Multispectral photoacoustic device

Abstract

An apparatus may include a platen, a light source system configured to provide first light of a first wavelength and second light of a second wavelength to a target object along a first axis, an ultrasonic receiver system, and a control system. The control system may be configured to cause the light source system to provide a first light to a target object at a first time and a second light to the target object at a second time; receiving a first ultrasonic receiver signal and a second ultrasonic receiver signal from the ultrasonic receiver system corresponding to a photoacoustic response of the target object to the first light and the second light, respectively; and estimating one or more vascular characteristics based on at least one of the first ultrasound receiver signal or the second ultrasound receiver signal.

Description

[0001] Priority Statement

[0002] This application claims priority to U.S. Patent Application No. 18 / 461,397, filed September 5, 2023, entitled “MULTISPECTRAL PHOTOACOUSTICDEVICES,” which is incorporated herein by reference for all purposes. Technical Field

[0003] This disclosure relates in general to photoacoustic devices and systems.

[0004] Related technical descriptions

[0005] Various sensing technologies and algorithms are being implemented in devices for a wide range of biometric and biomedical applications, including health and wellness monitoring. This push is partly driven by the limitations of traditional measurement devices for continuous, non-invasive, and non-bedridden monitoring. Some of these devices are or include photoacoustic devices. While some previously deployed photoacoustic devices and systems have provided acceptable results, improved photoacoustic devices and systems are desirable. Summary of the Invention

[0006] The systems, methods, and apparatuses disclosed herein each have several aspects, none of which individually assumes responsibility for the desired properties disclosed herein.

[0007] One innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus. In some specific embodiments, a mobile device (such as a wearable device, a cellular phone, etc.) may be at least part of the apparatus or may include at least part of the apparatus. The apparatus may include a pressure plate, a light source system, and a receiver system. The receiver system may be or may include an ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to light from the light source system. According to some examples, the light source system may be configured to provide light to the target object on the outer surface of the pressure plate. In some examples, the light may include at least a first wavelength (such as light having an amplitude peak at the first wavelength) and a second wavelength (such as light having an amplitude peak at the second wavelength).

[0008] In some implementations, the device may include a control system. The control system may 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 components, discrete hardware components, or combinations thereof. The control system may be configured to: provide a first light source to a target object at a first time; receive a first ultrasonic receiver signal from an ultrasonic receiver system corresponding to the photoacoustic response of the target object to the first light; provide a second light source to the target object at a second time; receive a second ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the second light; and distinguish the desired signal from one or more background signals, at least in part, based on the first and second ultrasonic receiver signals.

[0009] According to some embodiments, the device may include a pressure plate and a light source system configured to provide light to a target object on the outer surface of the pressure plate, the light including at least a first wavelength emitted by a first light-emitting device and a second wavelength emitted by a second light-emitting device. In some examples, the light source system may be configured to provide the first light to the target object along a first axis and may be configured to provide the second light to the target object along the first axis. According to some embodiments, the device may include an ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to the light from the light source system; and a control system configured to: cause the light source system to provide the first light to the target object at a first time; receive a first ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the first light; cause the light source system to provide the second light to the target object at a second time; receive a second ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the second light; and estimate one or more vascular features based on at least one of the first ultrasonic receiver signal or the second ultrasonic receiver signal.

[0010] In some embodiments, the device may include a pressure plate and a light source system configured to provide light to a target object on the outer surface of the pressure plate, the light comprising at least a first wavelength emitted by a first light-emitting device and a second wavelength emitted by a second light-emitting device. In some examples, the light source system may include a light guide system configured to deliver the first and second light to the pressure plate. In some such embodiments, the device may include an ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to the light from the light source system; and a control system configured to: cause the light source system to provide the first light to the target object at a first time; receive a first ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the first light; cause the light source system to provide the second light to the target object at a second time; receive a second ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the second light; and estimate one or more vascular features based on at least one of the first or second ultrasonic receiver signals.

[0011] According to some specific embodiments, the device may include a pressure plate and a light source system configured to provide light to a target object on the outer surface of the pressure plate, the light including at least a first wavelength emitted by a first light-emitting device and a second wavelength emitted by a second light-emitting device. In some examples, the light source system may include: a light guide system including one or more light guides configured to transport light in a direction parallel to or substantially parallel to the outer surface of the pressure plate; and an ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to the light from the light source system. According to some such specific embodiments, the device may include a control system configured to: cause the light source system to provide the first light to the target object at a first time; receive a first ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the first light; cause the light source system to provide second light to the target object at a second time; receive a second ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the second light; and estimate one or more vascular features based on at least one of the first or second ultrasonic receiver signals.

[0012] In some embodiments, the light guide system may include a plurality of light extraction elements residing within the one or more light guides. These light extraction elements may be configured to guide light toward the pressure plate. In some examples, these light extraction elements may include one or more recesses in the light guide surface, one or more protrusions on the light guide surface, or one or more structures formed on the light guide surface. According to some examples, these light extraction elements may include one or more three-dimensional shapes formed by these recesses in the light guide surface, these protrusions on the light guide surface, or these structures formed on the light guide surface. In some examples, these light extraction elements may include one or more beam splitters. According to some examples, these light extraction elements may include one or more mirrors or other reflective structures. In some examples, a two-dimensional array of light extraction elements may be configured to provide substantially uniform light to an illumination area on the outer surface of the pressure plate. According to some examples, at least some of the light extraction elements may be arranged with unequal spacing within the one or more light guides. In some such examples, light extraction elements located farther from the first light-emitting device may be spaced closer together than light extraction elements located closer to the first light-emitting device.

[0013] In some examples, the desired signal may correspond to blood vessels within the target object. According to some examples, the control system may be further configured to estimate one or more vascular features based on at least one of the first ultrasound receiver signal or the second ultrasound receiver signal. In some examples, the one or more vascular features may include vessel diameter, vessel area, vessel profile, vascular dilation, volumetric flow rate, pulse wave velocity, vessel wall thickness, or combinations thereof. According to some examples, the control system may be further configured to estimate blood pressure at least in part based on the one or more vascular features.

[0014] Other innovative aspects of the subject matter described in this disclosure can be implemented in a method. In some examples, the method may involve: providing a first wavelength of light to a target object at a first time; receiving a first ultrasonic receiver signal from an ultrasonic receiver system corresponding to the photoacoustic response of the target object to the first light; providing a second wavelength of light to the target object at a second time; receiving a second ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the second light; and distinguishing the desired signal from one or more background signals based at least in part on the first and second ultrasonic receiver signals.

[0015] In some examples, the desired signal may correspond to blood vessels within the target object. According to some examples, the method may involve estimating one or more vascular features based on at least one of the first ultrasound receiver signal or the second ultrasound receiver signal. In some examples, the one or more vascular features may include vessel diameter, vessel area, vessel profile, vascular dilation, volumetric flow rate, pulse wave velocity, vessel wall thickness, or combinations thereof. According to some examples, the method may involve estimating blood pressure based at least in part on the one or more vascular features.

[0016] Some or all of the methods described herein can be executed by one or more devices according to instructions (e.g., software) stored on a non-transitory medium. Such non-transitory media 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. Therefore, some innovative aspects of the subject matter described herein can be implemented in one or more non-transitory media on which software is stored. The software may include instructions for controlling one or more devices to perform one or more of the disclosed methods.

[0017] Details of one or more specific embodiments 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, drawings, and claims. Note that the relative dimensions in the following drawings are not to scale. Attached Figure Description

[0018] Figure 1 This is a block diagram illustrating example components of a device according to some disclosed specific implementations.

[0019] Figure 2A An example of a pulse emitted by a light source system and a corresponding receiver signal is shown.

[0020] Figure 2B An example is shown that distinguishes the desired signal from one or more background signals.

[0021] Figure 2C Additional examples are shown that distinguish the desired signal from one or more background signals.

[0022] Figure 3 The components of the apparatus according to some of the disclosed specific embodiments are shown.

[0023] Figure 4 Example components of a device according to some alternative specific implementations are shown.

[0024] Figure 5A , Figure 5B and Figure 5C It shows Figure 4Different examples of how some components of the device can be arranged.

[0025] Figure 5D The diagram shows the arrangement of additional components. Figure 4 Examples of components of the device shown.

[0026] Figure 6 Example components of a device according to some alternative specific implementations are shown.

[0027] Figure 7 Example components of a device according to some alternative specific implementations are shown.

[0028] Figure 8A and Figure 8B Example components of a device according to some alternative specific implementations are shown.

[0029] Figure 9A , Figure 9B ,and Figure 9C Example components of a device according to some alternative specific implementations are shown.

[0030] Figure 10A and Figure 10B Example components of a device according to some alternative specific implementations are shown.

[0031] Figure 11 This is a flowchart illustrating some examples of the disclosed operations.

[0032] Figure 12 It shows that it can be based on Figure 11 Examples of specific implementations of the method for extracting heart rate waveform (HRW) features.

[0033] 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.

[0034] Figure 14 A cross-sectional side view of a portion of an artery through which a pulse is propagating.

[0035] Figure 15A An example of a non-bedridden monitoring device designed to be worn around the wrist, according to some specific implementations, is shown.

[0036] Figure 15B An example of a non-bedridden monitoring device 1500 designed to be worn on a finger is shown according to some specific implementations.

[0037] Figure 15C An example of a non-bedridden monitoring device 1500 designed to reside on an earpiece is shown according to some specific implementations.

[0038] The same reference numerals and names in the various figures indicate the same elements. Detailed Implementation

[0039] The following description is directed to certain specific embodiments and is intended to describe various aspects of this disclosure. However, those skilled 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 this disclosure are particularly applicable to blood pressure monitoring applications. However, some specific embodiments are also applicable to other types of biosensing applications, as well as other fluid flow systems. The described specific embodiments can be implemented in any device, apparatus, or system that includes the means disclosed herein. Furthermore, it is contemplated that the described specific embodiments can be included in or associated with various electronic devices, such as, but not limited to: mobile phones, cellular phones with multimedia-enabled networks, mobile TV receivers, wireless devices, smartphones, smart cards, wearable devices (such as wristbands, armbands, wrist straps, rings, headbands, patches, etc.), Bluetooth. ® Devices, personal data assistants (PDAs), wireless email receivers, handheld or portable computers, netbooks, laptops, smartbooks, tablet devices, printers, copiers, scanners, fax machines, GPS receivers / navigators, cameras, digital media players, game consoles, wristwatches, clocks, computers, 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 displays of rearview cameras in vehicles), building structures, microwave ovens, refrigerators, stereo systems, cassette recorders or players, DVD players, CD players, VCRs, radios, portable storage chips, washing machines, dryers, washer / dryer units, parking meters, car doors, autonomous or semi-autonomous vehicles, drones, Internet of Things (IoT) devices, etc. Therefore, this teaching is not intended to be limited to the specific implementations depicted and described with reference to the accompanying drawings; rather, its applicability is broad and will be apparent to those skilled in the art.

[0040] Non-invasive health monitoring devices, such as those with photoacoustic plethysmography (PAPG) capability, offer a variety of potential advantages compared to more invasive health monitoring devices, such as those with cuff capability or catheter-based blood pressure measurement devices. However, it has proven difficult to design satisfactory PAPG-capable devices. For example, some PAPG-capable devices recently developed by the assignee have been able to provide light at only a single peak wavelength.

[0041] Some of the disclosed devices include a pressure plate, a light source system, a receiver system, and a control system. The receiver system may be or may include an ultrasonic receiver system. According to some examples, the light source system may be configured to provide light to a target object on the outer surface of the pressure plate. In some examples, the light may include at least a first wavelength (such as light having an amplitude peak at the first wavelength) and a second wavelength (such as light having an amplitude peak at the second wavelength). Such devices are examples of devices that may be referred to herein as multispectral photoacoustic devices.

[0042] According to some examples, the control system can be configured to: provide a first wavelength of light to a target object at a first time; and receive a first ultrasonic receiver signal from an ultrasonic receiver system corresponding to the photoacoustic response of the target object to the first light. In some examples, the control system can be configured to: provide a second wavelength of light to the target object at a second time; receive a second ultrasonic receiver signal from an ultrasonic receiver system corresponding to the photoacoustic response of the target object to the second light; and distinguish a desired signal from one or more background signals, at least in part, based on the first and second ultrasonic receiver signals. In some cases, the desired signal may correspond to at least a portion of a blood vessel within the target object. According to some examples, the light source system can be configured to provide the first and second light to the target object along the same axis.

[0043] 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 are multispectral photoacoustic devices capable of distinguishing a desired signal from one or more background signals, at least in part, based on an ultrasonic receiver signal corresponding to the photoacoustic response of a target object to light at two or more peak frequencies. In some disclosed examples, the multispectral photoacoustic device may be able to provide enhanced optical contrast for the desired signal. At least some disclosed devices are devices with PAPG capability. In some such examples, the desired signal may correspond to at least a portion of a blood vessel. Enhanced distinction between vascular signals and background signals can provide more accurate blood pressure estimation. However, some other disclosed multispectral photoacoustic devices may be able to provide additional functionality, such as blood oxygen estimation, blood glucose estimation, chemical sensing for industrial applications, etc. Some relevant examples of the context of such specific implementations are described in the following articles: Glière, Alain et al., “Challenges in the design and fabrication of a lab-on-a-chip photoacoustic gas sensor”, Sensors 14, No. 1 (2014), pp. 957–974; and Horvath, Thomas D et al., “Ratiometric photoacoustic sensing of pH using a “sonophore””, Analyst 133, No. 6 (2008), pp. 747–749, both of which are incorporated herein by reference.

[0044] Figure 1 This is a block diagram illustrating example components of a device according to some of the disclosed specific embodiments. In this example, device 100 includes a pressure plate 101, a receiver system 102, a light source system 104, and a control system 106. Some specific embodiments of device 100 may include an interface system 108, a noise reduction system 110, or both.

