JP2014094121A - Light transmission device, and optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light transmission device and an optical element, which are relatively inexpensive and excellent in assembly easiness and can be miniaturized.SOLUTION: The leading end portion of an optical fiber 200 has an end face inclined at a predetermined angle θ (0 degrees<θ<90 degrees ) with respect to the axial direction of the optical fiber 200 so that it can suppress the noises due to a light reflected on an end face. Moreover, a first face 203a of a prism 203 contacts the end face of the optical fiber 200 so that the optical fiber 200 and the prism 203 can be positioned merely by adjusting the phases thereby to retain an assembling feasibility. Moreover, the prism 203 is attached to the leading end of the optical fiber 200 and is intrinsically small-sized so that the entire construction can be made smaller and so that the distance from the prism 203 to the focal position can be shortened to easily observe even an observation object of a small diameter.

Description

  The present invention relates to an optical transmission device, and more particularly to an optical transmission device and an optical element suitable for use in an optical coherence tomographic image forming apparatus.

  In recent years, in the case of diagnosing a living tissue, an optical coherence tomographic image generation device that can obtain optical information inside the tissue has been proposed in addition to an image generation device that obtains optical information on the surface state of the tissue. . The optical coherence tomographic image generation device separates the low-coherence light into two, irradiates one of the observation sample such as a biological tissue, interferes with the other light the scattered light given the phase information of the observation sample, The phase information of the subject is obtained from the intensity information of the interference light, and the measurement location of the observation sample is imaged (see, for example, Patent Document 1).

JP 2009-201969 A

  By the way, in the optical coherence tomographic image generating apparatus disclosed in Patent Document 1, after the low coherence light is propagated through the optical fiber, it is reflected by the reflecting surface, and the light that can irradiate the observation sample from the side surface of the optical probe. A fiber probe is provided. In this optical fiber probe, since the tip end portion of the optical fiber is cut obliquely, the light propagating through the optical fiber is less likely to be reflected by the end face, and noise can be reduced accordingly.

  However, in the technique of Patent Document 1, light is collected by a gradient index lens or the like attached to the tip of an optical fiber, reflected by a reflecting surface, and irradiated on the side surface of the optical fiber probe. Therefore, the light reflected by the optical surface and reflection surface of the gradient index lens is detected as an interference signal, which may cause noise on the observation sample. In addition, the refractive index distribution type lens is relatively expensive, and it is necessary to position the lens and the reflecting surface with respect to the optical fiber with high accuracy during assembly, which increases the manufacturing cost of one optical fiber probe. There is a problem of end. In addition, since the distance between the optical fiber and the reflecting surface must be secured, the size of the optical fiber probe is increased.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a light transmission device and an optical element that are relatively inexpensive, excellent in ease of assembly, and capable of being downsized.

The optical transmission device according to claim 1, wherein the optical transmission device includes at least one optical fiber including a core portion and a cladding portion, and an optical element provided at an end portion of the optical fiber.
The tip of the optical fiber has an end face that is inclined at a predetermined angle θ (O degrees <θ <90 degrees) with respect to the axial direction of the optical fiber,
The optical element includes a first surface that is in contact with an end surface of the optical fiber, a second surface that reflects a light beam emitted from the end surface of the optical fiber and incident from the first surface, and a light beam reflected by the second surface. A third surface that emits light, and irradiation light emitted from the third surface is irradiated onto the observation target.

  According to the present invention, the end portion of the optical fiber has an end surface inclined at a predetermined angle θ (O degrees <θ <90 degrees) with respect to the axial direction of the optical fiber. Since the reflected light from the center deviates from the central axis of the optical fiber, noise caused by the reflected light can be suppressed. Further, since the first surface of the optical element is in contact with the end face of the optical fiber, the positioning of the optical fiber and the optical element is sufficient only for phase alignment, and assembling ease can be ensured. In addition, since the optical element is attached to the tip of the optical fiber, it is inherently small, and the measurement light can be observed without using a separate reflecting member because the second surface is a reflecting surface. Since the distance from the optical element to the focal position can be shortened, the observation can be easily performed even for a small-diameter observation target.

  The angle of the end face of the optical fiber is an angle suitable for preventing reflection within the range of 5 to 15 degrees. In particular, 8 degrees is desirable for the wavelength of light used for optical coherence tomographic image generation equipment and communications, and the noise intensity due to reflection is expected to be suppressed by about 60 dB, but the emitted light passes through the cladding. In order to achieve this, it is desirable to make it larger than 8 degrees.

