JP2003307487A - Optical scanning probe - Google Patents

Abstract

(57) [Problem] To stabilize an image of an observation object even when the posture of an insertion part of an optical scanning probe is changed during insertion into a body cavity, without a change in the optical path length between the object side and the reference side. An optical scanning probe is provided. SOLUTION: A low-interference light source 11 for generating low-interference light is provided inside a hard distal housing portion 5 at the distal end of a flexible insertion portion 4 inserted into a body cavity of an optical scanning probe 2. A collimator lens 15 for converting the beam into a parallel beam, a beam splitter 16 for splitting the beam into an object-side optical path 31 and a reference-side optical path 32, a two-dimensional scan mirror 22 disposed on the object-side optical path 31 on the transmitted light side, an objective lens 23, The piezo drive mirror 19 and the like of the reference side optical path 32 on the reflected light side of the beam splitter 16 are respectively arranged, and even if the insertion section 4 changes posture such as bending during insertion, the object side optical path 31 and the reference side optical path 32 Thus, an image of the observation target can be stably obtained without any change in both optical path lengths.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning probe for scanning a subject with light having low coherence to obtain image information.

[0002]

2. Description of the Related Art In recent years, when diagnosing a living tissue, an interference type OCT that obtains a tomographic image of a subject using low coherence light
(Optical Coherent Tomography) has been proposed. A conventional example of this interference type OCT (optical coherent tomography) will be described with reference to FIG.
The conventional interference type OCT 60 shown in FIG.
1, the near-infrared low-coherence light emitted from the low-coherence light source 61 is guided to the first optical fiber 62a, and the third optical fiber 62c is coupled by the optical coupler 63 for optical coupling.
To the fourth optical fiber 62d.

The third optical fiber 62c is an optical connector 64.
The low coherence light is transmitted to the optical scanning probe 66 which is connected to the fifth optical fiber 65 and can be inserted into the body cavity.

The low-coherence light emitted from the end of the fifth optical fiber 65 is condensed as an observation beam 67 on the observation object 68 inside the observation object by a condenser lens (not shown).

On the other hand, the fourth optical fiber 62d is connected to the frequency shifter 69, and is guided to the sixth optical fiber 62e via the frequency shifter 69. As the frequency shifter 69, an acousto-optical element (AOM) or an electro-optical element (EO),
Phase modulation means such as a piezoelectric element provided with a fiber loop is used.

The light emitted from the end of the sixth optical fiber 62e is guided to the movable mirror 71 by the lens 70.
The movable mirror 71 is moved in the optical axis direction of the emitted light by the mirror driving means 72. The end portion of the sixth optical fiber 69, the lens 70, the movable mirror 71, and the mirror driving means 72 constitute an optical path length adjusting means 73.

The second optical fiber 62b is the optical detector 7
4 is connected. The near-infrared low interference light emitted from the low coherence light source 61 is guided to the first optical fiber 62a,
The optical coupler 63 splits the optical fiber into a third optical fiber 62c and a fourth optical fiber 62d. Third optical fiber 62
The light guided to c is guided to the optical scanning probe 66 via the optical connector 64 and the fifth optical fiber 65, and is emitted as an observation beam 67 to the observation object 68 side.

The observation beam 67 and the observation point are scanned by a scanner (not shown) with respect to the observation object 68 in a direction indicated by an arrow or the like by a scanning drive signal from the scanning drive means 81. The reflected or scattered light from the observation object 68 side at the observation point returns to the fifth optical fiber 65 via the condenser lens, and the third optical fiber 62c in the reverse optical path.
Return to. This optical path becomes the object-side optical path.

Similarly, the low interference light branched to the fourth optical fiber 62d is subjected to frequency transition by the frequency shifter 69, and the sixth
The light is converted into substantially parallel light by the optical fiber 62e and the lens 70 and is guided to the movable mirror 71. The light reflected by the movable mirror 71 is again reflected by the lens 70 through the sixth optical fiber 62.
It is guided to e and returns to the fourth optical fiber 62d. This optical path is the reference optical path.

The light on the object side optical path and the light on the reference side optical path are optical couplers 6.
In the second optical fiber 62b, when the optical path lengths of the object side optical path and the reference side optical path match in the range of the coherence length of the low coherence light source 61, the frequency caused by the frequency shift amount of the frequency shifter 69 is mixed. The interference light modulated by is detected.

If the mirror driving means 72 adjusts the optical path length on the reference side to the optical path length to the observation point on the object side in advance by the optical path length adjusting means 73, information from the observation point is obtained. Will always be obtained as interference light. When this interference light is converted into an electric signal by the optical detector 74 and only the signal in the vicinity of the modulation frequency is taken out by the demodulator 75, the signal from the observation point can be detected with high S / N by optical heterodyne detection.

This signal is A / S synchronized with the scanning at the observation point.
An image of the observation object 68 can be obtained by capturing the image with the personal computer (hereinafter abbreviated as a personal computer) 77 by the D converter 76 and displaying the demodulated signal on the display 78 with brightness corresponding to the scanning position. The light from an aiming beam laser 79 that generates an aiming beam of visible light is guided to the third optical fiber 62c via a coupler 80.

