Semi-compact photoacoustic device and system

Abstract

An apparatus may include a platen, a light source system, and an ultrasound receiver system. The platen may be configured to separate one or more received arterial ultrasound waves generated by blood in the artery, by the wall of the artery, or a combination thereof from one or more other types of received ultrasound waves. The platen may have an outer surface having an acoustic impedance configured to approach an acoustic impedance of human skin. An outer surface of the platen may be configured to conform to a surface of human skin. The apparatus may include a noise reduction system. The light source system may include at least one multi-junction laser diode. The apparatus may include a mirror layer residing between the ultrasound receiver system and the platen.

Description

[0001] Priority Claim

[0002] This application claims priority to U.S. Patent Application No. 18 / 069,885, filed on December 21, 2022, entitled "SEMI-COMPACT PHOTOACOUSTIC DEVICES AND SYSTEMS", the entire content of which is incorporated herein by reference and used for all purposes.

[0003] Cross-Reference to Related Applications

[0004] This application is related to U.S. Patent Application No. 18 / 069,859, entitled "PHOTOACOUSTIC DEVICES AND SYSTEMS" (Attorney Docket No. 2205776 / QUALP579US), U.S. Patent Application No. 18 / 069,901, entitled "PHOTOACOUSTIC DEVICES AND SYSTEMS INCLUDING ONE OR MORE LIGHT GUIDE COMPONENTS" (Attorney Docket No. 2300761 / QUALP591US), U.S. Patent Application No. 18 / 069,877, entitled "SEMI-COMPACT PHOTOACOUSTIC DEVICES AND SYSTEMS" (Attorney Docket No. 2205722U1 / QUALP580AUS), U.S. Patent Application No. 18 / 069,882, entitled "SEMI-COMPACT PHOTOACOUSTIC DEVICES AND SYSTEMS" (Attorney Docket No. 2205722U2 / QUALP580BUS), U.S. Patent Application No. 18 / 069,888, entitled "SEMI-COMPACT PHOTOACOUSTIC DEVICES AND SYSTEMS" (Attorney Docket No. 2205722U4 / QUALP580DUS), and U.S. Patent Application No. 18 / 069,893, entitled "SEMI-COMPACT PHOTOACOUSTIC DEVICES AND SYSTEMS" (Attorney Docket No. 2205722U5 / QUALP580EUS), the entire content of all of these patent applications is incorporated herein by reference and used for all purposes. Technical Field

[0005] This disclosure generally relates to photoacoustic devices and systems. Background Art

[0006] A variety of different sensing technologies and algorithms are being implemented in devices for various biometric and biomedical applications, including health and wellness monitoring. This drive is in part due to the limitations of traditional measurement devices for use in continuous, non-invasive, and dynamic monitoring. Some such devices are or include photoacoustic devices. Although some previously deployed photoacoustic devices and systems can provide acceptable results, improved photoacoustic devices and systems would be desirable. SUMMARY OF THE INVENTION

[0007] The systems, methods, and devices of the present disclosure each have several aspects, none of which alone is responsible for the desired attributes disclosed herein.

[0008] An innovative aspect of the subject matter described in the present disclosure can be implemented in a device. The device can include a platen, a light source system, and an ultrasonic receiver system. In some embodiments, a mobile device (such as a wearable device, a cellular phone, etc.) can be or can include at least a portion of the device.

[0009] In some examples, the light source system can be configured to provide light to a target object on an outer surface of the platen. According to some examples, the ultrasonic receiver system can be configured to receive ultrasonic waves generated by the target object in response to light from the light source system. In some examples, a mirror layer can reside between the ultrasonic receiver system and the platen. The mirror layer can be configured to reflect light from the light source system.

[0010] According to some examples, the platen can be configured to increase the intensity of ultrasonic energy received by at least a portion of the ultrasonic receiver system. In some examples, the platen can include a sound waveguide. According to some examples, the platen can include a sound waveguide.

[0011] In some examples, the platen can include an acoustic lens. According to some examples, the acoustic lens can reside on or near the outer surface of the platen. In some examples, the acoustic lens can be a spherical lens or a cylindrical lens.

[0012] According to some examples, the platen, the light source system, or a combination thereof can be configured to transmit light from the light source system to the outer surface of the platen along a first axis or substantially along a first axis. In some examples, the platen can be configured to transmit ultrasonic waves generated by the target object along a second axis or substantially along a second axis. The second axis can be different from the first axis. According to some examples, the platen can be configured to transmit ultrasonic waves generated by the target object along a second axis or substantially along a second axis. The second axis can be parallel to the first axis.

[0013] In some examples, at least one surface of the platen may include an anti-reflection layer. According to some examples, an ultrasonic receiver system may include two or more receiver elements adjacent to an area of the platen, through which area light from a light source is transmitted towards a target object. In some examples, the platen, the light source system, or a combination thereof may be configured to transmit light in the near-infrared range.

[0014] According to some examples, the device may be or may include a mobile device. In some such examples, the outer surface of the platen may correspond to or may be proximate to the outer surface of the mobile device. In some examples, the mobile device may be or may include a cellular phone. According to some examples, the mobile device may be or may include a pen or stylus. In some examples, the pen or stylus may include a force sensor, a motion sensor, a spring, or a combination thereof.

[0015] In some examples, the thickness of the platen, the speed of sound in the platen, or a combination thereof may be configured to separate ultrasonic waves generated by blood in an artery from other ultrasonic waves. According to some examples, the platen may provide an acoustic attenuation of ultrasonic waves in a range from 0.3 to 3.0 decibels per centimeter per megahertz. In some examples, the acoustic impedance of at least the outer surface of the platen is configured to be close to the acoustic impedance of human skin. According to some examples, at least the outer surface of the platen may be configured to conform to the surface of human skin. In some examples, the speed of sound in the platen may be in the range from 800 meters per second to 3000 meters per second.

[0016] According to some examples, the device may include one or more optical waveguides. In some examples, at least a portion of one of the one or more optical waveguides may reside in a portion of the platen.

[0017] According to some examples, a device may include a platen and a light source system configured to provide light to a target object on an outer surface of the platen. The light source system may include one or more laser diodes and a drive circuit. In some examples, the device may include an ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to light from the light source system. In some examples, the device may include a noise reduction system including one or more noise reduction elements configured to at least partially decouple acoustic energy, electrical energy, light, or a combination thereof generated by the light source system from the ultrasonic receiver system.

[0018] In some examples, a noise reduction system can include one or more electromagnetic shielding transmission lines of a light source system. According to some examples, the one or more electromagnetic shielding transmission lines can be configured to reduce electromagnetic interference from the light source system received by an ultrasonic receiver system. According to some examples, the noise reduction system can include one or more air gaps between the light source system and the ultrasonic receiver system. In some examples, the noise reduction system can include one or more sound-absorbing layers configured to reduce sound energy generated by the light source system and received by the ultrasonic receiver system. According to some examples, at least one of the one or more sound-absorbing layers can reside within or proximate to the ultrasonic receiver system. In some examples, at least one of the one or more sound-absorbing layers can reside within or proximate to the light source system. According to some examples, the noise reduction system can include one or more light-absorbing layers configured to reduce the amount of light generated by the light source system and received by the ultrasonic receiver system. In some such examples, at least one of the one or more light-absorbing layers can reside within or proximate to the ultrasonic receiver system.

