Ultrasonic tonometer and ophthalmic ultrasonic actuator

Abstract

An ultrasonic actuator 10 has ultrasonic elements 11A,11B and irradiates an eye under inspection with ultrasonic waves. The ultrasonic actuator 10 comprises a sonotrode 20, a flexible vibration section 22, and a reflection section 50. The sonotrode 20 causes ultrasonic waves generated by the ultrasonic elements 11A,11B to propagate through the air. The flexible vibration section 22 is provided on the axial leading-end side of the sonotrode 20 and flexes and vibrates in accordance with ultrasonic vibrations of the sonotrode 20. The reflection section 50 covers at least a circumferential portion of the flexible vibration section 22 in a state of forming a gap between the reflection section 50 and the flexible vibration section 22, thereby reflecting ultrasonic waves generated from the flexible vibration section 22 and guiding the irradiation direction of the ultrasonic waves of the ultrasonic actuator 10 toward the leading end side in the axial direction.

Description

Ultrasonic tonometer and ophthalmic ultrasonic actuator

[0001] The present disclosure relates to an ultrasonic tonometer that measures the intraocular pressure of a subject's eye using ultrasonic waves, and an ophthalmic ultrasonic actuator used in an ophthalmic device such as an ultrasonic tonometer.

[0002] The most common type of non-contact tonometer is the air-injection tonometer, which measures intraocular pressure based on the deformation of the cornea when air is injected onto the cornea and the pressure of the air injected onto the cornea.

[0003] Furthermore, ultrasonic tonometers that measure intraocular pressure using ultrasound have been proposed as non-contact tonometers. For example, the ultrasonic tonometer described in Patent Document 1 measures intraocular pressure based on the deformation state of the cornea when ultrasound is radiated onto the cornea and the radiation pressure emitted onto the cornea. The ultrasonic tonometer described in Patent Document 2 measures the intraocular pressure of the subject's eye based on the relationship between the characteristics (phase, amplitude) of the wave reflected from the cornea and the intraocular pressure.

[0004] JP 5-253190 JP 2009-268651

[0005] Ophthalmic devices that use ultrasound to measure characteristics of a subject's eye, etc., require the subject's eye to be irradiated with ultrasound of sufficient output. For example, to measure the intraocular pressure of a subject's eye using ultrasound, it is necessary to irradiate the subject's eye with ultrasound of very high output. However, despite various studies, the present applicant has not yet achieved irradiation of ultrasound of sufficient output. For example, some ultrasonic actuators include an actuator equipped with a flexural vibration portion at the axial tip of a sonotrode that propagates ultrasound through the air. Ultrasonic actuators equipped with a flexural vibration portion may be able to irradiate ultrasound of a subject's eye with higher output than ultrasonic actuators without a flexural vibration portion. However, simply employing an ultrasonic actuator equipped with a flexural vibration portion has not been able to achieve irradiation of ultrasound of sufficient output. Therefore, a technology capable of emitting ultrasound to a subject's eye with higher efficiency is desired.

[0006] A typical object of the present invention is to provide an ultrasonic tonometer and an ophthalmic ultrasonic actuator that are capable of emitting ultrasonic waves to an eye to be examined with high efficiency.

[0007] An ultrasonic tonometer provided by a typical embodiment of the present disclosure is an ultrasonic tonometer that measures the intraocular pressure of a test eye using ultrasound, and includes an ultrasonic element and an ultrasonic actuator that irradiates the test eye with ultrasound. The ultrasonic actuator includes a sonotrode that propagates ultrasound generated by the ultrasonic element into the air, a flexible vibration section that is provided at the axial tip side of the sonotrode and flexurally vibrates in response to the ultrasonic vibration of the sonotrode, and a reflecting section that covers at least a portion of the circumferential direction of the flexible vibration section while forming a gap between itself and the flexible vibration section, thereby reflecting at least a portion of the ultrasound generated from the flexible vibration section and guiding the direction of ultrasound irradiation by the ultrasonic actuator toward the axial tip side.

[0008] An ophthalmic ultrasonic actuator provided by a typical embodiment of the present disclosure is an ophthalmic ultrasonic actuator used in an ophthalmic device that irradiates an ultrasonic wave to an eye to be examined, and includes an ultrasonic element that generates ultrasonic waves, a sonotrode that propagates the ultrasonic waves generated by the ultrasonic element into the air, a flexural vibration section that is provided at the axial tip side of the sonotrode and flexurally vibrates in response to the ultrasonic vibration of the sonotrode, and a reflecting section that covers at least a portion of the circumferential direction of the flexural vibration section while forming a gap between itself and the flexural vibration section, thereby reflecting at least a portion of the ultrasonic waves generated from the flexural vibration section and guiding the direction of irradiation of the ultrasonic waves by the ultrasonic actuator toward the axial tip side.

[0009] According to the ultrasonic tonometer and ophthalmic ultrasonic actuator of the present disclosure, ultrasonic waves can be easily emitted to the subject's eye with high efficiency.

[0010] The ultrasonic tonometer exemplified in the present disclosure measures the intraocular pressure of a subject's eye using ultrasound. The ultrasonic tonometer includes an ultrasonic actuator. The ultrasonic actuator has an ultrasonic element and irradiates the subject's eye with ultrasound. The ultrasonic actuator of the present disclosure includes a sonotrode, a flexural vibration portion, and a reflecting portion. The sonotrode propagates ultrasound generated by the ultrasonic element into the air. The flexural vibration portion is provided on the axial tip side of the sonotrode and flexurally vibrates in response to ultrasonic vibration of the sonotrode. The reflecting portion covers at least a portion of the circumferential direction of the flexural vibration portion while forming a gap between itself and the flexural vibration portion, thereby reflecting the ultrasound generated from the flexural vibration portion and guiding the direction of ultrasound irradiation by the ultrasonic actuator toward the axial tip side.

[0011] According to the ultrasonic tonometer and ultrasonic actuator of the present disclosure, ultrasonic waves propagating from the deflection vibration unit in a direction different from the axial tip side are reflected by the reflecting unit and easily guided toward the axial tip side, which makes it easier for the ultrasonic waves generated by the ultrasonic actuator to be emitted to the test eye with high efficiency.

[0012] The reflecting portion may cover the entire circumferential circumference of the flexible vibration portion. In this case, ultrasonic waves are more easily guided toward the axial tip end over the entire circumferential circumference, which further improves the efficiency of ultrasonic wave emission toward the test eye. However, the reflecting portion may cover only a portion of the circumferential circumference of the flexible vibration portion (for example, only above, only below, only to the side, or only above and below the sonotrode as viewed from the test eye). Even in this case, ultrasonic waves propagating from the flexible vibration portion to the surrounding area are more easily guided appropriately toward the test eye by the reflecting portion.

[0013] When a reflecting portion is provided around the entire circumference of the flexible vibration portion, it is more desirable that a gap between the flexible vibration portion and the reflecting portion be provided around the entire circumference of the flexible vibration portion. In this case, ultrasonic waves propagating to the rear end of the flexible vibration portion are more easily guided toward the tip end through the gap provided around the entire circumference. Therefore, ultrasonic waves are more easily emitted to the subject's eye with higher efficiency. However, the flexible vibration portion and the reflecting portion may be in contact with each other at a portion of the circumference of the flexible vibration portion. For example, a mesh-like member may be provided between the flexible vibration portion and the reflecting portion to reduce the possibility of foreign matter entering the gap. Even in this case, ultrasonic waves are more easily guided toward the tip end by the reflecting portion.

