JP6647700B2 - Interferometer - Google Patents

Description

  The present invention relates to an interferometer mainly used for an optical interference measuring device that measures an object using optical interference.

  2. Description of the Related Art Conventionally, there has been provided an optical interference measuring apparatus for measuring a test object using optical interference. The optical interference measuring device employs an optical fiber for the configuration of an interferometer that generates interference light as disclosed in Patent Document 1 because of the high degree of freedom in the arrangement of optical components and the compact configuration even with a long optical path length. Often do.

  In Patent Literature 1, light output from a wavelength-swept light source is guided to a first coupler via an optical fiber to be divided into measurement light and reference light, and the divided measurement light is transmitted through an optical fiber. The measurement light reflected from the eye to be inspected is guided to the second coupler via the first coupler, and the reference light split by the first coupler is converted to the second light via the optical fiber. Ophthalmologic apparatus for identifying the position of each part inside the eye to be inspected by detecting with a detector an interference light generated by combining the measurement light and the reference light guided to the second coupler and guided to the second coupler Is disclosed.

JP-A-2015-21732

  In an interferometer using an optical fiber, when the light propagates in the optical fiber, part of the light is scattered and scattered light is generated. For example, in the ophthalmologic apparatus disclosed in Patent Document 1, of the scattered light generated in the optical fiber through which the reference light passes, backscattered light scattered backward enters the measurement optical path via the first coupler, As a result, the interference light generated by the second coupler is affected, and it may not be possible to accurately specify the position of each part inside the eye to be inspected.

  In particular, in the reference optical path from the first coupler to the second coupler, from the first coupler to the optical path length from the first coupler to the second coupler in the reference optical path to the second coupler from the first coupler in the measurement optical path. Since the backscattered light of the reference light and the reference light generated at a position １ ／ of the optical path length obtained by subtracting the optical path length to the coupler strongly interfere with the reference light, it is necessary to suppress the backscattered light from the position.

  In view of the circumstances described above, the present invention is an interferometer having a reference optical path and a measurement optical path, and can suppress backscattered light generated in the optical fiber of the reference optical path from entering the measurement optical path. The task is to provide things.

In order to solve the problem, according to one aspect of the present invention, a first light splitting unit that splits light emitted from a light source into measurement light and reference light,
The measurement light emitted from the first light branching portion, which is irradiated on the test object and then reflected by the test object, and the reference light emitted from the first light branching portion are multiplexed. A second optical branching unit for generating interference light,
A first optical fiber that connects the first and second optical splitters to each other in order to guide the measurement light emitted from the first optical splitter to the second optical splitter; And having a measurement optical path length X;
A reference optical path connecting the first and second optical splitters to each other to guide the reference light emitted from the first optical splitter to the second optical splitter, and using a second optical fiber; And having a reference optical path length Y;
A balance detector that receives the generated interference light and differentially amplifies the interference light.
While the reference light propagates in the reference light path from the first light branching portion toward the second light branching portion, backscattered light is generated in a direction opposite to the propagation direction,
The measurement light path and the reference light path use a predetermined relationship between the measurement light path length X and the reference light path length Y, so that the backscattered light generated in the reference light path is the first light path. It is configured to suppress entering into the measurement optical path via an optical branching unit ,
Further, there is provided an interferometer including an optical path length changer that changes an optical path length of the reference light as a selected measurement target portion of the test object moves in a depth direction of the test object .
An example of the interferometer may further include a calculation device that specifies a position in a depth direction of each part of the test object based on the interference signal input from the balance detector .
According to another aspect of the present invention, the first light splitting unit splits light emitted from the light source into measurement light and reference light, and the measurement light emitted from the first light splitting unit is After being irradiated on the test object, reflected by the test object, returned to the first optical branching section, and emitted from the first optical branching section;
A second light branching unit that combines the measurement light emitted from the first light branching unit after being reflected by the test object and the reference light emitted from the first light branching unit to generate interference light When,
An optical fiber connecting the first and second optical splitters to each other to guide the reference light emitted from the first optical splitter to the second optical splitter;
And an optical element connected to the optical fiber.
The optical element is configured such that a length of a measurement optical path from the first optical branching section to the second optical branching section through which the measuring light passes through a path different from the optical fiber is X. When the length of the reference light path from the first optical branching section to the second optical branching section via the optical fiber is Y, the reference light is represented by (YX) / 2. An interferometer connected at a distance from the first optical branch to the second optical branch by a distance not exceeding a predetermined value.
According to still another aspect of the present invention, there is provided an interferometer, wherein light output from a light source is guided to a first optical branching unit to be divided into measurement light and reference light. Is irradiated on the test object, the measurement light reflected from the test object is guided to the second light splitting unit via the first light splitting unit, and the reference light split by the first light splitting unit is converted into light. In the interferometer, which is guided to the second optical branching unit via the fiber, and the measurement light and the reference light guided to the second optical branching unit are combined to generate interference light, the reference light is converted to the first light. Provided with a backscattered light removing unit on the path from the optical branching unit to the second optical branching unit via the optical fiber.

