Receiver array for photoacoustic device

Abstract

Some disclosed examples involve controlling, by a control system, a light source system to provide light to a target object on an outer surface of a platen, and receiving, by the control system, an ultrasonic receiver signal from each of a plurality of ultrasonic receiver elements in an array of ultrasonic receiver elements. The ultrasound receiver signal may correspond to ultrasound waves generated by the target object in response to light from the light source system. Some disclosed examples involve applying, by a control system, a receiver-side beamforming process to an ultrasound receiver signal to produce a beamformed ultrasound receiver image, and detecting, by the control system, a blood vessel within a target subject based at least in part on the beamformed ultrasound receiver image.

Description

[0001] Priority Statement

[0002] This application claims priority to U.S. Patent Application No. 18 / 323,021, filed May 24, 2023, entitled “Receiver Array for Optoacoustic Devices,” which is incorporated herein by reference in its entirety and for all purposes. Technical Field

[0003] This disclosure relates generally to photoacoustic devices, and more specifically to receiver arrays for photoacoustic devices. Background Technology

[0004] Various sensing technologies and algorithms are being implemented in a wide range of biometric and biomedical applications, including health and health monitoring devices. This push is partly due to the limitations of traditional measurement devices in terms of continuous, non-invasive, and ambulatory monitoring. Some of these devices are or include photoacoustic devices. While some previously deployed photoacoustic devices and systems have provided acceptable results, improvements to photoacoustic devices and systems are expected. Summary of the Invention

[0005] The systems, methods, and apparatuses disclosed herein each have several aspects, none of which individually assumes the desired properties of the disclosure herein.

[0006] One innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus. In some embodiments, a mobile device (such as a wearable device, a cellular phone, etc.) may be, 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 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 source system may include a light source array. The receiver system may be, or may include, an ultrasonic receiver system having an array of ultrasonic receiver elements. The ultrasonic receiver system may be configured to receive ultrasonic waves generated by the target object in response to light from the light source system.

[0007] In some embodiments, the apparatus 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, discrete hardware components, or combinations thereof. The control system may be configured to receive ultrasound receiver signals from each of a plurality of ultrasound receiver elements in an array. The ultrasound receiver signals may correspond to ultrasound waves generated by a target object in response to light from a light source system. According to some examples, the control system may be configured to apply a receiver-side beamforming process to the ultrasound receiver signals to produce a beamformed ultrasound receiver image. In some such examples, the receiver-side beamforming process may be or may include a delay-and-sum beamforming process. In some examples, the control system may be configured to detect blood vessels within a target object based at least in part on the beamformed ultrasound receiver image.

[0008] According to some examples, the control system can be configured to detect blood vessels within a target object based at least in part on ultrasound receiver signals. In some examples, the control system can also be configured to estimate one or more vascular features based at least in part on beamformed ultrasound receiver images. According to some examples, one or more vascular features may include vessel diameter, vessel area, vessel profile, vascular dilation, volumetric flow, pulse wave velocity, vessel wall thickness, or combinations thereof. In some examples, the control system can also be configured to estimate blood pressure based at least in part on one or more vascular features.

[0009] In some examples, the equipment may be configured to be worn or attached to a person. According to some examples, the array of ultrasound receiver elements may include a linear array of ultrasound receiver elements arranged along an array axis configured to extend along a blood vessel, wherein the array axis is within ±45 degrees of the blood vessel axis. In some examples, the array of ultrasound receiver elements may include a linear array of ultrasound receiver elements arranged along an array axis configured to extend through a blood vessel.

[0010] According to some examples, the array of ultrasonic receiver elements may include a linear array of ultrasonic receiver elements having a spacing between adjacent ultrasonic receiver elements equal to the wavelength corresponding to the peak frequency of the ultrasonic wave generated by the target object in response to light from the light source system. In some examples, the array of ultrasonic receiver elements may include a phased array of ultrasonic receiver elements having a spacing between adjacent ultrasonic receiver elements equal to a multiple of half the wavelength corresponding to the peak frequency of the ultrasonic wave generated by the target object in response to light from the light source system. According to some examples, the array of ultrasonic receiver elements may include a two-dimensional array of ultrasonic receiver elements.

[0011] In some examples, the array of ultrasonic receiver elements may include an array of electrodes arranged on a piezoelectric layer. In some such examples, the piezoelectric layer may include lead zirconate titanate (PZT) or a piezoelectric composite material.

[0012] Other innovative aspects of the subject matter described in this disclosure can be implemented in a method. This method may involve controlling a light source system, via a control system, to provide light to a target object on the outer surface of a pressure plate.

[0013] According to some examples, the method may involve a control system receiving an ultrasonic receiver signal from each of a plurality of ultrasonic receiver elements in an array of ultrasonic receiver elements. The ultrasonic receiver signal may correspond to an ultrasonic wave generated by a target object in response to light from a light source system.

[0014] In some examples, the method may involve applying a receiver-side beamforming process to an ultrasound receiver signal by a control system to produce a beamformed ultrasound receiver image. In some such examples, the receiver-side beamforming process may be, or may include, a delay and summation beamforming process.

[0015] According to some examples, the method may involve detecting blood vessels within a target object by a control system based at least in part on beamformed ultrasound receiver images. In some examples, the method may involve detecting blood vessels within a target object based at least in part on ultrasound receiver signals. According to some examples, the method may involve estimating one or more vascular features based at least in part on beamformed ultrasound receiver images.

[0016] According to some examples, 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 method may involve estimating blood pressure based at least in part on one or more vascular features.

[0017] 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 a non-transitory medium may include memory devices such as those described herein, including but not limited to random access memory (RAM) devices, read-only memory (ROM) devices, etc. Therefore, some innovative aspects of the subject matter described in this disclosure 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.

[0018] According to some examples, the method may involve a control system receiving an ultrasonic receiver signal from each of a plurality of ultrasonic receiver elements in an array of ultrasonic receiver elements. The ultrasonic receiver signal may correspond to an ultrasonic wave generated by a target object in response to light from a light source system.

[0019] In some examples, the method may involve applying a receiver-side beamforming process to an ultrasound receiver signal by a control system to produce a beamformed ultrasound receiver image. In some such examples, the receiver-side beamforming process may be, or may include, a delay and summation beamforming process.

[0020] According to some examples, the method may involve detecting blood vessels within a target object by a control system based at least in part on beamformed ultrasound receiver images. In some examples, the method may involve detecting blood vessels within a target object based at least in part on ultrasound receiver signals. According to some examples, the method may involve estimating one or more vascular features based at least in part on beamformed ultrasound receiver images.

[0021] According to some examples, 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 method may involve estimating blood pressure based at least in part on one or more vascular features.

[0022] Details of one or more embodiments of the subject matter described in this disclosure are set forth in the accompanying drawings and the following description. Other features, aspects, and advantages will become apparent from the specification, drawings, and claims. Note that the relative dimensions in the following drawings may not be drawn to scale. Attached Figure Description

[0023] Figure 1 This is a block diagram illustrating example components of an apparatus according to some disclosed embodiments.

[0024] Figure 2A and Figure 2B An example of an array of ultrasonic receiver elements is shown.

[0025] Figure 3A and Figure 4A Other examples of ultrasonic receiver element arrays are shown.

[0026] Figure 3B and Figure 4B It shows that it can be obtained from Figure 3A and Figure 4A An example of image data obtained by the ultrasonic receiver element array shown.

[0027] Figure 4C Another example of an array of ultrasonic receiver elements is shown.

[0028] Figure 5A Example components of an apparatus according to some disclosed embodiments are shown.

[0029] Figure 5B Example components of an apparatus according to some alternative implementations are shown.

[0030] Figure 6 An example of equipment configured to perform a receiver-side beamforming process is shown.

[0031] Figure 7A , Figure 8A and Figure 9A An apparatus with photoacoustic plethysmography (PAPG) capability is shown, along with examples of arteries at three different locations relative to the apparatus.

[0032] Figure 7B , Figure 8B and Figure 9B They are shown respectively in Figure 7A , Figure 8A and Figure 9A The image data shown is an example of image data obtained by equipment with PAPG capability in the case of artery location.

[0033] Figure 10 This is a flowchart illustrating some examples of publicly available operations.

[0034] Figure 11 Examples of heart rate waveform (HRW) features that can be extracted according to some implementations of the method in Figure 23 are shown.

[0035] Figure 12 An example device is shown that can be used in a system for estimating blood pressure based at least in part on pulse conduction time (PTT).

[0036] Figure 13 A schematic cross-sectional side view of a portion of an artery through which the pulse travels is shown.

[0037] Figure 14A An example dynamic monitoring device designed to be worn around the wrist, according to some embodiments, is shown.

[0038] Figure 14B An example motion monitoring device designed to be worn on a finger is shown according to some embodiments.

[0039] Figure 14C An example dynamic monitoring device designed to be placed on an earpiece is shown according to some embodiments.

[0040] The same reference numerals and names in the various figures indicate the same elements. Detailed Implementation

[0041] For the purpose of describing various aspects of this disclosure, the following description is directed to certain embodiments. However, those skilled in the art will readily recognize that the teachings herein can be applied in a variety of different ways. Some of the concepts and examples provided in this disclosure are particularly applicable to blood pressure monitoring applications. However, some embodiments may also be applicable to other types of biosensing applications, as well as other fluid flow systems. The described embodiments can be implemented in any device, apparatus, or system that includes the equipment disclosed herein. Furthermore, it is contemplated that the described embodiments can be included in or associated with a variety of electronic devices, such as, but not limited to: mobile phones, cellular phones with multimedia internet support, mobile TV receivers, wireless devices, smartphones, smart cards, wearable devices such as bracelets, armbands, wristbands, rings, headbands, patches, etc., Bluetooth® devices, personal data assistants (PDAs), wireless email receivers, handheld or portable computers, netbooks, laptops, smartbooks, tablets, printers, copiers, scanners, fax machines, GPS receivers / navigators, cameras, digital media players. Devices such as game consoles, wristwatches, clocks, calculators, television displays, flat panel displays, e-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 for 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 timers, car doors, automatic or semi-automatic vehicles, drones, Internet of Things (IoT) devices, etc. Therefore, these teachings are not intended to be limited to the specific embodiments depicted and described with reference to the accompanying drawings; rather, these teachings have a broad applicability, which will be apparent to those skilled in the art.

[0042] Non-invasive health monitoring devices, such as those with photoacoustic plethysmography (PAPG) capabilities, offer various potential advantages over invasive devices, such as cuff-based or catheter-based blood pressure measurement devices. However, designing satisfactory PAPG-based devices has proven challenging. One challenge is the low signal-to-noise ratio (SNR) of the signal of interest, such as the signal corresponding to ultrasound induced by the photoacoustic response of the arterial wall. For example, the signal corresponding to the arterial wall is typically significantly lower in amplitude than the signal corresponding to the photoacoustic response of the skin. Another challenge is that the orientation of the same artery can vary from user to user and even within the same user's body. These variations in arterial orientation can make properly positioning the ultrasound receiver in a PAPG-based device challenging. Even small changes in the ultrasound receiver's position can lead to significant differences in the received signal corresponding to the arterial wall.

