KR100460186B1 - System for optical tomography and the method using the same - Google Patents

Abstract

The present invention relates to an optical tomography system and method, and more particularly, to an optical tomography system and method capable of minimizing signal noise and restoring an image with high resolution without being limited to the shape of a target.

To this end, the present invention is a laser light source having a different wavelength of absorption coefficient corresponding to the target, a light transmitting unit for transmitting the light from the laser light source, a photo detector for detecting the light passing through the light transmitting unit and the photo detector Characterized in that it comprises a signal processor for processing the signal from.

Description

Optical tomography system and method {SYSTEM FOR OPTICAL TOMOGRAPHY AND THE METHOD USING THE SAME}

The present invention relates to an optical tomography system and method, and more particularly, to provide an optical tomography system and method for minimizing signal noise and restoring an image with high resolution without being limited to the shape of a target. .

In general, tomography (TOMOGRAPHY) refers to a detailed inspection that is carried out to grasp the minute internal structure, etc. that is not well known by only one direction of simple imaging.

Conventional imaging methods widely used in the medical and industrial fields include tomography using X-ray or ultrasound.

The imaging method using the X-ray has a big disadvantage that the effect on the living body, the imaging method using the ultrasound has a disadvantage of low spatial resolution and instantaneous resolution.

Therefore, a method of photographing a target using optical tomography (OPTICAL TOMOGRAPHY) has been studied.

Optical tomography refers to the reconstruction of an unknown internal structure into an image by optically nondestructive methods.

Among the conventional optical tomography methods, there is a non-time method proposed by J. Hebden et al. (Appl. Opt., Vol 32, pp. 372-380 (1993)).

The non-timed method is a method of measuring and detecting the time when the pulsed light from the light source is detected by the photodetector. Light scattered and incident on the photodetector passes through a distant path, and thus is incident later than light entering straight. Therefore, the structure is photographed by measuring the detection time of the incident light.

However, the non-time method has a disadvantage in that simultaneous measurement is difficult, and it is difficult to distinguish the scattered light and the straight light.

In addition, a tomography method using scanning method has been proposed by W. Wang et al. (US Pat. No. 6,252,925B1, System and method for performing computed tomography with fiber waveguide).

The scanning method is a method of spatially moving a light source or a target, and a device used for scanning light has a disadvantage in that the time resolution is complicated.

On the other hand, a laser tomography method for statistics of fluid fields has been proposed by Y. Sivathanu et al. (US Pat. No. 6,184,989B1, Laser sheet tomography apparatus for flow field statistics).

However, this method has disadvantages in that the structure and target of the laser extension must be in a straight line and a complicated optical system for linear transformation of the phase is required.

In addition, an optical tomography method using a laser and an optical fiber has been proposed by H. Battarbee et al. (US Pat. No. 6,291,824B1, Apparatus and method for high bandwidth optical tomography).

However, this method requires the use of a plurality of light sources, and there is a disadvantage in that it is not possible to distinguish between attenuation due to absorption and attenuation due to scattering.

The present invention has been proposed in view of the above problems, and an object of the present invention is to provide an optical tomography system and method capable of restoring an image of a target by minimizing noise of a signal.

It is another object of the present invention to provide an optical tomography system and method capable of restoring an image without being limited to the shape of the target.

It is still another object of the present invention to provide an optical tomography system and method capable of reconstructing an image with high temporal resolution and spatial resolution.

1 is a schematic diagram of an optical tomography system according to an embodiment of the present invention.

FIG. 2 is an enlarged view of an incident part and a light receiving part equipped with a focusing lens and a coupling device in the optical tomography system of FIG. 1; FIG.

3 is a state diagram illustrating a process of orthogonal radiation to a target in the optical tomography system of FIG.

4 is a state diagram showing a process of axially radiating to a target in the optical tomography system of FIG.

5 is a flowchart of an optical tomography method according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

10: laser light source 12: first laser

14: second laser 20: optical splitter

30: optical modulator 40: optical coupler

50: incident part 52: first focusing lens

54: first coupling device 60: light receiving unit

62: second focusing lens 64: second coupling device

70: photodetector 80: signal processor

90: computer A: target

B: light transmission part C: transmission line

S10: light emission step S2O: light branch step

S30: light modulation step S40: light coupling step

S50: incident step S60: light receiving step

S70: detection step S80: signal processing step

S90: Image Restoration Step

In order to achieve the object as described above, the optical tomography system according to the present invention is a laser light source having a wavelength different from the absorption coefficient corresponding to the target, a light transmitting unit for transmitting the light from the laser light source, the light It may include a photo detector for detecting the light passing through the transmission unit and a signal processor for processing a signal from the photo detector.