[0013]

However, according to the above-mentioned conventional example, the optical fiber 65, which is a part of the object side optical path, is inserted into the flexible tube inserted into the body cavity of the optical scanning probe 66. Therefore, the optical fiber 65 having a length of at least several tens of centimeters or more is subjected to tensile or compressive stress by being bent into various shapes when the optical scanning probe 66 is inserted into the body cavity.

The optical characteristics change when the optical fiber 65 receives stress. Furthermore, since the length of the optical fiber 65 is long, the optical path length of the object-side optical path changes unintentionally. As a result, there is a problem that the correct image of the observation target is not displayed.

Further, in the conventional observation apparatus, when the insertion section is exchanged from the main body of the apparatus, if the optical path length at the insertion section greatly changes due to individual differences or types of the insertion section, the optical path of the reference optical path is changed. It was difficult to adjust the length.

(Object of the Invention) The present invention has been made in view of the above problems. Provided is an optical scanning probe which can stably obtain an image of an observation target without any change in the optical path lengths on the object side and the reference side due to a change in the posture, regardless of the posture of the optical scanning probe being inserted into a body cavity. The purpose is to do. Another object of the present invention is to provide an optical scanning probe in which the user does not need to adjust the optical path length on the reference side each time, even when the individual difference or type of the insertion portion changes.

[0017]

An object-side optical path for guiding low-coherence light from a low-coherence light source to an object side for measurement and a reference side inside a hard tip of an insertion portion that can be inserted into a subject. Optical path branching means for branching the optical path to the reference side optical path, and light mixing means for mixing the light from the object side optical path and the reference side optical path and guiding the light to the light detecting means side as interference light. As a result, even if the posture is changed during insertion of the insertion portion into the body cavity, there is no fluctuation in the optical path lengths of the object side optical path and the reference side optical path due to the change in attitude, and a correct observation target image can be stably obtained. I have to.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIGS. 1 and 2 relate to a first embodiment of the present invention, and FIG. 1 shows an overall configuration of an interference type optical imaging apparatus including the first embodiment. 2 is a plan sectional view showing the configuration of the tip side of the optical scanning probe of the first embodiment.

As shown in FIG. 1, an interference type optical imaging apparatus 1 is connected to the optical scanning probe 2 of the first embodiment which is inserted into a body cavity, and the optical scanning probe 2 for operation control and image display. And a control device 3 having the function of.

The optical scanning probe 2 has an elongated and flexible probe insertion portion 4 which is inserted into a body cavity, a hard tip housing portion 5 provided at the tip end of the probe insertion portion 4, and a probe insertion portion. 4 and a connector portion 6 provided at the rear end of the connector 4. The connector portion 6 is detachably connected to the control device 3.

In the present embodiment, as will be described with reference to FIG. 2, the light source and the optical system are built in the tip housing portion 5 at the tip of the optical scanning probe 2, and the connector portion 6 simply connects the signal line to the control device 3. It has a structure to do.

Then, low coherence light is emitted to the observation object 8 side through the cover glass 7 of the observation window provided on the side surface portion of the distal end housing portion 5, and the reflected light is received by the light detecting means. Photoelectric conversion is performed and input to the control device 3 so that it can be displayed as an image.

As shown in FIG. 2, the probe insertion portion 4 of the optical scanning probe 2 is formed by, for example, a tightly wound coil 9 and a flexible tube 10 that watertightly covers the outer peripheral surface of the closely wound coil 9 and has a rigid tip portion. The light-shielding front housing 5 is fixed in a watertight manner.

Inside the tip housing 5, a low interference light source 11 formed of a super luminescent diode (SLD) is attached to a light source holder 12 and arranged. The low-interference light source 11 has a light source driving circuit (light source light emitting circuit) 14 inside the control device 3 through a signal line 13a.
The low-interference light source 11 outputs low-coherence light from its light emitting portion in response to a drive signal from the light source drive circuit 14.

A collimator lens 15 for making a parallel light flux is arranged in front of the light emitting portion of the low coherence light source 11, and a beam splitter 16 formed of a prism as an optical path branching element is arranged in front of the collimator lens 15. It splits into light that is transmitted and proceeds to the object side and light that is reflected and becomes reference light. As will be described later, the beam splitter 16 also serves as a light mixing means, that is, a means for mixing the split light beams and guiding the interference light to the light detecting means side.

The light splitting surface 16a of the beam splitter 16 is 45 with respect to the optical axis of the light emitted from the low coherence light source 11.
And splits into transmitted light and reflected light that is orthogonal thereto.

Further, a prism mirror (referred to as a prism mirror) 17 is disposed on the side of the beam splitter 16 which is desired to be reflected light. This prism mirror 1
The reflecting surface 7 forms an angle of 90 ° with the light splitting surface 16a of the beam splitter 16. A collimator lens 18 is arranged on the optical path reflected by the prism mirror 17,
A piezo drive mirror 19 having a function as an optical frequency shifter is attached to the mirror holder 20 at the focus position.

The piezo drive mirror 19 is provided with a signal line 13b.
Is connected to a personal computer (abbreviated as PC in FIG. 1) 21 inside the control device 3, and a control signal or a drive signal from the personal computer 21 causes the mirror surface of the piezo drive mirror 19 to move in the optical axis direction as indicated by arrow A. Move back and forth.

