JP2000342589A - Optical tomographic diagnostic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain good tomographic animation images of the gullet, stomach, intestines, and the like, by obtaining an optical path variable optical system which is high in speed, is wide in a scan range, is less in the intensity change of light and is stable in temperature characteristics. SOLUTION: This optical tomographic diagnostic apparatus is provided with the optical path variable optical system 24 on a reference light side or signal light side at the time of taking an interference signal by dividing the low coherence light from a light source to the signal light and the reference light, and irradiating an observation object with the signal light, then synthesizing the signal light and the reference light again to cause interference and observers the tomographic image of the observation object by changing the optical path length. In such a case, the optical path variable optical system 24 comprises a single mode optical fiber 25 for introduction, a collimator lens 29, a condenser lens 31, a single mode optical fiber 26 for take-out and optical elements 271 and 272 having the faces parallel to each other. The light is passed even number times these optical elements 271 and 272 and is rotated, by which the optical path length is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical tomography diagnostic apparatus, and more particularly, to an optical system for changing an optical path length in an optical tomographic diagnostic apparatus system using low coherent light.

[0002]

2. Description of the Related Art In recent years, an apparatus called OCT (optical tomography diagnostic apparatus) for observing a tomographic structure of a living body using low coherence light having a short coherence distance has been developed.

[0003] In order to observe a tomographic structure using low coherence light, light from a light source that generates low coherence light is separated into signal light and reference light, and the signal light is irradiated on the object to be measured. The reflected light is combined with the reference light again to detect an interference signal between the two lights. At this time, an interference signal is obtained only when the optical path lengths of the signal light and the reference light match, so that the observation position of the measurement target is scanned by changing the optical path length of the reference light or the signal light. As a result, the same effect can be obtained, and the tomographic structure to be measured can be observed.

FIG. 19 is a diagram showing a configuration of an example in which conventional OCT is applied to an endoscope. Light from the low coherence light source 1 is coupled to the single mode optical fiber 2 and guided to the position of the coupler 3. The light is separated by the coupler 3 into a signal light side and a reference light side. The separated light on the reference light side is guided to the position of the optical path length variable optical system 4 by the single mode optical fiber 2. The light returned from the variable optical path length optical system 4 is guided again to the position of the coupler 3 by a single mode optical fiber. On the other hand, the light separated to the signal light side is guided to the signal light side tip optical system 5 by a single mode optical fiber 2 different from the reference light side, irradiated to the subject O from there, and further reflected from the subject O,
The signal light is again combined with the light returned from the reference side by the coupler 3 through the signal light side tip optical system 5 and the single mode optical fiber 2. The combined return light on the reference side and the measurement side is guided to the detector 6 by the single mode optical fiber 2, and the detector 6 detects an interference signal.

FIG. 20 is a diagram showing a configuration of an example of a conventional optical path length variable optical system on the reference light side. The variable optical path length optical system
A single mode optical fiber 2 for guiding light from the coupler 3 to the optical path variable optical system, and a collimator lens 7
, A mirror 8 and a mirror driving device 9. The mirror 8 is mounted on a mirror driving device 9, and the position of the mirror 8 is changed in the optical axis direction by the mirror driving device 9. As a result, the position between the end of the single mode optical fiber 2 and the mirror 8 is changed. The optical path length changes. As a method for driving the mirror 8 in the optical axis direction, a method using a piezoelectric element such as PZT is generally used.

Other examples of the conventional optical path length variable optical system on the reference light side are disclosed in K. K. F. Kwang et. al, O
pt. Lett. 18, 558 to 560 (1993). This optical path length variable optical system is composed of a diffraction grating, a galvanomirror, and a Fourier transform lens. By changing the tilt of the galvanomirror with respect to the optical axis, a phase change is given for each wavelength, and as a result, the optical system The apparent optical path length is changed by changing the group velocity of the light inside. FIG. F. Kwo
The optical path length variable optical system such as ng is coupled to a single mode optical fiber so as to be easily used for an endoscope. K. F. In an optical system such as Kwong, a diffraction grating 10
Is preferably parallel light, but the light emitted from the single mode optical fiber 2 generally has a spread. Therefore, in this optical system, the diffraction grating 1
A collimator lens 7 is provided between the single mode optical fiber 2 for irradiating parallel light to zero and the diffraction grating 10 to make the light from the single mode optical fiber substantially parallel. The Fourier transform lens is indicated by reference numeral 11 and the galvanomirror is indicated by reference numeral 12.

[0007]

Conventionally, OCT has been used for observing relatively slow-moving objects such as retinal tomographic diagnosis and excised specimens. Recently, however, OCT has been performed using an endoscope. There is an increasing need to diagnose the progress of cancer by directly viewing the tomographic images of the stomach and intestine of the living body with moving images.
There is a need for an optical path length variable optical system that is very fast and has a relatively wide scan range.

In the conventional example in which the mirror is driven in the optical axis direction, a relatively wide range can be scanned when scanning at a low speed, but the effect of the inertia of the mirror increases when scanning at a high speed. There is a problem that the scanning range cannot be widened.

In a conventional example using a galvanometer mirror, even if the tilt angle of the galvanometer mirror is small, a large scan width of the optical path length can be obtained, so that high-speed scanning is possible. However, when this type of variable optical path length optical system, the single mode optical fiber 2 and the collimator lens 7 are coupled as shown in FIG. 21, the inclination of the galvanometer mirror 12 is changed from the solid line state to the dotted line state. Then, the light returning to the single mode optical fiber 2 also changes from a solid line to a dotted line.
Since the incident angle changes, the intensity of light after passing through the single mode optical fiber 2 changes. Further, the characteristics of the galvanomirror 12 tend to change depending on the temperature, so that there is a disadvantage that the scan range is likely to shift with time.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object a variable optical path length optical system which has a high speed, a wide scanning range, a small change in light intensity, and a stable temperature characteristic. The purpose is to obtain a moving image of a good tomography such as the esophagus, stomach, and intestine.

[0011]

An optical tomography diagnostic apparatus according to the present invention for achieving the above object divides low coherence light emitted from a light source having a short coherence length into a signal light side and a reference light side, and separates the signal light. After irradiating the observation object, the signal light is combined with the reference light again to form an interference system, and when an interference signal is taken, an optical path length variable optical system is provided on the reference light side or the signal light side to change the optical path length In the optical diagnostic apparatus, which is capable of observing the tomographic structure of the observation object by causing the optical path length variable optical system to include a single mode optical fiber for guiding light to the variable optical path length optical system and a single mode optical fiber for introducing the same, A collimator lens for collimating the light from the mode optical fiber, a condensing lens for collecting substantially parallel light, and a single-mode optical fiber for extracting light It is constituted by optical elements having planes parallel to each other, and light passing through the optical path length variable optical system is configured to pass at least several times through the optical element having planes parallel to each other, and By rotating the optical element having planes parallel to each other, the optical system is configured to change the optical path length between the introduction single mode optical fiber and the takeout single mode optical fiber. It is a feature.