[0043] Some disclosed devices include a pressure plate, a light source system, an ultrasound receiver system, and a control system. According to some embodiments, the light source system can be configured to provide light to a target object on the outer surface of the pressure plate. The ultrasound receiver system can be configured to receive ultrasound waves generated by the target object in response to light from the light source system. The ultrasound receiver system can include an array of ultrasound receiver elements. According to some embodiments, the control system can be configured to apply a receiver-side beamforming process to ultrasound receiver signals received from each of a plurality of ultrasound receiver elements in the array. In some embodiments, the control system can be configured to detect blood vessels within the target object based at least partially on beamformed ultrasound receiver images. According to some embodiments, the control system can be configured to estimate one or more vascular features based at least partially on beamformed ultrasound receiver images. In some embodiments, the control system can be configured to estimate blood pressure based at least partially on one or more vascular features.

[0044] Specific embodiments of the subject matter described in this disclosure can be implemented to achieve one or more of the following potential advantages. Various disclosed configurations include devices with PAPG capability, which can provide a higher SNR for signals corresponding to the photoacoustic response of one or more arterial walls compared to previously deployed devices with a single receiver element. Signals obtained from multiple receiver elements of an ultrasound receiver array can provide information about the location of arteries that would not be available if the signal were obtained from only a single ultrasound receiver element. Signals obtained from multiple receiver elements of an ultrasound receiver array can provide information about local pulse wave velocity, which can provide information about arterial hemodynamics, local stiffening, etc. An array of ultrasound receiver elements can provide greater tolerance for misalignment of the ultrasound receiver system compared to an ultrasound receiver system with a single receiver element.

[0045] Figure 1 This is a block diagram illustrating example components of an apparatus according to some disclosed embodiments. In this example, apparatus 100 includes a pressure plate 101, an ultrasonic receiver system 102, a control system 106, and a light source system 104. Some embodiments of apparatus 100 may include an interface system 108, a noise reduction system 110, or both. As with other disclosed embodiments, in some alternative embodiments, apparatus 100 may include more components, fewer components, or different components.

[0046] In some embodiments, the pressure plate 101 may be configured to increase the intensity of ultrasonic energy received at least partially by the ultrasonic receiver system. In some such embodiments, the pressure plate 101 may include an acoustic waveguide. According to some embodiments, the pressure plate 101 may include an acoustic lensing system. The acoustic lensing system may, for example, be disposed on or near the outer surface of the pressure plate 101. The acoustic lensing system may, for example, include a spherical lens or a cylindrical lens.

[0047] According to some examples, the pressure plate 101, the light source system 104, or a combination thereof can be configured to transmit at least some of the light from the light source system along a first axis or substantially along the first axis to the outer surface of the pressure plate (or to a target object on or near the outer surface), the first axis being oriented at a first angle relative to the outer surface of the pressure plate. In this context, "substantially along the first axis" can mean an angle range of ±10 degrees, ±15 degrees, ±20 degrees, ±25 degrees, ±30 degrees, or other such angle ranges along the first axis.

[0048] In some examples, at least a portion of the pressure plate 101 may be configured to transmit at least some of the ultrasonic waves generated by the target object along or substantially along a third axis at a third angle relative to the outer surface of the pressure plate. According to some examples, the third axis may be parallel to the second axis.

[0049] According to some examples, the pressure plate 101 may include different portions, which may have varying thicknesses, orientations, etc., depending on the specific implementation. In some examples, the pressure plate 101 may include a first pressure plate portion disposed between the light source system and the outer surface of the pressure plate. In some examples, the first pressure plate portion may have a thickness smaller than that of a second pressure plate portion disposed between at least one receiver element of the ultrasonic receiver system 102 and the outer surface of the pressure plate. In some such examples, the first pressure plate portion may be configured to receive light from the light source system and may also be configured to reflect ultrasonic waves generated by a target object toward at least one receiver element of the receiver system. However, in some examples, the first pressure plate portion disposed between the light source system and the outer surface of the pressure plate may have a thickness larger than that of a second pressure plate portion disposed between at least one receiver element of the ultrasonic receiver system 102 and the outer surface of the pressure plate.

[0050] According to some examples, pressure plate 101 (or other parts of the equipment) may include one or more anti-reflective layers. In some examples, one or more anti-reflective layers may be placed on or near one or more outer surfaces of pressure plate 101.

[0051] 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. (The terms “finger” and “digit” as used herein are used interchangeably, with the thumb being an example of a finger). Typical acoustic impedance ranges from 1.53 to 1.680 MRayls. In some examples, at least the outer surface of the pressure plate 101 may have an acoustic impedance in the range of 1.4–1.8 MRayls or in the range of 1.5–1.7 MRayls.

[0052] 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.

[0053] 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 ultrasonic receiver system 102. According to some examples, a layer disposed 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 disposed between the pressure plate 101 and one or more receiver elements may have an acoustic impedance within the range of acoustic impedance between the acoustic impedance of the pressure plate and the acoustic impedance of one or more receiver elements.

[0054] In this example, the ultrasonic receiver system 102 includes an array of ultrasonic receiver elements. Various examples and configurations of the ultrasonic receiver system 102 are disclosed herein. According to some examples, the array of ultrasonic receiver elements may be a linear array. In other examples, the array of ultrasonic receiver elements may be a two-dimensional array. According to some examples, the linear or two-dimensional array of ultrasonic receiver elements may be arranged in a plane, while in other examples, the linear or two-dimensional array of ultrasonic receiver elements may be arranged along a non-planar surface, such as a curved surface. In some examples, the linear or two-dimensional array of ultrasonic receiver elements may be a phased array, wherein there is a phase difference between samples from adjacent ultrasonic receiver elements. Some examples are described in more detail below. In some examples, the ultrasonic receiver system 102 may include an array of electrodes arranged on a piezoelectric receiver layer, such as a PVDF polymer layer, a PVDF-TrFE copolymer layer, or a piezoelectric composite layer. In some embodiments, other piezoelectric materials, such as aluminum nitride (AlN) or lead zirconate titanate (PZT), may be used in the piezoelectric layer.

[0055] In some examples, apparatus 100 can be configured to transmit and receive ultrasound. In some examples, ultrasound receiver system 102 may include an array of ultrasound transducer elements, such as a piezoelectric micromechanical ultrasound transducer (PMUT) array, a capacitive micromechanical ultrasound transducer (CMUT) array, etc. In some such examples, a piezoelectric receiver layer, PMUT elements in a single-layer PMUT array, or CMUT elements in a single-layer CMUT array can be used as both an ultrasound transmitter and an ultrasound receiver. According to some examples, ultrasound receiver system 102 may be or may include an ultrasound receiver array. In some examples, apparatus 100 may include one or more separate ultrasound transmitter elements. In some such examples, the ultrasound transmitter may include an ultrasound plane wave generator. However, in some examples, the same layer (e.g., a single piezoelectric layer) may be configured to transmit and receive ultrasound. According to some examples, an array of electrodes may be placed on the same piezoelectric layer. In some such examples, the array of electrodes and the piezoelectric layer can be used as both an ultrasound transmitter array and an ultrasound receiver array. Therefore, in some examples, ultrasound receiver system 102 may also be used as an ultrasound transmitter system.

[0056] According to some examples, the ultrasound receiver system 102 may include an array of ultrasound receiver elements disposed in a receiver plane. In some examples, the normal to the receiver plane may be oriented along or substantially along a second axis, which is at a second angle relative to the outer surface of the pressure plate. In this context, "substantially along the second axis" may mean within an angle range of ±10 degrees, ±15 degrees, ±20 degrees, ±25 degrees, ±30 degrees, or other such angle ranges. According to some examples, the second axis may be parallel to the first axis. However, in some examples, the second angle may differ from the first angle.

[0057] According to some embodiments, 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. In some examples, the light source system 104 may include an array of light-emitting elements, such as an LED array, a laser diode array, a VCSEL array, an edge-emitting laser array, or a combination thereof.

[0058] According to some examples, the light source system 104 may include one or more light-directing elements configured to guide light from the light source system along a first axis to a target object. In some examples, the one or more light-directing elements may include at least one diffraction grating. Alternatively or additionally, the one or more light-directing elements may include at least one lens.

[0059] In some examples, the light source system 104 can be configured to emit light within one or more wavelength ranges. In some examples, the light source system 104 can be configured to emit light in the 500 to 600 nanometer wavelength range. According to some examples, the light source system 104 can be configured to emit light in the 800 to 950 nanometer wavelength range.

[0060] 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, which can generate 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 lines) 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 with pulse repetition frequencies ranging from 1 kHz to 100 kHz.

[0061] In some examples, the light source system 104 may include a light source system surface having a normal parallel to or substantially parallel to the first axis. In some such examples, the light source of the light source system may be placed on or near the light source system surface.

[0062] 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 hemoglobin 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 hemoglobin. However, in some examples, the control system 106 can control the wavelength of the light emitted by the light source system 104 to preferentially induce acoustic emission in blood vessels, other soft tissues, and / or bone. For example, an infrared (IR) light-emitting diode (LED) can be selected, and short IR light pulses can be emitted to illuminate portions of the target object and generate acoustic emission, which is then detected by the ultrasound receiver system 102. In another example, IR LEDs and red LEDs or other colors, such as green, blue, white, or ultraviolet (UV), can be selected, and short light pulses can be emitted sequentially from each light source, with an ultrasound image acquired after light is emitted from each light source. In other embodiments, one or more light sources of different wavelengths can be excited sequentially or simultaneously to generate acoustic emission that can be detected by the ultrasound receiver. Image data from an ultrasound receiver, obtained at different depths (e.g., varying RGDs) within the target object using light sources of different wavelengths, can be combined to determine the location and type of material. Since materials in the body typically absorb light of different wavelengths differently, image contrast can occur. Because materials within the body absorb light of specific wavelengths, they can generate heat differently and produce acoustic emission of sufficiently short light pulses of sufficient intensity. Depth contrast can be achieved using light of different wavelengths and / or varying intensities at each selected wavelength. That is, continuous images with varying light intensities and wavelengths can be obtained at a fixed RGD (which may correspond to a fixed depth within the target object) to detect materials within the target object and their location. For example, photoacoustic detection of hemoglobin, blood glucose, or blood oxygen within blood vessels inside a target object such as a finger can be performed.

[0063] According to some embodiments, the light source system 104 can be configured to emit light pulses with pulse widths less than about 100 nanoseconds. In some embodiments, the light pulses can have pulse widths of about 10 nanoseconds to about 500 nanoseconds or greater. According to some examples, the light source system can be configured to emit multiple light pulses with pulse repetition frequencies 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 with pulse repetition frequencies 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 with pulse repetition frequencies between about 10 Hz and about 1 MHz. In some examples, the pulse repetition frequency of the light pulses can correspond to the acoustic resonant frequency of the ultrasonic receiver and the substrate. For example, a set of four or more light pulses with frequencies corresponding to the resonant frequency of the resonant acoustic cavity in the sensor stack can be emitted from the light source system 104, which allows for the establishment of received ultrasonic waves and higher synthesized signal strength. In some embodiments, the light source system 104 can include filtered light or a light source with a specific wavelength for detecting selected materials. In some implementations, the light source system may include light sources such as red, green, and blue LEDs for a display, which may be enhanced with light sources of other wavelengths (e.g., IR and / or UV) and 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 illumination of the target object.