A two-dimensional scan mirror 22 for performing a two-dimensional scan is arranged on the front side of the beam splitter 16, and an objective lens 23 is arranged on the reflection optical path side thereof.

The two-dimensional scan mirror 22 has a signal line 1
The scanning drive circuit 25 in the control device 3 is connected via 3c, and the two-dimensional scanning mirror 22 causes the beam splitter 16 to move by the scanning drive signal from the scanning drive circuit 25.
Reflects the light incident from the two-dimensional scanning,
The low coherence light 2 is transmitted to the observation object 8 side through the objective lens 23.
It is emitted so as to scan dimensionally.

The light reflected on the observation object 8 side passes through the opposite optical path, and a part of the light is reflected on the side surface opposite to the prism mirror 17 by the light branching surface 16a of the beam splitter 16. The light is branched, collected by a condenser lens 26 arranged so as to face the side surface, and received by a photodetector 27.

The signal photoelectrically converted by the photodetector 27 is input to the demodulator 28 in the control device 3 through the signal line 13d and demodulated. The signal demodulated by the demodulator 28 is converted into a digital signal by the A / D converter 29 and then input to the personal computer 21, converted into image data by the personal computer 21, and then output to the display 30. The image is displayed on the display 30.

In FIG. 2, the optical path from the light splitting surface 16a of the beam splitter 16 to the observation object 8 is the object side optical path 31. An optical path from the light branching surface 16a to the piezo drive mirror 19 through the prism mirror 17 and the collimator lens 18 serves as a reference side optical path 32.

Further, the reference side optical path 32 is a part thereof,
Specifically, from the prism mirror 17 to the piezo drive mirror 1
The optical path portion reaching 9 is in the axial direction of the optical scanning probe 2 (see FIG.
It has a portion 32a parallel to the left-right direction).

The operation of the optical scanning probe 2 having such a configuration will be described below. Emitted from the low interference light source 11,
For example, near-infrared low-coherence light is made into a parallel light beam by the collimator lens 15 and is incident on the beam splitter 16. A part of the light that has entered the beam splitter 16 passes through the light branching surface 16 a and obliquely enters the reflecting surface of the two-dimensional scan mirror 22.

The low coherence light that has entered the reflecting surface of the two-dimensional scan mirror 22 is reflected in the direction orthogonal to the axis of the optical scanning probe 2 and enters the objective lens 23. It is condensed by this objective lens 23 and focused on the observation object 8.

The two-dimensional scan mirror 22 is electrically driven by the scan drive circuit 25 of the control device 3 so that the reflection surface is two-dimensionally tilted. Thereby, the focal point of the low coherence light on the observation object 8 is two-dimensionally scanned on the observation object 8.

On the other hand, a part of the light emitted from the low interference light source 11 and incident on the beam splitter 16 is reflected by the light branching surface 16a and travels to the reference side optical path 32. That is, the light reflected by the light splitting surface 16 a of the beam splitter 16 is obliquely incident on the reflecting surface of the prism mirror 17.

The low coherence light reflected by the reflecting surface of the prism mirror 17 is reflected in the direction parallel to the axis of the optical scanning probe 2 and enters the collimator lens 18. It is condensed by this lens 18 and focused on the piezo drive mirror 19. The piezo drive mirror 19 is electrically driven by a drive signal from the personal computer 21, and its reflection surface reciprocates in the direction perpendicular to the optical axis. That is, it moves back and forth in the direction indicated by symbol A in FIG.

Since the light is reflected by the piezo drive mirror 19, the frequency ω of the low coherence light is equal to the Doppler shift frequency Ω corresponding to the axial speed of the piezo drive mirror 19.
A light shifted from is generated.

Part of the light reflected or scattered by the observation object 8 returns to the light branching surface 16a of the beam splitter 16 via the objective lens 23. This optical path is the object-side optical path 3
It is 1.

Similarly, the light reflected by the piezo-driving mirror 19 and frequency-modulated is again collimated by the collimator lens 18 into a parallel beam, and returns to the light splitting surface 16a of the beam splitter 16. This optical path is the reference side optical path 32.

Lights of the object side optical path 31 and the reference side optical path 32 are mixed at the optical branching surface 16a of the beam splitter 16, and the optical path lengths of the object side optical path 31 and the reference side optical path 32 are low interference light source 11.
When they match within the range of the coherence length of the light, the interference light having the frequency of the Doppler shift frequency Ω is generated.

Here, if the optical path length adjusting means is adjusted in advance so that the optical path length on the reference side and the optical path length to the observation point on the object side match, the information from the observation object 8 becomes interference light. You will always get it.

When the interference light is condensed on the photodetector 27 by the condenser lens 26 and converted into an electric signal, and only the signal near the frequency twice the frequency shift amount of the frequency shifter is taken out by the demodulator 28. The signal from the observation point can be detected with high S / N by the optical heterodyne detection.

This signal is synchronized with the scanning of the condensing point on the observation object 8 and is transmitted via the A / D converter 29 to the personal computer 21.
The image of the observation object 8 can be obtained by capturing the data with the display unit 30 and displaying the demodulation signal on the display 30 with the brightness corresponding to the scanning position.