In this case, the variable optical path length optical system is composed of a single-mode optical fiber that combines an introduction single-mode optical fiber and an extraction single-mode optical fiber, and a positive lens that also functions as a collimator lens and a condensing lens. An optical element that has a flat surface and an optical element that reflects light in the direction in which it came from is rotated in order. An optical system that changes the optical path length before returning to the optical fiber can be provided.

Further, the variable optical path length optical system includes an introduction single mode optical fiber for guiding light to the variable optical path length optical system, a collimator lens, at least one group of variable optical path length optical elements, and a condenser lens. , Consisting of a single-mode optical fiber for taking out light,
The optical path length variable optical element group includes a first optical element having surfaces parallel to each other.
And a second optical element made of a member having surfaces parallel to each other and having the same refractive index as the first optical element and having the same surface interval between the parallel surfaces, By rotating the parallel surface of the first optical element and the parallel surface of the second optical element in the optical path length variable optical element group at the same angle in opposite directions to each other, the single-mode optical fiber for introduction and the optical fiber for extraction are rotated. An optical system that changes the optical path length between the single mode optical fibers can be provided.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the principle of variable optical path length in the present invention will be described: As shown in FIG. 1, parallel light is emitted perpendicularly from a plane A, and has a refractive index n and a thickness d. Consider what reaches a plane B that passes through the glass 21 and is parallel to the plane A. The parallel flat glass 21 rotates about a straight line parallel to the X-axis direction as an axis. However, the direction of the light emitted from the plane A is the Z axis, and the directions perpendicular to the Z axis are the X axis and the Y axis.

The inclination of the normal of the parallel plate glass 21 with respect to the Z axis is simply referred to as the inclination of the parallel plate 21. When the inclination of the parallel flat plate 21 is 0, the light goes straight without being refracted as shown in FIG. 1, but when the parallel flat plate 21 is tilted, the light is emitted from the incident surface of the parallel flat glass 21 as shown in FIG. Refracted at the surface. At this time, since the entrance surface and the exit surface of the glass 21 are parallel to each other, the light before entering the glass 21 and the light after exiting from the glass 21 are displaced in the Y-axis direction. Has become.

When the inclination of the parallel flat glass 21 is 0, the optical path length L until the light emitted from the plane A reaches the plane B
The optical path length L (θ) of the optical path from the plane A to the plane B when the inclination of the parallel flat glass 21 is θ with reference to (0).
Has the following relationship:

L (θ) = L (0) + d {1-n-cos θ + (n ² −sin ² θ) ^1/2 } (1) Therefore, the parallel rays and the normal of the parallel flat glass 21 are The optical path length difference ΔL when the angle is 0 and when the angle is θ is as follows: ΔL = L (θ) −L (0) = d {1−n−cos θ + (n ² −sin ² θ) ^1/2 } (2)

The amount of shift ΔY in the Y-axis direction after passing through the parallel plate glass with respect to the light beam before passing through the parallel plate glass 21.
Is given by ΔY = d · sin θ {1-cos θ / (n ² −sin ² θ) ^1/2 } (3)

As described above, the optical path length can be changed by changing the inclination of the parallel flat glass 21 with respect to the light beam. However, when only one parallel flat glass 21 is used, the Y-axis direction can be changed. The light beam shifts in the direction (referred to as Y-direction shift). However, the shift of the light beam in the Y direction can be canceled by passing the light even number of times through a parallel plate having the same refractive index and thickness.

FIG. 3 specifically shows the configuration of this method. The terms A emitted parallel light in a direction perpendicular, parallel light emitted passes through the first parallel flat glass 21 _1, the second parallel flat glass _212, so as to reach the plane B. The first parallel flat glass 21 ₁ and the second parallel flat glass 21 ₂ have the same refractive index and the same thickness, and the first parallel flat glass 21 ₁ and the second parallel flat glass 21 ₂ are in phase and opposite to each other. It is inclined or rotated in the direction. That is, the first parallel flat glass 21 ₁
There when tilted θ with respect to the incident light, leave the second parallel flat glass 21 ₂ as inclined - [theta]. If you leave this way, the light is ΔY shifted to the first pass after the Y-axis direction of the parallel plate glass 21 _1, this time by passing through the second parallel flat plate glass 21 ₂ -DerutaY shifted in the Y-axis direction So that
The difference between the height of the light before entering the first parallel flat glass 21 ₁ and the light after passing through the second parallel flat glass 21 ₂ depends on the inclination of the parallel flat glass 21 ₁ , 21 _2. Always 0.

At this time, since light passes through the parallel plate glass twice, the parallel plate glass 2 having a thickness d and a refractive index n is used.
When the inclination of 11 ₁ and 21 ₂ is 0 and θ (in this case, the inclination of the first parallel flat glass 21 ₁ is θ and the second parallel flat glass 2
1 ₂ of the slope has become -θ. ), The optical path length difference Δ
L is as follows: ΔL = 2d {1−n−cos θ + (n ² −sin ² θ) ^1/2 } (4)

Here, the light passes through the parallel plate glass only twice, but if such optical systems are connected in series so that the light passes through the parallel plate even number of times, the Y
No direction shift is required.

In addition, it is convenient to use a single mode optical fiber to introduce light into the variable optical path length optical system and to take out light from the variable optical path length optical system, and it is hard to be affected by turbulence in the air. In an endoscope, a single mode optical fiber is used to introduce light into and out of the variable optical path length optical system.

When a single mode optical fiber is used for introducing the variable optical path length optical system and taking out the variable optical path length optical system, a collimator lens having a positive power to collimate the light from the single mode optical fiber for introduction is used.
In order to couple the collimated light into a single-mode optical fiber for extraction, a condenser lens having a positive power is used.

The present invention is based on the above principle. By adopting such a configuration, the optical path length can be increased without changing the position and angle of light incident on the single-mode optical fiber for extraction. Since it can be changed, an extremely stable optical path length variable optical system can be configured. In addition, the parallel flat glass can be rotated at high speed by rotating the parallel flat glass so that the inertia axis of the parallel flat glass coincides with the rotation axis, so that the tomographic structure inside the living body can be observed with a moving image. Become.

[0026]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
8 will be described: [Embodiment 1] FIGS. 4 and 5 are diagrams showing a first embodiment of the optical tomography diagnostic apparatus and the optical path length variable optical system according to the present invention.
FIG. 4 shows a system of the optical tomography diagnostic apparatus, and FIG. 5 shows a part of an optical path length variable optical system in the optical tomographic diagnostic apparatus. The system of the optical tomography diagnostic apparatus according to the present embodiment is based on a Michelson interference system.

[0027] In this embodiment, light emitted from the low coherence light source 1 passes through the optical circulator 22 through the first single-mode optical fiber 2 _1, it is led further to the second single mode optical fibers 2 ₂ through a coupler 3. The light is split by the coupler 3 into a signal light side and a reference light side.

