Electronic auscultation device

Abstract

This electronic auscultation device comprises: a diaphragm that contacts a living body, vibrates together with the living body, and has a light reflection part provided on the reverse surface of the diaphragm from the contact surface contacting the living body; a light source; a light receiving element that has a light receiving surface for receiving light emitted from the light source and specularly reflected by the light reflection part, and generates a signal corresponding to the amount of light that has reached the light receiving surface; a selection unit that selects any of a plurality of modes including a first mode for measuring living body vibrations including a first frequency band and a second mode for measuring living body vibrations including a second frequency band lower than the first frequency band; and a light emission amount adjustment unit for adjusting the light emission amount of the light source. The light emission amount adjustment unit adjusts the light emission amount of the light source so as to be a first light emission amount when the first mode is selected by the selection unit, and adjusts the light emission amount of the light source so as to be a second light emission amount smaller than the first light emission amount when the second mode is selected by the selection unit.

Description

Electronic stethoscope

[0001] The present disclosure relates to electronic auscultation devices.

[0002] In recent years, electronic auscultation devices that have sensors for measuring biological vibrations and can acquire biological sounds using the sensors have become popular. Patent Document 1 describes a device that measures biological vibrations using a piezoelectric element. This device sets the input impedance high when measuring low-frequency signals (up to 20 Hz) such as ballistocardiograms and pulse waves, and sets the input impedance low when measuring high-frequency signals (50 Hz or higher) such as heart sounds. This adjusts the amplification factor for biological vibrations.

[0003] Japanese Patent Application Laid-Open No. 2020-75136

[0004] Vibration measurement using an optical sensor has frequency characteristics different from those using a piezoelectric element. Some aspects of the present disclosure provide a technique for appropriately outputting vibrations measured using an optical sensor.

[0005] According to some embodiments, an electronic auscultation device is provided, comprising: a diaphragm that contacts a living body and vibrates together with the living body, the diaphragm having a light reflecting portion on the surface opposite to the contact surface that contacts the living body; a light source; a light receiving element having a light receiving surface that receives light emitted from the light source and specularly reflected by the light reflecting portion, and generating a signal corresponding to the amount of light reaching the light receiving surface; a selection means for selecting one of a plurality of modes including a first mode for measuring living body vibrations including a first frequency band and a second mode for measuring living body vibrations including a second frequency band lower than the first frequency band; and a light emission adjustment means for adjusting the light emission intensity of the light source, wherein when the first mode is selected by the selection means, the light emission adjustment means adjusts the light emission intensity of the light source to a first light emission intensity, and when the second mode is selected by the selection means, the light emission adjustment means adjusts the light emission intensity of the light source to a second light emission intensity smaller than the first light emission intensity.

[0006] According to the above embodiment, vibrations measured using an optical sensor can be output appropriately.

[0007] Other features and advantages of the present disclosure will become apparent from the following description taken in conjunction with the accompanying drawings, in which the same or similar components are designated by the same reference numerals.

[0008] Schematic diagram for explaining an example of the appearance of the electronic auscultation device of the first embodiment. Schematic diagram for explaining an example of the appearance of the electronic auscultation device of the first embodiment. Schematic diagram for explaining an example of the configuration of the chestpiece of the first embodiment. Schematic diagram for explaining an example of the operation of the chestpiece of the first embodiment. Schematic diagram for explaining an example of the operation of the chestpiece of the first embodiment. Schematic diagram for explaining an example of the operation of the chestpiece of the first embodiment. Schematic diagram for explaining an example of the operation of the chestpiece of the first embodiment. Schematic diagram for explaining an example of the operation of the chestpiece of the first embodiment. Schematic diagram for explaining an example of the change in the light receiving range of the first embodiment. A diagram for explaining the relationship between the displacement amount and the displacement signal of the first embodiment. Block diagram for explaining an example of the configuration of the electronic auscultation device of the first embodiment. A diagram for explaining the properties of heartbeat sounds and respiratory sounds and amplification processing according to a comparative example. A diagram for explaining amplification processing of the electronic auscultation device of the first embodiment. Block diagram for explaining an example of the circuit configuration of the electronic auscultation device of the first embodiment. Block diagram for explaining a modified circuit configuration of the electronic auscultation device of the first embodiment. Block diagram for explaining an example of the circuit configuration of the electronic auscultation device of the second embodiment. Block diagram for explaining a modified circuit configuration of the electronic auscultation device of the second embodiment.

[0009] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the claims. Although multiple features are described in the embodiments, not all of these multiple features are required, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0010] First Embodiment [Appearance of the Electronic Auscultation Device in the First Embodiment] The appearance of the electronic auscultation device 100 according to the first embodiment will be described with reference to FIGS. 1A to 8B . Note that the following drawings may be accompanied by a coordinate system CS, which is a three-dimensional Cartesian coordinate system having an x-axis, a y-axis, and a z-axis, to explain the directions. In these descriptions, the positive direction of the z-axis may be referred to as the upper side, and the negative direction of the z-axis may be referred to as the lower side. FIG. 1A shows the appearance of the electronic auscultation device 100 when viewed from one direction, and FIG. 1B shows the appearance of the electronic auscultation device 100 when viewed from another direction. The electronic auscultation device 100 is a diagnostic tool for listening to the internal sounds of a living body, such as a human or animal. The electronic auscultation device 100 is primarily used to listen to heartbeat and respiratory sounds.

[0011] As shown in FIG. 1A, the electronic auscultation device 100 includes a chestpiece 110 and a grip 120. The chestpiece 110 is a unit that is brought into contact with the surface of a living body, which is an example of a subject to be measured, during a diagnosis using the electronic auscultation device 100, to measure minute vibrations (displacements) on the surface of the living body and capture biological sounds. The chestpiece 110 detects minute displacements on the surface of the living body in close contact with the chestpiece 110 via a diaphragm 206 (described below). Therefore, the chestpiece 110 can also be referred to as a displacement detection device or a diaphragm displacement detection device. Furthermore, because the chestpiece 110 is used to detect vibrations on the surface of the living body, it can also be referred to as a biological vibration detection device.

[0012] The gripping portion 120 is gripped by a user (e.g., a doctor, nurse, or public health nurse) of the electronic auscultation device 100 when bringing the diaphragm 206 into close contact with the surface of a living body. Hereinafter, the user of the electronic auscultation device 100 will be simply referred to as the "user." The gripping portion 120 is rod-shaped as shown in FIGS. 1A and 1B, and the chestpiece 110 is attached to one end (the negative x-axis direction in FIGS. 1A and 1B). The gripping portion 120 is also called a handle, a grip, a handle, or the like.

[0013] The grip part 120 has a housing 121. The grip part 120 houses a battery and a circuit board inside the housing 121. The battery stores operating power for the electronic auscultation device 100. The circuit board has circuit elements for controlling the operation of the electronic auscultation device 100. The grip part 120 has a display unit 122, an operation unit 123, a power switch 124, and a connector 125 on the outer surface of the housing 121.

[0014] The display unit 122 displays the status of the electronic auscultation device 100. For example, the display unit 122 includes multiple indicators (four indicators in the example of FIG. 1A ). Each indicator is configured with a light-emitting diode (LED). The multiple indicators include an indicator indicating whether the power of the electronic auscultation device 100 is on or off. The multiple indicators also include an indicator indicating the current operating mode of the electronic auscultation device 100. The multiple indicators also include an indicator indicating whether the electronic auscultation device 100 is wirelessly connected to an external device. The multiple indicators also include an indicator indicating whether the chestpiece 110 is pressed against a living body surface. As shown in FIG. 1A , the display unit 122 is located on the outer surface of the housing 121, opposite the chestpiece 110, near one end of the chestpiece 110 in the x-axis direction. In this embodiment, "near the chestpiece 110" means closer to the chestpiece 110 than the center of the grip portion 120. The display unit 122 does not need to include all of the indicators described above, and the status of the electronic auscultation device 100 may be displayed using a liquid crystal panel or an electrostatic panel instead of or in addition to multiple indicators.

[0015] The operation unit 123 accepts operations from the user. In this embodiment, the operation unit 123 includes multiple physical buttons (three buttons in the example of FIG. 1A ) for accepting settings for the electronic auscultation device 100. Specifically, the operation unit 123 includes volume adjustment buttons (volume up button 123 a and volume down button 123 b) for adjusting the volume of the output sound. When the volume adjustment button is pressed, the electronic auscultation device 100 adjusts the gain of the signal output from the light-receiving element 204 and adjusts the volume of the sound output through the earphones. The operation unit 123 also includes a mode switching button 123 c for switching the operating mode of the electronic auscultation device 100. When the mode switching button 123 c is pressed, the operating mode is switched as described below. That is, the mode switching button 123 c accepts instructions from the user regarding the mode transition of the electronic auscultation device 100. The electronic auscultation device 100 selects one of multiple operating modes based on an instruction from the user using the mode switching button 123 c and operates in that operating mode. The operation unit 123 may include a touch panel instead of multiple physical buttons. The display unit 122 and the operation unit 123 may be integrated into a touch screen. The electronic auscultation device 100 may automatically select an operation mode in response to an acquired signal representing vibrations on the surface of a living body, instead of or in addition to a user instruction using the mode switching button 123c.

[0016] Like the display unit 122, the operation unit 123 is arranged on the outer surface of the housing 121 opposite the chestpiece 110, near one end of the chestpiece 110 in the x-axis direction. This arrangement allows the user to operate the operation unit 123 (for example, with their thumb) while holding the grip unit 120 during use of the electronic auscultation device 100. Furthermore, the display unit 122 is arranged at a position farther away from the center of the grip unit 120 in the x-axis direction than the operation unit 123. This arrangement allows the user to maintain visibility of the display unit 122 even when operating the operation unit 123 during use of the electronic auscultation device 100.

[0017] The power switch 124 is a switch that switches the power of the electronic auscultation device 100 on and off. The connector 125 is a connector for receiving a cable or a connector of an external device. Power is supplied from the external device to the battery included in the grip portion 120 through the connector 125. The power switch 124 may be provided on the chestpiece 110 instead of the grip portion 120. The connector 125 may be provided on the chestpiece 110 instead of the grip portion 120. Furthermore, the electronic auscultation device 100 may not include the connector 125. In this case, the electronic auscultation device 100 may have a wireless charging function or may be configured to have a replaceable battery.

[0018] The electronic auscultation device 100 in this embodiment includes both the chestpiece 110 and the grip portion 120, but may alternatively include only the chestpiece 110 and not the grip portion 120.

[0019] [Chestpiece Configuration of the Electronic Auscultation Device in the First Embodiment] An example configuration of the chestpiece 110 will be described with reference to Fig. 2. The upper side of Fig. 2 shows a cross-sectional view of the chestpiece 110, and the lower side of Fig. 2 shows a plan view of the chestpiece 110. In the plan view, only the light-emitting circuit board 203, the light-receiving circuit board 205, the diaphragm 206, and the light-reflecting portion 207 are shown to clarify the positional relationship of the components.

[0020] The chestpiece 110 includes a holding member 201, a light-emitting element 202, a light-emitting circuit board 203, a light-receiving element 204, a light-receiving circuit board 205, a diaphragm 206, a light-reflecting portion 207, and a housing 208. The housing 208 houses the holding member 201, the light-emitting element 202, the light-emitting circuit board 203, the light-receiving element 204, the light-receiving circuit board 205, and the light-reflecting portion 207. Because the holding member 201 has apertures 209 and 210, the housing 208 also houses the apertures 209 and 210. The diaphragm 206, together with the housing 208, form part of the exterior of the electronic auscultation device 100. Note that the components of the chestpiece 110 described here are merely examples, and in addition to the components shown in FIG. 2 , the chestpiece 110 may include a circuit board on which circuit elements for controlling its operation are mounted.