[0064] 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, discrete hardware components, or combinations thereof. Control system 106 may also include one or more memory devices (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, equipment 100 may have a memory system including one or more memory devices, although such memory system is not explicitly described in the original text. Figure 1 As shown in the diagram. The control system 106 can be configured to receive and process data from the ultrasound receiver system 102, for example, as described below. If the equipment 100 includes an ultrasound transmitter, the control system 106 can be configured to control the ultrasound transmitter. In some embodiments, the functionality of the control system 106 can be divided between one or more controllers or processors, such as a dedicated sensor controller for a mobile device and an application processor.

[0065] In some examples, the control system 106 may be configured to control the light source system 104 to emit light toward a target object on the outer surface of the pressure plate 101. In some such examples, the control system 106 may be configured to receive a signal from each of a plurality of ultrasound receiver elements in an array of ultrasound receiver elements of the ultrasound receiver system 102. The signal may correspond to an ultrasound wave generated by the target object in response to light from the light source system 104. In some examples, the control system 106 may be configured to apply a receiver-side beamforming process to the ultrasound receiver signal to generate a beamformed ultrasound receiver image. According to some examples, the control system 106 may be configured to detect blood vessels within the target object based at least in part on the beamformed ultrasound receiver image. In some such examples, the control system 106 may be configured to estimate one or more vascular features based at least in part on the beamformed ultrasound receiver image. In some examples, the control system 106 may be configured to estimate one or more cardiac features based at least in part on one or more arterial signals and vascular features. According to some examples, cardiac features may be or may include blood pressure.

[0066] Alternatively or additionally, in some examples, the control system 106 may be configured to control an ultrasound transmitter to emit ultrasound toward a target object on the outer surface of the pressure plate 101. In some such examples, the control system 106 may be configured to receive a signal from each of a plurality of ultrasound receiver elements in an array of ultrasound receiver elements of the ultrasound receiver system 102. The signal may correspond to an ultrasound wave reflected by the target object in response to the emitted ultrasound. In some examples, the control system 106 may be configured to apply a receiver-side beamforming process to the ultrasound receiver signal to generate a beamformed ultrasound receiver image. According to some examples, the control system 106 may be configured to detect blood vessels within the target object based at least in part on the beamformed ultrasound receiver image. In some such examples, the control system 106 may be configured to estimate one or more vascular features based at least in part on the beamformed ultrasound receiver image. In some examples, the control system 106 may be configured to estimate one or more cardiac features based at least in part on one or more arterial signals and vascular features. According to some examples, cardiac features may be or may include blood pressure.

[0067] Some embodiments of the device 100 may include an interface system 108. In some examples, the interface system 108 may include a wireless interface system. In some embodiments, the interface system 108 may include a user interface system, one or more network interfaces, one or more interfaces between the control system 106 and a memory system, and / or one or more interfaces or combinations thereof between the control system 106 and one or more external device interfaces (e.g., ports or application processors). According to some examples where the 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, the 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.

[0068] 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), other suitable types of force sensors, or combinations thereof. If the force sensor system includes a piezoresistive sensor, the piezoresistive sensor may include silicon, metal, polycrystalline silicon, glass, or combinations thereof. In some embodiments, the ultrasonic fingerprint sensor and the force sensor system may be mechanically coupled. In some such examples, the force sensor system may be integrated into the circuitry of the ultrasonic fingerprint sensor. In some examples, interface system 108 may include an optical sensor system, one or more cameras, or combinations thereof.

[0069] According to some examples, equipment 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 ultrasonic receiver system 102. In some embodiments, noise reduction system 110 may include one or more sound-absorbing layers, acoustic isolation materials, light-absorbing materials, reflective materials, or combinations thereof. In some examples, noise reduction system 110 may include acoustic isolation materials that may be placed between, on, or in combination with at least a portion of light source system 104 and ultrasonic receiver system 102. In some examples, noise reduction system 110 may include one or more electromagnetically shielded transmission lines. In some such examples, one or more electromagnetically shielded transmission lines may be configured to reduce electromagnetic interference received by ultrasonic receiver system 102 from circuitry of light source system 104, receiver system circuitry, or combinations thereof. In some examples, one or more electromagnetically shielded transmission lines, sound-absorbing layers, acoustic isolation materials, light-absorbing materials, reflective materials, or combinations thereof may be components of ultrasonic receiver system 102, light source system 104, or both. Although in fact the ultrasonic receiver system 102, the light source system 104, and the noise reduction system 110 are in Figure 1 Although shown as separate components, these components can still be considered as elements of the noise reduction system 110.

[0070] Equipment 100 can be used in a variety of different contexts, many of which are disclosed herein. For example, in some implementations, a mobile device may include equipment 100. In some such examples, the mobile device may be a smartphone. In some implementations, a wearable device may include equipment 100. For example, a wearable device may be a bracelet, armband, wristband, watch, ring, headband, or patch. Thus, in some examples, equipment 100 may be configured to be worn by or attached to a person.

[0071] Figure 2A and Figure 2B Examples of ultrasound receiver element arrays are shown. In these examples, array axis 220 corresponds to the x-axis of the coordinate system. According to these examples, each array 202 of ultrasound receiver elements includes two grounded elements 205, two inactive or "dead" ultrasound receiver elements 210, and six active ultrasound receiver elements 215. Arrows shown within blood vessels 225a and 225b indicate the direction of blood flow. As with other disclosed examples, Figure 2A and Figure 2B The types, quantities, sizes, and arrangements of the elements shown and described herein are merely examples.

[0072] according to Figure 2A and Figure 2B In the examples shown, each of the movable ultrasound receiver elements 215 extends further in the y-direction than in the x-direction. In other words, in these examples, each of the movable ultrasound receiver elements 215 extends further in the direction perpendicular to axis 220 than in the direction perpendicular to axis 220. For convenience, the dimension of the movable ultrasound receiver element 215 in the x-direction can be referred to as the width, while the dimension of the movable ultrasound receiver element 215 in the y-direction can be referred to as the length.

[0073] In some examples, Figure 2A and Figure 2B The active ultrasound receiver element 215 can have a length on the order of millimeters (mm), such as 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, etc., according to some examples. Figure 2A The active ultrasound receiver element 215 can have a smaller than Figure 2B The width of the active ultrasound receiver element 215. In some such examples, Figure 2A The active ultrasound receiver element 215 can have a width of less than 1 mm, such as 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm, etc. According to some examples, Figure 2B The active ultrasound receiver element 215 can have a width greater than 1 mm, such as 1.1 mm, 1.15 mm, 1.2 mm, 1.25 mm, 1.3 mm, 1.35 mm, 1.4 mm, 1.45 mm, 1.5 mm, etc. In some examples, the kerf or separation between adjacent active ultrasound receiver elements 215 can be less than 0.1 mm, such as 0.030 mm, 0.040 mm, 0.050 mm, 0.060 mm, 0.070 mm, etc.

[0074] According to some examples, the spacing between adjacent active ultrasonic receiver elements 215 can be equal to the wavelength corresponding to the peak frequency of the ultrasonic wave generated by the target object in response to light from the light source system. In some examples, the peak frequency can be in the range of 1 MHz to 12 MHz.

[0075] However, in some alternative examples, the spacing between adjacent active ultrasonic receiver elements 215 can be a multiple of half the wavelength corresponding to the peak frequency of the ultrasonic wave generated by the target object in response to light from the light source system. In some such examples, the array 202 of ultrasonic receiver elements can be a phased array of ultrasonic receiver elements. The multiple can be 1, 2, 3, 4, etc.

[0076] According to some examples, the array 202 of the ultrasonic receiver elements can be an array of electrodes arranged on a piezoelectric layer. The piezoelectric layer can be or can include lead zirconate titanate (PZT), a piezoelectric composite material, or a combination thereof. The composite piezoelectric material can be, for example, a 1-3 composite material, a 2-2 composite material, a 3-3 composite material, etc.

[0077] exist Figure 2A In the example shown, an array 202 of ultrasound receiver elements is arranged along an array axis 220, which is configured to extend through a blood vessel 225a. In this example, Figure 2A A portion of the blood vessel 225a shown extends along the vessel axis 230a. According to this example, the angle α between the array axis 220 and the vessel axis 230a is greater than 45 degrees. In some examples, the angle α can be greater than 60 degrees, greater than 75 degrees, etc. Making the angle α close to 90 degrees (such as within the range of 70 to 110 degrees) may be advantageous for imaging the cross-section of the blood vessel. Such images may be useful for detecting changes in vessel diameter during the systolic and diastolic phases of the cardiac cycle.

[0078] exist Figure 2B In the example shown, an array 202 of ultrasound receiver elements is arranged along an array axis 220, which is configured to extend along a blood vessel 225b. In this example, Figure 2B A portion of the blood vessel 225b shown extends along the vessel axis 230b. According to this example, the angle α between the array axis 220 and the vessel axis 230b is less than ±45 degrees. In other words, the absolute value of angle α can be less than 45 degrees. In some examples, the absolute value of angle α can be less than 30 degrees, less than 20 degrees, etc. Making the absolute value of angle α close to zero degrees (such as in the range of -20 degrees to 20 degrees) may be advantageous for imaging along the vessel axis. Such images may be useful for detecting blood flow within the vessel, determining local pulse wave velocity, etc.

[0079] Figure 3A and Figure 4A An additional example of an array of ultrasonic receiver elements is shown. Figure 3B and Figure 4B It shows that it can be obtained from Figure 3A and Figure 4A An example of image data obtained by an array of ultrasound receiver elements is shown. Figure 3A and Figure 4A In the example shown, array axis 220 corresponds to the x-axis of the coordinate system, the viewing angle is along the y-axis, and the blood vessels are shown separated from the array 202 of ultrasound receiver elements in the z-direction. As with other disclosed examples, Figure 3A and Figure 4A The types, quantities, sizes, and arrangements of the elements shown and described herein are merely examples.

[0080] Figure 3A The array 202 of ultrasound receiver elements shown is arranged along an array axis 220, which is configured to extend through a blood vessel 225c. In some examples, Figure 3A The array 202 of ultrasound receiver elements shown can be similar to Figure 2A An array 202 of ultrasound receiver elements or an example thereof is shown. However, in this example, the vascular axis 230c is perpendicular to the array axis 220. According to this example, Figure 3A Arrow 305 shown corresponds to the wall of blood vessel 225c, which is supported by light source system 104. Figure 3A The photoacoustic response of light (not shown in the image) corresponds to the ultrasonic wave.

[0081] Figure 3B The image data shown is Figure 3A The array 202 of ultrasound receiver elements corresponds to the ultrasound waves received instantaneously from the blood vessel 225c. In this example, Figure 3B The arrow tip shown is touching. Figure 3A The image data region corresponding to the vessel wall distal to 310 of the shown vessel 225c. Data acquired over time, such as... Figure 3B The image data shown may be useful for detecting changes in vessel diameter during the systolic and diastolic phases of the cardiac cycle.

[0082] Figure 4A The array 202 of ultrasound receiver elements shown is arranged along an array axis 220, which is configured to extend through a blood vessel 225b. Figure 4A The array 202 of the ultrasound receiver elements and the blood vessel 225b shown are Figure 2B An example of an array 202 of ultrasound receiver elements and a blood vessel 225b is shown. According to this example, Figure 4A Arrow 305 shown corresponds to the light source system 104 of the wall of blood vessel 225b. Figure 4A The photoacoustic response of light (not shown in the image) corresponds to the ultrasonic wave.