The light of the signal light side is irradiated to the measurement object O through the signal light side tip optical system 5 in the third single mode optical fiber 2 _3, light returning from the measurement object O is again the signal light side tip optical system 5 , I come back to the coupler 3 through the third single-mode optical fiber 2 _3.

On the other hand, the light of the reference light side, separated by the coupler 3 is guided to the optical path length varying optical system 24 in the fourth single-mode optical fiber 2 _4. The light path length has been varied by the optical path length varying optical system 24 will come back to the coupler 3 through a fourth single-mode optical fiber 2 ₄ of the same reference light side again.

The light returned from the signal light side and the light returned from the reference light side are combined by the coupler 3. Interference signal synthesized by the coupler 3 is divided into and the optical circulator 22 side second single mode optical fibers 2 ₂ of the first detector 6 ₁ side fifth single mode fiber 2 _5.

The interference light toward the first detector ₆₁ side fifth single mode fiber 2 ₅ of the first detector 6 via the fifth single mode fiber 2 _{5 1}
The light intensity is detected. On the other hand, the second single-mode optical fibers of the optical circulator 22 side 2 ₂
The light headed toward the optical circulator 22
In selectively guided by the second detector 6 ₂ side sixth single-mode optical fiber 2 to _6, the second detector 6 ₂
The light intensity is detected.

The first detector ₆₁ and second detector 6 ₂ has a differential detector, only the component of the interference signal is output, the components other than it is removed.

As shown in FIG. 5, the variable optical path length optical system 24 is a single-mode optical fiber (fourth single-mode optical fiber) 2 having both a single-mode optical fiber for introduction and a single-mode optical fiber for extraction.
₄ , a positive lens 25 which also serves as a collimator lens and a condenser lens, a parallel flat glass 21 which is an optical element having surfaces parallel to each other, and a plane mirror which is an optical element that reflects light in the original direction. is configured in the order of 26, the light emitted from the single mode optical fiber 2 ₄ is approximately parallel with the positive lens 25, passes through a parallel plate glass 21,
Is reflected by the plane mirror 26, passes through the parallel flat glass 21 again, further passes through the positive lens 25, to return to the single-mode optical fiber 2 _4, combined optical axis of the single-mode optical fiber 2 ₄ a positive lens 25 and the plane mirror 26 Have been. Further, the parallel plate glass 21 be adapted to rotate in the axial direction perpendicular to the optical axis, whereby the optical path length until the light emitted from the single mode optical fiber 2 ₄ returns to its single-mode optical fiber 2 ₄ again To change.

In the configuration of this embodiment, light is emitted from the parallel flat glass 2.
Since 1 passes through an even number of times, it does not change position by rotation of the optical parallel plate glass 21 to return to the single-mode optical fiber 2 _4.

The difference ΔL between the optical path length when the normal of the parallel plane of the parallel flat glass 21 to the optical axis is 0 and the optical path length when θ is: ΔL = 2d ｛1−n−cos θ + (n ² −sin ² θ) ^1/2・ ・ ・ (5) Here, n and d are parallel plate glass 21 respectively.
, And the thickness of the parallel flat glass 21.

In the configuration of the present embodiment, when the parallel flat glass 21 is rotated at a period T, the optical path length difference ΔL at time t is obtained.
(T) is as follows: ΔL (t) = 2d [1-n− | cos (2πt / T + φ) | + {n ² −sin ² (2πt / T + φ)} ^1/2 ] (6) Here, φ is the parallel flat glass 2 at t = 0.
It is an inclination of 1. The dotted line in FIG. 6 indicates a refractive index of 1.5 and a thickness of 1.
FIG. 7 is a diagram showing a time change of an optical path length when a zero parallel plate glass 21 is rotated at a period T. Actually, when the angle of the parallel flat glass 21 increases, the parallel flat glass 21
Since the size of the light path is finite, there is a time when the light ray is vignetted and the light does not pass through, so that the optical path length difference behaves like a solid line.

[Embodiment 2] FIG. 7 is a view showing an optical path length variable optical system of Embodiment 2. The second embodiment differs from the first embodiment only in the portion of the variable optical path length optical system 24 of the first embodiment, and other portions not shown are the same as the first embodiment including the interferometer.

In this embodiment, the glass plate 27 having a square cross section is used instead of the parallel plate glass 21 of the variable optical path length optical system 24 of the first embodiment. Further, a dotted line A in FIG.
5 shows the time lapse of the optical path length difference when the glass block 27 having a thickness of 10 (the length of one side of the cross section of the square) rotates at a period T.

When a glass block 27 having a square cross section is used as in the present embodiment, the time during which light does not pass through due to vignetting can be shortened. That is, in the first embodiment, when the inclination angle of the parallel flat glass 21 is around 90 °, the light is scattered on the side surface of the parallel flat glass 21,
There is a long time when light cannot pass. On the other hand, in the present embodiment, as shown in FIG. 7A, the glass block 27 rotates from the state where light first passes through the surface a and the surface c of the glass block 27, and the surface a and the surface c are changed. Even if it does not pass, as shown in FIG. 7 (b), light passes between the surface b and the surface d, so that light always passes except for a moment when the vertex of the glass block 27 cuts off the luminous flux. State. Further, in the first embodiment, the scanning can be performed only two reciprocations during each rotation of the parallel flat glass 21. On the other hand, in the present embodiment, there is an advantage that the number of times of the scanning can be increased to four reciprocations. In this embodiment, the cross-sectional shape of the glass block 27 is square, but if the cross-sectional shape is a polygonal shape such as a regular hexagon or a regular octagon,
The scanning cycle of the optical path length can be shortened without increasing the rotation speed of the glass block.

Embodiment 3 Embodiment 3 is different from Embodiment 2 only in that the portion of the optical path length variable optical system of Embodiment 2 is changed, and other portions not shown are the same as Embodiment 2 including the interferometer. is there.

FIG. 9 is a diagram showing the optical path length varying optical system of Example 3, when the optical axis of the single-mode optical fiber 2 ₄ and Z axis, FIG. 3 (a) optical path length varying optical system of this example 3 is a diagram viewed from the Y-axis direction, and FIG. 3B is a diagram viewed from the X-axis direction.

The optical path length varying optical system of this embodiment, single-mode optical fiber (fourth single mode fiber) for single-mode optical fiber of a single mode optical fiber and for dispensing introduced is shared with 2 _4, a collimator lens and a condenser lens A positive lens 25 also used as
A glass block 27 which is an optical element having planes parallel to each other and has a square cross section; a roof mirror 28 which is an optical path deflecting element for shifting the position of incident light and emitting the light in the opposite direction; And a plane mirror 26, which is an optical element that reflects light in the incoming direction.

The shape of the roof mirror 28 is such that the two reflecting surfaces are at right angles to each other, and the light incident on the roof mirror 28 is shifted in the X direction and emitted in the opposite direction.