Since the object-side optical path 31 and the reference-side optical path 32 are provided inside the hard tip housing 5 of the probe insertion portion 4 of the optical scanning probe 2, when they are inserted into the body cavity, the inside of the body cavity is Bending and twisting due to the shape are not received, and the optical positional relationship is kept stable.

Therefore, even if the optical scanning probe 2 is placed in any posture while being inserted into the body cavity, the optical path lengths of the object-side optical path 31 and the reference-side optical path 32 do not change due to the posture changes, and the image of the observation object 8 is displayed. You can always get it in the preset state,
Therefore, there is an effect that it is possible to obtain a good image which is not affected by the fluctuation of the optical path length.

Further, since a part of the reference side optical path 32 is formed parallel to the axial direction of the insertion section 4, the radial dimension of the optical scanning probe 2 can be reduced.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. 3 (A) and 3 (B). 3 (A) and 3 (B) are different from each other from a direction different from each other by 90 °.
3A is a diagram when a tip portion of the optical scanning probe of the embodiment is viewed, and specifically, FIG. 3A is a plan sectional view and FIG.
(B) is a side sectional view.

The optical scanning probe 2B of this embodiment has a tip housing 5b of the probe insertion portion 4 which can be inserted into the subject.
Inside, a low coherence light source 11, a collimator lens 15 in front of the light emitting portion of the low coherence light source 11, and a beam splitter 41 by a prism as an optical path branching element are arranged in front of the collimator lens 15.

The light splitting surface 41a of the beam splitter 41 is 45 with respect to the optical axis of the light emitted from the low coherence light source 11.
I have a degree.

This beam splitter 41 has a reflecting surface 41b.
Have. The reflecting surface 41b is parallel to the light splitting surface 41a of the beam splitter 41.

A condenser lens 42 is arranged at a front position facing the reflecting surface 41b of the beam splitter 41, and a fixed reflection mirror 43 fixed at a front position of the condenser lens 42 is arranged at the front position. Reflection mirror 43
The two-dimensional scan mirror 22 is arranged on the optical path reflected by the, and the objective lens 23 is further arranged on the optical path reflected by the two-dimensional scan mirror 22.

This objective lens 23 has a tip housing 5b.
It is arranged so as to face the cover glass 7 attached to the observation window on the front end surface of, and emits low-coherence light to the observation object 8 side through the cover glass 7. That is, the present embodiment is the direct-viewing type optical scanning probe 2B.

A prism 44 for returning the light is arranged at a front position of the beam splitter 41 facing the light splitting surface 41a, and the light returned by the prism 44 is collimator lens arranged under the beam splitter 41. After passing through 18, it is guided to a piezo drive mirror 19 as an optical frequency shifter, facing the collimator lens 18.

As shown in FIG. 3A, the beam splitter 41 has a second reflecting surface 4 on the side opposite to the reflecting surface 41b.
Have 1c. A condenser lens 26 and a photodetector 27 that receives the light condensed by the condenser lens 26 are arranged at a rear position on the optical path reflected by the reflection surface 41c.

Here, the optical path from the light splitting surface 41a of the beam splitter 41 to the observation object 8 is the object side optical path 45.
Becomes

Further, from the light branching surface 41a to the prism 44,
The optical path to the piezo drive mirror 19 via the collimator lens 18 becomes the reference side optical path 46.

Further, the reference side optical path 46 has, at a part thereof, portions 46a and 46b parallel to the axial direction of the optical scanning probe 2B (left and right direction in FIG. 3).

Further, in this embodiment, the table 20 to which the piezo driving mirror 19 is attached is made movable in the optical axis direction of the collimator lens 18 by the linear motor 47. In other words, the linear motor 47 moves the reflecting surface of the piezo drive mirror 19 together with the table 20 as indicated by reference numeral B in FIG. 3B, and the optical path length of the reference side optical path 46 is changed and set according to the observation object 8. The optical path length adjusting mechanism is formed in such a manner that it is possible.

This linear motor 47 is connected to the personal computer 21 of the control device 3 shown in FIG. 1 through the signal line 13e, and when the user operates the keyboard to change and set the optical path length, the personal computer 21 is instructed. The linear motor 47 is controlled so as to move the table 20 to the front side or the rear side by the specified value. The actual amount of movement by the linear motor 47 is detected by an encoder or the like not shown,
It moves forward or backward by the amount of movement detected by this encoder. The other configuration is the same as that of the first embodiment.

Next, the operation of the optical scanning probe 2B of this embodiment will be described. The near-infrared low-coherence light emitted from the low-coherence light source 11 is collimated by the collimator lens 15 and enters the beam splitter 41. A part of the light that has entered the beam splitter 41 is reflected by the light splitting surface 41a, further reflected by the reflecting surface 41b, enters the fixed reflecting mirror 43 through the condensing lens 42 facing the same, and is reflected to perform two-dimensional scanning. The light is obliquely incident on the reflection surface of the mirror 22.

The low interference light incident on the reflecting surface of the two-dimensional scan mirror 22 is reflected in the axial direction of the optical scanning probe 2B and enters the objective lens 23. It is condensed by the objective lens 23 and focused on the observation object 8.

When the two-dimensional scan mirror 22 is electrically driven, its reflecting surface is two-dimensionally tilted. Thereby, the focal point of the low coherence light on the observation object 8 is two-dimensionally scanned on the observation object.