  The optical transmission device according to claim 2 is characterized in that, in the invention according to claim 1, at least one of the second surface and the third surface of the optical element has a curvature.

  Accordingly, since at least one of the second surface and the third surface has a light condensing function, it is not necessary to separately provide a condensing lens or the like, and the configuration can be simplified and downsized. In particular, the curvature of the third surface provides a function of correcting aberrations that occur when light passes through the cover, such as when a cylindrical transparent cover is provided around the light transmission device. can do.

  According to a third aspect of the present invention, in the optical transmission device according to the first or second aspect, at least one of the second surface and the third surface of the optical element has an aspherical shape. .

  By making at least one of the second surface and the third surface an aspherical surface, it is possible to correct aberrations and the like generated when outgoing light passes through a cylindrical transparent cover, a cladding portion of an optical fiber, etc. Optical properties can be imparted.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the refractive index of the core portion in the optical fiber is different from the refractive index of the optical component. To do.

  By making the refractive index of the core portion in the optical fiber different from the refractive index of the optical component, the light incident on the optical element from the optical fiber can be bent at an arbitrary angle. The second surface can easily satisfy the total reflection condition, and the light utilization efficiency can be increased.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the optical element is produced by molding.

  Since the optical element is small enough to be attached to the end face of the optical fiber, it is desirable to mass-produce highly accurate optical elements by molding.

According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, the irradiation light emitted from the third surface of the optical element further enters the cladding portion of the optical fiber. After that, it comes out from the side of the optical fiber,
The origin of the optical fiber is the origin, the direction of the center of the light beam incident on the optical element from the origin is the Z axis, and is orthogonal to the Z axis in a plane including the axis of the optical fiber and the Z axis. The direction is the Y axis, the direction orthogonal to the Z axis and the Y axis is the X axis, the curvature of the second surface in the ZY plane is Py (1 / mm), and the second surface in the ZX plane Py <Px, and 4 <Py <10 and 5 <Px <20.

  The shape and size of the spot of irradiation light condensed by the light transmission device is determined by the distance from the end face of the optical fiber to the second surface of the optical element and the curvature of the second surface. However, when the irradiation light emitted from the third surface of the optical element further enters the cladding portion of the optical fiber and then exits from the side surface of the optical fiber, the irradiation light passes through the cladding portion. Since it is affected by the curvature of the cladding when passing, in order to form a condensing spot with an optimal shape, the curvature of the second surface is divided into the direction in which the curvature of the cladding is affected and the direction perpendicular thereto. It is necessary to make a difference. According to the present invention, the second surface has the curvatures Px and Py as described above, so that the light beam emitted from the end surface of the optical fiber and incident from the first surface is the second surface of the optical element. After being reflected by the surface, the irradiation light emitted from the third surface is appropriately condensed at a close position corresponding to the fact that it further passes through the cladding portion of the optical fiber.

  The optical transmission device according to claim 7 is the invention according to claim 6, wherein Py <1 when the distance from the origin to the intersection of the Z axis and the second surface is Z0 (mm). / Z0 <Px is satisfied.

  By giving the second surface a shape that satisfies the relationship of Py <1 / Z0 <Px and 4 <Py <10, 5 <Px <20, the light is emitted from the third surface, Furthermore, after entering the cladding portion of the optical fiber, the light emitted from the side surface of the optical fiber can form a spot of about 0.04 mm at a position about 0.1 mm away from the optical fiber axis. If the outer diameter of the clad part in the embodiment described later is φ0.13 mm, the curvature of the clad part is 15.385, and the direction affected by the curvature Py is also affected by the curvature of the clad part of the optical fiber. “About Amm” means a range of ± 5% with respect to Amm.

  The optical transmission device according to claim 8 is the optical transmission device according to any one of claims 1 to 7, wherein the focus position of the optical element is about 0.1 mm away from the axis of the optical fiber, and the spot size is 0. It is about 04 mm.

  Thus, by forming a small spot at a position close to the axis of the optical fiber, it is suitable for observing a tomography of a very small diameter tube such as a blood vessel.

  A light transmission device according to a ninth aspect is characterized in that, in the invention according to any one of the first to eighth aspects, the first surface is common to the third surface. Thereby, the shape of the optical element can be simplified.