[0083] Figure 4B The image data shown is Figure 4A The array 202 of ultrasound receiver elements corresponds to the ultrasound waves received instantaneously from the blood vessel 225b. In this example, Figure 4B The tip of the arrow shown is in contact with... Figure 4A The region of image data corresponding to the vessel wall on the distal side 310 of the illustrated vessel 225b. Data acquired over time, such as... Figure 4B The image data shown may be useful for detecting blood flow within blood vessel 225b and determining local pulse wave velocity.

[0084] Figure 4CAnother example of an array of ultrasound receiver elements is shown. In this example, the array 202 of ultrasound receiver elements is a two-dimensional array of ultrasound receiver elements. According to this example, the array 202 of ultrasound receiver elements is arranged in a square, with 6 active ultrasound receiver elements 215 on each side, and a total of 36 active ultrasound receiver elements 215. Similar to other disclosed examples, Figure 4C The types, numbers, sizes, and arrangements of the elements shown and described herein are merely examples. For instance, alternative examples of a two-dimensional array of ultrasound receiver elements may be arranged in different shapes (such as non-square rectangular shapes, hexagonal shapes, etc.). Some alternative examples of a two-dimensional array of ultrasound receiver elements may include different numbers of active ultrasound receiver elements 215, such as 16, 20, 25, 30, 32, 36, 40, 48, etc.

[0085] Figure 5A Example components of an apparatus according to some disclosed embodiments are shown. (This is in conjunction with other appendices provided herein.) Figure 1 Sample, Figure 5A The number, type, and arrangement of the components shown are merely illustrative. In this example, apparatus 100 is an instance of the apparatus 100 shown in Figure 3. According to this example, apparatus 100 includes a pressure plate 101, a receiver system 102, and a light source system 104. In this example, the outer surface 508a of the pressure plate 101 is configured to receive a target object, such as a finger 115, a wrist, etc. In this example, the finger 115 includes blood vessels 225d.

[0086] According to this example, the light source system 104 includes a light-emitting portion 104a and a lens 104b. In this example, the light-emitting portion 104a includes an array 502 of light-emitting elements. According to this example, the array 502 of light-emitting elements includes at least five individual light-emitting elements 515. In some examples, the array 502 of light-emitting elements may be a two-dimensional array of individual light-emitting elements 515. The light-emitting elements 515 may include, for example, light-emitting diodes, laser diodes, VCSELs, edge-emitting lasers, neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers, or combinations thereof. The light source system 104 including the array 502 of light-emitting elements is particularly advantageous for embodiments that also include an array 202 of ultrasonic receiver elements. The array 502 of light-emitting elements can illuminate a larger portion of the target object than a single light-emitting element. Furthermore, compared to a single light-emitting element, the array 502 of light-emitting elements provides a greater variety of light trajectories traveling within the target object and a greater variety of ultrasonic trajectories generated by photoacoustic effects traveling within the target object. In this example, lens 104b is configured to focus the light 503 emitted by the light-emitting portion 104a onto a relatively small cross-sectional area, which increases the intensity of the light 503 received by the target object (such as finger 115) on the outer surface 508a. Although Figure 5A The light-emitting portion 104a and the lens 104b are shown to be separated by a gap, but the light-emitting portion 104a and the lens 104b will generally be positioned adjacent to each other.

[0087] In this example, the pressure plate 101 includes a pressure plate portion 101a and a pressure plate portion 101b. According to this example, the pressure plate portion 101a has a thickness T1, which is less than the thickness T1 of the pressure plate portion 101b. In this example, the pressure plate portion 101a includes a surface 508b, which is configured to receive light 503 from the light source system 104. Although... Figure 5A The illustration shows a gap separating the light source system 104 from the surface 508b, but in some examples, the light source system 104 will be positioned adjacent to the surface 508b without a gap. According to this example, the pressure plate portion 101a is configured to direct light 503 from the light source system 104 to the outer surface 508a and to a target object (if any) on the outer surface 508a.

[0088] According to this example, pressure plate 101 (more specifically, pressure plate portion 101a) and light source system 104 are configured to transmit light 503 from light source system 104 along a first axis or substantially along a first axial direction to the outer surface 508a of pressure plate 101, the first axis being oriented at a first angle relative to the outer surface 508a. Figure 5AIn this example, axis 505a is an example of a first axis, and angle Θ1 is an example of a first angle. In this context, "substantially along the first axis" or "substantially parallel to the first axis" can mean within an angle range of ±10 degrees, ±15 degrees, ±20 degrees, ±25 degrees, ±30 degrees, or other such angle ranges along the first axis. According to this example, axis 505a is perpendicular to surface 508b.

[0089] In this example, receiver system 102 (an ultrasound receiver system in this embodiment) is positioned on surface 508c adjacent to pressure plate 101 (more specifically, pressure plate portion 101b). According to this example, receiver system 102 includes an array 202 of ultrasound receiver elements disposed in a receiver plane 510 oriented parallel to surface 508c. In this example, the array 202 of ultrasound receiver elements includes at least a linear array of active ultrasound receiver elements 215. In some examples, the array 202 of ultrasound receiver elements may include a two-dimensional array of active ultrasound receiver elements 215. In this example, the normal to receiver plane 510 is oriented along a second axis, which in this example is axis 505b, oriented at a second angle relative to outer surface 508a. Figure 5A In the example, angle Θ2 is a second angle. In this example, the receiver plane 510 is parallel to the outer surface 508a, so angle Θ2 is 90 degrees.

[0090] According to this example, pressure plate 101 (more specifically, pressure plate portion 101b) is configured to guide acoustic waves (including photoacoustic waves PA) emitted by a target object on outer surface 508a to receiver system 102. In this example, pressure plate 101 (more specifically, pressure plate portion 101b) is configured to transmit acoustic waves (including but not limited to ultrasonic waves) generated by the target object on outer surface 508a toward receiver system 102 along or substantially along a third axis oriented at a third angle relative to outer surface 508a. Figure 5AIn this example, axis 505c is an example of a third axis, and angle Θ3 is an example of a third angle. In this context, "substantially along the third axis" or "substantially parallel to the third axis" can mean within an angle range of ±10 degrees, ±15 degrees, ±20 degrees, ±25 degrees, ±30 degrees, or other such angle ranges. According to this example, the pressure plate portion 101b is shown transmitting arterial photoacoustic waves PA substantially along axis 505c. In this example, the second axis is parallel to or substantially parallel to the third axis (e.g., within a parallel range of + / - 5 degrees, within a parallel range of + / - 10 degrees, within a parallel range of + / - 15 degrees, within a parallel range of + / - 20 degrees, etc.).

[0091] In this example, the third axis is not parallel to the first axis, but rather separated from it by an angle (Θ3-Θ1). In some examples, the angle (Θ3-Θ1) can range from 20 degrees to 60 degrees. According to some alternative examples, the third axis can be parallel to the first axis. However, in some alternative examples, the first axis can be parallel to or substantially parallel to the third axis (e.g., within + / - 5 degrees of parallelism, within + / - 10 degrees of parallelism, within + / - 15 degrees of parallelism, within + / - 20 degrees of parallelism, etc.).

[0092] In some examples, the first, second, and third axes can be defined by a coordinate system relative to equipment 100 or a portion thereof. Figure 5A In the example shown, the Cartesian coordinate system is shown as defined relative to the outer surface 508a of the pressure plate 101.

[0093] In this example, axis 505d is parallel to outer surface 508a. An angle Θ4 is shown between axis 505d and surface 508b, indicating that the angle between surface 508b and outer surface 508a is also Θ4. According to this example, Θ4 = Θ3 - Θ1.

[0094] In some embodiments, the pressure plate 101 (e.g., at least a portion of the pressure plate portion 101b) may include an acoustic waveguide. In some such embodiments, the pressure plate portion 101b may be configured to transmit ultrasonic waves generated by a target object on the outer surface 508a toward the receiver system 102 via the acoustic waveguide.

[0095] 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 be placed on or near the pressure plate 101, for example, on or near the outer surface 508a.

[0096] Figure 5BExample components of an apparatus according to some alternative embodiments are shown. (This is in conjunction with other appendices provided herein.) Figure 1 Sample, Figure 5B The number, type, and arrangement of the components shown are merely illustrative. In this example, equipment 100 is... Figure 1 The example shown is of equipment 100.

[0097] In this example, receiver stack portion 102a includes ultrasound receiver elements 215a, 215b, 215c, and 215d, and a backing layer 580a. Here, receiver stack portion 102b includes ultrasound receiver elements 215e, 215f, 215g, and 215h, and a backing layer 580b. According to some embodiments, ultrasound receiver elements 215a-215d may be elements of a linear or two-dimensional array, and ultrasound receiver elements 215e-215h may be elements of other linear or two-dimensional arrays. However, in some embodiments, ultrasound receiver elements 215a and 215h may be portions of the same ultrasound receiver element ring. In some such embodiments, ultrasound receiver elements 215b and 215g may be portions of a second ultrasound receiver element ring, ultrasound receiver elements 215c and 215f may be portions of a third ultrasound receiver element ring, and ultrasound receiver elements 215d and 215e may be portions of a fourth ultrasound receiver element ring.

[0098] Backing layers 580a and 580b can be configured to suppress at least some acoustic artifacts and can provide a relatively higher signal-to-noise ratio (SNR) than receiver system 102 without backing layers. In some examples, backing layers 580a and 580b may comprise metal, epoxy resin, or a combination thereof.

[0099] As described elsewhere in this document, some embodiments of the equipment 100 include one or more elements configured for noise reduction. These noise reduction elements can be considered as references. Figure 1 The noise reduction system 110 is described as a part. However, such noise reduction elements can be placed in various parts of the equipment 100.

[0100] One type of noise that can exist in equipment 100 involves noise from light source system 104 (such as from...) Figure 5B The light from the light guide component 540 to the receiver system 102 leaks. Figure 5BThe example shown includes a light-mitigating element 555a disposed between a light guide assembly 540 and a receiver stack portion 102a, and a light-mitigating element 555b disposed between the light guide assembly 540 and the receiver stack portion 102b. In this example, light-mitigating elements 555a and 555b are also disposed between the light guide assembly 540 and mirror layers 565a and 565b, matching layers 570a and 570b, and adhesive layers 575a and 575b. In some examples, light-mitigating elements 555a and 555b may be discrete elements, while in other examples, they may be portions of a continuous element, such as a cylinder surrounding the light guide assembly 540. In some examples, light-mitigating elements 555a and 555b may comprise a material with a relatively low refractive index, such as a low-refractive-index foam. In this example, light-mitigating elements 555a and 555b are configured to increase optical coupling and reduce optical loss.

[0101] Another type of noise that can exist in the equipment 100 involves EMI from the light source system circuit 517, which can be received by the receiver system 102. Figure 5B In the example shown, the apparatus 100 includes an EMI-reducing element 560a near the receiver stack portion 102a and an EMI-reducing element 560b near the receiver stack portion 102b. In some examples, the EMI-reducing elements 560a and 560b may include one or more types of EMI shielding materials. According to some examples, the EMI-reducing elements 560a and 560b may be portions of a continuous element, such as a cylinder. In this example, the EMI-reducing element 560c is positioned between the light source system circuitry 517 and the receiver stack portions 102a and 102b. In some examples, the EMI-reducing element 560c may surround the light source system circuitry 517.

