JPH02150747A - Device for optical tomographic imaging - Google Patents

Abstract

PURPOSE:To obtain the optical tomographic image of a substance to be measured by irradiating the substance to be measured with a laser light beam and classifying and detecting only rectilinear component out of transmitted light beam by utilizing the directivity of optical heterodyne detection. CONSTITUTION:The laser light beam projected from a laser device 1 is splitted into two such as a laser light beam L1 and a laser light beam for reference L2 by a beam splitter 2. A sample 5 is irradiated with the laser light beam L1 and only the straight advancing component, out of the transmitted light, which is tinged with the optical absorption information of the sample 5 is extracted and optically mixed with the laser light beam L2 by a half mirror 13. In such a case, the sample 5 is irradiated with the laser light beam L1 by deviating the frequency thereof and the scattered laser light beam which is transmitted is condensed on an aperture 7. The optically mixed laser light beams are detected by utilizing the directivity of transmittivity of only straight advancing component in a specified direction with the aid of the optical heterodyne detection by a photoelectric detector 14. Thus, the distribution of the substance to be measured of the sample 5 is expressed as the tomographic image.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for imaging a tomographic image of an object to be measured using laser light and optical heterodyne detection.

[Conventional technology]

BACKGROUND ART To date, various tomography methods using physical energy have been devised to observe the inside of a material without destroying the material.

Among them, X-ray CT is the most representative one. This has made it possible to non-invasively observe the internal form of the object to be measured as a tomographic image. Additionally, MHI and ultrasound imaging methods that do not involve the risk of X-ray exposure have been developed.

[Problem to be solved by the invention]

Conventionally, CT devices using light have not been realized because materials with good light transmittance (linear transmittance)
Since it is easier to observe the inside than the outside, CT
This is because there was no need to make changes. In addition, in samples with poor direct light transmittance, Lamber
CT conversion was difficult because t-Beer's law did not hold.

On the other hand, in recent years, there has been a particular need to measure the conversion of essential substances within living organisms that accompany the life activities of living systems without interfering with life activities.

However, when attempting to observe functional changes due to material conversion inside a sample, X-ray CT can only obtain morphological information, and MRI only observes the dynamics of protons;
At T, only the dynamics of substances such as phosphorus and carbon could be observed. However, these methods all apply to the sample to be measured.
Currently, it is not possible to acquire internal functional information non-invasively.

The present invention is intended to solve the above-mentioned problems, by irradiating a laser beam onto an object to be measured, and separately detecting only the straight component of the transmitted laser beam using the directivity of optical heterodyne detection. An object of the present invention is to provide an optical tomographic imaging device capable of obtaining an optical tomographic image of an object to be measured.

[Means to solve the problem]

For this purpose, the optical tomographic imaging device of the present invention irradiates a sample with laser light, mixes the transmitted light with a reference light, and uses optical heterodyne detection to detect a specific direction of the laser light transmitted through a light scattering body. It is characterized by measuring the transmittance of only the straight component and obtaining a tomographic image of the distribution of specific substances in the sample.

In addition, it includes a laser device, a beam splitter that splits the laser beam from the laser device, a frequency converter that shifts the frequency of one of the laser beams split by the beam splitter, and a sample moving means that moves and rotates and converts the frequency. a first optical system for obtaining a parallel beam from the laser beam that has passed through the sample; and a first optical system for obtaining a parallel beam from the laser beam that has passed through the sample; a second optical system for producing a parallel light beam having the same spot diameter; an optical heterodyne detection means for optically mixing the output lights of the first optical system and the second optical system and extracting a beat component;
It is characterized by comprising a calculation means into which the optical heterodyne detection output and the sample position information from the sample moving means are input, and obtaining a tomographic image of the sample from the optical heterodyne detection output and the sample position information.

Furthermore, a laser device, a beam splitter that splits the laser beam from the laser device, a frequency converter that shifts the frequency of one of the laser beams split by the beam splitter, and a sample stage that is moved and rotated by the sample moving means. An expanding optical system that expands the frequency-converted laser beam and irradiates it onto the sample, and obtains a parallel beam with a predetermined spot diameter from the transmitted light, and a beam splitter that splits the other laser beam into the beam of the expanding optical system. A scanning optical system that scans with a magnifying optical system,
Optical heterodyne detection means optically mixes the output light of the scanning optical system and extracts a beat component, and a calculation means into which the optical heterodyne detection output, sample position information from the sample moving means, and scanning signal are input. It is characterized by obtaining a tomographic image of the sample from the output, sample position information, and scanning signal.

[Effect]

Laser light emitted from the laser device (wavelength λ, frequency ω
) is divided into two parts, one side is shifted by the frequency Δω and irradiated onto the sample, and the transmitted and scattered laser light is focused by a lens onto an aperture placed at its focal position. The light that has passed through the aperture is converted by the lens located behind the aperture into a parallel light beam that is equal to the diffraction limit determined by the aperture diameter and the aperture between the lenses located behind the aperture, and is collimated equally with this parallel light beam. It is optically mixed with one of the laser beams and detected by a photoelectric detector.