[0045] This document discloses various examples of the pressure plate 101, the light source system 104, and the receiver system 102. Some examples are described in more detail below.

[0046] The pressure plate 101 may be made of any suitable material, such as glass, acrylic, polycarbonate, etc. According to some examples, the pressure plate 101 (or another part of the device) may include one or more anti-reflective layers. In some examples, one or more anti-reflective layers may reside on or near one or more outer surfaces of the pressure plate 101.

[0047] In some examples, at least a portion of the outer surface of the pressure plate 101 may have an acoustic impedance configured to approximate the acoustic impedance of human skin. A portion of the outer surface of the pressure plate 101 may, for example, be a portion configured to receive a target object, such as a human finger. (As used herein, the terms "finger" and "fingertip" are used interchangeably, such that the thumb is an example of a finger.) Typical acoustic impedance of human skin ranges from 1.53 MRayl to 1.680 MRayl. In some examples, at least the outer surface of the pressure plate 101 may have an acoustic impedance in the range of 1.4 MRayl to 1.8 MRayl, or in the range of 1.5 MRayl to 1.7 MRayl. Alternatively or additionally, in some examples, at least the outer surface of the pressure plate 101 may be configured to conform to the surface of human skin. In some such examples, at least the outer surface of the pressure plate 101 may have material properties similar to putty or chewing gum.

[0048] In some examples, at least a portion of the pressure plate 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, a layer residing between the pressure plate 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 residing between the pressure plate 101 and one or more receiver elements may have an acoustic impedance within a range between the acoustic impedance of the pressure plate and the acoustic impedance of the one or more receiver elements.

[0049] In some examples, the light source system 104 may be configured to emit light toward a target object in contact with the first region of the pressure plate 101 through a first region of the pressure plate 101. According to some examples, the light source system 104 may include at least a first light-emitting element configured to emit first light of a first wavelength (such as light having an amplitude peak at the first wavelength) and a second light-emitting element configured to emit second light of a second wavelength (such as light having an amplitude peak at the second wavelength). In some examples, the light source system 104 may be configured to emit light at more than two wavelengths. In some specific implementations, the light may be laser light.

[0050] According to some examples, the light source system 104 may be configured to provide first and second light to a target object along the same axis (which may be referred to herein as the first axis). In some such examples, the receiver system 102 may receive ultrasonic receiver signals from the target object along a second axis different from (e.g., not parallel to) the first axis. According to some examples, the second axis may be separated from the first axis by an angle ranging from 10 degrees to 60 degrees. However, in some alternative embodiments, the receiver system 102 may receive ultrasonic receiver signals from the target object along a second axis parallel to or substantially parallel to the first axis. In this context, "substantially parallel" may mean within ±5 degrees, within ±10 degrees, within ±15 degrees, within ±20 degrees, etc.

[0051] In some examples, the light source system 104 may include a light guide system having one or more light guide components. The light guide system may be configured to deliver light from the light source system to a pressure plate. In some examples, the light guide component may include one or more optical fibers. According to some examples, a first light guide component may be configured to transmit light from a first light-emitting component to a first region of the pressure plate, or to another light guide component. In some examples, a second light guide component may be configured to transmit light from a second light-emitting component to a first region of the pressure plate, or to another light guide component.

[0052] According to some examples, the light guide assembly can be configured to deliver light in a direction parallel to or substantially parallel to the pressure plate. In this context, "substantially parallel" can mean within ±5 degrees, within ±10 degrees, etc. In some such examples, the light guide assembly may include light extraction elements (such as beam splitters) configured to direct light from the light guide assembly toward the pressure plate.

[0053] In some examples, receiver system 102 may include at least two receiver stack portions: a first receiver stack portion may reside near a first side of a first portion of the first light guide assembly, and a second receiver stack portion may reside near a second side of the first portion of the first light guide assembly. In some examples, the first and second receiver stack portions may be portions of a first receiver stack ring. The receiver stack ring may be configured to surround a portion of the light guide assembly. In some examples, receiver system 102 may be configured to detect acoustic waves corresponding to the photoacoustic response of a target object to light emitted by the light source system.

[0054] This document discloses various examples of receiver system 102, some of which may include an ultrasonic receiver system, an optical receiver system, or a combination thereof. In some embodiments where 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, receiver system 102 may include a piezoelectric receiver layer, such as a polyvinylidene fluoride (PVDF) polymer layer, a polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) copolymer, a piezoelectric composite, etc. In some embodiments, a single piezoelectric layer may be used as an ultrasonic receiver. In some embodiments, other piezoelectric materials, such as aluminum nitride (AlN) or lead zirconate titanate (PZT), may be used in the piezoelectric layer. In some examples, receiver system 102 may include an array of ultrasonic transducer elements, such as an array of piezoelectric micromechanical ultrasonic transducers (PMUTs), an array of capacitive micromechanical ultrasonic transducers (CMUTs), etc. In some such examples, a piezoelectric receiver layer, PMUT elements in a single-layer array of PMUTs, or 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, receiver system 102 may be or may include an array of ultrasonic receivers. In some examples, 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.

[0055] In some examples, the light source system 104 may include one or more light-emitting diodes (LEDs). 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.

[0056] In some examples, the light source system 104 may be configured to emit light in one or more wavelength ranges. In some examples, the light source system 104 may be configured to emit light in the 500 nm to 600 nm wavelength range. According to some examples, the light source system 104 may be configured to emit light in the 800 nm to 950 nm wavelength range.

[0057] Depending on the specific implementation, the light source system 104 may include various types of driving circuitry. In some disclosed embodiments, the light source system 104 may include at least one multi-junction laser diode that generates less noise than a single-junction laser diode. In some examples, the light source system 104 may include driving circuitry (also referred to herein as driving circuitry) configured to cause the light source system to emit light pulses with pulse widths ranging from 3 nanoseconds to 1000 nanoseconds. According to some examples, the light source system 104 may include driving circuitry configured to cause the light source system to emit light pulses at pulse repetition frequencies ranging from 1 kHz to 100 kHz.

[0058] In some embodiments, the apparatus (e.g., receiver system 102, 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 material may reside between at least a portion of receiver system 102 and light source system 104. In some examples, the apparatus (e.g., receiver system 102, light source system 104, or both) may include one or more electromagnetically shielded transmitting lines. In some such examples, the one or more electromagnetically shielded transmitting lines may be configured to reduce electromagnetic interference received by receiver system 102 from light source system 104.

[0059] In some embodiments, the light source system 104 can be configured to emit light of various wavelengths, which can be selected to trigger acoustic emission primarily from a specific type of material. For example, because heme in blood absorbs near-infrared light very strongly, in some embodiments, the light source system 104 can be configured to emit light of one or more wavelengths in the near-infrared range to trigger acoustic emission from heme. However, in some examples, the control system 106 can control the wavelength of the light emitted by the light source system 104 to preferentially sense acoustic waves in blood vessels, other soft tissues, and / or bones. For example, an infrared (IR) light-emitting diode (LED) can be selected, and short pulses of IR light can be emitted to illuminate a portion of a target object and generate acoustic 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), can be selected, and short pulses of light can be emitted sequentially from each light source, wherein an ultrasound image is obtained after each light source emits light. In other embodiments, one or more light sources of different wavelengths can be lit sequentially or simultaneously to generate acoustic emission that can be detected by an ultrasound receiver. Image data from an ultrasound receiver, acquired using light sources of different wavelengths and at different depths (e.g., varying RGDs) within a target object, can be combined to determine the location and type of material within the target object. Image contrast is possible because materials in a body typically absorb light of different wavelengths differently. When a material in a body absorbs light of a specific wavelength, it may heat up in different ways, generating acoustic emission of light pulses with sufficient intensity and shortness. Depth contrast can be obtained using light of different wavelengths and / or intensities at selected wavelengths. That is, continuous images can be obtained at a fixed RGD (which may correspond to a fixed depth of the target object) using varying light intensities and wavelengths to detect material and its location within the target object. For example, hemoglobin, blood glucose, or blood oxygen within blood vessels of a target object (such as a finger) can be detected photoacously.

[0060] According to some embodiments, the light source system 104 can be configured to emit light pulses with a pulse width of less than about 100 nanoseconds. In some embodiments, the light pulses may have a pulse width between about 10 nanoseconds and about 500 nanoseconds or longer. According to some examples, the light source system can be configured to emit multiple 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 multiple 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 multiple 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 may correspond to the acoustic resonant frequency of the ultrasonic receiver and the substrate. For example, a set of four or more light pulses may be emitted from the light source system 104 at a frequency corresponding to the resonant frequency of the resonant acoustic cavity in the sensor stack, allowing for the accumulation of received ultrasonic waves and a higher resulting signal strength. In some embodiments, filtered light or a light source with a specific wavelength for detecting the selected material may be included in the light source system 104. In some embodiments, the light source system may contain light sources such as red, green, and blue LEDs for displays, which may be enhanced by light sources of other wavelengths (such as IR and / or UV) and light sources with higher optical power. For example, high-power laser diodes or electronic flash units (e.g., LED or xenon flash units) with or without filters may be used for short-term irradiation of the target object.

[0061] The control system 106 may 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 components, discrete hardware components, or combinations thereof. The control system 106 may also include (and / or be configured to communicate with) one or more memory devices such as one or more random access memory (RAM) devices, read-only memory (ROM) devices, etc. Therefore, the device 100 may have a memory system including one or more memory devices, but... Figure 1 The memory system is not shown. The control system 106 can be configured to receive and process data from the receiver system 102, for example, as described below. If the device 100 includes an ultrasonic transmitter, the control system 106 can be configured to control the ultrasonic transmitter. In some implementations, the functionality of the control system 106 can be divided among one or more controllers or processors, such as between a dedicated sensor controller and an application processor in a mobile device.

[0062] In some examples, the control system 106 may be configured to control the light source system 104. For example, the control system 106 may 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 may be in the wavelength range of 600 nm to 1000 nm. In some examples, the laser pulses may have a pulse width in the range of 3 nanoseconds to 1000 nanoseconds.

[0063] According to some examples, the control system 106 may be configured to control a first light-emitting element of the light source system 104 to provide first light of a first wavelength to a target object at a first time. In some examples, the control system 106 may be configured to receive a first ultrasonic receiver signal from an ultrasonic receiver system corresponding to the photoacoustic response of the target object to the first light. In some examples, the control system 106 may be configured to control a second light-emitting element of the light source system 104 to provide second light of a second wavelength to the target object at a second time. According to some examples, the control system 106 may be configured to receive a second ultrasonic receiver signal from an ultrasonic receiver system corresponding to the photoacoustic response of the target object to the second light.

[0064] In some examples, the control system 106 may be configured to distinguish a desired signal from one or more background signals, at least in part, based on a first ultrasound receiver signal and a second ultrasound receiver signal. According to some examples, the desired signal may correspond to a blood vessel within a target object. In some examples, the control system 106 may be configured to estimate one or more vascular features based on the first ultrasound receiver signal, the second ultrasound receiver signal, or both. One or more vascular features may include vessel diameter, vessel area, vessel profile, vascular dilation, volumetric flow rate, pulse wave velocity, vessel wall thickness, or combinations thereof. In some examples, the control system 106 may be configured to evaluate one or more cardiac features, such as blood pressure, at least in part, based on one or more vascular features.

[0065] According to some examples, the control system 106 may be configured to control a first emitting element of the light source system 104 to provide a first laser pulse of a first wavelength to the target object at a first time, and to control a second emitting element of the light source system 104 to provide one or more second laser pulses of a second wavelength to the target object at a second time. In some such examples, there may be a time interval of only a few microseconds between the first and second times, such as 5 nanoseconds (ns), 6 ns, 7 ns, 8 ns, 9 ns, 10 ns, 11 ns, 12 ns, 13 ns, 14 ns, 15 ns, etc. According to some such examples, the first laser pulse may cause a photoacoustic response to be emitted from the target object and may also increase the local temperature in the target area of ​​the target object. In some such examples, one or more second laser pulses may also irradiate the target area. In some cases, because the Grüneisen parameter is temperature-dependent and because the first laser pulse increases the local temperature in the target area, one or more second laser pulses may produce a nonlinearly enhanced photoacoustic response from the target area. According to some examples, the control system 106 may be configured to receive a first ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to a first laser pulse, and to receive a second ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to one or more second laser pulses. In some examples, the control system 106 may be configured to control a first light-emitting element of the light source system 104 to provide one or more first laser pulses instead of a single first laser pulse.

[0066] Some specific embodiments of device 100 may include interface system 108. In some examples, interface system 108 may include a wireless interface system. In some specific embodiments, interface system 108 may include a user interface system, one or more network interfaces, one or more interfaces between control system 106 and memory system, and / or one or more interfaces between control system 106 and one or more external device interfaces (e.g., ports or application processors), or combinations thereof. According to some examples where interface system 108 is present and includes a user interface system, the user interface system may include a microphone system, a speaker system, a haptic feedback system, a voice command system, one or more displays, or combinations thereof. According to some examples, interface system 108 may include a touch sensor system, a gesture sensor system, or combinations thereof. The touch sensor system (if present) may be or may 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 combinations thereof.

[0067] In some examples, interface system 108 may include a force sensor system. The force sensor system (if present) may be or may 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 may include silicon, metal, polycrystalline silicon, glass, or a combination thereof. In some examples, interface system 108 may include an optical sensor system, one or more cameras, or a combination thereof.

[0068] According to some examples, device 100 may include a noise reduction system 110. For example, noise reduction system 110 may include one or more mirrors configured to reflect light from light source system 104 away from receiver system 102. In some specific implementations, 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, noise reduction system 110 may include sound-insulating materials that may reside between, on, or in at least a portion of receiver system 102 and light source system 104. In some examples, noise reduction system 110 may include one or more electromagnetically shielded transmission lines. In some such examples, the one or more electromagnetically shielded transmission lines may be configured to reduce electromagnetic interference received by receiver system 102 from circuitry of light source system 104, receiver system circuitry, or combinations thereof.

