is a schematic illustration of a third embodiment of a system for measuring optical coatings.
Referring to Figure 1 ofthe drawings, there is illustrated schematically a system hitherto employed for measuring optical coatings. The prior art system comprises an input system 1 and an output system 2 linked bya processing station 3wherein,under vacuum, coating is deposited and measured. In the input system 1, a beam of light4 is emitted from a light sourceS, passes through an optical filter6 and a rotating chopper7 before being splitbya beam splitter 8. One beam 9 ofthe split beam passes through a window 10 into a vacuum chamber 11 of the processing station 3. The other beam 12 terminates in a reference detector 13 which detects changes in light source intensity.In the vacuum chamber 11 an evaporation source 14supplies coatings to a substrate held in a test glass changer 15, the beam of light 9 being reflected from a first angled mirror 16 onto the substrate such that the beam 9 is reflected onto a second angled mirror 17 and subsequently leaves the vacuum chamber 11 through a window 18 to the output system 2. The beam 9 is then monitored by a detector 19 and compared with the signal from detector 13 both of which are passed through phase sensitive detectors 20,20'. In such a system, however, the different noise in the separate detectors 13 and 19 is not eliminated and results in inaccuracies.
Referring now to Figures 2, 3and4ofthe drawings, embodiments of the present invention are described wherein some parts of the systems are the same or closely similar to pa rts of the h itherto employed system of Figure 1, these parts being given, therefore, the same reference numerals. In the embodiment of Figure 2, one beam 9 of the split beam 4 travels through the processing station 3 as before, but the second or reference beam 21 is no longer passed to a detecting device but instead passes through a lens 22 to be carried byan optical fibre 23, by-passing the processing station 3,to another lens 24, which is positioned in the output system 2.Hence, both beams 9,21 nowenterthe output system 2 so they are incident on a rotating aperture or spatial filter 25, such that first beam 9 and then beam 21 are incident on the detectors 19,20, detector 19 converting into light into a signal, such as voltage, and the phase sensitive detector 20 improving the signal to noise ratio. The signalsthen enter a sample and hold device 26 which compares the signals generated by beams 9 and 21 such that the noise in the detecting devices of the system may be eliminated.
Referring now to the system of Figure 3 for measuring optical coatings according to the invention, in which the beam splitter 8 and recombining angled component 27 are within the vacuum chamber 11. The reference beam 21 therefore travels within the the vacuum chamber 11 and mechanical noise within the vacuum chamber
may be taken out, in addition to reducing noise in the detectors and light source. In afurtherembodiment (not shown) the reference beam travels a path closely similar to the other beam, the reference beam
being reflected off an angled optical component which is shielded from the evaporation source.
Referring now to the alternative system of Figure 4, the spatial filter 25 ofthe systems of Figures 2 and 3 is removed and the beams 9, 21 kept distinct in the output system 2 by modulation differences
introduced to the two beams 9, 21 by modulators, 28 and 29 respectively, placed in the beam paths. The
beams 9, 21 are recombined and compared, as
before, in the output system 2. The reference beam
21 and measuring beam 9 are recombined and
rendered as one monitoring signal 30 by a scanning monochromator31 , a subsequent electrnnicfilter32 being used to separate a measuring signal 33 and a
reference signal 34 from the one monitoring signal
30. A su bsequentreference circuit 35 compares the two signals 31, 32. The system of Figure 4 enables
correction for noise across different wavelengths
both in the light source 5and in the detector ofthe
scanning monochromator31.
Modifications and improvements may be
incorporated without departing from the scope ofthe invention.
Claims (6)
1 Asystemformeasuring opticalcoatingsby monitoring variations in a beam of lightthat has
encountered the said coatings, the beam having
been split, one partofwhich being a measurement
beam encounters the said coatings, a secondpart of which being a reference beam, wherein said
measurement beam and said reference beam are
measured using a single detector.
2. A system as claimed in Claim 1, wherein said
coating is located within a vacuum chamber of a
coating unit and said beam is split outside the
vacuum chamber, the reference beam passes to the
single detectorthrough an optical fibre.
3. A system as claimed in Claim 1, wherein the
reference beam also travels within the vacuum
chamber.
4. A method of measuring optical coatings by
measuring variations in a beam oflight that has
encountered said coatings comprising splitting the beamtoform one partwhich isa measurement
beam and encounters said coatings, and a second partwhich is a reference beam, and comparingsaid measurement beam and said reference beam in a
single detector.
5. A system for measuring optical coatings substantially as herein before described with
reference to Figures 2 to 4 of the accompanying
drawings.