[0019] According to some examples, the noise reduction system can include one or more reflective layers configured to reduce the amount of light generated by the light source system and received by the ultrasonic receiver system. In some examples, at least one of the one or more reflective layers can reside between the platen and at least a portion of the ultrasonic receiver system.

[0020] In some examples, the light source system can include at least one multi-junction laser diode. According to some examples, the light source system can include a lens configured to collimate light generated by the light source system.

[0021] In some examples, the platen, the light source system, or a combination thereof can be configured to transmit light from the light source system to an outer surface of the platen along a first axis or substantially along a first axis. According to some examples, the platen can be configured to transmit ultrasonic waves generated by a target object along a second axis or substantially along a second axis, where the second axis can be different from the first axis. In some examples, the platen can be configured to transmit ultrasonic waves generated by a target object along a second axis or substantially along a second axis, where the second axis can be parallel to the first axis. According to some examples, the ultrasonic receiver system can include two or more receiver elements adjacent to a region of the platen through which light from the light source system is transmitted toward the target object.

[0022] According to some examples, the light source system can be configured to transmit light in a wavelength range of 500 to 1000 nanometers. In some such examples, the light source system can be configured to transmit light within a wavelength range of 500 to 600 nanometers, a wavelength range of 800 to 950 nanometers, or both. In some examples, the light source system can include one or more light-emitting diodes, one or more vertical-cavity surface-emitting lasers, one or more edge-emitting lasers, or a combination thereof. According to some examples, the drive circuit can be configured to cause the light source system to emit light pulses with a pulse width in the range from 3 nanoseconds to 1000 nanoseconds. In some examples, the drive circuit can be configured to cause the light source system to emit light pulses with a pulse repetition frequency in the range from 1 kilohertz to 100 kilohertz.

[0023] In some examples, the device can be or can include a mobile device. In some examples, the outer surface of the platen can correspond to or can be close to the outer surface of the mobile device. In some examples, the mobile device can be or can include a cellular phone. According to some examples, the mobile device can be or can include a pen or stylus. In some examples, the pen or stylus can include a force sensor, a motion sensor, a spring, or a combination thereof.

[0024] According to some examples, the device can include one or more optical waveguides. According to some examples, at least a portion of one of the one or more optical waveguides can reside in a portion of the platen.

[0025] In some examples, the device can include a platen and a light source system configured to provide light to a target object on the outer surface of the platen. The light source system can include one or more laser diodes and a drive circuit. The one or more laser diodes can include at least one multi-junction laser diode. In some examples, the device can include an ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to light from the light source system.

[0026] According to some examples, the device can further include a noise reduction system including one or more noise reduction elements configured to at least partially decouple acoustic energy generated by the light source system, electrical energy generated by the light source system, light generated by the light source system, or a combination thereof from the ultrasonic receiver system. In some examples, one or more electromagnetic shielding transmission lines can be configured to reduce electromagnetic interference from the light source system received by the ultrasonic receiver system. According to some examples, the noise reduction system can include one or more air gaps between the light source system and the ultrasonic receiver system.

[0027] In some examples, the noise reduction system may include one or more sound-absorbing layers configured to reduce the acoustic energy generated by the light source system and received by the ultrasonic receiver system. According to some examples, at least one of the one or more sound-absorbing layers may reside in or proximate to the ultrasonic receiver system. In some examples, at least one of the one or more sound-absorbing layers may reside in or proximate to the light source system.

[0028] According to some examples, the noise reduction system may include one or more light-absorbing layers configured to reduce the amount of light generated by the light source system and received by the ultrasonic receiver system. In some examples, at least one of the one or more light-absorbing layers may reside in or proximate to the ultrasonic receiver system. According to some examples, the noise reduction system may include one or more reflective layers configured to reduce the amount of light generated by the light source system and received by the ultrasonic receiver system. At least one of the one or more reflective layers may reside between the platen and at least a portion of the ultrasonic receiver system.

[0029] In some examples, the light source system may include a lens configured to collimate the light generated by the light source system. According to some examples, the platen, the light source system, or a combination thereof may be configured to transmit light from the light source system to the outer surface of the platen along a first axis or substantially along a first axis. In some examples, the platen may be configured to transmit ultrasonic waves generated by a target object along a second axis or substantially along a second axis. The second axis may be different from the first axis. According to some examples, the platen may be configured to transmit ultrasonic waves generated by a target object along a second axis or substantially along a second axis. The second axis may be parallel to the first axis.

[0030] In some examples, the ultrasonic receiver system may include two or more receiver elements adjacent to an area of the platen through which light from the light source system is transmitted towards the target object.

[0031] According to some examples, the light source system may be configured to transmit light in a wavelength range of 500 to 1000 nanometers. In some such examples, the light source system may be configured to transmit light in a wavelength range of 500 to 600 nanometers, in a wavelength range of 800 to 950 nanometers, or in both. In some examples, the light source system may include one or more light-emitting diodes, one or more vertical-cavity surface-emitting lasers, one or more edge-emitting lasers, or a combination thereof. According to some examples, the drive circuit may be configured to cause the light source system to emit light pulses having a pulse width in the range from 3 nanoseconds to 1000 nanoseconds. In some examples, the drive circuit may be configured to cause the light source system to emit light pulses at a pulse repetition frequency in the range from 1 kilohertz to 100 kilohertz.

[0032] According to some examples, the mobile device can be or can include a cellular phone. In some examples, the mobile device can be or can include a pen or stylus. According to some examples, the pen or stylus can include a force sensor, a motion sensor, a spring, or a combination thereof.

[0033] In some examples, the device can include one or more optical waveguides. According to some examples, at least a portion of one of the one or more optical waveguides can reside in a portion of the platen.

[0034] In some examples, the device can include a platen, a light source system configured to provide light to a target object on an outer surface of the platen, and an ultrasonic receiver configured to receive ultrasonic waves generated by the target object in response to the light from the light source system. According to some examples, one or more platen characteristics including the thickness of the platen, the speed of sound in the platen, or a combination thereof can be configured to separate one or more arterial ultrasonic waves received from blood in an artery, from an arterial wall, or from a combination thereof, from one or more other types of received ultrasonic waves.

[0035] In some examples, one or more other types of received ultrasonic waves include reflected ultrasonic waves that have been emitted by the ultrasonic receiver and reflected from the target object. According to some examples, one or more platen characteristics cause the reflected ultrasonic waves emitted by the ultrasonic receiver to be received by the ultrasonic receiver after one or more arterial ultrasonic waves.

[0036] In some examples, the speed of sound in the platen can be in the range from 800 meters per second to 3000 meters per second. According to some examples, the thickness of the platen can be in the range from 5 to 40 millimeters. In some examples, the platen can be configured to increase the intensity of ultrasonic energy received by at least a portion of the ultrasonic receiver. According to some examples, the platen can include an acoustic waveguide. In some examples, the platen can include an acoustic lens. The acoustic lens can reside on or near an outer surface of the platen. According to some examples, the acoustic lens can be a spherical lens or a cylindrical lens.