  According to a tenth aspect of the present invention, in the invention according to any one of the first to ninth aspects, the optical transmission device is used in an optical coherence tomographic image forming apparatus.

  The optical element of Claim 11 is used for the optical transmission apparatus in any one of Claims 1-10, and has the 1st surface attached to the end surface of the said optical fiber.

  According to the present invention, it is possible to provide a light transmission device and an optical element that are relatively inexpensive, excellent in assembling, and can be reduced in size.

It is a figure which shows the structure of an optical coherence tomographic image generation apparatus. It is a figure which shows the coupling | bond part of an optical rotary joint and an optical probe. Is a diagram showing the main part of the optical probe, (A) is an expanded sectional view of the principal part of an optical probe, (b) is a front view of the principal part of an optical probe. It is sectional drawing similar to FIG. 4 which shows the modification of a prism. It is sectional drawing similar to FIG. 4 which shows the modification of a prism. It is sectional drawing similar to FIG. 4 which shows the modification of a prism.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, the form of the optical coherence tomographic image generation apparatus 102 will be described. An optical coherence tomographic image generation mounting 102 shown in FIG. 1 acquires a tomographic image of a sample (also called a biological tissue) 103 such as a blood vessel of a human body by a so-called Time Domain method, and includes a low coherence light source 2 and a light source. The light splitting means 4 that splits the low coherence light oscillated from the light, and the low coherence light that has passed through the light splitting means 4 is irradiated as the measurement light 105 on the measurement location of the sample 103 and the light reflected from the sample 103 is optically multiplexed. An optical probe 101 that propagates to the means 4, an optical rotary joint 1 that rotates the optical probe 101 about the axis of the optical probe 101, a lens unit 6 that irradiates low-coherence light that has passed through the light splitting means 4 as reference light, and The mirror 7 that reflects the reference light and propagates the light to the optical multiplexing means 4 and the optical path length through which the reference light propagates are adjusted. That the optical path length adjusting section 8, and a interference light detector 3 for detecting the interference light between being wave reflected light and the reference light by the multiplexing means.

  The light splitting unit 4 is composed of, for example, a 2 × 2 optical fiber coupler, and splits low-coherence light propagating from the light source through the optical fiber into measurement light 105 and reference light. The light dividing means 4 in this example also functions as the optical multiplexing means 4.

  The optical path length adjusting unit 8 is arranged so as to displace the optical distance between the lens unit 6 that collimates the light irradiated as the reference light, the mirror 7 that reflects the reference light, and the lens unit 6 and the mirror 7. A base that is movable in the direction of the middle arrow and an operation unit that moves the base. In order to change the measurement position in the sample 103 in the optical axis direction of the measurement light 105, the reference light It has a function of displacing the optical path length. The part to be moved when the optical distance is displaced may be either the mirror 7 or the lens unit 6.

  Then, the reference light whose optical path length has been displaced by the optical path length adjusting unit 8 is propagated to the optical multiplexing means 4. The reference light propagated to the optical multiplexing means 4 enters the interference light detector 3 that detects the light intensity of the interference light.

  The interference light detection unit 3 detects interference light between the reflected light from the sample 103 combined by the optical multiplexing unit 4 and the reference light, and is based on light incident on the interference light detection unit 3 that is not interference light. It has a function to reduce noise.

  Information on the measurement position of the sample 103 is output from the control unit 9 that controls the optical path length adjustment unit 8 to the image processing unit 5. Then, an optical tomographic image is generated by the image processing unit 5 based on the optical signal detected by the interference light detection unit 3, information on the measurement position in the control unit 9, and information from the control synchronization unit 10. The generated optical tomographic image 104 is displayed on the display device 11.

  Next, the operation of the optical coherence tomographic image generation apparatus 102 having the above configuration will be described. When acquiring a tomographic image, the optical path length of the reference light is first displaced to roughly adjust the optical path length so that the measurement target position of the sample 103 comes within the measurable region. Thereafter, low-coherence light is oscillated from the light source, and this light is split by the light splitting means 4 into measurement light 105 and reference light. The measurement light 105 is propagated from the optical probe 101 toward the sample 103, and the measurement target position is irradiated with low coherence light.