The laser light source may use a plurality of wavelength tunable lasers in the visible and infrared regions, and may use an optical fiber as the light transmitting unit.

The optical tomography system may further include an optical splitter that splits the light emitted from the light transmitting unit.

The optical splitter may use a cylinder lens, and may use an optical expansion optical system.

The optical tomography system may further include an optical modulator for frequency domain modulating the light emitted through the optical splitter, and may further include an optical coupler for coupling the light having two wavelengths through the optical modulator. The light emitter may further include an incidence unit for incident light from the photocoupler to the target.

The incidence part may inject a plurality of lights to the target in a direction orthogonal to each other, and may inject a plurality of lights to the target in the axial direction. The incident part may further include an optical system for reducing the spread of light in the target and a coupler for reducing the reflection of light at the interface between the target and the target.

The optical tomography system may further include a light receiving unit for receiving the light passing through the target.

The signal processor may be composed of an amplifier, a demodulator, and an analog to digital converter. The optical tomography system may further include a computer for image restoring and controlling the signal from the signal processor.

Optical tomography method according to the present invention is a light emission step of emitting light by correcting the absorption effect using a wavelength-variable laser light source, an incident step of incident light emitted from the laser light source to the target, incident to the target The method may include a detection step of detecting the transmitted light, a signal processing step of signal processing the light detected in the detection step, and an image restoration step of image restoring a signal of the light that has passed the signal processing step.

The light emitting step may further include an optical branching step of dividing the light emitted from the laser light source into a plurality of lights, and the optical branching step may further include an optical modulation step of frequency-domain modulating the light.

The optical modulation step may further include an optical coupling step of coupling the light of the two wavelengths passed through the optical modulator step.

The incident step may further include a light receiving step for receiving the light passing through the target.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, in adding reference numerals to the components of each drawing, it should be noted that the same components and the like have the same reference numerals as much as possible even if displayed on different drawings. In addition, in the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 is a schematic diagram of an optical tomography system according to an embodiment of the present invention.

As shown in FIG. 1, an optical tomography system according to an exemplary embodiment of the present invention includes a laser light source 10, a light transmitting unit B, an optical splitter 20, an optical modulator 30, and an optical combiner 40. ), The incident part 50, the light receiving part 60, the photodetector 70, the signal processor 80, and the computer 90.

The laser light source 10 is a device that emits light to the target A, and is composed of first and second lasers 12 and 14 of different wavelengths.

The first and second lasers 12 and 14 are determined by passing through the target body A in consideration of the optical thickness of the target body A. Light having wavelengths and intensities having different absorption coefficients is emitted from the first and second lasers 12 and 14, and the light emits light in the visible or infrared region according to the optical characteristics of the target A. FIG. use.

The first and second lasers 12 and 14 may use wavelength-tunable lasers such as DYE LASER according to the characteristics of the target A. FIG.

In addition, the laser light source 10 may be used to have an output form of a continuous output or pulse repeat type, if necessary, the output form and output intensity can be controlled by a computer (90).

The light transmitting unit B is a portion corresponding to a path for transmitting light emitted from the laser light source 10, and may use an optical fiber.

The optical splitter 20 is a device for dividing the light emitted from the laser light source 10 into various branches, and may use a cylinder lens or an optical expansion optical system.

The optical modulator 30 is an apparatus for temporally controlling the passage of light in order to discriminate light branched through the optical splitter 20, and includes an AO modulator and an EO modulator.

The optical coupler 40 is a device for coupling the light of two wavelengths branched from the first and second lasers 12 and 14, respectively, and applies a multicoupler or the optical splitter 20 to the reverse. Can be used.

In addition, the respective light transmitting parts to which the light split from the first and second lasers 12 and 14 are transmitted to combine the light of different wavelengths split from the first and second lasers 12 and 14. The end of B) can be positioned as close as possible.

The incident part 50 is a part for injecting the light coupled from the optical coupler 40 to the target A. The incident part 50 is a part corresponding to the opposite end of the light transmitting part B connected to the optical coupler 40.

The incident part 50 may include a first focusing lens 52 and a first coupling device 54.

The light receiving unit 60 is a portion that receives the light passing through the target A. The light receiving unit 60 is a portion corresponding to an end of the light transmitting unit B through which the light passing through the target A is transmitted.

The light receiving unit 60 may include a second focusing lens 62 and a second coupling device 64.