On the other hand, part of the light that has entered the beam splitter 41 passes through the light splitting surface 41a and enters the prism 44. Two reflecting surfaces 44a and 44b of this prism 44
It is totally reflected at and turned back. Then, it enters the collimator lens 18.

The light is condensed by the collimator lens 18 and focused on the piezo drive mirror 19. When the piezo drive mirror 19 is electrically driven, the reflecting surface reciprocates in the direction perpendicular to the optical axis. That is, it is moved back and forth as indicated by arrow A. The light reflected by the piezo drive mirror 19 generates light shifted from the light frequency ω by the Doppler shift frequency Ω corresponding to the axial speed of the piezo drive mirror 19.

A part of the light reflected or scattered by the observation object 8 returns to the light branching surface 41a of the beam splitter 41 by returning through the light path opposite to the above-mentioned light path. This optical path is the object side optical path 45.

Similarly, the light reflected by the mirror 19 and frequency-modulated returns to the light branching surface 41a of the beam splitter 41 which is collimated by the collimator lens 18 again.
This optical path is the reference side optical path 46.

Lights of the object side optical path 45 and the reference side optical path 46 are mixed at the optical branching surface 41a of the beam splitter 41, and the optical path lengths of the object side optical path 45 and the reference side optical path 46 are low coherence light source 1.
When they match within the coherence length range of 1, interference light having a frequency of the Doppler shift frequency Ω is generated.

Here, if the optical path length adjusting means is adjusted in advance so that the optical path length on the reference side and the optical path length to the observation point on the object side coincide with each other, the information from the observation object 8 becomes interference light. You will always get it. The interference light is condensed on the photodetector 27 by the condenser lens 26 and converted into an electric signal.

Then, as shown in FIG. 1, when the demodulator 28 extracts only the signal in the vicinity of the frequency twice the frequency transition amount of the frequency shifter, the signal from the observation point is detected at a high S / N ratio by the optical heterodyne detection. Can be detected. This signal is taken into the personal computer 21 via the A / D converter 29 in synchronization with the scanning of the focal point on the observation object 8 and the demodulation signal is displayed on the display 30 in the brightness corresponding to the scanning position for observation. An image of the object 8 can be obtained.

In the present embodiment, since the object side optical path 45 and the reference side optical path 46 are provided inside the hard tip portion of the probe insertion portion 4 of the optical scanning probe 2B, the body side cavity when inserted into the body cavity. There is no bending or twisting due to the inner shape, and the optical positional relationship is kept stable.

Therefore, no matter which posture the optical scanning probe 2B is in while it is inserted into the body cavity, the optical path lengths of the object-side optical path 45 and the reference-side optical path 46 do not change due to posture changes, and a correct observation target image is obtained. be able to.

Further, from the light branching surface 41a to the photodetector 27.
By bending the optical path leading to, the outer shape of the tip housing 5b can be made smaller than that of the first embodiment.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIGS. 4 (A) and 4 (B). 4 (A) and 4 (B) are the third from the direction different from each other by 90 °.
FIG. 4A is a diagram when a tip portion of the optical scanning probe of the embodiment is viewed, and specifically, FIG.
(B) is a side sectional view.

The optical scanning probe 2C according to the present embodiment is similar to the second embodiment except that the lower side of the prism 44 is cut out, an EO element 51 as an optical frequency shifter is arranged, and a piezo drive mirror 19 is further provided. Simply a reflective mirror 52
It has the same structure as the above. The EO element 51 is connected to the personal computer 21 via the signal line 13b.

More specifically, the low coherence light source 11 is provided inside the tip housing 5b of the probe insertion section 4 which can be inserted into the subject, and the collimator lens 15 is provided in front of the light emission section of the low coherence light source 11. , This collimator lens 15
A beam splitter 41 formed of a prism as an optical path branching element is disposed in front of the. The light splitting surface 41a of the beam splitter 41 forms 45 ° with respect to the optical axis of the light emitted from the low coherence light source 11.

Further, the beam splitter 41 has a reflecting surface 41b. The reflecting surface 41b is parallel to the light splitting surface 41a of the beam splitter 41. A condenser lens 42 is arranged in front of the beam splitter 41, and a fixed reflection mirror 43, a two-dimensional scan mirror 22 facing the fixed reflection mirror 43, and an objective lens 23 are arranged in front of the condenser lens 42. .

In front of the beam splitter 41,
A prism 44 that returns light is arranged, and this prism 4
The light reflected by the two reflecting surfaces 44a and 44b of No. 4 so as to be folded back is incident on the EO element 51 as an optical frequency shifter arranged on the optical path. The light that has passed through the EO element 51 is condensed by the collimator lens 18 that is arranged to face it, and is incident on the reflection mirror 52.

The beam splitter 41 has the second reflecting surface 41c as described above. The light reflected by the reflecting surface 41c is condensed by the condensing lens 26 arranged on the rear side of the optical path, and the photodetector 2 as the light receiving element.
It is incident on 7.

Here, the optical path from the light splitting surface 41a of the beam splitter 41 to the observation object 8 is the object side optical path 45.
Becomes Further, the optical path from the light branching surface 41a to the reflection mirror 52 via the prism 44 and the collimator lens 18 becomes the reference side optical path 46. This reference side optical path 46 has a part thereof in the axial direction of the optical scanning probe 2C (left and right direction in FIG. 4).
And portions 46a and 46b parallel to the.