The behavior of light in this embodiment is as follows.
You. Single mode optical fiber 2 _FourLight emitted from
Is made substantially parallel by the positive lens 25,
7 and then travel in the -Z direction with the roof mirror 28
At the same time, a shift in the X-axis direction is also received.
The light exiting the Dach mirror 28 is again the same glass block as before
27, and reaches a plane mirror 26. Flat mirror 2
The light that reaches 6 is reflected in the opposite direction,
Proceed in the opposite direction and finally the single mode optical fiber 2
_FourThe light returns to The original route is a gala
Sub-block 27, Dach mirror 28, Glass block 2
7. Single mode optical fiber through positive lens 25
2_FourThe route to return to.

The optical path length changes as the glass block 27 rotates around a straight line parallel to the X axis. In this embodiment, since the light passes through an even number of times the glass block 27 having a parallel plane, the light returning to the single-mode optical fiber 2 _4, glass blocks 2
It is possible to prevent the position from moving even if the 7 rotates. In Example 2, a glass block 27 which has the effect of changing the optical path length between the light comes back after being emitted from the single mode optical fiber 2 ₄ whereas through twice, in the present embodiment, the light Is a glass block 2
7, the light path length difference is twice as large as that of the second embodiment when the glass block 27 having the same refractive index and the same size as that of the second embodiment is used.

A solid line B in FIG. 8 indicates a case where the glass block 27 having a refractive index of 1.5 and a thickness (length of one side of a cross section square) of 10 is rotating at a period T in the configuration of this embodiment. 3 shows the time lapse of the optical path length difference. Example 2 Optical path length difference
It can be seen that it is twice as large.

As in the present embodiment, by using an optical path deflecting element such as the roof mirror 28 to pass light a plurality of times through an optical element having a parallel surface, the scanning width of the optical path length can be increased. can do.

In this embodiment, the roof mirror 28 is used as the optical path deflecting element. However, the optical path deflecting element may be a prism or the like which can shift the position of the incident light and change the direction of the incident light in the opposite direction. Others may be used.

[Embodiment 4] FIGS. 10 and 11 show a fourth embodiment of the optical tomography diagnostic apparatus and the optical path length variable optical system of the present invention. FIG. 10 shows a system of the optical tomography diagnostic apparatus, and FIG. 11 shows a part of an optical path length variable optical system in the optical tomographic diagnostic apparatus. The system of the optical tomography diagnostic apparatus according to the present embodiment is based on a Mach-Zehnder type interference system.

In this embodiment, a low coherence light source
The light exiting from the first single mode optical fiber 2₁
Through the first coupler 3₁Led to. 1st coupler
-3 ₁The light is divided into a signal light side and a reference light side.

The light of the signal light side optical through the second single-mode optical fiber 2 ₂ circulator 22
After passing through the third single mode optical fiber 2
_{3. The} measurement object O is irradiated through the signal light side tip optical system 5. Light returning from the measurement object O is the signal light side tip optical system 5 again, the third through the single-mode optical fiber 2 ₃ returning to the optical circulator 22. Light Optical circulator 22 to back coming signal light side is selectively directed to the fourth direction of the single-mode optical fiber 2 ₄ which is connected to the second coupler 3 _2.

[0052] On the other hand, the light of the first coupler 3 ₁ reference light side, separated by the fifth for introduction into the optical path length varying optical system 24
The light is guided to the optical path length variable optical system 24 by the single mode optical fiber ₂₅ . The light entering the optical path length varying optical system 24 after the optical path length has been varied, taken up by the sixth single-mode optical fiber 2 ₆ for taking out,
It led to the second coupler 3 _2.

[0053] The light guided light guided from the signal light side from the reference light side are combined by the second coupler 3 _2, the interference signal is output from the second coupler 3 _2. 2nd coupler 3
Interference signal synthesized by _2, the first detector ₆₁ and second detector 6 ₂ respectively 7 is guided in the eighth single mode optical fiber 2 _7, 2 _8. Detection occurs in the intensity of the first detector ₆₁ and the second respectively the detector 6 ₂ light. The first detector ₆₁ and second detector 6 ₂ has a differential detector, only the component of the interference signal is output, the components other than it is removed.

As shown in FIG. 11, the variable optical path length optical system 24 has an introduction single mode optical fiber ₂₅ for guiding light to the optical system and a collimator for light from the introduction single mode optical fiber ₂₅ . A collimator lens 29, a variable optical path length optical element group 30, a condensing lens 31 for condensing parallel light, and a single-mode optical fiber ₂₆ for extracting light are arranged in this order.

In this optical system, the light emitted from the introduction single-mode optical fiber ₂₅ passes through the collimator lens 29, the optical path length variable optical element group 30, and the condenser lens 31, and passes to the extraction glue mode fiber ₂₆ . The optical axes of the introduction single-mode optical fiber ₂₅ , the collimator lens 29, the condenser lens 31, and the take-out single-mode optical fiber ₂₆ are aligned so as to be incident. The variable optical path length optical element group 30 includes two glass blocks 27 ₁ , 2 having exactly the same refractive index and shape.
It is composed of 7 _2. Glass blocks 27 ₁ , 27 ₂
Uses a cross section having two sets of planes parallel to each other and a square cross section.

The two glass blocks 27 ₁ and 27 ₂ of the variable optical path length optical element group 30 have a mechanism in which parallel surfaces rotate at the same angle in directions opposite to each other. _The light collecting position is not shifted at the position ₆ , and the single-mode optical fiber 2 ₅ for introduction and the single-mode optical fiber 2 for extraction
The optical path length between ₅ is changed.

In this embodiment, the glass blocks 27 ₁ , 2
7 the difference [Delta] L in optical path length when the optical path length and theta when the angle is 0 relative to the normal of the optical axes of the _two mutually parallel planes, ΔL = 2d {1-n -cosθ + (n 2 -sin 2 θ ) ^1/2 ｝ (-45 ° <θ <45 °) (7) Here, n and d are glass blocks 27, respectively.
₁ and 27 ₂ , and the thickness of the square cross section of the glass blocks 27 ₁ and 27 ₂ . A dotted line A in FIG. 12 is a glass block 2 having a refractive index of 1.8, a square cross section, and a thickness of 10.
7 shows a temporal change of the optical path length when 7 ₁ and 27 ₂ are rotated at a period T.

[Embodiment 5] FIG. 13 differs from Embodiment 4 in that only the portion of the optical path length variable optical system of Embodiment 4 is changed, and the other portions not shown are the same as Embodiment 4 including the interferometer portion. . The optical axes of the single mode optical fibers 2 ₅ and 2 ₆ are Z
13 (a) is a diagram viewed from the Y-axis direction, and FIG.
FIG. 3B shows the optical path length variable optical system viewed from the X-axis direction.

The variable optical path length optical system according to the present embodiment transmits light from the first coupler 3 ₁ (FIG. 10) to the variable optical path length optical system 24.
And introducing the single-mode optical fiber 2 ₅ leading to a first 1GRIN lens (gradient index lens) 32 ₁ as a collimator lens, a glass block cross-sectional shape is an optical element having a plane parallel to each other has a square 27
When an optical path deflecting prism 33 is an optical path deflecting element to be emitted in opposite directions by shifting the position of the light that has entered, and the 2GRIN lens 32 ₂ as the condensing lens, single-mode optical fiber 2 for taking out for taking out the light ₆
It is composed of The glass block 27 rotates around a straight line parallel to the X axis.