2 is an enlarged view of an incident part and a light receiving part in which a focusing lens and a coupling device are mounted in the optical tomography system of the present invention.

As shown in FIG. 2, each of the incident part 50 and the light receiving part 60 includes a light transmitting part B for transmitting light, a first and second focusing lens 62 for preventing light from spreading, and a reflection. First and second coupling devices 54 and 64 are provided to reduce the number.

It is preferable to use the first and second coupling devices 54 and 64 having a refractive index about the middle of the refractive index of the target body A and the optical fiber refractive index of the light transmitting unit B.

3 is a state diagram illustrating a process of orthogonally radiating to a target in the optical tomography system of the present invention, Figure 4 is a state diagram showing a process of axial radiation to the target.

As shown in FIG. 3, when the light is orthogonally radiated to the target A, the incident part 50 may be arranged to be orthogonal to each other.

As shown in FIG. 4, when the light is radiated to the target A toward the center of the axis, the incident part 50 may be arranged to face the center of the target A. FIG.

The photodetector 70 detects light passing through the light receiving unit 60 and converts the optical signal transmitted to the light transmitting unit B into an electrical signal.

The photodetector 70 is composed of a photomultiplier tube or photodiode suitable for measuring the wavelength, intensity, and waveform of the light passing through the target body A.

The signal processor 80 is a device for processing light emitted from the photodetector 70, and is composed of an amplifier, a demodulator, and an analog-to-digital converter.

The amplifier is a part for amplifying an electrical signal, the demodulator is a part for discriminating a signal for each path through frequency domain demodulation, and the analog-to-digital converter is a part for converting an analog signal into a digital signal.

The computer 90 is an apparatus for restoring an image from the signal processor 80 and controlling the laser light source 10, the optical modulator 30, and the signal processor 80.

Hereinafter, a method of optical tomography according to an embodiment of the present invention will be described according to the photographing order and application principle with reference to FIGS. 1 and 5.

5 is a flowchart of an optical tomography method according to an embodiment of the present invention.

As shown in Figure 5, the optical tomography method according to an embodiment of the present invention, the light emission step (S10), the optical branching step (S20), the light modulation step (S30), the optical coupling step (S40), incident It consists of a step S50, a light receiving step S60, a detection step S70, a signal processing step S80, and an image restoring step S90.

First, in the light emission step (S10) it emits two lights of different wavelengths.

Secondly, in the optical branching step S20, the light emitted from the laser light source is split into a plurality of lights.

Third, in the light modulation step (S30), the light is frequency-domain modulated.

Fourth, in the optical coupling step (S40) combines the light of the two wavelengths passed through the optical modulation step (S30).

Fifth, in the incident step (S50), the light emitted from the laser light source 10 is incident on the target body (A).

Sixth, the light receiving step (S60) receives the light passing through the target (A).

Seventh, the detection step (S70) detects the light transmitted through the target body (A).

Eighth, in the signal processing step S80, the signal detected in the detection step S70 is signal processed.

Ninth, the image restoration step (S90) is to restore the image of the light signal passed through the signal processing step (S80).

In the light emission step S10, light having different wavelengths is emitted from the first and second lasers 12 and 14 of the laser light source 10.

The first and second lasers 12 and 14 have absorption coefficients suitable for the target A, and are for comparing the effects of absorption by injecting light having different transmittances into the target A. FIG.

In the light emission step S10, a plurality of separate laser light sources 10 may be used in parallel, and the laser light source 10 may emit light having different transmittances from two lasers.

This is because the absorption and scattering effects can be corrected by using the single laser light source 10 but using the first and second lasers 12 and 14 having different wavelengths.

That is, since the material selectively absorbs light of a specific wavelength according to its atomic and molecular structure, the optical concentration of the target A can be calculated by measuring the intensity of transmitted light using a wavelength having a different absorption coefficient. This is because the optical properties can be used to reduce the effects of scattering.

In the optical branching step S20, the light emitted from the laser light source 10 is split into a plurality of lights.

This does not require the use of complex equipment, such as using a plurality of laser light source 10 in parallel by splitting the light using the optical splitter 20, there is an inexpensive advantage.

In the optical modulation step (S30), it is possible to discriminate which path the light branched from the optical branching step (S20) passes through, and to reduce interference with light of adjacent paths and to be distinguished from background light. The optical modulator 30 performs frequency domain modulation to control the passage of light in time, so as not to overlap in time with the light in the adjacent path.

In the optical coupling step (S40) it combines the light of the two wavelengths passed through the optical modulation step (S30). This allows two light having different wavelengths to pass through the target A through the same path.