[0014] The specific configuration of the bending vibration unit can be selected as appropriate. For example, the bending vibration unit and the sonotrode may be formed as a single unit. In this case, a portion of the sonotrode's main body, which has a columnar (e.g., cylindrical) outer shape, slightly proximal to the tip may be cut out in an annular shape, and the portion remaining distal to the cutout may serve as the bending vibration unit. In this case, a sonotrode equipped with a bending vibration unit can be appropriately manufactured from a single member. Note that the shape of the cutout portion when viewed in a cross section including the axis of the sonotrode may be formed in an arc or elliptical arc shape. In this case, higher-output ultrasonic waves are more likely to be emitted toward the tip in the axial direction. Alternatively, the bending vibration unit and the sonotrode may be separate members. The bending vibration unit may be fixed to the tip of the sonotrode with a fixing member such as a screw. Even in this case, the bending vibration of the bending vibration unit makes it easier to emit high-output ultrasonic waves.

[0015] The ultrasonic actuator may be a Langevin transducer. The Langevin transducer may include an ultrasonic element, a sonotrode (sometimes called a horn or front mass), and a back mass. The ultrasonic element generates ultrasonic waves. As described above, the sonotrode propagates the ultrasonic waves generated by the ultrasonic element through the air. The sonotrode is a mass member located at the axial tip end (toward the subject's eye) of the ultrasonic element. The back mass is a mass member located at the axial rear end of the ultrasonic element. The sonotrode and back mass may be tightened toward each other with the ultrasonic element disposed therebetween. A Langevin transducer can generate ultrasonic waves with reduced mechanical and thermal energy loss, thereby generating ultrasonic waves with high output. However, the reflecting portion exemplified in this disclosure can be used in various ultrasonic actuators equipped with a flexible vibration portion. In other words, the reflecting portion exemplified in this disclosure can also be applied to ultrasonic actuators other than Langevin transducers.

[0016] The material of the reflector can be selected as appropriate, but it is desirable to use a material that has as large a difference in acoustic impedance as possible from air. For example, aluminum or resin can be used as the material of the reflector.

[0017] The axial tip of the reflecting portion may protrude further toward the tip than the axial tip of the flexible vibration portion. In this case, at least a portion of the ultrasonic waves propagating in the diagonal tip direction as viewed from the flexible vibration portion is also reflected by the inner circumferential surface of the reflecting portion and emitted toward the subject's eye. Therefore, the ultrasonic waves generated by the ultrasonic actuator can be more efficiently emitted toward the subject's eye.

[0018] However, it is sufficient that the reflecting portion is provided so as to cover at least the rear end side from the position of the flexible vibration portion in the axial direction of the sonotrode. In other words, regardless of whether the reflecting portion protrudes further forward than the axial tip of the flexible vibration portion, as long as the reflecting portion is provided so as to cover the rear end side from the position of the flexible vibration portion, ultrasonic waves propagating axially rearward from the flexible vibration portion are also more likely to be appropriately guided toward the axial tip side.

[0019] At least a portion of the inner circumferential surface (i.e., the surface facing the axis) at the axial tip of the reflecting portion may be formed with a first inclined surface that is inclined in a direction approaching the axis of the sonotrode (i.e., inward) as it approaches the tip. When the first inclined surface is provided, ultrasonic waves that pass through the tip opening of the reflecting portion are more likely to converge on the target object to be irradiated with ultrasonic waves (in this disclosure, the cornea of ​​the test eye). Therefore, ultrasonic waves generated by the ultrasonic actuator are more likely to be emitted to the test eye with higher efficiency. Note that the first inclined surface can also be expressed as an inclined surface that is inclined so as to face the rear end side in the axial direction of the sonotrode.

[0020] The range of the axial tip of the inner circumferential surface of the reflecting portion where the first inclined surface is formed can be set as appropriate. For example, if the axial tip of the reflecting portion protrudes further distally than the axial tip of the flexible vibration portion, the first inclined surface may be formed at least on the inner circumferential surface of the reflecting portion distal to the flexible vibration portion. In this case, ultrasonic waves are more likely to converge on the target object. As an example, in the present disclosure, the first inclined surface is formed on at least the axial range of the inner circumferential surface of the reflecting portion from the tip of the flexible vibration portion to the most distal end of the inner circumferential surface of the reflecting portion. In particular, in the present disclosure, the first inclined surface is formed in the range from the most distal end of the inner circumferential surface of the reflecting portion to the most distal end of the second inclined surface described below. Note that the entire inner circumferential surface of the reflecting portion distal to the flexible vibration portion does not necessarily have to be the first inclined surface. In other words, it is sufficient that the first inclined surface is formed at a position where ultrasonic waves are more likely to converge on the target object.

[0021] However, the inner circumferential surface of the axial tip of the reflecting portion may be formed parallel to the axis of the sonotrode, which also makes it easier for the ultrasonic waves to be appropriately guided to the tip side by the reflecting portion.

[0022] The outer peripheral surface (i.e., the surface facing away from the axis) at the axial tip of the reflecting part may have an outer peripheral inclined surface that is inclined in a direction approaching the axis of the sonotrode (i.e., inward) as it approaches the tip. By providing an outer peripheral inclined surface, it becomes easier to ensure space around the reflecting part. Therefore, it becomes even easier to install an ultrasonic actuator equipped with a reflecting part in a device. For example, even when multiple ultrasonic actuators are arranged as closely as possible, installation of the ultrasonic actuator becomes easier.

[0023] An annular space may be formed around the axis, surrounded by the tip of the main body supporting the flexible vibration part of the sonotrode, the flexible vibration part provided at the tip of the main body, and the inner circumferential surface of the reflector. At least a portion of the inner circumferential surface of the reflector facing the annular space may have a second inclined surface inclined in a direction away from the axis of the sonotrode (i.e., outward) as it approaches the tip. In this case, ultrasonic waves propagating through the annular space are more likely to be reflected by the second inclined surface toward the axial tip. In other words, ultrasonic waves propagating from the flexible vibration part toward the axial rear end are also more likely to be reflected by the second inclined surface toward the axial tip. Furthermore, if two adjacent surfaces at an angle of 90 degrees or less exist near the annular space, unintended phenomena such as diffraction are more likely to occur at the corner surrounded by the two surfaces. As a result, the quality of the ultrasonic waves irradiated to the test eye may be reduced. In contrast, by providing a second inclined surface on the inner peripheral surface of the reflecting portion, it is possible to eliminate or reduce the number of adjacent surfaces that are at an angle of 90 degrees or less near the annular space. This makes it easier for the ultrasonic waves generated by the ultrasonic actuator to be emitted more appropriately toward the subject's eye. The second inclined surface can also be expressed as an inclined surface that is inclined so as to face the tip side in the axial direction of the sonotrode.

[0024] The range of the inner circumferential surface of the reflecting portion where the second inclined surface is formed can be set as appropriate. For example, the base end of the second inclined surface may coincide with the base end of the annular space in the axial direction of the sonotrode. In this case, the number of adjacent surfaces at an angle of 90 degrees or less near the annular space is reduced. This makes it easier for the ultrasonic waves generated by the ultrasonic actuator to be emitted more appropriately toward the subject's eye.

[0025] Furthermore, the distal end of the second inclined surface may be smoothly connected to the proximal end of the first inclined surface, which makes it easier for the ultrasonic waves propagating through the annular space to be guided toward the distal end more appropriately.

[0026] However, it is also possible to change the ranges of the inner circumferential surface of the reflecting portion where the first and second inclined surfaces are formed. For example, a surface parallel to the axis of the sonotrode may be formed between the first and second inclined surfaces in the axial direction of the sonotrode. Even in this case, the provision of the reflecting portion makes it easier to properly guide the ultrasound toward the distal end.

[0027] The cross-sectional shape of the second inclined surface formed on the inner peripheral surface of the reflecting portion when viewed in a cross section including the axis of the sonotrode may be a curved shape that is inclined in a direction that moves away from the axis of the sonotrode as it approaches the tip side. In this case, the ultrasonic waves that have propagated through the annular space are more likely to be reflected toward the tip side by the second inclined surface more efficiently.