This operation is performed together with scanning in a direction perpendicular to the optical axis of the laser beam, and then the sample is rotated by Δθ, and similar scanning detection is performed over a rotation angle of 0° to 36°. Using the position signal and detection signal obtained in this way, a computer calculates image reproduction from the projection data, and creates a reproduced image on the monitor. Here, by adjusting the wavelength λ to the absorption band of the substance to be measured within the sample and varying it in various ways, a tomographic image of the distribution of a specific substance within the sample can be obtained.

In addition, the frequency-shifted laser beam is expanded and irradiated onto the sample, the transmitted light is made into a parallel beam, and the other laser beam that is split into two is transmitted through the sample and scanned within the expanded parallel beam to combine both. By performing light mixing, calculations for image reproduction can be performed in the same manner, and a tomographic image of the distribution of a specific substance within the sample can be similarly obtained.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the optical tomographic imaging apparatus of the present invention. In the figure, 1 is a laser device, 2 is a beam printer, 3.3', 9.10 is a mirror 4 is a frequency converter,
5 is a sample, 6, 8, 11.12 is a lens, 7 is an aperture, 13 is a half mirror, 14 is a photoelectric detector, 16 is a selection level measuring device, 17 is a sample stage, 18 is a sample stage controller,
19 is a computer, and 20 is a monitor.

A laser beam emitted from a laser device 1 is split into two by a beam splitter 2 into LI and L2. The laser beam is guided by a mirror 3 to a frequency converter 4 made of, for example, an electro-optic crystal, and is frequency-shifted by Δω, and then reflected by a mirror 3'.
The sample 5 is irradiated by the beam. The scattered laser light that has passed through the sample is focused by a lens 6 onto an aperture placed at the rear focal position. The light passing through the aperture is converted into a parallel light beam by a lens 8 whose front focal point is at the aperture position, and converted into a parallel light beam having a diffraction limit diameter determined by the aperture diameter of the lens 8 and the diameter of the aperture.

These optical systems cut out off-axis scattered light that is scattered in all directions, and extract only the straight components that carry information about the light absorption of the sample.

On the other hand, laser beam L for reference! Mirror 9. Through l'o,
The light is collected by the lens 11, and is converted into a parallel light beam L4 with the same spot diameter as a laser beam by the lens 12, which uses the rear focal position of the lens 11 as the front focal position, and is converted into a parallel light beam L4 with the same spot diameter.
13, the light is mixed with. and photoelectric detector 14
The amplifier 15 and the selective level measuring device 16 selectively detect only the component of the beat frequency Δω. By this heterodyne detection, scattered components that are not coherent with the laser beam L4 are cut out, so that only the component carrying light absorption information of the sample among the straight components can be detected.

Similar detection is performed while scanning the sample stage 17 in the X direction perpendicular to the laser beam optical axis.
scanning and detection in the X direction in the same manner as described above.

The above scanning is performed over an angle of θ from 0° to 360'.

X-ray scanning and θ rotation of the sample stage 17 are performed by the sample stage controller 1.
The position signal is input into the computer 19 along with the signal from the selected level measuring device. The computer 19 performs calculations for image reproduction from the projection data obtained by the above-described scanning, and forms a reproduced image on the monitor 20.

Note that by varying the wavelength of the laser beam to match the absorption band of each measurement substance in the sample, a specific substance in the sample can be selected and a tomographic image of its distribution can be obtained.

FIG. 2 is a diagram showing another embodiment of the present invention, and the same numbers as in FIG. 1 indicate the same contents. Note that 21 is a laser beam movement control device, and 22, 23, and 24 are lenses.

In the figure, a laser beam emitted from a laser device 1 is split into two parts by a beam splitter 2. The laser beam Ll is guided to the frequency converter 4 by the mirror 3, and
The frequency is shifted by ω, guided by the mirror 3' to the lens 22, focused at the focal point HA, and then irradiated onto the entire sample 5 or the part of the sample to be observed.

The scattered laser light transmitted through the sample 5 is focused by the lens 23 onto an aperture placed in a conjugate position with respect to point A, and only the light focused at point A passes through the aperture. Become.

The light that has passed through the aperture is converted into a parallel light beam by the lens 24 whose front focal point is at the aperture position, and converted by the lens 24 into a parallel light beam with a diffraction limit diameter determined by the aperture diameter of the lens 24 and the diameter of the aperture. Ru. Here, the parallel light beam is set to a diameter that is sufficiently larger than the diameter of L2, which is the reference light.

On the other hand, the reference light L2 separated by the beam splitter 2 is
Mirror 9. Parallel light flux L on half mirror 13 due to lO
t and is detected by a photoelectric detector 14, and only the frequency Δω component is selectively detected by an amplifier 15 and a selective level measuring device 16.