To this end, in the optical coupling step (S40), the optical fibers through which the light having different absorption coefficients pass are arranged as close as possible in space, or are configured in a form of 2-1 coupling through the optical splitter 20 to combine the light. You can.

In the incident step S50, the light coupled from the optical coupler 40 is incident on the target body A through the light transmitting unit B, and an end of the light transmitting unit B may be an incident unit. .

In the incident step (S50), in order to obtain a two-dimensional image of the target (A) of the portion corresponding to the incident portion 50 so that a plurality of light is incident on the target (A) in two orthogonal directions The optical fibers may be arranged orthogonally, or may be arranged in the circumferential direction of a circle centered on the center of the target body A. FIG.

When the target body A is taken as a whole, the incident part 50 is disposed orthogonally, and when the target part A is to be photographed in detail, the light receiving unit 60 is arranged in the axial direction. Let's do it.

In addition, in order to obtain a 3D image of the target A, the optical fiber of the part corresponding to the incident part 50 may be arranged to be loaded in one direction to realize images of various layers.

In addition, the incident part 50 may be equipped with a first focusing lens 52 to prevent the spread of light, and a first coupling device 54 such as a multiplexer may be mounted to reduce reflection.

In the case where the target body A is a material through which light cannot be transmitted, such as an opaque pipe, a through portion may be formed in the target body A to pass through the optical fiber, which is a light transmitting part B, and thus cannot transmit light. The internal structure of the target body A can also be photographed.

The light receiving step (S60) receives the light passing through the target (A), in order to prevent the spread of the light passing through the target (A) can be equipped with a second focusing lens 62, the reflection is A second coupling device 64 such as an optical fluid can be mounted so as to be small.

In the detecting step (S70), the optical signal by the light transmitted through the target A is converted into an electrical signal.

In the detecting step S70, a photodetector 70 suitable for measuring the wavelength, intensity, and waveform of the light transmitted through the target body A is used.

In order for the light emitted from the laser light source 10 to move, an optical fiber, which is a light transmitting part B, is connected from the laser light source 10 to the photodetector 70, and the optical fiber is connected to the laser light source 10. Use a material made of a material suitable for the wavelength.

In the signal processing step (S80), the electrical signal passing through the detection step (S70) passes through the transmission line (C) is incident to the signal processor 80 is processed.

The electrical signal passing through the transmission line C is amplified through an amplifier, a signal for each path is separated through a demodulator, noise is removed, and an analog signal is converted into a digital signal through a converter.

The demodulator demodulates the signals from each photodetector 70 according to the modulation waveform given by the computer 90.

In the image restoring step (S90), the digital signal that has undergone the signal processing step (S80) is calculated to restore the image.

The digital signal passed through the signal processor 80 is transmitted to the computer 90 equipped with the software necessary for image restoration, and the image restoration is performed through a suitable calculation process.

The light emitted from the laser light source 10 may be driven in the form of continuous output or pulse repetition under the control of the computer 90, and may be selected to a wavelength suitable for the target body A.

The temporal control of the optical speed of the optical modulator 30 and the modulation waveform of the signal processor 80 are also controlled by the computer 90.

Hereinafter, reconstructing an image by tomography of the target object A using the optical tomography system according to the present invention will be described.

First, the light passing through the target A decreases in intensity due to absorption and scattering.

The signal appearing on the photodetector 70 is composed of a combination of a signal caused by light entering a straight line whose intensity is reduced by absorption and scattering, a signal scattered by a path of adjacent light, and a noise signal caused by background light.

On the other hand, the absorption is changed depending on the wavelength due to the optical properties of the target (A).

Based on the above premise, the intensity I (λ) of light having a wavelength λ passing through the target body A is given by the following equation.

---(One)

{I} _ {0} (λ) in the above formula (1) is the intensity of light incident on the target A when there is no target A. [Alpha] ([lambda]) is the absorption coefficient for the wavelength [lambda] and the integration of this over the path of light contributes to the attenuation of the light.

C is a correction factor in consideration of scattering, and {I} _ {b} is a signal due to background light.

If there is information on each term of Equation (1), the optical characteristic on the path of light can be calculated by Equation (1), and if there is information on a plurality of paths of light, it is possible to reconstruct the tomography image.

The reconstruction of the image requires excellent spatial resolution and temporal resolution, and it is desirable that the noise is small.

The above embodiments are intended to specifically illustrate the present invention, and do not limit the scope of the present invention. In addition, it can be seen that all simple modifications and variations of the present invention are included in the scope of the present invention.