[0037] According to some examples, the platen, the light source system, or a combination thereof can be configured to transmit light from the light source system to an outer surface of the platen along a first axis or substantially along a first axis. In some examples, the platen can be configured to transmit ultrasonic waves generated by the target object along a second axis or substantially along a second axis, where the second axis can be different from the first axis. According to some examples, the platen can be configured to transmit ultrasonic waves generated by the target object along a second axis or substantially along a second axis, where the second axis can be parallel to the first axis.

[0038] In some examples, the ultrasound receiver can include two or more receiver elements adjacent to an area of the platen, through which area light from a light source is transmitted towards a target object. According to some examples, the platen, the light source system, or a combination thereof can be configured to transmit light in the near-infrared range.

[0039] According to some examples, the device can be or can include a mobile device, and wherein an outer surface of the platen can correspond to or can be proximate to an outer surface of the mobile device. According to some examples, the mobile device can be or can include a cellular phone. In some examples, the mobile device can be or can include a pen or stylus. According to some examples, the pen or stylus can include a force sensor, a motion sensor, a spring, or a combination thereof.

[0040] In some examples, the platen can provide an acoustic attenuation of ultrasound in the range of from 0.3 to 6.0 decibels per centimeter per megahertz. In some examples, the ultrasound received by the ultrasound receiver can be in the range of from 0.5 megahertz to 1.5 megahertz, and wherein the platen can provide an acoustic attenuation of ultrasound in the range of from 0.3 to 12.0 decibels per centimeter per megahertz. In some examples, a portion of the platen can reside between the outer surface and the ultrasound receiver, having a thickness in the range of from 0.25 cm to 0.75 cm. According to some examples, the ultrasound received by the ultrasound receiver can be in the range of from 1.5 megahertz to 3.0 megahertz, and wherein the platen can provide an acoustic attenuation of ultrasound in the range of from 0.3 to 3.0 decibels per centimeter per megahertz. In some examples, the portion of the platen residing between the outer surface and the ultrasound receiver can have a thickness in the range of from 0.5 cm to 2.0 cm. According to some examples, the ultrasound received by the ultrasound receiver can be in the range of from 3.0 megahertz to 7.0 megahertz. In some such examples, the platen can provide an acoustic attenuation of ultrasound in the range of from 0.3 to 3.0 decibels per centimeter per megahertz. In some examples, the portion of the platen residing between the outer surface and the ultrasound receiver can have a thickness in the range of from 2.0 cm to 6.0 cm.

[0041] According to some examples, the ultrasound received by the ultrasound receiver can be in the range of from 7.0 megahertz to 13.0 megahertz. In some such examples, the platen can provide an acoustic attenuation of ultrasound of less than 0.15 decibels per centimeter per megahertz. In some examples, the portion of the platen residing between the outer surface and the ultrasound receiver can have a thickness in the range of from 2.0 cm to 6.0 cm.

[0042] According to some examples, the acoustic impedance of at least the outer surface of the platen can be configured to be close to the acoustic impedance of human skin. In some examples, at least the outer surface of the platen can be configured to conform to the surface of human skin.

[0043] In some examples, at least one surface of the platen may include an antireflection layer or have an antireflection layer proximate to the at least one surface.

[0044] According to some examples, the device may include one or more optical waveguides. In some such examples, at least a portion of one of the one or more optical waveguides may reside in a portion of the platen.

[0045] In some examples, a device may include a platen having an outer surface whose acoustic impedance is configured to be close to the acoustic impedance of human skin. According to some examples, the outer surface may be configured to conform to the surface of human skin. In some examples, the device may include a light source system configured to provide light to a target object on or proximate to the outer surface of the platen. In some examples, the device may include an ultrasonic receiver configured to receive ultrasonic waves generated by the target object in response to light from the light source system.

[0046] According to some examples, the acoustic impedance of the outer surface may be in the range of plus or minus 5% of the acoustic impedance of human skin. In some examples, the acoustic impedance of the outer surface may be in the range of plus or minus 10% of the acoustic impedance of human skin. According to some examples, the acoustic impedance of the outer surface may be in the range of 1.4 to 1.7 megaraies.

[0047] In some examples, the outer surface may be configured to conform to the ridges and valleys of a finger pad. According to some examples, the outer surface may be configured to releasably adhere to the surface of human skin.

[0048] According to some examples, the platen may be configured to increase the intensity of ultrasonic energy received by at least a portion of the ultrasonic receiver. In some examples, the platen may include an acoustic waveguide. According to some examples, the platen may include an acoustic lens. In some examples, the acoustic lens may reside on or proximate to the outer surface of the platen. According to some examples, the acoustic lens may be a spherical lens or a cylindrical lens.

[0049] In some examples, the platen, the light source system, or a combination thereof may be configured to transmit light from the light source system to the outer surface of the platen along a first axis or substantially along a first axis. According to some examples, the platen may be configured to transmit ultrasonic waves generated by the target object along a second axis or substantially along a second axis. The second axis may be different from the first axis. According to some examples, the platen may be configured to transmit ultrasonic waves generated by the target object along a second axis or substantially along a second axis. The second axis may be parallel to the first axis.

[0050] In some examples, an ultrasound receiver may include two or more receiver elements adjacent to a region of a platen, through which region of the platen light from a light source is transmitted towards a target object.

[0051] According to some examples, a light source system may be configured to transmit light in a wavelength range from 500 to 1000 nanometers. In some such examples, the light source system may be configured to transmit light in a wavelength range from 500 to 600 nanometers, in a wavelength range from 800 to 950 nanometers, or in both. In some examples, the light source system may include one or more light emitting diodes, one or more vertical cavity surface emitting lasers, one or more edge emitting lasers, or a combination thereof. According to some examples, a drive circuit may be configured to cause the light source system to emit light pulses having a pulse width in a range from 3 nanoseconds to 1000 nanoseconds. In some examples, the drive circuit may be configured to cause the light source system to emit light pulses at a pulse repetition frequency in a range from 1 kilohertz to 100 kilohertz. In some examples, the platen, the light source system, or a combination thereof may be configured to transmit light in the near infrared range.

[0052] In some examples, the device may be or may include a mobile device. In some such examples, an outer surface of the platen may correspond to or may be proximate to an outer surface of the mobile device. According to some examples, the mobile device may be or may include a cellular phone. In some examples, the mobile device may be or may include a pen or stylus. The pen or stylus may include a force sensor, a motion sensor, a spring, or a combination thereof.

[0053] According to some examples, a thickness of the platen, a sound velocity of the platen, or a combination thereof may be configured to separate ultrasonic waves generated by blood in an artery from other ultrasonic waves. In some examples, the platen may provide an acoustic attenuation of ultrasonic waves in a range from 0.3 to 3.0 decibels per centimeter per megahertz. According to some examples, a sound velocity in the platen may be in a range from 800 - 3000 meters per second. In some examples, at least one surface of the platen may include an anti - reflection layer.

[0054] In some examples, the device may include one or more optical waveguides. According to some examples, at least a portion of one of the one or more optical waveguides may reside in a portion of the platen.