By this heterodyne detection, the scattered components that are not coherent with the laser beam L2 are cut out, as in the case of the embodiment shown in FIG. can.

Now, the laser beam L2 is YY of the parallel beam shown in FIG.
The above-mentioned detection is performed while scanning the mirror 9, 1O, and photoelectric detector 14 by the laser beam movement control device 21 so as to cross the parallel light beam in the ' direction.

Next, the sample table controller 18 of the sample table 17 rotates the sample table 17 by an angle Δθ, and similarly detects the laser beam while scanning in the YY' direction.This operation and the sample table rotation angle θ range from 0'' to 360 m By doing so, the cross-sectional projection data of the sample 5 is inputted to the computer 19 from the sample stage control device 18, laser beam movement control device 21, and selection level measuring device, image reproduction calculations are performed from these projection data, and the data are displayed on the monitor 20. The reconstructed image is constructed above.

In addition, the laser beam is scanned by the mirror 9. The lO1 photoelectric detector 14 and the laser beam movement controller 21 are used to rotate the sample 5 in the direction XX' in Figure 3, and rotate the sample 5 in a plane perpendicular to the plane in Figure 2, that is, in the direction of θ' in Figure 2. By collecting projection data and reproducing the image while performing this, a vertical cross-sectional image of the sample can be obtained. In addition, if the direction that crosses the parallel beam of laser beam L8 is set to any direction between YY' and Xx' in Figure 3, and the sample is rotated around the sample rotation axis corresponding to that direction, A cross-sectional image in any direction can be obtained. By varying the wavelength of the laser beam in accordance with the absorption band of each measurement substance within the sample, a tomographic image of the specific substance distribution within the sample in any direction can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to represent the distribution of a measurement substance in a sample as a tomographic image, and it is possible to
It is possible to provide a method for non-invasively analyzing the distribution of various substances in a sample with a relatively small volume, for which no analytical method exists.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the optical tomographic imaging device of the present invention, FIG. 2 is a diagram showing another embodiment of the present invention, and FIG. 3 is an AA diagram of the parallel light beam in FIG. 2. ' is a sectional view of '. l... Laser device, 2... Beam splitter, 3°3', 9.10... Mirror, 4... Frequency converter,
5... Sample, 6, 8, 11, 12.22, 23.24
... Lens, 7... Aperture, 13... Half mirror 14... Photoelectric detector, 16... Selection level measuring device, 17... Sample stage, 18... Sample stage control device,
19...computer, 20...monitor, 21.
...Laser beam movement control device. applicant

Claims (5)

[Claims] (1) Irradiate the sample with laser light, optically mix the transmitted light and reference light, and measure the transmittance of only the linear component in a specific direction from the laser light transmitted through the light scatterer by optical heterodyne detection, An optical tomographic imaging device characterized by obtaining a tomographic image of a specific substance distribution in a sample. (2) A laser device, a beam splitter that splits the laser beam from the laser device, a frequency converter that shifts the frequency of one of the laser beams split by the beam splitter, and a sample moving means that rotates and rotates the laser beam. A sample stage that is irradiated with the converted laser beam, a first optical system that obtains a parallel beam from the laser beam that has passed through the sample, and a parallel beam of the other laser beam that is split by a beam splitter from the first optical system. a second optical system for producing a parallel light beam having the same spot diameter as the second optical system; and an optical heterodyne detection means for optically mixing the output lights of the first optical system and the second optical system and extracting a beat component.
An optical tomographic imaging device comprising a calculation means into which optical heterodyne detection output and sample position information from a sample moving means are input, and obtaining a tomographic image of a sample from the optical heterodyne detection output and sample position information. . (3) The optical tomographic imaging apparatus according to claim 2, wherein the first optical system includes a lens that focuses the light transmitted through the sample onto an aperture, and a lens that has a front focal point at the aperture position. (4) A laser device, a beam splitter that splits the laser beam from the laser device, a frequency converter that shifts the frequency of one of the laser beams split by the beam splitter, and a sample stage that is moved and rotated by the sample moving means. , an expanding optical system that expands the frequency-converted laser beam and irradiates it onto the sample, and obtains a parallel beam with a predetermined spot diameter from the transmitted light; and a beam splitter that splits the other laser beam with a beam splitter into the expanding optical system. A scanning optical system that scans inside the camera, a magnifying optical system,
Optical heterodyne detection means optically mixes the output light of the scanning optical system and extracts a beat component, and a calculation means into which the optical heterodyne detection output, sample position information from the sample moving means, and scanning signal are input. An optical tomographic imaging device characterized by obtaining a tomographic image of a sample from an output, sample position information, and a scanning signal. (5) The magnifying optical system includes a lens whose back focal point is in front of the sample position, a lens that focuses transmitted light onto an aperture located at a position conjugate with the rear focal point of the lens, and an aperture position. 5. The optical tomographic imaging apparatus according to claim 4, further comprising a lens having a front focal position of .