[0021] The light-emitting element 202 is a light source that emits light. Power is supplied to the light-emitting element 202 from a power source external to the chestpiece 110 (a battery in the grip portion 120). In this embodiment, the light-emitting element 202 is a light-emitting diode (LED).

[0022] The light-emitting element 202 is mounted on a light-emitting circuit board 203. On the light-emitting circuit board 203, for example, a peripheral circuit for regulating the light emission amount of the light-emitting element 202 and a power supply terminal for receiving power from a power source external to the chest piece 110 are mounted. The light-emitting circuit board 203 may be a printed wiring board such as a flexible circuit board, or may be a paper phenolic board or a glass epoxy board. The light-emitting circuit board 203 including the light-emitting element 202 functions as a light-emitting unit.

[0023] The light receiving element 204 functions as an optical sensor that generates an electrical signal based on the amount of light received using power supplied from a power source external to the chestpiece 110 (e.g., a battery in the grip portion 120). The power supplied to the light receiving element 204 is supplied from a power source external to the chestpiece 110 (e.g., a battery in the grip portion 120). The light receiving element 204 may be, for example, a phototransistor or a complementary metal-oxide semiconductor (CMOS) sensor. In this embodiment, there is one light receiving element 204; however, a plurality of light receiving elements 204 may be used to form a line sensor (light receiving elements arranged in a 1×n (n≧2)) or an area sensor (light receiving elements arranged in an m×n (m≧2, n≧2))

[0024] The light receiving element 204 is mounted on a light receiving circuit board 205. In addition to the light receiving element 204, the light receiving circuit board 205 is also mounted with peripheral circuits for reading out signals from the light receiving element 204, a signal terminal for outputting signals to a device external to the chest piece 110, and a power supply terminal for receiving power from a power source external to the chest piece 110. The light receiving circuit board 205 may be a printed wiring board such as a flexible circuit board, or may be a paper phenolic board or a glass epoxy board. The light receiving circuit board 205 including the light receiving element 204 functions as a light receiving unit.

[0025] The holding member 201 holds the light-emitting circuit board 203 and the light-receiving circuit board 205. The light-emitting circuit board 203 and the light-receiving circuit board 205 are fixed to the holding member 201. These boards may be fixed to the holding member 201 using an adhesive or using fastening members such as screws.

[0026] The diaphragm 206 has a contact surface 206a that contacts the surface of a living body, which is an example of a subject to be measured, and an inner surface 206b that is the surface opposite the contact surface 206a. The diaphragm 206 is configured to elastically deform when pressed by the subject to be measured contacting the contact surface 206a. The inner surface 206b of the diaphragm 206 is provided with a light reflecting portion 207, which will be described later. In this embodiment, the diaphragm 206 is a laminated plate of glass epoxy resin, which is formed by impregnating glass fiber with epoxy resin and then subjecting it to a heat curing treatment. The thickness is 230 μm. The diaphragm 206 also has an integrated ring-shaped rim for securing the diaphragm 206 to the holding member 201 or the housing 208. In this embodiment, the contact surface 206a and inner surface 206b of the diaphragm 206 refer to the portions of the diaphragm 206 that do not include the ring-shaped rim integrated with the diaphragm 206. The diaphragm 206 may have a multi-layer structure. In this case, the outermost layer of the multi-layered diaphragm 206 that contacts the object to be measured is defined as the contact surface 206a, and the innermost layer on which the light reflecting portion 207 is provided is defined as the inner surface 206b. The diaphragm 206 may be composed of multiple layers or members as long as it vibrates integrally with the object to be measured when it comes into contact with it. In this embodiment, even if a separate cover is attached to the contact surface 206, this configuration is considered to be one form of the diaphragm 206 as long as the cover and the contact surface 206a vibrate integrally with the object to be measured. Furthermore, the contact surface 206a of the diaphragm 206 is exposed to the outside when the electronic auscultation device 100 is in use, but may be covered with a protective cover when not in use to prevent damage or deterioration to the contact surface 206a.

[0027] The diaphragm 206 is held by the holding member 201. The diaphragm 206 extends along the xy plane of the coordinate system CS. The diaphragm 206 is arranged so as to contact the surface of a living body, which is an example of a measurement target. The diaphragm 206 forms part of the exterior of the chestpiece 110. The diaphragm 206 has a contact surface 206a arranged so as to contact the surface of a living body when the electronic auscultation device 100 is in use, and an inner surface 206b opposite the contact surface 206a.

[0028] The diaphragm 206 has a fixed portion 206c and is fixed to the holding member 201. The fixed portion 206c is located on the outer periphery of the diaphragm 206. The inner periphery of the diaphragm 206 (i.e., the portion inside the fixed portion 206c) is not fixed to the holding member 201. Therefore, the diaphragm 206 can vibrate in the z-axis direction with the fixed portion 206c as a node. Specifically, when the chestpiece 110 is in use, the diaphragm 206 vibrates with the fixed portion 206c as a node in response to displacement of the surface of the living body. In this vibration, the center 206e of the diaphragm 206 becomes an antinode. The diaphragm 206 functions as a vibrating part that vibrates together with the object to be measured.

[0029] The light reflecting portion 207 reflects light emitted from the light emitting element 202. The light reflecting portion 207 is adhered to the inner surface 206b of the diaphragm 206 and moves integrally with the diaphragm 206 in the z-axis direction in response to the vibration of the diaphragm 206, which is in close contact with the surface of the living body. The light reflecting portion 207 has a circular outer edge in a plan view. The light reflecting portion 207 may have a diameter of 15 mm to 20 mm. The light reflecting portion 207 is positioned to cover a region 206d including the center 206e of the circle of the diaphragm 206. Since the displacement of the diaphragm 206 changes most significantly at the center 206e, the displacement of the diaphragm 206 can be detected with high sensitivity by reflecting light from the light emitting element 202 in the region including the center 206e. Note that, although the light reflecting portion 207 is positioned to cover the center 206e in this embodiment, it may also be positioned to cover a region of the diaphragm 206 that does not include the center 206e. The light reflecting portion 207 is made of, for example, an aluminum vapor deposition film and is a sheet-like member attached to the inner surface 206b of the diaphragm 206 (the surface opposite to the contact surface 206a).

[0030] The light-emitting element 202 emits light toward the inner surface 206b of the diaphragm 206. The upper surface of the light-reflecting portion 207 reflects the light emitted from the light-emitting element 202. That is, the upper surface of the light-reflecting portion 207 functions as a light-reflecting surface. In the following description, the reflection of light on the upper surface (i.e., the light-reflecting surface) of the light-reflecting portion 207 will simply be referred to as light being reflected by the light-reflecting portion 207. The light-reflecting portion 207 specularly reflects (in other words, specularly reflects) the light emitted from the light-emitting element 202. In the following description, the light traveling from the light-emitting element 202 toward the light-reflecting portion 207 will be referred to as incident light 211, and the light after the incident light 211 is reflected will be referred to as reflected light 212.

[0031] In this embodiment, the light reflecting portion 207 is a separate member from the diaphragm 206. However, the light reflecting portion 207 may be configured as the same member as the diaphragm 206, with at least a portion of the inner surface 206b of the diaphragm 206 also serving as the light reflecting portion. Alternatively, a coating layer may be applied to the diaphragm 206, and the coating layer may serve as the light reflecting portion. For example, the entire inner surface 206b of the diaphragm 206 may have a high reflectivity that allows it to reflect light to an extent that can be detected by the light receiving element 204. Alternatively, only a region of the inner surface 206b of the diaphragm 206, which is the region that is reached by light emitted from the light emitting element 202, may have such a high reflectivity.

[0032] The light-emitting element 202 is positioned so as to emit light toward a region 207a of the light-reflecting portion 207 that includes a portion covering the center 206e of the diaphragm 206 when the diaphragm 206 is not in contact with the surface of the living body. When the diaphragm 206 is not in contact with the surface of the living body, the diaphragm 206 is flat. In this embodiment, as described above, an LED that emits diffused light is used as the light-emitting element 202. Therefore, the chestpiece 110 includes an aperture portion 209 that narrows the light emitted from the light-emitting element 202. The aperture portion 209 allows only a portion of the light emitted from the light-emitting element 202 to enter the light-reflecting portion 207. In the example of FIG. 2 , the aperture portion 209 corresponds to a portion of the holding member 201 where an opening is formed. Note that, in this embodiment, a component that emits diffused light has been described as an example of the light-emitting element 202. However, instead, a laser diode or the like that emits linear light may be used as the light-emitting element 202, and the linear light may be emitted toward the region 207a. If the light-emitting element 202 is a component that emits linear light, the diaphragm portion 209 may be omitted. In this embodiment, the portion of the holding member 201 where the opening is formed has been described as an example of the diaphragm portion 209, but a one-sided diaphragm may be used instead of an opening. In that case, for example, a light-shielding wall for narrowing down one side (upper or lower side) of the light emitted from the light-emitting element 202 is provided instead of the opening.

[0033] The light-receiving element 204 is positioned to receive the reflected light 212. Specifically, the light-receiving element 204 is positioned at a location where the amount of reflected light 212 received changes due to vibration of the diaphragm 206 in the z-axis direction. The light-receiving element 204 is positioned so that when the diaphragm 206 is not in contact with the surface of the living body (i.e., when the diaphragm 206 is flat), it receives more of the reflected light 212 than when the diaphragm 206 is vibrating. That is, the light-receiving element 204 outputs an electrical signal corresponding to the amount of reflected light 212 it receives, and the amount of displacement of the diaphragm 206 can be determined based on this electrical signal. The principle behind this can be described later. The chestpiece 110 has an aperture 210 that narrows the light specularly reflected by the light reflecting portion 207. The diaphragm section 210 prevents diffusely reflected light from entering the light receiving element 204 and allows only at least a portion of the light from the light reflecting section 207 (i.e., the primarily reflected light) to reach the light receiving element 204. In the example of FIG. 2 , the portion of the holding member 201 where the opening is formed functions as the diaphragm section 210. Note that, in this embodiment, the portion of the holding member 201 where the opening is formed has been described as an example of the diaphragm section 210, but a one-sided diaphragm may be used instead of an opening. In that case, for example, a light-shielding wall for narrowing down one side (upper or lower side) of the light from the light reflecting section 207 is provided instead of the opening.

[0034] A housing 208 is attached to the outer periphery of the holding member 201. The housing 208 covers the light-emitting circuit board 203 and the light-receiving circuit board 205 and prevents ambient sound from entering the housing 208. The outer edges of the diaphragm 206, the holding member 201, and the housing 208 are generally aligned with one another in a plan view of the contact surface 206a of the diaphragm 206. In this embodiment, the housing 208 is made of metal, and the grounds of the circuit boards (e.g., the light-emitting circuit board 203 and the light-receiving circuit board 205) inside the chestpiece 110 are electrically connected to the housing 208. This stabilizes the ground potential.

[0035] By fixing the diaphragm 206 to the holding member 201, an internal space 213 surrounded by the diaphragm 206 and the holding member 201 is formed. The internal space 213 is sealed in order to prevent the light receiving element 204 from receiving any light other than that emitted by the light emitting element 202. Furthermore, the diaphragm 206 and the holding member 201 have a light-blocking property in order to prevent the light receiving element 204 from receiving any light other than that emitted by the light emitting element 202. In the example of FIG. 2 , a fixed portion 206c of the diaphragm 206 is fixed to the holding member 201. Alternatively, in the example of FIG. 2 , the fixed portion 206c of the diaphragm 206 may be fixed to the housing 208.