[0055] In some embodiments, the device may include a control system. The control system may include one or more general - purpose single - chip or multi - chip processors, digital signal processors (DSPs), application - specific integrated circuits (ASICs), field - programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic, discrete hardware components, or a combination thereof.

[0056] In some examples, the control system may be configured to control a light source system to emit light. According to some examples, the control system may be configured to receive, from an ultrasound receiver system, a signal corresponding to ultrasonic waves generated by a target object. According to some examples, the control system may be configured to identify, from the ultrasound receiver system, one or more arterial wall signals corresponding to ultrasonic waves generated by one or more arterial walls of the target object. According to some examples, the control system may be configured to estimate one or more cardiac characteristics based at least in part on the one or more arterial wall signals.

[0057] According to some examples, the control system may be configured to receive, from an ultrasound receiver system, a signal corresponding to ultrasonic waves generated by a target object. According to some examples, the control system may be configured to identify, from the ultrasound receiver system, one or more arterial blood signals corresponding to ultrasonic waves generated by blood within an artery of the target object. According to some examples, the control system may be configured to estimate one or more cardiac characteristics based at least in part on the one or more arterial blood signals.

[0058] In some examples, the control system may be configured to control a light source system to emit light. In some examples, the control system may be configured to receive, from an ultrasound receiver system, a signal corresponding to ultrasonic waves generated by a target object. In some examples, the control system may be configured to identify, from the ultrasound receiver system, one or more arterial signals corresponding to ultrasonic waves generated by blood within an artery of the target object, ultrasonic waves generated by one or more arterial walls of the target object, or a combination thereof. In some examples, the control system may be configured to, in some examples, the control system may be configured to estimate one or more cardiac characteristics based at least in part on the one or more arterial signals.

[0059] Other innovative aspects of the subject matter described in this disclosure may be implemented in a method. In some examples, the method may involve controlling, by a control system, a light source system to emit light onto a target object on an outer surface of a platen. In some examples, the method may involve receiving, by the control system, from an ultrasound receiver system, a signal corresponding to ultrasonic waves generated by the target object. In some examples, the method may involve identifying, by the control system, an arterial signal from the ultrasound receiver system that corresponds to ultrasonic waves generated by blood within an artery of the target object, ultrasonic waves generated by one or more arterial walls of the target object, or a combination thereof. In some examples, the method may involve, in some examples, the method may involve estimating, by the control system, one or more cardiac characteristics based at least in part on the arterial blood signals. According to some examples, controlling the light source system to emit light may involve controlling the light source system to emit laser pulses.

[0060] Some or all of the methods described herein may be performed by one or more devices according to instructions (e.g., software) stored on a non-transitory medium. Such a non-transitory medium may include memory devices such as those described herein, including but not limited to random access memory (RAM) devices, read only memory (ROM) devices, and the like. Accordingly, some innovative aspects of the subject matter described in this disclosure may be implemented in one or more non-transitory media having software stored thereon. The software may include instructions for controlling one or more devices to perform one or more of the disclosed methods.

[0061] In some examples, the method may involve controlling a light source system by a control system to emit light onto a target object on an outer surface of a platen. In some examples, the method may involve receiving, by the control system, from an ultrasound receiver system, a signal corresponding to ultrasonic waves generated by the target object. In some examples, the method may involve identifying, by the control system, an arterial signal from the ultrasound receiver system, the arterial signal corresponding to ultrasonic waves generated by blood within an artery of the target object, ultrasonic waves generated by one or more arterial walls of the target object, or a combination thereof. In some examples, the method may involve estimating, by the control system, one or more cardiac characteristics based at least in part on the arterial blood signal. According to some examples, controlling the light source system to emit light may involve controlling the light source system to emit laser pulses.

[0062] Details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims. Note that the relative dimensions in the following figures may not be drawn to scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1A An example of a blood pressure monitoring device based on photoplethysmography (PPG) is shown.

[0064] Figure 1B An example of a blood pressure monitoring device based on photoacoustic plethysmography (which may be referred to herein as PAPG) is shown.

[0065] Figure 2A 、 Figure 2B and Figure 2C An example of a device configured to receive acoustic waves emitted from different depths is shown.

[0066] Figure 3 is a block diagram showing example components of a device according to some disclosed implementations.

[0067] Figure 4A An example of components of a device according to some disclosed implementations is shown.

[0068] Figure 4B and Figure 4C illustrates example components of a device in accordance with some additional disclosed embodiments.

[0069] Figure 4D illustrates example components of a device in accordance with additional disclosed embodiments.

[0070] Figure 5 illustrates example components of a device in accordance with some disclosed embodiments.

[0071] Figure 6A is a diagram that illustrates the response of a receiver system to Figure 5 the EMI, light waves, and sound waves represented in

[0072] Figure 6B illustrates example components of a device in accordance with some disclosed embodiments.

[0073] Figure 6C is a diagram that illustrates, for a range of platen thicknesses, an example of Figure 6B the time of flight of sound waves corresponding to each artery size and depth shown in

[0074] Figure 7 illustrates an example of a photoacoustic device configured as a smart phone.

[0075] Figure 8 illustrates an example of a photoacoustic device configured for a pen-type embodiment.

[0076] Figure 9A 、 Figure 9B and Figure 9C illustrate examples of ray tracing inside a target object and two different types of platens.

[0077] Figure 10A 、 Figure 10B 、 Figure 10C and Figure 10D illustrate examples of two additional types of platens and corresponding ray tracing diagrams.

[0078] Figure 11A and Figure 11B illustrates example components of a device in accordance with some additional disclosed embodiments.

[0079] Figure 12 、 Figure 13 and Figure 14 illustrate components of a device including a noise reduction element.

[0080] Figure 15A and Figure 15B illustrate examples of devices having different types of light source systems.

[0081] Figure 16A A graph showing the blood light absorption coefficients of hemoglobin (Hb) and oxyhemoglobin (HbO2) versus wavelength is presented.

[0082] Figure 16B A table indicating the maximum permissible exposure (MPE) guidelines for wavelengths of 808 nanometers and 940 nanometers is presented.

[0083] Figure 17A A graph showing an example of a photoacoustic (PA) signal received by a receiver system is presented.

[0084] Figure 17B An example of a single-junction laser diode implementation is presented.

[0085] Figure 17C An example of a multi-junction laser diode implementation is presented, in which the multi-junction laser diode includes 5 junctions.

[0086] Figure 18 A flowchart showing examples of some disclosed operations is presented.

[0087] Figure 19 An example of heart rate waveform (HRW) features that can be extracted according to some embodiments is presented.

[0088] Figure 20 An example of a device that can be used in a system for estimating blood pressure based at least in part on pulse transit time (PTT) is presented.

[0089] Figure 21 A cross-sectional side view of a graphical representation of a portion of an artery through which a pulse propagates is presented.

