Electronic auscultation device

Abstract

To amplify vibration measured by using an optical sensor at an appropriate amplification factor.SOLUTION: The electronic stethoscope apparatus includes a diaphragm that comes into contact with a living body and vibrates together with the living body and is provided with a light reflecting portion on a surface opposite to a contact surface, a light source, and a light receiving surface that receives light emitted from the light source and specularly reflected by the light reflecting portion. A light receiving element that generates a signal according to an amount of light reaching a light receiving surface, a selection unit that selects any one of a plurality of modes including a first mode for measuring biological vibration including a first frequency band and a second mode for measuring biological vibration including a second frequency band lower than the first frequency band, an output unit that outputs a digital signal based on a signal generated by the light receiving element to the outside, and a light emission amount adjustment unit that adjusts a light emission amount of a light source, the light emission amount adjustment part adjusts the light emission amount of the light source to be a first light emission amount when the first mode is selected, and adjusts the light emission amount of the light source to be a second light emission amount smaller than the first light emission amount when the second mode is selected.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to an electronic auscultation device. [Background technology]

[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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-75136 Summary of the Invention [Problem to be solved by the invention]

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

[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 according 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; an output means for outputting a digital signal based on the signal generated by the light-receiving element to the outside; 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. [Effects of the Invention]

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

[0007] [Figure 1A] 1 is a schematic diagram illustrating an example of the appearance of an electronic auscultation device according to a first embodiment. [Figure 1B] 1 is a schematic diagram illustrating an example of the appearance of an electronic auscultation device according to a first embodiment. [Figure 2] 1 is a schematic diagram illustrating a configuration example of a chest piece according to a first embodiment. [Figure 3A] 5A to 5C are schematic diagrams illustrating an example of the operation of the chestpiece of the first embodiment. [Figure 3B] 5A to 5C are schematic diagrams illustrating an example of the operation of the chestpiece of the first embodiment. [Figure 3C] 5A to 5C are schematic diagrams illustrating an example of the operation of the chestpiece of the first embodiment. [Figure 3D]5A to 5C are schematic diagrams illustrating an example of the operation of the chestpiece of the first embodiment. [Figure 3E] 5A and 5B are schematic diagrams illustrating an example of change in the light receiving range according to the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating the relationship between the displacement amount and the displacement signal according to the first embodiment. [Figure 5] 1 is a block diagram illustrating an example of the configuration of an electronic auscultation device according to a first embodiment. [Figure 6] 10A and 10B are diagrams illustrating the properties of heartbeat sounds and breathing sounds and amplification processing according to a comparative example. [Figure 7] FIG. 2 is a diagram for explaining the amplification process of the electronic auscultation device of the first embodiment. [Figure 8A] FIG. 1 is a block diagram illustrating an example of the circuit configuration of an electronic auscultation device according to a first embodiment. [Figure 8B] FIG. 4 is a block diagram illustrating a modified example of the circuit configuration of the electronic auscultation device of the first embodiment. [Figure 9A] FIG. 10 is a block diagram illustrating an example of the circuit configuration of an electronic auscultation device according to a second embodiment. [Figure 9B] FIG. 10 is a block diagram illustrating a modified example of the circuit configuration of the electronic auscultation device of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] 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 invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, 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.

[0009] 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. 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 heartbeats and respiratory sounds.

[0010] 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 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 later). 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.

[0011] 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.

[0012] 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.

[0013] 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 that indicates whether the power of the electronic auscultation device 100 is on or off. The multiple indicators also include an indicator that indicates the current operating mode of the electronic auscultation device 100. The multiple indicators also include an indicator that indicates whether the electronic auscultation device 100 is wirelessly connected to an external device. The multiple indicators also include an indicator that indicates 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, on the side opposite the chestpiece 110, near the chestpiece 110, which is one end in the x-axis direction. In this embodiment, "near the chestpiece 110" means that the display unit 122 is 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.