  Information on the sample 103 at a position where the optical distance from the light splitting means 4 until the reference light is reflected by the mirror 7 and the optical distance of the measurement light 105 irradiated and reflected from the light splitting means 4 to the sample 103 coincides. Detected as an interference signal. At this time, the position of the optical interference is displaced at a high speed by displacing the optical path adjustment unit at a high speed, and the measurement light 105 irradiated from the optical probe 101 to the sample 103 scans the measurement target position in one dimension. Then, the reflected light from the measurement target position is combined with the reference light reflected by the mirror 7 by the optical multiplexing means 4, and the interference light between the reflected light and the reference light is detected by the interference light detection unit 3.

  When the optical probe 101 is rotated by the optical rotary joint 1, the measurement light 105 is scanned in the rotation direction of the optical probe 101 on the measurement target position. Since information on the measurement direction of the sample 103 is obtained at each portion along the scanning direction, a tomographic image of a tomographic plane including the scanning direction can be acquired. At this time, one scan of the sample 103 to be measured when the optical probe 101 is rotated 360 ° is completed. Since the optical probe 101 rotates continuously, the rotation angle of the optical probe 101 is detected by the image synchronization unit, and information is output to the image processing unit 5 to accurately generate a tomographic image for the entire circumference of the sample 103. . The tomographic image 104 acquired in this way is displayed on the display device 11.

  The mechanism of the optical coherence tomographic image generation apparatus 102 has been described using the Time Domain method. However, in addition to the Time Domain method, a Spectra Dmain method using a spectroscopic system instead of a single detector, or a sweep source using a wavelength sweep laser. Any of the methods may be used.

  FIG. 2 shows the details of the structure for rotating the optical probe 101 and connecting the optical rotary joint 1 and the optical probe 101 in this embodiment.

  By coupling the optical probe 101 and the optical rotary joint 1 via the connector portion, the light of the low coherence light source 2 is propagated to the optical probe 101 via the optical coupling portion in the optical rotary joint 1.

  The connector portion includes an adapter 32 provided in the optical rotary joint and a connector attached to the optical probe 101. The adapter 32 is fixed to the rotor 37, and the adapter 32 is also rotated as the rotor 37 rotates. The connector here refers to an FC connector, an SC connector or the like generally used in the optical communication field.

  Accordingly, when the rotor 37 rotates, the optical probe 101 also rotates through the adapter 32, whereby the sample 103 is scanned. The rotor 37 is rotationally driven by a rotational drive device. Specifically, when the motor 33 rotates the roller 34, the rotor 37 whose outer periphery is in contact with the roller 34 is rotated.

  If the connector of the optical probe 101 is removed from the adapter 32, the rotating optical fiber 23 and the optical probe 101 can be attached and detached. The optical probe 101 is provided with a retaining ring 207 so that it can be attached to and detached from the exterior portion of the optical rotary joint 1. By removing the connector and retaining ring 207 of the optical probe 101, the optical probe 101 is attached to the optical rotary joint 1. Can be removed from. A cover 35 configured to be openable and closable via a hinge 36 is provided on the exterior of the optical rotary joint 1. The optical probe 101 is locked to the exterior portion of the optical rotary joint 1 with a retaining ring 207, and the user can open the lid portion 35 and remove the optical probe 101 from the connector portion. Therefore, when a failure or the like of the optical probe 101 occurs, only the optical probe 101 can be replaced.

  FIG. 3 and FIG. 4 show a configuration diagram of the optical probe 101 from the connector portion to the tip. The light propagated from the optical rotary joint to the optical probe 101 is transmitted to the core portion 201 of the optical fiber 200 and irradiated from the end surface of the core portion 201 on the side not connected to the optical rotary joint of the optical fiber 200. The end surface of the core portion 201 of the optical fiber 200 is, for example, an angle θ = 45 degrees (arbitrary within a range of 0 degree <θ <90 degrees, provided that the best angle of the end face that can reduce reflected light noise is about 8 degrees. In view of this, θ is not limited to 45 degrees and may be a smaller angle), and the reflected light generated at the end face of the optical fiber 200 does not return to the optical coherence tomographic image generation apparatus 102. Therefore, noise generated on the end face of the optical fiber 200 can be suppressed.

