CN115931857A - All-fiber three-dimensional tomography system - Google Patents
All-fiber three-dimensional tomography system Download PDFInfo
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- CN115931857A CN115931857A CN202211367785.7A CN202211367785A CN115931857A CN 115931857 A CN115931857 A CN 115931857A CN 202211367785 A CN202211367785 A CN 202211367785A CN 115931857 A CN115931857 A CN 115931857A
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- 238000012014 optical coherence tomography Methods 0.000 description 5
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Abstract
The invention discloses an all-fiber three-dimensional tomography system which comprises a frequency-sweeping laser, a first optical coupler, a first optical circulator, a first optical collimator, a first convex lens, an electric control attenuator, a second optical circulator, a second optical collimator, a second convex lens, a second optical coupler and a balance detector. The scanning laser included in the all-fiber three-dimensional tomography system can rapidly perform line or surface scanning on optical scattering media such as biological tissues and the like by utilizing a technology of acquiring optical signals to acquire images and adopting an all-fiber circuit architecture so as to obtain a high-resolution three-dimensional image.
Description
Technical Field
The invention relates to an optical inspection system, in particular to an all-fiber three-dimensional tomography system, which can utilize the technology of acquiring optical signals to acquire images and adopts an all-fiber circuit architecture, and can quickly perform line or surface scanning on optical scattering media such as biological tissues and the like to acquire high-resolution three-dimensional images.
Background
In many current industries, it is very important to inspect the surface of a minute structure or to obtain three-dimensional information. In the field of optical interference, interference occurs when the path lengths of a reference beam and a scanning beam coincide with each other. More specifically, the interference generating condition is a coherence length (coherence length) of the light source. Optical interference will occur when the path length difference is less than the source coherence length. The non-transparent specimen can be examined with a Michelson interferometer (Michelson interferometer) or a milo interferometer (Mirau interferometer). Transparent samples can also be measured by interferometry.
The michelson interferometer is one of the most commonly used configurations in optical interferometers. The light source is split into two paths by using a beam splitter (beam splitter). Both beams are reflected back to the beam splitter, which then combines and creates interference. The resulting interference pattern that is not directed back to the light source is typically directed to some type of photodetector (detector) or camera. For different applications of the interferometer, the two optical paths may have different lengths, or may contain optical elements or even the material being measured. The light source provides an initial beam of light to a beam splitter, which splits the initial beam into two beams. One of the two beams is directed onto the sample and the other beam is directed into a mirror to form a reference path. After the two beams are reflected back to the beam splitter, they will be combined and directed to a detector, thereby generating an interference pattern on the detector.
The mirao (Mira) interferometer is another commonly used optical interferometer configuration. The working principle of the milo interferometer is the same as that of the michelson interferometer. The difference between the two is the actual position of the reference arm (reference arm). The reference arm of the Miro interferometer is positioned in the microscope objective lens assembly and the light source generates an initial beam towards the lens L which refracts the beam to the beam splitter to generate two beams. One beam is directed into the sample and the other is reflected back to the half mirror on the lens L. Another optical system may be applied to combine the two beams to generate an interference pattern. For example, if the sample can be transparent, another optical system is configured below the sample. If the sample is opaque, an optical system with a mirror to collect the two beams should be configured above the sample.
Although both michelson and milo interferometers are widely used, the sample is probed using only one beam and interference is generated using the reference beam. Thus, in both cases, only half at most of the light from the light source can reach the sample surface. This greatly limits the ability to detect fine features on the sample surface. Furthermore, the reference path is critical to the system, which leads to the complexity of the michelson interferometer. Although the interference result can be obtained using the milo interferometer, in a non-transparent sample, since the interference must be performed using the back-scattered light, the intensity of light irradiated on the sample is further reduced, and information on the depth and thickness of the sample is easily lost.
Therefore, how to solve the above problems and deficiencies of the prior art is a topic to be researched and developed by the related art.