  ADVANTAGE OF THE INVENTION According to this invention, in the reference optical path which comprises at least one part with an optical fiber, it can suppress that the backscattered light scattered backward among the scattered lights produced in the optical fiber enters into the measurement optical path.

1 is a schematic configuration diagram of an optical system of an ophthalmologic apparatus using an interferometer according to a first embodiment of the present invention. FIG. 2 is a block diagram of a control system of the ophthalmologic apparatus employing the interferometer according to the first embodiment of the present invention. 5 is a flowchart illustrating an example of a processing procedure of the ophthalmologic apparatus according to the first embodiment. FIG. 4 is a diagram illustrating a procedure for performing Fourier transform on an interference signal detected by an interference optical system to specify a target portion of an eye to be inspected. It is a figure for explaining the function of a zero point adjustment mechanism. It is a schematic structure figure of an optical system of an ophthalmologic apparatus which adopted an interferometer of a 2nd embodiment concerning the present invention. It is a schematic structure figure of an optical system of an ophthalmologic apparatus which adopted an interferometer of a 3rd embodiment concerning the present invention.

[First Embodiment]
Hereinafter, an ophthalmologic apparatus 1 using an interferometer 100 according to a first embodiment of the present invention will be described with reference to the drawings. In the present embodiment, an ophthalmologic apparatus that specifies the position of a measurement target portion (for example, a crystalline lens, a retina, or the like) inside an eye to be inspected by using optical interference will be described in detail. However, the present invention is not limited to the ophthalmologic apparatus as described above, and any optical interference measuring apparatus that measures an object using optical interference can be employed.

  FIG. 1 is a diagram illustrating a schematic configuration of an optical system of the ophthalmologic apparatus 1. As shown in FIG. 1, an optical system 10 of the ophthalmologic apparatus 1 includes an optical interference optical system 20 that causes measurement light reflected from the eye E to interfere with reference light, and observation for observing an anterior eye of the eye E. The optical system 50 (shown in FIG. 2), the XYZ alignment optical system 60 (shown in FIG. 2) for aligning the optical system 10 with the eye E in a predetermined positional relationship, and the eye E are fixed. It comprises a fixation optical system (not shown) and the like. As the observation optical system 50, the XYZ alignment optical system 60, and the fixation optical system, those used in a known ophthalmic apparatus can be used, and thus detailed description thereof will be omitted. Here, as shown in FIG. 1, an interferometer 100 according to the first embodiment of the present invention including a balance detector 120 is referred to as an optical interference optical system 20.

  The light interference optical system 20 irradiates the inside of the eye E with the light source 101 and one of the lights split from the light source 101 by the beam splitter 102 as measurement light, and reflects the reflected light (measurement light) into the beam splitter 102. And a reference optical system that guides the light from the light source 101 to the beam splitter 103 as reference light, and a reference optical system that guides the other light branched by the beam splitter 102 to the beam splitter 103 via the beam splitter 103. It comprises a balance detector 120 for receiving interference light generated by multiplexing the measurement light and the reference light by the beam splitter 103.