  The optical fiber 200 and a curved prism (which is a prism whose at least one optical surface is a curved surface, but hereinafter simply referred to as a prism) 203 constitute a light transmission device. A resin or glass prism 203 that is an optical element includes a first surface 203a that is in contact with the end surface of the core portion 201 of the optical fiber 200, a second surface 203b that reflects a light beam emitted from the end surface of the core portion 201 of the optical fiber 200, and And a third surface 203c that emits the light beam reflected by the second surface 203b. The second surface 203b has a curvature and is preferably an aspherical surface. Here, the first surface 203a is a plane in contact with the end surface of the core portion 201 of the optical fiber 200, and is also common to the third surface 203c. The prism 203 is formed by a mold (not shown) and then bonded to the end surface 201a of the optical fiber 200 with an adhesive. Since the first surface 203a of the prism 203 is in contact with the end surface of the optical fiber 200, the positioning of the optical fiber 200 and the prism 203 is sufficient only for phase alignment, and assembling is ensured.

  The second surface 203b may have a reflection function using total reflection, or a reflective film may be deposited. In addition, the irradiation direction of the light which propagated the core part 201 changes with the end surface of the core part 201 by making the refractive index of the core part 201 and the prism 203 of the optical fiber 200 different. By changing the light irradiation direction in this way, it is possible to have a suitable incident angle with respect to the second surface 203b of the prism 203. In the present embodiment, the refractive index of the prism 203 is larger than the refractive index of the core portion 201 of the optical fiber 200.

  The light irradiated from the end surface of the core portion 201 of the optical fiber 200 is irradiated into the prism 203 in front of the optical fiber 200, is reflected by the second surface 203b having the curved surface of the prism 203, and then passes through the third surface 203c. Then, after entering the clad portion 202 of the optical fiber 200 again, the light is irradiated from the side surface of the clad portion 202. At this time, if the refractive index of the prism 203 is set to the same level as that of the core portion 201 of the optical fiber 200, reflection noise generated at the boundary surface between the end surface of the core portion 201 and the prism 203 can be reduced.

  Thereafter, the light irradiated from the side surface of the cladding part 202 is collected outside the optical probe 101. At this time, since the side surface of the clad part 203 has a curved surface, the ratio of the reflected light generated at the side boundary of the clad part 202 returning to the optical coherence tomographic image generation device 102 is reduced, so that noise seen in the tomographic image is suppressed. be able to.

  The measurement light 105 that scans the sample 103 passes through the sheath 206 and is emitted from the side surface to the outside. Next, the measurement light 105 is scattered and reflected inside the living tissue, and the measurement light 105 returned to the optical probe 101 by the scattering is incident on the side surface of the optical fiber 200 via the sheath 206. Thereafter, the measuring light 105 is propagated to the prism 203, the optical fiber 200, the optical rotary joint 1, and the main body optical system.

  Here, the shape and size of the spot of the measurement light 105 collected outside the optical probe 101 are determined by the distance from the end surface of the core portion 201 of the optical fiber 200 to the second surface 203b of the prism 203 and the curvature of the second surface 203b. Determined. Since the measurement light 105 is affected by the curvature of the side surface when passing through the side surface of the cladding portion 202, the curvature of the mirror surface of the prism 203 is changed to the cladding portion 202 in order to form a focused spot with an optimum shape. It is necessary to provide a difference between the direction in which the curvature is affected and the vertical direction. Therefore, in the present embodiment, the second surface 203b has the following shape.

  Specifically, referring to FIG. 4, the end surface (emission point) of the core portion 201 of the optical fiber 200 is defined as the origin O, the direction of the center of the light beam incident on the prism 203 from the origin O is defined as the Z axis, and the optical fiber 200. The direction perpendicular to the Z axis in the plane including the axis of the core portion 201 and the Z axis is the Y axis, the direction perpendicular to the Z axis and the Y axis is the X axis, and the second surface 203b in the ZY plane is When the curvature is Py (1 / mm) and the curvature of the second surface 203b in the ZX plane is Px (1 / mm), Py <Px and 4 <Py <10, 5 <Px <20 Was made to hold. Further, when the distance from the origin O to the intersection P between the Z axis and the second surface 203b is Z0 (mm), Py <1 / Z0 <Px is established. Here, as an example, Px = 17.857, Py = 9.524, 1 / Z0 = 15.385.

  By providing the second surface 203b with such a shape, a spot of about 0.04 mm can be created at a position 0.1 mm away from the side surface of the optical probe by the measurement light 105 emitted from the optical probe 101. At this time, because of the relationship between the spot size and the confocal length, the optical probe 101 functions as a probe having a resolution of about 0.02 mm from the side surface of the optical probe 101 to 1 mm ahead. Suitable for observing faults in tubes.