[0028] As an example, in the present disclosure, the cross-sectional shape of the second inclined surface when viewed in a cross section including the axis is formed in a partial arc shape. As a result, ultrasonic waves are efficiently reflected toward the distal end. However, the cross-sectional shape of the second inclined surface may be formed in a curved shape other than a partial arc (e.g., a partial elliptical arc shape, a quadratic curve shape, a sinusoidal curve shape, etc.). It is also possible to form the cross-sectional shape of the second inclined surface when viewed in a cross section including the axis in a linear shape. Even in this case, ultrasonic waves are more easily guided toward the distal end than when the second inclined surface is not formed on the inner peripheral surface of the reflecting portion.

[0029] An annular space may be formed around the axis, surrounded by the distal end of the main body supporting the flexible vibration portion of the sonotrode, the flexible vibration portion provided at the distal end of the main body, and the inner circumferential surface of the reflecting portion. The ultrasonic tonometer may further include a fixing portion that fixes the position of the reflecting portion relative to the sonotrode, axially proximal to the annular space. The sonotrode and the reflecting portion may be spaced apart from each other over the entire circumferential direction, axially distal to the fixing portion. In this case, ultrasonic vibration of the sonotrode is more likely to occur appropriately than when the reflecting portion and the sonotrode contact each other distal to the fixing portion. Therefore, ultrasonic waves are more likely to be irradiated to the subject's eye more appropriately.

[0030] The ultrasonic tonometer may further include a back mass, a flange, and a fixing portion. The back mass is disposed on the axial rear end side of the ultrasonic element and sandwiches the ultrasonic element between the back mass and the sonotrode. The flange is provided on at least one of the sonotrode and the back mass and extends in a direction away from the axis. The fixing portion is provided on the reflecting portion and is attached to the flange via a vibration-damping member that attenuates vibration, thereby fixing the position of the reflecting portion relative to the sonotrode. In this case, because the fixing portion of the reflecting portion is attached to the flange via the vibration-damping member, ultrasonic vibration of the sonotrode is more likely to occur appropriately. Therefore, ultrasonic waves are more likely to be irradiated to the subject's eye more appropriately.

[0031] The reflecting portion attached to the flange portion via the vibration-isolating member may be attached to a holder that holds the ultrasonic actuator. In this case, ultrasonic vibration of the sonotrode is more likely to occur appropriately than when at least one of the sonotrode and the back mass is directly attached to the holder. Therefore, ultrasonic waves are more likely to be irradiated to the subject's eye more appropriately.

[0032] The flange portion may be provided on the sonotrode instead of the back mass. In a Langevin type transducer, it is necessary to connect wiring to the electrode placed between the sonotrode and the back mass. By providing the flange portion on the sonotrode, the wiring connected to the electrode can be easily passed to the rear end side in the axial direction. This prevents the configuration of the ultrasonic actuator from becoming complicated. However, it is also possible to provide the flange portion on the back mass.

[0033] The cross-sectional shape of the inner peripheral surface of the reflecting portion when viewed in a cross section perpendicular to the axis at any position in the axial direction can be selected as appropriate. For example, the cross-sectional shape of the inner peripheral surface of the reflecting portion in a cross section perpendicular to the axis may be circular or elliptical. In this case, corners are less likely to be formed on the inner peripheral surface of the reflecting portion, making it less likely that diffraction or other reductions will occur at the corners. Furthermore, if the cross-sectional shape of the inner peripheral surface of the reflecting portion is circular, the direction of irradiation of ultrasonic waves guided by the reflecting portion is more likely to be stable. By making the cross-sectional shape of the inner peripheral surface of the reflecting portion elliptical according to the space in which the ultrasonic actuator is to be disposed, it is easier to ensure freedom in the placement of the ultrasonic actuator. However, the cross-sectional shape of the inner peripheral surface of the reflecting portion in a cross section perpendicular to the axis can also be a shape other than circular or elliptical (e.g., polygonal or sectorial).

[0034] The ultrasonic actuator may further include a protective member (e.g., a mesh-like member or a slit-like member) that covers the tip opening of the reflecting portion and allows ultrasonic waves to pass from the tip opening to the tip side in the axial direction. The provision of the protective member makes it difficult for the user's fingers or foreign objects to come into contact with the sonotrode inside the reflecting portion. This makes it easier for the ultrasonic vibration of the sonotrode to be performed more appropriately.

[0035] The ultrasonic tonometer may include a plurality of ultrasonic actuators. The ultrasonic tonometer may applanate the cornea of ​​the subject's eye by irradiating the cornea with ultrasonic waves generated by the plurality of ultrasonic actuators. In this case, by using a plurality of ultrasonic actuators each equipped with a reflecting portion, ultrasonic waves with a higher output are irradiated onto the cornea. As a result, the cornea is more likely to be applanated appropriately, which makes it easier to perform appropriate intraocular pressure measurement using ultrasonic waves.

[0036] 6 is a side view showing the appearance of the ultrasonic tonometer 1. FIG. 7 is a plan view showing the schematic configuration inside the housing of the ultrasonic tonometer. FIG. 8 is a diagram showing the schematic configuration of the irradiation unit 100 when viewed from the side of the eye E to be examined. FIG. 9 is a block diagram showing the schematic configuration of the control system of the ultrasonic tonometer 1. FIG. 10 is a perspective view of the ultrasonic actuator 10 of the present embodiment. FIG. 11 is a cross-sectional view of the ultrasonic actuator 10 in a plane including the axis O. FIG. 12 is an enlarged cross-sectional view of a region R in FIG. 6. FIG. 13 is a graph showing the results of a comparison test.

[0037] A typical embodiment according to the present disclosure will be described below with reference to the drawings. The ultrasonic tonometer 1 includes an ultrasonic actuator 10 that emits ultrasonic waves and measures the intraocular pressure of the subject's eye E in a non-contact manner using the ultrasonic waves emitted by the ultrasonic actuator 10. For example, the ultrasonic tonometer 1 can measure the intraocular pressure of the subject's eye E by optically or acoustically detecting changes in the shape or vibration of the subject's eye E caused by irradiating the subject's eye E with ultrasonic waves. As an example, the ultrasonic tonometer 1 may continuously irradiate the cornea of ​​the subject's eye E with pulse waves or burst waves and measure the intraocular pressure of the subject's eye E based on ultrasonic output information when the cornea is deformed into a predetermined state (e.g., an applanated state or a flattened state). The ultrasonic output information may be, for example, at least one of the sound pressure, acoustic radiation pressure, irradiation time (e.g., the elapsed time after a trigger signal to start ultrasonic irradiation is input), and frequency of the ultrasonic waves. When deforming the cornea of ​​the subject's eye E, for example, ultrasonic sound pressure, acoustic radiation pressure, or acoustic streaming may be used. The ultrasonic tonometer 1 may also measure the intraocular pressure of the subject's eye E based on an ultrasonic signal received in response to irradiation of the subject's eye E with ultrasonic waves. In this case, at least one of the amplitude and frequency of the ultrasonic waves may be used as the ultrasonic signal. The ultrasonic actuator 10 may also be used in ophthalmic devices other than the ultrasonic tonometer 1.

[0038] <Overall Configuration> The overall configuration of the ultrasonic tonometer 1 will be described with reference to FIG. 1 . As shown in FIG. 1 , in this embodiment, the front-to-back direction of the device is the Z direction, the left-to-right direction of the device is the X direction, and the up-to-down direction of the device is the Y direction. The ultrasonic tonometer 1 of this embodiment includes a base 2, a housing 3, a face support unit 4, and a drive unit 5. The base 2 supports the entire device, including the housing 3 of the ultrasonic tonometer 1. The housing 3 is provided with an irradiation unit 100 and an optical system 200, which will be described later. The housing 3 also includes a display unit 75 that displays various images and an operation unit 76 (e.g., a touch panel provided on the display unit 75) through which the examiner inputs various instructions to the ultrasonic tonometer 1. The face support unit 4 supports the face of the subject. In this embodiment, the face support unit 4 is installed on the base 2. However, the face support unit 4 may be installed in a location other than the base 2. The drive unit 5 changes the relative position between the housing 3 and the subject's eye E, which is supported by the face support unit 4. The drive unit 5 of this embodiment changes the relative position between the eye E and the housing 3 by moving the housing 3 relative to the base 2 .