Next, the operation of the optical scanning probe 2C of this embodiment will be described. The near-infrared low-coherence light emitted from the low-coherence light source 11 is collimated by the collimator lens 15 and enters the beam splitter 41. A part of the light incident on the beam splitter 41 is reflected by the light splitting surface 41a, further reflected by the reflecting surface 41b, enters the fixed reflection mirror 43 through the condenser lens 42, is reflected, and is reflected by the two-dimensional scan mirror 22. Is obliquely incident on the reflection surface of.

The low-coherence light that has entered the reflecting surface of the two-dimensional scan mirror 22 is reflected in the axial direction of the optical scanning probe 2C and enters the objective lens 23. This objective lens 23
The light is focused by and is focused on the observation object 8. When the two-dimensional scan mirror 22 is electrically driven, the reflection surface tilts in two dimensions. Thereby, the focal point of the low coherence light on the observation object 8 is two-dimensionally scanned on the observation object 8.

On the other hand, part of the light that has entered the beam splitter 41 passes through the light splitting surface 41a and enters the prism 44. Two reflecting surfaces 44a and 44b of this prism 44
Then, the light is reflected by the laser beam, is turned back, and enters the EO element 51.
This EO element 51 has electrodes formed on the surface of an electro-optical crystal, and when a voltage is applied between the electrodes via a personal computer 21, the optical constants of the electro-optical crystal change and the light passing through the inside is modulated. is there.

When the light passes through the EO element 51, light shifted from the optical frequency ω by an integral multiple of the frequency Ω of the signal driving the EO element 51 is generated. Further, it enters the collimator lens 18, is condensed by this lens 18, and is focused on the reflection mirror 52.

A part of the light reflected or scattered by the observation object 8 returns to the light branching surface 41a of the beam splitter 41 by returning through the light path opposite to the above-mentioned light path. This optical path is the object side optical path 45. Similarly, the light reflected by the reflection mirror 52 and frequency-modulated is again made into a parallel beam by the collimator lens 18 and returns to the light branching surface 41 a of the beam splitter 41. This optical path is the reference side optical path 46.

The lights of the object side optical path 45 and the reference side optical path 46 are mixed at the optical branching surface 41a of the beam splitter 41, and the optical path lengths of the object side optical path 45 and the reference side optical path 46 are equal to the coherence length of the low coherence light source 11. When they match in the range, the interference light modulated at the frequency resulting from the driving frequency of the EO element 51 is generated.

Here, if the optical path length adjusting means is adjusted in advance so that the optical path length on the reference side and the optical path length to the observation point on the object side match, the reflected light information from the observation object 8 interferes. It will always be obtained as light. The interference light is condensed on the photodetector 27 by the condenser lens 26 and converted into an electric signal.

Then, as shown in FIG. 1, when the demodulator 28 extracts only the signal near the modulation frequency of the interference light,
High S / N of the signal from the observation point by optical heterodyne detection
Can be detected with. This signal is taken into the personal computer 21 via the A / D converter 29 in synchronism with the scanning of the focal point on the observation target, and the demodulation signal is displayed on the display 30 with the brightness corresponding to the scanning position, thereby observing the observation target. 8 images can be obtained.

Since the object side optical path 45 and the reference side optical path 46 are provided inside the hard container at the tip of the probe insertion portion 4 of the optical scanning probe 2C, the shape inside the body cavity when inserted into the body cavity. The optical positional relationship is kept stable without being bent or twisted due to.

Therefore, no matter what position the optical scanning probe 2C is in while it is inserted into the body cavity, the optical path lengths of the object-side optical path 45 and the reference-side optical path 46 do not change due to changes in the attitude, and a correct observation target image is obtained. You can

Furthermore, since the EO element 51 can be driven at a higher speed than the piezo driving mirror 19, it is possible to support image display at a higher frame rate than when the piezo driving mirror 19 is used as a frequency shifter.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to FIGS. 5 (A) and 5 (B) are from the direction different from each other by 90 °
FIG. 5A is a diagram when the tip portion of the optical scanning probe of the embodiment is viewed, and specifically, FIG. 5A is a plan sectional view.
(B) is a side sectional view.

The optical scanning probe 2C of the present embodiment is different from the second embodiment in that the light reflected by the reflecting surface 41c of the beam splitter 41 is received by the photodetector 27 via the condenser lens 26. In addition, the photodetector 27 arranged on the back side of the low coherence light source 11 receives light.

More specifically, the optical scanning probe 2D according to the present embodiment has the low coherence light source 1 inside the tip housing 5b of the probe insertion portion 4 which can be inserted into the subject.
1. A collimator lens 15 is provided in front of the light emitting portion of the low coherence light source 11, and a beam splitter 41 as an optical path branching element is provided in front of the collimator lens 15. The light splitting surface 41a of the beam splitter 41 is inclined with respect to the optical axis of the light emitted from the low coherence light source 11.

