Full optical fibre Fizeau interference confocal measuring apparatus
Technical field
The present invention relates to nanometer accuracy measurement, particularly a kind of full optical fibre Fizeau interference confocal measuring apparatus.Be mainly used in the high-precision three-dimensional topography measurement of micro-nano device.
Background technology
Nanoscale science and technology is based on the scientific and technical system of the intersection that subject such as the physics, chemistry, biology, information, material of nanoscale constitutes.As the new branch of science of 21 century, the develop rapidly of nanosecond science and technology will bring the change of essence to material, device, system and process technology.Exploitation Highgrade integration, the intelligentized micro-nano device that can be mass-produced are one of nanometer technology targets that will realize.To detect be the key link of research and control micro-nano device performance to geometric sense accurately, for example, and the thickness of each layer etc. in surface topography, bench height, the sandwich construction.
The cofocus scanning microscopic system has unique axial response characteristic, has three-dimensional chromatography imaging function, has been widely used in biology, medical science, industry detection and metrology field.But the axial resolution of common confocal microscope still only rests on sub-micrometer scale, and the noise of light source directly influences measurement result with drift.Differential type confocal microscope system [Noninterferometric differential confocal microscopywith 2-nm depth resolution has been proposed for this reason, Optics Communications, 135,233-237,1997], make Measurement Resolution reach 2nm,, make measuring accuracy be subjected to the light intensity curve effect of nonlinear owing to still adopt the luminous intensity measurement method.Optical fiber Fizeau interference measuring technique is a kind of high-acruracy survey technology [Profile measurement of optically rough surfaces by fiber-opticinterferometry that is used for micrometric displacement and surface topography, OPTICS LETTERS, Vol.18, No.16,1361-1363,1993], still do not have axial chromatography function.
Summary of the invention
The objective of the invention is to overcome above-mentioned the deficiencies in the prior art, propose a kind ofly to utilize wavelength-division multiplex technique, adopt the Fizeau interference technology of the ingenious fusion of fiber grating filter and the method for confocal microscopy, provide the geometric senses such as thickness of a kind of surface topography that is used for micro-nano device, bench height, each layer of sandwich construction to carry out the full optical fibre Fizeau interference confocal measuring apparatus of high-acruracy survey.
Technical solution of the present invention is as follows:
A kind of full optical fibre Fizeau interference confocal measuring apparatus is characterised in that it constitutes:
The output terminal of the output terminal of first semiconductor laser and second semiconductor laser respectively with first port of optical fiber wave multiplexer, second port links to each other, the 3rd port of this optical fiber wave multiplexer links to each other with first port of optical fiber light-guiding element, the 3rd port of this optical fiber light-guiding element links to each other with probe optical fiber, close output end face is with first fiber grating on this probe optical fiber, the diffraction light of described first fiber grating is radiated on the testing sample that is on the 3-D scanning platform through GRIN Lens, second port of described optical fiber light-guiding element and first port of fiber optic splitter link to each other, the 3rd port of this fiber optic splitter links to each other with the 3rd fiber grating and second fiber grating respectively with the 4th port, the output terminal of second fiber grating links to each other with first photodetector, and the output terminal of the 3rd fiber grating links to each other with second photodetector.
The central wavelength lambda of described first semiconductor laser
0Central wavelength lambda with second semiconductor laser
1Be complementary with the centre wavelength and the reflection bandwidth of bandwidth and first fiber grating, second fiber grating, fiber grating.
Described optical fiber light-guiding element is fiber coupler or fiber optical circulator.
The output end face of described probe optical fiber has been cut an angle, to reduce the reflection of end face, this probe optical fiber is other low loss fiber of the light signal of general commercial single-mode fiber or multimode optical fiber or other suitable described first semiconductor laser of transmission and the emission of second semiconductor laser.
Described second fiber grating is that centre wavelength is λ
1Narrow band filter, the 3rd fiber grating is that centre wavelength is λ
0Narrow band filter.
The response wave length of described first photodetector and second photodetector is corresponding with the wave band of the light signal of described first semiconductor laser and the emission of second semiconductor laser, described first photodetector and second photodetector are photodiodes, or photoelectric cell.
The present invention has following characteristics and advantage:
1) light path adopts full fiberize structure, and measuring system has realized microminiaturization and flexibility, and is simple in structure, and light path is stable, and antijamming capability is strong, is convenient to being positioned by geodesic structure.And there is not the problem of physical pin obstruction and cleaning in confocal system.