[0039] <Irradiation Unit> The configuration of the irradiation unit 100 in the ultrasonic tonometer 1 of this embodiment will be described with reference to FIGS. 2 and 3 . FIG. 2 is a plan view showing a schematic configuration inside the housing of the ultrasonic tonometer 1 of this embodiment. FIG. 3 is a diagram showing a schematic configuration of the irradiation unit 100 as viewed from the examinee's eye E. As shown in FIG. 2 , the irradiation unit 100 is disposed in front of the examinee's eye E and irradiates ultrasonic waves onto the examinee's eye E (in this embodiment, the cornea of ​​the examinee's eye E). As shown in FIG. 3 , the irradiation unit 100 of this embodiment includes multiple ultrasonic actuators 10 (10A, 10B, 10C, 10D, 10E, and 10F). In other words, the irradiation unit 100 of this embodiment can also be expressed as a parametric speaker. The ultrasonic tonometer 1 of this embodiment applanates the cornea of ​​the examinee's eye E by irradiating the cornea with ultrasonic waves generated by the multiple ultrasonic actuators 10. As a result, the cornea is more likely to be applanated appropriately by the multiple ultrasonic actuators 10, making it easier to perform intraocular pressure measurement using ultrasound more appropriately. The ultrasonic actuator 10 will be described in detail later.

[0040] The multiple ultrasonic actuators 10 are held by the holding unit 101 with their axial tip ends (the side where ultrasonic waves are emitted) facing the test eye. As shown in FIG. 2 , the shape of the holding unit 101 on the test eye E side of the test eye E in this embodiment is a partial spherical surface. The multiple ultrasonic actuators 10 are held by the holding unit 101 and arranged on a spherical surface. As a result, the sound axes of the multiple ultrasonic actuators 10 intersect at a single point, making it easier for ultrasonic waves to converge at the point where the sound axes intersect. However, the multiple ultrasonic actuators 10 do not necessarily have to be arranged on a spherical surface; they may be arranged on a curved surface such as an ellipsoid or a flat surface. The phase of the ultrasonic waves irradiated to the test eye E can also be controlled by appropriately adjusting the drive waveforms, etc., of the multiple ultrasonic actuators 10. Controlling the phase of the ultrasonic waves irradiated to the test eye E may perform at least one of adjusting the focal position and controlling the increase / decrease of the ultrasonic output. Also, as an example, six ultrasonic actuators 10 (10A to 10F) are used in the irradiation unit 100 of this embodiment, but it goes without saying that the number of ultrasonic actuators 10 used is not limited to six. One ultrasonic actuator 10 may be used alone in an ophthalmic device such as an ultrasonic tonometer.

[0041] 2 and 3 , the holder 101 is formed with an opening 102 for passing the optical axis of the optical system 200. In this embodiment, the opening 102 for passing the optical axis O1 of an observation system (photography optical system) 220 (described later) is provided in the center of the holder 101. That is, the optical axis O1 of the observation system 220 is disposed in the opening 102 of the holder 101. As described above, by providing the opening 102 for passing the optical axis O1 of the observation system 220 in the holder 101 that holds the multiple ultrasonic actuators 10, ultrasonic waves with sufficient output are irradiated onto the subject's eye E, and the subject's eye E is properly observed via the observation system 220. In this embodiment, a first hole 103 through which a light projection optical axis O3 of the deformation detection system 260 (or the Z alignment detection system 280) passes is provided on one of the left and right sides of the holder 101, and a second hole 104 through which a light reception optical axis O4 of the deformation detection system 260 (or the Z alignment detection system 280) passes is provided on the other side. A light-transmitting member 102A (e.g., a transparent plate or a lens) that transmits light while preventing foreign matter from entering the ultrasonic actuator 10 is provided in the opening 102. Similarly, a light-transmitting member 103A is provided in the first hole 103, and a light-transmitting member 104A is provided in the second hole 104.

[0042] As shown in FIG. 3 , the ultrasonic actuators 10A-10F are held by a holder 101 so as to surround an opening 102 through which the optical axis O1 of the observation system 220 passes. Specifically, in this embodiment, the ultrasonic actuators 10A-10F are arranged such that the sound source areas (the total area of ​​the ultrasonic irradiation surfaces of the ultrasonic actuators 10A-10F) are vertically symmetrical in the upper and lower regions of the holder 101 when the holder 101 is divided by a horizontal plane H including the optical axis O1. Furthermore, the ultrasonic actuators 10A-10F are arranged such that the sound source areas are horizontally symmetrical in the left and right regions of the holder 101 when the holder 101 is divided by a vertical plane V including the optical axis O1. This can prevent the acoustic axis L1 of the ultrasonic waves from deflecting relative to the optical axis O1, making it easier to irradiate the subject's eye E with ultrasonic waves more appropriately. The acoustic axis is the central axis of the ultrasonic waves irradiated by the irradiation unit 100. The acoustic axis extends in the direction of propagation of the ultrasonic waves or in the direction of vibration of the irradiation unit 100, and passes through the focal position where the ultrasonic waves output by the irradiation unit 100 are focused.

[0043] As shown in FIG. 3 , when the irradiation unit 100 is viewed from the subject's eye E, the ultrasonic actuators 10A to 10F have a circular or elliptical shape (more specifically, the inner shape of the reflecting unit 50, which will be described later). Therefore, corners are less likely to form on the inner circumferential surface of the reflecting unit 50, reducing the likelihood of diffraction or other reductions at the corners. As a result, ultrasonic waves are more likely to be irradiated appropriately onto the subject's eye E. Specifically, when the irradiation unit 100 is viewed from the subject's eye E, the ultrasonic actuators 10A and 10D have a circular shape. Therefore, the direction of ultrasonic waves emitted by the ultrasonic actuators 10A and 10D is more likely to be stabilized. Furthermore, when the irradiation unit 100 is viewed from the subject's eye E, the ultrasonic actuators 10B, 10C, 10E, and 10F have an elliptical shape in accordance with the installation space of each ultrasonic actuator 10 in the holding unit 101. As a result, the degree of freedom in arranging the ultrasonic actuators 10A to 10F is appropriately ensured. However, it is also possible to change the shape of the inside of the reflecting portion 50 of each of the ultrasonic actuators 10A to 10F.

[0044] Assume that adjustment of the relative position between the subject's eye E and the housing of the ultrasonic tonometer 1 in the X, Y, and Z directions (so-called alignment) is complete, and the optical axis O1 of the observation system 220 passes through the cornea (hereinafter referred to as the "alignment completion state"). In this embodiment, in the alignment completion state, the multiple ultrasonic actuators 10A-10F are held by the holding unit 101 so that, when viewed from the subject's eye E (more specifically, the corneal apex of the subject's eye E), all of the multiple ultrasonic actuators 10A-10F are within a range in which their angle with respect to the optical axis O1 is 48 degrees or less. In this case, the possibility that part of the ultrasonic waves emitted from the irradiation unit 100 toward the subject's eye E will be blocked by the subject's nose is reduced. This makes it easier to more appropriately irradiate the subject's eye E with ultrasonic waves.

[0045] <Optical System> The configuration of the optical system 200 in the ultrasonic tonometer 1 of this embodiment will be described with reference to Fig. 2. The optical system 200 is used to perform at least one of observation and measurement of the subject's eye. The optical system 200 of this embodiment includes an objective system 210, an observation system 220, a fixation target projection system 230, an illumination system 240, a deformation detection system 260, a Z-alignment detection system 280, a dichroic mirror 201, and a beam splitter 204.

[0046] The objective system 210 is an optical system for taking in light from outside the housing 3 to the optical system 200 and / or irradiating light from the optical system 200 to outside the housing 3. The objective system 210 includes optical elements (for example, at least one of an objective lens, a relay lens, etc.).