[0036] [Example of Operation of the Electronic Auscultation Device in the First Embodiment] The operation of the chestpiece 110 of the electronic auscultation device 100 will be described with reference to Figures 3A to 3D. Figures 3A and 3B show the diaphragm 206 in an unpressured state (i.e., flat state), while Figures 3C and 3D show the diaphragm 206 in a state pressed by the biological surface 320. In each of Figures 3A and 3C, the lower side shows a cross-sectional view of the chestpiece 110, and the upper side shows a plan view of the chestpiece 110. The cross-sectional view of the chestpiece 110 omits the light-emitting circuit board 203, the light-receiving circuit board 205, and the housing 208, and shows the shape of the holding member 201 in detail. The plan view of the chestpiece 110 shows only the light-emitting element 202, the light-receiving element 204, the light-reflecting portion 207, the light-shielding wall 304, and the light-shielding wall 305. 3B and 3D are perspective views focusing on the light emitting element 202, the light receiving element 204, the light reflecting portion 207, the light shielding wall 304, and the light shielding wall 305. FIG.

[0037] 3A to 3D, the chestpiece 110 is used in contact with a biological surface 320, which is an example of a subject to be measured. That is, during use, the contact surface 206a of the diaphragm 206 of the chestpiece 110 is in close contact with the biological surface 320, which is an example of a subject to be measured. This causes the biological surface 320, diaphragm 206, and light reflecting portion 207 to vibrate together. Therefore, the chestpiece 110 detects the displacement of the upper surface of the light reflecting portion 207 in the z-axis direction as the displacement of the biological surface 320 in the z-axis direction. The displacement of the biological surface 320 occurs in response to physical movements, such as the heartbeat and breathing, of the person holding the biological surface 320.

[0038] 3A and 3B , the light-emitting element 202 and the light-receiving element 204 are positioned so that when the diaphragm 206 is flat, the light-receiving element 204 receives more reflected light 212 than when the diaphragm 206 is vibrating. The light-receiving element 204 amplifies and outputs a photocurrent corresponding to the amount of light received. The peripheral circuit of the light-receiving circuit board 205 converts the photocurrent output from the light-receiving element 204 into a voltage to generate an output value as a displacement signal, converts the displacement signal into a digital signal, and outputs it to an external device. In this embodiment, the displacement signal refers to the output value of the light-receiving element 204 that reflects the state and deformation of the diaphragm 206 at any given time.

[0039] 3C and 3D , when the diaphragm 206 is pressed by the biological surface 320 and the biological surface 320 is displaced upward, the distance in the z-axis direction between the light-emitting element 202 and the upper surface of the light-reflecting portion 207 decreases. Accordingly, the area of ​​the light-reflecting portion 207 that is reached by the incident light 211 moves closer to the light-emitting element 202, and the reflected light 212 also moves closer to the light-emitting element 202. As a result, the amount of reflected light 212 that reaches the light-receiving element 204 decreases, and the value of the displacement signal generated by the light-receiving circuit board 205 decreases.

[0040] 3A to 3D, the light-shielding wall 304 having the opening 306 formed therein functions as the diaphragm 209 on the incident light 211 side, and the light-shielding wall 305 having the opening 307 formed therein functions as the diaphragm 210 on the reflected light 212 side. In particular, the portion of the light-shielding wall 304 above the upper edge of the opening 306 corresponds to the first diaphragm. Therefore, part of the light emitted by the light-emitting element 202 is blocked by the light-shielding wall 304 and does not reach the light-reflecting portion 207. Furthermore, at least part of the light specularly reflected by the light-reflecting portion 207 is blocked by the light-shielding wall 305, depending on the position of the light-reflecting portion 207. In this embodiment, both the openings 306 and 307 are rectangular. In the following description, of the four sides of each of openings 306 and 307, the side parallel to and closer to diaphragm 206 will be referred to as the lower side, the side parallel to and farther from diaphragm 206 will be referred to as the upper side, the side on the left side as viewed from light-emitting element 202 will be referred to as the left side, and the side on the right side as viewed from light-emitting element 202 will be referred to as the right side.

[0041] 3A to 3D, incident light 211 and reflected light 212 represent light fluxes that reach light receiving element 204. In Fig. 3B, some light 310 of the light emitted from light emitting element 202 passes through opening 306 of light-shielding wall 304 and is reflected by light reflecting portion 207 to become light 311, but is blocked by a portion of light-shielding wall 305 that is above reflected light 212 and does not reach light receiving element 204. The same is true in Fig. 3D.

[0042] 3A and 3B , the portion of the light reflecting portion 207 that the incident light 211 reaches when the diaphragm 206 is not pressed by the biological surface 320 is referred to as the effective range 300. The effective range 300 is the portion of the light reflecting portion 207 that reflects light that reaches the light receiving element 204. When the diaphragm 206 is not pressed by the biological surface 320, the effective range 300 is equal to the range that the light from the light emitting element 202 reaches. In this embodiment, the effective range 300 is a rectangular area. The periphery of the effective range 300 is referred to as the boundary line of the effective range 300. The boundary line of the effective range 300 is located between the effective range 300 and the area other than the effective range 300. In the following description, part of the boundary line will also be referred to as the boundary line.

[0043] Of the four line segments that make up the boundary of the effective range 300, the line segment that includes the farthest position in the x-axis direction from the light-emitting element 202 is referred to as the far boundary 300a. The portion of the incident light 211 that reaches the far boundary 300a is referred to as the far incident light 211a. The far incident light 211a means that it includes the portion of the optical path from the light-emitting element 202 to the light reflecting portion 207 that is the longest. The angle of incidence of the incident light 211 to the light reflecting portion 207 reaches a maximum value 303a at a position on the far boundary 300a.

[0044] Of the four line segments that constitute the boundary of the effective range 300, the line segment that includes the position closest to the light-emitting element 202 in the x-axis direction is referred to as the near boundary 300b. The portion of the incident light 211 that reaches the near boundary 300b is referred to as the near incident light 211b. The near incident light 211b means that it includes the portion of the optical path from the light-emitting element 202 to the light reflecting portion 207 that is shortest. The angle of incidence of the incident light 211 to the light reflecting portion 207 reaches a minimum value 303b at a position on the near boundary 300b. Of the light emitted from the light-emitting element 202, light that is not included between the far incident light 211a and the near incident light 211b is attenuated by being reflected multiple times by the light-shielding wall 304.

[0045] Of the four line segments that make up the boundary of the effective range 300, the two line segments other than the far boundary 300a and the near boundary 300b are referred to as lateral boundary lines 300c and 300d. The lateral boundary line 300c is located on the right side of the effective range 300 as seen from the light-emitting element 202, and the lateral boundary line 300d is located on the left side of the effective range 300 as seen from the light-emitting element 202.

[0046] As shown in FIGS. 3A and 3B , the region of the light receiving element 204 formed by the reflected light 212 specularly reflected by the light reflecting portion 207 is referred to as the light irradiation region 301. The light irradiation region 301 is a portion of the light receiving element 204 where light emitted from the light emitting element 202 and specularly reflected by the light reflecting portion 207 reaches. In addition to the light specularly reflected by the light reflecting portion 207, scattered light may also reach the light receiving element 204. In this embodiment, the region formed by the specularly reflected light is defined as the light irradiation region. The amount of light reaching the light receiving element 204 is proportional to the area of ​​the light irradiation region 301. In this embodiment, the light irradiation region 301 is a rectangular region. The periphery of the light irradiation region 301 is referred to as the boundary line of the light irradiation region 301. The boundary line of the light irradiation region 301 is located between the light irradiation region 301 and the region other than the light irradiation region 301.

[0047] Of the four line segments constituting the boundary of the light irradiation area 301, the line segment formed by light narrowed by the aperture section 209 and specularly reflected by the light reflecting section 207 is referred to as the lower boundary 301a. Of the four line segments constituting the boundary of the light irradiation area 301, the line segment opposite the lower boundary 301a is referred to as the upper boundary 301b. The lower boundary 301a is an example of a boundary formed by light narrowed by the aperture section 209 and specularly reflected by the light reflecting section 207. The lower boundary 301a is a boundary that moves in response to the displacement of the contact surface 206a, as described below. In this embodiment, the movement of the lower boundary 301a changes the area of ​​the light irradiation area 301, and the output of the light receiving element 204 changes. This allows for accurate measurement of the displacement of the object to be measured. The upper boundary 301b is an example of a boundary that does not move in response to the displacement of the contact surface 206a and whose length does not change even when the contact surface 206a is displaced. Of the four line segments that make up the boundary of the light irradiation area 301, the two line segments other than the lower boundary line 301a and the upper boundary line 301b are referred to as lateral boundary lines 301c and 301d. The lateral boundary line 301c is located on the right side of the light irradiation area 301 as seen from the light emitting element 202, and the lateral boundary line 301d is located on the left side of the light irradiation area 301 as seen from the light emitting element 202. The lateral boundary lines 301c and 301d are examples of boundary lines that do not move in response to the displacement of the contact surface 206a, but whose length changes when the contact surface 206a is displaced, as will be described later.

[0048] Light passing through the opening 306 along the upper edge of the opening 306 is specularly reflected by the light reflecting portion 207 and then reaches the lower boundary line 301a of the light irradiation area 301 of the light receiving element 204 without being blocked by the light-shielding wall 305. Therefore, the upper edge of the opening 306 defines the lower boundary line 301a of the light irradiation area 301. On the other hand, light passing through the opening 306 along the lower edge of the opening 306 is specularly reflected by the light reflecting portion 207 and then blocked by the light-shielding wall 305, and does not reach the light receiving element 204. Therefore, the lower edge of the opening 306 does not define the light irradiation area 301. Therefore, the near incident light 211b is not narrowed by the diaphragm portion 209. Alternatively, light passing through the opening 306 along the lower edge of the opening 306 may be specularly reflected by the light reflecting portion 207 and then reaches the light receiving element 204 without being blocked by the light-shielding wall 305. In this case, the lower side of the opening 306 defines the light irradiation area 301. In this configuration, the displacement signal remains constant as the displacement of the diaphragm 206 ranges from zero to a predetermined value. Thereafter, when the lower side of the opening 306 no longer defines the light irradiation area 301, the displacement signal begins to decrease monotonically.

[0049] Light that passes through the opening 306, is specularly reflected by the light reflecting portion 207, and then passes through the opening 307 along the upper edge of the opening 307 reaches the upper boundary line 301b of the light irradiation region 301 of the light receiving element 204. Therefore, the upper edge of the opening 307 defines the upper boundary line 301b of the light irradiation region 301. In other words, the upper edge of the opening 307 is an example of an aperture section that narrows down the light specularly reflected by the light reflecting portion 207. On the other hand, light does not pass through the portion along the lower edge of the opening 307 because it is blocked by the light-shielding wall 304. Therefore, the lower edge of the opening 307 does not define the light irradiation region 301.

[0050] 3A , the lateral boundary lines 301c and 301d of the light irradiation region 301 are defined by the right and left sides of the opening 307. Alternatively, the lateral boundary lines 301c and 301d of the light irradiation region 301 may be defined by the right and left sides of the opening 306.