The cross-sectional shape of the optical path deflecting prism 33 on the XZ plane is a right-angled isosceles triangle, and light incident on this prism is shifted in the X direction and emitted in the opposite direction. .

The behavior of light in this embodiment is as follows. The light emitted from the introduction for single mode optical fiber 2 ₅ which is in the 1GRIN lens 32 ₁ substantially parallel,
After passing through the glass block 27, the optical path deflecting prism 3
3, the traveling direction can be changed in the -Z direction, and at the same time, a shift in the X-axis direction is also received.

The light exiting the optical path deflecting prism 33 passes through the same glass block 27 as before, is condensed by the _second GRIN lens 322, and is taken into the take-out single mode optical fiber ₂₆ .

The optical path length changes as the glass block 27 rotates around a straight line parallel to the X axis. In this embodiment, since the light passes through the glass block 27 having a parallel surface even number of times, the light condensing position is shifted even if the glass block 27 rotates at the position of the single-mode optical fiber ₂₆ for extraction. It is possible not to be.

In the present embodiment, only one glass block 27 is used, and there is no need to rotate the two glass blocks 27 ₁ and 27 ₂ in the opposite directions with the same phase as in the fourth embodiment. There is an advantage that control of the rotation mechanism is simplified.

In this embodiment, light passes twice through the glass block 27 having the function of changing the optical path length. The number of times light passes through the glass block 27 is the same as in the fourth embodiment. Therefore, the glass block 2 used in this embodiment is
When a glass block having the same refractive index and the same size as that of the fourth embodiment is used, the optical path length difference becomes the same as that of the fourth embodiment.

The collimator lens and the condensing lens used in this embodiment may be ordinary positive lenses instead of the GRIN lenses 32 ₁ and 32 _{2. The} GRIN lens is, for example, SELFOC (a product of Nippon Sheet Glass Co., Ltd.). Since optical fibers having relatively small diameters, such as (name), are produced, the use of such materials can make the optical system more compact. In addition, although the prism 33 whose cross-sectional shape is a right-angled isosceles triangle is used as the optical path deflecting element, the optical path deflecting element is shifted in position of incident light, such as a roof mirror, and
Anything can be used as long as the direction is changed to the opposite direction and ejected.

[Embodiment 6] FIG. 14 shows a fifth embodiment in which only the variable optical path length optical system of the fifth embodiment is changed, and the other portions (not shown) are the same as the fifth embodiment including the interferometer. . The optical axes of the single mode optical fibers 2 ₅ and 2 ₆ are Z
14A is a diagram viewed from the Y-axis direction, FIG.
FIG. 4B shows the optical path length variable optical system viewed from the X-axis direction.

The variable optical path length optical system according to the present embodiment uses the light from the first coupler 3 ₁ (FIG. 10) to change the optical path length variable optical system 24.
In the introduction for single mode optical fiber 2 ₅ for guiding a first 1GRIN lens 32 ₁ as a collimator lens, the light which has been cross-sectional shape between the glass block 27 which is square, the incident is an optical element having a plane parallel to each other Are shifted from each other, and the first to third optical path deflecting prisms 33 ₁ , 3 are three optical path deflecting elements for emitting light in opposite directions.
3 _2, 33 _3, and the 2GRIN lens 32 ₂ as the condenser lens, and a single-mode optical fiber 2 ₆ for taking out for taking out the light. The glass block 27 rotates around a straight line parallel to the X axis.

First to third optical path deflecting prisms 33 ₁ , 33
_2, 33 ₃ in the XZ plane cross-sectional shape, both are at right angles isosceles triangle, light incident on these prisms are shifted in the X direction, and is emitted orientation is changed in the opposite direction .

The behavior of light in this embodiment is as follows.
You. Single mode optical fiber 2 for introduction_FiveEjected from
The reflected light is the first GRIN lens 32₁After being made almost parallel,
After passing through the glass block 27, the first optical path deflection prism
33₁At the same time as changing the traveling direction to -Z direction.
It is shifted in the X-axis direction. First optical path deflection prism 33 ₁
Light passed through the same glass block 27 as before again
Then, the second optical path deflection prism 33_TwoTo move in the Z direction
It is shifted in the X-axis direction at the same time as being changed. Second light
Path deflection prism 33_TwoThe light that came out is again the same glass as before
After passing through the block 27, the third optical path deflecting prism 33_Three
To change the traveling direction again to the -Z direction and at the same time the X axis
After receiving a shift in direction, again the same glass block as before
Go through 27. And finally, the second GRIN lens 32
_TwoSingle mode optical fiber for focusing
ー 2₆It is taken in.

The optical path length changes as the glass block 27 rotates around a straight line parallel to the X axis.

Further, in this embodiment, since the light passes through the glass block 27 having a parallel surface even number of times, even if the glass block 27 rotates, the light on the take-out single mode optical fiber ₂₆ is not changed. It is possible to keep the focusing position from moving.

Further, in the fourth or fifth embodiment, the glass block 27 having the function of changing the optical path length while the light exits from the single mode optical fiber and returns.
In the present embodiment, the light passes through the glass block 27 four times, whereas in the present embodiment, the light path length is equal to that of the fourth or fifth embodiment using the same refractive index and the same size glass block. The difference is twice the value of Example 4 or 5.

As described above, the optical path deflecting optical systems 33 ₁ , 3
3 with _2, 33 _3, without increasing the size of the glass block 27 by passing a plurality of times light in the glass block 27, it is possible to increase the scanning range of the optical path length.

A solid line B in FIG. 12 indicates a case where the glass block 27 having a refractive index of 1.8 and a thickness (length of one side of a cross section square) of 10 is rotating at a period T in the configuration of this embodiment. 3 shows the time lapse of the optical path length difference. It can be seen that the optical path length difference is twice the value of Example 4 or 5.

In this embodiment, as the optical path deflecting element, prisms 33 ₁ , 33 ₂ , each having a right-angled isosceles triangle in cross section,
33 ₃ While using the optical path deflecting element, for example the roof mirrors and the like, it is shifted positions of the incident light, and may be any ones which orientation is emitted is changed in the opposite direction.

[Embodiment 7] FIG. 15 differs from Embodiment 6 in that only the portion of the optical path length variable optical system of Embodiment 6 is changed, and the other portions (not shown) are the same as Embodiment 6 including the interferometer. . The optical axes of the single mode optical fibers 2 ₅ and 2 ₆ are Z
15A is a diagram viewed from the Y-axis direction, and FIG.
FIG. 5B shows the optical path length variable optical system viewed from the X-axis direction.