[0090] Like reference numerals and markings in the various figures indicate like elements. Detailed Description

[0091] For purposes of describing aspects of the present disclosure, the following description is directed to certain embodiments. However, those of ordinary skill in the art will readily recognize that the teachings herein can be applied in many different ways. Some of the concepts and examples provided in the present disclosure are particularly applicable to blood pressure monitoring applications. However, some embodiments can also be applicable to other types of biosensing applications as well as other fluid flow systems. The described embodiments can be implemented in any device, apparatus, or system that includes the devices disclosed herein. Additionally, it is contemplated that the described embodiments can be included in or associated with various electronic devices, such as, but not limited to: mobile phones, multimedia Internet-enabled cellular phones, mobile TV receivers, wireless devices, smart phones, smart cards, wearable devices (such as bracelets, armbands, wristbands, rings, headbands, patches, etc.), Bluetooth® devices, personal data assistants (PDAs), wireless email receivers, handheld or portable computers, netbooks, notebooks, smartbooks, tablet computers, printers, copiers, scanners, fax devices, global positioning system (GPS) receivers / navigators, cameras, digital media players, gaming consoles, watches, clocks, calculators, television monitors, flat panel displays, electronic reading devices (e.g., e-readers), mobile health devices, computer monitors, automotive displays (including odometer and speedometer displays, etc.), cockpit controls and / or displays, camera view displays (such as the display of a rear view camera in a vehicle), building structures, microwave ovens, refrigerators, stereo systems, cassette recorders or players, DVD players, CD players, VCRs, radios, portable memory chips, washing machines, dryers, washer / dryers, parking meters, vehicle doors, autonomous or semi-autonomous vehicles, drones, Internet of Things (IoT) devices, etc. Accordingly, the teachings are not intended to be limited to the specific embodiments depicted and described with reference to the figures; rather, these teachings have broad applicability, which will be apparent to those of ordinary skill in the art.

[0092] In recent years, a variety of different devices have emerged on the market for biometric and biomedical applications, including health and wellness monitoring, biometric authentication, etc. Some such devices include light sources, such as light sources that include one or more lasers. For example, some health monitoring systems and some biometric authentication systems can be configured to illuminate a target with high-intensity light for in vivo detection, such as for heart pulse detection. Some devices can be configured to illuminate a target with high-intensity light for blood oxygen estimation, heart rate monitoring, blood pressure monitoring, etc. Some such devices can illuminate a target with high-intensity light for blood pressure monitoring based on photoplethysmography (PPG) or photoacoustic plethysmography (PAPG).

[0093] Compared with more invasive health monitoring devices (such as cuff - based or catheter - based blood pressure measurement devices), non - invasive health monitoring devices (such as PAPG - based devices) have various potential advantages. However, it has been shown that it is difficult to design a satisfactory compact or semi - compact PAPG - based device. (Some "semi - compact" devices may have a length in the range of 5.0 millimeters to 40 millimeters. Some semi - compact devices may have a cross - sectional area in the range of 6.0 square millimeters to 50 square millimeters. A "compact" device is a device smaller than a semi - compact device.) For example, some previously deployed PAPG - based devices have generated various types of artifact signals, including but not limited to electromagnetic interference (EMI) signals, signals from reflected light, and signals from reflected sound waves. Such artifact signals may obscure the desired signals, such as signals corresponding to blood vessels or blood within blood vessels.

[0094] Some disclosed devices include a platen, a light source system, and an ultrasonic receiver system. In some embodiments, the platen can be configured to separate one or more received arterial ultrasonic waves generated by blood in an artery, by an arterial wall, or by a combination thereof from one or more other types of received ultrasonic waves. According to some embodiments, the platen can have an outer surface whose acoustic impedance is configured to be close to the acoustic impedance of human skin. In some such embodiments, the outer surface of the platen can be configured to conform to the surface of human skin.

[0095] Some disclosed embodiments can include a noise reduction system. According to some embodiments, the light source system can include at least one multi - junction laser diode. Some disclosed embodiments can include a mirror layer residing between the ultrasonic receiver system and the platen.

[0096] Certain embodiments of the subject matter described in this disclosure can be implemented to achieve one or more of the following potential advantages. In some embodiments, the noise reduction system can be configured to at least partially decouple acoustic energy, electrical energy, light, or a combination thereof generated by the light source system from the ultrasonic receiver system. Such embodiments can increase the signal - to - noise ratio of the desired signal. Embodiments in which the light source system includes at least one multi - junction laser diode can also reduce noise and increase the signal - to - noise ratio of the desired signal. According to some embodiments, the arterial ultrasonic waves can be more easily detected because the platen can be configured to separate the received arterial ultrasonic waves from one or more other types of received ultrasonic waves. In some embodiments that include a mirror layer, the mirror layer can be configured to reflect light from the light source system away from the ultrasonic receiver system, thereby reducing another type of noise.

[0097] Figure 1AShows an example of a blood pressure monitoring device based on photoplethysmography (PPG). Figure 1A Shows examples of arteries, veins, arterioles, venules, and capillaries of the circulatory system (including arteries, veins, arterioles, venules, and capillaries inside finger 115). In Figure 1A The example shown, an electrocardiogram (ECG) sensor has detected a proximal arterial pulse near the heart 116. Some examples of measuring the arterial pulse transit time (PTT) based on the arterial pulses measured by two sensors are described below. In some embodiments, one of the sensors can be an ECG sensor.

[0098] According to Figure 1A The example shown, a light source including one or more lasers or light-emitting diodes (LEDs) has transmitted light (in some examples, green light, red light, and / or near-infrared (NIR) light), which has penetrated the tissue of finger 115 in the illumination area. The reflections from these tissues detected by a photodetector can be used to detect volume changes corresponding to the heart rate waveform in the blood of the illuminated area of finger 115.

[0099] As Figure 1A Shown in the heart rate waveform diagram 118, the capillary heart rate waveform 119 has a different shape and phase shift relative to the arterial heart rate waveform 117. In this simple example, the detected heart rate waveform 121 is a combination of the capillary heart rate waveform 119 and the arterial heart rate waveform 117. In some cases, the responses of one or more other blood vessels can also be part of the heart rate waveform 121 detected by the PPG-based blood pressure monitoring device. The PPG-based blood pressure monitoring device is not optimal because the PPG superimposes data corresponding to the blood volumes of all illuminated blood vessels, and each blood vessel exhibits different and time-offset blood volume changes. Nevertheless, there are many deployed PPG-based blood pressure monitoring devices.

[0100] Figure 1B Shows an example of a blood pressure monitoring device based on photoacoustic plethysmography (which may be referred to as PAPG herein). Figure 1B Shows Figure 1A The same examples of arteries, veins, arterioles, venules, and capillaries inside finger 115 shown in Figure 1B In some examples, the light source shown in Figure 1A Can be or can include one or more LEDs, one or more laser diodes, etc. In this example, as

[0101] In Figure 1BIn the example shown, the blood vessel (and the components of the blood itself) is heated by incident light from a light source and emits sound waves. In this example, the emitted sound waves include ultrasonic waves. According to this embodiment, the sound wave emission is being detected by an ultrasonic receiver, which in this example is a piezoelectric receiver. The photoacoustic emission from the irradiated tissue detected by the piezoelectric receiver can be used to detect the volume change corresponding to the heart rate waveform in the blood in the irradiated area of the finger 115. Although some of the tissue areas shown as being irradiated are offset from the tissue areas shown as generating photoacoustic emissions, this is merely for illustrative convenience. It will be understood that the actually irradiated tissue will be those that generate photoacoustic emissions. Additionally, it will be understood that the maximum level of photoacoustic emission will generally be generated along the same axis as the maximum irradiation level. In some examples, the ultrasonic receiver can be an instance of the receiver system 202 described below with reference to FIG. 2.