[0051] The reflected light of the distant incident light 211a is referred to as the lower-end reflected light 212a. The lower-end reflected light 212a is the light of the reflected light 212 located lowest in the z-axis direction (i.e., the portion closest to the diaphragm 206). The lower-end reflected light 212a reaches the lower boundary 301a of the light irradiation area 301. The lower boundary 301a is formed by light that is narrowed by the diaphragm unit 209 and specularly reflected by the light reflecting unit 207. The lower-end reflected light 212a is away from each side of the opening 307. In other words, the lower-end reflected light 212a is not narrowed by the diaphragm unit 210. In the configurations of FIGS. 3A and 3B , the lower boundary 301a includes the position of the light irradiation area 301 closest to the diaphragm 206 in the normal direction (i.e., the z-axis direction) of the diaphragm 206 when not pressed by the biological surface 320. 3A and 3B , the lower boundary line 301 a includes a position in the light irradiation area 301 where light reaches with the maximum reflection angle at the light reflecting portion 207. This maximum reflection angle is equal to the maximum incident angle 303 a. Furthermore, in the configurations of FIGS. 3A and 3B , the lower boundary line 301 a includes a position farthest from the light emitting element 202 in a plan view of the diaphragm 206 when it is not pressed.

[0052] The reflected light of the near incident light 211b is referred to as upper edge reflected light 212b. The upper edge reflected light 212b is the light of the reflected light 212 located at the top in the z-axis direction (i.e., the portion farthest from the diaphragm 206). The upper edge reflected light 212b reaches the upper boundary line 301b of the light irradiation area 301. In the configurations of FIGS. 3A and 3B , the upper boundary line 301b includes the position in the light irradiation area 301 farthest from the diaphragm 206 in the normal direction of the diaphragm 206 in the unpressed state (i.e., the z-axis direction). Also, in the configurations of FIGS. 3A and 3B , the upper boundary line 301b includes the position in the light irradiation area 301 reached by the light with the smallest reflection angle at the light reflecting portion 207. This minimum reflection angle is equal to the minimum incident angle 303b. Furthermore, in the configurations of FIGS. 3A and 3B, the upper boundary line 301b includes the position closest to the light emitting element 202 in a plan view of the diaphragm 206 in an unpressured state.

[0053] 3C and 3D , when the diaphragm 206 is pressed by the biological surface 320, the positions of the effective range 300, far boundary 300a, near boundary 300b, light irradiation region 301, lower boundary 301a, and upper boundary 301b all change. The portion of the reflected light 212 farthest from the light-emitting element 202 in the x-axis direction is referred to as the lower-end reflected light 212a. The lower-end reflected light 212a reaches the lower boundary 301a of the light irradiation region 301. As described above, the lower boundary 301a is defined by the upper edge of the opening 306 of the diaphragm unit 209 on the light-emitting element 202 side. The lower boundary 301a moves in response to the displacement of the contact surface 206a due to the elastic deformation of the diaphragm 206, which changes the area of ​​the light irradiation region 301 and the output of the light-receiving element 204, as described below.

[0054] Lower boundary line 301a is displaced by a displacement factor G relative to the displacement of diaphragm 206. The position at which the farthest portion of reflected light 212 from light emitting element 202 (in three-dimensional space, regardless of the x-axis direction) reaches light receiving element 204 is also displaced by the displacement factor G. Displacement factor G has a value that depends on the angle of incidence of incident light 211 on light reflecting portion 207 and the angle of the light receiving surface of light receiving element 204 relative to light reflecting portion 207. Chestpiece 110 may be configured so that displacement factor G is greater than 1.5, or may be configured so that displacement factor G is greater than 2.

[0055] As shown in FIGS. 3A to 3D , the upper boundary line 301b is defined by the portion of the light-shielding wall 305 that is above the reflected light 212, and is a boundary line that does not move in response to displacement of the contact surface 206a and whose length does not change even when displacement of the contact surface 206a occurs. The portion of the light-shielding wall 304 that is below the incident light 211 does not need to block the light emitted from the light-emitting element 202. For example, the portion of the light-shielding wall 304 that is below the incident light 211 does not need to be provided. Furthermore, the lower boundary line 301a is defined by the portion of the light-shielding wall 304 that is above the incident light 211. Therefore, the portion of the light-shielding wall 305 that is below the reflected light 212 does not need to block the light specularly reflected by the light reflecting portion 207. For example, the portion of the light-shielding wall 305 that is below the reflected light 212 does not need to be provided.

[0056] [Changes in the Reach Range of Reflected Light in the Electronic Auscultation Device of the First Embodiment] With reference to Fig. 3E, changes in the light irradiation area 301 formed by the reflected light 212 reaching the light receiving surface of the light receiving element 204 will be described. Fig. 3E shows a plan view of the light receiving surface of the light receiving element 204. The left side of Fig. 3E shows the position of the light irradiation area 301 when the diaphragm 206 is not pressed. The right side of Fig. 3E shows the position of the light irradiation area 301 when the diaphragm 206 is pressed by the biological surface 320.

[0057] To explain the directions, a coordinate system CS' is attached to Figure 3E. The coordinate system CS' is a two-dimensional Cartesian coordinate system having x' and y' axes that are orthogonal to each other. The y' axis coincides with the y axis of the coordinate system CS. The x' axis is parallel to the xz plane of the coordinate system CS. In the following description, the positive direction of the x' axis will be referred to as the upper side, and the negative direction of the x' axis will be referred to as the lower side.

[0058] The surface of the light receiving element 204 that faces the internal space 213 is the light receiving surface. The light receiving element 204 detects the amount of light that reaches the light receiving surface. As described above, in this embodiment, the light receiving element 204 is a single light receiving element. A line sensor or an area sensor may be used instead of a single light receiving element. The light receiving surface may have a rectangular shape. Of the four sides of the light receiving surface, the side that is parallel to the diaphragm 206 and closer to the diaphragm 206 is referred to as side 204a.

[0059] The area of ​​the light irradiation region 301 is determined by the lower boundary line 301a, the upper boundary line 301b, and the lateral boundary lines 301c and 301d. As shown in FIG. 3E , the lower boundary line 301a of the light irradiation region 301 changes in the x′-axis direction in response to the displacement of the contact surface 206a. On the other hand, the upper boundary line 301b and the lateral boundary lines 301c and 301d do not substantially move in response to the displacement of the contact surface 206a. Therefore, the area of ​​the light irradiation region 301 changes in response to the movement of the lower boundary line 301a. The length of the upper boundary line 301b does not change even when the contact surface 206a is displaced. On the other hand, the lengths of the lateral boundary lines 301c and 301d change when the contact surface 206a is displaced.

[0060] As the area of ​​the light-irradiated region 301 changes, the signal output from the light-receiving element 204 also changes. Specifically, the greater the displacement of the contact surface 206a of the diaphragm 206 from the flat state, the shorter the distance between the lower boundary 301a and the upper boundary 301b (i.e., the lengths of the lateral boundary lines 301c and 301d), and the smaller the area of ​​the light-irradiated region 301. Therefore, the greater the displacement of the diaphragm 206 from the flat state, the less light the light-receiving element 204 receives. Accordingly, the signal output from the light-receiving element 204 also becomes smaller. As shown in FIG. 3E , the amount of movement of the lower boundary 301a accompanying the movement of the light-reflecting portion 207 is greater than the amount of movement of the upper boundary line 301b accompanying the movement of the light-reflecting portion 207.

[0061] 3E, the change in the light irradiation area 301 in the x'-axis direction is larger than the change in the light irradiation area 301 in the y'-axis direction. Therefore, in order to increase the dynamic range of the light receiving element 204, the width of the light receiving element 204 in the x'-axis direction may be larger than the width of the light receiving element 204 in the y'-axis direction. More specifically, the width of the light receiving element 204 in the x'-axis direction may be three times or more the width of the light receiving element 204 in the y'-axis direction.

[0062] [Relationship between the displacement amount of the biological surface 320 and the displacement signal of the electronic auscultation device in the first embodiment] The relationship between the displacement amount of the biological surface 320 and the displacement signal will be described with reference to Fig. 4. The displacement signal is a voltage output from the optical receiver circuit board 205. A graph 400 in Fig. 4 shows the relationship between the displacement amount of the biological surface 320 and the displacement signal. The horizontal axis of the graph 400 represents the displacement amount of the biological surface 320, and represents the displacement signal generated by the optical receiver circuit board 205.

[0063] As described above, the displacement of the biological surface 320 is equal to the displacement of the upper surface of the light reflecting portion 207. The displacement of the upper surface of the light reflecting portion 207 is equal to the displacement of the diaphragm 206. As shown in FIG. 3E, as the displacement of the reflected light 212 increases, the amount of the reflected light 212 that reaches the light receiving element 204 decreases monotonically and linearly. Therefore, if the displacement of the biological surface 320 is d and the value of the displacement signal is S, then: S = Vmax - k × d (Equation 1) Here, Vmax is the value of the displacement signal when the displacement d is zero. Vmax is determined by the amount of light emitted by the light emitting element 202 and the sensitivity of the light receiving element 204. The sensitivity of the light receiving element 204 refers to the change in output voltage per unit amount of light incident on the light receiving element 204. The higher the sensitivity of the light receiving element 204, the larger Vmax becomes. Furthermore, Vmax increases as the amount of light emitted by the light-emitting element 202 increases. k is the amplification factor of the light-receiving element 204. k is also determined by the amount of light emitted by the light-emitting element 202 and the sensitivity of the light-receiving element 204. k increases as the sensitivity of the light-receiving element 204 increases. Furthermore, k increases as the amount of light emitted by the light-emitting element 202 increases.

[0064] The displacement amount d at which the displacement signal S becomes zero is represented as dmax. dmax is, for example, 1 mm. As the displacement amount d of the biological surface 320 increases, the area of ​​the light irradiation region 301 decreases and becomes zero. When the area of ​​the light irradiation region 301 becomes zero, the displacement signal S also becomes zero. The displacement amount d at which the area of ​​the light irradiation region 301 becomes zero is determined by the respective positions of the light receiving element 204 and the diaphragm unit 210 relative to the reflected light 212.

[0065] When the displacement d exceeds dmax, the reflected light 212 no longer reaches the light receiving element 204, and therefore, even if the displacement d increases, the displacement signal S remains zero. Therefore, the chestpiece 110 is configured so that the displacement d is in the range of 0 to dmax within the range in which the diaphragm 206 is expected to vibrate (referred to as the operating range of the diaphragm 206). As shown in graph 400, the light emitting element 202 and the light receiving element 204 are positioned so that the amount of light reaching the light receiving element 204 (amount of received light) changes monotonically as the light reflecting portion 207 moves in one direction within the operating range of the diaphragm 206. In the example of FIG. 4, the light receiving element 204 is positioned so that the amount of received light monotonically decreases, but the light receiving element 204 may also be positioned so that the amount of received light monotonically increases.

[0066] In this embodiment, the light emitting element 202 and the light receiving element 204 are arranged so that when the diaphragm 206 is flat, all of the reflected light 212 reaches the light receiving element 204. Alternatively, the light emitting element 202 and the light receiving element 204 may be arranged so that when the diaphragm 206 is in a position displaced downward from the flat position, all of the reflected light 212 reaches the light receiving element 204.

[0067] In the above-described embodiment, the normal to the light receiving surface of the light receiving element 204 is inclined with respect to the z-axis direction (i.e., the normal direction to the diaphragm 206). Alternatively, the normal to the light receiving surface of the light receiving element 204 may coincide with the z-axis direction. In other words, the light receiving surface is parallel to the diaphragm 206.

[0068] The chestpiece 110 according to the above-described embodiment can accurately detect the displacement of the biological surface 320. Specifically, in the above-described chestpiece 110, when a biological surface, which is an example of a measurement target, is in close contact with the diaphragm 206, a displacement signal is generated based on the displacement of the biological surface 320, which vibrates integrally with the diaphragm 206. Therefore, regardless of the frequency at which the biological surface 320 vibrates, the displacement of the biological surface 320 can be accurately detected. For example, the displacement of the biological surface 320 due to low-frequency vibrations of approximately 10 Hz can also be accurately detected. Such low-frequency vibrations are included in sounds (e.g., heart sounds) generated by vibrations propagated from within the body due to heartbeats. In the chestpiece 110, the displacement signal does not change unless the diaphragm 206 is displaced. Therefore, ambient sounds and vibrations or accelerations due to movement of the chestpiece 110 are not detected as noise, resulting in output characteristics with a high S / N ratio.