2) interference of light and confocal microscopy are combined, the high precision characteristics and the exclusive characteristics of axial response on a large scale of confocal measuring technique of optical interferometry technology had both been made full use of, overcome the relative measurement of optical interferometry technology and the low shortcoming of resolution of confocal measuring technique again, can carry out the contactless measurement of high precision the geometric senses such as thickness of the surface topography of micro-nano device, bench height, sandwich construction.
3) introduce wavelength-division multiplex thought and Fiber Bragg Grating technology in the optical fiber telecommunications system, adopt the dual wavelength multiplexing method to realize that the common light path that reaches interference of light system and confocal system merges, because the reference arm and the signal arm of Fizeau interference itself are common light paths, thereby whole three light signals of system all are common light paths, have improved measuring stability.
Description of drawings
Fig. 1 is the light channel structure synoptic diagram of full optical fibre Fizeau interference confocal measuring apparatus of the present invention.
Embodiment
The invention will be further described below in conjunction with embodiment and accompanying drawing, but should not limit protection scope of the present invention with this.
Fig. 1 is the light channel structure synoptic diagram of full optical fibre Fizeau interference confocal measuring apparatus of the present invention, also be the embodiment of the invention the light channel structure synoptic diagram.As seen from the figure, constituting of full optical fibre Fizeau interference confocal measuring apparatus of the present invention:
The output terminal of first semiconductor laser 1 and second semiconductor laser 2 respectively with first port 31 of optical fiber wave multiplexer 3, second port 32 links to each other, the 3rd port 33 of this optical fiber wave multiplexer 3 and first port 41 of optical fiber light-guiding element 4 link to each other, the 3rd port 43 of this optical fiber light-guiding element 4 links to each other with probe optical fiber 5, close output end face is with first fiber grating 6 on this probe optical fiber 5, the diffraction light of described first fiber grating 6 is radiated on the testing sample 14 that is on the 3-D scanning platform 8 through GRIN Lens 7, second port 42 of described optical fiber light-guiding element 4 and first port 91 of fiber optic splitter 9 link to each other, the 3rd port 93 of this fiber optic splitter 9 links to each other with the 3rd fiber grating 11 and second fiber grating 10 respectively with the 4th port 94, the output of second fiber grating 10 links to each other with first photodetector 12, and the 3rd fiber grating 11 links to each other with second photodetector 13.
The central wavelength lambda of described first semiconductor laser 1
0Be complementary with the centre wavelength and the reflection bandwidth of the central wavelength lambda 1 of second semiconductor laser 2 and bandwidth and first fiber grating 6, second fiber grating 10, the 3rd fiber grating 11.
In the present embodiment: first semiconductor laser 1 and second semiconductor laser 2 adopt distributed feed-back formula (DFB) semiconductor laser of output wavelength at the 1300nm wave band, and both centre wavelength difference are in several nanometers, and output power is 1mW.It is the fiber coupler of 1:1 that optical fiber wave multiplexer 3 adopts splitting ratio.It is the fiber coupler of 1:1 that optical fiber light-guiding element 4 also adopts splitting ratio.Probe optical fiber 5 is the general commercial single-mode fiber.It is the fiber coupler of 1:1 that fiber optic splitter 9 adopts splitting ratio.First fiber grating 6, second fiber grating 10, the 3rd fiber grating 11 adopt the uniform period fiber grating that writes with Ultra-Violet Laser irradiation in general single mode fiber.First photodetector 12 and second photodetector 13 adopt the InGaAs photodetector.