[0102] according to Figure 5B In the example shown, apparatus 100 includes an optical coupling component 511 configured to couple light from light-emitting component 535 to light-guiding component 540. In this example, optical coupling component 511 has a frustoconical outer surface 513. According to this example, optical coupling component 511 is partially positioned between receiver stack portions 102a and 102b and light-guiding component 540 to reduce the overall thickness of apparatus 100 along the z-axis. Although some other disclosed embodiments are not shown as having optical coupling components, alternative examples of such disclosed embodiments may indeed include one or more optical coupling components.

[0103] Figure 6An example of equipment configured to perform a receiver-side beamforming process is shown. In this example, the receiver-side beamforming process is a delay-summation beamforming process. Similar to other disclosed examples, Figure 6 The types, quantities, sizes, and arrangements of the elements shown and described herein, as well as the associated methods, are merely examples.

[0104] In this example, a source emitting ultrasonic waves 305 is shown, which are detected by active ultrasonic receiver elements 215a, 215b, and 215c of an array 202 of ultrasonic receiver elements. The array 202 of ultrasonic receiver elements is part of an ultrasonic receiver system 102. In some examples, ultrasonic waves 305 may correspond to the photoacoustic response of a target object to light emitted by a light source system 104 of the apparatus 100. In this example, active ultrasonic receiver elements 215a, 215b, and 215c provide ultrasonic receiver signals 615a, 615b, and 615c to the control system 106, respectively.

[0105] According to this example, the control system 106 includes a delay module 605 and a summing module 610. In this example, the delay module 605 is configured to determine whether a delay should be applied to each of the ultrasound receiver signals 615a, 615b, and 615c, and if so, what delay should be applied. According to this example, the delay module 605 determines that a delay d0 of t2 should be applied to ultrasound receiver signal 615a, a delay d1 of t1 should be applied to ultrasound receiver signal 615b, and no delay should be applied to ultrasound receiver signal 615c. Therefore, the delay module 605 applies the delay of t2 to ultrasound receiver signal 615a to produce ultrasound receiver signal 615a', and applies the delay of t1 to ultrasound receiver signal 615b to produce ultrasound receiver signal 615b'.

[0106] In some examples, delay module 605 can determine the delay (if any) to be applied to the ultrasound receiver signals by performing a correlation operation on the input ultrasound receiver signals. For example, delay module 605 can perform a correlation operation on ultrasound receiver signals 615a and 615c, and can determine that by applying a time shift of t2 to ultrasound receiver signal 615a, ultrasound receiver signal 615a will be strongly correlated with ultrasound receiver signal 615c. Similarly, delay module 605 can perform a correlation operation on ultrasound receiver signals 615b and 615c, and can determine that by applying a time shift of t1 to ultrasound receiver signal 615b, ultrasound receiver signal 615b will be strongly correlated with ultrasound receiver signal 615c.

[0107] According to this example, the summing module 610 is configured to sum the ultrasound receiver signals 615a', 615b', and 615c to produce a summed signal 620. It can be observed that the amplitude of the summed signal 620 is greater than the amplitude of any one of the ultrasound receiver signals 615a, 615b, or 615c. In some instances, the signal-to-noise ratio (SNR) of the summed signal 620 may be greater than the SNR of any one of the ultrasound receiver signals 615a, 615b, or 615c.

[0108] Figure 7A , Figure 8A and Figure 9A An apparatus with photoacoustic volumetric plethysmography (PAPG) capability is shown, along with examples of arteries in three different locations relative to the apparatus. Figure 7B , Figure 8B and Figure 9B They are shown respectively in Figure 7A , Figure 8A and Figure 9A The image data shown is an example of image data obtained by equipment with PAPG capability in the case of artery location.

[0109] exist Figure 7A , Figure 8A and Figure 9A In the examples shown, the equipment 100 includes a pressure plate 101, a light source system 104, and an ultrasound receiver system 102 with an array 202 of ultrasound receiver elements. In these examples, the array 202 of ultrasound receiver elements has six movable ultrasound receiver elements 215 disposed in a receiver plane 510. In these examples, the movable ultrasound receiver elements 215 are numbered from 1 to 6. According to these examples, the central axis 710 of the array 202 of ultrasound receiver elements is perpendicular to the receiver plane 510. In these examples, arteries 225e, 225f, and 225g are all 2 mm in diameter and are located within a target object 705 in contact with the equipment 100. For simplicity, the target object 705 is... Figure 7A , Figure 8A and Figure 9A The middle element is represented as a rectangle. As with other publicly available examples, Figure 7A , Figure 8A and Figure 9A The types, quantities, sizes, and arrangements of the elements shown and described herein are merely examples.

[0110] Figure 7B , Figure 8B and Figure 9B It shows the relationship with the source Figure 7A , Figure 8A and Figure 9A A graph showing the image data corresponding to the signals from the array 202 of the ultrasound receiver elements. In these examples, numbers 1-6 along the vertical axis correspond to signals from... Figure 7A , Figure 8A and Figure 9A The signals from the active ultrasound receiver elements 215, numbered 1-6, correspond to each other. Number 7 on the vertical axis represents the summation of signals from receiver elements 1-6. Number 8 on the vertical axis represents the output of the Delayed Summation (DAS) process, as described in this document's references. Figure 6 What has been made public.

[0111] exist Figure 7A In this context, artery 225e is located 3 mm from the central axis in the negative x-direction. In other words, the center of artery 225e has an x-coordinate of -3 mm relative to coordinate system 715.

[0112] Figure 7B Image data including the signal corresponding to artery 225e is shown. Reference numeral 720a indicates the signal from receiver element 1 corresponding to artery 225e, and reference numeral 720b indicates the signal from receiver element 6 corresponding to artery 225e. Although it can be easily observed... Figure 7B These representations of the arterial signals in the image, as well as the representations of the arterial signals from receiver elements 2-5, are shown. However, the representation of the arterial signals shown in row 8 is more pronounced after the DAS process, exhibiting higher amplitude and a higher SNR. Conversely, as shown in row 7, averaging only the signals from receiver elements 1-6 reduces the amplitude of the represented arterial signals.

[0113] It can also be observed that the individual representations of the arterial signals from receiver elements 1-6 shown in rows 1-6 provide information about the location of artery 225e. Since the arterial signal is first received by receiver element 1 and last received by receiver element 6, it is obvious that artery 225e is closest to receiver element 1 and farthest from receiver element 6.

[0114] exist Figure 8A In the middle, the center of artery 225f is located on the central axis 710. Figure 8B Image data including signals corresponding to artery 225f is shown. Reference numeral 820a indicates the signal from receiver element 1 corresponding to artery 225f, and reference numeral 820b indicates the signal from receiver element 6 corresponding to artery 225f. Although it is possible to... Figure 8B We see these representations of arterial signals, as well as representations of arterial signals from receiver elements 2-5, but the representation of arterial signals shown in row 8 has a higher amplitude and a higher SNR. Again, as shown in row 7, simply averaging the signals from receiver elements 1-6 reduces the amplitude of the represented arterial signals.

[0115] The separate representations of the arterial signals from receiver elements 1-6 shown in rows 1-6 also provide information about the location of artery 225f. Since the arterial signals are first received by receiver elements 3 and 4 and last received by receiver elements 1 and 6, it is obvious that artery 225e is on or near the central axis 710.

[0116] exist Figure 9A In the middle, artery 225g is located 710.3 mm away from the central axis in the positive x direction. Figure 9B Image data including signals corresponding to artery 225g is shown. Reference numeral 920a indicates the signal from receiver element 1 corresponding to artery 225g, and reference numeral 920b indicates the signal from receiver element 6 corresponding to artery 225g. Figure 7B and Figure 8B In the example shown, the representation of the arterial signal in row 8 is more pronounced after the DAS process. However, as shown in row 7, averaging only the signals from receiver elements 1-6 reduces the amplitude of the represented arterial signal.

[0117] Furthermore, the individual representation of the arterial signal from receiver elements 1-6 provides information about the location of artery 225g. Since the arterial signal is received first by receiver element 6 and last by receiver element 1, it is obvious that artery 225g is closest to receiver element 6 and farthest from receiver element 1.

[0118] Figure 10 This is a flowchart illustrating examples of some publicly disclosed operations. For example, Figure 10 The box can be made of Figure 1 The equipment 100 or similar equipment performs the operation. Similar to other methods disclosed herein, Figure 10 The methods outlined herein may include more or fewer boxes than indicated. Furthermore, the boxes in the methods disclosed herein are not necessarily executed in the indicated order. In some instances, Figure 10 One or more boxes shown can be executed simultaneously.

[0119] In this example, block 1005 relates to a control system controlling a light source system to provide light to a target object on the outer surface of a pressure plate. Depending on the specific example, the target object could be a finger, wrist, etc. According to this example, block 1010 relates to a control system receiving an ultrasonic receiver signal from each of a plurality of ultrasonic receiver elements in an array of ultrasonic receiver elements. In this example, the ultrasonic receiver signal corresponds to an ultrasonic wave generated by the target object in response to light from the light source system.

[0120] According to this example, block 1015 relates to applying a receiver-side beamforming process to an ultrasound receiver signal by a control system to produce a beamformed ultrasound receiver image. In some examples, the receiver-side beamforming process may be or may include a delay-and-sum beamforming process. For example, block 1015 may relate to, as referenced... Figure 6 The process described above. Other examples may involve other types of beamforming. In some such examples, beamforming may be based on algorithms developed according to machine learning techniques, such as machine learning techniques based on raw data corresponding to signals generated by individual ultrasound receiver elements.

[0121] In this example, block 1020 relates to detecting blood vessels within a target object by a control system based at least in part on beamforming ultrasound receiver images. In some examples, method 1000 may involve detecting blood vessels within a target object based at least in part on ultrasound receiver signals.

[0122] For example, blood vessels can be detected based on a time window corresponding to the speed of sound within a expected range of depths through the vessel. Alternatively or additionally, blood vessels can be detected based on one or more characteristics of the photoacoustic response of the blood within the vessel, the vessel wall, or a combination thereof.

[0123] In some examples, method 1000 may involve estimating one or more vascular features based at least in part on beamforming ultrasound receiver images. The 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. In some examples, the one or more vascular features may be arterial features. In some examples, method 1000 may involve estimating one or more cardiac features based at least in part on one or more vascular features. According to some such examples, method 1000 may involve estimating blood pressure based at least in part on one or more vascular features. According to some examples, method 1000 may involve extracting and evaluating heart rate waveform (HRW) features.

[0124] Figure 11 It shows that according to Figure 10 Examples of some implementations of the method that can extract heart rate waveform (HRW) features. Figure 11The 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 time interval between systole and diastole is indicated below the horizontal axis. During the systolic phase of the cardiac cycle, 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. With expansion comes a corresponding increase in the volume of blood at that specific location or region, and with this increase in blood volume comes a associated change in one or more properties of the region. Conversely, during the diastolic phase of the cardiac cycle, blood pressure in the artery decreases, and the arterial wall constricts. With constriction comes a corresponding decrease in the volume of blood at that specific location, and with this decrease in blood volume comes a associated change in one or more properties of the region.