[0102] Figure 1A An important difference between the PPG-based system and Figure 1B the PAPG-based method is that Figure 1B the sound waves shown in Figure 1A travel much slower than the reflected light waves shown in Figure 1B . Therefore, depth discrimination based on the arrival time of the sound waves shown in Figure 1A is possible, while depth discrimination based on the arrival time of the light waves shown in

[0103] This depth discrimination allows some of the disclosed embodiments to isolate the sound waves received from different blood vessels.

[0104] Figure 2A , 2B and 2C show examples of devices configured to receive sound waves emitted from different depths. As with other embodiments shown and described herein, Figure 2A - 2C the types of elements shown in

[0105] According to these examples, the device 200 includes an ultrasonic receiver 202, a light source system 204 (which includes an LED in this example), and a control system (which is not shown in Figure 2A - 2C ). According to these examples, the device 200 includes a beam splitter 201 inside the platen 202 to which the light source system 204 is mounted. In this case, the finger 206 rests on the outer surface 205 of the device 200.

[0106] Figure 2A shows the light 203 emitted from the light source system 204. A portion of the light 203 is reflected by the beam splitter 201 and enters the finger 206. For example, the range gate delay (RGD) for this and other embodiments can be selected to correspond to the time required for the photoacoustic emission to reach the receiver from the shallowest target of interest. For example, in one configuration of the device 200 using a 12.7 mm beam splitter between the finger 206 and the ultrasonic receiver 202 ( Figure 2A RX in), the finger surface signal will arrive in the time it takes for the sound wave to travel through the entire beam splitter. Using the speed of sound in borosilicate glass of 5500 m / s as an approximation of the speed of sound in the beam splitter and a beam splitter size of 12.7 mm, this time becomes 12.7 mm / 5500 m / s, or 2.3 microseconds. Thus, a range gate delay of 2.3 microseconds corresponds to the surface of the finger 206. For example, to travel 1 mm in the finger 206, now using the speed of sound in tissue of 1.5 mm / microsecond, this time becomes 1 mm / 1.5 mm / microsecond, or ~0.67 microseconds. Thus, a range gate delay of ~2.97 microseconds (2.3 microseconds + 0.67 microseconds) will cause the ultrasonic receiver 202 to start sampling the sound wave reflected from a depth of approximately 1 mm below the outer surface of the finger 206.

[0107] Figure 2B shows the acoustic signal corresponding to the photoacoustic emission from the tissue (e.g., blood and blood vessels) inside the finger 206 caused by the light entering the finger 206. In Figure 2B the example shown, the acoustic signals originate from different depths (depths 208a, 208b, and 208c) within the finger 206. Therefore, the travel times t1, t2, and t3 from depths 208a, 208b, and 208c to the ultrasonic receiver 202 are also different: in this case, t3 > t2 > t1. Thus, multiple acquisition time delays can be selected to receive the sound waves emitted from depths 208a, 208b, and 208c.

[0108] Figure 2C shows what can be done by, for example, Figure 2A and Figure 2BThe various types of signals and noises generated by the devices shown in [figure]. In this example, the only desired signals generated by the receiver system 202 are those signals caused by PA4, which are photoacoustic waves of the artery generated in response to the incident light 203a by the artery 207, by the blood in the artery 207, or a combination thereof. However, the receiver system 202 may also generate unwanted signals in response to various other phenomena, including signals in response to electromagnetic interference (EMI) 211 generated by the drive circuitry of the light source system 204, signals in response to reflected light 203b reflected from the outer surface of the device 200 or from the finger 206, signals in response to photoacoustic waves PA1, PA2, PA3, PA5, and PA6, and sound waves A1 and A2. In these examples, the photoacoustic wave PA1 is generated by the receiver system 202 in response to light reflected from the finger 206, the photoacoustic wave PA2 is generated by the beam splitter 201, the photoacoustic wave PA3 is generated by the surface of the finger 206, the photoacoustic wave PA5 is an arterial photoacoustic signal having a trajectory different from that of the photoacoustic wave PA4, and the photoacoustic wave PA6 is generated by the structure of the light source system 204. According to these examples, the sound wave A1 is generated by the reverberation of EMI, PA1, PA2, PA3, PA4, PA5, and PA6 within the platen 202. Here, the sound wave A2 is generated by the mechanical vibration of the light source system 204, such as the mechanical vibration of the drive circuitry of the light source system 204 or the mechanical vibration generated by the drive circuitry of the light source system 204.

[0109] In view of the foregoing problems, the present inventors have designed various disclosed embodiments. In some embodiments, the device may include a platen configured to separate one or more received arterial ultrasonic waves (such as Figure 2C the arterial photoacoustic wave PA4) from one or more other types of received sound waves and photoacoustic waves (such as Figure 2C the photoacoustic waves PA1, PA2, PA3, PA5, and PA6, Figure 2C the sound waves A1 and A2, or one or more of their combinations). Some disclosed embodiments may include a noise reduction system configured to at least partially decouple the acoustic energy (such as Figure 2C the sound wave A2) generated by the light source system 204, the EMI (such as Figure 2C the EMI 211) generated by the light source system 204, the light generated by the light source system 204, or a combination thereof from the ultrasonic receiver system 202. Some disclosed embodiments may include a mirror system configured to reflect light away from the ultrasonic receiver system 202. In some disclosed embodiments, the light source system may include at least one multi-junction laser diode, which may generate less noise than a single-junction laser diode.

[0110] Figure 3It is a block diagram showing example components of a device according to some disclosed embodiments. In this example, device 300 includes a platen 301, a receiver system 302, and a light source system 304. Some embodiments of device 300 may include a noise reduction system 305, a control system 306, an interface system 308, a mirror system 310, or a combination thereof.

[0111] Various examples of platen 301 are disclosed herein. Some examples are shown in Figures 4A to 5 , Figure 7 , Figure 8 and Figures 10A to 11B and are described in more detail below with reference to these figures.

[0112] In some embodiments where receiver system 302 includes an ultrasonic receiver system, platen 301 may be configured to increase the intensity of ultrasonic energy received by at least a portion of the ultrasonic receiver system. In some such embodiments, platen 301 may include a sound waveguide. According to some embodiments, platen 301 may include an acoustic lens system. The acoustic lens system may reside, for example, on or near the outer surface of platen 301. The acoustic lens system may include, for example, a spherical lens or a cylindrical lens.

[0113] According to some examples, platen 301, light source system 304, or a combination thereof may be configured to transmit light from the light source system to the outer surface of the platen (or to a target object on or near the outer surface) along a first axis or substantially along a first axis. In this context, "substantially along the first axis" may mean within an angular range of plus or minus 10 degrees, plus or minus 15 degrees, plus or minus 20 degrees, plus or minus 25 degrees, plus or minus 30 degrees, or within another such angular range of the first axis.