Further, the beam splitter 41 has a reflecting surface 41.
b. The reflecting surface 41b is parallel to the light splitting surface 41a of the beam splitter 41. A lens 42 is provided in front of the beam splitter 41, and a fixed reflection mirror 43, a two-dimensional scan mirror 22, an objective lens 23 are provided in front of the lens 44.
Are arranged. A prism 44 is arranged in front of the beam splitter 41, a lens 18 is arranged below the beam splitter 41, and a piezo drive mirror 19 is arranged behind the lens 18. A light receiving element 27 is arranged behind the low coherence light source 11.

The optical path from the light splitting surface 41a of the beam splitter 41 to the observation object 8 is the object side optical path 45.

An optical path from the light branching surface 41a to the mirror 19 through the prism 44 and the lens 18 is the reference side optical path 46. Further, the reference side optical path 46 has portions 46a and 46b which are parallel to the axial direction of the optical scanning probe 2D (left and right direction in FIG. 5).

Next, the operation of the optical scanning probe 2D of this embodiment will be described. The near-infrared low-coherence light emitted from the low-coherence light source 11 is collimated by the collimator lens 15 and enters the beam splitter 41. A part of the light incident on the beam splitter 41 is reflected by the light splitting surface 41a.

Further, the light is reflected by the reflecting surface 41b, and the lens 42
Then, the light enters the fixed reflection mirror 43, is reflected, and obliquely enters the reflection surface of the two-dimensional scan mirror 22. The low coherence light that has entered the reflecting surface of the two-dimensional scan mirror 22 is reflected in the axial direction of the optical scanning probe 2D and enters the objective lens 23.

It is condensed by the objective lens 23 and focused on the observation object 8. When the two-dimensional scan mirror 22 is electrically driven, the reflection surface tilts in two dimensions. As a result, the focal point of the low interference light on the observation target 8 is two-dimensionally scanned on the observation target.

On the other hand, part of the light that has entered the beam splitter 41 passes through the light splitting surface 41a and enters the prism 44. The light is reflected by the two reflecting surfaces 44a and 44b of the prism 44 and folded back. Further, the light enters the lens 18.

It is condensed by this lens 18 and focused on the piezo drive mirror 19. When the piezo drive mirror 19 is electrically driven, the reflecting surface reciprocates in the direction perpendicular to the optical axis. Since the light is reflected by the piezo drive mirror 19, the light frequency ω is equal to the Doppler shift frequency Ω according to the axial speed of the piezo drive mirror 19.
A light shifted from is generated.

The light reflected and scattered by the observation object 8 is
Returning the optical path opposite to the optical path described above, the beam splitter 41
Return to the light branching surface 41a. This optical path is the object side optical path 45.

Similarly, the light reflected by the mirror 19 and frequency-modulated returns again to the light splitting surface 41a of the beam splitter 41 which is made into a parallel beam by the lens 18. This optical path is the reference side optical path 46.

The light on the object side optical path 45 and the light on the reference side optical path 46 are mixed at the optical branching surface 41a of the beam splitter 41, and the optical path lengths of the object side optical path 45 and the reference side optical path 46 are low coherence light source 1.
When they match within the coherence length range of 1, interference light having a frequency of the Doppler shift frequency Ω is generated. Here, if the optical path length adjusting means is adjusted in advance so that the optical path length on the reference side and the optical path length to the observation point on the object side match, information from the observation target is always obtained as interference light. Become.

This interference light passes through the collimator lens 15 and the low coherence light source 11, and the light receiving element 2 arranged on the back side thereof.
It is incident on 7. The light receiving element 27 converts the light intensity into an electric signal, and when the demodulator 28 shown in FIG. 1 extracts only the signal in the vicinity of the frequency Ω, the signal from the observation point can be detected with high S / N by the optical heterodyne detection. .

This signal is taken into the personal computer 21 by the A / D converter 29 in synchronism with the scanning of the focal point on the observation target, and the demodulated signal is displayed on the display 30 with the brightness corresponding to the scanning position to observe. An image of the object 8 can be obtained.

Here, since the object side optical path 45 and the reference side optical path 46 are provided inside the hard tip of the probe insertion portion 4 of the optical scanning probe 2D, when they are inserted into the body cavity,
The optical positional relationship is kept stable without being bent or twisted due to the shape inside the body cavity.

Therefore, even if the optical scanning probe 2D is placed in any posture while being inserted into the body cavity, the optical path lengths of the object-side optical path and the reference-side optical path do not change due to the posture change, and a correct observation target image can be obtained. it can.

Further, in this embodiment, the light branching surface 41 is used.
Since the optical path from a to the light receiving element 27 is arranged coaxially with the low coherence light source 11, the outer shape of the tip housing 5b can be made smaller than in the second and third embodiments.

According to each of the embodiments described above, the optical path on the object side and the optical path on the reference side are provided with the probe insertion portion 4 of the optical scanning probe.
Since it is provided inside the hard tip, it is not bent or twisted due to the shape inside the body cavity when inserted into the body cavity, and the optical positional relationship is kept stable.

Therefore, even if the optical scanning probe is inserted into the body cavity in any posture, the optical path lengths of the optical path on the object side and the optical path on the reference side do not change due to changes in the posture, and a correct observation target image can be obtained. An optical scanning probe can be provided.

Although the piezo driving mirror 19 is provided on the reference side optical path side in the above-described embodiment, for example, the first embodiment, an optical modulator such as an EO element may be provided on the object side optical path side. You can Further, an embodiment configured by partially combining the above-described embodiments also belongs to the present invention.