[0069] Device 100 can be used in a variety of different contexts, many of which are disclosed herein. For example, in some embodiments, a mobile device may include device 100. In some such examples, the mobile device may be a smartphone. In some embodiments, a wearable device may include device 100. Wearable devices may be, for example, bracelets, armbands, wristbands, watches, rings, headbands, or patches.

[0070] Figure 2A An example of a pulse emitted by a light source system and a corresponding receiver signal is shown. In this example, the light source system has a first light-emitting element configured to emit a first light of a first wavelength and a second light-emitting element configured to emit a second light of a second wavelength. According to this example, the first light-emitting element is a VCSEL-1, which is configured to emit laser light having an amplitude peak at the first wavelength. In this example, the second light-emitting element is a VCSEL-2, which is configured to emit laser light having an amplitude peak at the second wavelength.

[0071] According to this example, the control system controls the light source system to provide a first light to the target object at a first time, which is a time interval starting at approximately 0 microseconds (μs) in Figure 205. Figure 205 shows a first ultrasonic receiver signal 210 from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the first light. In this example, the control system controls the light source system to provide a second light to the target object at a second time, which is a time interval starting at approximately 10 microseconds in Figure 205. Figure 205 shows a second ultrasonic receiver signal 215 from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the second light.

[0072] Figure 2B An example is shown that distinguishes the desired signal from one or more background signals. Figure 220 shows the ultrasonic receiver signal corresponding to the photoacoustic response of the target object, where the vertical axis indicates the amplitude and the horizontal axis indicates the time in microseconds × 10⁻⁶. -2 The time unit is defined as 1000 time units in Figure 220, which equals 10 microseconds. Curve 225 indicates the ultrasonic receiver signal corresponding to the photoacoustic response of the target object to a first light with a peak amplitude at a wavelength of 808 nanometers (nm), and curve 230 indicates the ultrasonic receiver signal corresponding to the photoacoustic response of the target object to a second light with a peak amplitude at a wavelength of 940 nm. In these examples, both the first and second lights are laser lights.

[0073] In these examples, the peaks and troughs during the first 200 time units in Figure 220 are shown to correspond to electromagnetic interference (EMI). Such signals can be considered as examples of system noise. Because EMI does not vary with the wavelength of the light used for illumination, curves 225 and 230 can be observed to overlap during this time interval.

[0074] The peaks and troughs during a time interval of approximately 400 to 660 time units correspond to the photoacoustic responses of one or more skin layers and the photoacoustic responses from subepidermal features, which in this example include vascular features. The signal corresponding to the blood vessels is an example of a signal that may be referred to herein as the “desired signal.” Curves 225 and 230 are observed not to overlap at various points within this time interval. Between approximately 400 to 520 time units (e.g., near peak 235 corresponding to the skin photoacoustic response), the signal corresponding to light with a peak amplitude at a wavelength of 808 nm has a relatively higher amplitude than the signal corresponding to light with a peak amplitude at a wavelength of 940 nm. In some examples, the control system may assign higher weight to the signal corresponding to light with a peak amplitude at a wavelength of 808 nm used for imaging skin features in this time interval. In some examples, the control system may use the signal corresponding to light with a peak amplitude at a wavelength of 808 nm for imaging skin features in this time interval and may discard the signal corresponding to light with a peak amplitude at a wavelength of 940 nm.

[0075] However, between approximately 550 and 650 time units (e.g., near peak 240 corresponding to the anterior wall of the artery), the signal corresponding to light with a peak amplitude at a wavelength of 808 nm has a relatively lower amplitude than the signal corresponding to light with a peak amplitude at a wavelength of 940 nm. In some examples, the control system may assign higher weight to the signal corresponding to light with a peak amplitude at a wavelength of 940 nm used for imaging vascular features in this time interval. In some examples, the control system may use the signal corresponding to light with a peak amplitude at a wavelength of 940 nm for imaging vascular features in this time interval and may discard the signal corresponding to light with a peak amplitude at a wavelength of 808 nm.

[0076] Therefore, devices with multispectral PAPG capabilities can provide enhanced differentiation between vascular and background signals, and can provide more accurate measurements of vascular features such as vessel diameter, vessel area, vessel profile, vascular dilation, volumetric flow rate, pulse wave velocity, vessel wall thickness, or combinations thereof. Since various methods of blood pressure estimation are partly based on the measured vascular features, more accurate measurements of vascular features provided by some of the disclosed devices with multispectral PAPG capabilities can also provide more accurate blood pressure estimates.

[0077] Multispectral photoacoustic devices can enhance the differentiation of desired signals from other types of background signals. For example, multispectral photoacoustic devices can enhance the differentiation of signals corresponding to skin melanin signals, which typically have high absorption at relatively short light wavelengths (such as those in the 400 nm to 500 nm range) and low absorption at longer light wavelengths (such as those in the 800 nm to 900 nm range).

[0078] Figure 2C Additional examples are shown to distinguish the desired signal from one or more background signals. Figure 250 shows the ultrasonic receiver signal corresponding to the photoacoustic response of the target object, where the vertical axis indicates the photoacoustic amplitude in arbitrary units (au) and the horizontal axis indicates the time unit in microseconds. Curves 255, 260, 265, and 270 indicate the amplitude of the ultrasonic receiver signal corresponding to the photoacoustic response of the target object to light with peak amplitude at wavelengths of 875 nm, 800 nm, 725 nm, and 650 nm, respectively, corresponding to 0.02 mm. -1 0.04mm -1 0.06mm -1 and 0.08mm -1 It is absorbed by the skin.

[0079] In these examples, the peaks and troughs in Figure 250 during the first 1.7 microseconds correspond to EMI and to the photoacoustic response of one or more skin layers. Such reflections can be considered examples of background signals. The portions of curves 255 to 270 corresponding to EMI can be observed to overlap with each other; however, the portions of curves 255 to 270 corresponding to the skin vary significantly, primarily due to the different absorption of light by the skin at different wavelengths.

[0080] Figure 3 Components of an apparatus according to some of the disclosed specific embodiments are shown. As with the other figures provided herein, Figure 3 The number, type, and arrangement of the components shown are presented by way of example only. In this example, device 100 is... Figure 1 An example of device 100 is shown. According to this example, device 100 includes a pressure plate 101, a receiver system 102, and a light source system 104. In this example, the outer surface 308a of the pressure plate 101 is configured to receive a target object 355, which in this example is a finger.

[0081] According to this example, the light source system 104 includes a light-emitting component 335a and a corresponding light source system circuit 345a, a light-emitting component 335b and a corresponding light source system circuit 345b, and light guiding elements 310a, 310b, and 310c. According to this example, the light guiding elements 310a, 310b, and 310c are a mirror, a lens, and a beam splitter, respectively. The light-emitting components 335a and 335b may, for example, include one or more light-emitting diodes, one or more laser diodes, one or more VCSELs, one or more edge-emitting lasers, one or more Nd:YAG lasers, or combinations thereof.

[0082] In this example, light-emitting component 335a is configured to emit light 305a, and light-emitting component 335b is configured to emit light 305b (in... Figure 3 (Seen as a thick dashed line). According to this example, light 305a and light 305b have amplitude peaks at different wavelengths. In some specific implementations, the light source system 104 may include a light guide configured to direct light from the light source system 104 toward the pressure plate 101.

[0083] According to this example, the light source system 104 is configured to guide light 305a and light 305b toward the target object 355 along the same axis (which in this case is axis 315a). In this example, axis 315a is at an angle Θ1 relative to axis 315b, which is normal to the outer surface 308a of pressure plate 101. In some examples, angle Θ1 may be in the range of 10 degrees to 60 degrees. In this example, light guiding element 310a is configured to reflect light emitted by light-emitting component 335a toward light guiding element 310b. According to this example, light guiding element 310c is configured to guide light emitted by light-emitting components 335a and 335b along axis 315a. In this example, light guiding element 310b is configured to focus light reflected by light guiding element 310a. In some cases, light guiding element 310b may be configured to focus light reflected by light guiding element 310a onto light guiding element 310c.

[0084] According to some alternative examples, the light source system 104 may be configured to direct light 305a and light 305b toward target object 355 substantially along the same axis. In this context, "substantially along the same axis" may mean within ±5 degrees, within ±10 degrees, within ±15 degrees, etc.

[0085] In this example, light beams 305a and 305b generate a photoacoustic response in the target object 355, causing the target object 355 to emit sound waves 340. At least some of the sound waves 340 are ultrasonic waves traveling along axis 315b toward the receiver system 102. Therefore, the sound waves 340 cause ultrasonic receiver signals from the receiver system 102 corresponding to the photoacoustic response of the target object 355 to light beams 305a and 305b.

[0086] Figure 4 Example components of a device according to some alternative embodiments are shown. As with the other figures provided herein, Figure 4 The number, type, and arrangement of the components shown are presented by way of example only. In this example, device 100 is... Figure 1 An example of device 100 is shown. According to this example, device 100 includes a pressure plate 101, a receiver system 102, and a light source system 104. In this example, the outer surface 408a of the pressure plate 101 is configured to receive a target object, which in this example is a finger 355.

[0087] In this example, the light source system 104 includes light-emitting components 435a and 435b, and light source system circuitry 445a and 445b. The light-emitting components 435a and 435b may, for example, include one or more light-emitting diodes, one or more laser diodes, one or more VCSELs, one or more edge-emitting lasers, one or more Nd:YAG lasers, or combinations thereof. In this example, the light source system 104 includes L examples of light-emitting components, where L is an integer greater than 1. In this example, L equals 2. In other examples, L may be greater than 2. Therefore, in this example, the light source system includes at least a second light-emitting component and at least a second light-guiding component.

[0088] According to this example, the light source system 104 includes a light guide component 440a configured to transmit light 450a from the light-emitting component 435a to the light guide component 440c. In this example, the light source system also includes a light guide component 440b configured to transmit light 450b from the light-emitting component 435b to the light guide component 440c. Therefore, in this example, 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 transmit light from the second light-emitting component to at least a portion of the first light guide component.

[0089] Although the light guide assemblies 440a and 440b are shown as having a 90-degree bend, these are merely examples. According to some other specific implementations (including, but not limited to, those shown...), the actual implementation may vary. Figure 8A and Figure 8B(As shown in the example) Optical guide components 440a and 440b may have different shapes. In some specific implementations, optical guide components 440a and 440b may include flexible materials (such as one or more optical fibers), allowing optical guide components 440a and 440b to be formed into arcuate shapes and more progressive bends.

[0090] According to this example, receiver system 102 is or includes an ultrasonic receiver system. In this example, receiver system 102 includes receiver stack portion 102a and receiver stack portion 102b. In this example, receiver stack portion 102a includes piezoelectric material 415a, electrode layer 420a on a first side of piezoelectric material 415a, and electrode layer 422a on a second side of piezoelectric material 415a. According to some examples, an anisotropic conductive film (ACF) layer may reside between each of electrode layers 420a and 420b and piezoelectric material 415a. In this example, electrode layer 422a resides between piezoelectric material 415a and backing layer 430a. Electrode layers 420a and 420b include a conductive material, which may be or may include a conductive metal (such as copper in some cases). Electrode layers 420a and 420b may be electrically connected to receiver system circuitry, which is not in... Figure 4 As shown in the diagram. The receiver system circuitry can be considered as a reference. Figure 1 This is part of the control system 106, part of the receiver system 102, or both described herein. The piezoelectric material 415a may include, for example, a polyvinylidene fluoride (PVDF) polymer, a polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) copolymer, aluminum nitride (AlN), lead zirconate titanate (PZT), piezoelectric composite materials (such as 1-3 composites, 2-2 composites, 3-3 composites, etc.), or combinations thereof.

[0091] Backing layers 430a and 430b can be configured to suppress at least some artifacts and provide a relatively higher signal-to-noise ratio (SNR) than receiver system 102 lacking a backing layer. In some examples, backing layers 430a and 430b may comprise metal, epoxy resin, or a combination thereof. According to this example, backing layers 430a and 430b extend from electrode layers 422a and 422b to the base of light source system circuits 445a and 445b. In some examples, backing layers 430a and 430b may be part of a continuous structure, such as a ring structure. In some examples, backing layers 430a and 430b may surround light source system circuits 445a and 445b, light-emitting components 435a and 435b, and light-guiding components 440a and 440b.

[0092] In this example, the receiver stack portion 102b includes a piezoelectric material 415b, an electrode layer 420b on a first side of the piezoelectric material 415b, and an electrode layer 422b on a second side of the piezoelectric material 415b. Here, the electrode layer 422b resides between the piezoelectric material 415b and the backing layer 430b. According to this example, the receiver stack portion 102a resides near the first side of the light guide assembly 440c, and the receiver stack portion 102b resides near the second side of the light guide assembly 440c. In this example, the piezoelectric materials 415a and 415b are configured to generate electrical signals in response to received acoustic waves (such as photoacoustic waves PA1 and PA2).

[0093] The light guide components 440a, 440b, and 440c may comprise any suitable material or combination of materials for propagating at least some of the light emitted by the light-emitting components 435a and 435b within the light guide components 440a, 440b, and 440c, for example, due to total internal reflection between one or more core materials and one or more cladding materials of the light guide components 440a, 440b, and 440c. In such examples, the core material will have a higher refractive index than the cladding material. In a specific and non-limiting example, the core material may have a refractive index of about 1.64, and the cladding material may have a refractive index of about 1.3. In some examples, the core material may comprise glass, silica, quartz, plastic, zirconium fluoride, chalcogenides, or combinations thereof. According to some examples, the cladding material may comprise polyvinyl chloride (PVC), acrylic, polytetrafluoroethylene (PTFE), polysiloxane, or fluorocarbon rubber. In some examples, the light guide components 440a, 440b, and 440c may include one or more optical fibers. As used herein, the terms "light guide" and "light duct" are used synonymously.