  The light source 101 is a wavelength-swept light source, and the wavelength of emitted light changes at a predetermined cycle. When the wavelength of the light emitted from the light source 101 changes, the intensity of the interference light between the light reflected from each part of the eye E and the reference light changes in accordance with the wavelength of the emitted light. The frequency of the intensity change depends on the position in the depth direction of the reflection position of the reflected light. Therefore, by measuring the interference light while changing the wavelength of the emitted light, it is possible to specify the position of each part (that is, the cornea E0, the lens E1, and the retina E2) inside the eye E to be examined. Become.

  The measurement optical system includes a beam splitter 102, an objective lens 108, a collimator lens 109, an optical fiber 105, a collimator lens 113, and a beam splitter 103. The light emitted from the light source 101 is applied to the eye E via the objective lens 108 with the reflected light branched by the beam splitter 102 as measurement light. The measurement light reflected from the subject's eye E enters the beam splitter 102 again, and the transmitted measurement light is guided to the beam splitter 103 via the collimator lens 109, the optical fiber 105, and the collimator lens 113.

  The reference optical system includes a beam splitter 102, a collimator lens 110, an optical fiber 106, a collimator lens 111, a zero-point adjustment mechanism 30, a collimator lens 112, an optical fiber 107, a collimator lens 114, and a beam splitter 103. And is constituted by. The light emitted from the light source 101 is a collimator lens 110, an optical fiber 106, a collimator lens 111, a zero-point adjustment mechanism 30, a collimator lens 112, an optical fiber 107, and a collimator lens, using the transmitted light branched by the beam splitter 102 as reference light. The light is guided to the beam splitter 103 via 114.

  The measurement light and the reference light guided to the beam splitter 103 are combined in the beam splitter 103, and the generated interference light is detected for balance through the collimator lens 115 and the optical fiber 117 and the collimator lens 116 and the optical fiber 118. It is led to the vessel 120. The interference light guided to the balance detector 120 is differentially amplified in the balance detector 120 and input to the arithmetic unit 80. In the present embodiment, the balance detector 120 is used for detecting the interference light, but the detection of the interference light is not limited to this. For example, a photodiode can be used.

  Next, the zero-point adjusting mechanism 30 provided in the reference optical system will be described. The zero-point adjusting mechanism 30 includes a corner cube 104 and a first driving device 81 (shown in FIG. 2) that moves the corner cube 104 forward and backward with respect to the collimator lenses 111 and 112. The first drive device 81 drives the corner cube 104 in the direction of arrow A in FIG. 1 to change the optical path length from the beam splitter 102 to the beam splitter 103 (that is, the reference optical path length of the reference optical system). The zero point described here is, as shown in FIG. 5, the reference optical path length (specifically, the beam splitter 102 to the zero point adjustment mechanism 30 to the beam splitter 103) and the measurement optical path length (specifically, the beam splitter 102 to This is a position where point 0 to the beam splitter 102 to beam splitter 103) coincide with each other. In a measuring apparatus using interference light, the interference in the depth direction (in this embodiment, the direction of the retina E2 of the eye E to be examined) is based on the point 0. Get the signal. That is, as shown in FIG. 5, when the optical path length from the beam splitter 102 to the beam splitter 103 in the measurement optical path is X, and the optical path length from the beam splitter 102 to the zero point is d, the measurement optical path length is 2d + X. Since the reference optical path length is Y, in FIG. 5, Y = 2d + X.

  When the measurement from the cornea E0 to the retina E2 of the eye E is performed as in the present embodiment, usually, as shown in FIG. 5, a position slightly before the cornea E0 of the eye E (the eye to be inspected shown in FIG. 5). The position is adjusted by the zero point adjusting mechanism 30 so that the zero point comes to the position (ΔZ forward from E). Note that the zero point adjustment mechanism 30 in the present embodiment is configured so that the position of the zero point can be moved by the distance from the surface of the cornea E0 to the surface of the retina E2.