[0069] [Hardware Configuration of the Electronic Auscultation Device in the First Embodiment] Referring to FIG. 5 , an example of the hardware configuration of the electronic auscultation device 100 will be described. The electronic auscultation device 100 includes the chestpiece 110 and a sound output unit 510. The sound output unit 510 is implemented by multiple circuit elements mounted on a circuit board included in the grip unit 120. The multiple circuit elements include a processor. The processor constituting the sound output unit 510 transmits a sound signal based on a displacement signal generated by the chestpiece 110 to an external sound output device. The sound signal transmitted by the sound output unit 510 represents the body sound of a living body (e.g., a human) having a body surface 320, and is therefore also referred to as a biosignal. The sound signal is transmitted to a sound output device 520, such as earphones or headphones. The sound signal is also transmitted to a computer 530 (e.g., a personal computer, smartphone, tablet, etc.) simultaneously with the transmission to the sound output device 520. A user such as a doctor, nurse, or public health nurse can listen to the body sounds represented by the digitally converted sound signals using the sound output device 520 or the computer 530. The sound output device 520 is a wired or wireless earphone or headphone.

[0070] The sound output unit 510 has the components shown in FIG. 5 . Since the sound output unit 510 conforms to the earphones or headphones, it can transmit sound signals both wirelessly and via wired communication. The following describes the process by which the sound output device 520 outputs a sound signal via wired communication. The displacement signal output from the chestpiece 110 is filtered and amplified by the filter / amplifier 518 and supplied to the A / D converter 511 and the amplifier 515. The amplifier 515 further amplifies the output from the filter / amplifier 518 and supplies it to the wired communication unit 517. The wired communication unit 517 provides the amplified sound signal to the sound output device 520. The wired communication unit 517 is, for example, a 3.5 mm AUX terminal. The amplification gain of the amplifier 515 is adjusted by the volume adjustment unit 516. The sound output device 520 may be considered to constitute a part of the electronic auscultation device 100. In this case, the electronic auscultation device 100 includes a chestpiece 110 , a grip portion 120 , and a sound output device 520 .

[0071] Next, the process by which the sound output device 520 outputs a sound signal via wireless communication will be described. The A / D converter 511 digitizes the output from the filter / amplifier 518. The digital displacement signal is then amplified by the amplifier 512 and supplied to the encoder 513. The encoder 513 performs signal processing, such as data compression and encoding, on the amplified sound signal to generate sound data for wireless communication. The order of processing by the amplifier 512 and the encoder 513 may be reversed. Then, a wireless communication unit 514 compliant with a wireless communication standard such as Bluetooth (registered trademark) provides the processed sound data to the sound output device 520. The amplification gain of the amplifier 512 is adjusted by the volume adjustment unit 516. Although the above-described example of the electronic auscultation device 100 is capable of outputting a sound signal via both wireless and wired communication, it may also be capable of outputting a sound signal via only one of these communication methods.

[0072] The transmission of sound signals to the computer 530 is similar to the transmission of sound signals to the sound output device 520. The computer 530 can also visually display waveform data generated based on the sound signals. The waveform data may be generated by the computer 530 or by the electronic auscultation device 100. Furthermore, part or all of the signal processing and sound output processing by the electronic auscultation device 100 may be performed by an external device (e.g., the sound output device 520 or the computer 530).

[0073] The electronic auscultation device 100 can accurately detect displacement of the biological surface 320 regardless of the frequency at which the biological surface 320 vibrates. Therefore, the electronic auscultation device 100 enables effective auscultation of both relatively low-frequency biological sounds, such as heartbeat sounds, emitted by the body due to heartbeats, and relatively high-frequency biological sounds, such as breathing sounds. Respiratory sounds are biological vibrations that include a frequency band (first frequency band) that includes components in a frequency range of, for example, 500 Hz to 1 kHz. Heartbeat sounds are biological vibrations that include a frequency band (second frequency band) that includes components in a frequency range of, for example, 30 Hz to 300 Hz.

[0074] The operation unit 123 of the electronic auscultation device 100 is provided with a mode switching button 123c. Pressing the mode switching button 123c switches the auscultation mode of the electronic auscultation device 100 between a mode suitable for auscultating heartbeat sounds (hereinafter referred to as the "heartbeat mode") and a mode suitable for auscultating breath sounds (hereinafter referred to as the "breathbeat mode"). The electronic auscultation device 100 may have an auscultation mode other than the heartbeat sound mode and the breathbeat mode. When auscultating heartbeat sounds, the user operates the mode switching button 123c provided on the operation unit 123 to select the heartbeat sound mode, which is one of the auscultation modes. On the other hand, when auscultating breath sounds, the user operates the mode switching button 123c provided on the operation unit 123 to select the breath sound mode, which is one of the auscultation modes.

[0075] The operation unit 123 is provided with volume adjustment buttons 123a and 123b for adjusting the gain of the displacement signal output by the electronic auscultation device 100. The volume adjustment buttons 123a and 123b are used to adjust the volume of the sound output by the electronic auscultation device 100. Furthermore, the display unit 122 of the electronic auscultation device 100 is provided with an LED as an indicator that displays whether the current auscultation mode is the heartbeat sound mode or the breath sound mode. Depending on the lighting state of this LED, the user can visually determine whether the current operating mode is the heartbeat sound mode or the breath sound mode. Note that the heartbeat sound mode and the breath sound mode are each an example of an auscultation mode.

[0076] [Characteristics of Heartbeat Sounds and Breathing Sounds and Amplification Processing According to a Comparative Example] The characteristics of heartbeat sounds and breathing sounds and amplification processing according to a comparative example will be described with reference to Fig. 6. In the comparative example, regardless of whether heartbeat sounds or breathing sounds are auscultated, the sound signal obtained by amplifying the amplitude of the vibration of diaphragm 206 with the same amplification factor is A / D converted by A / D converter 511. The upper side of Fig. 6 shows the case where breathing sounds are auscultated, and the lower side of Fig. 6 shows the case where heartbeat sounds are auscultated. In Fig. 6, graph 400 is the same as the graph described above in Fig. 4. Graphs 601 to 604 show the change over time in the sound signal, with the horizontal axis representing time and the vertical axis representing voltage.

[0077] First, a case where respiratory sounds are auscultated will be described. w1 represents the peak-to-peak value of the vibration of the diaphragm 206 due to respiratory sounds. Typically, w1 is approximately 1 to 5 μm. As described above, the light-receiving element 204 amplifies the displacement of the diaphragm 206 by an amplification factor k (Equation 1 described above). Therefore, the peak-to-peak value w2 of the vibration of the displacement signal due to respiratory sounds is k×w1.

[0078] A high-pass filter (HPF) is then applied to the displacement signal to attenuate the DC component and camera shake component contained in the displacement signal. Graph 601 represents the displacement signal after the HPF has been applied, i.e., the respiratory sound signal. Voltage Vref represents the baseline of vibration (e.g., 1.5 V), and voltage Vcap represents the upper limit of the voltage that can be converted by the A / D converter 511 (e.g., 3.3 V). The A / D converter 511 converts voltages in the range of 0 to Vcap into digital values. Hereinafter, the range that can be converted by the A / D converter 511 will be referred to as the conversion range of the A / D converter 511.

[0079] After the HPF is applied, the breathing sound signal is amplified by 300 times by the amplifier circuit. Graph 602 shows the breathing sound signal after amplification. In the example of graph 602, the breathing sound signal falls within the conversion range of the A / D converter 511.

[0080] Next, a case where heartbeat sound is auscultated will be described. w3 represents the peak-to-peak value of the vibration of diaphragm 206 due to heartbeat sound. Typically, w3 is a value of approximately 20 to 40 μm. The peak-to-peak value w4 of the vibration of the displacement signal due to heartbeat sound is k×w3.

[0081] The HPF is then applied to the displacement signal to attenuate the DC component and the camera shake component contained in the displacement signal. A graph 603 represents the displacement signal, i.e., the heartbeat sound signal, after the HPF has been applied.

[0082] After the HPF is applied, the heartbeat sound signal is amplified by 300 times by the amplifier circuit. Graph 604 shows the amplified heartbeat sound signal. In the example of graph 602, the heartbeat sound signal does not fall within the conversion range of the A / D converter 511.

[0083] The amplitude of the vibration of diaphragm 206 due to heartbeat sounds is several tens to 100 times the amplitude of the vibration of diaphragm 206 due to respiratory sounds. Therefore, as shown in Figure 6, if the amplitude of the vibration of diaphragm 206 is amplified by the same amplification factor (e.g., 300 times) regardless of whether heartbeat sounds or respiratory sounds are being auscultated, the heartbeat sounds, which have large amplitudes, cannot be properly auscultated. On the other hand, if the amplification factor of the amplifier circuit is reduced (e.g., to 100 times) so that the heartbeat sound signal falls within the conversion range of A / D converter 511, the amplitude of the respiratory sound signal will decrease, resulting in a lower S / N ratio.

[0084] Therefore, in this embodiment, the electronic auscultation device 100 sets, for each operation mode, the amount of fluctuation in the output value of the sound signal per unit vibration amount of the diaphragm 206. Specifically, the electronic auscultation device 100 according to this embodiment sets the amount of fluctuation in the output value of the sound signal per unit vibration amount of the diaphragm 206 when the breath sound mode (first mode) is selected to be larger than the amount of fluctuation in the output value of the sound signal per unit vibration amount of the diaphragm 206 when the heartbeat sound mode (second mode) is selected.

[0085] The electronic auscultation device 100 does not need to change the amount of fluctuation in the output value of the sound signal so that the breath sound signal and the heartbeat sound signal supplied to the A / D converter 511 have similar amplitudes. Generally, low-frequency sounds are harder for the human ear to hear than high-frequency sounds. For example, it is known that the sound pressure level of a heartbeat sound, which sounds like a 20-phon sound to humans, is about 70 decibels lower than the sound pressure level of a breath sound, which sounds like the same 20-phon sound to humans. However, the difference between the amplitude of the breath sound vibration and the heartbeat sound vibration is greater than the difference in sound pressure levels. Therefore, when the breath sound mode is selected, the electronic auscultation device 100 increases the amount of fluctuation in the output value of the sound signal per unit vibration of the diaphragm 206 compared to when the heartbeat sound mode is selected.

[0086] In an electronic auscultation device using a piezoelectric element, there is no need to set the amount of fluctuation in the output value of the sound signal as in the present disclosure. In the frequency band including breathing sounds and heartbeat sounds, the higher the frequency, the greater the gain of the piezoelectric element. Therefore, even if breathing sounds and heartbeat sounds are amplified with the same amplification factor, the breathing sounds sound louder to humans. On the other hand, in the electronic auscultation device 100 using an optical sensor as in this embodiment, the output characteristics of the light-receiving element 204 are constant in the frequency band including breathing sounds and heartbeat sounds. Therefore, the amount of fluctuation in the output value of the sound signal is set as described above.

[0087] [Setting the amount of variation due to sensitivity of the light receiving element in the first embodiment] A method for changing the amount of variation in the output value of the sound signal per unit vibration amount of the diaphragm 206 will be described with reference to Fig. 7. In the example of Fig. 7, the amount of variation in the output value of the sound signal per unit vibration amount of the diaphragm 206 is changed by setting the amplification factor of the light receiving element 204. The upper side of Fig. 7 shows settings in the breath sound mode, and the lower side of Fig. 7 shows settings in the heartbeat sound mode. Graphs 701 to 704 show changes in the sound signal over time, with the horizontal axis representing time and the vertical axis representing voltage.