[0014] 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 123a and volume down button 123b) 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 123c for switching the operation mode of the electronic auscultation device 100. When the mode switching button 123c is pressed, the operation mode is switched as described below. That is, the mode switching button 123c accepts instructions from the user regarding the mode transition of the electronic auscultation device 100. The electronic auscultation device 100 selects one of multiple operation modes based on an instruction from the user using the mode switching button 123c and operates in that operation mode. The operation unit 123 may include a touch panel instead of multiple physical buttons. The display unit 122 and operation unit 123 may be integrated as 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's instruction using the mode switching button 123c.

[0015] Like the display unit 122, the operation unit 123 is arranged on the outer surface of the housing 121 opposite the chestpiece 110, near the chestpiece 110, at one end in the x-axis direction. With this arrangement, the user can operate the operation unit 123 (for example, with their thumb) while holding the grip unit 120 while using 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. With this arrangement, the user can maintain visibility of the display unit 122 even when operating the operation unit 123 while using the electronic auscultation device 100.

[0016] 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 does not have to include the connector 125. In this case, the electronic auscultation device 100 may have a wireless charging function or may be configured so that the battery is replaceable.

[0017] The electronic stethoscope 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.

[0018] [Chestpiece configuration of the electronic stethoscope device in the first embodiment] An example configuration of chestpiece 110 will be described with reference to Fig. 2. The upper side of Fig. 2 shows a cross-sectional view of chestpiece 110, and the lower side of Fig. 2 shows a plan view of chestpiece 110. In the plan view, only light-emitting circuit board 203, light-receiving circuit board 205, diaphragm 206, and light reflecting portion 207 are shown to clarify the positional relationship of the components.

[0019] 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 also include a circuit board on which circuit elements for controlling its operation are mounted.

[0020] 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 uses a light emitting diode (LED).

[0021] 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 phenol board or a glass epoxy board. The light emitting circuit board 203 including the light emitting element 202 functions as a light emitting unit.

[0022] 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, the number of light receiving elements 204 is one, but the present invention is not limited to this. 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)) may be configured using a plurality of light receiving elements 204.

[0023] 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.

[0024] 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.

[0025] The diaphragm 206 has a contact surface 206a that contacts the surface of a living body, which is an example of a measurement target, 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 measurement target 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 made by impregnating glass fiber with epoxy resin and then subjecting it to a thermal curing treatment. The thickness is 230 μm. The diaphragm 206 also has an integrated ring-shaped rim for fixing 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 contacts 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.

[0026] 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.

[0027] Diaphragm 206 has fixed portion 206c and is fixed to holding member 201. Fixed portion 206c is located on the outer periphery of diaphragm 206. The inner periphery of diaphragm 206 (i.e., the portion inside fixed portion 206c) is not fixed to holding member 201. Therefore, diaphragm 206 can vibrate in the z-axis direction with fixed portion 206c as a node. Specifically, when chestpiece 110 is in use, diaphragm 206 vibrates with fixed portion 206c as a node in response to displacement of the surface of the living body. In this vibration, center 206e of diaphragm 206 becomes an antinode. Diaphragm 206 functions as a vibrating part that vibrates together with the object to be measured.

[0028] 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 disposed in a position covering an area 206d of the diaphragm 206 that includes a center 206e of the circle. 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 the light from the light emitting element 202 in the area including the center 206e. Note that, although the light reflecting portion 207 is disposed in a position covering the center 206e in this embodiment, it may also be disposed in a position covering an area 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).

[0029] 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.

[0030] 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 be configured as the light reflecting portion. For example, the entire inner surface 206b of the diaphragm 206 may have a high reflectivity that can 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 reached by light emitted from the light emitting element 202, may have such a high reflectivity.

[0031] The light-emitting element 202 is disposed 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 has 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 the present 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 blocking 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.

[0032] The light receiving element 204 is positioned to receive the reflected light 212. Specifically, the light receiving element 204 is positioned at a position where the amount of received reflected light 212 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. 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.

[0033] 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 all substantially 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.

[0034] 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.

[0035] [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.

[0036] As shown in FIGS. 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 the physical movements of the person owning the biological surface 320, such as heartbeat and breathing.

[0037] 3A and 3B, the light-emitting element 202 and the light-receiving element 204 are arranged 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.

[0038] 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.

[0039] In the chestpiece 110 of FIGS. 3A to 3D, the light-shielding wall 304 in which the opening 306 is formed functions as the diaphragm section 209 on the incident light 211 side, and the light-shielding wall 305 in which the opening 307 is formed functions as the diaphragm section 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 section. 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 section 207. Furthermore, at least part of the light specularly reflected by the light-reflecting section 207 is blocked by the light-shielding wall 305, depending on the position of the light-reflecting section 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 bottom side, the side parallel to and farther from diaphragm 206 will be referred to as the top side, the side to the left as viewed from light-emitting element 202 will be referred to as the left side, and the side to the right as viewed from light-emitting element 202 will be referred to as the right side.

[0040] 3A to 3D, incident light 211 and reflected light 212 represent light fluxes that reach light receiving element 204. In Fig. 3B, part of the light emitted from light emitting element 202, light 310, 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.

[0041] 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 an 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.

[0042] Of the four line segments that form 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 line 300a. The portion of the incident light 211 that reaches the far boundary line 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 unit 207 that is the longest. The angle of incidence of the incident light 211 to the light reflecting unit 207 reaches a maximum value 303a at a position on the far boundary line 300a.

[0043] Of the four line segments that form 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 line 300b. The portion of the incident light 211 that reaches the near boundary line 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 line 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.

[0044] Of the four line segments that make up the boundary of effective range 300, the two line segments other than far boundary 300a and near boundary 300b are referred to as lateral boundary lines 300c and 300d. Lateral boundary line 300c is located on the right side of effective range 300 as seen from light-emitting element 202, and lateral boundary line 300d is located on the left side of effective range 300 as seen from light-emitting element 202.

[0045] 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.

[0046] Of the four line segments constituting the boundary of the light irradiation area 301, the line segment formed by light that has been 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 that has been 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 enables 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 form the boundary of the light-irradiated region 301, the two line segments other than the lower boundary 301a and the upper boundary 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-irradiated region 301 as viewed from the light-emitting element 202, and the lateral boundary line 301d is located on the left side of the light-irradiated region 301 as viewed 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 lengths change when the contact surface 206a is displaced, as will be described later.

[0047] 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, the 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 opening 306 defines light irradiation area 301. In this configuration, the displacement signal remains constant as the displacement of diaphragm 206 ranges from zero to a predetermined value. Thereafter, when the lower side of opening 306 no longer defines light irradiation area 301, the displacement signal begins to decrease monotonically.

[0048] 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 area 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 area 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 area 301.

[0049] 3A, the lateral boundary lines 301c and 301d of the light irradiation area 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 area 301 may be defined by the right and left sides of the opening 306.

[0050] 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 located lowest in the z-axis direction among the reflected light 212 (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 section 209 and specularly reflected by the light reflecting section 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 section 210. In the configurations of FIGS. 3A and 3B , the lower boundary 301a includes the position of the light irradiation area 301 that is 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, lower boundary line 301a includes the position in light irradiation area 301 where light reaches with the maximum reflection angle at light reflecting portion 207. This maximum reflection angle is equal to maximum incident angle 303a. Furthermore, in the configurations of FIGS. 3A and 3B, lower boundary line 301a includes the position farthest from light emitting element 202 in a plan view of diaphragm 206 in an unpressed state.

[0051] The reflected light of the near incident light 211b is referred to as upper end reflected light 212b. The upper end reflected light 212b is the light located at the uppermost position in the z-axis direction among the reflected light 212 (i.e., the portion farthest from the diaphragm 206). The upper end 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 that is 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 where the light reaches 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, upper boundary line 301b includes the position closest to light emitting element 202 in a plan view of diaphragm 206 in an unpressured state.

[0052] 3C and 3D, when the diaphragm 206 is pressed by the biological surface 320, the positions of the effective range 300, the far boundary 300a, the near boundary 300b, the light irradiation region 301, the lower boundary 301a, and the 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 side 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. This changes the area of ​​the light irradiation region 301 and the output of the light-receiving element 204, as described below.

[0053] Lower boundary line 301a is displaced by a displacement magnification 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 (within three-dimensional space, regardless of the x-axis direction) reaches light receiving element 204 is also displaced by the displacement magnification factor G. Displacement magnification 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 magnification factor G is greater than 1.5, or may be configured so that displacement magnification factor G is greater than 2.

[0054] As shown in FIGS. 3A to 3D , the upper boundary line 301b is defined by a 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 a 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 unit 207. For example, the portion of the light-shielding wall 305 that is below the reflected light 212 does not need to be provided.

[0055] [Change in the range of reflected light in the electronic auscultation device according to the first embodiment] Referring to Fig. 3E, a change in the light irradiation area 301 formed by the reflected light 212 that reaches 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.

[0056] To explain the directions, a coordinate system CS' is attached to FIG. 3E. The coordinate system CS' is a two-dimensional Cartesian coordinate system having mutually orthogonal x'-axis and y'-axis. 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 is referred to as the upper side, and the negative direction of the x'-axis is referred to as the lower side.

[0057] 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.

[0058] The area of ​​the light-irradiated region 301 is determined by a lower boundary line 301a, an upper boundary line 301b, and side boundary lines 301c and 301d. As shown in FIG. 3E, the lower boundary line 301a of the light-irradiated 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 side 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-irradiated 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 side boundary lines 301c and 301d change when the contact surface 206a is displaced.

[0059] 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 line 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.

[0060] 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, it is preferable that the width of the light receiving element 204 in the x'-axis direction be larger than the width of the light receiving element 204 in the y'-axis direction. More specifically, it is preferable that the width of the light receiving element 204 in the x'-axis direction be three or more times the width of the light receiving element 204 in the y'-axis direction.

[0061] [Relationship between the displacement amount of the living body surface 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 light receiving 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 light receiving circuit board 205.

[0062] As described above, the displacement amount of the biological surface 320 is equal to the displacement amount of the upper surface of the light reflecting portion 207. The displacement amount of the upper surface of the light reflecting portion 207 is equal to the displacement amount of the diaphragm 206. As shown in FIG. 3E, as the displacement amount of the reflected light 212 increases, the light that reaches the light receiving element 204 monotonically and linearly decreases. Therefore, if the displacement amount of the biological surface 320 is d and the value of the displacement signal is S, then S=Vmax-k×d…(Formula 1) where 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, the greater the amount of light emitted by the light-emitting element 202, the larger Vmax becomes. 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. The higher the sensitivity of the light-receiving element 204, the larger k becomes. Furthermore, the greater the amount of light emitted by the light-emitting element 202, the larger k becomes.

[0063] 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.

[0064] When displacement d exceeds dmax, reflected light 212 no longer reaches light receiving element 204, and thus displacement signal S remains zero even if displacement d increases. Therefore, chestpiece 110 is configured so that displacement d is in the range of 0 to dmax within the range in which diaphragm 206 is expected to vibrate (referred to as the operating range of diaphragm 206). As shown in graph 400, light emitting element 202 and light receiving element 204 are positioned so that the amount of light reaching light receiving element 204 (amount of received light) changes monotonically in response to movement of light reflecting portion 207 in one direction within the operating range of diaphragm 206. In the example of FIG. 4, light receiving element 204 is positioned so that the amount of received light monotonically decreases, but light receiving element 204 may also be positioned so that the amount of received light monotonically increases.

[0065] 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.

[0066] 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.

[0067] 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 about 10 Hz can also be accurately detected. Such low-frequency vibrations are included in sounds (e.g., heart sounds) generated by vibrations propagated from inside 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.

[0068] [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 being transmitted to the sound output device 520. A user such as a doctor, nurse, or public health nurse can listen to the body sound represented by the digitally converted sound signal using the sound output device 520 or the computer 530. The sound output device 520 is a wired or wireless earphone or headphone.

[0069] 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 stethoscope device 100 includes a chestpiece 110 , a grip portion 120 , and a sound output device 520 .

[0070] Next, a process for the sound output device 520 to output 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 an example has been described in which the electronic auscultation device 100 is capable of outputting a sound signal via both wireless and wired communication, the electronic auscultation device 100 may be capable of outputting a sound signal via only one of these communication methods.

[0071] 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. In addition, 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).

[0072] 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 good 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 emitted by the body due to breathing. Respiratory sounds are biological vibrations that include a frequency band (first frequency band) that includes components in a frequency range from 500 Hz to 1 kHz, for example. Heartbeat sounds are biological vibrations that include a frequency band (second frequency band) that includes components in a frequency range from 30 Hz to 300 Hz, for example.

[0073] A mode switching button 123c is provided on the operation unit 123 of the electronic auscultation device 100. When the mode switching button 123c is pressed, the auscultation mode of the electronic auscultation device 100 switches 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 "breath sound mode"). The electronic auscultation device 100 may have an auscultation mode other than the heartbeat sound mode and the breath sound 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.

[0074] 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 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.

[0075] [Characteristics of heartbeat and breathing sounds and amplification processing according to comparative examples] The properties of heartbeat sounds and respiratory 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 respiratory sounds are auscultated, the amplitude of the vibration of diaphragm 206 is amplified at the same amplification factor, and the resulting sound signal is A / D converted by A / D converter 511. The upper side of Fig. 6 shows the case where respiratory 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.

[0076] First, a case where respiratory sounds are auscultated will be described. w1 represents the peak-to-peak value of the vibration of diaphragm 206 due to respiratory sounds. Typically, w1 is approximately 1 to 5 μm. As described above, light receiving element 204 amplifies the displacement of diaphragm 206 by an amplification factor k (Equation 1 above). Therefore, the peak-to-peak value w2 of the vibration of the displacement signal due to respiratory sounds is k × w1.

[0077] Then, a high-pass filter (HPF) is applied to the displacement signal to attenuate the DC component and camera shake component contained in the displacement signal. Graph 601 shows 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 is referred to as the conversion range of the A / D converter 511.

[0078] After the HPF is applied, the respiratory sound signal is amplified by 300 times by the amplifier circuit. Graph 602 shows the amplified respiratory sound signal. In the example of graph 602, the respiratory sound signal falls within the conversion range of the A / D converter 511.

[0079] Next, we will explain the case where heartbeat sound is auscultated. 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.

[0080] Then, 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 603 represents the displacement signal, i.e., the heartbeat sound signal, after the HPF is applied.

[0081] 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.

[0082] 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 Fig. 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 auscultated properly. 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 becomes smaller, resulting in a lower S / N ratio.

[0083] Therefore, in this embodiment, the electronic auscultation device 100 sets, for each operation mode, the amount of variation 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 variation 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 variation 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.

[0084] 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 amplitudes of the breath sound vibrations and the heartbeat sound vibrations 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.

[0085] 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 invention. 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, 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.

[0086] [Setting of fluctuation amount due to sensitivity of light receiving element in the first embodiment] A method for changing the amount of fluctuation in the output value of the sound signal per unit vibration amount of diaphragm 206 will be described with reference to Fig. 7. In the example of Fig. 7, the amount of fluctuation in the output value of the sound signal per unit vibration amount of diaphragm 206 is changed by setting the amplification factor of 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.

[0087] 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.

[0088] First, the settings in the breath sound mode will be described. w1 is the same as in the description of Figure 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 the breath sound is k1 × w1.

[0089] An HPF is applied to the displacement signal, and the DC component and the tremor component included in the displacement signal are attenuated. Graph 701 represents the displacement signal after the HPF is applied, that is, the breath sound signal.

[0090] The breath sound signal after the HPF is applied is amplified 300 times by an amplifier circuit. Graph 702 represents the amplified breath sound signal. In the example of Graph 702, the breath sound signal is within the conversion range of the A / D converter 511.

[0091] Next, the settings in the heart sound mode will be described. w3 is the same as in the description of FIG. 6. In the heart sound mode, it is assumed that the light receiving element 204 amplifies the displacement of the diaphragm 206 with an amplification factor k2 (k2 < k1). Therefore, the peak-to-peak value w6 of the vibration of the displacement signal due to the heart sound is k2 × w3.