  Next, the configuration of the control system of the ophthalmologic apparatus 1 of the present embodiment will be described. As shown in FIG. 2, the ophthalmologic apparatus 1 is controlled by the arithmetic unit 80. The arithmetic unit 80 is configured by a microcomputer (microprocessor) including a CPU (not shown), a ROM, a RAM, and the like. The arithmetic unit 80 includes an optical interference optical system 20, an observation optical system 50, an XYZ alignment optical system 60, a fixation optical system (not shown), a first driving device 81, a monitor 5, a memory 6, , And the joystick 7 are connected. The arithmetic unit 80 controls ON / OFF of the light source (light source 101 and the like) of each optical system of the optical interference optical system 20, the observation optical system 50, the XYZ alignment optical system 60, and the fixation optical system (not shown). The first driving device 81 that drives the point adjustment mechanism 30 is controlled. Further, the observation optical system 50 is controlled to display an image of the anterior segment of the eye E to be inspected, which is captured by the observation optical system 50, on the monitor 5. Further, the arithmetic unit 80 is connected to the balance detector 120 of the optical interference optical system 20, and receives an interference signal corresponding to the intensity of the interference light detected by the balance detector 120. The arithmetic unit 80 specifies the position of each part of the eye E (the front and back surfaces of the cornea E0, the front and back surfaces of the crystalline lens E1, and the surface of the retina E2) by Fourier transforming the interference signal input from the balance detector 120. Then, the axial length of the eye E is calculated.

  Next, a procedure for specifying the position of each part of the eye E and measuring the eye size using the ophthalmologic apparatus 1 of the present embodiment will be described with reference to FIG. FIG. 3 is a flowchart illustrating an example of a processing procedure of the ophthalmologic apparatus 1 of the present embodiment.

  First, in step S10, XYZ alignment for aligning the optical system 10 with the eye E to be inspected in a predetermined positional relationship is performed. The XYZ alignment is performed using the XYZ alignment optical system 60. First, the joystick 7 is operated to roughly align the optical system 10 with the eye E to be inspected. Thereafter, based on a detection signal output from the XYZ alignment optical system 60, an X-axis driving device and a Y-axis driving device (not shown) The optical system 10 is automatically aligned in the XYZ directions with respect to the eye E by the Z-axis driving device.

  Next, in step S11, the zero point position is adjusted. As described above, the zero-point position is adjusted by controlling the zero-point adjustment mechanism 30 so that the zero-point position is located at a position in front of the subject's eye E by ΔZ. After that, the measurement of the eye E is started.

  In step S12, an interference signal of the eye E is acquired. As described above, the interference signal of the eye E is detected by the balance detector 120 of the light interference optical system 20, and is input to the arithmetic unit 80.

  In step S13, the interference signal input to the arithmetic unit 80 is Fourier-transformed. Then, in step S14, the target site (for example, cornea E0, crystalline lens E1, retina E2, etc.) of the eye E to be examined is specified from the Fourier-transformed data (referred to as “A-scan image”), Then, in step S15, each eye dimension value calculated in step S14 is displayed on the display screen of the monitor 5. FIG. 4 is a diagram showing a procedure for specifying a target site (for example, cornea E0, crystalline lens E1, retina E2, etc.) of eye E by subjecting the interference signal detected by balance detector 120 to Fourier transform.

  Here, in the optical interference optical system 20 according to the present embodiment, as described above, since the optical fiber 106 and the optical fiber 107 are used in the reference optical path, when the reference light propagates in the optical fiber, Part of the reference light propagating in the optical fiber is scattered to generate scattered light. Of the scattered light generated in the optical fiber through which the reference light passes, the backscattered light scattered backward enters the measurement optical path via the beam splitter 102, and as a result, affects the interference light generated by the beam splitter 103. However, there is a possibility that the position of each part inside the eye E cannot be specified accurately.