[0088] 7, graphs 705 and 706 represent the relationship between the displacement amount of the biological surface 320 and the displacement signal, similar to graph 400 in Fig. 4. In this embodiment, the amplification factor of the light receiving element 204 in the heartbeat sound mode is set to be smaller than the amplification factor of the light receiving element 204 in the breath sound mode. Therefore, the absolute value of the slope of graph 706 is smaller than the absolute value of the slope of graph 705.

[0089] First, the settings in the breath sound mode will be described. w1 is the same as in the description of FIG. 6. In the breath sound mode, the light receiving element 204 amplifies the displacement of the diaphragm 206 with an amplification factor k1. Therefore, the peak-to-peak value w5 of the vibration of the displacement signal due to breath sounds is k1 × w1.

[0090] The HPF is applied to the displacement signal to attenuate the DC component and the camera shake component contained in the displacement signal.Graph 701 represents the displacement signal, i.e., the breath sound signal, after the HPF is applied.

[0091] After the HPF is applied, the breathing sound signal is amplified by 300 times by the amplifier circuit. Graph 702 shows the breathing sound signal after amplification. In the example of graph 702, the breathing sound signal falls within the conversion range of the A / D converter 511.

[0092] Next, the settings in the heartbeat mode will be described. w3 is the same as in the description of FIG. 6. In the heartbeat mode, the light receiving element 204 amplifies the displacement of the diaphragm 206 by an amplification factor k2 (k2<k1). Therefore, the peak-to-peak value w6 of the vibration of the displacement signal due to the heartbeat sound is k2×w3.

[0093] The HPF is applied to the displacement signal to attenuate the DC component and the camera shake component contained in the displacement signal. A graph 703 represents the displacement signal, i.e., the heartbeat sound signal, after the HPF is applied.

[0094] After the HPF is applied, the heartbeat sound signal is amplified by 300 times by the amplifier circuit. Graph 704 shows the amplified heartbeat sound signal. In the example of graph 702, the heartbeat sound signal falls within the conversion range of the A / D converter 511.

[0095] As described above, in this embodiment, when the breath sound mode is selected, the displacement signal generated at a specific amplification factor (k1) is further amplified by the amplifier circuit and supplied to the A / D converter 511 for A / D conversion into a digital signal. On the other hand, when the heartbeat sound mode is selected, the displacement signal generated at a lower amplification factor (k2) than the specific amplification factor is further amplified by the amplifier circuit and supplied to the A / D converter 511 for A / D conversion into a digital signal. This allows the sound signal to be appropriately converted into a digital signal in both the breath sound mode and the heartbeat sound mode.

[0096] [Circuit Configuration of Electronic Auscultation Device in First Embodiment] An example of the circuit configuration of the electronic auscultation device 100 will be described with reference to Fig. 8A. The circuit configuration in Fig. 8A is a diagram showing in more detail the hardware configuration in Fig. 6.

[0097] The chestpiece 110 includes a light-emitting element 202 and a light-receiving element 204. Furthermore, in the example of FIG. 8A , the chestpiece 110 also includes a three-axis acceleration sensor 850. The acceleration sensor 850 is a sensor that measures three-dimensional acceleration. The acceleration sensor 850 is a sensor for detecting motion of the electronic auscultation device 100, for example, detecting that the electronic auscultation device 100 has been picked up by a user. In other words, the acceleration sensor 850 is used to determine whether the electronic auscultation device 100 is in use. In this embodiment, the acceleration sensor 850 is included in the chestpiece 110, but it may also be included in the grip portion 120 instead of the chestpiece 110. Furthermore, if a different configuration is adopted to determine the use state of the electronic auscultation device 100, the acceleration sensor 850 need not be included.

[0098] 1A , the grip unit 120 includes a display unit 122, an operation unit 123, a power switch 124, and a connector 125. The grip unit 120 further includes a microcontroller 800, a power supply unit 810, a UART integrated circuit 820, and a signal processing unit 830. The multiple circuit elements included in the grip unit 120 may be mounted on the same circuit board included in the grip unit 120, or may be distributed and mounted on multiple circuit boards.

[0099] The microcontroller 800 is a control means that controls the overall operation of the electronic auscultation device 100. In FIG. 8A, the electronic auscultation device 100 includes one or more microcontrollers 800. The microcontroller 800 includes a processor 801, a nonvolatile memory 802, a Bluetooth® circuit 803, and a RAM 804. The processor 801 controls the operation of the electronic auscultation device 100 by executing programs stored in the nonvolatile memory 802. The nonvolatile memory 802 is a storage means for storing programs that define the operation of the electronic auscultation device 100 and various setting data, and retains its stored contents even without external power. The Bluetooth circuit 803 is a control unit that controls the wireless communication unit 514, which complies with the Bluetooth wireless communication standard. The wireless communication unit 514 includes an antenna for wireless communication. In FIG. 8A , the microcontroller 800 includes a built-in Bluetooth circuit 803; however, the Bluetooth circuit 803 may be external to the microcontroller 800. The RAM 804 is a storage unit that temporarily stores programs and various setting data read from the nonvolatile memory 802. The microcontroller 800 is implemented by multiple circuit elements mounted on a circuit board included in the grip portion 120. The microcontroller 800 transmits a sound signal based on a displacement signal generated by the light receiving element 204 to an external sound output device via the wireless communication unit 514 or the wired communication unit 517. The sound output device 520 is, for example, a wired or wireless earphone or headphone. The microcontroller 800 can transmit the sound signal to the sound output device 520 as well as to a computer 530 (e.g., a personal computer, smartphone, tablet, etc.). A doctor, nurse, or public health nurse can listen to the body sounds represented by the digitally converted sound signals using the sound output device 520 or the computer 530. The displacement signal output from the light receiving element 204 is filtered and amplified by a signal processing unit 830 (described later) and supplied to an A / D converter 511. The A / D converter 511 digitizes the output from the signal processing unit 830.The digital displacement signal is then subjected to signal processing, such as data compression and encoding, by the microcontroller 800 using an encoder in accordance with a communication standard, and converted into sound data for wireless communication. This conversion to sound data is, for example, conversion into Pulse Code Modulation (PCM) format. The wireless communication unit 514, which complies with a wireless communication standard such as Bluetooth®, then transmits the PCM-formatted sound data to the sound output device 520. Upon receiving the sound data, the sound output device 520 outputs sound corresponding to the sound data. While the electronic auscultation device 100 described above is capable of transmitting sound data via both wireless and wired communication, it may also be capable of transmitting sound via only one of these communication methods. Transmission of sound data to the computer 530 is similar to transmission of sound data to the sound output device 520. The computer 530 can also visually display waveform data generated based on the received sound data. The waveform data may be generated by either the computer 530 or the electronic auscultation device 100. Furthermore, some or all of the signal processing and sound output processing performed by the electronic auscultation device 100 may be performed by an external device (for example, the sound output device 520 or the computer 530).

[0100] The UART integrated circuit 820 is connected to both the microcontroller 800 and the connector 125 (specifically, its data terminal). The UART integrated circuit 820 performs communication in accordance with the UART standard. The UART integrated circuit 820 and the connector 125 function as the wired communication unit 517. The microcontroller 800 may be able to communicate with an external device via a wired connection through the UART integrated circuit 820 and the connector 125. The UART integrated circuit 820 may also be connected to a power supply terminal of the connector 125. A voltage VBUS may be applied to the UART integrated circuit 820 from an external device (e.g., a charger or a computer 530) connected to the connector 125 through the power supply terminal of the connector 125. The UART integrated circuit 820 may be able to operate using the voltage VBUS as its operating voltage.

[0101] The power supply unit 810 includes a battery 811, a charging integrated circuit 812, a boost converter 813, a voltage regulator 814, a load switch 815, and a voltage regulator 816. The power supply unit 810 supplies power to a plurality of circuit elements included in the electronic auscultation device 100. The power supply unit 810 may supply power at a plurality of different voltages. Alternatively, the power supply unit 810 may supply power at a single voltage and may drop the voltage at a stage preceding each circuit element to an appropriate operating voltage.

[0102] The battery 811 stores electrical energy used by the electronic auscultation device 100. The battery 811 may have a function of cutting off the current when the current flowing through the battery 811 exceeds a threshold. The charging integrated circuit 812 is an integrated circuit (IC) that controls charging to and discharging from the battery 811. For example, the charging integrated circuit 812 charges the battery 811 using electrical energy supplied from an external device such as a charger connected to the connector 125 or the computer 530. The charging integrated circuit 812 also supplies the electrical energy stored in the battery 811 to the boost converter 813. The voltage provided by the charging integrated circuit 812 is referred to as voltage VBAT. The voltage VBAT is, for example, 3.7 V.

[0103] The boost converter 813 boosts a DC voltage to another DC voltage. The boost converter 813 is also called a DC / DC converter. The boost converter 813 boosts the voltage VBAT supplied from the charging integrated circuit 812 to a voltage V0. The voltage V0 is, for example, 6.8 V. The voltage regulator 814 generates and outputs a voltage of a specific value. The voltage regulator 814 may be a linear regulator, also called a low-dropout regulator (LDO). The voltage regulator 814 generates operating voltages for some circuit elements of the electronic auscultation device 100. The voltage generated by the voltage regulator 814 is referred to as voltage V1. The voltage regulator 814 may generate an operating voltage for the microcontroller 800; for example, voltage V1 is 3.3 V. The operating voltage of the acceleration sensor 850 is also voltage V1. In the example of FIG. 8A , voltage V1 is applied to both the microcontroller 800 and the acceleration sensor 850. Power is supplied to the microcontroller 800 and the acceleration sensor 850 from a voltage regulator 814 in a power supply unit 810. The voltage regulator 814 outputs voltage V1 when a voltage higher than voltage V1 is applied to its input terminal. Therefore, when voltage V0 is supplied from the boost converter 813, the voltage regulator 814 outputs voltage V1.

[0104] The load switch 815 is a switch that switches between on (conducting state) and off (non-conducting state) in response to a control signal from the microcontroller 800. The voltage regulator 816 generates and outputs a voltage of a specific value. The voltage regulator 816 may be a linear regulator or an LDO. The voltage regulator 816 generates an operating voltage for some circuit elements of the electronic auscultation device 100. The voltage generated by the voltage regulator 816 is represented as voltage V2. The voltage regulator 816 may generate an operating voltage for the light-emitting element 202 and the light-receiving element 204; for example, voltage V2 is 5.8 V. In the example of FIG. 8A , voltage V2 is applied to each of the light-emitting element 202 and the light-receiving element 204. Power is supplied to the light-emitting element 202 and the light-receiving element 204 from the voltage regulator 816 of the power supply unit 810. The voltage regulator 816 outputs voltage V2 when a voltage higher than voltage V2 is applied to its input terminal. Therefore, the voltage regulator 816 outputs the voltage V2 when the load switch 815 is on. The voltage regulator 816 does not output the voltage V2 when the load switch 815 is off. When the voltage regulator 816 does not output the voltage V2, the potential of the output terminal of the voltage regulator 816 is the ground potential.