[0047] The illumination system 240 includes an illumination light source 241 and illuminates the subject's eye E. The illumination system 240 of this embodiment illuminates the subject's eye E with infrared light using the illumination light source 241, which is an infrared light source. In this embodiment, the multiple illumination light sources 241 are disposed diagonally in front of the subject's eye E.

[0048] The observation system 220 captures an observation image of the subject's eye E (in this embodiment, an image of the anterior segment of the subject's eye E). Specifically, the observation system 220 of this embodiment includes a light-receiving lens 221 and a light-receiving element 222. The observation system 220 of this embodiment receives a light beam reflected from the subject's eye E, the light beam being centered on the optical axis O1. That is, at least a portion of the light emitted from the illumination light source 241 and reflected by the subject's eye E is received by the light-receiving element 222. In this embodiment, the reflected light from the subject's eye E passes through the opening 102 of the irradiation unit 100, passes through the objective system 210 and the light-receiving lens 221, and is received by the light-receiving element 222. In this embodiment, the corneal reflection bright spot of the illumination light source 241 received by the light-receiving element 222 is used, for example, for alignment in the up / down and left / right directions (XY alignment). In this case, the illumination system 240 and the observation system 220 function as an XY alignment detection unit. Of course, an index projection system that projects an index for XY alignment from the optical axis O1 onto the subject's eye may be provided separately from the illumination system 240. In this case, the corneal central bright spot is captured in the observation image of the observation system 220, and therefore, XY alignment may be performed based on the corneal central bright spot.

[0049] The fixation target projection system 230 projects a fixation target onto the subject's eye E. The fixation target projection system 230 of this embodiment includes a target light source 231, an aperture 232, a projection lens 233, an aperture 234, etc. Light from the target light source 231 passes through the aperture 232, the projection lens 233, the aperture 234, etc. along an optical axis O2 and is reflected by the dichroic mirror 201. The dichroic mirror 201 makes the optical axis O2 of the fixation target projection system 230 coaxial with the optical axis O1. The light from the target light source 231 reflected by the dichroic mirror 201 passes through the objective system 210 along the optical axis O1 and is irradiated onto the subject's eye E. When the subject fixates on the target of the fixation target projection system 230, the subject's line of sight is stabilized.

[0050] The deformation detection system 260 detects deformation of the cornea of ​​the subject's eye E. The deformation detection system 260 of this embodiment includes a light source 261, a projector lens 262, an aperture 263, a light-receiving lens 264, an aperture 265, and a light-receiving element 266. Light from the light source 261 passes through the projector lens 262, the aperture 263, and the first hole 103 of the holder 101 along the optical axis O3, and is irradiated onto the subject's eye E. The reflected light emitted from the light source 261 and reflected by the subject's eye E passes through the second hole 104 of the holder 101 along the optical axis O4, is reflected by the beam splitter 204, passes through the light-receiving lens 264 and the aperture 265, and is received by the light-receiving element 266. The deformation detection system 260 detects deformation of the cornea based on the corneal reflected light received by the light-receiving element 266.

[0051] For example, the deformation detection system 260 may detect the state of deformation of the cornea based on the magnitude of the light-receiving signal of the light-receiving element 266. The deformation detection system 260 may detect the timing when the amount of light received by the light-receiving element 266 is maximum as the timing when the cornea has reached an applanated state. In this case, the deformation detection system 260 is set so that the amount of light received reaches a maximum when the cornea of ​​the subject's eye reaches an applanated state. The deformation detection system 260 may be an anterior segment cross-sectional image capturing unit such as an OCT or Scheimpflug camera. The deformation detection system 260 may also detect at least one of the amount of deformation or the rate of deformation of the cornea.

[0052] The Z alignment detection system 280 detects the relative positional relationship in the Z direction between the subject's eye E and the housing 3 (i.e., the alignment state in the Z direction). The Z alignment detection system 280 of this embodiment includes a light-receiving lens 281 and a light-receiving element 282. The Z alignment detection system 280 of this embodiment detects the alignment state in the Z direction by detecting reflected light from the cornea of ​​the subject's eye E. As an example, the Z alignment detection system 280 of this embodiment receives light emitted from the light source 261 and reflected by the cornea of ​​the subject's eye E. In this case, the Z alignment detection system 280 may receive a bright spot formed by reflection of light from the light source 261 by the cornea of ​​the subject's eye E. In other words, in this embodiment, the light source 261 of the deformation detection system 260 also serves as the light source of the Z alignment detection system 280.

[0053] For example, light from the light source 261 reflected by the cornea of ​​the subject's eye E passes through the second hole 104 of the holder 101 along the optical axis O4, then passes through the beam splitter 204 and the light-receiving lens 281, and is received by the light-receiving element 282. If the relative positions of the subject's eye E and the Z alignment detection system 280 shift in the Z direction from the appropriate position, the receiving position of the light from the light source 261 reflected by the cornea (e.g., the position where the intensity of the received light signal is maximum) shifts on the light-receiving element 282. Therefore, the Z alignment detection system 280 may detect the alignment state based on the receiving position of the light from the light source 261 on the light-receiving element 282.

[0054] <Control System> The configuration of the control system in the ultrasonic tonometer 1 of this embodiment will be described with reference to FIG. 4 . The control unit 70 is responsible for various controls in the ultrasonic tonometer 1 (e.g., control of the entire device, calculation processing of measurement values, etc.). The control unit 70 may be realized, for example, by a general CPU (Central Processing Unit) 71, ROM 72, RAM 73, etc. The ROM 72 stores various programs and initial values ​​for controlling the operation of the ultrasonic tonometer 1. The RAM 73 temporarily stores various information. The control unit 70 may be configured with one control unit or multiple control units (i.e., multiple processors). The control unit 70 is connected to, for example, the drive unit 5, the storage unit 74, the display unit 75, the operation unit 76, the irradiation unit 100, the optical system 200, etc.

[0055] <Ultrasonic Actuator> The ultrasonic actuator 10 (10A-10F) of this embodiment will be described in detail with reference to FIGS. 5 to 7 . The ultrasonic actuator used in the ultrasonic tonometer 1 of this embodiment is a so-called Langevin-type transducer (sometimes referred to as a "bolt-clamped Langevin-type transducer"). In a Langevin-type transducer, the ultrasonic element 11 (11A, 11B) is compressed by two mass members (the sonotrode 20 and the back mass 30), thereby generating ultrasonic waves with high efficiency while reducing mechanical and thermal energy losses. The following description will be given using one ultrasonic actuator 10A as an example of the six ultrasonic actuators 10A-10F used in the ultrasonic tonometer 1. The other ultrasonic actuators 10B-10F may be identical to the ultrasonic actuator 10A described below, or may have slightly different shapes of some components. Below, the axis of the ultrasonic actuator 10 (which is also the axis of the sonotrode 20 of the ultrasonic actuator 10) is designated as O. The ultrasonic waves are emitted toward the tip side of the axis O (upper side in FIGS. 5 to 7).

[0056] As shown in FIG. 6 , the ultrasonic actuator 10 of this embodiment includes ultrasonic elements 11 (11A, 11B), electrodes 12 (12A, 12B), a sonotrode 20, a back mass 30, a bolt 40, and a reflecting portion 50. The ultrasonic elements 11 generate ultrasonic waves. For example, a piezoelectric element (piezoelectric ceramic, etc.) or a magnetostrictive element may be used as the ultrasonic element 11. The ultrasonic elements 11 of this embodiment have an annular (ring-like) shape. In this embodiment, multiple (two in this embodiment) ultrasonic elements 11A, 11B are used in a stacked state. Electrodes 12 (12A, 12B) are connected to each of the multiple ultrasonic elements 11A, 11B. The electrodes 12 of this embodiment also have an annular (ring-like) shape. In this embodiment, the electrode 12A is connected to the tip side of the ultrasonic element 11A, and the electrode 12B is connected to the tip side of the ultrasonic element 11B.

[0057] The sonotrode 20 and the back mass 40 (sometimes collectively referred to as "mass members") sandwich the ultrasonic element 11 between them, thereby increasing the tensile strength of the ultrasonic element 11 and improving its vibration resistance. As a result, high-power ultrasonic waves can be generated more easily. A metal block or the like may be used as the mass member.