  If the second surface 203b of the prism 203 has a spherical shape and a reflecting surface, the second surface 203b can direct the traveling direction of the light toward the sample 103 and can condense the light onto the sample 103 at the same time. An optical system. In particular, with the configuration shown in FIG. 4, the outer shape of the prism 203 is substantially equal to the outer diameter of the cladding portion 202 of the optical fiber 200, so that observation can be performed by inserting it into a thin blood vessel.

  The reflecting surface of the second surface 203b of the prism 203 may be totally reflected according to the refractive index of the optical element and the light bending direction, or may be a mirror surface obtained by depositing a metal film on the reflecting surface. It may be reflective. In particular, the second surface 203b is formed into an aspherical shape, and optical influences other than the optical fiber 200 and the prism 203 (such as aberration generated when the measurement light 105 passes through the cladding portion 202 and the sheath 206) are corrected. be able to.

  In manufacturing the optical probe 101 described above, a step of obliquely polishing the core portion 201 and the clad portion 202 of the optical fiber 200, a step of placing the prism 203 on the tip of the optical fiber 200, and a step of forming the curved surface of the prism 203 with a mold or the like. By using a process of curing a resin as a prism by ultraviolet irradiation or thermosetting, and a process of forming a mirror surface on a resin curved surface, a large number of optical probes can be manufactured simultaneously. In addition, since the manufacturing cost can be reduced as compared with an optical probe using a gradient index prism, a large amount of low-cost optical probes can be provided.

  A sheath 206 is provided on the outer periphery of the optical probe 101 so that the optical system of the optical probe 101 and the sample 103 come into contact to prevent damage to the optical probe 101 and the sample 103. The sheath 206 is a flexible tube that holds the optical fiber 200 and the prism 203 inside the optical probe 101 and is formed of a material having a high light transmittance such as Teflon (registered trademark). In particular, any material that can transmit low-coherence light with high efficiency may be used. In order to correct the aberration that occurs when the measurement light 105 passes through the sheath 206, the second surface 203b may be aspherical.

  The optical probe 101 having the configuration described so far is used by being inserted into a body lumen. Since the outer diameter of the optical probe 101 is about 0.5 mm to 3 mm, the size of the prism 203 is the diameter. The direction is preferably about 0.3 mm to 3 mm.

  A torque wire 205 is provided between the sheath 206 and the optical system in the optical probe 101. The torque wire 205 is an iron wire wound around the optical fiber 200, and prevents the optical system from being damaged due to the rotation by transmitting the rotational force transmitted from the rotor 37 to the connector portion to the tip of the optical probe 101. .

  The sheath 206 is bonded to a retaining ring 207, and the retaining ring 207 is fixed to the exterior portion of the optical rotary joint 1. The optical system of the optical probe 101 and the sheath 206 are not bonded. A stopper 209 is provided in front of the optical probe 101 so as not to damage the sample 103 and the optical probe 101.

  The optical probe 101 irradiates the measurement light 105 inside the living body while rotating around the axis of the optical fiber 200, and the measurement light 105 is emitted toward the living tissue positioned along the radial direction of the optical probe 101. Scanned. At this time, since the sheath 206 is fixed to the optical rotary joint 1 via the retaining ring 207 and does not rotate, the biological sample can be rotationally scanned non-invasively.

  FIG. 5 is a cross-sectional view similar to FIG. 4 showing a modification of the prism. In this modification, unlike the above-described embodiment, the refractive index of the prism 203 is smaller than the refractive index of the core portion 201 of the optical fiber 200. Therefore, the inclination of the end face of the optical fiber 200 is reversed from that of the above-described embodiment, and the light enters the second face 203b. The direction of inclination of the end face of the optical fiber 200 and the angle of inclination can be arbitrarily adjusted by selecting the refractive index of the prism 203 and the refractive index of the core portion 201 of the optical fiber 200. The second surface 203b of the prism 203 is an aspheric surface, and the third surface 203c is a toroidal surface. The measurement light 105 emitted from the end surface of the core portion 201 of the optical fiber 200 and incident from the first surface 203a is reflected by the second surface 203b, emitted from the third surface 203c, and passes through the cladding portion 202. There is no.