[0125] Figure 11 The HRW features shown relate to the width of the contraction and / or diastolic portions of the HRW curve at different "heights" indicated by the percentage of maximum amplitude. For example, the SW50 feature is the width of the contraction portion of the HRW curve at 50% of the maximum amplitude "height". In some embodiments, the HRW features used for blood pressure estimation may include some or all of the HRW features SW10, SW25, SW33, SW50, SW66, SW75, DW10, DW25, DW33, DW50, DW66, and DW75. In other embodiments, additional HRW features may be used for blood pressure estimation. In some instances, such additional HRW features may include the sum and ratio of SW and DW at one or more “heights,” for example, (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 other HRW features for blood pressure estimation. In some instances, such additional HRW features may include sums, differences, ratios, and / or other operations based on more than one “height,” such as (DW75+SW75) / (DW50+SW50), (DW50+SW50) / (DW10+SW10), etc.

[0126] Figure 12 An example device is shown that can be used in a system for estimating blood pressure based at least in part on pulse conduction time (PTT). (This is in conjunction with other appendices provided herein.) Figure 1The number, type, and arrangement of components are presented by way of example only. According to this example, system 1200 includes at least two sensors. In this example, system 1200 includes at least an electrocardiogram sensor 1205 and a device 1210 configured to be mounted on a finger of a person 1201. In this example, device 1210 is or includes an apparatus configured to perform at least some of the PAPG methods disclosed herein. For example, device 1210 may be or may include the apparatus 300 of FIG. 3 or a similar apparatus.

[0127] As shown in graph 1220, PAT comprises two parts: the pre-ejection period (PEP, the time required to convert the electrical signal into mechanical pumping force and isovolute contraction to open the aortic valve) and PTT. The onset time of PAT can be estimated based on the QRS complex (the electrical signal characteristics of ventricular electrical stimulation). As shown in graph 1220, in this example, the start of the pulse arrival time (PAT) can be calculated based on the R-wave peak measured by ECG sensor 1205, and the end of PAT can be detected via a signal provided by analysis device 1210. In this example, it is assumed that the end of PAT corresponds to the intersection between the tangent of the local minimum detected by device 1210 and the tangent of the maximum slope / first derivative of the sensor signal after the minimum time.

[0128] There are many known algorithms for blood pressure estimation based on PTT and / or PAT, some of which are outlined in Table 1 of Sharma, M, et al., “Cuffless and Continuous Blood Pressure Monitoring: A Review of Methods” (“Sharma”), published by the Multidisciplinary Digital Publishing Institute (MDPI) Technology 2017, 5, 21, and the corresponding text on pages 5–10, both of which are incorporated herein by reference.

[0129] Some previously disclosed methods involve calculating blood pressure based on PTT and / or PAT measured by a sensor system including a PPG sensor, according to one or more of the equations shown in Sharma's Table 1 or other known equations. As mentioned above, some disclosed PAPG-based implementations are configured to distinguish arterial HRW from other HRWs. Compared to those measured by PPG sensors, such implementations can provide more accurate measurements of PTT and / or PAT. Therefore, the disclosed PAPG-based implementations can provide more accurate blood pressure estimates, even if the blood pressure estimate is based on previously known formulas.

[0130] Other embodiments of system 1200 may exclude the electrocardiogram sensor 1205. In some such embodiments, device 1215, configured to be mounted on the wrist of a person 1201, may be or may include an apparatus configured to perform at least some of the PAPG methods disclosed herein. For example, device 1215 may be or may include apparatus 200 of FIG. 2 or similar apparatus. According to some such examples, device 1215 may include a light source system and two or more ultrasound receivers. Reference is made below. Figure 14A Describe an example. In some examples, device 1215 may include an array of ultrasound receivers.

[0131] In some embodiments of system 1200 that do not include electrocardiogram sensor 1205, device 1210 may include a light source system and two or more ultrasound receivers. (Refer to below) Figure 14B Describe an example.

[0132] Figure 13 A schematic cross-sectional side view of a portion of the artery 1300 through which the pulse 1302 propagates is shown. Figure 13 The boxed arrows in the figure indicate the direction of blood flow and pulse propagation. As shown, the propagating pulse 1302 causes strain in the arterial wall 1304, which manifests as an increase in the diameter (and therefore the cross-sectional area) of the arterial wall—a phenomenon known as "distension." The actual spatial length L of the propagating pulse along the artery (in the direction of blood flow) is typically comparable to the length of a limb, such as the distance from the subject's shoulder to their wrist or fingers, and is usually less than one meter (m). However, the length L of the propagating pulse varies considerably among subjects and can vary significantly over time for a given subject, depending on various factors. The spatial length L of the pulse generally decreases with increasing distance from the heart until the pulse reaches the capillaries.

[0133] As described above, certain embodiments relate to devices, systems, and methods for estimating blood pressure or other cardiovascular characteristics based on the estimation of arterial dilation waveforms. Unless otherwise stated, the terms “estimate,” “measure,” “calculate,” “infer,” “infer,” “evaluate,” “determine,” and “monitor” are used interchangeably herein where appropriate. Similarly, derivatives of these terminological roots are also used interchangeably where appropriate; for example, the terms “to estimate,” “to measure,” “to calculate,” “to infer,” and “to determine” are also used interchangeably herein. In some embodiments, the pulse wave velocity (PWV) of a propagating pulse can be estimated by measuring the pulse conduction time (PTT) of the pulse as it travels from a first physical location along the artery to a more distant second physical location 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. If it is deterministic, then PWV can be estimated as the physical spatial distance the pulse travels. Divide by the distance the pulse travels through physical space The quotient of the time taken (PTT). Typically, a first sensor located at a first physical location is used to determine the start time (also referred to herein as the "first time location") at which the pulse arrives or propagates through the first physical location. A second sensor at a second physical location is used to determine the end time (also referred to herein as the "second time location") at which the pulse arrives or propagates through the second physical location and continues through the remainder of the arterial branch. In such an example, PTT represents the time distance (or time difference) between the first time location and the second time location (start and end times).

[0134] The fact that arterial dilation waveform measurements are performed at two different physical locations means that the estimated PWV inevitably represents the entire path distance traveled by the pulse between the first and second physical locations. The average value is calculated based on the mean. More specifically, PWV typically depends on many factors, including blood density. arterial wall stiffness (Or conversely, elasticity), arterial diameter, arterial wall thickness, and blood pressure. Because 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). (Average above).

[0135] In conventional methods for obtaining pulse wave velocity (PWV), an electrocardiogram (ECG) sensor is used to obtain the pulse start time at the heart, detecting electrical signals from the heart. For example, the start time can be estimated based on the QRS complex (the electrical signal characteristics of ventricular electrical stimulation). In this method, different sensors located at a secondary location (e.g., the finger) are typically used to obtain the pulse end time. As those skilled in the art will understand, there are numerous arterial discontinuities, branches, and variations along the entire path from the heart to the finger. PWV can vary by up to or more than an order of magnitude along different segments of the entire path from the heart to the finger. Therefore, PWV estimation based on such a long path length is unreliable.

[0136] In the various embodiments described herein, PTT estimates are obtained based on measurements associated with an arterial dilation signal (also referred to as “arterial dilation data” or more generally, “sensor data”), obtained by each of a first arterial dilation sensor 1306 and a second arterial dilation sensor 1308, respectively, located near a first physical location and a second physical location along the artery of interest. In some specific embodiments, the first arterial dilation sensor 1306 and the second arterial dilation sensor 1308 are advantageously positioned near the first and second physical locations, between which arterial properties of the artery of interest (such as wall elasticity and diameter) can be considered or assumed to be relatively constant. Thus, the PWV calculated based on the PTT estimate is more representative of the actual PWV along a specific segment of the artery. In turn, the blood pressure estimated based on the PWV... This provides a more accurate representation of actual blood pressure. In some implementations, the separation distance between the first arterial dilation sensor 1306 and the second arterial dilation sensor 1308... The magnitude of the pulse (and thus the distance between the first and second locations along the artery) can range from about 1 centimeter (cm) to several tens of centimeters—long enough to distinguish the pulse reaching the first physical location from the pulse reaching the second physical location, but close enough to provide sufficient assurance of arterial consistency. In some specific embodiments, the distance between the first arterial dilation sensor 1306 and the second arterial dilation sensor 1308... The distance can range from about 1 cm to about 30 cm, and in some embodiments, it is less than or equal to about 20 cm, and in some embodiments, it is less than or equal to about 10 cm, and in some specific embodiments, it is less than or equal to about 5 cm. In some other embodiments, the distance between the first arterial dilation sensor 1306 and the second arterial dilation sensor 1308... The distance 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. A dynamic monitoring device using the first arterial dilation sensor 1306 and the second arterial dilation sensor 1308 separated by a distance of about 5 cm and assuming a PWV of about 15 m / s means a PTT of about 3.3 ms.

[0137] The distance between the first arterial dilation sensor 1306 and the second arterial dilation sensor 1308 The values ​​can be pre-programmed into the memory of the monitoring device incorporated into the sensors (e.g., the memory of the control system 306 described above with reference to FIG3, or a memory configured to communicate with the control system 306). As those skilled in the art will understand, in this embodiment, the spatial length L of the pulse can be greater than the distance from the first arterial dilation sensor 1306 to the second arterial dilation sensor 1308. Thus, although Figure 13 The illustrated pulse 1302 is shown to have a spatial length L equivalent to the distance between the first arterial dilation sensor 1306 and the second arterial dilation sensor 1308, but in reality, each pulse can typically have a greater spatial length than the distance between the first arterial dilation sensor 1306 and the second arterial dilation sensor 1308. Larger or even much larger (e.g., about an order of magnitude or more) spatial lengths L.

[0138] Sensing architecture and topology

[0139] In some embodiments of the dynamic monitoring device disclosed herein, both the first arterial dilation sensor 1306 and the second arterial dilation sensor 1308 are sensors of the same type. In some such embodiments, the first arterial dilation sensor 1306 and the second arterial dilation sensor 1308 are identical sensors. In such embodiments, each of the first arterial dilation sensor 1306 and the second arterial dilation sensor 1308 utilizes the same sensor technology, has the same sensitivity to arterial dilation signals caused by propagating pulses, and has the same time delay and sampling characteristics. In some embodiments, each of the first arterial dilation sensor 1306 and the second arterial dilation sensor 1308 is configured for photoacoustic volumetric plethysmography (PAPG) sensing, for example, as disclosed elsewhere herein. Some such embodiments include a light source system and two or more ultrasound receivers, which may be examples of the light source system 304 and receiver system 302 of FIG. 3. In some embodiments, each of the first arterial dilation sensor 1306 and the second arterial dilation sensor 1308 is configured for ultrasound sensing via transmitting ultrasound signals and receiving corresponding reflections. In some alternative embodiments, each of the first arterial dilation sensor 1306 and the second arterial dilation sensor 1308 can be configured for impedance plethysmography (IPG) sensing, also known in the biomedical context as bioimpedance sensing. In various embodiments, regardless of the type of sensor used, each of the first arterial dilation sensor 1306 and the second arterial dilation sensor 1308 is broadly designed to capture and provide arterial dilation data indicative of an arterial dilation signal generated by the propagation of a pulse at a portion of the artery near which the respective sensor is positioned. For example, the arterial dilation data can be provided from the sensor to the processor in the form of a voltage signal generated or received by the sensor based on an ultrasound signal or impedance signal sensed by the respective sensor.