[0105] The signal processing unit 830 processes the displacement signal to generate a sound signal representing the sound transmitted from the biological surface 320 to the diaphragm 206, and outputs this sound signal to the microcontroller 800. Specifically, the signal processing unit 830 extracts components of a specific frequency band contained in the displacement signal to generate the sound signal. The displacement signal is a signal generated and output by the light receiving element 204 in accordance with the amount of light reaching the light receiving element 204. The amount of light reaching the light receiving element 204 changes in accordance with the displacement of the diaphragm 206. Note that, as described above, if the light emitting element 202 is a laser diode that emits laser light, the displacement signal may be a signal generated and output by the light receiving element 204 in accordance with the position of the light reaching the light receiving element 204. Even when realized with a laser diode, the displacement signal still represents the displacement of the diaphragm 206.

[0106] The signal processing unit 830 includes a signal path between the light receiving element 204 and the microcontroller 800, which includes a buffer circuit 831, an HPF 832, and amplifier circuits 833 and 834 (fourth amplifier circuits) with low-pass filters. These circuit elements are connected in series. The signal processing unit 830 amplifies the displacement signal received from the light receiving element 204 through this signal path and supplies the amplified signal to the microcontroller 800. As will be described later, a digital signal based on the signal output from the amplifier circuit 834 is output to the outside as a sound signal in each of the breath sound mode and the heartbeat sound mode. Therefore, the signal output from the amplifier circuit 834 is referred to as a sound signal.

[0107] The buffer circuit 831 receives a displacement signal from the light receiving element 204 and outputs the displacement signal to the HPF 832. The buffer circuit 831 converts the impedance of the signal path between the light receiving element 204 and the HPF 832. For example, the output impedance of the buffer circuit 831 is lower than the output impedance of the light receiving element 204. The operating power of the buffer circuit 831 is supplied from the voltage regulator 816.

[0108] The HPF 832 attenuates low-frequency components (i.e., frequency components lower than a specific cutoff frequency) of the displacement signal received from the buffer circuit 831 and passes high-frequency components (i.e., frequency components higher than the cutoff frequency) of the displacement signal, and outputs the resulting signal to the amplifier circuit 833. In order to extract the respiratory sound signal and the heartbeat sound signal, the cutoff frequency of the HPF 832 is, for example, a value within the range of 10 Hz to 100 Hz (e.g., 10 Hz).

[0109] The HPF 832 is disposed on the signal path between the light receiving element 204 and the microcontroller 800 and removes or attenuates low-frequency noise contained in the displacement signal. The low-frequency noise contained in the displacement signal is a component that does not originate from vibrations transmitted from the biological surface to the diaphragm 206. For example, the low-frequency noise may include components caused by the user's shaking of the electronic stethoscope device 100. The low-frequency noise may also include changes in the DC component caused by the diaphragm 206 being pressed against the biological surface. Such low-frequency noise has a significantly larger amplitude than the components originating from vibrations transmitted from the biological surface to the diaphragm 206 (hereinafter referred to as biological components). Therefore, by amplifying the displacement signal with suppressed low-frequency noise, biological components can be appropriately acquired within the dynamic range of the amplifier circuit. Note that instead of the HPF 832, a bandpass filter that removes components below a value in the range of 10 Hz to 100 Hz (e.g., 10 Hz) may be used.

[0110] 8A, a buffer circuit 831 is disposed on the signal path between the light receiving element 204 and the HPF 832. By lowering the output impedance of the circuit elements preceding the HPF 832 in this way, sufficient power is supplied to the capacitor of the HPF 832, improving the output characteristics of the signal from the HPF 832. This improves the quality of the heartbeat sound signal.

[0111] The amplifier circuit 833 amplifies the signal received from the HPF 832, attenuates high-frequency components, and passes low-frequency components. The amplifier circuit 833 attenuates high-frequency noise contained in the displacement signal and outputs the displacement signal to the amplifier circuit 834. The cutoff frequency of the amplifier circuit 833 is 1 kHz in this embodiment. However, the cutoff frequency of the amplifier circuit 833 may be 1 kHz or less, for example, 950 Hz or 900 Hz. The cutoff frequency of the amplifier circuit 833 may also be 1 kHz or more and less than 2 kHz. The operating power of the amplifier circuit 833 is supplied from the voltage regulator 816. The amplification factor of the amplifier circuit 833 is, for example, 150 times.

[0112] The amplifier circuit 834 amplifies the signal received from the amplifier circuit 834, attenuates high-frequency components of the signal, and outputs a signal with low-frequency components passed through to the microcontroller 800. The cutoff frequency of the amplifier circuit 834 may be the same as or different from the cutoff frequency of the amplifier circuit 833. The operating power of the amplifier circuit 834 is supplied from the voltage regulator 816. The amplification factor of the amplifier circuit 833 is, for example, 2x.

[0113] Both amplifier circuits 833 and 834 may be inverting amplifier circuits. In this case, the two amplifier circuits 833 and 834 are connected in series, so that the polarity of the displacement signal and the polarity of the heartbeat sound signal match. Alternatively, the signal processing unit 830 may include only one amplifier circuit with a low-pass filter, which may be a non-inverting amplifier circuit. Furthermore, the polarity of the displacement signal and the polarity of the heartbeat sound signal may be different from each other.

[0114] In this embodiment, the amplifier circuits 833 and 834 include low-pass filters, but the amplifier circuits 833 and 834 may not include low-pass filters. In this case, another low-pass filter may be disposed on the signal path between the HPF 832 and the microcontroller 800. Furthermore, a band-pass filter may be disposed on this signal path instead of the low-pass filter.

[0115] When the breath sound mode is selected, the microcontroller 800 A / D converts the sound signal supplied from the amplifier circuit 834 to generate a digital signal representing the breath sound and outputs this digital signal to the outside. On the other hand, when the heartbeat sound mode is selected, the microcontroller 800 A / D converts the sound signal supplied from the amplifier circuit 834 to generate a digital signal representing the heartbeat sound and outputs this digital signal to the outside.

[0116] As shown in FIG. 8A , the signal processing unit 830 further outputs the displacement signal to the microcontroller 800 before it is processed by the HPF 832. In the example of FIG. 8A , a node 835 located on the signal path between the buffer circuit 831 and the HPF 832 is connected to the microcontroller 800. The displacement signal is output from this node 835 to the microcontroller 800. As will be described later, the microcontroller 800 detects the pressing state (also referred to as the contact state) of the diaphragm 206 based on this displacement signal and performs a volume setting operation, which will be described later. The displacement signal to the microcontroller 800 may also be output from another node on the signal path between the light receiving element 204 and the HPF 832. For example, the displacement signal to the microcontroller 800 may also be output from a node on the signal path between the light receiving element 204 and the buffer circuit 831.

[0117] In the example of FIG. 8A, other circuit elements may be disposed on the signal path between the buffer circuit 831 and the light receiving element 204.

[0118] The displacement signal, heartbeat sound signal, respiratory sound signal, and acceleration signal are supplied to corresponding input terminals of the microcontroller 800. The microcontroller 800 includes an A / D converter 511 that converts these analog signals into digital signals, and processing by the microcontroller 800 is performed using the digital signals.

[0119] The current control circuit 860 controls the current flowing through the light-emitting element 202. The current control circuit 860 has a control terminal 861. When a high-level signal is supplied to the control terminal 861, a current flows through the light-emitting element 202, and when a low-level signal is supplied to the control terminal 861, no current flows through the light-emitting element 202. In FIG. 8A , the current control circuit 860 is included in the grip portion 120, but at least some of the circuit elements of the current control circuit 860 may be included in the chestpiece 110.

[0120] The microcontroller 800 adjusts the current flowing through the light-emitting element 202 by supplying a control signal to a control terminal 861 of the current control circuit 860. The light-emitting element 202 emits light with an amount of light corresponding to the current flowing through the light-emitting element 202. Therefore, the microcontroller 800 has a function of adjusting the amount of light emitted by the light-emitting element 202 (light-emission amount adjustment function). Specifically, the microcontroller 800 supplies a pulse-width modulation signal to the control terminal 861 of the current control circuit 860. The microcontroller 800 adjusts the amount of light emitted by the light-emitting element 202 by changing the duty ratio of this pulse-width modulation signal.

[0121] When the breath sound mode is selected, the microcontroller 800 adjusts the light emission intensity of the light emitting element 202 to a specific light emission intensity (first light emission intensity), and when the heartbeat sound mode is selected, adjusts the light emission intensity of the light emitting element 202 to a light emission intensity (second light emission intensity) lower than the specific light emission intensity. Specifically, when the breath sound mode is selected, the microcontroller 800 sets the pulse width modulation signal to a specific duty ratio, and when the heartbeat sound mode is selected, sets the pulse width modulation signal to a duty ratio lower than the specific duty ratio.

[0122] [Modification of the circuit configuration of the electronic auscultation device in the first embodiment] A modification of the circuit configuration of the electronic auscultation device 100 in the first embodiment will be described with reference to Fig. 8B. Differences from Fig. 8A will be described below. The configuration of the current control circuit 860 differs between Fig. 8A and Fig. 8B.

[0123] The current control circuit 860 controls the current flowing through the light-emitting element 202. When a high-level signal is supplied to the control terminal 861, the transistor 862 turns on, and when a low-level signal is supplied to the control terminal 861, the transistor 862 turns off. Therefore, the resistance value of the current path passing through the light-emitting element 202 is lower when the control signal is off than when it is on. Therefore, the current flowing through the light-emitting element 202 is larger when the control signal is off than when it is on.

[0124] The microcontroller 800 adjusts the current flowing through the light-emitting element 202 by supplying a control signal to a control terminal 861 of the current control circuit 860. The light-emitting element 202 emits light of an amount corresponding to the current flowing through the light-emitting element 202. Therefore, the microcontroller 800 has a function of adjusting the amount of light emitted by the light-emitting element 202.

[0125] When the breath sound mode is selected, the microcontroller 800 adjusts the light emission intensity of the light emitting element 202 to a specific light emission intensity (first light emission intensity), and when the heartbeat sound mode is selected, adjusts the light emission intensity of the light emitting element 202 to a light emission intensity (second light emission intensity) that is smaller than the specific light emission intensity. Specifically, when the breath sound mode is selected, the microcontroller 800 turns on the transistor 862, and when the heartbeat sound mode is selected, the microcontroller 800 turns off the transistor 862.

[0126] According to the above embodiment, the amplitude of the vibration of the diaphragm 206 can be amplified by an appropriate amplification factor in both the breath sound mode and the heartbeat sound mode.

[0127] <Second embodiment> [Circuit configuration of electronic auscultation device in second embodiment] An example of the configuration of an electronic auscultation device 100 according to a second embodiment will be described with reference to Figures 9A and 9B. The following mainly describes the differences from the first embodiment. The second embodiment differs from the first embodiment in the method of setting the gain of the light receiving element 204. In the second embodiment, the gain of the light receiving element 204 is set by setting the sensitivity of the light receiving element 204.

[0128] The circuit configuration of the electronic auscultation device 100 in the second embodiment will be described with reference to Fig. 9A. Differences from Fig. 8A will be described below. Figs. 8A and 9A differ in the configuration of the power supply unit 810. Furthermore, the electronic auscultation device 100 in Fig. 9A includes a voltage control circuit 870 instead of the current control circuit 860. In Fig. 9A, the voltage control circuit 870 is included in the grip portion 120, but at least some of the circuit elements of the voltage control circuit 870 may be included in the chestpiece 110.