[0078] the optical path length varying optical system of this embodiment, first coupler 3 ₁ the optical path length of light from (10) adjustable optical system 24
And introducing the single-mode optical fiber 2 ₅ leading to a first 1GRIN lens 32 ₁ as a collimator lens, and the 2GRIN lens 32 ₂ as the condensing lens, single-mode optical fiber 2 for taking out for taking out the light
₆ , an optical path length variable optical element group 30 composed of _two glass blocks 27 ₁ and 27 ₂ , and an optical path deflecting element 35 that shifts the position of incident light and emits it in the opposite direction.

The variable optical path length optical element group 30 includes a first optical
First glass block 27 as an element ₁And the second optical element
The second glass block 27 which is a child_TwoIt is composed of
First glass block 27₁And the second glass block 27_Two
Indicates that both the cross-sectional shapes of the XZ plane are square, and the refractive index is
And the shape is the same.

The two glass blocks 27 ₁ and 27 ₂ of the variable optical path length optical element group 30 have a mechanism in which parallel surfaces rotate in opposite directions at the same angle.

The configuration of the optical path deflecting element 35 is such that the optical path deflecting single mode optical fiber 34 and the third GRIN lens 32 as a light path deflecting element condensing lens for condensing the light on the optical path deflecting single mode optical fiber 34.
₃ and a _fourth GRIN lens 324 as a collimator lens for an optical path deflecting element for making the light emitted from the optical path deflecting single mode optical fiber 34 substantially parallel. Further, since the incident side end face and the exit side end face of the optical path deflecting single mode optical fiber 34 are arranged in parallel in the X direction in the same direction, the optical path deflecting element 35 enters the single mode optical fiber 34 for the optical path deflecting element. It has the effect of shifting light in the X direction and changing its direction to the opposite direction and emitting it.

The behavior of light in this embodiment is as follows. The light emitted from the introduction for single mode optical fiber 2 ₅ which is substantially parallel with the 1GRIN lens 32 _1, passes through the optical path length varying element group 30, can change the direction of travel in the -Z direction in the subsequent optical path deflecting element 35 At the same time as the shift in the X-axis direction. The light exiting the optical path deflecting element 35 again passes through the same optical path length variable element group 30 as before, and then the second GR
Is condensed with IN lens 32 _2, it is incorporated into the single-mode optical fiber 2 ₆ for taking out.

The change in the optical path length is determined by the optical path length variable optical element group 3
The two glass blocks 27 ₁ and 27 ₂ are rotated at the same angle in opposite directions, but the light emitted from the introduction single mode optical fiber ₂₅ is incident on the entrance end face of the optical path deflected single mode optical fiber 34. And when the end of the single-mode optical fiber ₂₆ for taking out is reached, the glass block 2
Since the light passes through the even number of times 7 ₁ and 27 ₂ , the light condensing position does not change even if the glass blocks 27 ₁ and 27 ₂ rotate.

In the configuration of this embodiment, the time of the optical path length difference when a glass block having a refractive index of 1.8 and a thickness (length of one side of a cross section of a square) of 10 is rotated at a rotation period of T. The progress is the same as that of the sixth embodiment since the number of times that light passes through the glass block is four times.

In this embodiment, as in the sixth embodiment, the light is passed through the same glass blocks 27 ₁ and 27 ₂ a plurality of times, so that the scanning width of the optical path length can be increased. Further, by using the GRIN lenses 32 _{1 to} 32 ₄ , it is possible to make the optical system compact.

[0086] In this embodiment, the 4GRIN lens 3 is a first 3GRIN lens 32 ₃ and the optical path deflecting element collimator lens is a condenser lens of the optical path deflecting element 35
₂₄ is on the same side as the optical path length variable element group 30,
As shown in FIG. 16, the incident side of the optical path deflecting single mode optical fiber 34 of the optical path deflecting element 35 and the third GRIN lens 32 which is a condenser lens of the optical path deflecting element 35.
₃ and the fourth side as the exit side of the optical path deflecting single mode optical fiber 34 and the collimator lens for the optical path deflecting element.
And a GRIN lens 32 _4, be arranged on opposite sides of the optical path length varying element group 30, the same effect as in the case of FIG. 15 is obtained.

[Embodiment 8] FIG. 17 differs from Embodiment 6 in that only the portion of the optical path length variable optical system of Embodiment 6 is changed, and other portions not shown are the same as Embodiment 6 including the interferometer. . The optical axes of the single mode optical fibers 2 ₅ and 2 ₆ are Z
17 (a) is a view from the Y-axis direction, and FIG.
FIG. 7B shows the optical path length variable optical system viewed from the X-axis direction.

The variable optical path length optical system according to the present embodiment transmits light from the first coupler 3 ₁ (FIG. 10) to the variable optical path length optical system 24.
And introducing the single-mode optical fiber 2 ₅ leading to a first 1GRIN lens 32 ₁ as a collimator lens, and the 2GRIN lens 32 ₂ as the condensing lens, single-mode optical fiber 2 for taking out for taking out the light
₆ , a variable optical path length optical element group 30 composed of _two glass blocks 27 ₁ and 27 ₂ , and first and second optical path deflecting elements 35 ₁ and 35 ₂ for shifting the position of incident light and emitting the light in opposite directions. It is composed of

The optical path length variable optical element group 30 includes a first optical
First glass block 27 as an element ₁And the second optical element
The second glass block 27 which is a child_TwoIt is composed of
First glass block 27₁And the second glass block 27_Two
Has a regular hexagonal cross section on the XZ plane, and is refracted.
The rate and shape are the same.

The two glass blocks 27 ₁ and 27 ₂ of the variable optical path length optical element group 30 have a mechanism in which parallel surfaces rotate at the same angle in directions opposite to each other.

[0091] The first optical path deflecting element 35 ₁ of the arrangement, as the optical path deflecting element condenser lens for condensing the first optical path deflecting single-mode optical fibers 34 ₁ first 3GRIN
A lens 32 _3, and a second 4GRIN lens 32 ₄ of the optical path deflecting element collimator lens for substantially parallel light emitted from the first optical path deflecting single-mode optical fibers 34 ₁ thereof. Further, since the arranged in parallel irradiation side and the first optical path incident surface of the deflection for single-mode optical fiber 34 ₁ in the X direction in the same direction, the first optical path deflecting element 35 ₁ is single mode for the optical path deflecting element the light incident on the optical fiber 34 ₁ is shifted in the X direction, and has the effect of orientation is emitted instead in the opposite direction.

[0092] Also, the second optical path deflecting element 35 ₂ structure,
The 5G as an optical path deflecting element condenser lens for condensing the second optical path deflecting single-mode optical fiber 34 ₂
And RIN lens 32 _5, first as an optical path deflecting element collimator lens for substantially parallel light emitted from the second optical path deflecting single-mode optical fiber 34 ₂ 6GR
It is composed of a IN lens 32 _6. Further, since the arranged in parallel irradiation side and a second optical path deflecting single-mode optical fiber 34 _{and second} incident surfaces in the X direction in the same direction, the second optical path deflecting element 35 ₂ is single-mode optical path deflecting element the light incident on the optical fiber 34 ₂ is shifted in the X direction, and has the effect of orientation is emitted instead in the opposite direction.