Disclosure of Invention
To solve the above problems, an object of the present invention is to provide an all-fiber three-dimensional tomography system.
The invention provides an all-fiber three-dimensional tomography system, which is particularly used for carrying out three-dimensional tomography on an object to be observed at a high speed. The swept-frequency laser is used for emitting laser rays with different wavelengths. The first optical coupler is connected to the frequency-swept laser through an optical fiber, and is used for receiving initial incident light emitted by the frequency-swept laser and splitting the initial incident light into first incident light and second incident light, wherein the quantity of the first incident light is 40-60 times that of the second incident light. The first optical scanning module is connected to the first optical coupler through an optical fiber to receive a first incident light ray, wherein the first incident light ray is emitted to an object to be observed to generate a first reflected light ray. The second optical scanning module is connected to the first optical coupler through an optical fiber to receive a second incident light, wherein the second incident light is emitted to a plane mirror to generate a second reflected light. The second optical coupler is connected to the first optical scanning module and the second optical scanning module through optical fibers to respectively combine the first reflected light and the second reflected light, wherein two output ports of the second optical coupler output the first target light and the second target light with the same quantity of light and perform optical interference effect with each other. The balance detector is connected to two output ports of the second optical coupler through optical fibers to receive the first target light and the second target light and output optical measurement signals after signal processing.
In an embodiment of the invention, the first optical scanning module includes a first optical circulator, a first optical collimator, a first convex lens and an electrically controlled attenuator. The first optical circulator is connected to the first optical coupler through an optical fiber to receive a first incident light ray, wherein the first incident light ray enters from a first port of the first optical circulator and exits from a second port. The first optical collimator is connected to the second port of the first optical circulator through an optical fiber, and the first optical collimator is used for converting divergent light of the first incident light into parallel light. The first convex lens is arranged in front of the first light collimator, wherein the first incident light ray can pass through the first light collimator and the first convex lens to irradiate towards the object to be observed so as to generate a first reflected light ray. The input port of the electrically controlled attenuator is connected to the third port of the first optical circulator through an optical fiber to receive the first reflected light and attenuate the first reflected light according to an attenuation parameter value.
In an embodiment of the invention, the second optical scanning module includes a second optical circulator, a second optical collimator, and a second convex lens. The second optical circulator is connected to the first optical coupler through an optical fiber to receive a second incident light ray, wherein the second incident light ray enters from the first port of the second optical circulator and exits from the second port. The second optical collimator is connected to the second port of the second optical circulator through an optical fiber, and the second optical collimator is used for converting divergent light of the second incident light into parallel light. The second convex lens is arranged in front of the second light collimator, wherein the second incident light passes through the second light collimator and the second convex lens to emit to a plane mirror so as to generate a second reflected light.
In an embodiment of the invention, the two input ports of the second optical coupler are respectively connected to the output port of the electrically controlled attenuator and the third port of the second optical circulator through optical fibers to respectively combine the first reflected light and the second reflected light.
In an embodiment of the invention, the first incident light and the second incident light reach the object to be observed and the plane mirror respectively and simultaneously.
In an embodiment of the invention, the first reflected light and the second reflected light reach the second optical coupler at the same time.
In an embodiment of the present invention, the attenuation parameter value of the electrically controlled attenuator is manually or automatically set according to the type of the object to be observed.
In summary, the all-fiber three-dimensional tomography system provided by the invention can bring the following effects:
1. the line or plane scanning can be rapidly carried out on an optical scattering medium such as biological tissues and the like so as to obtain a high-resolution three-dimensional image;
2. the whole optical tomography system is more easily and accurately erected through the optical fiber line; and
3. has high elasticity, high scanning resolution and high efficiency.
The purpose, technical content, features and effects of the present invention will be more readily understood through the following detailed description of specific embodiments.
Drawings
Fig. 1 is a block diagram of an all-fiber three-dimensional tomography system according to the present invention.
FIG. 2 is a detailed block diagram of the all-fiber three-dimensional tomography system of the present invention.