The principle of work of full optical fibre Fizeau interference confocal measuring apparatus of the present invention is described below:
The present invention introduces the wavelength-division multiplex thought in the Fibre Optical Communication Technology, adopt the dual wavelength multiplexing method, the corresponding Fizeau interference of a wavelength system, the corresponding confocal microscope system of another wavelength, the common light path that realizes light Fizeau interference system and confocal system merges, to reach high precision characteristics and the exclusive characteristics of axial response on a large scale of confocal measurement that both make full use of optical interferometry, overcome the purpose of the low shortcoming of the resolution of the relative measurement of optical interferometry and confocal measurement again.As shown in Figure 1, first semiconductor laser 1 and second semiconductor laser 2 send optical maser wavelength and are respectively λ 0 and λ 1, the centre wavelength of first fiber grating 6 is that the centre wavelength of λ 0, the second fiber grating 10 is that the wavelength of λ 0, the three fiber grating 11 is center λ 1.Wavelength is that the laser of λ 0 arrives probe optical fiber 5 through optical fiber wave multiplexer 3 and optical fiber light-guiding element 4, through first fiber grating 6, part light is reflected by it, part light continues transmission and exports from fiber end face A, reflect by GRIN Lens 7 arrival samples 14 and by sample, this two bundles reflected light interferes at second photodetector 13, constitutes optical fiber Fizeau interference system.Wavelength is that the laser of λ 1 arrives probe optical fiber 5 through optical fiber wave multiplexer 3 and optical fiber light-guiding element 4, and pass through first fiber grating 6 and export from fiber end face A, focus on sample 14 through GRIN Lens 7, after the reflection again by the optical fiber head coupled back into optical fibers, receive by first photodetector 12, here the effect of fiber end face A is exactly confocal system " pin hole ", and wavelength is the light formation optical fiber confocal microscope system of λ 1 thus.When measuring, be responsible for determining reflecting surface by the optical fiber confocal microscope system, just axial chromatography function is responsible for measuring two-dimentional pattern by the Fizeau interference system.
First semiconductor laser 1 recited above and second semiconductor laser 2, be measuring system optical signal transmitting source, their centre wavelength and bandwidth need be complementary with the centre wavelength and the reflection bandwidth of first fiber grating 6, second fiber grating 10, the 3rd fiber grating 11.
Described optical fiber light-guiding element 4, its function are that the laser signal that comprises two wavelength from 3 outputs of optical fiber wave multiplexer is sent to probe optical fiber 5, and the light signal of reverse transfer is sent to fiber optic splitter 9 in the optical fiber 5 of will popping one's head in.It can be fiber coupler or fiber optical circulator, if fiber coupler, its splitting ratio is generally 1:1.
Said probe optical fiber 5, the position of its close output end face A is with first fiber grating 6, and output end face A has cut an angle, to reduce the reflection of end face.It can be other optical fiber of general commercial single-mode fiber or multimode optical fiber or other light signal of said semiconductor laser 1 and semiconductor laser 2 emissions above suitable low-loss transmission.
Described fiber grating 6, its function are for the Fizeau interference system provides one with reference to reflecting surface, do not reflect the light signal of confocal system simultaneously again.Its reflectivity size can be determined according to the reflection characteristic of sample 14, to obtain high interference contrast.
Fiber optic splitter 9 recited above, second fiber grating 10 and the 3rd fiber grating 11, constitute a dual wavelength demultiplexing module, effect is that the wavelength that makes the photodetector 12 of winning receive only confocal system is the light of λ 1, and the wavelength that second photodetector 13 receives only the Fizeau interference system is the light of λ 0.
The present invention adopts the narrow band fiber grating as wave filter, makes that the interval of two wavelength is very little, thereby can reduce the focus disperse problem that the wavelength difference is brought.
The function of described first photodetector 12 and second photodetector 13 is that light signal is converted to electric signal, its response wave length should said in the above first semiconductor laser 1 and the wave band of the light signal of second semiconductor laser, 2 emissions, they can be photodiodes, or photoelectric cell etc.
The experiment and the analysis showed that: the present invention has following characteristics and advantage:
1) light path adopts full fiberize structure, and measuring system has realized microminiaturization and flexibility, and is simple in structure, light path Stable, antijamming capability is strong, is convenient to being positioned by geodesic structure. And there is not the physical pin resistance in confocal system Plug and the problem of cleaning.
2) interference of light and confocal microscopy are combined, both taken full advantage of the high accuracy spy of optical interferometry technology Point and the exclusive characteristics of axial response on a large scale of confocal measuring technique have overcome again the relative survey of optical interferometry technology The low shortcoming of resolution ratio of amount and confocal measuring technique can be to surface topography, the shoulder height, many of micro-nano device The geometric senses such as thickness of layer structure are carried out the contactless measurement of high accuracy.
3) introduce wavelength-division multiplex thought and Fiber Bragg Grating technology in the optical fiber telecommunications system, adopt the dual wavelength multiplexing method real The common light path that now reaches interference of light system and confocal system merges, because reference arm and the signal arm of Fizeau interference itself Be common light path, thereby whole three optical signals of system all are common light paths, have improved the stability of measuring.