According to the optical tomography system and method according to the present invention as described above, it is possible to provide an optical tomography system and method which is excellent in spatial resolution using an optical fiber and capable of simultaneous measurement of a target.

In addition, the optical modulator provides an optical tomography system and method in which noise is minimized by modulating a frequency domain.

In addition, by using a single laser light source and a light splitter without using multiple laser light sources in parallel, the device provides a simple and inexpensive optical tomography system and method.

In addition, by using an optical fiber, several lenses are required for linear transformation of an image, and the present invention provides an optical tomography system and method which solves a conventional problem in which images are changed according to their positions and deformation due to temperature is solved.

In addition, the problem that the light source and the target should be in a straight line due to the straightness of the light is solved by using the optical fiber, and the light source and the photodetector can be disposed anywhere, and the optical shape is not limited by the shape of the target and the size of the photodetector. A tomography system and method are provided.

In addition, since the incidence portion may be inserted into the target body, it is also possible to photograph an internal structure such as an opaque pipe through which light cannot pass.

Claims (20)

delete delete In the optical tomography system for transmitting a laser light to the target to obtain and process the tomography data, A plurality of laser light sources having a wavelength corresponding to a target and having different wavelengths; A light transmitting unit which transmits each light emitted from the laser light source through different light paths and enters a target; A photodetector that receives the light passing through the target and converts the light into an electrical signal; And Receiving the electrical signal output from the photodetector includes a signal processor for processing an optical characteristic or an image signal on a path, In order to apply the optical tomography system to a variety of targets, the plurality of laser light source is characterized in that the wavelength-variable laser in the visible and infrared region, The optical transmission tomography system, characterized in that the optical transmission unit (optical fiber). 4. The optical tomography system of claim 3, further comprising a light splitter for each of the light transmitting sections connected to the respective laser light sources to split the light from the light transmitting sections into different light paths. The optical tomography system of claim 4, wherein the optical splitter uses a cylinder lens. The optical tomography system of claim 4, wherein the optical splitter uses an optical expansion optical system. The frequency domain modulation of each of the optical paths branched from the optical splitter to receive the light splitted from the respective optical splitters so as to frequency-modulate the optical signal to be delivered to the target to increase the selectivity of the optical signal. and an optical modulator for frequency modulation. The target of claim 7, wherein the targets are coupled by combining optical paths of different laser light sources passing through the optical modulator to form one optical path branched from the different laser light sources and receiving light having two wavelengths passing through the optical modulator. An optical tomography system, characterized in that it further comprises a plurality of optical couplers for transmitting to the sieve. 9. The optical tomography system of claim 8, further comprising an incidence portion around the target to allow light from the optical coupler to enter the target. The incidence portions of the incidence portions are perpendicular to each other with respect to the target object such that optical paths are formed in directions perpendicular to each other when the light passing through the plurality of optical couplers passes through the target object. Optical tomography system, characterized in that installed around the target. 10. The method of claim 9, wherein the incidence is provided around the target toward the target center so that each of the light passing through the plurality of optical coupler is transmitted radially toward the center of the target. Optical tomography system, characterized in that. 12. The optical system of claim 11, wherein the incidence portion is further configured to optically couple the incidence portion and the target to an optical system for reducing the spread of light in the target and a coupler for reducing the reflection of light at an interface between the target and the target. Optical tomography system comprising a. 12. The optical tomography system of claim 11, further comprising a light receiving unit between the target and the photodetector at a corresponding position to receive the light passing through the target from the incidence. The optical tomography system of claim 3, wherein the signal processor comprises an amplifier, a demodulator, and an analog to digital converter. The optical tomography system of claim 3, further comprising a computer for image restoring and controlling the signal from the signal processor. A light emission step of emitting light by correcting an absorption effect using a wavelength tunable laser light source; An incident step of injecting light emitted from the laser light source into a target; A detection step of detecting light incident on the target; A signal processing step of signal processing the light detected in the detection step; And And an image restoring step of restoring an image of the light that has undergone the signal processing step. 17. The optical tomography method of claim 16, further comprising an optical branching step of splitting light emitted from the laser light source into a plurality of lights. 18. The optical tomography method of claim 17, wherein the optical branching step further comprises an optical modulation step of frequency-domain modulating light. 19. The optical tomography method of claim 18, wherein the optical modulation step further comprises an optical coupling step of coupling the light having two wavelengths through the optical modulator step. 18. The optical tomography method of claim 16, wherein the incident step further comprises a light receiving step of receiving light passing through the target.