Description of reference numerals: 100-all-fiber three-dimensional tomography system; 110-swept-frequency laser; 120-a first optical coupler; 130-a first optical scanning module; 132-a first optical circulator; 134-a first light collimator; 136-a first convex lens; 138-an electrically controlled attenuator; 140-a second optical scanning module; 142-a second optical circulator; 144-a second light collimator; 146-a second convex lens; 150-a second optical coupler; 160-a balanced detector; IL-initial incident light; TL 1-first incident ray; TL 2-second incident ray; BL 1-first reflected light; BL 2-second reflected light; PL1 — first target ray; PL 2-second target ray; TML-optical measurement signal; TA-object to be observed; MA-plane mirror.
Detailed Description
In order to solve the problems of the prior art, the inventor of the present invention has studied and developed for many years to improve the scaling of the existing products, and then, how to use an all-fiber three-dimensional tomography system to achieve the most efficient function will be described in detail.
Optical Coherence Tomography (OCT) can generate a non-invasive three-dimensional deep image of a wafer or a skin tissue, based on the principle of michelson interferometer, which forms an interference phenomenon by changing the phase of a reflected beam from a reference end and a reflected beam from an object to be detected when they are overlapped, so as to form a three-dimensional deep image of the tissue to be detected.
Referring to fig. 1, fig. 1 is a block diagram of an all-fiber three-dimensional tomography system according to the present invention. As shown in the figure, the all-fiber three-dimensional tomography system 100 of the present disclosure adopts an all-fiber line to construct the whole optical system to fully exert the advantages of the optical fiber, and is particularly suitable for the field of performing three-dimensional tomography on an object to be observed at a high speed, and can greatly retain the depth and thickness information of the object to be observed. The all-fiber three-dimensional tomographic scanning system 100 includes a swept-frequency laser 110, a first optical coupler 120, a first optical scanning module 130, a second optical scanning module 140, a second optical coupler 150, and a balance detector 160.
Further, the swept-frequency laser 110 is configured to emit laser Light with different wavelengths (the spectrum is quite wide) at different times, and the Light Source of the swept-frequency laser 110 is a Low Coherence Light Source (Low Coherence Light Source), which is mainly configured to generate an initial Light beam, which can achieve high resolution. The first optical coupler 120 is connected to the swept-frequency laser 110 by an optical fiber, and the first optical coupler 120 is configured to receive an initial incident light IL emitted by the swept-frequency laser 110 and split the initial incident light IL into a first incident light TL1 and a second incident light TL2, where the amount of the first incident light TL1 is 40-60 times that of the second incident light TL2, and in this embodiment, the first incident light is 49 times, but is not limited to 49 times. The first optical scanning module 130 is connected to the first optical coupler 120 by an optical fiber to receive a first incident light ray TL1, wherein the first incident light ray TL1 is emitted to the object to be observed TA to generate a first reflected light ray BL1, wherein the object to be observed TA may be a wafer, skin or other object according to actual usage.
In addition, the second optical scanning module 140 is connected to the first optical coupler 120 by an optical fiber to receive the second incident light TL2, wherein the second incident light TL2 is emitted to a plane mirror MA to generate a second reflected light BL2. The first incident light TL1 and the second incident light TL2 reach the object TA to be observed and the plane mirror MA at the same time, respectively, or substantially at the same time. The second optical coupler 150 is connected to the first optical scanning module 130 and the second optical scanning module 140 by optical fibers to combine the first reflected light beam BL1 and the second reflected light beam BL2, wherein two output ports of the second optical coupler 150 output the first target light beam PL1 and the second target light beam PL2 with the same quantity of light beams and the first target light beam PL1 and the second target light beam PL2 perform an optical interference effect with each other. The first reflected light ray BL1 and the second reflected light ray BL2 reach the second optical coupler 150 at the same time. The balance detector 160 is connected to two output ports of the second optical coupler 150 by optical fibers to receive the first target light PL1 and the second target light PL2, and outputs an optical measurement signal TML, which is an interference image with three-dimensional information, after signal processing. As can be seen from the above description, the all-fiber three-dimensional tomographic scanning system 100 of the present invention utilizes the technology of capturing optical signals to obtain images and adopts an all-fiber circuit architecture, so as to rapidly perform line or plane scanning on an optical scattering medium, such as a biological tissue, to obtain a high-resolution three-dimensional image.