[0114] In some examples, platen 301 may be configured to transmit ultrasonic waves generated by a target object along a second axis or substantially along a second axis. In this context, "substantially along the second axis" may mean within an angular range of plus or minus 10 degrees, plus or minus 15 degrees, plus or minus 20 degrees, plus or minus 25 degrees, plus or minus 30 degrees, or within another such angular range of the second axis. According to some examples, the second axis may be parallel to the first axis. However, in some examples, the second axis may be different from the first axis.

[0115] According to some examples, the platen 301 may include one or more anti-reflection layers configured to suppress optical reflection. As used herein, the term "anti-reflection" refers to light reflection. In other words, an "anti-reflection" layer is a layer configured to reduce light reflection. In some such examples, the platen 301 may include one or more anti-reflection layers residing between the platen 301 and the receiver 302. In some examples, the thickness of the platen 301, the speed of sound of the platen 301, or a combination thereof may be configured to separate ultrasonic waves generated by blood in an artery from other ultrasonic waves.

[0116] In some examples, the acoustic impedance of at least a portion of the outer surface of the platen 301 may be configured to approximate the acoustic impedance of human skin. The portion of the outer surface of the platen 301 may be, for example, the portion configured to receive a target object such as a human finger. (As used herein, the terms "finger" and "digit" may be used interchangeably such that the thumb is an example of a finger.) The typical range of the acoustic impedance of human skin is from 1.53 to 1.680 megaryls. In some examples, at least the outer surface of the platen 301 may have an acoustic impedance in the range of from 1.4 to 1.8 megaryls or in the range of from 1.5 to 1.7 megaryls.

[0117] Alternatively or additionally, in some examples, at least the outer surface of the platen 301 may be configured to conform to the surface of human skin. In some such examples, at least the outer surface of the platen 301 may have material properties similar to putty or chewing gum.

[0118] This disclosure presents various examples of the receiver system 302, some of which may include an ultrasonic receiver system, an optical receiver system, or a combination thereof. In some embodiments that include an ultrasonic receiver system, the ultrasonic receiver and the ultrasonic transmitter may be combined in an ultrasonic transceiver. In some examples, the receiver system 302 may include a piezoelectric receiver layer, such as a PVDF polymer layer or a PVDF-TrFE copolymer layer. In some examples, the receiver system 302 may include a composite piezoelectric material, such as a 0-3 composite, a 1-3 composite, a 2-2 composite, a 3-3 composite, etc. In some embodiments, a single piezoelectric layer may be used as an ultrasonic receiver. In some embodiments, other piezoelectric materials may be used in the piezoelectric layer, such as aluminum nitride (AlN) or lead zirconate titanate (PZT). In some examples, the receiver system 302 may include an array of ultrasonic transducer elements, such as an array of piezoelectric micromachined ultrasonic transducers (PMUTs), an array of capacitive micromachined ultrasonic transducers (CMUTs), etc. In some such examples, the piezoelectric receiver layer, a PMUT element in a single-layer array of PMUTs, or a CMUT element in a single-layer array of CMUTs may be used as both an ultrasonic transmitter and an ultrasonic receiver. According to some examples, the receiver system 302 may be or may include an ultrasonic receiver array. In some examples, the device 300 may include one or more separate ultrasonic transmitter elements. In some such examples, the (multiple) ultrasonic transmitters may include an ultrasonic plane wave generator.

[0119] In some examples, the light source system 304 may include one or more light-emitting diodes (LEDs). In some embodiments, the light source system 304 may include one or more laser diodes. According to some embodiments, the light source system 304 may include one or more vertical-cavity surface-emitting lasers (VCSELs). In some embodiments, the light source system 304 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.

[0120] In some examples, the light source system 304 may be configured to transmit light within one or more wavelength ranges. In some examples, the light source system 304 may be configured to transmit light in the wavelength range of 500 to 600 nanometers (nm). In some examples, the light source system 304 may be configured to transmit light in the wavelength range of 700 to 800 nanometers. According to some examples, the light source system 304 may be configured to transmit light in the wavelength range of 800 to 950 nanometers.

[0121] Depending on the particular implementation, the light source system 304 may include various types of drive circuitry. In some of the disclosed implementations, the light source system 304 may include at least one multi-junction laser diode, which may generate less noise than a single-junction laser diode. In some examples, the light source system 304 may include a drive circuit (also referred to herein as drive circuitry) configured to cause the light source system to emit light pulses having a pulse width in the range from 3 nanoseconds to 1000 nanoseconds. According to some examples, the light source system 304 may include a drive circuit configured to cause the light source system to emit light pulses at a pulse repetition frequency in the range from 1 kilohertz to 100 kilohertz.

[0122] In some implementations, the platen 301, the receiver system 302, the light source system 304, or a combination thereof may include one or more sound-absorbing layers. In some examples, the light source system 304 may include one or more electromagnetic shielding transmission lines. In some such examples, the one or more electromagnetic shielding transmission lines may be configured to reduce electromagnetic interference received by the receiver system 302 from the light source system 304. Such a sound-absorbing layer, electromagnetic shielding transmission line, or a combination thereof may also be considered part of the noise reduction system 305.

[0123] In some embodiments, the light source system 304 can be configured to emit light of various wavelengths, which can be selectable to trigger acoustic wave emission primarily from a specific type of material. For example, since hemoglobin in blood absorbs near-infrared light quite strongly, in some embodiments, the light source system 304 can be configured to emit one or more wavelengths of light in the near-infrared range to trigger acoustic wave emission from hemoglobin. Given factors such as skin reflectivity, fluence, absorption coefficients of blood and various tissues, and skin safety limits, certain wavelength ranges may be relatively more or less suitable for various use cases. For example, wavelength ranges of 500 nanometers to 600 nanometers and 800 to 950 nanometers can both be suitable for obtaining a photoacoustic response from relatively small, shallow blood vessels (such as those that can be found in a finger, such as having a diameter of approximately 0.5 millimeters and a depth in the range of 0.5 millimeters to 1.5 millimeters). For example, the wavelength range of 800 to 950 nanometers can be suitable for obtaining a photoacoustic response from relatively large, deep blood vessels (such as those that can be found in an adult wrist, such as having a diameter of approximately 2.0 millimeters and a depth in the range of 2 millimeters to 3 millimeters). However, in some examples, the control system 306 can control the (multiple) wavelengths of the light emitted by the light source system 304 to preferentially induce acoustic waves in blood vessels, other soft tissues, and / or bones. For example, an infrared (IR) light-emitting diode LED can be selected and emit short pulses of IR light to irradiate a portion of a target object and generate acoustic wave emission, which is then detected by the receiver system 302. In another example, an IR LED and a red LED or other colors, such as green, blue, white, or ultraviolet (UV), can be selected in sequence, and short pulses of light can be emitted from each light source, and an ultrasound image can be obtained after light has been emitted from each light source. In other embodiments, one or more light sources of different wavelengths can be fired sequentially or simultaneously to generate acoustic emissions detectable by an ultrasound receiver. Image data from the ultrasound receiver can be combined to determine the location and type of materials in the target object, where the image data is obtained using light sources of different wavelengths and at different depths into the target object (e.g., varying RGD). Since materials in the body typically absorb light of different wavelengths differently, image contrast can occur. Since materials in the body absorb light of a specific wavelength, they may heat up differently and generate acoustic wave emissions with sufficiently short light pulses having sufficient intensity. Depth contrast can be obtained using light of different wavelengths and / or the intensity at each selected wavelength. That is, continuous images can be obtained at a fixed RGD (which can correspond to a fixed depth into the target object) using varying light intensities and wavelengths to detect materials and their locations within the target object. For example, hemoglobin, blood glucose, or blood oxygen within blood vessels inside a target object such as a finger can be detected photoacoustically.