6. A method for measuring optical coatings
substantially as hereinbefore described with
reference to Figures 2 to 4 of the accompanying
drawings.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB08714264A GB2192454A (en) | 1986-07-01 | 1987-06-18 | System for measuring optical coatings |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB868616058A GB8616058D0 (en) | 1986-07-01 | 1986-07-01 | Measuring optical coatings |
GB08714264A GB2192454A (en) | 1986-07-01 | 1987-06-18 | System for measuring optical coatings |
Publications (2)
Publication Number | Publication Date |
---|---|
GB8714264D0 GB8714264D0 (en) | 1987-07-22 |
GB2192454A true GB2192454A (en) | 1988-01-13 |
Family
ID=26290986
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB08714264A Withdrawn GB2192454A (en) | 1986-07-01 | 1987-06-18 | System for measuring optical coatings |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB2192454A (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2261728A (en) * | 1991-11-25 | 1993-05-26 | Helmut Reisser | Instrument for determining visual surface properties |
DE4413745A1 (en) * | 1994-04-20 | 1995-10-26 | Gramm Gmbh & Co Kg | Monitoring object surfaces |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1031380A (en) * | 1962-07-06 | 1966-06-02 | British Aircraft Corp Ltd | Optical density comparator system |
GB1254316A (en) * | 1967-12-12 | 1971-11-17 | Gaf Corp | An improved densitometer |
US4365896A (en) * | 1980-04-03 | 1982-12-28 | Bethlehem Steel Corp. | Optical attenuation monitor system and method |
US4511800A (en) * | 1983-03-28 | 1985-04-16 | Rca Corporation | Optical reflectance method for determining the surface roughness of materials in semiconductor processing |
EP0176827A2 (en) * | 1984-09-24 | 1986-04-09 | Kollmorgen Corporation | Method and apparatus for simultaneously determining gauge and orientation of polymer films |
EP0193742A2 (en) * | 1985-03-06 | 1986-09-10 | Hitachi, Ltd. | Wavelength scanning interferometry and interferometer employing laser diode |
-
1987
- 1987-06-18 GB GB08714264A patent/GB2192454A/en not_active Withdrawn
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1031380A (en) * | 1962-07-06 | 1966-06-02 | British Aircraft Corp Ltd | Optical density comparator system |
GB1254316A (en) * | 1967-12-12 | 1971-11-17 | Gaf Corp | An improved densitometer |
US4365896A (en) * | 1980-04-03 | 1982-12-28 | Bethlehem Steel Corp. | Optical attenuation monitor system and method |
US4511800A (en) * | 1983-03-28 | 1985-04-16 | Rca Corporation | Optical reflectance method for determining the surface roughness of materials in semiconductor processing |
EP0176827A2 (en) * | 1984-09-24 | 1986-04-09 | Kollmorgen Corporation | Method and apparatus for simultaneously determining gauge and orientation of polymer films |
EP0193742A2 (en) * | 1985-03-06 | 1986-09-10 | Hitachi, Ltd. | Wavelength scanning interferometry and interferometer employing laser diode |
Non-Patent Citations (1)
Title |
---|
WO A1 82/04310 * |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2261728A (en) * | 1991-11-25 | 1993-05-26 | Helmut Reisser | Instrument for determining visual surface properties |
US5392125A (en) * | 1991-11-25 | 1995-02-21 | Reisser; Helmut | Instrument for determining visual surface properties |
GB2261728B (en) * | 1991-11-25 | 1996-06-12 | Helmut Reisser | Instrument for determining visual surface properties |
DE4413745A1 (en) * | 1994-04-20 | 1995-10-26 | Gramm Gmbh & Co Kg | Monitoring object surfaces |
Also Published As
Publication number | Publication date |
---|---|
GB8714264D0 (en) | 1987-07-22 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP0500293B1 (en) | Particle detection method and apparatus | |
US3737237A (en) | Monitoring deposition of films | |
US4248536A (en) | Dual wavelength photometric device | |
US4063822A (en) | System for detecting a first light transmissive substance, such as for instance blood, in a second light transmissive, different substance | |
CA1068371A (en) | Circuit arrangements for controlling detector signals in surface inspection systems | |
GB2192454A (en) | System for measuring optical coatings | |
JPS5453562A (en) | Photoelectric detector | |
JP2973639B2 (en) | Equipment for measuring characteristics of sheet-like objects | |
EP0006648B1 (en) | Method and device for inspecting a moving sheet material for streaklike defects | |
EP0257973A3 (en) | Method and apparatus for compensating fiber optic lead and connector losses in a fiber optic sensor | |
CA2126387A1 (en) | High s/n ratio optical detection apparatus and method | |
JPH07270325A (en) | Defect inspector | |
JPH05142156A (en) | Foreign matter inspecting device | |
US5210417A (en) | Modulated high sensitivity infrared polarimeter | |
GB1347827A (en) | Multichromatic multibeam absorption photometer | |
JPS6361151A (en) | Apparatus for measuring contamination of insulator | |
JPH0310144A (en) | Corpuscle measuring apparatus | |
JPS60169743A (en) | Defect detecting method of surface of article | |
JPS5520454A (en) | Testing unit of light transmitting object dependent upon laser | |
JPS60129645A (en) | Gas concentration measuring apparatus | |
JPS6039974B2 (en) | optical inspection | |
JPS56128407A (en) | Light interference device | |
SU1233644A1 (en) | Double-beam gas analyzer | |
JPH06317535A (en) | Semiconductor inspection device and manufacture of semiconductor using same | |
JPH06180293A (en) | Foreign matter inspection apparatus |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |