Photoacoustic devices and systems including one or more light guide assemblies

Abstract

An apparatus may include a platen, a light source system, and a receiver system. The light source system may include at least a first light emitting component and at least a first light guide component. The first light guide assembly may be configured to transmit light from the first light emitting assembly to a target object in contact with the first region of the platen. A receiver system may include at least two receiver stack portions. The first receiver stack portion may be located proximate a first side of the first portion of the first light guide assembly, and the second receiver stack portion may be located proximate a second side of the first portion of the first light guide assembly. The receiver system may be configured to detect an acoustic wave corresponding to a photoacoustic response of a target object to light emitted by the light source system.

Description

[0001] This application claims priority to U.S. Patent Application No. 18 / 069,901, filed on December 21, 2022, entitled "PHOTOACOUSTIC DEVICES AND SYSTEMS INCLUDING ONE OR MORE LIGHT GUIDE COMPONENTS", which is hereby incorporated by reference in its entirety for all purposes.

[0002] Cross - reference to related applications

[0003] This application relates to U.S. Patent Application No. 18 / 069,859 (Attorney Docket No. 2205776 / QUALP579US), entitled "PHOTOACOUSTIC DEVICES AND SYSTEMS"; U.S. Patent Application No. 18 / 069,877 (Attorney Docket No. 2205722U1 / QUALP580AUS), entitled "SEMI - COMPACT PHOTOACOUSTIC DEVICES AND SYSTEMS"; U.S. Patent Application No. 18 / 069,882 (Attorney Docket No. 2205722U2 / QUALP580BUS), entitled "SEMI - COMPACT PHOTOACOUSTIC DEVICES AND SYSTEMS"; U.S. Patent Application No. 18 / 069,885 (Attorney Docket No. 2205722U3 / QUALP580CUS), entitled "SEMI - COMPACT PHOTOACOUSTIC DEVICES AND SYSTEMS"; U.S. Patent Application No. 18 / 069,888 (Attorney Docket No. 2205722U4 / QUALP580DUS), entitled "SEMI - COMPACT PHOTOACOUSTIC DEVICES AND SYSTEMS"; and U.S. Patent Application No. 18 / 069,893 (Attorney Docket No. 2205722U5 / QUALP580EUS), entitled "SEMI - COMPACT PHOTOACOUSTIC DEVICES AND SYSTEMS", each of which is hereby incorporated by reference in its entirety for all purposes. Technical field

[0004] This disclosure generally relates to photoacoustic devices and systems. Background Art

[0005] A variety of different sensing technologies and algorithms are being implemented in devices for various biometric and biomedical applications, including hygiene and health monitoring. This drive is due in part to the availability limitations of traditional measurement devices for continuous, non-invasive, and mobile monitoring. Some such devices are, or include, photoacoustic devices. Although some previously deployed photoacoustic devices and systems can provide acceptable results, improved photoacoustic devices and systems would be desirable. Summary of the Invention

[0006] The systems, methods, and devices of the present disclosure each have several aspects, none of which alone is responsible for the desired attributes disclosed herein.

[0007] An innovative aspect of the subject matter described in the present disclosure can be implemented in a device. The device can include a pressing plate, a light source system, and a receiver system. The receiver system can be, or can include, an ultrasonic receiver system. In some embodiments, a mobile device (such as a wearable device, a cellular phone, etc.) can be, or can include, at least a part of the device.

[0008] In some examples, the light source system can be configured to emit light through a first region of the pressing plate to a target object in contact with the first region of the pressing plate. According to some examples, the light source system can include at least a first light-emitting component and at least a first light guiding component. In some examples, the first light guiding component can be configured to send the light from the first light-emitting component to the first region of the pressing plate. In some examples, at least the first region of the pressing plate can be transparent. In some examples, the first light guiding component can include at least one optical fiber.

[0009] According to some examples, the receiver system can include at least two receiver stack portions. In some such examples, the first receiver stack portion can be located near a first side of a first portion of the first light guiding component, and the second receiver stack portion can be located near a second side of the first portion of the first light guiding component. In some examples, the receiver system can be configured to detect sound waves corresponding to the photoacoustic response of the target object to the light emitted by the light source system. In some examples, the first receiver stack portion can be located near a second region on a first side of the pressing plate in the first region, and the second receiver stack portion can be located near a third region on a second opposite side of the pressing plate in the first region.

[0010] In some examples, the first receiver stack portion and the second receiver stack portion can be parts of a first receiver stack ring. According to some examples, the first receiver stack ring can be configured to surround a first portion of the first light guide assembly. In some examples, the annular region of the platen near the first receiver stack ring can be configured to surround a first region of the platen. In some examples, the device can further include a second receiver stack ring. According to some such examples, the second receiver stack ring can be configured to surround the first receiver stack ring. In some examples, the light source system can include at least a second light guide assembly. In some such examples, the second light guide assembly can be configured to send light from the first light emitting assembly to a second region of the platen. In some examples, the second receiver stack ring can surround the second region of the platen.

[0011] In some examples, the light source system can include at least a second light emitting assembly and at least a second light guide assembly. According to some such examples, the second light guide assembly can be configured to send light from the second light emitting assembly to at least a portion of the first light guide assembly.

[0012] According to some examples, the receiver system can include a linear array of receiver stack portions. In some examples, the receiver system can include a two-dimensional array of receiver stack portions.

[0013] In some examples, the first receiver stack portion can be located between a first portion of the first light emitting assembly and the platen, and the second receiver stack portion can be located between a second portion of the first light emitting assembly and the platen.

[0014] According to some examples, at least one of the first receiver stack portion or the second receiver stack portion can be located between a second portion of the first light guide assembly and the platen. According to some such examples, the device can further include at least one electromagnetic shielding layer located between the first light emitting assembly and the receiver system.

[0015] In some examples, the light source system can include at least a first optical coupling component configured to couple light from the first light emitting assembly to the first light guide assembly.

[0016] According to some examples, the first light emitting assembly can be configured to emit laser pulses. According to some such examples, the laser pulses can be in a wavelength range of 500 nm to 1000 nm. In some examples, the first light emitting assembly can be configured to emit laser pulses with a pulse width in a range from 3 nanoseconds to 1000 nanoseconds.

[0017] In some examples, the combined thickness of the platen and the receiver stack portion can be in a range from 2 mm to 8 mm.

[0018] According to some examples, the device may further include a mirror system, which may include a first mirror portion located between the pressing plate and the first receiver stack portion and a second mirror portion located between the pressing plate and the second receiver stack portion.

[0019] In some embodiments, the device may include a control system. The control system may include one or more general single-chip or multi-chip processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs) or other programmable logic devices, discrete gate or transistor logic, discrete hardware components, or combinations thereof.

[0020] In some examples, the control system may be configured to control the light source system. In some examples, the control system may also be configured to receive a signal corresponding to an acoustic wave from the receiver system. According to some examples, the control system may also be configured to estimate one or more cardiac characteristics based at least in part on the signal.

[0021] Other innovative aspects of the subject matter described in this disclosure may be implemented in a method. In some examples, the method may involve causing a light source system to emit light through a first region of a pressing plate toward a target object in contact with the first region of the pressing plate. According to some examples, the light source system may include at least a first light emitting component and at least a first light guiding component. In some examples, the first light guiding component may be configured to send light from the first light emitting component to the first region of the pressing plate.

[0022] According to some examples, the method may involve receiving, from a receiver system, a signal corresponding to an acoustic wave caused by a photoacoustic response of the target object to the light emitted by the light source system. In some examples, the receiver system may include at least two receiver stack portions, a first receiver stack portion being located near a first side of a first portion of the first light guiding component, and a second receiver stack portion being located near a second side of the first portion of the first light guiding component. According to some examples, causing the light source system to emit light may involve causing the light source system to emit laser pulses.

[0023] Some or all of the methods described herein may be performed by one or more devices according to instructions (e.g., software) stored on a non-transitory medium. Such a non-transitory medium may include memory devices such as those described herein, including but not limited to random access memory (RAM) devices, read only memory (ROM) devices, etc. Thus, some innovative aspects of the subject matter described in this disclosure may be implemented in one or more non-transitory media having software stored thereon. The software may include instructions for controlling one or more devices to perform one or more of the disclosed methods.

[0024] In some examples, the method may involve causing a light source system to emit light through a first region of a platen toward a target object in contact with the first region of the platen. According to some examples, the light source system may include at least a first light-emitting component and at least a first light guide component. In some examples, the first light guide component may be configured to send light from the first light-emitting component to the first region of the platen.

[0025] According to some examples, the method may involve receiving, from a receiver system, a signal corresponding to sound waves caused by a photoacoustic response of a target object to light emitted by the light source system. In some examples, the receiver system may include at least two receiver stack portions, a first receiver stack portion being located near a first side of a first portion of the first light guide component, and a second receiver stack portion being located near a second side of the first portion of the first light guide component. According to some examples, causing the light source system to emit light may involve causing the light source system to emit laser pulses.

[0026] Details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims. Note that the relative dimensions in the figures below may not be drawn to scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a block diagram showing example components of a device according to some disclosed implementations.

[0028] Figure 2 shows example components of a device according to some disclosed implementations.

[0029] Figure 3A 、 Figure 3B and Figure 3C show Figure 2 different examples of how some of the components of the device shown in

[0030] Figure 3D show Figure 2 examples of components of the device shown in

[0031] Figure 4 show example components of a device according to some alternative implementations.

[0032] Figure 5 show example components of a device according to some alternative implementations.

[0033] Figure 6 show example components of a device according to some alternative implementations.

[0034] Figure 7Illustrates example components of a device according to some alternative embodiments.

[0035] Figure 8 Illustrates example components of a device according to some alternative embodiments.

[0036] Figure 9 Illustrates example components of a device according to some alternative embodiments.

[0037] Figure 10 Illustrates example components of a device according to some alternative embodiments.

[0038] Figure 11 Is a flowchart illustrating examples of some disclosed operations.

[0039] Figure 12 Illustrates according to Figure 11 Examples of heart rate waveform (HRW) features that can be extracted according to some embodiments of a method.

[0040] Figure 13 Illustrates examples of devices that can be used in a system for estimating blood pressure based at least in part on pulse transit time (PTT).

[0041] Figure 14 Shows a cross-sectional side view of a graphical representation of a portion of an artery through which a pulse propagates.

[0042] Figure 15A Illustrates an example flow monitoring device designed to be worn around the wrist according to some embodiments.

[0043] Figure 15B Illustrates an example flow monitoring device 1500 designed to be worn on a finger according to some embodiments.

[0044] Figure 15C Illustrates an example flow monitoring device 1500 designed to be located on an earbud according to some embodiments.

[0045] Like reference numerals and names in different figures indicate like elements. Detailed Description

[0046] For purposes of describing various aspects of the present disclosure, the following description is directed to certain embodiments. However, those of ordinary skill in the art will readily recognize that the teachings herein can be applied in many different ways. Some of the concepts and examples provided in the present disclosure are particularly applicable to blood pressure monitoring applications. However, some embodiments can also be applicable to other types of biosensing applications, as well as other fluid flow systems. The described embodiments can be implemented in any device, apparatus, or system that includes the devices disclosed herein. Additionally, it is contemplated that the described embodiments can be included in or associated with various electronic devices, such as but not limited to: mobile phones, cellular phones supporting multimedia Internet, mobile TV receivers, wireless devices, smart phones, smart cards, wearable devices (such as bracelets, armbands, wristbands, rings, headbands, patches, etc.), Bluetooth® devices, personal data assistants (PDAs), wireless email receivers, handheld or portable computers, netbooks, notebooks, smartbooks, tablet computers, printers, copiers, scanners, fax devices, global positioning system (GPS) receivers / navigators, cameras, digital media players, gaming consoles, watches, clocks, calculators, television monitors, flat panel displays, electronic reading devices (e.g., e-readers), mobile health devices, computer monitors, automotive displays (including odometer and speedometer displays, etc.), cockpit controls and / or displays, camera view displays (such as the display of a rearview camera in a vehicle), building structures, microwave ovens, refrigerators, stereo systems, cassette recorders or players, DVD players, CD players, VCRs, radios, portable memory chips, washing machines, dryers, washer / dryers, parking meters, vehicle doors, autonomous or semi-autonomous vehicles, drones, Internet of Things (IoT) devices, etc. Thus, the teachings are not intended to be limited to the specific embodiments depicted and described with reference to the accompanying drawings; rather, the teachings have broad applicability, which will be apparent to those of ordinary skill in the art.

[0047] Non-invasive health monitoring devices, such as those based on photoacoustic plethysmography (PAPG), have various potential advantages over invasive health monitoring devices, such as those based on cuff or catheter-based blood pressure measurement devices. However, it has proven difficult to design a satisfactory compact or semi-compact PAPG-based device. (The length of some "semi-compact" devices can be in the range of 5.0 mm to 40 mm. The cross-sectional area of some semi-compact devices can be in the range of 6.0 mm 2 to 50 mm 2within the range. A "compact" device is smaller than a semi-compact device.) For example, some semi-compact devices recently developed by the present assignee for reducing spurious signals such as electromagnetic interference (EMI) signals, signals from reflected light, and signals from reflected sound waves may be too large to be conveniently deployed in wearable devices such as watches, patches, or earbuds.

[0048] Some disclosed devices include a platen, a light source system, and a receiver system. The receiver system can be or can include an ultrasonic receiver system. According to some embodiments, the light source system can be configured to emit light through a first region of the platen to a target object in contact with the first region of the platen. In some embodiments, the light source system can include at least a first light-emitting component and at least a first light guide component. In some such embodiments, the first light guide component can be configured to send light from the first light-emitting component to the first region of the platen. According to some embodiments, the receiver system can include at least two receiver stack portions: a first receiver stack portion can be located near a first side of a first portion of the first light guide component, and a second receiver stack portion can be located near a second side of the first portion of the first light guide component. In some examples, the first receiver stack portion and the second receiver stack portion can be parts of a receiver stack ring. The receiver system can be configured to detect sound waves corresponding to the photoacoustic response of the target object to the light emitted by the light source system. In some embodiments, the device can include an anti-reflection layer, a mirror layer, or a combination thereof. As used herein, "anti-reflection" refers to the property of light. Thus, an anti-reflection layer is a layer configured to reduce light reflection.

[0049] Specific embodiments of the subject matter described in this disclosure can be implemented to achieve one or more of the following potential advantages. Various disclosed configurations include devices with PAPG functionality that are compact enough to be located in wearable devices. Configurations in which the receiver stack portions are located on the side of or around a central light source can enhance the sensitivity of the device to received photoacoustic waves, such as arterial photoacoustic waves. According to some embodiments, the receiver system can be shielded from electromagnetic interference (EMI) caused by the circuitry of the light source system, from the light emitted by the light source system, from the light reflected by the platen, or a combination thereof. In some such embodiments, the light source system circuitry and the light-emitting part(s) can be laterally offset from the receiver system, which can result in even less EMI reaching the receiver system. In some examples, an acoustic impedance matching layer can mitigate unwanted reflections of sound waves, thereby reducing another type of noise.

[0050] Figure 1A block diagram showing example components of a device according to some disclosed embodiments. In this example, device 100 includes a platen 101, a receiver system 102, and a light source system 104. Some embodiments of device 100 may include a control system 106, an interface system 108, a noise reduction system 110, or a combination thereof.

[0051] Various examples of the platen 101 and various configurations of the light source system 104 and the receiver system 102 are disclosed herein. Some examples are described in more detail below. The platen 101 may be made of any suitable material, such as glass, acrylic, polycarbonate, etc.

[0052] According to some examples, the platen 101 (or another part of the device) may include one or more anti-reflection layers. In some examples, one or more anti-reflection layers may be located on or near one or more outer surfaces of the platen 101.

[0053] In some examples, at least a portion of the outer surface of the platen 101 may have an acoustic impedance configured to approximate the acoustic impedance of human skin. A portion of the outer surface of the platen 101 may be (for example) configured to receive a portion of a target object, such as a human finger. (As used herein, the terms "finger" and "digit" may be used interchangeably, for example, the thumb is an example of a finger.) The typical range of the acoustic impedance of human skin is 1.53 - 1.680 MRayls. In some examples, at least the outer surface of the platen 101 may have an acoustic impedance in the range of 1.4 - 1.8 MRayls or in the range of 1.5 - 1.7 MRayls. Alternatively or additionally, in some examples, at least the outer surface of the platen 101 may be configured to conform to the surface of human skin. In some such examples, at least the outer surface of the platen 101 may have a material property similar to putty or chewing gum.

[0054] In some examples, at least a portion of the platen 101 may have an acoustic impedance configured to approximate the acoustic impedance of one or more receiver elements of the receiver system 102. According to some examples, the layer located between the platen 101 and one or more receiver elements may have an acoustic impedance configured to approximate the acoustic impedance of one or more receiver elements. Alternatively or additionally, in some examples, the layer located between the platen 101 and one or more receiver elements may have an acoustic impedance within the acoustic impedance range between the acoustic impedance of the platen and the acoustic impedance of one or more receiver elements.

[0055] In some examples, the light source system 104 may be configured to emit light through a first region of the platen 101 to a target object in contact with the first region of the platen 101. According to some examples, the light source system 104 may include at least a first light emitting component and at least a first light guiding component. In some examples, the light guiding component may include one or more optical fibers. The first light guiding component may be configured to send light from the first light emitting component to the first region of the platen.

[0056] According to some examples, the receiver system 102 may include at least two receiver stack portions: a first receiver stack portion may be located near a first side of a first portion of the first light guiding component, and a second receiver stack portion may be located near a second side of the first portion of the first light guiding component. In some examples, the first receiver stack portion and the second receiver stack portion may be parts of a first receiver stack ring. The receiver stack ring may be configured to surround the first portion of the first light guiding component. In some examples, the receiver system 102 may be configured to detect sound waves corresponding to a photoacoustic response of the target object to light emitted by the light source system.

[0057] Various examples of the receiver system 102 are disclosed herein, some of which may include an ultrasonic receiver system, an optical receiver system, or a combination thereof. In some embodiments where the receiver system 102 is or includes an ultrasonic receiver system, an ultrasonic receiver and an ultrasonic transmitter may be combined in an ultrasonic transceiver. In some examples, the receiver system 102 may include a piezoelectric receiver layer, such as a layer of polyvinylidene fluoride (PVDF) polymer, polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) copolymer, piezoelectric composite, etc. In some embodiments, a single piezoelectric layer may be used as an ultrasonic receiver. In some embodiments, other piezoelectric materials may be used in the piezoelectric layer, such as aluminum nitride (AlN) or lead zirconate titanate (PZT). In some examples, the receiver system 102 may include an array of ultrasonic transducer elements, such as an array of piezoelectric micromachined ultrasonic transducers (PMUTs), an array of capacitive micromachined ultrasonic transducers (CMUTs), etc. In some such examples, the piezoelectric receiver layer, the PMUT elements in a single-layer array of PMUTs, or the CMUT elements in a single-layer array of CMUTs may be used as both an ultrasonic transmitter and an ultrasonic receiver. According to some examples, the receiver system 102 may be or may include an ultrasonic receiver array. In some examples, the device 100 may include one or more separate ultrasonic transmitter elements. In some such examples, the ultrasonic transmitter may include an ultrasonic plane wave generator.

[0058] In some examples, the light source system 104 may include one or more light emitting diodes. In some embodiments, the light source system 104 may include one or more laser diodes. According to some embodiments, the light source system 104 may include one or more vertical cavity surface emitting lasers (VCSELs). In some embodiments, the light source system 104 may include one or more edge emitting lasers. In some embodiments, the light source system may include one or more neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers.

[0059] In some examples, the light source system 104 may be configured to emit laser pulses in a wavelength range of 500 nm to 1000 nm. In some examples, the light source system 104 may be configured to send light in one or more wavelength ranges. In some examples, the light source system 104 may be configured to send light in a wavelength range of 500 to 600 nanometers (nm). According to some examples, the light source system 104 may be configured to send light in a wavelength range of 800 to 950 nm. One or both of these wavelength ranges may be suitable for various usage scenarios, considering factors such as skin reflectance, energy density, absorption coefficients of blood and various tissues, and skin safety limits. For example, both the wavelength range of 500 nm to 600 nm and the wavelength range of 800 nm to 950 nm may be suitable for obtaining photoacoustic responses from relatively small, shallow blood vessels (such as blood vessels with a diameter of about 0.5 mm and a depth in the range of 0.5 mm to 1.5 mm, such as blood vessels that can be found in a finger). For example, the wavelength range of 800 to 950 nm may be suitable for obtaining photoacoustic responses from relatively large, deep blood vessels (such as blood vessels with a diameter of about 2.0 mm and a depth in the range of 2 mm to 3 mm, such as blood vessels that can be found in an adult wrist).

[0060] Depending on the specific embodiment, the light source system 104 may include various types of drive circuits. In some disclosed embodiments, the light source system 104 may include at least one multi-junction laser diode, which may generate less noise than a single-junction laser diode. In some examples, the light source system 104 may include a drive circuit (also referred to herein as a drive circuit system) that is configured to cause the light source system to emit light pulses with a pulse width in the range of 3 nanoseconds to 1000 nanoseconds. According to some examples, the light source system 104 may include a drive circuit that is configured to cause the light source system to emit light pulses with a pulse repetition frequency in the range of 1 kilohertz to 100 kilohertz.

[0061] In some embodiments, the device (e.g., the receiver system 102, the light source system 104, or both) may include one or more sound-absorbing layers, sound-insulating materials, light-absorbing materials, light-reflecting materials, or combinations thereof. In some examples, the sound-insulating materials may be located between at least a portion of the light source system 104 and the receiver system 102. In some examples, the device (e.g., the receiver system 102, the light source system 104, or both) may include one or more electromagnetic shielding transmission lines. In some such examples, the one or more electromagnetic shielding transmission lines may be configured to reduce electromagnetic interference received by the receiver system 102 from the light source system 104.

[0062] In some embodiments, the light source system 104 may be configured to emit light of various wavelengths, which may be selected to trigger acoustic wave emission primarily from a specific type of material. For example, because hemoglobin in blood strongly absorbs near-infrared light, in some embodiments, the light source system 104 may be configured to emit one or more wavelengths of light in the near-infrared range to trigger acoustic wave emission from hemoglobin. However, in some examples, the control system 106 may control the (one or more) wavelengths of the light emitted by the light source system 104 to preferentially induce acoustic waves in blood vessels, other soft tissues, and / or bones. For example, an infrared (IR) light-emitting diode (LED) may be selected and short pulses of IR light may be emitted to irradiate a portion of a target object and generate acoustic wave emission that is then detected by the receiver system 102. In another example, an IR LED and a red LED or other colors, such as green, blue, white, or ultraviolet (UV), may be selected and short pulses of light may be emitted sequentially from each light source, and an ultrasound image may be obtained after light is emitted from each light source. In other embodiments, one or more light sources of different wavelengths may be excited sequentially or simultaneously to generate acoustic emissions that can be detected by an ultrasound receiver. Image data obtained using light sources of different wavelengths and at different depths (e.g., varying RGD) into the target object from the ultrasound receiver may be combined to determine the location and type of materials in the target object. Image contrast may occur when materials in the body generally absorb different wavelengths of light differently. When materials in the body absorb a specific wavelength of light, they may differentially heat up and generate acoustic wave emission with a light pulse that has a short enough duration and sufficient intensity. Depth contrast may be obtained with light of different wavelengths and / or intensities for each selected wavelength. That is, sequential images may be obtained with varying light intensities and wavelengths at a fixed RGD (which may correspond to a fixed depth into the target object) to detect materials and their locations within the target object. For example, hemoglobin, blood glucose, or blood oxygen in blood vessels within a target object such as a finger may be photoacoustically detected.

[0063] According to some embodiments, the light source system 104 can be configured to emit light pulses having a pulse width less than about 100 nanoseconds. In some embodiments, the light pulses can have a pulse width between about 10 nanoseconds and about 500 nanoseconds or greater. According to some examples, the light source system can be configured to emit a plurality of light pulses at a pulse repetition frequency between 10 Hz and 100 kHz. Alternatively or additionally, in some embodiments, the light source system 104 can be configured to emit a plurality of light pulses at a pulse repetition frequency between about 1 MHz and about 100 MHz. Alternatively or additionally, in some embodiments, the light source system 104 can be configured to emit a plurality of light pulses at a pulse repetition frequency between about 10 Hz and about 1 MHz. In some examples, the pulse repetition frequency of the light pulses can correspond to the acoustic resonance frequency of the ultrasonic receiver and the substrate. For example, a set of four or more light pulses can be emitted from the light source system 104 at a frequency corresponding to the resonance frequency of the resonant acoustic cavity in the sensor stack, allowing the establishment of the received ultrasonic waves and a higher resulting signal intensity. In some embodiments, the light source system 104 can include a filtered light or light source having a specific wavelength for detecting a selected material. In some embodiments, the light source system can include light sources, such as the red, green, and blue LEDs of a display, which can be enhanced with light sources of other wavelengths (such as IR and / or UV) and light sources having higher optical power. For example, a high-power laser diode or an electronic flash unit (e.g., an LED or a xenon flash unit) with or without a filter can be used for short-term illumination of the target object.

[0064] The control system 106 can include one or more general-purpose single-chip or multi-chip processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic, discrete hardware components, or combinations thereof. The control system 106 can also include one or more memory devices (and / or be configured to communicate therewith), such as one or more random access memory (RAM) devices, read-only memory (ROM) devices, etc. Thus, the apparatus 100 can have a memory system including one or more memory devices, although the memory system is not shown in Figure 1 as described below. The control system 106 can be configured to receive and process data from the receiver system 102, for example, as described below. If the apparatus 100 includes an ultrasonic transmitter, the control system 106 can be configured to control the ultrasonic transmitter. In some embodiments, the functions of the control system 106 can be divided among one or more controllers or processors, such as a dedicated sensor controller and an application processor of a mobile device.

[0065] In some examples, the control system 106 can be configured to control the light source system 104. For example, the control system 106 can be configured to control one or more light-emitting portions of the light source system 104 to emit laser pulses. In some examples, the laser pulses can be in the wavelength range of 500 nm to 1000 nm. In some examples, the laser pulses can have a pulse width in the range from 3 nanoseconds to 1000 nanoseconds. In some examples, the control system 106 can be configured to receive a signal from the ultrasonic receiver system 102, the signal corresponding to ultrasonic waves generated by the target object in response to light from the light source system 104. In some examples, the control system 106 can be configured to estimate one or more cardiac characteristics at least in part based on the signal. According to some examples, the cardiac characteristic can be or can include blood pressure.

[0066] Some embodiments of the apparatus 100 can include an interface system 108. In some examples, the interface system 108 can include a wireless interface system. In some embodiments, the interface system 108 can include a user interface system, one or more network interfaces, one or more interfaces between the control system 106 and the memory system and / or one or more interfaces between the control system 106 and one or more external device interfaces (e.g., ports or application processors), or a combination thereof. According to some examples where the interface system 108 is present and includes a user interface system, the user interface system can include a microphone system, a speaker system, a haptic feedback system, a voice command system, one or more displays, or a combination thereof. According to some examples, the interface system 108 can include a touch sensor system, a gesture sensor system, or a combination thereof. The touch sensor system (if present) can be or can include a resistive touch sensor system, a surface capacitive touch sensor system, a projected capacitive touch sensor system, a surface acoustic wave touch sensor system, an infrared touch sensor system, any other suitable type of touch sensor system, or a combination thereof.

[0067] In some examples, the interface system 108 can include a force sensor system. The force sensor system (if present) can be or can include a piezoresistive sensor, a capacitive sensor, a thin film sensor (e.g., a polymer-based thin film sensor), another suitable type of force sensor, or a combination thereof. If the force sensor system includes a piezoresistive sensor, the piezoresistive sensor can include silicon, metal, polysilicon, glass, or a combination thereof. In some examples, the interface system 108 can include an optical sensor system, one or more cameras, or a combination thereof.

[0068] According to some examples, the apparatus 100 may include a noise reduction system 110. For example, the noise reduction system 110 may include one or more mirrors configured to reflect light from the light source system 104 away from the receiver system 102. In some embodiments, the noise reduction system 110 may include one or more sound-absorbing layers, sound-insulating materials, light-absorbing materials, light-reflecting materials, or combinations thereof. In some examples, the noise reduction system 110 may include a sound-insulating material that may be located between at least a portion of the light source system 104 and the receiver system 102, on at least a portion of the receiver system 102, or a combination thereof. In some examples, the noise reduction system 110 may include one or more electromagnetic shielding transmission lines. In some such examples, the one or more electromagnetic shielding transmission lines may be configured to reduce electromagnetic interference received by the receiver system 102 from the circuitry of the light source system 104, the receiver system circuitry, or a combination thereof.

[0069] The apparatus 100 may be used in a variety of different contexts, many examples of which are disclosed herein. For example, in some embodiments, a mobile device may include the apparatus 100. In some such examples, the mobile device may be a smartphone. In some embodiments, a wearable device may include the apparatus 100. The wearable device may be, for example, a bracelet, armband, wristband, watch, ring, headband, or patch.

[0070] Figure 2 An example component of an apparatus according to some disclosed embodiments is shown. As with other figures provided herein, Figure 1 the Figure 2 number, type, and arrangement of the elements shown are presented merely as examples. In this example, the apparatus 100 is Figure 1 an instance of the apparatus 100 shown in the figure. According to this example, the apparatus 100 includes a platen 101, a receiver system 102, and a light source system 104. In this example, the outer surface 208a of the platen 101 is configured to accommodate a target object, such as a finger 255, a wrist, etc.

[0071] According to this example, the receiver system 102 is or includes an ultrasonic receiver system. In this example, the receiver system 102 includes a receiver stack portion 102a and a receiver stack portion 102b. In this example, the receiver stack portion 102a includes a piezoelectric material 215a, an electrode layer 220a on a first side of the piezoelectric material 215a, and an electrode layer 222a on a second side of the piezoelectric material 215a. According to some examples, an anisotropic conductive film (ACF) layer may be located between each of the electrode layers 220a and 220b and the piezoelectric material 215a. In this example, the electrode layer 222a is located between the piezoelectric material 215a and a backing layer 230a. The electrode layers 220a and 220b include a conductive material which, in some instances, may be or may include a conductive metal such as copper. The electrode layers 220a and 220b may be electrically connected to Figure 2 receiver system circuitry not shown. The receiver system circuitry may be considered part of the control system 106, part of the receiver system 102, or both as described herein with reference to Figure 1 The piezoelectric material 215a may include, for example, a polyvinylidene fluoride (PVDF) polymer, a polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) copolymer, aluminum nitride (AlN), lead zirconate titanate (PZT), a piezoelectric composite (such as a 1-3 composite, a 2-2 composite, a 3-3 composite, etc.), or a combination thereof. The backing layer 230a may be configured to suppress at least some acoustic artifacts and may provide a relatively high signal-to-noise ratio (SNR) compared to the receiver system 102 without the backing layer. In some examples, the backing layer 230a may include a metal, an epoxy resin, or a combination thereof.

[0072] In this example, the receiver stack portion 102b includes a piezoelectric material 215b, an electrode layer 220b on a first side of the piezoelectric material 215b, and an electrode layer 222b on a second side of the piezoelectric material 215b. Here, the electrode layer 222b is located between the piezoelectric material 215b and a backing layer 230b. According to this example, the receiver stack portion 102a is located near a first side of the light guide assembly 240a, and the receiver stack portion 102b is located near a second side of the light guide assembly 240a. In this example, the piezoelectric materials 215a and 215b are configured to generate electrical signals in response to received acoustic waves such as photoacoustic waves PA1 and PA2.

[0073] According to this example, the light source system 104 includes at least a first light emitting component (the light emitting component 235a in this example), at least a first light guiding component (the light guiding component 240a in this example), and the light source system circuit 245a. The light emitting component 235a can include, for example, one or more light emitting diodes, one or more laser diodes, one or more VCSELs, one or more edge emitting lasers, one or more neodymium doped yttrium aluminum garnet (Nd:YAG) lasers, or a combination thereof.

[0074] The light guiding component 240a can include any suitable material or combination of materials for causing at least some of the light emitted by the light emitting component 235a to propagate within the light guiding component 240a, for example due to total internal reflection between one or more core materials and one or more cladding materials of the light guiding component 240a. In such an example, the (one or more) core materials will have a higher refractive index than the (one or more) cladding materials. In a specific and non-limiting example, the core material can have a refractive index of approximately 1.64, and the cladding material can have a refractive index of approximately 1.3. In some examples, the core material can include glass, silica, quartz, plastic, zirconium fluoride, chalcogenide, or a combination thereof. According to some examples, the cladding material can include polyvinyl chloride (PVC), acrylic, polytetrafluoroethylene (PTFE), silicone, or fluororubber. In some examples, the light guiding component 240a can include one or more optical fibers. As used herein, the terms "light guide" and "light duct" can be used synonymously.

[0075] In some examples, the width W3 of the light guiding component 240a can be in the range of 0.25 mm to 3 mm, such as 0.5 mm, 1.0 mm, 1.5 mm, etc. According to some examples, the width W2 of the space between the receiver stack portion 102a and the receiver stack portion 102b can be in the range of 0.5 mm to 5 mm, such as 1.0 mm, 1.5 mm, 2 mm, 2.5 mm, etc. In some examples, the space 233a between the receiver stack portion 102a and the light guiding component 240a and the space 233b (if any) between the receiver stack portion 102b and the light guiding component 240a - in other words, the (one or more) spaces between W2 and W3 (if any) - can include light absorbing material. According to some examples, the spaces 233a and 233b (if any) can include air. In some examples, the spaces 233a and 233b (if any) can include sound absorbing material, preferably a sound absorbing material having a relatively low Grüneisen parameter.

[0076] In this example, the light source system 104 is configured to emit light through a first region of the platen towards a target object in contact with the first region of the platen 101. According to this example, the light source system 104 is configured to send light through the light guide assembly 240a and the platen region 201a towards the finger 255 in contact with the platen region 201a - represented by light rays 250a and 250b in Figure 2 . In this example, the arterial walls of the artery 207 generate photoacoustic waves PA1 and PA1 in response to the light rays 250a and 250b respectively.

[0077] The platen 101 may include any suitable material, such as glass, acrylic, polycarbonate, combinations thereof, etc. In some examples, the width W1 of the platen 101 may be in the range of 2 mm to 10 mm, such as 4 mm, 5 mm, 6 mm, etc. According to some examples, the thickness of the platen 101 (in the z - direction of the coordinate system shown in Figure 2 ) may be in the range of 50 microns to 500 microns, such as 150 microns, 200 microns, 250 microns, 300 microns, etc.

[0078] In this example, the platen 101 includes platen regions 201a, 201b, and 201c. In this example, the platen region 201a is located adjacent to the light guide assembly 240a. Thus, in this example, at least the platen region 201a includes a transparent material. According to some examples, the platen 101 may include one or more anti - reflection layers. In some examples, one or more anti - reflection layers may be located on or near the platen 101, such as on or near the outer surface 208a.

[0079] According to this example, the platen region 201b is located near the receiver stack portion 102a, and the platen region 201c is located near the receiver stack portion 102c. In this example, the mirror layer 205a, the matching layer 210a, and the adhesive layer 215a are located between the platen region 201b and the receiver stack portion 102a. Similarly, in this example, the mirror layer 205b, the matching layer 210b, and the adhesive layer 215b are located between the platen region 201c and the receiver stack portion 102b. The matching layers 210a and 210b may have an acoustic impedance that is selected to reduce the acoustic wave reflections caused by the acoustic impedance contrast between one or more layers of the receiver stack portions 102a and 102b adjacent to or near the matching layers 210a and 210b. According to some examples, the matching layers 210a and 210b may include polyethylene terephthalate (PET). In some examples, the adhesive layers 215a and 215b may include a pressure - sensitive adhesive (PSA) material.

[0080] In Figure 2In the example shown, the device has a thickness T1 (along the z-axis) from the top of the platen to the bottom of the backing layers 230a and 230b, and has a thickness T2 from the top of the platen to the bottom of the light source system circuitry. In some examples, T2 can be in the range of 2 mm to 10 mm. According to some examples, T1 can be in the range of 1 mm to 8 mm. The thickness of the backing layers 230a and 230b can be in the range of 3 mm to 7 mm, such as 4.5 mm, 5.0 mm, 5.5 mm, etc. Thus, embodiments without a backing layer can be much thinner than embodiments including one or more backing layers.

[0081] Figure 3A , Figure 3B and Figure 3C shows how some components of the device shown in Figure 2 can be arranged in different examples. As with other figures provided herein, Figure 1 the number, type, and arrangement of the elements shown in Figures 3A - 3C are presented merely as examples. In these examples, the device 100 is an instance of the device 100 shown in Figure 1 and Figure 2 . In each of these examples, a top view of the device 100 is shown, along the z-axis of the coordinate system shown in Figure 2 . In these examples, the light guide assembly 240a is shown as having a circular cross-section. However, in alternative examples, the light guide assembly 240a can have a different cross-sectional shape, such as a square cross-sectional shape, a rectangular cross-sectional shape, a hexagonal cross-sectional shape, etc.

[0082] In these examples, the outlines of the receiver stack portions 102a and 102b (and, in Figure 3B , the outlines of the receiver stack portions 102c - 102h) are shown in dashed lines, indicating that these elements are below the outer surface 208a of the platen 101. According to these examples, the receiver stack portion 102a is located near the first side of the light guide assembly 240a, and the receiver stack portion 102b is located near the second side of the light guide assembly 240a. In these examples, the receiver stack portion 102a is located near the platen region 102b on the first side of the platen region 102a (in this example, below, along the z-axis away from the observer), and the receiver stack portion 102b is located near the platen region 102c on the second opposite side of the platen region 102a.

[0083] According to the example shown in Figure 3A , the receiver stack portions 102a and 102b are discrete elements of a linear array of receiver stack portions having N receiver elements, where in this instance, N is 2. In alternative examples, N can be greater than 2.

[0084] In Figure 3B the example shown in Figure 3B , the receiver stack portions 102a and 102b are discrete elements of a two-dimensional receiver array of receiver stack portions having M receiver elements, where M is 9 in this instance. In alternative examples, M can be greater than or less than 9.

[0085] According to Figure 3C the example shown in Figure 3C , the receiver stack portions 102a and 102b are part of the receiver stack ring 305a. In this example, the receiver stack ring 305a is configured to surround the light guide assembly 240a. According to this example, the annular region of the platen 301 near the receiver stack ring 305a (above in this example, closer to the observer along the z-axis) that includes the platen regions 201b and 201c is configured to surround the platen region 201a.

[0086] Figure 3D Shows Figure 2 an example of the components of the device with additional components arranged as shown in Figure 2 . As with other attachments provided herein Figure 1 likewise, Figure 3D the number, type, and arrangement of the elements shown in Figure 3D are presented merely as examples. In these examples, the device 100 is Figure 1 an instance of the device 100 shown in Figure 1 . In this example, a top view of the device 100 is shown, which is along Figure 2 the z-axis of the coordinate system shown in Figure 2 . In this example, the light guide assembly 240a is shown as having a circular cross-section. However, in alternative examples, the light guide assembly 240a can have a different cross-sectional shape.

[0087] In this example, the receiver stack portions 102a and 102b are part of the receiver stack ring 305a. According to this example, the receiver stack ring 305a is configured to surround the light guide assembly 240a. In this example, the receiver stack ring 305a includes the receiver stack portions 102a and 102b, and the platen regions 201b and 201c. According to this example, the receiver stack ring 305b is configured to surround the receiver stack ring 305a. In this example, the receiver stack ring 305b includes the receiver stack portions 102c and 102d, and the platen regions 201j and 201k.

[0088] Figure 4 Shows an example of the components of the device according to some alternative embodiments. As with other attachments provided herein Figure 1 likewise, Figure 4 the number, type, and arrangement of the elements shown in Figure 4 are presented merely as examples. In this example, the device 100 isFigure 1 An example of the device 100 shown in Figure 2 All the elements shown in

[0089] In Figure 4 the optical coupling element 405 is shown as having a width (along the x-axis) that decreases from a first side coupled to the light-emitting component 235a to a second side coupled to the light guide component 240a. In some examples, the optical coupling element 405 may include one or more of the same materials as those forming the light guide component 240a. According to some alternative examples, the optical coupling element 405 may be or may include a lens configured to focus the light from the light-emitting component 235a onto the light guide component 240a. In some examples, the optical coupling provided by the optical coupling element 405 may allow the light guide component 240a to have a relatively smaller width or diameter than the light guide component 240a of the device 100 that does not include the optical coupling element 405.

[0090] Figure 5 An example of the components of a device according to some alternative embodiments is shown. As with other figures provided herein Figure 1 likewise, Figure 5 the number, type, and arrangement of the elements shown in Figure 1 An example of the device 100 shown in Figure 2 All the elements shown in

[0091] In this example, the light source system further includes a light guide assembly 240b configured to send light 250b from the light emitting assembly 235b to the light guide assembly 250a. Thus, in this example, the light source system includes at least a second light emitting assembly and at least a second light guide assembly, the second light guide assembly being configured to send light from the second light emitting assembly to at least a portion of the first light guide assembly. According to this example, the light guide assembly 240b is further configured to send light 250a from the light emitting assembly 235a to the light guide assembly 250a. Although the light guide assembly 240b is shown as having a 90-degree bend, this is merely an example. In some embodiments, the light guide assembly 240b may include a flexible material, such as one or more optical fibers, allowing the light guide assembly 240b to form an arcuate shape and a more gradual bend.

[0092] Figure 6 An example component of a device according to some alternative embodiments is shown. As with other figures provided herein, Figure 1 likewise, Figure 6 the number, type, and arrangement of elements shown are presented merely as examples. In this example, the device 100 is Figure 1 an instance of the device 100 shown. In this example, the light source system 104 includes at least a second light guide assembly configured to send light from a first light emitting assembly to a second region of the platen. According to this example, a second receiver stack ring surrounds the second region of the platen.

[0093] In this example, the light source system 104 includes a light emitting assembly 235a configured to provide light to a platen region 240a1 of the receiver stack ring 305a and a platen region 240a2 of the receiver stack ring 305c. In this example, the light emitting assembly 235a is configured to provide light to the platen region 240a1 via the light guide assemblies 240c and 240a1. According to this example, the light emitting assembly 235a is configured to provide light to the platen region 240a2 via the light guide assemblies 240c and 240a2.

[0094] Although in this example, the second region of the platen - in this instance region 201a2 - is surrounded by a second receiver stack ring, in other examples, the second region of the platen may be adjacent to other configurations of the receiver stack portion. In some alternative examples, the second region of the platen may be adjacent to a receiver stack portion in a linear array, such as in the Figure 3A example shown. In other examples, the second region of the platen may be adjacent to a receiver stack portion in a two-dimensional array, such as in the Figure 3B example shown.

[0095] Figure 7 An example component of a device according to some alternative embodiments is shown. As with other figures provided herein,Figure 1 Similarly, Figure 7 the number, type, and arrangement of the components shown are presented only as an example. In this example, device 100 is Figure 1 an instance of device 100 shown in

[0096] As described elsewhere herein, some embodiments of device 100 include one or more components configured for noise reduction. These noise reduction components may be considered part of the noise reduction system 110 described in reference Figure 1 However, such noise reduction components may be located in various parts of device 100.

[0097] One type of noise that may be present in device 100 involves light leakage from the light source system 104 (such as from Figure 7 the light guide assembly 240a) to the receiver system 102. According to Figure 7 the example shown in, device 100 includes a light mitigation element 705a located between the light guide assembly 240a and the receiver stack portion 102a, and a light mitigation element 705b located between the light guide assembly 240a and the receiver stack portion 102b. In this example, the light mitigation elements 705a and 705b are also located between the light guide assembly 240a and the mirror layers 205a and 205b, the matching layers 210a and 210b, and the adhesive layers 215a and 215b. In some examples, the light mitigation elements 705a and 705b may be discrete elements, while in other examples, the light mitigation elements 705a and 705b may be part of a continuous element, such as a cylinder surrounding the light guide assembly 240a. In some examples, the light mitigation elements 705a and 705b may include a material having a relatively low refractive index, such as a low refractive index foam. In this example, the light mitigation elements 705a and 705b are configured to increase optical coupling and reduce optical losses.

[0098] Another type of noise that may be present in device 100 involves EMI from the light source system circuit 245a, which may be received by the receiver system 102. In Figure 7 the example shown in, device 100 includes an EMI reduction element 710a near the receiver stack portion 102a and an EMI reduction element 710b near the receiver stack portion 102b. In some examples, the EMI reduction elements 710a and 710b may include one or more types of EMI shielding materials. According to some examples, the EMI reduction elements 710a and 710b may be part of a continuous element, such as a cylinder. In this example, the EMI reduction element 710c is located between the light source system circuit 245a and the receiver stack portions 102a and 102b. In some examples, the EMI reduction element 710c may surround the light source system circuit 245a.

[0099] According to Figure 7 the example shown in, the apparatus 100 includes an optical coupling component 405 configured to couple light from the light-emitting component 235a into the optical waveguide component 240a, as described above with reference to Figure 4 the foregoing. In this example, the optical coupling component 405 has a frustoconical outer surface 715. According to this example, the optical coupling component 405 is partially located between the receiver stack portions 102a and 102b and the optical waveguide component 240a to reduce the overall thickness of the apparatus 100 along the z-axis. Although some other disclosed embodiments are not shown as having an optical coupling component, alternative examples of such disclosed embodiments may actually include one or more optical coupling components.

[0100] Figures 2 - 7 The embodiment of the apparatus 100 shown in includes a light source system 104 having a light-emitting component located below the receiver stack portions 102a and 102b and the optical waveguide component 240a. (In this example, the term "below" means relatively farther in the negative direction along the z-axis relative to another element such as the platen 101. The reader will understand that the disclosed apparatus may be held in various orientations.) Referring to Figure 2 and Figure 3A it can be seen that in some such embodiments, the first receiver stack portion is located between the first portion of the first light-emitting component and the platen, and the second receiver stack portion is located between the second portion of the first light-emitting component and the platen. For example, referring to Figure 3A it can be seen that portions of the receiver stack portions 102a and 102b overlap with the light-emitting component 235a.

[0101] In various alternative embodiments, the light source system 104 may have one or more light-emitting components, light source system circuitry, or a combination thereof that is laterally displaced (also referred to herein as "laterally offset") from the receiver stack portions 102a and 102b, the optical waveguide component 240a, or both. In some such embodiments, another optical waveguide component may extend under the receiver stack portion 102a, the receiver stack portion 102b, or both. In such embodiments, the receiver stack portion 102a or the receiver stack portion 102b may be located between the second portion of another guiding component and the platen 101.

[0102] Figure 8 shows an example component of an apparatus according to some alternative embodiments. As with other figures provided herein Figure 1 the number, type, and arrangement of the elements shown in are presented only by way of example. In this example, the apparatus 100 is Figure 8 an instance of the apparatus 100 shown in Figure 1 .

[0103] In this example, the light-emitting component 235a and the light source system circuit 245a are not located below the receiver stack portions 102a and 102b and the light guide component 240a. Instead, according to this example, the light-emitting component 235a and the light source system circuit 245a are laterally offset from the receiver stack portions 102a and 102b and the light guide component 240a. This separation and the presence of the EMI-reducing elements 710a, 710b, and 710c can reduce the amount of electromagnetic interference generated by the light source system circuit 245a and received by the receiver system 102. In this example, the light-emitting component 235a and the light source system circuit 245a are located near the platen area 201l that is laterally offset from the platen areas 201a, 201b, and 201c.

[0104] In some embodiments, the receiver system circuit can also be laterally displaced from the receiver stack portions 102a and 102b and the light guide component 240a. According to some such embodiments, the receiver system circuit can also be encapsulated in an EMI-reducing material.

[0105] In this example, the light source system 104 is configured to send the light 250c from the light-emitting component 235a to the platen area 201a - and to the target object (if any) on the platen area 201a - via the light guide components 240d and 240a. Thus, in this example, the receiver stack portion 102b is located between the light guide component 240d and the platen 101.

[0106] Although the light guide component 240d is shown as having a 90-degree bend, this is merely an example. In some embodiments, the light guide component 240d can include a flexible material, such as one or more optical fibers, allowing the light guide components 240d and 240a to form an arcuate shape and a gentler bend.

[0107] Compared with the example where the light-emitting component 235a and the light source system circuit 245a are located below the receiver stack portions 102a and 102b and the light guide component 240a, such as Figure 8 the example shown in has the additional potential advantage of reducing the overall thickness of the device 100 in the z dimension. Although by comparing, for example, Figure 2 and Figure 8 the embodiments shown in, this difference does not seem obvious, but this is because the drawings are not necessarily drawn to scale. In some embodiments, the thickness of the light guide components 240d and 240a can be about 1 mm. Thus, the embodiment where the light-emitting component 235a and the light source system circuit 245a are laterally displaced from the receiver stack portions 102a and 102b and the light guide component 240a can reduce the overall thickness of the device 100.

[0108] Figure 9Shows example components of a device according to some alternative embodiments. As with other figures provided herein, Figure 1 the number, type, and arrangement of the elements shown Figure 9 are presented merely as examples. In this example, device 100 is Figure 1 an instance of the device 100 shown

[0109] Figure 9 The example of the device 100 shown Figure 8 is similar to the example shown: According to this example, the light-emitting component 235a and the light source system circuit 245a are laterally offset from the receiver stack portions 102a and 102b and the light guide component 240a. In this example, the light-emitting component 235a and the light source system circuit 245a are located near the platen area 201n that is laterally offset from the platen areas 201a, 201b, and 201c. In this example, the light source system 104 is configured to send the light 250d from the light-emitting component 235a to the platen area 201a - and the target object (if any) on the platen area 201a - via the light guide components 240e and 240a. Thus, in this example, the receiver stack portion 102b is located between the light guide component 240e and the platen 101.

[0110] However, in this example, the platen 101 includes platen portions 901a, 901b, and 901c. According to this example, the platen portion 901a is elevated relative to the platen portions 901b and 901c. In this example, the receiver stack portions 102a and 102b and the light guide component 240a are located near the platen portion 901a - below it in this example. Here, the light-emitting component 235a and the light source system circuit 245a are located below the platen portion 901c.

[0111] Therefore, in this example, the platen portion 901a and the receiver stack portions 102a and 102b and the light guide component 240a are configured to press into the surface of a target object (such as a finger, wrist, etc.). Configuring the platen portion 901a to press into the surface of the target object can provide potential advantages. For example, if the platen area 201a of the platen portion 901a near the light guide component 240a is pressed into the surface of the target object, this configuration can provide better coupling of the light 250d into the target object. If the platen areas 201b and 201c of the platen portion 901a - which are near the receiver stack portions 102a and 102b respectively - are pressed into the surface of the target object, this configuration can provide better coupling of the photoacoustic waves generated by the target object into the receiver stack portions 102a and 102b.

[0112] In some embodiments, the receiver system circuitry can also be laterally displaced from the receiver stack portions 102a and 102b and the light guide assemblies 240a. In some such embodiments, the receiver system circuitry can be located near (in this example, below) the platen portion 901b. According to some such embodiments, the receiver system circuitry can also be encapsulated in EMI-reducing material.

[0113] Figure 10 An example assembly of a device according to some alternative embodiments is shown. As with other figures provided herein, Figure 1 likewise, Figure 10 the number, type, and arrangement of the elements shown are presented merely as an example. In this example, the device 100 is Figure 1 an instance of the device 100 shown in

[0114] Figure 10 The example of the device 100 shown in Figure 8 is similar to the example shown in: according to this example, the light-emitting assembly 235a and the light source system circuitry 245a are laterally offset from the receiver stack portions 102a and 102b and the light guide assemblies 240a. In this example, the light source system 104 is configured to send light 250e from the light-emitting assembly 235a to the platen area 201a - and to a target object (if any) on the platen area 201a via the light guide assemblies 240f and 240a. Thus, in this example, the receiver stack portion 102b is located between the light guide assembly 240f and the platen 101.

[0115] However, in this example, the light guide assembly 240f includes only a single bend 1005, rather than Figure 8 the two bends in the light guide assembly 240d of

[0116] However, according to this example, the light-emitting assembly 235a and the light source system circuitry 245a extend below the receiver stack portions 102a and 102b (e.g., along the z-axis away from the surface 208a of the platen 101). Thus, assuming the components are otherwise the same, Figure 10 the device 100 shown in Figure 8 may be thicker than the device 100 of

[0117] The present inventors envision Figures 1 - 10 various arrangements and corresponding descriptions of the example shown in Figures 2 - 4 and Figures 6 - 10The light source system 104 is shown with only a single light-emitting component 235a, but in some alternative embodiments, each of these examples can include a light source system 104 having more than one light-emitting component. In some such examples, the light source system 104 can include L instances of the light-emitting component, where L is an integer greater than 1. In some examples, L can be 2, 3, 4, 5, 6, etc.

[0118] Similarly, although Figure 2 , Figure 3A , Figure 3C , Figure 4 , Figure 5 and Figures 7 - 10 only the receiver stack portions 102a and 102b are shown, but Figure 2 , Figure 3A , Figure 3C , Figure 4 , Figure 5 and Figures 7 - 10 alternative embodiments of can include additional receiver stack portions. The receiver stack portions can be arranged in one or more linear arrays, one or more regions, two-dimensional arrays, one or more rings, etc. Various arrangements of the receiver stack portions can have one, two, or more associated instances of the light-emitting component.

[0119] As described elsewhere herein, some embodiments of the device 100 can include a control system, and the control system can be an instance of the control system 106 of Figure 1 . In some embodiments, the control system can be configured to control the light source system 104. According to some embodiments, the control system can be configured to receive a signal corresponding to a sound wave from the receiver system 102, and the sound wave corresponds to the photoacoustic response of a target object to the light emitted by the light source system 104.

[0120] Figure 11 is a flowchart showing examples of some disclosed operations. Figure 11 The blocks of (and the blocks of other flowcharts provided herein) can be executed, for example, by the device 100 of Figure 1 or a similar device. Like other methods disclosed herein, Figure 11 The method outlined in can include more or fewer blocks than shown. Additionally, the blocks of the methods disclosed herein are not necessarily executed in the order indicated. In some instances, Figure 11 One or more of the blocks shown in can be executed simultaneously.

[0121] In this example, block 1105 involves controlling the light source system by the control system - which can be Figure 1An example of the light source system 104 - emits light towards a target object on or near the outer surface of the platen. Depending on the specific example, the target object can be a finger, a wrist, etc. According to this example, block 1110 involves receiving, by a control system, a signal from an ultrasound receiver system - which can be an Figure 1 example of the receiver system 102 - the signal corresponding to ultrasonic waves generated by the target object in response to the light emitted by the light source system.

[0122] According to this example, block 1115 involves the control system identifying a vascular signal from the ultrasound receiver system, the vascular signal corresponding to ultrasonic waves generated by blood within the blood vessels of the target object, one or more blood vessel walls, or a combination thereof. According to some examples, block 1115 can involve the control system identifying an arterial signal from the ultrasound receiver system, the arterial signal corresponding to ultrasonic waves generated by blood within the arteries of the target object, one or more arterial walls, or a combination thereof. For example, the vascular signal can be identified by implementing a range gating delay (RGD) corresponding to the expected depth of the blood vessel. Alternatively or additionally, the arterial signal can be identified based on one or more characteristics of the photoacoustic response of the blood vessel wall, blood, or a combination thereof.

[0123] In this example, block 1120 involves the control system estimating one or more cardiac characteristics at least in part based on the vascular signal. In some examples, block 1120 can involve estimating blood pressure at least in part based on the vascular signal. In some such examples, block 1120 can involve estimating blood pressure at least in part based on the arterial signal. According to some examples, block 1120 or another aspect of method 1100 can involve extracting and evaluating heart rate waveform (HRW) features.

[0124] Figure 12 Shows examples of heart rate waveform (HRW) features that can be extracted according to Figure 11 some embodiments of the method. Figure 12 The horizontal axis of represents time, and the vertical axis represents signal amplitude. The cardiac cycle is indicated by the time between adjacent peaks of the HRW. The systolic and diastolic time intervals are indicated below the horizontal axis. During the systolic phase of the cardiac cycle, when the pulse propagates through a specific location along the artery, the arterial wall expands according to the pulse waveform and the elastic properties of the arterial wall. Associated with the expansion is a corresponding increase in the blood volume at the specific location or region, and associated with the increase in blood volume is an associated change in one or more characteristics in that region. Conversely, during the diastolic phase of the cardiac cycle, the blood pressure in the artery decreases, and the arterial wall contracts. Associated with the contraction is a corresponding decrease in the blood volume at the specific location, and associated with the decrease in blood volume is an associated change in one or more characteristics in that region.

[0125] Figure 12The widths of the systolic and / or diastolic portions of the HRW features shown at various "heights" of the HRW curve, which are indicated as a percentage of the maximum amplitude. For example, the SW50 feature is the width of the systolic portion of the HRW curve at the "height" of 50% of the maximum amplitude. In some embodiments, the HRW features used for blood pressure estimation may include some or all of the SW10, SW25, SW33, SW50, SW66, SW75, DW10, DW25, DW33, DW50, DW66, and DW75 HRW features. In other embodiments, additional HRW features may be used for blood pressure estimation. In some instances, such additional HRW features may include the sum and ratio of SW and DW at one or more "heights", such as (DW75 + SW75), DW75 / SW75, (DW66 + SW66), DW66 / SW66, (DW50 + SW50), DW50 / SW50, (DW33 + SW33), DW33 / SW33, (DW25 + SW25), DW25 / SW25, and / or (DW10 + SW10), DW10 / SW10. Other embodiments may use other HRW features for blood pressure estimation. In some instances, such additional HRW features may include sums, differences, ratios, and / or other operations based on more than one "height", such as (DW75 + SW75) / (DW50 + SW50), (DW50 + SW50 / (DW10 + SW10), etc.

[0126] Figure 13 An example of a device that can be used in a system for estimating blood pressure based at least in part on pulse transit time (PTT) is shown. As with other figures provided herein, the number, type, and arrangement of elements are presented merely as examples. According to this example, system 1300 includes at least two sensors. In this example, system 1300 includes at least an electrocardiogram sensor 1305 and a device 1310 configured to be mounted on the finger of a person 1301. In this example, device 1310 is or includes a device configured to perform at least some of the PAPG methods disclosed herein. For example, device 1310 may be or may include Figure 1 device 300 or a similar device. Figure 1

[0127] As shown in graph 1320, PAT includes two components, pre-ejection period (PEP, the time required to convert an electrical signal into a mechanical pumping force and isovolumetric contraction to open the aortic valve) and PTT. The start time of PAT can be estimated based on the QRS complex - the electrical signal characteristic of the electrical stimulation of the ventricles. As shown in graph 1320, in this example, the start of the pulse arrival time (PAT) can be calculated based on the peak of the R wave measured by the electrocardiogram sensor 1305, and the end of PAT can be detected by analyzing the signal provided by the device 1310. In this example, it is assumed that the end of PAT corresponds to the intersection between the tangent of the local minimum detected by the device 1310 and the tangent of the maximum slope / first derivative of the sensor signal after the time of the minimum.

[0128] There are many known algorithms for blood pressure estimation based on PTT and / or PAT, some of which are summarized in Table 1 and described in the corresponding text on pages 5 - 10 of "Cuff-Less and Continuous Blood Pressure Monitoring: a Methodological Review" by Sharma, M. et al. in Technologies by the Multidisciplinary Digital Publishing Institute (MDPI) on May 21, 2017, both of which are incorporated herein by reference.

[0129] Some previously disclosed methods have involved calculating blood pressure based on PTT and / or PAT measured by a sensor system including a PPG sensor, according to one or more equations shown in Table 1 of Sharma or other known equations. As described above, some disclosed PAPG-based embodiments are configured to distinguish arterial HRW from other HRW. Such embodiments can provide a more accurate measurement of PTT and / or PAT relative to the PTT and / or PAT measured by the PPG sensor. Therefore, the disclosed PAPG-based embodiments can provide a more accurate blood pressure estimate, even if the blood pressure estimate is based on previously known formulas.

[0130] Other embodiments of the system 1300 may not include the electrocardiogram sensor 1305. In some such embodiments, the device 1315 configured to be mounted on the wrist of the person 1301 can be or can include means configured to perform at least some of the PAPG methods disclosed herein. For example, the device 1315 can be or can include Figure 2 the device 200 or a similar device. According to some such examples, the device 1315 can include a light source system and two or more ultrasonic receivers. An example is described below with reference to Figure 15A In some examples, the device 1315 can include an array of ultrasonic receivers.

[0131] In some embodiments of the system 1300 that do not include the electrocardiogram sensor 1305, the device 1310 may include a light source system and two or more ultrasonic receivers. The following references Figure 15B describe an example.

[0132] Figure 14 A cross-sectional side view showing a graphical representation of a portion of the artery 1400 through which the pulse 1402 propagates. Figure 14 The box arrows in [the figure] show the direction of blood flow and pulse propagation. As shown, the propagating pulse 1402 causes strain in the arterial wall 1404, which manifests as an expansion of the diameter (and thus cross-sectional area) of the arterial wall—a phenomenon called "dilation". The spatial length L of the actual propagating pulse along the artery (in the direction of blood flow) is typically comparable to the length of a limb, such as the distance from the shoulder of a subject to the wrist or finger of the subject, and is typically less than 1 meter (m). However, the length L of the propagating pulse can vary from subject to subject and can vary significantly over time for a given subject depending on various factors. The spatial length L of the pulse generally decreases as the distance from the heart increases until the pulse reaches the capillaries.

[0133] As described above, some specific embodiments relate to devices, systems, and methods for estimating blood pressure or other cardiovascular characteristics based on an estimate of an arterial dilation waveform. Unless otherwise indicated, the terms "estimate", "measure", "calculate", "infer", "derive", "evaluate", "determine", and "monitor" may be used interchangeably herein. Similarly, derivatives of the roots of these terms may also be used interchangeably as appropriate; for example, the terms "estimate", "measure", "calculate", "infer", and "determine" may also be used interchangeably herein. In some embodiments, the pulse wave velocity (PWV) of the propagating pulse can be estimated by measuring the pulse transit time (PTT) of the pulse as it propagates from a first physical location along the artery to another, more distal second physical location along the artery. It should be understood that this PTT is different from the PTT described above with reference to FIG. 15. However, either version of the PTT can be used for the purpose of blood pressure estimation. Assuming that the physical distance between the first physical location and the second physical location is determinable, the PWV can be estimated as the physical spatial distance traveled by the pulse divided by the time it takes for the pulse to traverse the physical spatial distance The quotient of the time used (PTT). Generally, a first sensor at a first physical location is used to determine the start time when a pulse arrives at or propagates through the first physical location (also referred to herein as the "first time location"). A second sensor at a second physical location is used to determine the end time when the pulse arrives at or propagates through the second physical location and continues through the remainder of the arterial branch (also referred to herein as the "second time location"). In such an example, PTT represents the time distance (or time difference) between the first time location and the second time location (start time and end time).

[0134] The fact that arterial dilation waveforms are measured at two different physical locations implies that the estimated PWV inevitably represents the entire path distance that the pulse travels between the first physical location and the second physical location averaged over. More specifically, PWV generally depends on multiple factors, including blood density , the stiffness of the arterial wall (or conversely, elasticity), arterial diameter, arterial wall thickness, and blood pressure. Since arterial wall elasticity and baseline resting diameter (e.g., the diameter at the end of ventricular diastole) vary significantly throughout the arterial system, the PWV estimate obtained from PTT measurements is an inherent average (averaged over the entire path length between the two locations where the measurements are performed). averaged over).

[0135] In traditional methods for obtaining PWV, an electrocardiogram (ECG) sensor has been used to obtain the start time of the pulse at the heart, which detects electrical signals from the heart. For example, the start time can be estimated based on the QRS complex - the electrical signal characteristics of the electrical stimulation of the ventricles. In such a method, a different sensor at a second location (e.g., a finger) is typically used to obtain the end time of the pulse. As those of ordinary skill in the art will understand, there are many arterial discontinuities, branches, and variations along the entire path length from the heart to the finger. Along each segment of the entire path length from the heart to the finger, the PWV can change by up to or more than an order of magnitude. Therefore, the PWV estimate based on such a long path length is unreliable.

[0136] In various embodiments described herein, a PTT estimate is obtained based on measurements (also referred to as "arterial distension data" or more generally as "sensor data") associated with arterial distension signals obtained by each of a first arterial distension sensor 1406 and a second arterial distension sensor 1408 at a first physical location and a second physical location along an artery of interest. In some particular embodiments, the first arterial distension sensor 1406 and the second arterial distension sensor 1408 are advantageously located near the first physical location and the second physical location, wherein between the first physical location and the second physical location, arterial properties of the artery of interest, such as wall elasticity and diameter, can be considered or assumed to be relatively constant. In this way, the PWV calculated based on the PTT estimate is more representative of the actual PWV along a specific segment of the artery. In turn, the blood pressure estimated based on the PWV is more representative of the true blood pressure. In some embodiments, the separation distance between the first arterial distension sensor 1406 and the second arterial distension sensor 1408 (and thus the distance between the first location and the second location along the artery) can range from about 1 centimeter (cm) to several tens of centimeters - long enough to distinguish the arrival of the pulse at the first physical location from the arrival of the pulse at the second physical location, but close enough to provide sufficient assurance of arterial consistency. In some specific embodiments, the distance between the first arterial distension sensor 1406 and the second arterial distension sensor 1408 can range from about 1 cm to about 30 cm, and in some embodiments, is less than or equal to about 20 cm, and in some embodiments, is less than or equal to about 10 cm, and in some specific embodiments, is less than or equal to about 5 cm. In some other embodiments, the distance between the first arterial distension sensor 1406 and the second arterial distension sensor 1408 can be less than or equal to 1 cm, for example, about 0.1 cm, about 0.25 cm, about 0.5 cm, or about 0.75 cm. As a reference, a typical PWV can be about 15 meters per second (m / s). Using a flow monitoring device with the first arterial distension sensor 1406 and the second arterial distension sensor 1408 separated by a distance of about 5 cm, and assuming a PWV of about 15 m / s implies a PTT of about 3.3 milliseconds (ms).

[0137] The magnitude value of the separation distance between the first arterial distension sensor 1406 and the second arterial distension sensor 1408 can be pre-programmed into the memory within the monitoring device incorporating the sensors (e.g., such as that referenced above Figure 1memory of the described control system 306, or a memory configured to communicate with the control system 306). As will be understood by one of ordinary skill in the art, in such an embodiment, the spatial length L of the pulse can be greater than the distance from the first arterial dilation sensor 1406 to the second arterial dilation sensor 1408 . Thus, although Figure 14 the graphical pulse 1402 shown in is shown as having a spatial length L comparable to the distance between the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408, in reality each pulse can typically have a spatial length L that is even much larger (e.g., about an order of magnitude or more) than the distance between the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408.

[0138] Sensing Architecture and Topology

[0139] In some embodiments of the flow monitoring device disclosed herein, the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408 are both sensors of the same sensor type. In some such embodiments, the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408 are the same sensor. In such an embodiment, each of the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408 utilizes the same sensor technology, has the same sensitivity to arterial dilation signals caused by propagating pulses, and has the same time delay and sampling characteristics. In some embodiments, each of the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408 is configured for photoacoustic plethysmography (PAPG) sensing, e.g., as disclosed elsewhere herein. Some such embodiments include a light source system and two or more ultrasonic receivers, which can be Figure 1Examples of the light source system 104 and the receiver system 102. In some embodiments, each of the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408 is configured for ultrasonic sensing by transmitting ultrasonic signals and receiving the corresponding reflected ultrasounds. In some alternative embodiments, each of the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408 may be configured for impedance plethysmography (IPG) sensing, also known as bioimpedance sensing in a biomedical context. In various embodiments, regardless of the type of sensor utilized, each of the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408 is widely used to capture and provide arterial dilation data indicative of an arterial dilation signal that is generated from the propagation of a pulse through a portion of an artery near which the respective sensor is located. For example, the arterial dilation data may be provided to the processor from the sensor in the form of a voltage signal generated or received by the sensor based on the ultrasonic signal or impedance signal sensed by the respective sensor.

[0140] As described above, during the systolic phase of the cardiac cycle, when a pulse propagates through a specific location along an artery, the arterial wall expands according to the pulse waveform and the elastic properties of the arterial wall. Associated with the expansion is a corresponding increase in the blood volume at the specific location or region, and associated with the increase in blood volume is an associated change in one or more properties in that region. Conversely, during the diastolic phase of the cardiac cycle, the blood pressure in the artery decreases, and the arterial wall contracts. Associated with the contraction is a corresponding decrease in the blood volume at the specific location, and associated with the decrease in blood volume is an associated change in one or more properties in that region.

[0141] In the context of bioimpedance sensing (or impedance plethysmography), the blood in an artery has a greater electrical conductivity than the surrounding or adjacent skin, muscle, fat, tendon, ligament, bone, lymph, or other tissues. The susceptance (and dielectric constant) of the blood also differs from the susceptance (and dielectric constant) of other types of surrounding or nearby tissues. When a pulse propagates through a specific location, the corresponding increase in blood volume results in an increase in the electrical conductivity at the specific location (and more generally, an increase in admittance, or equivalently, a decrease in impedance). Conversely, during the diastolic phase of the cardiac cycle, the corresponding decrease in blood volume results in an increase in the resistivity at the specific location (and more generally, an increase in impedance, or equivalently, a decrease in admittance).

[0142] Bioimpedance sensors typically operate by applying an electrical excitation signal at an excitation carrier frequency to a region of interest via two or more input electrodes and detecting an output signal (or output signals) via two or more output electrodes. In some more specific embodiments, the electrical excitation signal is a current signal injected into the region of interest via the input electrodes. In some such embodiments, the output signal is a voltage signal representative of the voltage response of the tissue in the region of interest to the applied excitation signal. The detected voltage response signal is affected by the different, and in some instances time-varying, electrical properties of the various tissues through which the injected excitation current signal passes. In some embodiments in which the bioimpedance sensor is operable to monitor blood pressure, heart rate, or other cardiovascular characteristics, the detected voltage response signal is amplitude and phase modulated by the time-varying impedance (or conversely, admittance) of the underlying artery, which fluctuates in synchrony with the user's heartbeat, as described above. To determine various biological characteristics, information in the detected voltage response signal is typically demodulated from the excitation carrier frequency component using various analog or digital signal processing circuits, which may include passive and active components.

[0143] In some examples incorporating an ultrasound sensor, measurement of arterial dilation can involve, for example, directing ultrasonic waves toward the artery into a limb via one or more ultrasound transducers. Such an ultrasound sensor is also configured to receive reflected waves that are at least partially based on the directed wave. The reflected waves can include scattered waves, specularly reflected waves, or both scattered and specularly reflected waves. The reflected waves provide information about the arterial wall and thus about arterial dilation.

[0144] In some embodiments, regardless of the type of sensors used for the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408, the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408 can be arranged, assembled, or otherwise included within a single housing of a single flow monitoring device. As described above, the housing and other components of the monitoring device can be configured such that when the monitoring device is secured or otherwise physically coupled to a subject, both the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408 are at separate distances at a first location and a second location in contact with or very close to the user's skin, and in some embodiments, along an arterial segment where various arterial properties can be assumed to be relatively constant therebetween. In various embodiments, the housing of the flow monitoring device is a wearable housing, or is incorporated into or integrated with a wearable housing. In some particular embodiments, the wearable housing includes (or is connected to) a physical coupling mechanism for removably and non-invasively attaching to the user. The housing can be formed using any of a variety of suitable manufacturing processes, including injection molding and vacuum molding, etc. Additionally, the housing can be made of a variety of suitable materials, including but not limited to plastics, metals, glass, rubber, and ceramics, or combinations of these or other materials. In a specific embodiment, the housing and the coupling mechanism are fully flowable for use. In other words, some embodiments of the wearable monitoring devices described herein are non-invasive, non-body-restraining, and generally do not restrict the unrestrained movement of the subject's arm or leg, such that cardiovascular properties, such as blood pressure, can be continuously or periodically monitored even when the subject is moving or otherwise engaged in physical activity. Thus, the flow monitoring device facilitates and enables long-term wearing and monitoring (e.g., for days, weeks, or a month or longer without interruption) of one or more biological properties of interest to obtain a better picture of such properties over an extended duration and generally a better picture of the user's health.

[0145] In some embodiments, the flow monitoring device can be placed around the user's wrist with a strap or band similar to a watch or a fitness / activity tracker. Figure 15A An example flow monitoring device 1500 designed to be worn around the wrist is shown in accordance with some embodiments. In the example shown, the monitoring device 1500 includes a housing 1502 integrally formed, coupled, or otherwise integrated with a wristband 1504. In some instances, the first arterial dilation sensor 1506 and the second arterial dilation sensor 1508 can each include an example of the ultrasound receiver system 102 and a portion of the light source system 104 described above with reference to Figure 1 In this example, the flow monitoring device 1500 is coupled around the wrist such that the first arterial dilation sensor 1506 and the second arterial dilation sensor 1508 within the housing 1502 are each placed along a segment of the radial artery 1510 (note that when the monitoring device is coupled to the subject, the sensors are typically hidden from the outside or outer surface of the housing facing the subject, but are exposed on the inner surface of the housing to enable the sensors to obtain measurements from the underlying artery through the subject's skin). Also as shown, the first arterial dilation sensor 1506 and the second arterial dilation sensor 1508 are separated by a fixed distance . In some other embodiments, the flow monitoring device 1500 can be similarly designed or adapted to be placed using a strip or band wrapped around the forearm, upper arm, ankle, calf, thigh, or finger (all of which are hereinafter referred to as "limb").

[0146] Figure 15B An example flow monitoring device 1500 designed to be worn on a finger according to some embodiments is shown. In some instances, the first arterial dilation sensor 1506 and the second arterial dilation sensor 1508 can each include an example of the ultrasonic receiver 102 and a portion of the light source system 104 described above with reference to Figure 1 the ultrasonic receiver 102 and a portion of the light source system 104 described above with reference to

[0147] In some other embodiments, the flow monitoring devices disclosed herein can be placed on an area of interest of the user without using a strip or band. For example, the first arterial dilation sensor 1506 and the second arterial dilation sensor 1508 and other components of the monitoring device can be encapsulated in a housing that is fixed to the skin of the area of interest of the user using an adhesive or other suitable attachment mechanism (an example of a "patch" monitoring device).

[0148] Figure 15C An example flow monitoring device 1500 designed to be located on an earbud is shown according to some embodiments. According to this example, the flow monitoring device 1500 is coupled to the housing of the earbud 1520. In some instances, the first arterial dilation sensor 1506 and the second arterial dilation sensor 1508 can each include an example of the ultrasonic receiver 102 and a portion of the light source system 104 described above with reference to Figure 1 the ultrasonic receiver 102 and a portion of the light source system 104 described above with reference to

[0149] Implementation examples are described in the following numbered clauses:

[0150] 1. A device, comprising: a platen; a light source system configured to emit light through a first region of the platen to a target object in contact with the first region of the platen, the light source system including at least a first light-emitting component and at least a first light guide component, the first light guide component being configured to send light from the first light-emitting component to the first region of the platen; and a receiver system including at least two receiver stack portions, a first receiver stack portion being located near a first side of a first portion of the first light guide component, and a second receiver stack portion being located near a second side of the first portion of the first light guide component, the receiver system being configured to detect sound waves corresponding to the photoacoustic response of the target object to the light emitted by the light source system.

[0151] 2. The device according to clause 1, wherein the first receiver stack portion is near a second region on a first side of the platen in the first region, and wherein the second receiver stack portion is near a third region on a second opposite side of the platen in the first region.

[0152] 3. The device according to clause 1 or clause 2, wherein the first receiver stack portion and the second receiver stack portion are parts of a first receiver stack ring.

[0153] 4. The device according to clause 3, wherein the first receiver stack ring is configured to surround a first part of the first light guide assembly.

[0154] 5. The device according to clause 3 or clause 4, wherein an annular region of the platen near the first receiver stack ring is configured to surround the first region of the platen.

[0155] 6. The device according to any one of clauses 3-5, further comprising a second receiver stack ring.

[0156] 7. The device according to clause 6, wherein the second receiver stack ring is configured to surround the first receiver stack ring.

[0157] 8. The device according to clause 6, wherein the light source system includes at least a second light guide assembly configured to send light from the first light emitting component to a second region of the platen, wherein the second receiver stack ring surrounds the second region of the platen.

[0158] 9. The device according to any one of clauses 1-8, wherein the light source system includes at least a second light emitting component and at least a second light guide assembly configured to send light from the second light emitting component to at least a part of the first light guide assembly.

[0159] 10. The device according to any one of clauses 1-9, wherein the receiver system includes a linear array of receiver stack portions.

[0160] 11. The device according to any one of clauses 1-10, wherein the receiver system includes a two-dimensional array of receiver stack portions.

[0161] 12. The device according to any one of clauses 1-11, wherein the first receiver stack portion is between a first part of the first light emitting component and the platen, and wherein the second receiver stack portion is between a second part of the first light emitting component and the platen.

[0162] 13. The device according to any one of clauses 1-12, wherein at least one of the first receiver stack portion or the second receiver stack portion is located between the second portion of the first light guide assembly and the platen.

[0163] 14. The device according to clause 13, further comprising at least one electromagnetic shielding layer located between the first light emitting assembly and the receiver system.

[0164] 15. The device according to any one of clauses 1-14, wherein the light source system comprises at least a first optical coupling component configured to couple light from the first light emitting assembly into the first light guide assembly.

[0165] 16. The device according to any one of clauses 1-15, wherein the first light emitting assembly is configured to emit laser pulses.

[0166] 17. The device according to clause 16, wherein the laser pulses are in a wavelength range of 500 nm to 1000 nm.

[0167] 18. The device according to clause 16 or clause 17, wherein the first light emitting assembly is configured to emit laser pulses with a pulse width in a range from 3 nanoseconds to 1000 nanoseconds.

[0168] 19. The device according to any one of clauses 1-18, wherein at least a first region of the platen is transparent.

[0169] 20. The device according to any one of clauses 1-19, wherein the combined thickness of the platen and the receiver stack portion is in a range from 2 mm to 8 mm.

[0170] 21. The device according to any one of clauses 1-20, further comprising a mirror system comprising a first mirror portion located between the platen and the first receiver stack portion and a second mirror portion located between the platen and the second receiver stack portion.

[0171] 22. The device according to any one of clauses 1-21, wherein the first light guide assembly comprises at least one optical fiber.

[0172] 23. The device according to any one of clauses 1-22, further comprising a control system configured to control the light source system.

[0173] 24. The device according to clause 23, wherein the control system is further configured to receive a signal corresponding to the sound wave from the receiver system.

[0174] 25. The apparatus according to clause 24, wherein the control system is further configured to estimate one or more cardiac characteristics based at least in part on the signal.

[0175] 26. An apparatus comprising: a platen; a light source component configured to emit light through a first region of the platen towards a target object in contact with the first region of the platen, the light source component including at least a first light emitting assembly and at least a first light guiding assembly, the first light guiding assembly being configured to send light from the first light emitting assembly to the first region of the platen; and a receiver system including at least two receiver stack portions, a first receiver stack portion being located near a first side of a first portion of the first light guiding assembly, and a second receiver stack portion being located near a second side of the first portion of the first light guiding assembly, the receiver system being configured to detect sound waves corresponding to a photoacoustic response of the target object to the light emitted by the light source component.

[0176] 27. The apparatus according to clause 26, wherein the first receiver stack portion is located near a second region on a first side of the platen in the first region, and wherein the second receiver stack portion is located near a third region on a second opposite side of the platen in the first region.

[0177] 28. The apparatus according to clause 26 or clause 27, wherein the first receiver stack portion and the second receiver stack portion are parts of a first receiver stack ring.

[0178] 29. A method comprising: causing a light source system to emit light through a first region of a platen towards a target object in contact with the first region of the platen, the light source system including at least a first light emitting assembly and at least a first light guiding assembly, the first light guiding assembly being configured to send light from the first light emitting assembly to the first region of the platen; and receiving, from a receiver system, a signal corresponding to sound waves caused by a photoacoustic response of the target object to the light emitted by the light source system, wherein the receiver system includes at least two receiver stack portions, a first receiver stack portion being located near a first side of a first portion of the first light guiding assembly, and a second receiver stack portion being located near a second side of the first portion of the first light guiding assembly.

[0179] 30. The method according to clause 29, wherein causing the light source system to emit light involves causing the light source system to emit laser pulses. As used herein, the phrase "at least one of" in a list of cited items means any combination of those items, including a single member. By way of example, "at least one of a, b, or c" is intended to cover: a, b, c, a - b, a - c, b - c, and a - b - c.

[0180] The various illustrative logical, logical blocks, modules, circuits, and algorithmic processes described in connection with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or a combination of both. The interchangeability of hardware and software has been described generally in terms of functionality and illustrated in the various illustrative components, blocks, modules, circuits, and processes described above. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

[0181] The hardware and data processing apparatus for implementing the various illustrative logical, logical blocks, modules, and circuits described in connection with the aspects disclosed herein can be implemented or executed with a general purpose single-chip or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, or any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some embodiments, the specific processes and methods may be performed by circuitry specific to a given function.

[0182] In one or more aspects, the described functionality may be implemented in hardware, digital electronic circuitry, computer software, firmware, including the structures disclosed in this specification and structural equivalents thereof, or any combination thereof. Embodiments of the subject matter described in this specification may also be implemented as one or more computer programs, i.e., one or more modules of computer program instructions, encoded on a computer storage medium for execution by, or to control the operation of, a data processing apparatus.

[0183] If implemented in software, these functions can be stored on or transmitted over a computer-readable medium (e.g., a non-transitory medium) as one or more instructions or code. The processes of the methods or algorithms disclosed herein can be implemented in a processor-executable software module, which can reside on a computer-readable medium. Computer-readable media include computer storage media and communication media including any medium that can transfer a computer program from one place to another. The storage media can be any available media accessible by a computer. By way of example and not limitation, non-transitory media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired program code in the form of instructions or data structures and that can be accessed by a computer. Similarly, any connection can be properly termed a computer-readable medium. Disk and optical disks used herein include compact disk (CD), laser disk, optical disk, digital versatile disk (DVD), floppy disk, and Blu-ray disk, where disks typically reproduce data magnetically, while optical disks reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. Additionally, operations of a method or algorithm can reside as one or any combination or set of code and instructions on a machine-readable medium and a computer-readable medium, which can be incorporated into a computer program product.

[0184] Various modifications to the embodiments described in this disclosure will be apparent to those of ordinary skill in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the claims, principles, and novel features disclosed herein. The term "exemplary" is used herein specifically to mean "serving as an example, instance, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior or better than other embodiments.

[0185] Certain features that are described in the context of separate embodiments in this specification can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented separately in multiple embodiments or in any suitable sub-combination. Additionally, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from the claimed combination can in some cases be deleted from the combination, and the claimed combination can be directed to a sub-combination or a variation of a sub-combination.

[0186] Similarly, although the operations are described in a specific order in the drawings, this should not be construed as requiring that the operations be performed in the specific order or sequence shown, or that all of the operations shown be performed, to obtain the desired result. In some cases, multitasking and parallel processing may be advantageous. Additionally, the separation of various system components in the above-described embodiments should not be construed as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other embodiments are within the scope of the appended claims. In some cases, the acts recited in the claims can be performed in a different order and still obtain the desired result.

[0187] It should be understood that unless the features in any specifically described embodiment are explicitly identified as being incompatible with each other, or the surrounding context implies that they are mutually exclusive and not readily combinable in a complementary and / or supportive sense, the overall concept of the present disclosure contemplates that the specific features of those complementary embodiments can be selectively combined to provide one or more comprehensive but slightly different technical solutions. Thus, it will be further understood that the above description is given by way of example only, and modifications in detail can be made within the scope of the present disclosure.

[0188] Various modifications to the embodiments described in this disclosure will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the appended claims are not intended to be limited to the embodiments shown herein but are to be accorded the widest scope consistent with the disclosure, the principles disclosed herein, and the novel features.

[0189] Additionally, certain features that are described in the context of separate embodiments in this specification can also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment can also be implemented separately in multiple embodiments or in any suitable sub-combination. Moreover, although features may be described as acting in certain combinations above and even initially claimed as such, one or more features from the claimed combination can in some cases be deleted from the combination, and the claimed combination can be directed to a sub-combination or a variant of a sub-combination.

[0190] Similarly, although the operations are described in a specific order in the figures, this should not be construed as requiring that the operations be performed in the specific order or sequence shown, or that all of the operations shown be performed to obtain the desired result. Additionally, the figures may schematically depict one or more example processes in the form of a flowchart. However, other operations not shown may be incorporated into the example processes schematically shown. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the operations shown. Further, the various operations described and shown may themselves include and collectively be referred to as multiple sub-operations. For example, each of the operations described above may itself involve the execution of a process or algorithm. Additionally, in some embodiments, the various operations described and shown may be combined or performed in parallel. Similarly, the separation of the various system components in the above-described embodiments should not be construed as requiring such separation in all embodiments. Thus, other embodiments are also within the scope of the appended claims. In some cases, the acts recited in the claims may be performed in a different order and still obtain the desired result.

Claims

1. A device, comprising: A pressing plate; A light source system configured to emit light to a target object in contact with a first region of the pressing plate through the first region of the pressing plate, the light source system including at least a first light-emitting component and at least a first light guide component, the first light guide component being configured to send light from the first light-emitting component to the first region of the pressing plate; And A receiver system including at least two receiver stack portions, a first receiver stack portion being located near a first side of a first portion of the first light guide component, and a second receiver stack portion being located near a second side of the first portion of the first light guide component, the receiver system being configured to detect sound waves corresponding to a photoacoustic response of the target object to the light emitted by the light source system.

2. The device according to claim 1, wherein The first receiver stack portion is located near a second region on a first side of the pressing plate in the first region, and wherein the second receiver stack portion is located near a third region on a second opposite side of the pressing plate in the first region.

3. The device according to claim 1, wherein, The first receiver stack portion and the second receiver stack portion are parts of a first receiver stack ring.

4. The apparatus according to claim 3, wherein, The first receiver stack ring is configured to surround the first portion of the first light guide component.

5. The device according to claim 3, wherein, An annular region of the pressing plate near the first receiver stack ring is configured to surround the first region of the pressing plate.

6. The device according to claim 3, further comprising a second receiver stack ring.

7. The apparatus according to claim 6, wherein, The second receiver stack ring is configured to surround the first receiver stack ring.

8. The apparatus according to claim 6, wherein, The light source system includes at least a second light guide component configured to send light from the first light-emitting component to a second region of the pressing plate, wherein the second receiver stack ring surrounds the second region of the pressing plate.

9. The device according to claim 1, wherein The light source system includes at least a second light-emitting component and at least a second light guide component, the second light guide component being configured to send light from the second light-emitting component to at least a portion of the first light guide component.

10. The apparatus according to claim 1, wherein, The receiver system includes a linear array of receiver stack portions.

11. The device according to claim 1, wherein, The receiver system includes a two-dimensional array of receiver stack portions.

12. The apparatus according to claim 1, wherein The first receiver stack portion is located between a first portion of the first light-emitting component and the pressing plate, and wherein the second receiver stack portion is located between a second portion of the first light-emitting component and the pressing plate.

13. The device according to claim 1, wherein, At least one of the first receiver stack portion or the second receiver stack portion is located between a second portion of the first light guide component and the pressing plate.

14. The device according to claim 13, further comprising at least one electromagnetic shielding layer located between the first light-emitting component and the receiver system.

15. The device according to claim 1, wherein, The light source system includes at least a first optical coupling component configured to couple light from the first light-emitting component into the first light guide component.

16. The device according to claim 1, wherein, The first light-emitting component is configured to emit laser pulses.

17. The apparatus according to claim 16, wherein, The laser pulses are in a wavelength range of 500 nm to 1000 nm.

18. The apparatus according to claim 16, wherein, The first light-emitting component is configured to emit laser pulses with a pulse width in a range from 3 nanoseconds to 1000 nanoseconds.

19. The device according to claim 1, wherein, At least a first region of the pressure plate is transparent.

20. The apparatus according to claim 1, wherein, The combined thickness of the pressure plate and the receiver stack portion is in the range from 2 mm to 8 mm.

21. The apparatus according to claim 1, further comprising a mirror system, the mirror system including a first mirror portion located between the pressure plate and the first receiver stack portion and a second mirror portion located between the pressure plate and the second receiver stack portion.

22. The device according to claim 1, wherein, The first light guide assembly includes at least one optical fiber.

23. The apparatus according to claim 1, further comprising a control system configured to control the light source system.

24. The apparatus according to claim 23, wherein, The control system is further configured to receive a signal corresponding to the acoustic wave from the receiver system.

25. The apparatus according to claim 24, wherein, The control system is further configured to estimate one or more cardiac characteristics based at least in part on the signal.

26. An apparatus, comprising: A pressure plate; A light source component for emitting light through a first region of the pressure plate to a target object in contact with the first region of the pressure plate, the light source component including at least a first light emitting assembly and at least a first light guide assembly, the first light guide assembly being configured to send the light from the first light emitting assembly to the first region of the pressure plate; And A receiver system including at least two receiver stack portions, a first receiver stack portion being located near a first side of a first portion of the first light guide assembly, and a second receiver stack portion being located near a second side of the first portion of the first light guide assembly, the receiver system being configured to detect an acoustic wave corresponding to a photoacoustic response of the target object to the light emitted by the light source component.

27. The apparatus according to claim 26, wherein, The first receiver stack portion is located near a second region on a first side of the pressure plate in the first region, and wherein the second receiver stack portion is located near a third region on a second opposite side of the pressure plate in the first region.

28. The apparatus according to claim 26, wherein, The first receiver stack portion and the second receiver stack portion are parts of a first receiver stack ring.

29. A method, comprising: Causing a light source system to emit light through a first region of a pressure plate to a target object in contact with the first region of the pressure plate, the light source system including at least a first light emitting assembly and at least a first light guide assembly, the first light guide assembly being configured to send the light from the first light emitting assembly to the first region of the pressure plate; And Receiving, from a receiver system, a signal corresponding to an acoustic wave caused by a photoacoustic response of the target object to the light emitted by the light source system, wherein the receiver system includes at least two receiver stack portions, a first receiver stack portion being located near a first side of a first portion of the first light guide assembly, and a second receiver stack portion being located near a second side of the first portion of the first light guide assembly.

30. The method according to claim 29, wherein, Causing the light source system to emit light involves causing the light source system to emit laser pulses.

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