[0092] An HPF is applied to the displacement signal, and the DC component and the tremor component included in the displacement signal are attenuated. Graph 703 represents the displacement signal after the HPF is applied, that is, the heart sound signal.

[0093] The heart sound signal after the HPF is applied is amplified 300 times by an amplifier circuit. Graph 704 represents the amplified heart sound signal. In the example of Graph 702, the heart sound signal is within the conversion range of the A / D converter 511.

[0094] As described above, in the present 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, where it is A / D converted into a digital signal. On the other hand, when the heart sound mode is selected, the displacement signal generated at an amplification factor (k2) lower than this specific amplification factor is further amplified by the amplifier circuit and supplied to the A / D converter 511, where it is A / D converted into a digital signal. Thereby, in either the breath sound mode or the heart sound mode, the sound signal can be appropriately converted into a digital signal.

[0095] [Circuit Configuration of the Electronic Stethoscope in the 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 of Fig. 8A is a diagram showing in more detail the hardware configuration of Fig. 6.

[0096] 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. That is, 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.

[0097] 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.

[0098] 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 (registered trademark) 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 the stored contents even without external power. The Bluetooth circuit 803 is a control unit that controls the wireless communication unit 514 that complies with the Bluetooth wireless communication standard. The wireless communication unit 514 includes an antenna for wireless communication. Although the microcontroller 800 includes the Bluetooth circuit 803 in FIG. 8A, the Bluetooth circuit 803 may be external to the microcontroller 800. The RAM 804 is a storage means for temporarily storing programs and various setting data read from the nonvolatile memory 802. The microcontroller 800 is realized by a plurality of circuit elements mounted on a circuit board included in the grip unit 120. The microcontroller 800 transmits a sound signal based on the 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 biological 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 to Pulse Code Modulation (PCM) format. The wireless communication unit 514, which complies with a wireless communication standard such as Bluetooth (registered trademark), 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).

[0099] 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 UART. 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.

[0100] 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.

[0101] 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.

[0102] 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 and is 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, the 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.

[0103] 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.

[0104] 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, when the light emitting element 202 is a laser diode that emits laser light as described above, 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.

[0105] The signal processing unit 830 includes a signal path between the light receiving element 204 and the microcontroller 800, in which a buffer circuit 831, an HPF 832, and amplifier circuits 833 and 834 (fourth amplifier circuits) with low-pass filters are arranged. 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.

[0106] 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.

[0107] 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).

[0108] 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 shaking of the user's hand while holding the electronic stethoscope 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, the biological components can be appropriately acquired within the dynamic range of the amplifier circuit. Note that the HPF 832 may be replaced by a bandpass filter that removes components below a value in the range of 10 Hz to 100 Hz (e.g., 10 Hz).

[0109] 8A, a buffer circuit 831 is placed 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.

[0110] The amplifier circuit 833 amplifies the signal received from the HPF 832, attenuates high-frequency component signals, and passes low-frequency component signals. 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.

[0111] The amplifier circuit 834 amplifies the signal received from the amplifier circuit 834, attenuates high-frequency components of the signal, and outputs the signal with low-frequency components passed 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.

[0112] 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, signal processing unit 830 may include only one amplifier circuit with a low-pass filter, and this amplifier circuit 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.

[0113] 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.

[0114] 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.

[0115] 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 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 be output from a node on the signal path between the light receiving element 204 and the buffer circuit 831.

[0116] 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.

[0117] 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.

[0118] Current control circuit 860 controls the current flowing through light-emitting element 202. Current control circuit 860 has a control terminal 861. When a high-level signal is supplied to control terminal 861, current flows through light-emitting element 202, and when a low-level signal is supplied to control terminal 861, current does not flow through light-emitting element 202. In FIG. 8A , current control circuit 860 is included in grip portion 120, but at least some of the circuit elements of current control circuit 860 may be included in chestpiece 110.

[0119] 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.

[0120] 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 duty ratio lower than the specific duty ratio.