The behavior of light in this embodiment is as follows. The light emitted from the introduction for single mode optical fiber 2 ₅ which is in the 1GRIN lens 32 ₁ substantially parallel,
It passes through the optical path length varying element group 30, as then can change the traveling direction in the -Z direction by the first optical path deflecting element 35 ₁ at the same time X
Axial shift. Light emitted ₁ first optical path deflecting element 35 again after passing through the same optical path length varying element group 30 as before, the same time X-axis direction as can change the traveling direction in the Z direction in the second optical path deflecting element 35 ₂ Will be shifted. After passing through the same variable optical path length optical element group 30 as before, the second GRI
Is condensed with N lens 32 _2, it is incorporated into the single-mode optical fiber 2 ₆ for taking out.

FIG. 18 shows the configuration of the present embodiment.
8 shows the time lapse of the optical path length difference when a glass block having a thickness of 10 (interval between planes parallel to each other) is rotated at a rotation cycle of T.

The change in the optical path length is determined by the optical path length variable optical element group 3
0 is performed by rotating the two glass blocks 27 ₁ and 27 _{2 in} the directions opposite to each other at the same angle, and the light emitted from the introduction single mode optical fiber ₂₅ is deflected by the optical path deflected single mode optical fibers 34 ₁ and 34. when reaching the _second end face (both the incident surface and exit surface), and, when it reaches the end face of the take-out for single mode optical fiber 2 _6, since the glass block 27 _1, 27 ₂ come through an even number of times, the glass blocks 27 ₁ , so that the 27 ₂ condensing position of the light does not change even if the rotation.

In this embodiment, the glass blocks 27 ₁ , 27
_Since the cross-sectional shape of ₂ is a regular hexagon, scanning is performed six times while the glass blocks 27 ₁ and 27 ₂ make one rotation.

Thus, the glass blocks 27 ₁ , 27
Regular hexagon a _second cross-sectional shape from a square, by increasing the number of vertices of a regular octagon and the polygon shape, even a glass block 27 _1, 27 ₂ of the rotational speed are the same, allowing high-speed scanning. However, if we increase the number of vertices of the polygon shape, since the scanning width is reduced, the scanning width by increasing the number of times through the optical path length varying optical element group 30 using many optical path deflecting element 35 _1, 35 ₂ I'm making it big.

In the first to eighth embodiments, the optical elements having at least one set of parallel surfaces are all made of glass. However, for example, an optical plastic or the like that transmits and refracts light is used. Needless to say, the variable optical path length optical system may be provided not only on the reference light side but also on the signal light side.

The above-described optical tomography diagnostic apparatus of the present invention can be configured, for example, as follows: [1] Low-coherence light emitted from a light source having a short coherence length is divided into a signal light side and a reference light side, After irradiating the observation object with the signal light, the signal light is combined with the reference light again to form an interference system. When an interference signal is obtained, an optical path length variable optical system is provided on the reference light side or the signal light side to provide an optical path. In an optical diagnostic apparatus capable of observing a tomographic structure of an observation object by changing a length, the optical path length variable optical system includes an introduction single mode optical fiber for guiding light to the optical path length variable optical system, and Collimator lens for collimating the light from the single-mode optical fiber for introduction, condensing lens for collecting substantially parallel light, and single-mode for extracting light A fiber and an optical element having planes parallel to each other are configured, and light passing through the optical path length variable optical system passes through the optical element having planes parallel to each other at least several times. And an optical system adapted to change the optical path length between the introduction single-mode optical fiber and the take-out single-mode optical fiber by rotating the optical elements having surfaces parallel to each other. An optical tomography diagnostic apparatus, comprising:

[2] The variable optical path length optical system includes a single-mode optical fiber that functions as both the single-mode optical fiber for introduction and the single-mode optical fiber for extraction, and a positive-mode optical fiber that also functions as the collimator lens and the condensing lens. A lens, the optical element having the planes parallel to each other, and the optical element reflecting the light in the original direction are arranged in this order, and the single element is rotated by rotating the optical element having the planes parallel to each other. 2. The optical tomography diagnostic apparatus according to claim 1, wherein the optical system changes an optical path length until light emitted from the mode optical fiber returns to the single mode optical fiber again.

[3] The variable optical path length optical system is a single mode optical fiber which also serves as the single-mode optical fiber for introduction and the single mode optical fiber for take-out, and a positive mode which also serves as the collimator lens and the condensing lens. A lens, an optical element having planes parallel to each other, an optical element for reflecting light in the original direction, and an optical path for shifting at least one incoming light position in a parallel or opposite direction and emitting the light. An optical element comprising a deflecting element and rotating the optical element having surfaces parallel to each other to change an optical path length until light emitted from the single mode optical fiber returns to the single mode optical fiber again. 2. The optical tomography diagnostic apparatus according to the above 1, wherein the apparatus is a system.

[4] The variable optical path length optical system includes an introduction single mode optical fiber for guiding light to the variable optical path length optical system, a collimator lens, at least one group of variable optical path length optical elements, An optical lens and a single-mode optical fiber for extracting light for extracting light are arranged in this order, and the optical path length variable optical element group includes a first optical element having planes parallel to each other and a plane parallel to each other. The first optical element and a second optical element made of a member having the same refractive index and being parallel to each other and having the same surface interval, and the first optical element in the variable optical path length optical element group. By rotating the parallel surface of the first optical element and the parallel surface of the second optical element in the opposite directions at the same angle, the single-mode optical fiber for introduction and the single-mode optical fiber for extraction are rotated. 2. The optical tomography diagnostic apparatus according to the above 1, wherein the optical system is an optical system that changes an optical path length between the divers.

[5] The variable optical path length optical system comprises: an introduction single mode optical fiber for guiding light to the variable optical path length optical system; a collimator lens;
A single-mode optical fiber for taking out light outside the variable optical path length optical system, an optical element having surfaces parallel to each other, and at least one position of incident light is shifted in a parallel direction or an opposite direction. An optical path deflecting element to be emitted, and by rotating the optical element having planes parallel to each other, the optical path length between the introduction single mode optical fiber and the takeout single mode optical fiber is changed. 2. The optical tomography diagnostic apparatus according to the above 1, wherein the apparatus is an optical system.

[6] The variable optical path length optical system includes: an introduction single mode optical fiber for guiding light to the variable optical path length optical system; a collimator lens;
A single-mode optical fiber for taking out light outside the variable optical path length optical system, at least one group of optical elements, and at least one incoming light are shifted in a parallel or opposite direction and emitted. An optical path deflecting element, wherein the optical element group further includes a first optical element having surfaces parallel to each other, and a parallel optical surface having the same refractive index as the first optical element. And a second optical element made of a member having the same surface spacing between the first and second optical elements in the optical element group. The optical system is configured to change the optical path length between the introduction single-mode optical fiber and the take-out single-mode optical fiber by rotating the main surfaces at the same angle in opposite directions. Optical tomographic diagnostic apparatus having the aforementioned 1, wherein Rukoto.