Next, the all-fiber three-dimensional tomography system 100 will be described in further detail.
Please refer to fig. 2, fig. 2 is a detailed block diagram of an all-fiber three-dimensional tomography system according to the present invention. The first optical scanning module 130 includes a first optical circulator 132, a first optical collimator 134, a first convex lens 136 and an electrically controlled attenuator 138. The first optical circulator 132 is connected to the first optical coupler 120 by an optical fiber to receive the first incident light ray TL1, wherein the first incident light ray TL1 enters from the first port of the first optical circulator 132 and exits from the second port. The first light collimator 134 is connected to the second port of the first light circulator 132 by an optical fiber to receive the first incident light ray TL1, and is configured to convert divergent light of the first incident light ray TL1 into parallel light. The first convex lens 136 for focusing is disposed in front of the first light collimator 134, wherein the first incident light TL1 passes through the first light collimator 134 and through the first convex lens 136 to emit towards the object TA to be observed, so as to generate a first reflected light BL1. The input port of the electrically controlled attenuator 138 is fiber-connected to the third port of the first optical circulator 132 to receive the first reflected light BL1 and attenuate, i.e., reduce the amount of light, according to an attenuation parameter value. The attenuation parameter value of the electrically controlled attenuator 138 is manually or automatically set according to the type of the object TA to be observed, so as to flexibly adjust the amount of the first reflected light rays BL1, thereby optimizing the whole all-fiber three-dimensional tomography system 100.
In addition, the second optical scanning module 140 includes a second optical circulator 142, a second optical collimator 144, and a second convex lens 146. The second optical circulator 142 is connected to the first optical coupler 120 by an optical fiber to receive a second incident light ray TL2, wherein the second incident light ray TL2 enters from the first port and exits from the second port of the second optical circulator 142. The second light collimator 144 is connected to the second port of the second light circulator 142 by an optical fiber to receive the second incident light ray TL2, and the second light collimator 144 is configured to convert the divergent light of the second incident light ray TL2 into parallel light. The second convex lens 146 for focusing is disposed in front of the second light collimator 144, wherein the second incident light ray TL2 passes through the second light collimator 144 and through the second convex lens 146 to the plane mirror MA to generate a second reflected light ray BL2. Next, the two input ports of the second optical coupler 150 are respectively connected to the output port of the electrically controlled attenuator 138 and the third port of the second optical circulator 142 by optical fibers to respectively combine the first reflected light BL1 and the second reflected light BL2.
As can be seen from the above description, in a system environment using an optical fiber line as a main connection line of the all-fiber three-dimensional tomography system 100, the light path of the first incident light TL1 and the light path of the second incident light TL2 are equivalent to each other, and the light path of the first reflected light BL1 and the light path of the second reflected light BL2 are equivalent to each other. Wherein more than 90% of laser energy is concentrated on the sample, and only a single wavelength is output instantly, the laser energy is held by the single wavelength, unlike the traditional OCT laser energy shared by multiple wavelengths, therefore, the interference image detected finally by the invention is better than that of the traditional OCT.
The tomography system adopting the all-fiber line can be applied to the optical coherence tomography of non-metal objects. For example, the present invention may be applied to defect inspection and sizing of non-metallic articles in the semiconductor manufacturing industry, such as wafers, transparent glue, glass or plastic films. In the present invention, due to the high-tolerance nature of optics, information of micron or even sub-micron dimensions of the entire object to be observed can be obtained. In addition, by using the invention, the flatness, surface roughness or film thickness of the film surface can be checked, and other information about the non-metal object can be obtained by constructing a three-dimensional image.