[0121] [Modification of the circuit configuration of the electronic auscultation device in the first embodiment] A modified example 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. Fig. 8A and Fig. 8B differ in the configuration of the current control circuit 860.

[0122] 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 is turned on, and when a low-level signal is supplied to the control terminal 861, the transistor 862 is turned 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 higher when the control signal is off than when it is on.

[0123] 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.

[0124] 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) 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.

[0125] According to the above embodiment, the amplitude of vibration of the diaphragm 206 can be amplified by an appropriate amplification factor in both the breath sound mode and the heartbeat sound mode.

[0126] <Second embodiment> [Circuit configuration of the electronic auscultation device in the second embodiment] An example of the configuration of an electronic auscultation device 100 according to the second embodiment will be described with reference to Figures 9A and 9B. Differences from the first embodiment will be mainly described below. 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.

[0127] 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.

[0128] 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 represented 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.

[0129] 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.

[0130] 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).

[0131] 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 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.

[0132] [Modification of the circuit configuration of the electronic auscultation device in the second embodiment] A modified example of the circuit configuration of the electronic auscultation device 100 in the second embodiment will be described with reference to Figure 9B. Differences from Figure 9A will be described below. Figures 9A and 9B differ in the configuration of the voltage control circuit 870. Also, the power supply unit 810 in Figure 9B does not include a voltage regulator 817.

[0133] 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.

[0134] 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.

[0135] 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 an amount of light emission (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.

[0136] According to the above embodiment, the amplitude of vibration of the diaphragm 206 can be amplified by an appropriate amplification factor in both the breath sound mode and the heartbeat sound mode.

[0137] <Modifications of the above embodiment> 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, it 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.

[0138] In the above-described embodiment, chestpiece 110 includes only one light-emitting element 202. Alternatively, chestpiece 110 may include multiple light-emitting elements 202. Light emitted by the multiple light-emitting elements 202 may be reflected by light reflecting portion 207 and reach light-receiving element 204. Light-receiving element 204 may detect the displacement of diaphragm 206 based on the total amount of light received by the multiple light-receiving elements 204. 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 light reflecting portion 207. The displacement of diaphragm 206 may be detected based on the total amount of light received by the multiple light-receiving elements 204.

[0139] 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 may not 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.

[0140] 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.

[0141] 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.

[0142] 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.

[0143] 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.

[0144] <Other embodiments> The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program.The present invention can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0145] <Summary of the embodiment> (Item 1) a diaphragm that comes into contact with a living body and vibrates together with the living body, the diaphragm having a light reflecting portion provided on a surface of the diaphragm opposite to a contact surface that comes into contact with the living body; A light source and 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 that generates a signal according to the amount of light that reaches the light-receiving surface; A selection means for selecting one of a plurality of modes including a first mode for measuring biological vibrations including a first frequency band and a second mode for measuring biological vibrations including a second frequency band lower than the first frequency band; an output means for outputting a digital signal based on the signal generated by the light receiving element to an external device; a light emission amount adjusting means for adjusting the light emission amount of the light source; Equipped with The light emission amount adjusting means When the first mode is selected by the selection means, adjusting the light emission amount of the light source to a first light emission amount; When the second mode is selected by the selection means, the light emission amount of the light source is adjusted to a second light emission amount that is smaller than the first light emission amount. An electronic stethoscope device. (Item 2) The electronic auscultation device further comprises a current control circuit for controlling a current flowing through the light source; The light emission amount adjusting means adjusts the light emission amount of the light source by changing the duty ratio of a pulse width modulation signal supplied to the current control circuit. 2. The electronic auscultation device according to item 1. (Item 3) 2. The electronic auscultation device according to item 1, wherein the light emission intensity adjusting means adjusts the light emission intensity of the light source by changing the resistance value of a current path passing through the light source. (Item 4) The electronic auscultation device further includes a sensitivity adjusting means for adjusting the sensitivity of the light receiving element, The sensitivity adjustment means When the first mode is selected by the selection means, the sensitivity of the light receiving element is adjusted to a first sensitivity; When the second mode is selected by the selection means, the sensitivity of the light receiving element is adjusted to a second sensitivity lower than the first sensitivity. 4. The electronic auscultation device according to any one of items 1 to 3, (Item 5) the first frequency band components include components in a frequency band ranging from 500 Hz to 1 kHz; the second frequency band components include components in a frequency band ranging from 30 Hz to 300 Hz; 5. The electronic auscultation device according to any one of items 1 to 4, characterized in that: (Item 6) the first mode is a mode for measuring breath sounds, The second mode is a mode for measuring heartbeat sounds. 6. The electronic auscultation device according to any one of items 1 to 5, (Item 7) the light source includes a light emitting diode; The electronic stethoscope device further includes an aperture unit that narrows the light emitted from the light-emitting diode, the light receiving surface is disposed so as to receive light that has passed through the diaphragm portion and has been specularly reflected by the light reflecting portion, The signal generated by the light receiving element is a signal corresponding to the area of ​​the light irradiation region formed by the specularly reflected light that reaches the light receiving surface. 7. The electronic auscultation device according to any one of items 1 to 6, (Item 8) 8. The electronic auscultation device according to any one of items 1 to 7, wherein the selection means selects one of the plurality of modes based on an instruction from a user.