[0140] As described above, during the systolic phase of the cardiac cycle, 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. This expansion corresponds to a increase in the volume of blood at that specific location or region, and with this increase in blood volume comes a associated change in one or more properties of the region. Conversely, during the diastolic phase of the cardiac cycle, blood pressure in the artery decreases, and the arterial wall constricts. This constriction corresponds to a decrease in the volume of blood at that specific location, and with this decrease in blood volume comes a associated change in one or more properties of the region.

[0141] In the context of bioimpedance sensing (or impedance plethysmography), blood in an artery has a higher electrical conductivity than the surrounding or adjacent skin, muscle, fat, tendons, ligaments, bone, lymph, or other tissues. The susceptance (and 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 the volume of blood at that location leads to an increase in conductivity (and more generally, an increase in admittance, or equivalently, a decrease in impedance). Conversely, during the diastolic phase of the cardiac cycle, the corresponding decrease in the volume of blood at a particular location leads to an increase in resistivity (and more generally, an increase in impedance, or equivalently, a decrease in admittance).

[0142] Bioimpedance sensors typically function by applying an electrical excitation signal at an excitation carrier frequency to a region of interest via two or more input electrodes and detecting an output signal (or multiple output signals) via two or more output electrodes. In some more specific embodiments, the electrical excitation signal is a current signal injected into the region of interest via the input electrodes. In some such embodiments, the output signal is a voltage signal 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 instances time-varying, electrical properties of the various tissues through which the injected excitation current signal passes. In some embodiments where the bioimpedance sensor is operable for monitoring blood pressure, heart rate, or other cardiovascular characteristics, the detected voltage response signal is amplitude and phase modulated by the time-varying impedance (or conversely, admittance) of the underlying artery, which, as described above, 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.

[0143] In some examples incorporating ultrasound sensors, the measurement of arterial dilation may involve (e.g., via one or more ultrasound transducers) introducing ultrasound waves toward the artery into the limb. Such ultrasound sensors are also configured to receive waves, at least in part based on reflections of the introduced waves. The reflected waves may include scattered waves, specularly reflected waves, or both. The reflected waves provide information about the arterial wall, and therefore, information about arterial dilation.

[0144] In some embodiments, regardless of the type of sensor used for the first arterial dilation sensor 1306 and the second arterial dilation sensor 1308, both the first arterial dilation sensor 1306 and the second arterial dilation sensor 1308 can be arranged, assembled, or otherwise included within a single housing of a single dynamic monitoring device. As described above, the housing and other components of the monitoring device can be configured such that when the monitoring device is fixed or otherwise physically coupled to a subject, the first arterial dilation sensor 1306 and the second arterial dilation sensor 1308 contact or are adjacent to the user's skin at a first position and a second position, respectively, with a separation distance between the first position and the second position. Furthermore, in some embodiments, arterial properties along which the various arteries are located can be assumed to be relatively constant segments of arteries. In various embodiments, the housing of the dynamic monitoring device is a wearable housing, or is incorporated into or integrated with a wearable housing. In some specific embodiments, the wearable housing includes (or is connected to) a physical coupling mechanism for removable, non-invasive attachment to a user. The housing can be formed using any of a variety of suitable manufacturing processes, including injection molding and vacuum forming, etc. Moreover, the housing can be made of 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 are fully dynamic in use. In other words, some embodiments of the wearable monitoring devices 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 while the subject is moving or otherwise engaging in physical activity. In this way, dynamic monitoring devices are convenient and capable of being worn and monitored for extended periods (e.g., for days, weeks, or months or longer without interruption) for one or more biometrics of interest to obtain a better picture of these traits over the extended duration, and generally, a better picture of the user's health.

[0145] In some implementations, the motion monitoring device can be positioned by wrapping around the user's wrist with a strap or band similar to a watch or fitness / activity tracker. Figure 14AAn example dynamic monitoring device 1400 designed to be worn around the wrist, according to some embodiments, is shown. In the illustrated example, the monitoring device 1400 includes a housing 1402 integrally formed, coupled, or otherwise integrated with a wristband 1404. In some instances, a first arterial dilation sensor 1406 and a second arterial dilation sensor 1408 may each include portions of the ultrasound receiver system 302 and the light source system 304 described above with reference to FIG. 3. In this example, the dynamic monitoring device 1400 is coupled around the wrist such that the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408 within the housing 1402 are each positioned along a segment of the radial artery 1410 (note that when the monitoring device is coupled to a subject, the sensors are typically concealed from the view of the outer or outer surface of the housing facing the subject, but exposed on the inner surface of the housing to allow the sensors to obtain measurements from the underlying artery through the subject's skin). Also as shown, the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408 are separated by a fixed distance. In some other embodiments, the dynamic monitoring device 1400 may be similarly designed or adapted to be positioned using straps or bands around the forearm, upper arm, ankle, lower leg, thigh, or fingers (hereinafter referred to as "limbs").

[0146] Figure 14B An example dynamic monitoring device 1400 designed to be worn on a finger is shown according to some embodiments. In some instances, the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408 may each include portions of the ultrasound receiver 302 and the light source system 304 described above with reference to FIG3.

[0147] In some other embodiments, the dynamic monitoring device disclosed herein can be positioned on an area of ​​interest to the user without the use of straps or bands. For example, the first arterial dilation sensor 1406 and the second arterial dilation sensor 1408, along with other components of the monitoring device, can be encapsulated in a housing that is secured to the skin of the area of ​​interest to the user using an adhesive or other suitable attachment mechanism (an example of a "patch" monitoring device).

[0148] Figure 14C An example motion monitoring device 1400, designed to be placed on an earplug according to some embodiments, is shown. According to this example, the motion monitoring device 1400 is coupled to the housing of an earplug 1420. In some instances, a first arterial dilation sensor 1406 and a second arterial dilation sensor 1408 may each include portions of the ultrasound receiver 302 and the light source system 304 described above with reference to FIG. 3.

[0149] Examples of implementation methods are described in the following numbered clauses:

[0150] 1. 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; an ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to light from the light source system, the ultrasonic receiver system including an array of ultrasonic receiver elements; and a control system configured to: receive an ultrasonic receiver signal from each of a plurality of ultrasonic receiver elements in the array; apply a receiver-side beamforming process to the ultrasonic receiver signal to generate a beamformed ultrasonic receiver image; and detect blood vessels within the target object based at least in part on the beamformed ultrasonic receiver image.

[0151] 2. The equipment according to Clause 1, wherein the control system is configured to detect blood vessels within a target object based at least in part on ultrasound receiver signals.

[0152] 3. The equipment according to Clause 1 or Clause 2, wherein the control system is further configured to estimate one or more vascular features based at least in part on beamforming ultrasound receiver images.

[0153] 4. The equipment according to Clause 3, 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.

[0154] 5. The equipment according to Clause 3 or Clause 4, wherein the control system is further configured to estimate blood pressure based at least in part on the one or more vascular features.

[0155] 6. The equipment according to any one of Clauses 1-5, wherein the light source system comprises an array of light sources.

[0156] 7. The equipment according to any one of Clauses 1-6, wherein the equipment is configured to be worn or attached to a person.

[0157] 8. The apparatus according to Clause 7, wherein the array of ultrasound receiver elements comprises a linear array of ultrasound receiver elements arranged along an array axis configured to extend along a blood vessel, and wherein the array axis is within ±45 degrees of the blood vessel axis.

[0158] 9. The apparatus according to Clause 7, wherein the array of ultrasound receiver elements comprises a linear array of ultrasound receiver elements arranged along an array axis configured to extend through a blood vessel.

[0159] 10. The apparatus according to any one of Clauses 1-9, wherein the array of ultrasonic receiver elements comprises a linear array of ultrasonic receiver elements having a spacing between adjacent ultrasonic receiver elements equal to the wavelength corresponding to the peak frequency of an ultrasonic wave generated by the target object in response to light from the light source system.

[0160] 11. The apparatus according to any one of Clauses 1-10, wherein the array of ultrasonic receiver elements comprises a phased array of ultrasonic receiver elements having a spacing between adjacent ultrasonic receiver elements equal to a multiple of half a wavelength corresponding to the peak frequency of an ultrasonic wave generated by the target object in response to light from the light source system.

[0161] 12. The apparatus according to any one of clauses 1-11, wherein the array of ultrasonic receiver elements comprises a two-dimensional array of ultrasonic receiver elements.

[0162] 13. The apparatus according to any one of clauses 1-12, wherein the array of ultrasonic receiver elements is or includes an array of electrodes arranged on a piezoelectric layer.

[0163] 14. The equipment as described in Clause 13, wherein the piezoelectric layer is or includes lead zirconate titanate (PZT) or a piezoelectric composite material.

[0164] 15. The equipment according to Clause 1, wherein the receiver-side beamforming process is or includes a delay and summation beamforming process.

[0165] 16. 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; an ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to light from the light source system, the ultrasonic receiver system including an array of ultrasonic receiver elements; and a control device for: receiving an ultrasonic receiver signal from each of a plurality of ultrasonic receiver elements in the array; applying a receiver-side beamforming process to the ultrasonic receiver signal to generate a beamformed ultrasonic receiver image; and detecting blood vessels within the target object based at least in part on the beamformed ultrasonic receiver image.

[0166] 17. The equipment according to Clause 16, wherein the control device includes means for detecting blood vessels within a target object based at least in part on ultrasound receiver signals.

[0167] 18. The apparatus according to Clause 16, wherein the control device includes means for estimating one or more vascular features based at least in part on an ultrasound receiver image of beamforming.

[0168] 19. The equipment according to Clause 18, wherein the one or more vascular features include vascular diameter, vascular dilation, volumetric flow rate, pulse wave velocity, vascular wall thickness, or a combination thereof.

[0169] 20. The equipment according to Clause 18, wherein the control device includes means for estimating blood pressure based at least in part on the one or more vascular features.

[0170] 21. A method comprising: controlling a light source system to provide light to a target object on an outer surface of a pressure plate by a control system; receiving an ultrasound receiver signal from each of a plurality of ultrasound receiver elements in an array of ultrasound receiver elements by the control system, the ultrasound receiver signal corresponding to an ultrasound wave generated by the target object in response to light from the light source system; applying a receiver-side beamforming process to the ultrasound receiver signal by the control system to generate a beamformed ultrasound receiver image; and detecting blood vessels within the target object by the control system based at least in part on the beamformed ultrasound receiver image.

[0171] 22. The method according to Clause 21 further includes detecting blood vessels within the target object based at least in part on ultrasound receiver signals.

[0172] 23. The method according to Clause 21 or Clause 22 further includes estimating one or more vascular features based at least in part on beamforming ultrasound receiver images.

[0173] 24. The method according to Clause 23, 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.

[0174] 25. The method described under Clause 23 or Clause 24 further includes estimating blood pressure based at least in part on the one or more vascular features.

[0175] 26. The method according to any one of clauses 21-25, wherein the receiver-side beamforming process includes a delay and summation beamforming process.

[0176] 27. One or more non-transitory media storing instructions for performing a method comprising: controlling a light source system to provide light to a target object on an outer surface of a pressure plate; receiving, by a control system, an ultrasound receiver signal from each of a plurality of ultrasound receiver elements in an array of ultrasound receiver elements, the ultrasound receiver signal corresponding to an ultrasound wave generated by the target object in response to light from the light source system; applying a receiver-side beamforming process to the ultrasound receiver signal to generate a beamformed ultrasound receiver image; and detecting blood vessels within the target object based at least in part on the beamformed ultrasound receiver image.