  As described above, in order to suppress the influence generated by other than the optical fiber 200 and the prism 203, a curvature can be given to the third surface 203c separately from making the second surface 203b spherical. In the case of this example, the influence of astigmatism generated by the transparent sheath 206 positioned outside the optical fiber 200 and the optical prism 203 can be corrected by the toroidal shape of the third surface 203c.

  FIG. 6 is a cross-sectional view similar to FIG. 4 showing another modification of the prism. In this modification, the second surface 203b of the prism 203 is a flat surface, and the third surface 203c is an aspherical surface.

  FIG. 7 is a cross-sectional view similar to FIG. 4 showing another modification of the prism. In this modification, the second surface 203b of the prism 203 is a spherical surface or an aspherical surface, and the third surface 203c is a flat surface, but the measuring beam 105 is inclined at an angle with respect to the normal line of the third surface 203c. It comes out. Thereby, since the light reflected by the third surface 203c deviates from the optical axis, the influence of the reflected light returning directly into the core part 201 of the optical fiber 200 can be reduced.

  The present invention is not limited to the embodiments described in the specification, and other embodiments and modifications are apparent to those skilled in the art from the embodiments and ideas described in the present specification. It is. For example, the optical fiber used in the present invention is preferably a single mode, but a fiber to which the effect of the present invention for reducing reflection noise can be applied includes a multimode fiber.

DESCRIPTION OF SYMBOLS 1 Optical rotary joint 2 Low coherence light source 3 Interference light detection part 4 Light splitting means (it also serves as an optical multiplexing means)
5 Image processing unit 6 Lens unit 7 Mirror 8 Optical path length adjustment unit 9 Control unit 10 Control synchronization unit 11 Display device 31 Connector 32 Adapter 33 Motor 34 Roller 35 Lid 36 Hinge 37 Rotor 101 Optical probe 102 Tomographic image generation device 103 Sample 104 Tomographic image 105 Measuring light
200 optical fiber 201 core portion 202 clad portion 203 prism 203a first surface 203b second surface 203c third surface 204 tomographic image 205 torque wire 206 sheath 207 retaining ring 208 connector 209 plug

Claims (11)

In an optical transmission device composed of at least one optical fiber having a core part and a clad part, and an optical element provided at the end of the optical fiber,
The tip of the optical fiber has an end face that is inclined at a predetermined angle θ (O degrees <θ <90 degrees) with respect to the axial direction of the optical fiber,
The optical element includes a first surface that is in contact with an end surface of the optical fiber, a second surface that reflects a light beam emitted from the end surface of the optical fiber and incident from the first surface, and a light beam reflected by the second surface. And a third surface that emits light, and the irradiation light emitted from the third surface is irradiated onto the observation target.   The optical transmission device according to claim 1, wherein at least one of the second surface and the third surface of the optical element has a curvature.   3. The light transmission device according to claim 1, wherein at least one of the second surface and the third surface of the optical element has an aspherical shape.   4. The optical transmission device according to claim 1, wherein a refractive index of a core portion in the optical fiber is different from a refractive index of the optical component.   The optical transmission device according to claim 1, wherein the optical element is manufactured by molding. Irradiation light emitted from the third surface of the optical element is further incident on the cladding portion of the optical fiber, and then emitted from the side surface of the optical fiber,
The origin of the optical fiber is the origin, the direction of the center of the light beam incident on the optical element from the origin is the Z axis, and is orthogonal to the Z axis in a plane including the axis of the optical fiber and the Z axis. The direction is the Y axis, the direction orthogonal to the Z axis and the Y axis is the X axis, the curvature of the second surface in the ZY plane is Py (1 / mm), and the second surface in the ZX plane 6. Py <Px and 4 <Py <10 and 5 <Px <20 are satisfied, where Px (1 / mm) is the curvature of the above. Light transmission device.   7. The light transmission according to claim 6, wherein Py <1 / Z0 <Px is established when a distance from the origin to the intersection of the Z axis and the second surface is Z0 (mm). apparatus.   The optical transmission device according to claim 1, wherein the focus position of the optical element is about 0.1 mm away from the axis of the optical fiber, and the spot size is about 0.04 mm.   The light transmission device according to claim 1, wherein the first surface is common to the third surface.   The optical transmission device according to claim 1, wherein the optical transmission device is used in an optical coherence tomographic image forming apparatus.   11. An optical element that is used in the light transmission device according to claim 1 and has a first surface that is attached to an end surface of the optical fiber.

Images