In summary, the all-fiber three-dimensional tomography system provided by the invention can bring the following effects:
1. the line or surface scanning can be rapidly carried out on an optical scattering medium such as biological tissues and the like so as to obtain a high-resolution three-dimensional image;
2. the whole optical tomography system is more easily and accurately erected through the optical fiber line; and
3. has high elasticity, high scanning resolution and high scanning efficiency.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Therefore, all the equivalent changes or modifications according to the features and the spirit of the claims should be included in the scope of the present invention.
Claims (7)
1. An all-fiber three-dimensional tomography system, particularly for high-speed three-dimensional tomography of an object to be observed, the all-fiber three-dimensional tomography system comprising:
a frequency-scanning laser for emitting laser beams with different wavelengths;
a first optical coupler, which is connected to the swept-frequency laser by an optical fiber, and is used for receiving an initial incident light emitted by the swept-frequency laser and splitting the initial incident light into a first incident light and a second incident light, wherein the quantity of the first incident light is 40-60 times that of the second incident light;
a first optical scanning module, which is connected to the first optical coupler by an optical fiber to receive the first incident light, wherein the first incident light is emitted to the object to be observed to generate a first reflected light;
a second optical scanning module, which is connected to the first optical coupler by an optical fiber to receive the second incident light, wherein the second incident light is emitted to a plane mirror to generate a second reflected light;
a second optical coupler connected to the first optical scanning module and the second optical scanning module by optical fibers to respectively combine the first reflected light and the second reflected light, wherein two output ports of the second optical coupler output a first target light and a second target light of the same quantity of light and perform optical interference effect with each other; and
and a balance detector connected to the two output ports of the second optical coupler via optical fibers to receive the first target light and the second target light and output an optical measurement signal after signal processing.
2. The all-fiber three-dimensional tomography system as claimed in claim 1, wherein the first optical scanning module comprises:
a first optical circulator connected to the first optical coupler by an optical fiber to receive the first incident light, wherein the first incident light enters from a first port of the first optical circulator and exits from a second port;
a first optical collimator connected to the second port of the first optical circulator by an optical fiber, the first optical collimator being configured to convert divergent light of the first incident light into parallel light;
a first convex lens, which is arranged in front of the first light collimator, wherein the first incident light passes through the first light collimator and through the first convex lens to emit to the object to be observed so as to generate a first reflected light; and
an electrically controlled attenuator having an input port connected to the third port of the first optical circulator by an optical fiber to receive the first reflected light and attenuate it according to an attenuation parameter value.
3. The all-fiber three-dimensional tomography system as claimed in claim 1, wherein the second optical scanning module comprises:
a second optical circulator connected to the first optical coupler by an optical fiber to receive the second incident light, wherein the second incident light enters from the first port of the second optical circulator and exits from the second port;
a second optical collimator connected to the second port of the second optical circulator by an optical fiber, the second optical collimator being configured to convert divergent light of the second incident light into parallel light; and
a second convex lens disposed in front of the second light collimator, wherein the second incident light passes through the second light collimator and the second convex lens to emit to a plane mirror to generate a second reflected light.
4. The all-fiber three-dimensional tomography system as claimed in claim 2 and 3, wherein the two input ports of the second optical coupler are respectively connected to the output port of the electrically controlled attenuator and the third port of the second optical circulator by optical fibers for respectively combining the first reflected light and the second reflected light.
5. The all-fiber three-dimensional tomography system as claimed in claim 1, wherein the first incident light and the second incident light reach the object to be observed and the plane mirror simultaneously.
6. The all-fiber three-dimensional tomography system of claim 1 wherein the first reflected light and the second reflected light reach the second optical coupler simultaneously.
7. The all-fiber three-dimensional tomographic scanning system as in claim 2, wherein the attenuation parameter value of the electrically controlled attenuator is manually or automatically set according to the type of the object to be observed.
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