[0058] The sonotrode (sometimes referred to as a horn or front mass) 20 is a mass member disposed on the distal end side of the ultrasonic element 11 in the axial O direction (i.e., toward the subject's eye E). The sonotrode 20 propagates ultrasonic waves generated by the ultrasonic element 11 into the air. A flexural vibration portion 22 is provided on the distal end side of the sonotrode 20 in the axial O direction (i.e., distal to the sonotrode main body 21). The flexural vibration portion 22 flexibly vibrates in response to ultrasonic vibrations of the sonotrode 20. As a result, ultrasonic waves are more likely to be emitted at a higher output than when the flexural vibration portion 22 is not provided. In this embodiment, the flexural vibration portion 22 and the sonotrode main body 21 are integrally formed. More specifically, in this embodiment, a portion of the sonotrode main body 21, which has a columnar (cylindrical) outer shape, slightly proximal to the distal end in the axial O direction is cut out in an annular shape, and the portion remaining distal to the cutout portion forms the flexural vibration portion 22. Therefore, the sonotrode 20 equipped with the flexible vibration portion 22 can be appropriately manufactured from a single member. In addition, in this embodiment, when the sonotrode 20 is viewed in a cross section including the axis O, the shape of the notch formed in the sonotrode body portion 21 is formed on a circular arc (or an elliptical arc). As a result, ultrasonic waves with a higher output can be more easily irradiated toward the tip side in the direction of the axis O.

[0059] However, the specific configurations of the sonotrode and the flexural vibration unit may be changed. For example, the flexural vibration unit and the sonotrode may be separate components. In this case, the flexural vibration unit may be fixed to the tip of the sonotrode with a fixing member such as a screw. Even in this case, the flexural vibration of the flexural vibration unit makes it easier to irradiate high-output ultrasonic waves.

[0060] A flange portion 24 that widens in a direction away from the axis O is provided near the rear end of the sonotrode 20 in the direction of the axis O. The flange portion 24 is used to attach the ultrasonic element 11, electrode 12, sonotrode 20, bending vibration portion 22, back mass 30, and bolt 50 of the ultrasonic actuator 10 to the ultrasonic tonometer 1. As will be described in detail later, in this embodiment, the fixing portion 60 of the reflecting portion 50 is attached to the flange portion 24, and the reflecting portion 50 is further held by a holding portion 101 (see FIGS. 2 and 3 ), thereby attaching the ultrasonic actuator 10 to the ultrasonic tonometer 1. In addition, a threaded hole 25 is formed near the axis O of the sonotrode 20, extending from the rear end to the center portion in the direction of the axis O. A bolt 40 is screwed into the threaded hole 25.

[0061] The back mass 30 is a mass member arranged on the rear end side of the ultrasonic element 11 in the axial O direction. The back mass 30 sandwiches the ultrasonic element 11 between itself and the sonotrode 20. The back mass 30 in this embodiment has a substantially cylindrical shape. A screw hole 35 is formed in the back mass 30 near the axis O, penetrating from the front end to the rear end in the axial O direction.

[0062] The bolt 40 has a substantially columnar or cylindrical shape. A helical thread is formed on the outer periphery of the bolt 40. The thread of the bolt 40 is threadedly engaged with the threaded hole 25 of the sonotrode 20 and the threaded hole 35 of the back mass 30. With the ultrasonic element 11 disposed between the sonotrode 20 and the back mass 30, the bolt 40 is threadedly engaged with the threaded hole 35 of the back mass 30 and the threaded hole 25 of the sonotrode 20. Therefore, the sonotrode 20 and the back mass 30 are tightened in a direction that brings them closer to each other. As a result, the ultrasonic element 11 is tightly sandwiched between the sonotrode 20 and the back mass 30.

[0063] The ultrasonic actuator 10 includes an insulating member 42. The insulating member 42 is disposed between the inner circumferential surfaces of the ring-shaped ultrasonic elements 11A and 11B and the electrodes 12A and 12B and the outer circumferential surface of the bolt 40, thereby preventing electric leakage to the bolt 40.

[0064] The reflecting unit 50 covers at least a portion of the circumferential direction of the flexible vibration unit 22 (in this embodiment, the entire circumferential direction) when the axis O is used as a reference, while forming a gap between the reflecting unit 50 and the flexible vibration unit 22. The reflecting unit 50 reflects at least a portion of the ultrasonic waves generated from the flexible vibration unit 22, guiding the direction of ultrasonic waves emitted by the ultrasonic actuator 10 toward the tip side in the axial direction O. The ultrasonic waves generated from the flexible vibration unit 22 propagate not only toward the tip side of the axis O, but also in directions away from the axis O, etc. In contrast, in the ultrasonic actuator 10 of this embodiment, ultrasonic waves propagating from the flexible vibration unit 22 in a direction other than the tip side in the axial direction O are reflected by the reflecting unit 50 and are easily guided toward the tip side in the axial direction O. As a result, the ultrasonic waves generated by the ultrasonic actuator 10 can be easily irradiated to the subject's eye E with high efficiency. In this embodiment, the reflecting unit 50 is made of a material such as aluminum or resin, which has a large difference in acoustic impedance with air.

[0065] The reflecting section 50 in this embodiment covers the entire circumferential circumference of the flexible vibration section 22. Therefore, ultrasonic waves are easily guided toward the tip side in the axial O direction over the entire circumferential circumference, which makes it easier to further improve the efficiency of emitting ultrasonic waves to the subject's eye E. Furthermore, in this embodiment, gaps between the flexible vibration section 22 and the reflecting section 50 are provided over the entire circumferential circumference of the flexible vibration section 22. Therefore, ultrasonic waves propagated to the rear end side of the flexible vibration section 22 are easily guided toward the tip side through the gaps provided over the entire circumferential circumference.

[0066] In this embodiment, the tip of the reflecting unit 50 in the axial O direction (the upper end in FIGS. 5 and 6 ) protrudes further toward the tip side than the tip of the bending vibration unit 22 in the axial O direction. As a result, at least a portion of the ultrasonic waves propagating obliquely in the tip direction as viewed from the bending vibration unit 22 is also reflected by the inner circumferential surface of the reflecting unit 50 (i.e., the inner surface facing the axis O side) and emitted toward the subject's eye E. Therefore, the ultrasonic waves generated by the ultrasonic actuator 10 can be more easily emitted to the subject's eye E with higher efficiency.

[0067] In the reflecting unit 50 of this embodiment, a first inclined surface 51 is formed on at least a portion of the inner circumferential surface (i.e., the surface facing the axis O) at the tip end in the axial O direction. The first inclined surface 51 is inclined in a direction approaching the axis O (i.e., inward) as it approaches the tip end. By providing the first inclined surface 51, ultrasonic waves that pass through the tip opening of the reflecting unit are more likely to converge on the target object to which the ultrasonic waves are irradiated (in this disclosure, the cornea of ​​the test eye E). Therefore, ultrasonic waves generated by the ultrasonic actuator 10 are more likely to be emitted to the test eye E with higher efficiency. The first inclined surface 51 can also be expressed as an inclined surface inclined so as to face the rear end side in the axial O direction.

[0068] In the reflecting unit 50 of this embodiment, a first inclined surface 51 is formed on at least the inner circumferential surface closer to the tip end in the axial O direction than the flexible vibration unit 22. As a result, ultrasonic waves are more easily converged on the target object. As an example, in this embodiment, the first inclined surface 51 is formed on the inner circumferential surface of the reflecting unit 50 in the axial O direction, at least in a range from the tip position of the flexible vibration unit 22 to the position of the most distal end of the inner circumferential surface of the reflecting unit 50. In detail, in this embodiment, the first inclined surface 51 is formed in a range from the most distal end of the inner circumferential surface of the reflecting unit 50 to the most distal end of a second inclined surface 52 described later. However, it is not necessary for the entire inner circumferential surface of the reflecting unit 50 that is closer to the tip end than the flexible vibration unit 22 to be the first inclined surface 51. In other words, it is sufficient that the first inclined surface 51 is formed at a position where ultrasonic waves are more easily converged on the target object.