[0129] The power supply unit 810 further includes a voltage regulator 817 on the path between the load switch 815 and the voltage regulator 816. The voltage regulator 817 generates and outputs a voltage of a specific value. The voltage regulator 817 may be a linear regulator or an LDO. The voltage regulator 817 generates an operating voltage for some circuit elements of the electronic auscultation device 100. The voltage generated by the voltage regulator 817 is referred to as voltage V3. The voltage regulator 817 may generate an operating voltage for the light receiving element 204 when the breath sound mode is selected. For example, voltage V3 is 6.4 V. The voltage regulator 817 outputs voltage V3 when a voltage higher than voltage V3 is applied to its input terminal. Therefore, the voltage regulator 817 outputs voltage V3 when the load switch 815 is on. The voltage regulator 817 does not output voltage V3 when the load switch 815 is off. When voltage V3 is not output, the potential of the output terminal of the voltage regulator 816 is ground potential. Voltage regulator 816 generates voltage V2 as in Figure 8A. Voltage V3 is higher than voltage V2.

[0130] The voltage control circuit 870 changes the voltage supplied to the light receiving element 204. The voltage control circuit 870 has a control terminal 871. When a high-level signal is supplied to the control terminal 871, the transistor 872 is turned on and a voltage V3 is supplied to the light receiving element 204. When a low-level signal is supplied to the control terminal 871, the transistor 872 is turned off and a voltage V2 is supplied to the light receiving element 204.

[0131] The microcontroller 800 changes the voltage supplied to the light receiving element 204 by supplying a control signal to a control terminal 871 of the voltage control circuit 870. The light receiving element 204 generates a displacement signal with sensitivity according to the voltage supplied to the light receiving element 204. Therefore, the microcontroller 800 has a function of adjusting the sensitivity of the light receiving element 204 (sensitivity adjustment function).

[0132] When the breath sound mode is selected, the microcontroller 800 adjusts the sensitivity of the light receiving element 204 to a specific sensitivity (first sensitivity), and when the heartbeat sound mode is selected, adjusts the sensitivity of the light receiving element 204 to a sensitivity (second sensitivity) lower than the specific sensitivity. Specifically, when the breath sound mode is selected, the microcontroller 800 turns on the transistor 872, and when the heartbeat sound mode is selected, the microcontroller 800 turns off the transistor 872. Note that, regardless of whether the breath sound mode or the heartbeat sound mode is selected, the voltage V2 is supplied to the light emitting element 202, and the voltage V1 is supplied to the microcontroller 800. This reduces power consumption compared to when the voltage V3 is supplied to the light emitting element 202 and the microcontroller 800.

[0133] [Modification of the circuit configuration of the electronic auscultation device in the second embodiment] A modification of the circuit configuration of the electronic auscultation device 100 in the second embodiment will be described with reference to Fig. 9B. Differences from Fig. 9A will be described below. Figs. 9A and 9B differ in the configuration of the voltage control circuit 870. In addition, the power supply unit 810 in Fig. 9B does not include a voltage regulator 817.

[0134] The voltage control circuit 870 controls the resistance value of the current path passing through the light receiving element 204. When a high-level signal is supplied to the control terminal 871, the transistor 873 turns on, and when a low-level signal is supplied to the control terminal 871, the transistor 873 turns off. Therefore, the resistance value of the current path passing through the light receiving element 204 is lower when the control signal is off than when it is on. Therefore, the current flowing through the light receiving element 204 is larger when the control signal is off than when it is on.

[0135] The microcontroller 800 adjusts the current flowing through the light receiving element 204 by supplying a control signal to a control terminal 871 of the voltage control circuit 870. The sensitivity of the light receiving element 204 varies depending on the current flowing through the light receiving element 204. Therefore, the microcontroller 800 has a function of adjusting the sensitivity of the light receiving element 204.

[0136] When the breath sound mode is selected, the microcontroller 800 adjusts the sensitivity of the light receiving element 204 to a specific sensitivity (first sensitivity), and when the heartbeat sound mode is selected, adjusts the sensitivity of the light receiving element 204 to a light emission amount (second sensitivity) smaller than the specific sensitivity. Specifically, when the breath sound mode is selected, the microcontroller 800 turns on the transistor 873, and when the heartbeat sound mode is selected, the microcontroller 800 turns off the transistor 873.

[0137] According to the above embodiment, the amplitude of the vibration of the diaphragm 206 can be amplified by an appropriate amplification factor in both the breath sound mode and the heartbeat sound mode.

[0138] <Modifications of the Above-described Embodiments> In the first embodiment, the amount of variation in the output value of the sound signal per unit vibration amount of the diaphragm according to the auscultation mode was set by switching the light emission amount of the light-emitting element 202. In the second embodiment, the amount of variation in the output of the sound signal per unit vibration amount of the diaphragm according to the auscultation mode was set by switching the sensitivity of the light-receiving element 204. However, the amount of variation in the output value of the sound signal per unit vibration amount of the diaphragm 206 may be achieved by any combination of the methods of the first and second embodiments. Specifically, the amount of variation may be set by any combination of the light emission amount of the light-emitting element 202 and the sensitivity of the light-receiving element 204.

[0139] In the above-described embodiment, the chestpiece 110 includes only one light-emitting element 202. Alternatively, the chestpiece 110 may include multiple light-emitting elements 202. Light emitted by the multiple light-emitting elements 202 may be reflected by the light reflecting portion 207 and reach the light-receiving element 204. The light-receiving element 204 may detect the displacement of the diaphragm 206 based on the total amount of light received by the multiple light-receiving elements 204. The chestpiece 110 may include multiple light-receiving elements 204. Each of the multiple light-receiving elements 204 may receive light emitted from a separate light-emitting element 202 and reflected by the light reflecting portion 207. The displacement of the diaphragm 206 may be detected based on the total amount of light received by the multiple light-receiving elements 204.

[0140] In the above-described embodiment, the electronic auscultation device 100 generates a displacement signal (i.e., a signal representing the displacement of the diaphragm 206) based on the amount of light emitted from the light-emitting element 202, reflected by the light-reflecting element 207, and received by the light-receiving element 204. Alternatively, the electronic auscultation device 100 may have the light-emitting element 202 emit laser light toward the light-reflecting element 207. The laser light reflected by the light-reflecting element 207 reaches the light-receiving element 204. The position at which the laser light reaches the light-receiving element 204 varies depending on the displacement of the diaphragm 206. Therefore, the electronic auscultation device 100 may detect the displacement signal based on the position of the light received by the light-receiving element 204. When the light-emitting element 202 emits laser light, the chestpiece 110 does not need to include the apertures 209 and 210. When the light-emitting element 202 emits laser light, the light-receiving element 204 may be a two-dimensional area sensor or a one-dimensional line sensor.

[0141] Furthermore, in the above-described embodiment, the microcontroller 800 selects the auscultation mode based on an instruction from the user, but the mode may be selected automatically by the microcontroller 800 based on a displacement signal.

[0142] The electronic auscultation device described above is primarily intended as a diagnostic tool in which doctors, nurses, and public health nurses place a diaphragm on the surface of a patient's body to listen to heartbeat and breathing sounds. However, it is also conceivable that the electronic auscultation device could be used by general users other than medical professionals, rather than as a diagnostic tool. For example, it is conceivable that general users would use the electronic auscultation device for the purpose of promoting and managing their health. In such cases, the electronic auscultation device could be installed in a health management device that has the function of measuring vital data such as pulse rate and body temperature. Therefore, the electronic auscultation device of this embodiment can also be applied to a health management device that can simultaneously acquire biological information other than biological sounds.

[0143] Furthermore, the electronic auscultation device of this embodiment may be used for diagnosing animals other than humans, i.e., it goes without saying that it can be used as an electronic auscultation device for pets used by veterinarians.

[0144] The electronic auscultation device of this embodiment is sometimes referred to as a "displacement detection device" because it detects the displacement of a diaphragm. Aside from auscultation, the displacement detection device can also be used to detect abnormal industrial sounds. For example, when an abnormality occurs in a gas or water pipeline, low-frequency sounds that are difficult for the human ear to hear can be generated. The displacement detection device of this embodiment can be used as a device for identifying the source of such low-frequency sounds and listening for them. When using the displacement detection device for such purposes, a user contacts the diaphragm of the displacement detection device with a target object. The displacement detection device then detects the vibration of the target object, converts the displacement signal representing the vibration into a sound signal, and transmits it to a sound output device. This allows the user to identify the source of the low-frequency sound. Potential targets that are sources of low-frequency sounds include gas or water pipelines, as well as outdoor units of air conditioners. Motors, which are sources of vibration, can also be target objects. Various industrial machines can also be target objects. In other words, in addition to auscultation, the displacement detection device can be used for various purposes as a device that detects the vibration of a target object and outputs sound.

[0145] The present disclosure can also be realized by a process in which a program that realizes one or more functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present disclosure can also be realized by a circuit (e.g., an ASIC) that realizes one or more functions.

[0146] The technical ideas derived from this disclosure are not limited to the disclosed exemplary embodiments, but are intended to encompass various modifications to the exemplary embodiments, or the replacement of equivalent structures or functions, etc. The scope of the following claims should be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

[0147] This application claims priority based on Japanese Patent Application No. 2024-126146, filed August 1, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. An electronic auscultation device comprising: a diaphragm that comes into contact with a living body and vibrates together with the living body, the diaphragm having a light reflecting portion on the surface opposite to the contact surface that comes into contact with the living body; a light source; a light receiving element having a light receiving surface that receives light emitted from the light source and specularly reflected by the light reflecting portion, and generating a signal according to the amount of light that reaches the light receiving surface; a selection means that selects one of a plurality of modes including a first mode that measures living body vibrations including a first frequency band and a second mode that measures living body vibrations including a second frequency band lower than the first frequency band; and a light emission amount adjustment means that adjusts the light emission amount of the light source, wherein when the first mode is selected by the selection means, the light emission amount adjustment means adjusts the light emission amount of the light source to a first light emission amount, and when the second mode is selected by the selection means, adjusts the light emission amount of the light source to a second light emission amount that is smaller than the first light emission amount.

2. The electronic auscultation device according to claim 1, further comprising a current control circuit that controls the current flowing through the light source, and the light emission amount adjusting means adjusts the light emission amount of the light source by changing the duty ratio of the pulse width modulation signal supplied to the current control circuit.

3. The electronic auscultation device according to claim 1, wherein said light emission amount adjusting means adjusts the light emission amount of said light source by changing the resistance value of the current path passing through said light source.

4. The electronic auscultation device according to any one of claims 1 to 3, further comprising a sensitivity adjustment means for adjusting the sensitivity of the light-receiving element, wherein the sensitivity adjustment means adjusts the sensitivity of the light-receiving element to a first sensitivity when the first mode is selected by the selection means, and adjusts the sensitivity of the light-receiving element to a second sensitivity lower than the first sensitivity when the second mode is selected by the selection means.

5. An electronic auscultation device according to any one of claims 1 to 4, characterized in that the components of the first frequency band include components of a frequency band ranging from 500 Hz to 1 kHz, and the components of the second frequency band include components of a frequency band ranging from 30 Hz to 300 Hz.

6. An electronic auscultation device according to any one of claims 1 to 5, characterized in that the first mode is a mode for measuring respiratory sounds, and the second mode is a mode for measuring heartbeat sounds.

7. An electronic auscultation device as claimed in any one of claims 1 to 6, characterized in that the light source includes a light-emitting diode, the electronic auscultation device further comprises an aperture section for narrowing down the light emitted from the light-emitting diode, the light-receiving surface is arranged to receive light that passes through the aperture section and is specularly reflected by the light-reflecting section, and the signal generated by the light-receiving element is a signal corresponding to the area of ​​the light-irradiated region formed by the specularly reflected light that reaches the light-receiving surface.

8. An electronic auscultation device according to any one of claims 1 to 7, wherein said selection means selects one of said plurality of modes based on an instruction from a user.

9. An electronic auscultation device according to any one of claims 1 to 8, further comprising output means for outputting a digital signal based on the signal generated by said light receiving element to the outside.

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