[0094] In some examples, the width W3 of the light guide component 440c may 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 may 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 433a between the receiver stack portion 102a and the light guide component 440c and the space 433b between the receiver stack portion 102b and the light guide component 440c (if either exists), in other words, the space between W2 and W3 (if either exists), may include light-absorbing material. According to some examples, spaces 433a and 433b (if either exists) may include air. In some examples, spaces 433a and 433b (if either exists) may include sound-absorbing material, preferably a sound-absorbing material with a relatively low Green'sson parameter.

[0095] In this example, the light source system 104 is configured to emit light toward a target object in contact with the first region of the pressure plate 101 through a first region of the pressure plate. According to this example, the light source system 104 is configured to direct light (in the light guide assembly 440c and the pressure plate region 401a) through the light guide assembly 440c and the pressure plate region 401a. Figure 4 The light rays (represented by ray 450a and 450b) are directed toward the finger 355 in contact with the pressure plate area 401a. In this example, the arterial wall of artery 407 generates photoacoustic waves PA1 and PA2 in response to light rays 450a and 450b, respectively.

[0096] The pressure plate 101 may comprise any suitable material, such as glass, acrylic resin, polycarbonate, combinations thereof, etc. In some examples, the width W1 of the pressure plate 101 may range from 2 mm to 10 mm, for example, 4 mm, 5 mm, 6 mm, etc. According to some examples, the thickness of the pressure plate 101 (in...) Figure 4 The coordinate system shown (in the z-direction) can be located in the range of 50 micrometers to 500 micrometers, for example, 150 micrometers, 200 micrometers, 250 micrometers, 300 micrometers, etc.

[0097] In this example, the pressure plate 101 includes pressure plate regions 401a, 401b, and 401c. In this example, pressure plate region 401a resides adjacent to the light guide component 440c. Therefore, in this example, at least pressure plate region 401a includes a transparent material. According to some examples, the pressure plate 101 may include one or more anti-reflective layers. In some examples, one or more anti-reflective layers may reside on or near the pressure plate 101, for example, on or near the outer surface 408a.

[0098] According to this example, pressure plate region 401b resides near receiver stack portion 102a and pressure plate region 401c resides near receiver stack portion 102c. In this example, mirror layer 405a, matching layer 410a, and adhesive layer 415a reside between pressure plate region 401b and receiver stack portion 102a. Similarly, in this example, mirror layer 405b, matching layer 410b, and adhesive layer 415b reside between pressure plate region 401c and receiver stack portion 102b. Matching layers 410a and 410b may have acoustic impedance selected to reduce sound wave reflections caused by acoustic impedance contrast between receiver stack portion 102a and one or more layers adjacent to or near matching layers 410a and 410b. According to some examples, matching layers 410a and 410b may comprise polyethylene terephthalate (PET). In some examples, adhesive layers 415a and 415b may include pressure-sensitive adhesive (PSA) material.

[0099] exist Figure 4In the example shown, the device has a thickness T1 (along the z-axis) from the top of the pressure plate to the base of the backing layers 430a and 430b, and a thickness T2 from the top of the pressure plate to the base of the light source system circuitry. In some examples, T2 may range from 2 mm to 10 mm. According to some examples, T1 may range from 1 mm to 8 mm. The thickness of the backing layers 430a and 430b may range from 3 mm to 7 mm, such as 4.5 mm, 5.0 mm, 5.5 mm, etc. Therefore, an embodiment without a backing layer can be substantially thinner than an embodiment including a backing layer.

[0100] Figure 5A , Figure 5B and Figure 5C It shows Figure 4 The illustration shows different examples of how some components of the apparatus can be arranged. As with the other figures provided herein, Figures 5A to 5C The number, type, and arrangement of the components shown are presented by way of example only. In these examples, device 100 is... Figure 1 and Figure 4 Examples of the device 100 are shown. In each of these examples, a top view of the device 100 is shown, wherein the top view is along... Figure 4 The z-axis of the coordinate system shown. In these examples, the light guide component 440c is shown as having a circular cross-section. However, in alternative examples, the light guide component 440c may have different cross-sectional shapes, such as a square cross-section, a rectangular cross-section, a hexagonal cross-section, etc.

[0101] In these examples, the outlines of receiver stack portion 102a and receiver stack portion 102b (and, in Figure 5B In the diagram, the outlines of receiver stack portions 102c to 102h are shown in dashed lines, indicating that these elements are below the outer surface 408a of the pressure plate 101. According to these examples, receiver stack portion 102a resides near a first side of the light guide assembly 440c, and receiver stack portion 102b resides near a second side of the light guide assembly 440c. In these examples, receiver stack portion 102a resides near its pressure plate region 102b on the first side of the pressure plate region 102a (in this example, below it along the z-axis further away from the viewer), and receiver stack portion 102b resides near its pressure plate region 102c on the opposite second side of the pressure plate region 102a.

[0102] according to Figure 5A In the example shown, receiver stack portion 102a and receiver stack portion 102b are discrete components of a linear receiver stack portion array having N receiver elements, where N is 2 in this case. In an alternative example, N may be greater than 2.

[0103] exist Figure 5B In the example shown, receiver stack portion 102a and receiver stack portion 102b are discrete components of a two-dimensional receiver array having M receiver elements, where M is 9 in this case. In an alternative example, M may be greater than or less than 9.

[0104] according to Figure 5C In the example shown, receiver stack portions 102a and 102b are portions of receiver stack ring 305a. In this example, receiver stack ring 305a is configured to surround light guide assembly 440c. According to this example, an annular region of pressure plate 301 adjacent to receiver stack ring 305a (in this example, above along the z-axis closer to the viewer), this annular region includes pressure plate regions 401b and 401c, which are configured to surround pressure plate region 401a.

[0105] Figure 5D The diagram shows the arrangement of additional components. Figure 4 Examples of components of the apparatus shown. As with the other figures provided herein, Figure 5D The number, type, and arrangement of the components shown are presented by way of example only. In these examples, device 100 is... Figure 1 An example of device 100 is shown. In this example, a top view of device 100 is shown, wherein the top view is along... Figure 4 The z-axis of the coordinate system shown. In this example, the light guide component 440c is shown as having a circular cross-section. However, in alternative examples, the light guide component 440c may have a different cross-sectional shape.

[0106] In this example, receiver stack portions 102a and 102b are portions of receiver stack ring 305a. According to this example, receiver stack ring 305a is configured to surround the light guide assembly 440c. In this example, receiver stack ring 305a includes receiver stack portions 102a and 102b, and pressure plate regions 401b and 401c. According to this example, receiver stack ring 305b is configured to surround receiver stack ring 305a. In this example, receiver stack ring 305b includes receiver stack portions 102c and 102d, and pressure plate regions 401j and 401k.

[0107] Figure 6 Example components of a device according to some alternative embodiments are shown. As with the other figures provided herein, Figure 6 The number, type, and arrangement of the components shown are presented by way of example only. In this example, device 100 is... Figure 1An example of device 100 is shown. According to this example, device 100 includes a pressure plate 101, a receiver system 102, and a light source system 104. In this example, the outer surface 408a of the pressure plate 101 is configured to receive a target object, which in this example is a finger 355.

[0108] Figure 6 The device 100 shown is basically similar to Figure 4 The apparatus 100 shown and described above. Therefore, Figure 6 In and Figure 4 Detailed descriptions of the corresponding components will not be repeated here. Instead, this discussion will focus on... Figure 4 Device 100 and Figure 6 The differences between the devices 100.

[0109] According to this example, backing layers 430a and 430b are not as good as Figure 4 The electrode layers 422a and 422b extend to the base of the light source system circuits 445a and 445b, as shown. Conversely, the backing layers 430a and 430b are only adjacent to portions of the light guide components 440a and 440b and do not extend to the light-emitting components 435a and 435b or the light source system circuits 445a and 445b. In some examples, the backing layers 430a and 430b may be portions of a continuous structure (such as a ring structure) surrounding portions of the light guide components 440a and 440b.

[0110] Furthermore, in this example, device 100 includes noise reduction elements 610a and 610b. Noise reduction elements 610a and 610b are referenced. Figure 1 An example of the noise reduction system 110 described. One type of noise that may be present in device 100 is electromagnetic interference (EMI) from light source system circuits 445a and 445b, which can be received by receiver system 102. In some specific embodiments, at least a portion of noise reduction elements 610a and 610b may include EMI suppression material.

[0111] In this example, noise reduction elements 610a and 610b extend from outer surface 408a to the base of light source system circuits 445a and 445b. According to some alternative examples, noise reduction elements 610a and 610b extend from the base of pressure plate 101 to the base of light source system circuits 445a and 445b. In some examples, noise reduction elements 610a and 610b may be part of a continuous structure (such as a ring structure). In some such examples, noise reduction elements 610a and 610b may be part of a continuous structure surrounding all layers from pressure plate 101 to light source system circuits 445a and 445b, or from mirrors 405a and 405b to all layers of light source system circuits 445a and 445b.

[0112] Figure 7 Example components of a device according to some alternative embodiments are shown. As with the other figures provided herein, Figure 7 The number, type, and arrangement of the components shown are presented by way of example only. In this example, device 100 is... Figure 1 An example of device 100 is shown. According to this example, device 100 includes a pressure plate 101, a receiver system 102, and a light source system 104. In this example, the outer surface 408a of the pressure plate 101 is configured to receive a target object, which in this example is a finger 355.

[0113] Figure 7 The device 100 shown is basically similar to Figure 6 The apparatus 100 shown and described above. Figure 7 The device 100 shown also includes a... Figure 3 Light guiding elements 310a, 310b, and 310c are similar to light guiding elements. Therefore, Figure 7 In and Figure 3 and Figure 6 Detailed descriptions of the corresponding components will not be repeated here. Instead, this discussion will focus on... Figure 3 and Figure 6 Device 100 and Figure 7 The differences between the devices 100.

[0114] According to this example, the light source system 104 includes Figure 6 The light guide assembly 440c is included, but light guide assemblies 440a and 440b are not included. In this example, light 450a and 450b from light-emitting elements 735a and 735b, respectively, are guided toward the pressure plate 101 by light guiding elements 710a, 710b, and 710c. According to this example, light guiding elements 710a, 710b, and 710c are a mirror, a lens, and a beam splitter, respectively. In this example, the light source system 104 is configured to guide light 450a and 450b toward the pressure plate 101 along an axis 715 that is perpendicular to the pressure plate 101 and parallel to the long axis of the light guide assembly 440c, which in this case corresponds to the z-axis.

[0115] Moreover, with Figure 3 Unlike the example shown, receiver system 102 receives at least some sound waves generated by light 450a and 450b along an axis parallel to or substantially parallel to the axis along which light 450a and 450b are transmitted, which in this example is Figure 7 Axis 715. In this context, "substantially parallel" to axis 715 can mean ±5 degrees, ±10 degrees, ±15 degrees, ±20 degrees, etc.

[0116] and Figure 6The noise reduction elements 610a and 610b are the same, while the noise reduction elements 710a and 710b are reference. Figure 1 An example of the noise reduction system 110 described. However, according to this example, noise reduction elements 710a and 710b are... Figure 6 The noise reduction elements 610a and 610b are configured in different ways. Figure 7 In the example shown, noise reduction elements 710a and 710b do not extend to the base of light source system circuits 445a and 445b and do not surround light source system circuits 445a and 445b or light-emitting elements 735a and 735b. Furthermore, in Figure 7 In the example shown, portions of noise reduction elements 710a and 710b extend between backing layers 430a and 430b and at least some portions of the light source system 104. As mentioned elsewhere herein, in some cases, backing layers 430a and 430b may be portions of a continuous structure (such as a ring structure) surrounding the light guide assembly 440c. In some such examples, portions of noise reduction elements 710a and 710b may extend within a continuous structure (such as a ring structure) between backing layers 430a and 430b and at least some portions of the light source system 104.

[0117] Figure 8A and Figure 8B Example components of a device according to some alternative embodiments are shown. As with the other figures provided herein, Figure 8A and Figure 8B The number, type, and arrangement of the components shown are presented by way of example only. In these examples, device 100 is... Figure 1 Examples of the apparatus 100 are shown. According to these examples, the apparatus 100 includes a pressure plate 101, a receiver system 102, and a light source system 104. In these examples, the outer surface of the pressure plate 101 is configured to receive a target object, which in these examples is a wrist 805 including a radial artery 807.

[0118] Figure 8A and Figure 8B The example shown is the same as Figure 4 The apparatus 100 shown and described above has some similarities. For example, Figure 8A and Figure 8B The examples shown include those with Figure 4 The light guide assemblies 440a, 440b, and 440c have similar functions to the light guide assemblies 840a, 840b, and 840c: Like the light guide assemblies 440a, 440b, and 440c, the light guide assemblies 840a, 840b, and 840c are configured to guide light from the light-emitting elements 835a and 835b (VCSELs in this example) toward at least a portion of the outer surface 408a of the pressure plate 101. However, in Figure 8A and Figure 8B In the examples shown, the shapes and proportions of the light guide components 840a, 840b, and 840c are similar to... Figure 4 The optical guide components 440a, 440b, and 440c differ somewhat. For example, Figure 4 The optical guide component 440c has a uniform or substantially uniform width (such as ±1%, ±3%, ±5%, etc.) when measured in the x-direction; however, Figure 8A and Figure 8B The width of the light guide component 840c increases from the first side adjacent to the light guide components 840a and 840b to the second side adjacent to the backing layer 430. In these examples, the width of the light guide component 840c on the second side adjacent to the backing layer 430 (at least along the x-axis) is equal to the width of the backing layer 430.