  As shown in FIG. 1, the optical path length from the beam splitter 102 to the beam splitter 103 in the measurement optical system is X, and the optical path length from the beam splitter 102 to the beam splitter 103 via the zero point adjustment mechanism 30 in the reference optical system. Is Y, the position (P1) of (Y−X) / 2 from the beam splitter 102 to the beam splitter 103 in the reference optical path is the same as the position of the zero point in the measurement optical system. When the backscattered light of the reference light generated in the optical fiber enters the measurement optical path via the beam splitter 102, it greatly affects the interference light generated by the beam splitter 103. That is, it is important to suppress backscattered light generated at the position P1 in the reference light path. In the present embodiment, as shown in FIG. 1, the backscattered light is generated at the position of P1 by arranging the zero-point adjusting mechanism 30 composed of a free space (not using an optical fiber) at the position of P1. Can be suppressed. Accordingly, the influence of the backscattered light in the interference light generated by the beam splitter 103 can be suppressed, so that the position of each part inside the eye E can be accurately specified.

[Second embodiment]
Next, an ophthalmologic apparatus 2 using an interferometer 200 according to a second embodiment of the present invention will be described with reference to the drawings.

  FIG. 6 is a schematic configuration diagram of the optical system 11 of the ophthalmologic apparatus 2 employing the interferometer 200 according to the second embodiment of the present invention. In the interferometer 200, an optical isolator 130 is disposed between an optical fiber 131 and an optical fiber 132 on a reference optical path from the beam splitter 102 to the beam splitter 103. The optical isolator 130 is an optical element having a characteristic of transmitting light traveling in one direction and blocking light traveling in the opposite direction. In the present embodiment, the optical isolator 130 is arranged so that reference light traveling from the beam splitter 102 to the beam splitter 103 is transmitted, and conversely, reference light traveling from the beam splitter 103 to the beam splitter 102 is blocked. As shown in FIG. 6, when the optical path length from the beam splitter 102 to the beam splitter 103 in the measurement optical system is X, and the optical path length from the beam splitter 102 to the beam splitter 103 in the reference optical system is Y, the reference optical path The optical isolator 130 is disposed at a position not exceeding the position (P2) of (YX) / 2 from the beam splitter 102 to the beam splitter 103 in FIG. As a result, the backscattered light generated in the optical fiber 132 including the position of P2 which is the same as the position of the zero point in the measurement optical system is blocked by the optical isolator 130, so that the light is transmitted to the measurement optical path via the beam splitter 102. Intrusion can be suppressed. That is, it is possible to suppress the influence of the backscattered light generated at the position P2 where the influence is particularly large in the interference light generated by the beam splitter 103. Therefore, the position of each part inside the eye E can be accurately specified. Will be able to

[Third Embodiment]
Next, an ophthalmologic apparatus 3 using an interferometer 300 according to a third embodiment of the present invention will be described with reference to the drawings.

  FIG. 7 is a schematic configuration diagram of the optical system 12 of the ophthalmologic apparatus 3 employing the interferometer 300 according to the third embodiment of the present invention. In the above-described first and second embodiments, the beam splitters 102 and 103 are employed as branch members for splitting light. However, as shown in FIG. 7, in the interferometer 300, instead of the beam splitters 102 and 103, The fiber couplers 201 and 202 are adopted. When an interferometer is configured using an optical fiber as in the ophthalmologic apparatus according to the present invention, the interferometer can be easily assembled by using a fiber coupler in the optical branching unit as in the interferometer 300.

  Here, the interferometers 100, 200, and 300 are examples of an interferometer, the light source 101 is an example of a light source, the beam splitter 102 and the fiber coupler 201 are examples of a first optical splitter, and the beam splitter 103 The fiber coupler 202 is an example of a second optical branching unit, the zero point adjustment mechanism 30 is an example of a free space, and the optical isolator 130 is an example of an optical element.