[7] The optical tomography diagnostic apparatus according to the above 3, 5 or 6, wherein the optical path deflecting elements are roof mirrors having surfaces perpendicular to each other.

[8] The optical tomography diagnostic apparatus according to the above 3, 5 or 6, wherein the optical path deflecting element is a right-angle prism.

[0107]

[9] The optical path deflecting element includes a single mode optical fiber for optical path deflection, an optical path deflecting element condensing lens for condensing the light on the single mode optical fiber for optical path deflection, and an emission light from the single mode optical fiber for optical path deflection. 7. The collimator lens for an optical path deflecting element for making the optical path deflecting element substantially parallel, and the incident side end face and the exit side end face of the optical path deflecting single mode optical fiber are configured in parallel. Optical tomography diagnostic device.

[10] The optical tomography diagnostic apparatus according to any one of the above items 1 to 9, wherein the optical elements having mutually parallel surfaces have a polygonal shape.

[0109]

By using the variable optical path length optical system according to the present invention, the optical tomography diagnostic apparatus of the present invention has a high speed, a wide scan range, a small change in light intensity, and a stable temperature characteristic. A variable optical path length optical system can be obtained, and a tomographic image of the esophagus, stomach, intestine, and the like can be observed with a favorable moving image.

[Brief description of the drawings]

FIG. 1 is a first diagram illustrating the principle of an optical path length variable optical system according to the present invention.

FIG. 2 is a second diagram illustrating the principle of the optical path length variable optical system according to the present invention.

FIG. 3 is a diagram showing a specific configuration for canceling a light beam shift.

FIG. 4 is a configuration diagram of an optical tomography diagnostic apparatus according to Embodiment 1 of the present invention.

FIG. 5 is a configuration diagram of an optical path length variable optical system of the optical tomography diagnostic apparatus according to the first embodiment.

FIG. 6 is a diagram illustrating a temporal change of an optical path length according to the first embodiment.

FIG. 7 is a configuration diagram of an optical path length variable optical system of the optical tomography diagnostic apparatus according to the second embodiment.

FIG. 8 is a diagram illustrating a temporal change of an optical path length in Examples 2 and 3.

FIG. 9 is a configuration diagram of an optical path length variable optical system of an optical tomography diagnostic apparatus according to a third embodiment.

FIG. 10 is a configuration diagram of an optical tomography diagnosis apparatus according to a fourth embodiment.

FIG. 11 is a configuration diagram of an optical path length variable optical system of an optical tomography diagnostic apparatus according to a fourth embodiment.

FIG. 12 is a diagram showing a time change of an optical path length in Examples 4 to 7.

FIG. 13 is a configuration diagram of an optical path length variable optical system of an optical tomography diagnostic apparatus according to a fifth embodiment.

FIG. 14 is a configuration diagram of an optical path length variable optical system of an optical tomography diagnostic apparatus according to a sixth embodiment.

FIG. 15 is a configuration diagram of an optical path length variable optical system of an optical tomography diagnostic apparatus according to a seventh embodiment.

FIG. 16 is a configuration diagram of a modification of the optical path length variable optical system of the optical tomography diagnostic apparatus according to the seventh embodiment.

FIG. 17 is a configuration diagram of an optical path length variable optical system of an optical tomography diagnostic apparatus according to an eighth embodiment.

FIG. 18 is a diagram illustrating a temporal change of an optical path length according to an eighth embodiment.

FIG. 19 is a diagram showing a configuration of an example in which a conventional optical tomography diagnostic apparatus is applied to an endoscope.

FIG. 20 is a configuration diagram of an example of a conventional optical path length variable optical system.

FIG. 21 is a configuration diagram of another example of a conventional optical path length variable optical system.

[Explanation of symbols]

O ... measured 1 ... low-coherence light source 2 ₁ to 2 ₈ ... single-mode optical fibers 3,3 _1, 3 ₂ ... coupler 5 ... signal light side front end optics ₆₁ and 62 ₂ ... detector 21 _1, 21 ₂ ... Parallel plate glass 22 Optical circulator 24 Optical path length variable optical system 25 Positive lens 26 Planar mirror 27, 27 ₁ , 27 ₂ Glass block 28 Dach mirror 29 Collimator lens 30 Optical path length variable optical element group 31 the condenser lens 32 ₁ to 32 ₆ ... GRIN lens 33 _1, 33 _2, 33 ₃ ... optical path deflecting prism 34, 34 _1, 34 ₂ ... Single-mode optical fibers 35 and 35 ₁ for the optical path deflecting, 35 ₂ ... optical path deflecting element

Claims (3)

[Claims] 1. A low coherence light emitted from a light source having a short coherence length is divided into a signal light side and a reference light side, and the signal light is irradiated onto an observation object. When taking an interference signal, in the optical diagnostic apparatus that allows to observe the tomographic structure of the observation object by changing the optical path length by providing an optical path length variable optical system on the reference light side or the signal light side, The variable optical path length optical system, an introduction single mode optical fiber for guiding light to the optical path length variable optical system, a collimator lens for collimating the light from the introduction single mode optical fiber, and substantially parallel light. A converging lens for converging light, a single-mode optical fiber for extracting light, and an optical element having surfaces parallel to each other; Light passing through the system, by rotating the optical element having at least said has become the optical element to pass through even-number times with a plane parallel to each other and mutually parallel surfaces of said,
An optical tomography diagnostic apparatus comprising an optical system adapted to change an optical path length between the introduction single mode optical fiber and the takeout single mode optical fiber. 2. The variable optical path length optical system includes: a single mode optical fiber that also serves as the introduction single mode optical fiber and the extraction single mode optical fiber; and a positive lens that also serves as the collimator lens and the condenser lens. And an optical element having a plane parallel to each other, and an optical element reflecting light in the original direction. The single mode is formed by rotating the optical element having a plane parallel to each other. 2. The optical tomography diagnostic apparatus according to claim 1, wherein the optical system is configured to change an optical path length until light emitted from the optical fiber returns to the single mode optical fiber again. 3. The variable optical path length optical system includes: an introduction single mode optical fiber for guiding light to the variable optical path length optical system; a collimator lens; at least one group of variable optical path length optical elements; A lens and a single-mode optical fiber for taking out light for taking out light, wherein the variable optical path length optical element group has a first optical element having surfaces parallel to each other and a surface parallel to each other. A first optical element and a second optical element made of a member having the same refractive index and being parallel to each other and having the same surface interval, wherein the first optical element in the optical path length variable optical element group is Rotating the parallel plane of the optical element and the parallel plane of the second optical element at the same angle in opposite directions to each other, thereby obtaining the single-mode optical fiber for introduction and the single-mode optical fiber for extraction. 2. An optical tomography diagnostic apparatus according to claim 1, wherein the optical system is an optical system that changes an optical path length between the optical paths.