[0177] 28. One or more non-transitory media as described in Clause 27, wherein the method further includes detecting blood vessels within the target object based at least in part on ultrasound receiver signals.

[0178] 29. One or more non-transitory media as described in Clause 27 or Clause 28, wherein the method further comprises estimating one or more vascular features based at least in part on beamforming ultrasound receiver images.

[0179] 30. One or more non-transient media as described in Clause 29, 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.

[0180] 31. One or more non-transient media as described in Clause 29 or Clause 30, wherein the method further includes estimating blood pressure based at least in part on the one or more vascular features.

[0181] 32. One or more non-transient media according to any one of clauses 27-31, wherein the receiver-side beamforming process includes a delay and summation beamforming process.

[0182] As used in this article, the phrase "at least one" in a list of items refers to any combination of these items, including individual members. For example, "at least one of a, b, or c" is intended to cover a, b, c, ab, ac, bc, and abc.

[0183] The various illustrative logics, logic blocks, modules, circuits, and algorithmic processes described in conjunction with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or a combination of both. The interchangeability of hardware and software has been generally described in terms of functionality and is illustrated in the various illustrative components, blocks, modules, circuits, and processes described above. Whether this functionality is implemented in hardware or software depends on the specific application and the design constraints imposed on the entire system.

[0184] Hardware and data processing apparatuses that can implement or perform the various illustrative logics, logic blocks, modules, and circuits described in conjunction with the aspects disclosed herein can be implemented 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, discrete hardware components, or any combination thereof. 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 implementations, specific processes and methods can be performed by circuitry specific to a given function.

[0185] In one or more aspects, the described functionality can be implemented in hardware, digital electronic circuits, computer software, or firmware that includes the structures disclosed in this specification and their equivalents, or any combination thereof. Embodiments of the subject matter described in this specification can 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.

[0186] If implemented in software, functionality can be stored as one or more instructions or code on or transmitted on 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, which can be placed on a computer-readable medium. Computer-readable media include both computer storage media and communication media, encompassing any medium capable of transferring a computer program from one place 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, disk storage 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. Similarly, any connection can be properly referred to as a computer-readable medium. Disks and optical discs as used herein include compact optical discs (CDs), laser discs, optical discs, digital versatile optical discs (DVDs), floppy disks, and Blu-ray discs, where 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 be placed on a machine-readable and computer-readable medium as one of code and instructions or any combination of code and instructions or a collection of code and instructions, which may be incorporated into a computer program product.

[0187] Various modifications to the embodiments described in this disclosure will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not intended to be limited to the embodiments shown herein, but is intended to be accorded the widest scope consistent with the claims, principles, and novel features disclosed herein. The word “exemplary,” if used herein, is used only to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0188] Some features described in the context of individual embodiments in this specification 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 initially claimed in this way, one or more features from the claimed combination may be removed from the combination in some cases, and the claimed combination may lead to sub-combinations or variations thereof.

[0189] Similarly, although the operations are depicted in a specific order in the accompanying drawings, this should not be construed as requiring that such operations be performed in the specific order or sequence shown, or requiring that all the operations shown be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Furthermore, the separation of the various system components in the above embodiments should not be construed as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. In addition, other embodiments are also within the scope of the appended claims. In some cases, the actions recited in the claims can be performed in a different order and the desired result can still be achieved.

[0190] It should be understood that unless features in any particular described embodiment are explicitly identified as incompatible with each other, or the surrounding context suggests that they are mutually exclusive and not readily composable in terms of complementarity and / or supporting significance, this disclosure as a whole is contemplated and envisioned as allowing the selective combination of specific features of these complementary embodiments to provide one or more comprehensive but slightly different technical solutions. Therefore, it will be further understood that the above description is given by way of example only and modifications in detail may be made within the scope of this disclosure.

[0191] Various modifications to the embodiments described in this disclosure will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit or scope of the invention. Therefore, the appended claims are not intended to be limited to the embodiments shown herein, but are intended to be given the widest scope consistent with this disclosure, the principles disclosed herein, and the novel features.

[0192] Furthermore, some features described in the context of individual embodiments in this specification 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. Moreover, although features may be described above as operating in certain combinations, and even initially claimed in this way, one or more features from the claimed combination may be removed from the combination in some cases, and the claimed combination may lead to sub-combinations or variations of sub-combinations.

[0193] Similarly, although operations are depicted in a specific order in the accompanying drawings, this should not be construed as requiring that such operations be performed in the specific order or sequence shown, or requiring that all shown operations be performed to achieve the desired result. Furthermore, the drawings may schematically depict one or more example processes in the form of flowcharts. However, other operations not depicted may be incorporated into the schematically shown example processes. For example, one or more additional operations may be performed before, after, simultaneously with, or between any shown operations. Moreover, the various operations described and shown may themselves include, and collectively refer to, multiple sub-operations. For example, each of the operations described above may itself involve the execution of a process or algorithm. Furthermore, in some embodiments, the various operations described and shown may be combined or performed in parallel. Similarly, the separation of various system components in the above embodiments should not be construed as requiring such separation in all embodiments. Therefore, other embodiments are also within the scope of the appended 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 comprising: Pressure plate; A light source system is configured to provide light to a target object on the outer surface of the pressure plate; An ultrasonic receiver system is configured to receive ultrasonic waves generated by the target object in response to light from the light source system, the ultrasonic receiver system comprising an array of ultrasonic receiver elements; and The control system is configured as follows: An ultrasound receiver signal is received from each of the plurality of ultrasound receiver elements in the array; A receiver-side beamforming process is applied to the ultrasound receiver signal to generate a beamformed ultrasound receiver image; and Blood vessels within the target object are detected, at least in part, based on the beamformed ultrasound receiver image.

2. The equipment according to claim 1, wherein, The control system is configured to detect the blood vessels within the target object based at least in part on the ultrasound receiver signal.

3. The equipment according to claim 1, wherein, The control system is also configured to estimate one or more vascular features based at least in part on the beamformed ultrasound receiver image.

4. The equipment according to claim 3, 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.

5. The equipment according to claim 3, wherein, The control system is also configured to estimate blood pressure based at least in part on the one or more vascular features.

6. The equipment according to claim 1, wherein, The light source system includes an array of light sources.

7. The equipment according to claim 1, wherein, The equipment is configured to be worn or attached to a person.

8. The equipment according to claim 7, wherein, The array of ultrasound receiver elements comprises a linear array of ultrasound receiver elements arranged along an array axis configured to extend along the blood vessel, wherein the array axis is within ±45 degrees of the blood vessel axis.

9. The equipment according to claim 7, wherein, The array of ultrasound receiver elements comprises a linear array of ultrasound receiver elements arranged along an array axis configured to extend through the blood vessel.

10. The equipment according to claim 1, wherein, The array of ultrasonic receiver elements comprises a linear array of ultrasonic receiver elements having a spacing between adjacent ultrasonic receiver elements equal to the wavelength corresponding to the peak frequency of the ultrasonic wave generated by the target object in response to light from the light source system.

11. The equipment according to claim 1, wherein, The array of ultrasonic receiver elements comprises a phased array of ultrasonic receiver elements having a spacing between adjacent ultrasonic receiver elements equal to a multiple of half a wavelength corresponding to the peak frequency of the ultrasonic wave generated by the target object in response to light from the light source system.

12. The equipment according to claim 1, wherein, The array of ultrasonic receiver elements comprises a two-dimensional array of ultrasonic receiver elements.

13. The equipment according to claim 1, wherein, The array of ultrasonic receiver elements includes an array of electrodes arranged on a piezoelectric layer.

14. The equipment according to claim 13, wherein, The piezoelectric layer includes lead zirconate titanate (PZT) or a piezoelectric composite material.

15. The equipment according to claim 1, wherein, The receiver-side beamforming process includes a delay and summation beamforming process.

16. An apparatus comprising: Pressure plate; A light source system is configured to provide light to a target object on the outer surface of the pressure plate; An ultrasonic receiver system is configured to receive ultrasonic waves generated by the target object in response to light from the light source system, the ultrasonic receiver system comprising an array of ultrasonic receiver elements; and Control device, used for: An ultrasound receiver signal is received from each of the plurality of ultrasound receiver elements in the array; A receiver-side beamforming process is applied to the ultrasound receiver signal to generate a beamformed ultrasound receiver image; and Blood vessels within the target object are detected, at least in part, based on the beamformed ultrasound receiver image.

17. The equipment according to claim 16, wherein, The control device includes means for detecting the blood vessels within the target object, at least in part based on the ultrasound receiver signal.

18. The equipment according to claim 16, wherein, The control device includes means for estimating one or more vascular features based at least in part on the ultrasound receiver image of the beamforming.

19. The equipment according to claim 18, wherein, The one or more vascular features include vessel diameter, vascular dilation, volumetric flow rate, pulse wave velocity, vessel wall thickness, or a combination thereof.

20. The equipment according to claim 18, wherein, The control device includes means for estimating blood pressure based at least in part on the one or more vascular features.

21. A method comprising: The control system controls the light source system to provide light to the target object on the outer surface of the pressure plate; The control system receives an ultrasonic receiver signal from each of a plurality of ultrasonic receiver elements in an array of ultrasonic receiver elements, the ultrasonic receiver signal corresponding to an ultrasonic wave generated by the target object in response to light from the light source system; The control system applies a receiver-side beamforming process to the ultrasound receiver signal to generate a beamformed ultrasound receiver image. as well as The control system detects blood vessels within the target object based at least in part on the beamformed ultrasound receiver image.

22. The method of claim 21, further comprising detecting the blood vessels within the target object based at least in part on the ultrasound receiver signal.

23. The method of claim 21, further comprising estimating one or more vascular features based at least in part on the beamformed ultrasound receiver image.

24. The method according to claim 23, 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.

25. The method of claim 23, further comprising estimating blood pressure based at least in part on the one or more vascular features.

26. The method according to claim 21, wherein, The receiver-side beamforming process includes a delay and summation beamforming process.

27. One or more non-transitory media storing instructions for performing a method, the method comprising: The control light source system provides light to the target object on the outer surface of the pressure plate; The control system receives an ultrasonic receiver signal from each of a plurality of ultrasonic receiver elements in an array of ultrasonic receiver elements, the ultrasonic receiver signal corresponding to an ultrasonic wave generated by the target object in response to light from the light source system; A receiver-side beamforming process is applied to the ultrasound receiver signal to generate a beamformed ultrasound receiver image; and Blood vessels within the target object are detected, at least in part, based on the beamformed ultrasound receiver image.

28. One or more non-transitory media according to claim 27, wherein, The method also includes detecting the blood vessels within the target object based at least in part on the ultrasound receiver signal.

29. One or more non-transitory media according to claim 27, wherein, The method also includes estimating one or more vascular features based at least in part on the beamformed ultrasound receiver image.

30. One or more non-transitory media according to claim 29, 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.

31. One or more non-transitory media according to claim 29, wherein, The method also includes estimating blood pressure based at least in part on the one or more vascular features.

32. One or more non-transitory media according to claim 27, wherein, The receiver-side beamforming process includes a delay and summation beamforming process.

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