[0069] Furthermore, in this embodiment, an outer peripheral inclined surface 53 is formed on the outer peripheral surface (i.e., the surface facing away from the axis O) at the tip of the reflecting unit 50 in the axial O direction, the outer peripheral inclined surface 53 being inclined in a direction approaching the axis O (i.e., inward) as it approaches the tip. The provision of the outer peripheral inclined surface 53 makes it easier to ensure space around the reflecting unit 50. This makes it even easier to install the ultrasonic actuator 10 equipped with the reflecting unit 50 in a device. For example, as shown in FIG. 3, even when multiple ultrasonic actuators 10 are arranged as closely as possible, the installation of the ultrasonic actuator 10 is made easier.

[0070] In this embodiment, an annular space CS is formed around the axis, surrounded by the tip portion of the sonotrode main body 21, the flexible vibration portion 22 provided at the tip of the sonotrode main body 21, and the inner circumferential surface of the reflecting portion 50. If the reflecting portion 50 were not provided, ultrasonic waves propagating through the annular space CS would often escape to the outside in a direction away from the axis O. In contrast, in this embodiment, a second inclined surface 52 is formed on at least a portion of the inner circumferential surface of the reflecting portion 50 that faces the annular space CS. The second inclined surface 52 is inclined in a direction away from the axis O (i.e., outward) as it approaches the tip. Therefore, ultrasonic waves propagating through the annular space CS are more likely to be reflected by the second inclined surface 52 toward the tip side in the axial O direction. In other words, ultrasonic waves propagating from the flexible vibration portion 22 toward the rear end side in the axial O direction are also more likely to be reflected by the second inclined surface 52 toward the tip side in the axial O direction. Furthermore, if two adjacent surfaces at an angle of 90 degrees or less exist near the annular space CS, unintended phenomena such as diffraction are likely to occur at the corner surrounded by the two surfaces. As a result, the quality of the ultrasound irradiated to the test eye E may be reduced. In response to this, by providing the second inclined surface 52 on the inner peripheral surface of the reflecting unit 50, it is possible to eliminate or reduce the number of adjacent surfaces at an angle of 90 degrees or less near the annular space CS. This makes it easier for the ultrasound generated by the ultrasonic actuator 10 to be emitted more appropriately toward the test eye E. The second inclined surface 52 can also be expressed as an inclined surface inclined toward the tip side in the axial O direction.

[0071] The second inclined surface 52 of this embodiment will be described in more detail. In this embodiment, the base-side end of the second inclined surface 52 coincides with the base-side end of the annular space CS in the direction of the axis O. That is, the base-side end of the annularly cut-out portion of the sonotrode 20 slightly proximal to the most distal end and the base-side end of the second inclined surface 52 coincide with each other in the direction of the axis O. Therefore, the number of two surfaces adjacent to each other at an angle of 90 degrees or less near the annular space CS is reduced. This makes it easier for the ultrasonic waves generated by the ultrasonic actuator 10 to be more appropriately emitted toward the subject's eye E. Furthermore, the tip-side end of the second inclined surface 52 smoothly connects to the base-side end of the first inclined surface 51 described above. This makes it easier for the ultrasonic waves propagating through the annular space CS to be more appropriately guided toward the tip side.

[0072] As shown in FIG. 6 , the cross-sectional shape of the second inclined surface 52 formed on the inner peripheral surface of the reflecting portion 50 when viewed in a cross section including the axis O is a curved shape that slopes away from the axis O as it approaches the tip. In this case, ultrasonic waves propagating through the annular space CS are more efficiently reflected toward the tip by the second inclined surface 52. Note that, as an example, in this embodiment, the cross-sectional shape of the second inclined surface 52 when viewed in a cross section including the axis O is formed in a partial arc shape. As a result, ultrasonic waves are efficiently reflected toward the tip. However, the cross-sectional shape of the second inclined surface 52 may be formed in a curved shape other than a partial arc (e.g., a partial elliptical arc shape, a quadratic curve shape, a sinusoidal curve shape, etc.). Furthermore, the cross-sectional shape of the second inclined surface when viewed in a cross section including the axis may also be formed in a linear shape.

[0073] As described above, a fixing portion 60 that fixes the position of the reflecting portion 50 relative to the sonotrode 20 is provided on the proximal side of the annular space CS in the axial O direction. In this embodiment, the sonotrode 20 and the reflecting portion 50 are spaced apart on the distal side of the fixing portion 60 in the axial O direction. Therefore, ultrasonic vibration of the sonotrode 20 is more likely to occur appropriately than when the reflecting portion 50 and the sonotrode 20 come into contact on the distal side of the fixing portion 60. This makes it easier for ultrasonic waves to be irradiated to the subject's eye E more appropriately.

[0074] A configuration for fixing the position of the reflecting unit 50 relative to the sonotrode 20 will be described with reference to Figure 7. As shown in Figure 7, a flange 24 that widens in a direction away from the axis O is provided near the rear end of the sonotrode 20 in the axial O direction. In addition, a fixing unit 60 that fixes the position of the reflecting unit 50 relative to the sonotrode 20 is provided on a part of the inside of the reflecting unit 50 (in the present embodiment, the inside of the base end side of the reflecting unit 50). The fixing unit 60 provided on the reflecting unit 50 is attached to the flange 24 via vibration-damping members 62A and 62B, thereby fixing the position of the reflecting unit 50 relative to the sonotrode 20. Therefore, ultrasonic vibration of the sonotrode 20 is more likely to occur appropriately than when the fixing unit 60 is attached to the sonotrode 20 (in the present embodiment, the flange 24) without the vibration-damping members 62A and 62B.

[0075] In the example shown in FIG. 7 , an annular (ring-shaped) vibration-damping member 62A is provided between the tip end surface of the flange portion 24 and the reflecting portion 50. Furthermore, a vibration-damping member 62B is provided between the rear end surface of the flange portion 24 and the fixing piece 55 of the reflecting portion 50. As an example, the fixing piece 55 and the vibration-damping member 62B in this embodiment are formed in an annular (ring-shaped) shape. However, the shapes of the fixing piece 55 and the vibration-damping member 62B may be changed. With the flange portion 24, the vibration-damping members 62A and 62B, the reflecting portion 50, and the fixing piece 55 assembled in appropriate positions, the fixing piece 55 is fixed to the rear end surface of the reflecting portion 50 by a screw 65. As a result, the vibration-damping member 62A, the flange portion 24, and the vibration-damping member 62B are sandwiched between the rear end surface of the reflecting portion 50 and the tip end surface of the fixing piece 55, thereby fixing the position of the reflecting portion 50 relative to the sonotrode 20. The vibration-isolating members 62A, 62 may be made of elastic materials such as rubber, or may be made of vibration-isolating grease, etc. However, the fixing method shown in Fig. 7 is one example, and the shape of each part may be changed.

[0076] As shown in Figure 7, in this embodiment, the flange portion 24 is provided on the sonotrode 20 rather than the back mass 30. As described above, in the ultrasonic actuator 10, it is necessary to connect wiring to the electrodes 12A, 12B arranged between the sonotrode 20 and the back mass 30. By providing the flange portion 24 on the sonotrode 20, the wiring connected to the electrodes 12A, 12B can be easily passed to the rear end side in the direction of the axis O. This prevents the configuration of the ultrasonic actuator 10 from becoming complicated. However, it is also possible to provide a flange portion on the back mass 30 and attach the fixing portion of the reflector 50 to the flange portion of the back mass 30.

[0077] In this embodiment, the reflecting unit 50, which is attached to the flange via a vibration-isolating member, is attached to a holding unit 101 (see FIGS. 2 and 3) that holds the ultrasonic actuator 10. Therefore, ultrasonic vibration of the sonotrode 20 is more likely to occur appropriately than when at least one of the sonotrode 20 and the back mass 30 is directly attached to the holding unit 101. Therefore, ultrasonic waves are more likely to be irradiated to the subject's eye E appropriately.