[0119] According to these examples, both the backing layer 430 and the piezoelectric material 415 are transparent. In some such examples, the transparent backing layer 430 may comprise transparent beads, such as glass beads (e.g., spherical beads, other transparent bead shapes, or combinations thereof), within a transparent epoxy resin. According to some examples, the transparent piezoelectric material 415 may comprise PVDF. In some examples, the light source system 104 may be configured to provide light through the transparent backing layer 430 and the transparent piezoelectric material 415 to all or substantially all (e.g., at least 75%, at least 80%, at least 85%, at least 90%, etc.) of the outer surface 408a of the pressure plate 101.

[0120] exist Figure 8A and Figure 8B In the example shown, the receiver system circuit 802 resides below the light source system 104 (in other words, at a greater distance along the -z direction). This physical separation between the receiver system circuit 802 and the piezoelectric material 415 may result in relatively less EMI reaching the piezoelectric material 415 compared to a specific implementation where the receiver system circuit 802 resides closer to the piezoelectric material 415.

[0121] exist Figure 8B In the example shown, the device includes a transparent electrode array 820 residing between a transparent piezoelectric material 415 and a pressure plate 101. In some examples, the transparent electrode array 820 may include indium tin oxide (ITO), a broad-spectrum transparent conductive oxide (TCO), a conductive polymer, or a combination thereof. According to some examples, the transparent electrode array 820 may include a linear array. Alternatively or additionally, in some examples, the transparent electrode array 820 may include a two-dimensional array.

[0122] Figure 9A , Figure 9B and Figure 9C Example components of a device according to some alternative specific implementations are shown. As with other figures provided herein, Figures 9A to 9C The number, type, and arrangement of the components shown are presented by way of example only. In these examples, device 100 is... Figure 1 Examples of the apparatus 100 are shown. According to these examples, the apparatus 100 includes a pressure plate 101, a receiver system 102, and a light source system 104. In these examples, the outer surface of the pressure plate 101 is configured to receive a target object, which in these examples is a wrist 805 including a radial artery 807.

[0123] exist Figures 9A to 9C In the examples shown, the light guide system 104 includes a light guide 904 configured to guide light 950a and 950b from light-emitting elements 935a and 935b, respectively, in a direction parallel to or substantially parallel to the pressure plate 101. According to these examples, light-emitting element 935a is configured to emit light with a peak amplitude at a first wavelength, and light-emitting element 935b is configured to emit light with a peak amplitude at a second wavelength. In these examples, the light guide system 104 is configured to guide light 950a and 950b substantially along an x-axis, which in these examples is oriented parallel to the outer surface 408a of the pressure plate 101. In this context, "substantially parallel" can mean within 5 degrees of parallelism, within 10 degrees of parallelism, within 15 degrees of parallelism, within 20 degrees of parallelism, etc.

[0124] According to some examples, light-emitting elements 935a, 935b, or both may be positioned on different sides of device 100, such as opposite or adjacent sides. In some examples, light-emitting element 935a may reside on one side of device 100, and light-emitting element 935b may reside on the other side of device 100. In some examples, both light-emitting elements 935a and 935b may reside on two or more sides of device 100. According to some examples, light-emitting elements 935a and 935b may be positioned as follows: Figure 10B The arrangement is shown.

[0125] According to these examples, the light guide system 104 includes a plurality of light extraction elements 910 residing within the light guide 904. In these examples, the light extraction elements 910 are configured to guide light exiting the light guide 904 toward the pressure plate 101. In some specific implementations, the light extraction elements 910 may be or may include beam splitters, mirrors, or other reflective structures, etc. Figure 9A and Figure 9BIn the example shown, the light extraction element 910 includes a beam splitter. Alternatively or additionally, in some embodiments, the light extraction element 910 may be or may include one or more recesses in the light guide surface, one or more protrusions in the light guide surface, or one or more structures formed on the light guide surface. In some such examples, the light extraction element 910 may be or may include one or more three-dimensional shapes formed by recesses in the light guide surface, protrusions in the light guide surface, or structures formed on the light guide surface.

[0126] exist Figure 9C In the example shown, the light extraction element 910 includes a reflective structure formed on the light guide surface 977. According to this example, when viewed in a cross-section on the xz plane, the reflective structure is triangular, as shown... Figure 9C As shown. However, in alternative embodiments, the reflective structure may have other shapes.

[0127] according to Figure 9C In the example shown, light extraction elements 910 are arranged within the light guide 904 at unequal intervals. In this example, light extraction elements 910 located farther from the light-emitting devices 935a and 935b can be spaced closer to each other than light extraction elements 910 located closer to the light-emitting devices 935a and 935b. Compared to a specific implementation where the same light extraction elements 910 are equally spaced, spacing the light extraction elements 910 farther from the light source more than those closer to the light source can provide relatively uniform illumination to the outer surface of the pressure plate 101 and the target object in contact with that surface. In some other implementations, relatively uniform illumination of the outer surface of the pressure plate 101 can be achieved by including light extraction elements 910 farther from the light source that are configured to extract relatively more light than those closer to the light source (e.g., by providing a relatively larger reflective structure farther from the light source).

[0128] According to some examples, a two-dimensional array of light extraction elements 910 can provide light to all or substantially all (such as at least 75%, at least 80%, at least 95%, at least 90%, etc.) of the outer surface 408a of the pressure plate 101. In some such examples, the two-dimensional array of light extraction elements 910 can provide substantially uniform light to the illumination area of ​​the outer surface 408a of the pressure plate 101. In this context, "substantially uniform" may mean ±5% of the peak amplitude, ±10% of the peak amplitude, ±15% of the peak amplitude, ±20% of the peak amplitude, etc. In some examples, the light extraction element 910 may be as described in U.S. Patent No. 8,545,084. Figures 1 to 6 As shown in A and as referenced Figures 1 to 6 The arrangement described in A is incorporated herein by reference for all purposes.

[0129] according to Figures 9A to 9C In the example shown, both the backing layer 430 and the piezoelectric material 415 are transparent. In some examples, the backing layer 430 and the piezoelectric material 415 may be as described in the reference. Figure 8A and Figure 8B As described above.

[0130] exist Figures 9A to 9C In the example shown, the receiver system circuit 802 resides below the light source system 104 (in other words, further away from the light source system along the -z direction). Compared to a specific implementation where the receiver system circuit 802 resides closer to the piezoelectric material 415, this physical separation between the receiver system circuit 802 and the piezoelectric material 415 may result in relatively less EMI reaching the piezoelectric material 415, which is potentially advantageous.

[0131] exist Figure 9B and Figure 9C In the example shown, device 100 includes a transparent electrode array 820 residing between a transparent piezoelectric material 415 and a pressure plate 101. In some examples, the transparent electrode array 820 may include indium tin oxide (ITO), a broad-spectrum transparent conductive oxide (TCO), a conductive polymer, or a combination thereof. According to some examples, the transparent electrode array 820 may include a linear array. Alternatively or additionally, in some examples, the transparent electrode array 820 may include a two-dimensional array.

[0132] Figure 10A and Figure 10B Example components of a device according to some alternative embodiments are shown. As with the other figures provided herein, Figure 10A and Figure 10B The number, type, and arrangement of the components shown are presented by way of example only. In these examples, device 100 is... Figure 1 Examples of apparatus 100 are shown. According to these examples, apparatus 100 includes a transparent pressure plate 101, a receiver system 102, and a light source system 104, although the elements of the light source system 104 are... Figure 10A It is not visible in the middle.

[0133] according to Figure 10A and Figure 10B In the example shown, backing layer 430 (if present) is transparent. Figure 10A and Figure 10B In the example shown, receiver system 102 includes a transparent piezoelectric layer 415 and a two-dimensional transparent electrode array 820, which together form a two-dimensional receiver element array.

[0134] Specific implementations including receiver element arrays (including, but not limited to, implementations including two-dimensional receiver element arrays) have various potential advantages. One advantage is that prior knowledge of the precise location of the target of interest (such as blood vessels) may not be required before obtaining ultrasound or photoacoustic data from the target object. Some receiver elements in the array can be positioned close to the target of interest, while others can be positioned far from it. Some receiver elements may receive relatively strong signals from the target of interest, some may receive relatively weak signals, and others may receive such weak signals from the target of interest at levels no higher than the background noise level. Nevertheless, at least some receiver elements can receive sufficiently strong signals from the target of interest by adding the signals received from multiple receiver elements, and the device 100 can provide a clear image of the target of interest.

[0135] according to Figure 10B In the example shown, light-emitting element 1035a resides on a first side of device 100, and light-emitting element 1035b resides on a second side of device 100, which in this case is an adjacent side. In some alternative examples, the second side may be an opposite side. In some examples, both light-emitting element 935a and light-emitting element 935b may reside on two or more sides of device 100.

[0136] exist Figure 10B In the example shown, the light guide system 104 includes a light guide (not shown) configured to guide light from light-emitting elements 1035a and 1035b, respectively, in a direction parallel to or substantially parallel to the pressure plate 101. In some such examples, the light guide may reside beneath the transparent piezoelectric layer 415, for example, as... Figures 9A to 9C As shown.

[0137] according to Figure 10B In the example shown, the light guide system 104 includes a plurality of light extraction elements (not shown) residing within the light guide. In these examples, the light extraction elements are configured to direct light leaving the light guide toward the pressure plate 101. In some specific embodiments, the light extraction elements may be or may include beam splitters, mirrors, or other reflective structures, etc.

[0138] According to some examples, a two-dimensional array of light extraction elements can provide light to all or substantially all of the outer surfaces 408a of the pressure plate 101. In some such examples, a two-dimensional array of light extraction elements 910 can provide substantially uniform light to the illumination area of ​​the outer surface 408a of the pressure plate 101.

[0139] Figure 11 This is a flowchart illustrating some examples of the disclosed operations. Figure 11 The boxes (and the boxes in other flowcharts provided herein) can be, for example, made by... Figure 1 The device 100 or a similar device performs the operation. As with other methods disclosed herein, Figure 11 The methods outlined herein may include more or fewer boxes than those shown. Furthermore, the boxes in the methods disclosed herein are not necessarily executed in the indicated order. In some cases, Figure 11 One or more boxes in the box shown can be executed concurrently.

[0140] In this example, box 1105 relates to: enabling the light source system to provide first light of a first wavelength to the target object at a first moment. In some examples, box 1105 may relate to: controlling the light source system by a control system (which may be...) Figure 1 Examples of a light source system 104 and a control system 106 are provided to emit first light of a first wavelength onto a target object on the outer surface of a pressure plate at a first moment. Depending on the specific example, the target object may be a finger, wrist, etc. The first light may be emitted, for example, through a first light-emitting element of at least the light source system configured to emit light having a peak amplitude at the first wavelength.

[0141] According to this example, block 1110 relates to receiving a first ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the first light. In some examples, block 1110 may relate to receiving, via control system 106, a signal from receiver system 102 corresponding to the ultrasonic waves generated by the target object in response to the first light.

[0142] In this example, block 1115 relates to: providing a second wavelength of light to a target object by a light source system at a second time. The second light may be emitted, for example, by a second light-emitting element of the light source system configured to emit light having a peak amplitude at the second wavelength. In some examples, block 1115 may relate to: controlling the light source system 104 by a control system 106 to emit second wavelength of light to the target object at a second time.

[0143] According to this example, block 1120 relates to receiving a second ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the second light. In some examples, block 1120 may relate to the control system 106 receiving a signal from the receiver system 102 corresponding to the ultrasonic waves generated by the target object in response to the second light.

[0144] In this example, block 1125 relates to distinguishing a desired signal from one or more background signals, at least in part, based on signals from a first ultrasound receiver and a second ultrasound receiver. According to some examples, block 1125 may be executed by control system 106. In some examples, the desired signal may correspond to a blood vessel within the target object. In some examples, method 1100 may relate to estimating one or more vascular features based on at least one of the first or second ultrasound receiver signals. One or more vascular features may include, for example, vessel diameter, vessel area, vessel profile, vessel dilation, volumetric flow rate, pulse wave velocity, vessel wall thickness, or combinations thereof.

[0145] According to some examples, method 1100 may involve estimating blood pressure based at least in part on one or more vascular features. In some examples, method 1100 may involve extracting and estimating heart rate waveform (HRW) features that may be based at least in part on one or more vascular features.

[0146] Figure 12 It shows that it can be based on Figure 11 Examples of specific implementations of the method for extracting heart rate waveform (HRW) features. Figure 12 The horizontal axis 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 cardiac circulation, as the pulse travels along the artery through a specific location, the arterial wall expands according to the pulse waveform and the elastic properties of the arterial wall. Accompanying this expansion is a corresponding increase in blood volume at the specific location or region, and with the increase in blood volume, one or more properties in that region change accordingly. Conversely, during the diastolic phase of cardiac circulation, blood pressure in the artery decreases and the arterial wall constricts. Accompanying this constriction is a corresponding decrease in blood volume at the specific location, and with the decrease in blood volume, one or more properties in that region change accordingly.

[0147] Figure 12The illustrated HRW features represent the width of the contraction and / or diastolic portions of the HRW curve at different "heights," expressed as a percentage of the maximum amplitude. For example, the SW50 feature is the width of the contraction portion of the HRW curve at a "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 cases, 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 implementations may use additional HRW features for blood pressure estimation. In some cases, such additional HRW features may include sums, differences, ratios, and / or other calculations based on more than one “height,” such as (DW75 + SW75) / (DW50 + SW50), (DW50 + SW50 / (DW10 + SW10), etc.

[0148] 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. The number, type, and arrangement of elements are presented by way of example only, as shown in the other figures provided herein. 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 a finger of a person 1301. In this example, device 1310 is or includes means configured to perform at least some of the PAPG methods disclosed herein. For example, device 1310 may be or may include Figure 1 The device 300 or similar device.

[0149] As mentioned in Figure 1320, PAT comprises two components: pre-ejection phase (PEP, the time required to convert the electrical signal into 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 characteristics of ventricular electrical stimulation). As shown in Figure 1320, in this example, the start of the pulse arrival time (PAT) can be calculated based on the R wave peak measured by the ECG sensor 1305, and the end of PAT can be detected by analysis of the signal provided by the device 1310. In this example, it is assumed that the end of PAT corresponds to the intersection of 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 that minimum.

[0150] There are many known blood pressure estimation algorithms 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 Sharma, M. et al.’s “Cuff-Less and Continuous Blood Pressure Monitoring: A Methodological Review (“Sharma”)” (published in Technologies, Vol. 5, No. 21, 2017, Multidisciplinary Digital Publishing Institute (MDPI), which is incorporated herein by reference.

[0151] 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 in Sharma's Table 1 or other known equations. As mentioned above, some disclosed embodiments with PAPG capability are configured to distinguish arterial HRW from other HRWs. Such embodiments provide more accurate PTT and / or PAT measurements compared to those measured by a PPG sensor. Therefore, the disclosed embodiments with PAPG capability can provide more accurate blood pressure estimates, even when the blood pressure estimate is based on previously known formulas.

[0152] Other embodiments of system 1300 may not include electrocardiogram sensor 1305. In some such embodiments, device 1315, configured to be mounted on the wrist of person 1301, may be or may include means configured to perform at least some of the PAPG methods disclosed herein. For example, device 1315 may be or may include device 200 of FIG2 or similar means. According to some such examples, device 1315 may include a light source system and two or more ultrasound receivers. Reference is made below. Figure 15A Describe an example. In some examples, device 1315 may include an array of ultrasonic receivers.

[0153] In some specific embodiments of system 1300 excluding electrocardiogram sensor 1305, device 1310 may include a light source system and two or more ultrasound receivers. See below for reference. Figure 15B An example is described.

[0154] Figure 14 A cross-sectional side view of a schematic diagram showing a portion of the artery 1400 through which a pulse 1402 propagates. Figure 14 The boxed arrows indicate the direction of blood flow and pulse propagation. As illustrated, the propagating pulse 1402 causes strain in the arterial wall 1404, which manifests as an increase in the diameter (and therefore the cross-sectional area) of the arterial wall, referred to as "dilation." The spatial length of the actual propagating pulse along the artery (along the direction of blood flow) is also shown. L It is usually comparable to the length of a limb, such as the distance from the subject's shoulder to their wrist or fingers, and is typically less than one meter (m). However, the length of the pulse transmission... L It can vary considerably between different subjects, and for a given subject, it may depend on various factors that vary significantly over time. Spatial length of the pulse L It usually decreases as the distance from the heart increases until the pulse reaches the capillaries.

[0155] As described above, certain specific implementations involve devices, systems, and methods for estimating blood pressure or other cardiovascular characteristics based on estimations of arterial dilation waveforms. Unless otherwise indicated, the terms “estimate,” “measure,” “calculate,” “infer,” “derive,” “evaluate,” “determine,” and “monitor” are used interchangeably herein where appropriate. Similarly, derivatives of the roots of these terms are also used interchangeably where appropriate; for example, the terms “estimate,” “measure,” “calculate,” “infer,” and “determine” are also used interchangeably herein. In some implementations, the pulse wave velocity (PWV) of the propagating pulse can be estimated by measuring its pulse transit time (PTT) as the pulse travels from a first physical location along the artery to a second physical location further distal along the artery. It should be understood that this PTT differs from the PTT described above with reference to Figure 15. However, either version of the PTT can be used for the purpose of blood pressure estimation. The physical distance between the first and second physical locations is assumed. It is deterministic; PWV can be estimated as the physical spatial distance traveled by the pulse. Divide by the distance the pulse travels across that physical space The time taken (PTT) is the quotient of the time elapsed. Generally, a first sensor located at a first physical location is used to determine the start time of the pulse's arrival at that point or its propagation 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 of the pulse's arrival at that point or its propagation through the second physical location and its continuation through the rest of the arterial branch (also referred to herein as the "second time location"). In such examples, PTT represents the time distance (or time difference) between the first time location and the second time location (start time and end time).

[0156] The fact that arterial dilation waveforms are measured at two different physical locations implies that the estimated PWV inevitably represents the total path distance of the pulse propagation between the first and second physical locations. The average value is calculated based on the mean. More specifically, PWV typically depends on several factors, including blood density. The stiffness of the arterial wall (or conversely, elasticity), arterial diameter, arterial wall thickness, and blood pressure. Because both 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 a PTT measurement is essentially an average (the total path length between the two locations where the measurement was performed). (Above average).

[0157] In conventional methods for acquiring pulse wave velocity (PWV), electrocardiogram (ECG) sensors (which detect electrical signals from the heart) have been used to obtain the onset time of the pulse at the heart. For example, the onset time can be estimated based on the QRS complex (the electrical signal characteristics of ventricular electrical stimulation). In such methods, different sensors positioned at a second location (e.g., the finger) are typically used to obtain the end time of the pulse. As those skilled in the art will understand, there are many arterial discontinuities, branches, and variations along the entire path from the heart to the finger. PWV variations can reach or exceed one order of magnitude along various extensions of the entire path from the heart to the finger. Thus, PWV estimations based on such a long path length are unreliable.

[0158] In the various specific embodiments described herein, PPT estimation is obtained based on measurements associated with an arterial dilation signal (also referred to as "arterial dilation data" or more commonly "sensor data"), obtained by each of a first arterial dilation sensor 1406 and a second arterial dilation sensor 1408, respectively, approaching a first physical location and a second physical location along the artery of interest. In some specific embodiments, the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408 are advantageously positioned near the first and second physical locations, allowing the arterial properties (such as wall elasticity and diameter) of the artery of interest between the first and second physical locations to be considered or assumed to be relatively constant. In this way, the PWV calculated based on the PTT estimation is more representative of the actual PWV along a specific segment of the artery. Subsequently, the blood pressure is estimated based on the PWV. This provides a more accurate representation of actual blood pressure. In some specific implementations, the separation distance between the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408... The magnitude of the pulse (and therefore the distance between the first and second positions along the artery) can range from about 1 centimeter (cm) to tens of centimeters, long enough to distinguish the arrival of the pulse at the first physical position from the arrival of the pulse at the second physical position, but close enough to provide sufficient assurance of arterial consistency. In some specific embodiments, the distance between the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408... The distance can be in the range of approximately 1 cm to approximately 30 cm, and in some embodiments, less than or equal to approximately 20 cm, and in some embodiments, less than or equal to approximately 10 cm, and in some embodiments, less than or equal to approximately 5 cm. In some other embodiments, the distance between the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408... The pulse width (PWV) 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. For reference, a typical PWV can be about 15 m / s. Using a non-asylum monitoring device with a first arterial dilation sensor 1406 and a second arterial dilation 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 ms.

[0159] The distance between the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408 The values ​​of the quantities can be pre-programmed into the memory within the monitoring device that integrates the sensors (e.g., reference memory). Figure 1 The pulse is stored in the memory of the control system 306 described above, or in a memory configured to communicate with the control system. As will be understood by those skilled in the art, in such embodiments, the spatial length of the pulse... L It 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 illustrated pulse 1402 is shown to have a spatial length equivalent to the distance between the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408. L In reality, each pulse can generally have a distance greater than, and even much greater than (e.g., about an order of magnitude or more) the distance between the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408. Spatial length L .

[0160] Sensing architecture and topology

[0161] In some embodiments of the non-bedridden 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 identical sensors. In such embodiments, each of the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408 utilizes the same sensor technology with 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, for example, photoacoustic plethysmography (PAPG) sensing as disclosed elsewhere herein. Some such embodiments include a light source system and two or more ultrasound receivers, which may be... Figure 1Examples of a light source system 104 and a 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 via the transmission of an ultrasonic signal and the reception of a corresponding reflection. 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 in a biomedical context as bioimpedance sensing. In various embodiments, regardless of the type of sensor used, each of the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408 functions broadly to capture and provide arterial dilation data indicating an arterial dilation signal generated by the propagation of a pulse through an artery adjacent to a portion of which the respective sensor is located. For example, the arterial dilation data may be provided from the sensor to the processor 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.

[0162] As described above, during the systolic phase of cardiac circulation, as the pulse travels along the arteries through a specific location, the arterial walls expand according to the pulse waveform and the elastic properties of the arterial walls. This expansion is accompanied by a corresponding increase in blood volume at that specific location or region, and with this increase in blood volume, one or more properties in that region change accordingly. Conversely, during the diastolic phase of cardiac circulation, blood pressure in the arteries decreases and the arterial walls constrict. This constriction is accompanied by a corresponding decrease in blood volume at that specific location, and with this decrease in blood volume, one or more properties in that region change accordingly.

[0163] In the context of bioimpedance sensing (or impedance plethysmography), blood in an artery has a higher conductivity than surrounding or adjacent skin, muscle, fat, tendons, ligaments, bone, lymph, or other tissues. The susceptivity (and therefore the dielectric constant) of blood also differs from that of other types of surrounding or nearby tissues. As a pulse propagates through a particular location, the corresponding increase in blood volume results in an increase in conductivity (and more generally, an increase in admittance, or equivalently, a decrease in impedance) at that location. Conversely, during the diastolic phase of cardiac circulation, the corresponding decrease in blood volume results in an increase in resistivity (and more generally, an increase in impedance, or equivalently, a decrease in admittance) at that location.

[0164] Bioimpedance sensors typically function by applying an electrically excited signal at an excitation carrier frequency to a region of interest via two or more input electrodes and detecting an output signal (or multiple output signals) via two or more output electrodes. In some more specific embodiments, the electrically excited 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 representing the voltage response of tissue in the region of interest to the applied excitation signal. The detected voltage response signal is influenced by the different (and in some cases time-varying) electrical properties of the various tissues through which the injected excitation current signal passes. In some embodiments where the bioimpedance sensor can be operated 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 artery, as described above, which fluctuates in sync with the user's heartbeat. To determine various biological characteristics, information from 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.

[0165] In some examples of incorporating ultrasound sensors, the measurement of arterial dilation may involve, for example, guiding ultrasound waves into the limb toward the artery via one or more ultrasound transducers. Such ultrasound sensors are also configured to receive reflected waves, at least in part based on the guided waves. The reflected waves may include scattered waves, specular reflections, or both. The reflected waves provide information about the arterial wall and, therefore, information about arterial dilation.

[0166] In some specific implementations, regardless of the type of sensor used for the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408, both the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408 may be arranged, assembled, or otherwise included within a single housing of a single ambulatory monitoring device. As described above, the housing and other components of the monitoring device may be configured such that when the monitoring device is fixed or otherwise physically coupled to a subject, both the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408 are respectively positioned at a distance... The separate first and second positions are in contact with or adjacent to the user's skin, and in some embodiments, it may be assumed that the various arterial properties along the arterial extension between the first and second positions are relatively constant. In various embodiments, the housing of the non-motorized monitoring device is a wearable housing or incorporated into or integrated with a wearable housing. In some embodiments, the wearable housing includes (or is connected to) a physical coupling mechanism for detachable, non-invasive attachment to the user. The housing can be formed using any of a variety of suitable manufacturing processes, including injection molding and vacuum forming. Additionally, the housing can be made from any 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 certain embodiments, the housing and coupling mechanism enable fully non-motorized use. In other words, some embodiments of the wearable monitoring device described herein are non-invasive, non-physically inhibiting, and generally do not restrict the free and uninhibited movement of the subject's arms or legs, enabling continuous or periodic monitoring of cardiovascular characteristics (such as blood pressure) even when the subject is moving or otherwise engaging in physical activity. Thus, non-bedridden monitoring devices facilitate and enable long-term wear and monitoring (e.g., uninterrupted for days, weeks, or a month or more) of one or more biological characteristics of interest to obtain a better picture of such characteristics over the extended duration, and generally, a better picture of the user's health.

[0167] In some implementations, non-bedridden monitoring devices can be positioned around the user's wrist using a strip or band, similar to a watch or fitness / activity tracker. Figure 15A An example of a non-bedridden monitoring device 1500 designed to be worn on the wrist is shown according to some specific embodiments. In the illustrated example, the monitoring device 1500 includes a housing 1502 integrally formed, coupled, or otherwise integrated with a wristband 1504. In some cases, a first arterial dilation sensor 1506 and a second arterial dilation sensor 1508 may each include a reference... Figure 1 This is an example of the ultrasound receiver system 102 described above and a part of the light source system 104. In this example, the non-motorized monitoring device 1500 is coupled around the wrist, such that a first arterial dilation sensor 1506 and a second arterial dilation sensor 1508 within the housing 1502 are each positioned along a segment of the radial artery 1510 (note that when the monitoring device is coupled to the subject, the sensors are typically concealed when viewed from the subject-facing external or outer surface of the housing, but exposed on the inner surface of the housing so that the sensors can obtain measurements from the artery beneath through the subject's skin). Also as shown, the first arterial dilation sensor 1506 and the second arterial dilation sensor 1508 are positioned at a fixed distance. Separately. In some other specific implementations, the non-bedridden monitoring device 1500 may similarly be designed or adapted for positioning using strips or bands around the forearm, upper arm, ankle, lower leg, thigh, or fingers (all of which are referred to below as "limbs").

[0168] Figure 15B An example of a non-bedridden monitoring device 1500 designed to be worn on a finger is shown according to some specific embodiments. In some cases, a first arterial dilation sensor 1506 and a second arterial dilation sensor 1508 may each include the components referenced above. Figure 1 An example of the described ultrasonic receiver 102 and part of the light source system 104.

[0169] In some other embodiments, the non-bedridden monitoring device disclosed herein can be positioned on a user’s area of ​​interest without the use of strips or bands. For example, the first arterial dilation sensor 1506 and the second arterial dilation sensor 1508, along with other components of the monitoring device, can be enclosed in a housing that is secured to the user’s skin in the area of ​​interest using an adhesive or other suitable attachment mechanism (example of a “patch” monitoring device).

[0170] Figure 15C An example of a non-bedridden monitoring device 1500 designed to reside on an earplug is shown according to some specific embodiments. According to this example, the non-bedridden monitoring device 1500 is coupled to a housing of an earplug 1520. In some cases, a first arterial dilation sensor 1506 and a second arterial dilation sensor 1508 may each include a reference... Figure 1 An example of the ultrasonic receiver system 102 described above and a part of the light source system 104.

[0171] Specific implementation examples are described in the following numbered clauses: 1A. An apparatus comprising: a pressure plate; a light source system configured to provide light to a target object on an outer surface of the pressure plate, the light including at least a first wavelength of first light and a second wavelength of second light; an ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to the light from the light source system; and a control system configured to: cause the light source system to provide the first light to the target object at a first time; receive a first ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the first light; cause the light source system to provide the second light to the target object at a second time; receive a second ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the second light; and distinguish a desired signal from one or more background signals based at least in part on the first ultrasonic receiver signal and the second ultrasonic receiver signal.

[0172] 2A. The apparatus according to Clause 1A, wherein the desired signal corresponds to a blood vessel within the target object.

[0173] 3A. The apparatus according to Clause 2A, wherein the control system is further configured to estimate one or more vascular features based on at least one of the first ultrasound receiver signal or the second ultrasound receiver signal.

[0174] 4A. The device according to Clause 3A, wherein the one or more vascular features include vascular diameter, vascular area, vascular profile, vascular dilation, volumetric flow rate, pulse wave velocity, vascular wall thickness, or a combination thereof.

[0175] 5A. The apparatus according to Clause 3A or Clause 4A, wherein the control system is further configured to estimate blood pressure at least in part based on the one or more vascular features.

[0176] 6A. An apparatus according to any one of clauses 1A to 5A, wherein the light source system includes a first laser configured to emit the first light and a second laser configured to emit the second light.

[0177] 7A. The apparatus according to any one of clauses 1A to 6A, wherein the light source system further comprises a light guide system configured to deliver light from the light source system to the pressure plate.

[0178] 8A. The apparatus according to Clause 7A, wherein the first optical guide portion of the optical guide system resides between at least two ultrasonic receiver system portions.

[0179] 9A. The apparatus according to Clause 8A, wherein the light guiding system includes a second light guiding portion configured to deliver the first light to the first light guiding portion and a third light guiding portion configured to deliver the second light to the first light guiding portion.

[0180] 10A. The apparatus according to Clause 7A, wherein at least a portion of the ultrasonic receiver system is arranged as a loop around the first light guide portion.

[0181] 11A. The apparatus according to Clause 7A, wherein the light guiding system includes a light guide configured to deliver light in a direction parallel to or substantially parallel to the pressure plate.

[0182] 12A. The apparatus according to Clause 11A, wherein the light guide system includes a plurality of light extraction elements residing within the light guide, the light extraction elements being configured to direct light toward the pressure plate.

[0183] 13A. The apparatus according to any one of clauses 7A to 12A, wherein the ultrasonic receiver system comprises an array of ultrasonic receiver elements.

[0184] 14A. The apparatus according to Clause 13A, wherein the ultrasonic receiver element array comprises a linear ultrasonic receiver element array.

[0185] 15A. The apparatus according to Clause 13A, wherein the ultrasonic receiver element array comprises a two-dimensional ultrasonic receiver element array.

[0186] 16A. The apparatus according to any one of clauses 13A to 15A, wherein the array of ultrasonic receiver elements is transparent.

[0187] 17A. The apparatus according to any one of clauses 1A to 16A, wherein the ultrasonic receiver system comprises a transparent piezoelectric layer.

[0188] 18A. The apparatus according to any one of clauses 1A to 17A, wherein the ultrasonic receiver system includes a transparent electrode layer.

[0189] 19A. An apparatus according to any one of clauses 1A to 18A, wherein the light source system is configured to provide the first light to the target object along a first axis and is configured to provide the second light to the target object along the first axis.

[0190] 20A. The apparatus according to Clause 19A, wherein the ultrasonic receiver system receives sound waves from the target object along a second axis different from the first axis, the sound waves corresponding to the first ultrasonic receiver signal and the second ultrasonic receiver signal.

[0191] 21A. The apparatus according to Clause 20A, wherein the second axis is separated from the first axis at an angle ranging from 10 degrees to 60 degrees.

[0192] 22A. A method comprising: providing a first wavelength of light to a target object at a first time using a light source system; receiving a first ultrasonic receiver signal from an ultrasonic receiver system corresponding to a photoacoustic response of the target object to the first light; providing a second wavelength of light to the target object at a second time using the light source system; receiving a second ultrasonic receiver signal from the ultrasonic receiver system corresponding to a photoacoustic response of the target object to the second light; and distinguishing a desired signal from one or more background signals based at least in part on the first ultrasonic receiver signal and the second ultrasonic receiver signal.

[0193] 23A. The method according to Clause 22A, wherein the desired signal corresponds to a blood vessel within the target object.

[0194] 24A. The method according to Clause 23, further comprising: estimating one or more vascular features based on at least one of the first ultrasound receiver signal or the second ultrasound receiver signal.

[0195] 25A. The method according to Clause 24A, wherein the one or more vascular features include vascular diameter, vascular area, vascular profile, vascular dilation, volumetric flow rate, pulse wave velocity, vascular wall thickness, or a combination thereof.

[0196] 26A. The method according to Clause 24A or Clause 25A, the method further comprising estimating blood pressure based at least in part on the one or more vascular features.

[0197] 27A. One or more non-transitory computer-readable media having instructions stored thereon for performing a method, the method comprising: causing a light source system to provide first light of a first wavelength to a target object at a first time; receiving a first ultrasonic receiver signal from an ultrasonic receiver system corresponding to a photoacoustic response of the target object to the first light; causing the light source system to provide second light of a second wavelength to the target object at a second time; receiving a second ultrasonic receiver signal from the ultrasonic receiver system corresponding to a photoacoustic response of the target object to the second light; and distinguishing a desired signal from one or more background signals based at least in part on the first ultrasonic receiver signal and the second ultrasonic receiver signal.

[0198] 28A. One or more non-transitory computer-readable media as described in Clause 27A, wherein the desired signal corresponds to a blood vessel within the target object, and wherein the method further comprises: estimating one or more blood vessel features based on at least one of the first ultrasound receiver signal or the second ultrasound receiver signal.

[0199] 29A. One or more non-transitory computer-readable media as described in Clause 28A, wherein the one or more vascular features include vascular diameter, vascular area, vascular profile, vascular dilation, volumetric flow rate, pulse wave velocity, vascular wall thickness, or combinations thereof.

[0200] 30A. One or more non-transitory computer-readable media as described in Clause 28A or Clause 29A, wherein the method further comprises estimating blood pressure based at least in part on the one or more vascular features.

[0201] 1B. An apparatus comprising: a pressure plate; a light source system configured to provide light to a target object on an outer surface of the pressure plate, the light comprising at least a first light of a first wavelength emitted by a first light-emitting device and a second light of a second wavelength emitted by a second light-emitting device, the light source system being configured to provide the first light to the target object along a first axis and to provide the second light to the target object along the first axis; an ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to the light from the light source system; and a control system configured to: cause the light source system to provide the first light to the target object at a first time; receive a first ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the first light; cause the light source system to provide the second light to the target object at a second time; receive a second ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the second light; and estimate one or more vascular features based on at least one of the first ultrasonic receiver signal or the second ultrasonic receiver signal.

[0202] 2B. The apparatus according to Clause 1B, wherein the control system is further configured to distinguish the desired signal from one or more background signals based at least in part on the first ultrasonic receiver signal and the second ultrasonic receiver signal.

[0203] 3B. The apparatus according to Clause 2B, wherein the desired signal corresponds to a blood vessel within the target object.

[0204] 4B. The device according to any one of clauses 1B to 3B, wherein the one or more vascular features include vascular diameter, vascular area, vascular profile, vascular dilation, volumetric flow rate, pulse wave velocity, vascular wall thickness, or a combination thereof.

[0205] 5B. The apparatus according to any one of clauses 1B to 4B, wherein the control system is further configured to estimate blood pressure at least in part based on the one or more vascular features.

[0206] 6B. The apparatus according to any one of clauses 1B to 5B, wherein the first light-emitting device includes a first laser configured to emit the first light, and wherein the second light-emitting device includes a second laser configured to emit the second light.

[0207] 7B. The apparatus according to any one of clauses 1B to 6B, wherein the light source system further comprises a light guide system configured to deliver light from the light source system to the pressure plate.

[0208] 8B. The apparatus according to Clause 7B, wherein the first optical guide portion of the optical guide system resides between at least two ultrasonic receiver system portions.

[0209] 9B. The apparatus according to Clause 8B, wherein the light guiding system includes a second light guiding portion configured to deliver the first light to the first light guiding portion and a third light guiding portion configured to deliver the second light to the first light guiding portion.

[0210] 10B. The apparatus according to any one of clauses 7B to 9B, wherein at least a portion of the ultrasonic receiver system is arranged as a loop around the first light guide portion.

[0211] 11B. The apparatus according to any one of clauses 7B to 10B, wherein the light guiding system includes a first light guiding device and a second light guiding device, the second light guiding device being configured to reflect light emitted by the second light-emitting device toward the first light guiding device.

[0212] 12B. The apparatus according to Clause 11B, wherein the first light guiding device is configured to guide light emitted by the first light-emitting device and the second light-emitting device along the first axis.

[0213] 13B. The apparatus according to Clause 12B, wherein the first axis is orthogonal to or substantially orthogonal to the plane of the pressure plate.

[0214] 14B. The apparatus according to any one of clauses 11B to 13B, wherein the first light guiding device includes a mirror and the second light guiding device includes a beam splitter.

[0215] 15B. The apparatus according to any one of clauses 1B to 14B, wherein the first axis is offset relative to the linear ultrasonic receiver element array at an angle ranging from 10 to 60 degrees from the normal to the plane of the pressure plate.

[0216] 16B. The apparatus according to Clause 15B, wherein the plane corresponds to the outer surface of the pressure plate.

[0217] 17B. The apparatus according to any one of clauses 1B to 16B, wherein the ultrasonic receiver system comprises a linear ultrasonic receiver element array, a two-dimensional ultrasonic receiver element array, or both.

[0218] 18B. The apparatus according to any one of clauses 1B to 17B, wherein the ultrasonic receiver system comprises a transparent array of ultrasonic receiver elements, a transparent piezoelectric layer, a transparent electrode layer, or a combination thereof.

[0219] 19B. The apparatus according to any one of clauses 1B to 18B, wherein the ultrasonic receiver system receives sound waves from the target object along a second axis different from the first axis, the sound waves corresponding to the first ultrasonic receiver signal and the second ultrasonic receiver signal.

[0220] 20B. The apparatus according to Clause 19B, wherein the second axis is separated from the first axis at an angle ranging from 10 degrees to 60 degrees.

[0221] 1C. An apparatus comprising: a pressure plate; a light source system configured to provide light to a target object on an outer surface of the pressure plate, the light comprising at least a first light of a first wavelength emitted by a first light-emitting device and a second light of a second wavelength emitted by a second light-emitting device, the light source system including a light guide system configured to deliver the first light and the second light to the pressure plate; an ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to the light from the light source system; and a control system configured to: cause the light source system to provide the first light to the target object at a first time; receive a first ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the first light; cause the light source system to provide the second light to the target object at a second time; receive a second ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the second light; and estimate one or more vascular features based on at least one of the first ultrasonic receiver signal or the second ultrasonic receiver signal.

[0222] 2C. The apparatus according to Clause 1C, wherein the control system is further configured to distinguish the desired signal from one or more background signals based at least in part on the first ultrasonic receiver signal and the second ultrasonic receiver signal.

[0223] 3C. The apparatus according to Clause 2C, wherein the desired signal corresponds to a blood vessel within the target object.

[0224] 4C. The device according to any one of clauses 1C to 3C, wherein the one or more vascular features include vascular diameter, vascular area, vascular profile, vascular dilation, volumetric flow rate, pulse wave velocity, vascular wall thickness, or a combination thereof.

[0225] 5C. The apparatus according to any one of clauses 1C to 4C, wherein the control system is further configured to estimate blood pressure at least in part based on the one or more vascular features.

[0226] 6C. The apparatus according to any one of clauses 1C to 5C, wherein the first light-emitting device includes a first laser configured to emit the first light, and the second light-emitting device includes a second laser configured to emit the second light.

[0227] 7C. The apparatus according to any one of clauses 1C to 6C, wherein the first optical guiding portion of the optical guiding system resides between at least two ultrasonic receiver system portions.

[0228] 8C. The apparatus according to Clause 7C, wherein the light guiding system includes a second light guiding portion configured to deliver the first light to the first light guiding portion and a third light guiding portion configured to deliver the second light to the first light guiding portion.

[0229] 9C. The apparatus according to any one of clauses 1C to 8C, wherein at least a portion of the ultrasonic receiver system is arranged as a loop around the first optical guide portion.

[0230] 10C. The apparatus according to any one of clauses 1C to 9C, wherein the light guiding system includes a light guide configured to deliver light in a direction parallel to or substantially parallel to the pressure plate.

[0231] 11C. The apparatus according to Clause 10C, wherein the light guide system includes a plurality of light extraction elements residing within the light guide, the light extraction elements being configured to direct light toward the pressure plate.

[0232] 12C. The apparatus according to any one of clauses 1C to 11C, wherein the ultrasonic receiver system comprises a linear ultrasonic receiver element array, a two-dimensional ultrasonic receiver element array, or both.

[0233] 13C. The apparatus according to any one of clauses 1C to 12C, wherein the ultrasonic receiver system comprises a transparent array of ultrasonic receiver elements, a transparent piezoelectric layer, a transparent electrode layer, or a combination thereof.

[0234] 14C. An apparatus according to any one of clauses 1C to 13C, wherein the light source system is configured to provide the first light to the target object along a first axis and is configured to provide the second light to the target object along the first axis.

[0235] 15C. The apparatus according to Clause 14C, wherein the ultrasonic receiver system receives sound waves from the target object along a second axis different from the first axis, the sound waves corresponding to the first ultrasonic receiver signal and the second ultrasonic receiver signal.

[0236] 16C. The apparatus according to Clause 15C, wherein the second axis is separated from the first axis at an angle ranging from 10 degrees to 60 degrees.

[0237] 1D. An apparatus comprising: a pressure plate; a light source system configured to provide light to a target object on an outer surface of the pressure plate, the light comprising at least a first light of a first wavelength emitted by a first light-emitting device and a second light of a second wavelength emitted by a second light-emitting device, the light source system including a light guide system comprising one or more light guides configured to deliver light in a direction parallel to or substantially parallel to the outer surface of the pressure plate; an ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to the light from the light source system; and a control system configured to: cause the light source system to provide the first light to the target object at a first time; receive a first ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the first light; cause the light source system to provide the second light to the target object at a second time; receive a second ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the second light; and estimate one or more vascular features based on at least one of the first ultrasonic receiver signal or the second ultrasonic receiver signal.

[0238] 2D. The apparatus according to Clause 1D, wherein the control system is further configured to distinguish the desired signal from one or more background signals based at least in part on the first ultrasonic receiver signal and the second ultrasonic receiver signal.

[0239] 3D. The apparatus according to Clause 2D, wherein the desired signal corresponds to a blood vessel within the target object.

[0240] 4D. The device according to any one of clauses 1D to 3D, wherein the one or more vascular features include vascular diameter, vascular area, vascular profile, vascular dilation, volumetric flow rate, pulse wave velocity, vascular wall thickness, or a combination thereof.

[0241] 5D. The device according to any one of clauses 1D to 4D, wherein the control system is further configured to estimate blood pressure at least in part based on the one or more vascular features.

[0242] 6D. An apparatus according to any one of clauses 1D to 5D, wherein the first light-emitting device includes a first laser configured to emit the first light, and the second light-emitting device includes a second laser configured to emit the second light.

[0243] 7D. An apparatus according to any one of clauses 1D to 6D, wherein the light guiding system includes a plurality of light extraction elements residing within the one or more light guides, the light extraction elements being configured to guide light toward the pressure plate.

[0244] 8D. The apparatus according to Clause 7D, wherein the light extraction element comprises one or more recesses in the light guide surface, one or more protrusions in the light guide surface, or one or more structures formed on the light guide surface.

[0245] 9D. The apparatus according to Clause 7D or Clause 8D, wherein the light extraction element comprises one or more three-dimensional shapes formed by the recess in the light guide surface, the protrusion in the light guide surface, or the structure formed on the light guide surface.

[0246] 10D. An apparatus according to any one of clauses 7D to 9D, wherein the light extraction element comprises one or more beam splitters.

[0247] 11D. The apparatus according to any one of clauses 7D to 10D, wherein the light extraction element comprises one or more mirrors or other reflective structures.

[0248] 12D. The apparatus according to any one of clauses 7D to 11D, wherein the two-dimensional light extraction element array is configured to provide substantially uniform light to an irradiation area on the outer surface of the pressure plate.

[0249] 13D. The apparatus according to any one of clauses 7D to 12D, wherein at least some of the light extraction elements are arranged at unequal intervals within the one or more light guides.

[0250] 14D. The apparatus according to Clause 13D, wherein light extraction elements located farther from the first light-emitting device are spaced closer to each other than light extraction elements located closer to the first light-emitting device.

[0251] 15D. The apparatus according to any one of clauses 1D to 14D, wherein the ultrasonic receiver system comprises a linear ultrasonic receiver element array, a two-dimensional ultrasonic receiver element array, or both.

[0252] 16D. The apparatus according to any one of clauses 1D to 15D, wherein the ultrasonic receiver system comprises a transparent ultrasonic receiver element array, a transparent piezoelectric layer, a transparent electrode layer, or a combination thereof.

[0253] 17D. The apparatus according to Clause 16D further includes a transparent backing layer residing between or between the one or more light guides and the transparent ultrasonic receiver element array, the transparent piezoelectric layer, the transparent electrode layer, or between the one or more light guides and combinations thereof.

[0254] 18D. The apparatus according to any one of clauses 1D to 17D, wherein one or more ultrasonic receiver elements of the ultrasonic receiver system reside on a first side of the one or more light guides, and the receiver system circuitry resides on an opposite second side of the one or more light guides.

[0255] 19D. The apparatus according to any one of clauses 1D to 18D, wherein the first light-emitting device resides on a first side of the pressure plate and the second light-emitting device resides on a second side of the pressure plate.

[0256] 20D. The apparatus according to Clause 19D, wherein the first side is adjacent to the second side.

[0257] 21D. The apparatus according to any one of clauses 1D to 20D, wherein the first light-emitting device and the second light-emitting device reside on a first side of the pressure plate.

[0258] As used in this article, the phrase “at least one of the items” refers to any combination of these items, including a single member. As an example, “at least one of a, b, or c” is intended to cover: a, b, c, ab, ac, bc, and abc.

[0259] The various exemplary logics, logic blocks, modules, circuits, and algorithmic processes described in conjunction with the specific implementations disclosed herein can be implemented as electronic hardware, computer software, or a combination of both. The interchangeability of hardware and software has been broadly described in terms of functionality and illustrated in the aforementioned exemplary components, blocks, modules, circuits, and processes. Whether such functionality is implemented in hardware or software depends on the specific application and the design constraints imposed on the overall system.

[0260] Hardware and data processing means for implementing the various exemplary logic units, logic blocks, modules, and circuits described herein can be implemented or executed using 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 units, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor can be a microprocessor, or any conventional processor, controller, microcontroller, or state machine. A processor can 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 combined with a DSP core, or any other such configuration. In some specific implementations, specific processes and methods can be performed by circuitry specific to a given function.

[0261] In one or more aspects, the described functionality may be implemented in hardware, digital electronic circuits, computer software, firmware, including the structures disclosed in this specification and their structural equivalents or any combination thereof. Specific implementations 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 a data processing apparatus or for controlling the operation of a data processing apparatus.

[0262] If implemented in software, the functions can be stored as one or more instructions or codes on or transmitted via a computer-readable medium such as a non-transitory medium. The processes of the methods or algorithms disclosed herein can be implemented in a processor-executable software module that can reside on a computer-readable medium. Computer-readable media include both computer storage media and communication media, including any medium capable of transferring a computer program from one location to another. Storage media can be any available medium accessible to a computer. By way of example and not limitation, non-transitory media can include RAM, ROM, EEPROM, CD-ROM or other optical disc storage devices, disk storage devices or other magnetic storage devices, or any other medium that can be used to store desired program code in the form of instructions or data structures and is accessible to a computer. Additionally, any connection can be appropriately referred to as a computer-readable medium. As used herein, disks and optical discs include compact optical discs (CDs), laser discs, optical discs, digital versatile optical discs (DVDs), floppy disks, and Blu-ray discs, wherein disks typically magnetically reproduce data, while optical discs optically reproduce data using lasers. Combinations of the above should also be included within the scope of computer-readable media. Additionally, the operation of a method or algorithm may reside as a set of code and instructions or any combination of code and instructions on a machine-readable medium and a computer-readable medium that may be incorporated into a computer program product.

[0263] Various modifications to the specific embodiments described herein may be apparent to those skilled in the art, and the general principles defined herein may be applied to other specific embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not intended to be limited to the specific embodiments shown herein, but is to be accorded the widest scope consistent with the claims, principles, and novel features disclosed herein. The word “exemplary” (if any) is used herein specifically to mean “serving as an example, instance, or illustration.” Any specific embodiment described herein as “exemplary” is not necessarily to be construed as superior to or better than other specific embodiments.

[0264] Certain features described in this specification in the context of a single embodiment may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments. Furthermore, although features may be described above as operating in certain combinations and even originally claimed in this way, one or more features from the claimed combination may be removed from that combination in some cases, and the claimed combination may be for sub-combinations or variations thereof.

[0265] Similarly, although operations are depicted in a specific order in the figures, this should not be construed as requiring such operations to be performed in the shown specific order or sequential order, or to perform all illustrated operations to achieve the desired result. In some environments, multitasking and parallel processing may be advantageous. Furthermore, the separation of the various system components in the embodiments described above 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 following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve the desired result.

[0266] It should be understood that unless features in any particular embodiment of the description are explicitly identified as incompatible with each other, or the surrounding context suggests that they are mutually exclusive and not easily combined in a complementary and / or supporting sense, the general conception and ideas of this disclosure may be selectively combined with specific features of those complementary embodiments to provide one or more comprehensive but slightly different technical solutions. Therefore, it should also be understood that the above description is given by way of example only and may be modified in detail within the scope of this disclosure.

[0267] Various modifications to the specific embodiments described in this disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other specific embodiments without departing from the spirit or scope of this disclosure. Therefore, the following claims are not intended to limit the specific embodiments shown herein, but are intended to be consistent with the maximum scope of this disclosure, the principles disclosed herein, and the novel features.

[0268] Additionally, some features described in this specification in the context of a single embodiment may also be implemented in combination within that single embodiment. Conversely, individual features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments. Furthermore, while some features are described above as working in a particular combination and even initially claimed in this way, in some cases, one or more features from the claimed combination may be extracted from that combination, and the claimed combination may involve sub-combinations or variations thereof.

[0269] Similarly, although operations are depicted in a specific order in the figures, this should not be construed as requiring such operations to be performed in the indicated specific order or sequential order, or to perform all illustrated operations to achieve the desired result. Furthermore, the figures may schematically depict one or more example processes in the form of flowcharts. However, other operations not depicted may be incorporated into the schematically illustrated example processes. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the illustrated operations. Moreover, the various agents in the described and illustrated operations may themselves include and collectively include several sub-operations. For example, each of the operations described above may itself involve the execution of a program or algorithm. Furthermore, in some embodiments, the various agents in the described and illustrated operations may be combined or performed in parallel. Similarly, the separation of various system components in the embodiments described above should not be construed as requiring this separation in all embodiments. Thus, other embodiments are within the scope of the following claims. In some cases, the actions recited in the claims may be performed in a different order and still achieve the desired result.

Claims

1. An apparatus, the apparatus comprising: Pressure plate; A light source system configured to provide light to a target object on the outer surface of the pressure plate, the light comprising at least a first light of a first wavelength emitted by a first light-emitting device and a second light of a second wavelength emitted by a second light-emitting device, the light source system being configured to provide the first light to the target object along a first axis and being configured to provide the second light to the target object along the first axis; An ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to light from the light source system; and The control system is configured to: The light source system provides the first light to the target object at the first moment; Receive a first ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the first light; The light source system then delivers the second light to the target object at a second time. Receive a second ultrasonic receiver signal from the ultrasonic receiver system corresponding to the photoacoustic response of the target object to the second light; and One or more vascular features are estimated based on at least one of the first ultrasound receiver signal or the second ultrasound receiver signal.

2. The apparatus of claim 1, wherein the control system is further configured to distinguish the desired signal from one or more background signals based at least in part on the first ultrasonic receiver signal and the second ultrasonic receiver signal.

3. The apparatus of claim 2, wherein the desired signal corresponds to a blood vessel within the target object.

4. The device according to claim 1, wherein the one or more vascular features include vascular diameter, vascular area, vascular profile, vascular dilation, volumetric flow rate, pulse wave velocity, vascular wall thickness, or combinations thereof.

5. The apparatus of claim 1, wherein the control system is further configured to estimate blood pressure at least in part based on the one or more vascular features.

6. The apparatus of claim 1, wherein the first light-emitting device includes a first laser configured to emit the first light, and wherein the second light-emitting device includes a second laser configured to emit the second light.

7. The apparatus of claim 1, wherein the light source system further comprises a light guide system configured to deliver light from the light source system to the pressure plate.

8. The apparatus of claim 7, wherein the first optical guide portion of the optical guide system resides between at least two ultrasonic receiver system portions.

9. The apparatus of claim 8, wherein the light guiding system includes a second light guiding portion configured to deliver the first light to the first light guiding portion and a third light guiding portion configured to deliver the second light to the first light guiding portion.

10. The apparatus of claim 7, wherein at least a portion of the ultrasonic receiver system is arranged as a loop around the first optical guide portion.

11. The apparatus of claim 7, wherein the light guiding system includes a first light guiding device and a second light guiding device, the second light guiding device being configured to reflect light emitted by the second light-emitting device toward the first light guiding device.

12. The apparatus of claim 11, wherein the first light guiding device is configured to guide light emitted by the first light-emitting device and the second light-emitting device along the first axis.

13. The apparatus of claim 12, wherein the first axis is orthogonal to or substantially orthogonal to the plane of the pressure plate.

14. The apparatus of claim 11, wherein the first light guiding device comprises a mirror, and the second light guiding device comprises a beam splitter.

15. The apparatus of claim 1, wherein the first axis is offset relative to the linear ultrasonic receiver element array at an angle ranging from 10 to 60 degrees from the normal to the plane of the pressure plate.

16. The apparatus of claim 15, wherein the plane corresponds to the outer surface of the pressure plate.

17. The apparatus of claim 1, wherein the ultrasonic receiver system comprises a linear ultrasonic receiver element array, a two-dimensional ultrasonic receiver element array, or both.

18. The apparatus of claim 1, wherein the ultrasonic receiver system comprises a transparent ultrasonic receiver element array, a transparent piezoelectric layer, a transparent electrode layer, or a combination thereof.

19. The apparatus of claim 1, wherein the ultrasonic receiver system receives sound waves from the target object along a second axis different from the first axis, the sound waves corresponding to the first ultrasonic receiver signal and the second ultrasonic receiver signal.

20. The apparatus of claim 19, wherein the second axis is separated from the first axis at an angle ranging from 10 degrees to 60 degrees.

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