[Additional Notes] 1. The optical scanning probe according to claim 1, wherein a low-coherence light source is also disposed inside the hard tip.

2. In claim 1, a modulation means for performing light modulation is further provided on one optical path side of the reference side optical path and the object side optical path. 3. In claim 1, an optical path length adjusting means for adjusting the optical path length on the reference side is further provided on the reference side optical path side.

4. Inside the tip of the insertion part that can be inserted into the subject, an optical path branching element, an optical frequency shifter, a part of the object side optical path from the optical branching element to the observation point, and from the optical branching element to the optical frequency shifter. And a reference side optical path that branches, at least a part of the reference side optical path,
An optical scanning probe, which is parallel to the axial direction of the optical scanning probe.

5. Inside the tip of the insertion part that can be inserted into the subject, an optical path branching element, an optical frequency shifter, a part of the object side optical path from the optical branching element to the observation point, and from the optical branching element to the optical frequency shifter. An optical scanning probe having at least a branched reference side optical path, and one portion of the reference side optical path is parallel to an axial direction of the optical scanning probe.

6. Inside the tip of the insertion part that can be inserted into the subject, the optical path branching element, the optical frequency shifter, a part of the object side optical path from the optical branching element to the observation point, and from the optical branching element to the optical frequency shifter. And a reference side optical path that branches off, and the reference side optical path is 180 ° in the middle thereof.
An optical scanning probe, which is folded back and has two portions parallel to the axial direction of the optical scanning probe.

7. Inside the tip of the insertion part that can be inserted into the subject, the optical path branching element, the optical frequency shifter, a part of the object side optical path from the optical branching element to the observation point, and from the optical branching element to the optical frequency shifter. At least a part of the reference side optical path that branches off and the light receiving element are parallel to the axial direction of the optical scanning probe, and the optical path from the light branching element to the light receiving element also has An optical scanning probe characterized in that a part thereof is parallel to the axial direction of the optical scanning probe.

[0122]

As described above, according to the present invention, the low-coherence light from the low-coherence light source is guided to the object side to be measured, inside the hard tip of the insertion portion that can be inserted into the subject. Optical path splitting means for splitting an optical path into an object side optical path and a reference side optical path serving as a reference side, and light mixing means for mixing the light from the object side optical path and the reference side optical path and guiding the mixed light to the light detecting means side as interference light. Since and are provided, no matter how the posture is changed during insertion of the insertion part into the body cavity, there is no change in the optical path lengths of the object-side optical path and the reference-side optical path due to the posture change, and the correct observation target image is stabilized. You can get it.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an interference-type optical imaging apparatus including a first embodiment of the present invention.

FIG. 2 is a plan cross-sectional view of the configuration on the tip side of the optical scanning probe according to the first embodiment.

FIG. 3 is a cross-sectional view of the configuration on the tip side of an optical scanning probe according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view of the configuration on the tip side of an optical scanning probe according to a third embodiment of the present invention.

FIG. 5 is a cross-sectional view of the configuration on the tip side of an optical scanning probe according to a fourth embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of a conventional interference type OCT.

[Explanation of symbols]

1. Optical imaging device 2 ... Optical scanning probe 3 ... Control device 4 ... Probe insertion part 5 ... Tip housing part 6 ... Connector part 8 ... Observing object 11 ... Low interference light source 13a to 13d ... Signal line 15 ... Collimator lens 16 ... Beam splitter 17 ... Prism mirror 18 ... Collimator lens 19 ... Piezo drive mirror 21 ... PC 22 ... Two-dimensional scan mirror 23 ... Objective lens 25 ... Scan drive circuit 26 ... Condensing lens 27 ... Photodetector 28 ... Demodulator 29 ... A / D converter 30 ... Display 31 ... Object-side optical path 32 ... Reference side optical path

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02B 26/10 104 G01B 11/24 D 4C061 F term (reference) 2F064 AA09 EE01 FF03 GG02 GG12 GG13 GG22 GG24 GG44 GG55 GG68 HH03 JJ05 2F065 AA51 CC16 FF52 FF67 GG07 GG21 HH14 JJ03 LL02 LL04 LL13 LL46 LL53 LL62 MM16 NN08 QQ03 2G059 AA06 BB12 EE09 FF01 FF06 GG02 HH01 JJ11 JJ12 JJ13 JJ15 JJ18 JJ22 JJ30 LL01 MM09 PP04 2H041 AA23 AB14 AC08 AZ02 2H045 AB13 BA12 4C061 CC06 DD03 FF47 HH51

Claims (3)

[Claims] 1. An object-side optical path that guides low-coherence light from a low-coherence light source to an object side to be measured inside a hard tip of an insertion portion that can be inserted into a subject, and a reference side that is a reference side. An optical path branching means for branching the optical path to an optical path, and a light mixing means for mixing the light from the object side optical path and the reference side optical path and guiding the mixed light to the light detecting means side as interference light. Optical scanning probe. 2. The optical scanning probe according to claim 1, wherein the optical path branching unit also has a function of the light mixing unit. 3. The optical scanning probe according to claim 1, wherein the optical path on the object side is provided with scanning means for two-dimensionally scanning low coherence light.