[0078] The cross-sectional shape of the inner peripheral surface of the reflecting portion 50 when viewed in a cross section perpendicular to the axis O at an arbitrary position in the direction of the axis O will be described. As described with reference to FIG. 3 , in this embodiment, the cross-sectional shape of the inner peripheral surface of the reflecting portion 50 in a cross section perpendicular to the axis O is circular or elliptical. In this case, corners are less likely to be formed on the inner peripheral surface of the reflecting portion 50, making it less likely that diffraction or the like will be reduced at the corners. Furthermore, if the cross-sectional shape of the inner peripheral surface of the reflecting portion 50 is circular, the irradiation direction of the ultrasonic waves guided by the reflecting portion 50 will be more stable. By making the cross-sectional shape of the inner peripheral surface of the reflecting portion 50 an ellipse according to the space in which the ultrasonic actuator 10 is to be disposed, it is easier to ensure freedom in the placement of the ultrasonic actuator 10.

[0079] Although not shown, the ultrasonic actuator 10 may further include a protective member (for example, a mesh-like member or a slit-like member) that covers the tip opening of the reflecting part 50 and allows ultrasonic waves to pass from the tip opening to the tip side in the axial O direction. By providing the protective member, it becomes difficult for the user's fingers or foreign objects to come into contact with the sonotrode 20 inside the reflecting part 50. This makes it easier for the sonotrode 20 to vibrate ultrasonically more appropriately.

[0080] Referring to FIG. 8 , the results of a comparative test to confirm the effect of using the reflecting portion 50 will be described. In this test, the ultrasonic actuator 10 equipped with the reflecting portion 50 of the above embodiment ("with reflecting portion" in FIG. 8 ) and the ultrasonic actuator with only the reflecting portion 50 removed ("without reflecting portion" in FIG. 8 ) were used, and the sound pressure level was measured while changing the distance from the tip of the ultrasonic actuator in the direction along the axis O. All conditions were the same except for the presence or absence of the reflecting portion 50. As shown in FIG. 8 , the sound pressure level in the case of "with reflecting portion" was higher than the sound pressure level in the case of "without reflecting portion" regardless of the distance from the tip. From the above results, it can be confirmed that the use of the reflecting portion 50 increases the output of ultrasonic waves irradiated in the direction of the tip of the axis O.

[0081] The techniques disclosed in the above embodiments are merely examples. Therefore, the techniques exemplified in the above embodiments can be modified. For example, in the above embodiments, the position of the reflector 50 relative to the sonotrode 20 is fixed by attaching the fixing portion 60 of the reflector 50 to the flange portion 24, which is continuous in the circumferential direction of the outer periphery of the mass member (the sonotrode 20 in this embodiment). However, the method for fixing the position of the reflector 50 relative to the sonotrode 20 can also be changed. For example, a plurality of fixing members such as protrusions may be formed at regular intervals on the outer periphery of the mass member (at least one of the sonotrode 20 and the back mass 30), and the position of the reflector 50 relative to the sonotrode 20 may be fixed by sandwiching each fixing member in the direction of the axis O. In this case, as in the above embodiments, it is desirable to use a vibration-damping member between the fixing member and the reflector 50.

[0082] REFERENCE SIGNS LIST 1 ultrasonic tonometer 10 ultrasonic actuator 11 (11A, 11B) ultrasonic element 12 (12A, 12B) electrode 20 sonotrode 21 sonotrode main body 22 flexural vibration part 24 flange part 30 back mass 50 reflecting part 51 first inclined surface 52 second inclined surface 53 outer peripheral inclined surface 60 fixing part 62A, 62B vibration-isolating member

Claims

1. An ultrasonic tonometer for measuring the intraocular pressure of a test eye using ultrasound, comprising an ultrasonic actuator having an ultrasonic element and irradiating ultrasonic waves to the test eye, the ultrasonic actuator comprising: a sonotrode for propagating ultrasonic waves generated by the ultrasonic element into the air; a flexural vibration section provided at the axial tip side of the sonotrode and flexurally vibrating in response to ultrasonic vibration of the sonotrode; and a reflecting section covering at least a portion of the circumferential direction of the flexural vibration section while forming a gap between the flexural vibration section and the flexural vibration section, thereby reflecting at least a portion of the ultrasonic waves generated by the flexural vibration section and guiding the direction of irradiation of ultrasonic waves by the ultrasonic actuator toward the axial tip side.

2. An ultrasonic tonometer as claimed in claim 1, characterized in that the axial tip of the reflecting part protrudes further towards the tip side than the axial tip of the flexible vibration part.

3. An ultrasonic tonometer as claimed in claim 1 or 2, characterized in that a first inclined surface is formed on at least a portion of the inner surface at the axial tip of the reflecting part, the first inclined surface being inclined in a direction approaching the axis of the sonotrode as it approaches the tip.

4. An ultrasonic tonometer as described in any one of claims 1 to 3, characterized in that an annular space having a shape annular around an axis is formed and is surrounded by the tip of a main body portion supporting the flexible vibration portion of the sonotrode, the flexible vibration portion provided at the tip of the main body portion, and the inner surface of the reflecting portion, and at least a portion of the inner surface of the reflecting portion that faces the annular space is formed with a second inclined surface that is inclined in a direction that moves away from the axis of the sonotrode as it approaches the tip.

5. An ultrasonic tonometer as described in claim 4, characterized in that the cross-sectional shape of the second inclined surface formed on the inner surface of the reflecting portion, when viewed in a cross section including the axis of the sonotrode, is a curved shape that is inclined in a direction away from the axis of the sonotrode as it approaches the tip.

6. An ultrasonic tonometer as described in any one of claims 1 to 5, characterized in that an annular space having a shape annular around an axis is formed and is surrounded by the tip of a main body portion supporting the flexible vibration portion of the sonotrode, the flexible vibration portion provided at the tip of the main body portion, and the inner surface of the reflecting portion, and further comprising a fixing portion for fixing the position of the reflecting portion relative to the sonotrode, on the base end side in the axial direction of the annular space, and the sonotrode and the reflecting portion are spaced apart on the tip side in the axial direction of the fixing portion.

7. An ultrasonic tonometer as described in any one of claims 1 to 6, further comprising: a back mass arranged on the axial rear end side of the ultrasonic element and sandwiching the ultrasonic element between it and the sonotrode; a flange portion provided on at least one of the sonotrode and the back mass and extending in a direction away from the axis; and a fixing portion provided on the reflecting portion and attached to the flange portion via an anti-vibration member that attenuates vibrations, thereby fixing the position of the reflecting portion relative to the sonotrode.

8. An ultrasonic tonometer as claimed in claim 7, characterized in that the reflecting section attached to the flange section via the vibration-isolating member is attached to a holding section which holds the ultrasonic actuator.

9. An ultrasonic tonometer as described in any one of claims 1 to 8, comprising a plurality of ultrasonic actuators, and characterized in that the cornea of ​​the test eye is applanated by irradiating the cornea with ultrasonic waves generated by the plurality of ultrasonic actuators.

10. An ophthalmic ultrasonic actuator used in an ophthalmic device that irradiates an ultrasonic wave to an eye to be examined, comprising: an ultrasonic element that generates ultrasonic waves; a sonotrode that propagates the ultrasonic waves generated by the ultrasonic element into the air; a flexural vibration section that is provided at the axial tip side of the sonotrode and flexurally vibrates in association with ultrasonic vibration of the sonotrode; and a reflecting section that covers at least a portion of the circumferential direction of the flexural vibration section while forming a gap between the flexural vibration section and the flexural vibration section, thereby reflecting at least a portion of the ultrasonic waves generated from the flexural vibration section and guiding the irradiation direction of the ultrasonic wave by the ultrasonic actuator to the axial tip side.

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