[0146] The invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0147] 100 Electronic stethoscope device, 110 Chest piece, 120 Grip, 202 Light-emitting element, 204 Light-receiving element, 206 Diaphragm

Claims

1. a diaphragm that comes into contact with a living body and vibrates together with the living body, the diaphragm having a light reflecting portion provided on a surface of the diaphragm opposite to a contact surface that comes into contact with the living body; A light source and 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 that generates a signal according to the amount of light that reaches the light-receiving surface; a selection means for selecting one of a plurality of modes including a first mode for measuring biological vibrations including a first frequency band and a second mode for measuring biological vibrations including a second frequency band lower than the first frequency band; an output means for outputting a digital signal based on the signal generated by the light receiving element to an external device; a light emission amount adjusting means for adjusting the light emission amount of the light source; Equipped with The light emission amount adjusting means When the first mode is selected by the selection means, adjusting the light emission amount of the light source to a first light emission amount; When the second mode is selected by the selection means, the light emission amount of the light source is adjusted to a second light emission amount that is smaller than the first light emission amount. An electronic stethoscope device.

2. The electronic auscultation device further comprises a current control circuit for controlling a current flowing through the light source; The light emission amount adjusting means adjusts the light emission amount of the light source by changing the duty ratio of a pulse width modulation signal supplied to the current control circuit.

2. The electronic auscultation device according to claim 1.

3. 2. 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 a resistance value of a current path passing through said light source.

4. The electronic auscultation device further includes a sensitivity adjusting means for adjusting the sensitivity of the light receiving element, The sensitivity adjustment means When the first mode is selected by the selection means, the sensitivity of the light receiving element is adjusted to a first sensitivity; When the second mode is selected by the selection means, the sensitivity of the light receiving element is adjusted to a second sensitivity lower than the first sensitivity.

2. The electronic auscultation device according to claim 1.

5. the first frequency band components include components in a frequency band ranging from 500 Hz to 1 kHz; the second frequency band components include components in a frequency band ranging from 30 Hz to 300 Hz; 2. The electronic auscultation device according to claim 1.

6. the first mode is a mode for measuring breath sounds, the second mode is a mode for measuring heartbeat sounds; 2. The electronic auscultation device according to claim 1.

7. the light source includes a light emitting diode; The electronic stethoscope device further includes an aperture unit that narrows the light emitted from the light-emitting diode, the light receiving surface is disposed so as to receive light that has passed through the diaphragm portion and has been specularly reflected by the light reflecting portion, The signal generated by the light receiving element is a signal corresponding to the area of ​​the light irradiation region formed by the specularly reflected light that reaches the light receiving surface.

2. The electronic auscultation device according to claim 1.

8. 2. The electronic auscultation device according to claim 1, wherein the selection means selects one of the plurality of modes based on an instruction from a user.

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