  As described above, the embodiments of the present invention have been described in detail. However, these are merely examples, and the present invention is not to be construed as being limited in any way by the specific description in the embodiments, and is not limited to those skilled in the art. Various changes, modifications, improvements, and the like can be performed based on knowledge, and any such embodiments are within the scope of the present invention unless departing from the spirit of the present invention. Should be understood to be included in

  For example, in the interferometers 100, 200, and 300 of the above embodiment, the light source 101, which is one of Fourier-domain optical coherence tomography (hereinafter referred to as “OCT”), has a wavelength-swept light source. In this case, SS-OCT using the above is adopted. However, the interferometer according to the present invention is not limited to the SS-OCT, but may be a spectrum domain OCT (SD-OCT), which is another Fourier domain type OCT, or a time domain type OCT. You may.

  In the interferometer 200 according to the second embodiment, the optical isolator 130 is employed, but the optical element that is disposed in the reference optical path and blocks backscattered light generated in the optical fiber is limited to the optical isolator. Instead, an optical attenuator or an optical circulator may be employed.

  In addition, at least one of the two optical branching units may be configured with an optical fiber. As in the first embodiment, when a part of the optical system of the interferometer is configured with free space, the optical branching section can be simply configured without using an optical fiber. Can be inexpensive.

  In the interferometer 100 according to the first embodiment, the zero-point adjusting mechanism 30 is arranged at the position P1, but the scope of the present invention is not limited to the configuration in which the zero-point adjusting mechanism is arranged. , P1 may be provided with another mechanism in which a predetermined range around the position becomes a free space.

  In addition, since the light interference generated by the beam splitter 103 occurs in a range of a coherent length (square of the wavelength of the light source ÷ the line width of the light source) from the point 0, a predetermined range is set as the coherent length of the light source 101. Thereby, a free space can be provided at an appropriate position. This makes it possible to more effectively suppress the influence of the backscattered light of the reference light. Note that the predetermined range is not limited to the coherent length of the light source 101, and the position and the range may be appropriately set according to the backscattered light to be suppressed.

  In the interferometers 100, 200, and 300 of the above-described embodiments, an optical fiber is used for the optical path from the beam splitter 102 to the beam splitter 103 in the measurement optical path. However, depending on the configuration of the measurement optical path, an optical fiber is particularly used. If unnecessary, an optical path from the beam splitter 102 to the beam splitter 103 may be configured in free space.

1, 2, 3, ophthalmic apparatus 5, monitor 10, 11, 12, optical system 20, optical interference optical system 30, zero-point adjustment mechanism 50, observation optical system 60, XYZ alignment optical system 100 , 200, 300, interferometer 101, light sources 102, 103, beam splitter 120, balance detectors 201, 202, fiber coupler

Claims (2)

A first light splitting unit that splits light emitted from the light source into measurement light and reference light,
The measurement light emitted from the first light branching portion, which is irradiated on the test object and then reflected by the test object, and the reference light emitted from the first light branching portion are multiplexed. A second optical branching unit for generating interference light,
A first optical fiber that connects the first and second optical splitters to each other in order to guide the measurement light emitted from the first optical splitter to the second optical splitter; And having a measurement optical path length X;
A reference optical path connecting the first and second optical splitters to each other to guide the reference light emitted from the first optical splitter to the second optical splitter, and using a second optical fiber; And having a reference optical path length Y;
A balance detector that receives the generated interference light and differentially amplifies the interference light.
While the reference light propagates in the reference light path from the first light branching portion toward the second light branching portion, backscattered light is generated in a direction opposite to the direction,
The measurement light path and the reference light path use a predetermined relationship between the measurement light path length X and the reference light path length Y, so that the backscattered light generated in the reference light path is the first light path. It is configured to suppress entering into the measurement optical path via an optical branching unit ,
Furthermore, an interferometer including an optical path length changer that changes an optical path length of the reference light as a selected measurement target portion of the test object moves in a depth direction of the test object . The interferometer according to claim 1, further comprising a calculation device that specifies a position in a depth direction of each part of the test object based on an interference signal input from the balance detector .