[0124] According to some embodiments, the light source system 304 may be configured to emit light pulses having a pulse width of less than about 100 nanoseconds. In some embodiments, the light pulses may have a pulse width between about 10 nanoseconds and about 500 nanoseconds or longer. According to some examples, the light source system may be configured to emit a plurality of light pulses at a pulse repetition frequency between 10 Hertz and 100 kiloHertz. Alternatively or additionally, in some embodiments, the light source system 304 may be configured to emit a plurality of light pulses at a pulse repetition frequency between about 1 megaHertz and about 100 megaHertz. Alternatively or additionally, in some embodiments, the light source system 304 may be configured to emit a plurality of light pulses at a pulse repetition frequency between about 10 Hertz and about 1 megaHertz. In some examples, the pulse repetition frequency of the light pulses may correspond to the acoustic resonance frequency of the ultrasonic receiver and the substrate. For example, a set of four or more light pulses may be emitted from the light source system 304 at a frequency corresponding to the resonance frequency of the resonant acoustic cavity in the sensor stack, thereby allowing the accumulation of the received ultrasonic waves and a higher generated signal intensity. In some embodiments, a filtered light or light source having a specific wavelength for detecting a selected material may be included in the light source system 304. In some embodiments, the light source system may include light sources such as red, green, and blue LEDs of a display, which may be enhanced with light sources of other wavelengths (such as IR and / or UV) and with light sources of higher optical power. For example, a high-power laser diode or an electronic flash unit (e.g., an LED or a xenon flash unit) with or without a filter may be used for short-term illumination of the target object.

[0125] In some examples, the device 300 includes a noise reduction system 305. One or more specific components of the noise reduction system 305 may vary according to a particular embodiment. Some examples of the noise reduction system 305 are described in more detail below with reference to Figures 12 to 14 more detail.

[0126] According to some examples, the noise reduction system 305 may include one or more noise reduction elements configured to at least partially decouple acoustic energy generated by the light source system 304, electrical energy generated by the light source system 304, light generated by the light source system 304, or a combination thereof from the receiver system 302.

[0127] In some examples, the noise reduction system 305 may include one or more electromagnetic shielding transmission lines, which may be the electromagnetic shielding transmission lines of the light source system 304 in some examples. In some such examples, the one or more electromagnetic shielding transmission lines may be configured to reduce electromagnetic interference received by the receiver system 302 from the light source system 304.

[0128] According to some examples, the noise reduction system 305 can include one or more air gaps between the light source system 304 and the receiver system 302. Alternatively or additionally, in some examples, the noise reduction system 305 can include one or more sound-absorbing layers configured to reduce the sound energy generated by the light source system 304 and received by the receiver system 302. In some examples, at least one of the one or more sound-absorbing layers can reside in or proximate to the receiver system 302. In some examples, at least one of the one or more sound-absorbing layers can reside in or proximate to the light source system 304.

[0129] In some examples, the noise reduction system 305 can include one or more light-absorbing layers configured to reduce the amount of light generated by the light source system 304 and received by the receiver system 302. Preferably, the one or more light-absorbing layers have a relatively low Grüneisen parameter and do not generate a large photoacoustic signal. According to some examples, at least one light-absorbing layer can reside in or proximate to the receiver system 302.

[0130] According to some examples, the noise reduction system 305 can include one or more reflective layers configured to reduce the amount of light generated by the light source system 304 and received by the receiver system 302. Such a reflective layer can also be considered part of the mirror system 310. In some examples, at least one reflective layer can reside between the platen 301 and at least a portion of the receiver system 302.

[0131] The control system 306 can include one or more general-purpose single-chip or multi-chip processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic, discrete hardware components, or combinations thereof. The control system 306 can also include one or more memory devices, such as one or more random access memory (RAM) devices, read-only memory (ROM) devices, etc., (and / or configured to communicate therewith). Thus, the apparatus 300 can have a memory system including one or more memory devices, although Figure 3 the memory system is not shown therein. The control system 306 can be configured to receive and process data from the receiver system 302, for example, as described below. If the apparatus 300 includes an ultrasonic transmitter, the control system 306 can be configured to control the ultrasonic transmitter. In some embodiments, the functions of the control system 306 can be divided among one or more controllers or processors, such as a dedicated sensor controller and an application processor of a mobile device.

[0132] In some examples, the control system 306 can be configured to control the light source system 304 to emit light towards a target object on the outer surface of the platen 301. In some such examples, the control system 306 can be configured to receive, from the ultrasonic receiver system 302, a signal corresponding to ultrasonic waves generated by the target object in response to the light from the light source system 304. In some examples, the control system 306 can be configured to identify one or more arterial signals from the ultrasonic receiver system. In some such examples, the one or more arterial signals can be or can include one or more arterial wall signals corresponding to ultrasonic waves generated by one or more arterial walls of the target object. In some such examples, the one or more arterial signals can be or can include one or more arterial blood signals corresponding to ultrasonic waves generated by blood within the arteries of the target object. In some examples, the control system 306 can be configured to estimate one or more cardiac characteristics at least in part based on the one or more arterial signals. According to some examples, the cardiac characteristics can be or can include blood pressure.

[0133] Some embodiments of the apparatus 300 can include an interface system 308. In some examples, the interface system 308 can include a wireless interface system. In some embodiments, the interface system 308 can include a user interface system, one or more network interfaces, one or more interfaces between the control system 306 and the memory system, and / or one or more interfaces between the control system 306 and one or more external device interfaces (e.g., ports or application processors), or a combination thereof. According to some examples in which the interface system 308 is present and includes a user interface system, the user interface system can include a microphone system, a speaker system, a haptic feedback system, a voice command system, one or more displays, or a combination thereof. According to some examples, the interface system 308 can include a touch sensor system, a gesture sensor system, or a combination thereof. The touch sensor system (if present) can be or can include a resistive touch sensor system, a surface capacitive touch sensor system, a projected capacitive touch sensor system, a surface acoustic wave touch sensor system, an infrared touch sensor system, any other suitable type of touch sensor system, or a combination thereof.

[0134] In some examples, the interface system 308 can include a force sensor system. The force sensor system, if present, can be or can include a piezoresistive sensor, a capacitive sensor, a thin film sensor (e.g., a polymer-based thin film sensor), another type of suitable force sensor, or a combination thereof. If the force sensor system includes a piezoresistive sensor, the piezoresistive sensor can include silicon, metal, polysilicon, glass, or a combination thereof. In some embodiments, the ultrasonic fingerprint sensor and the force sensor system can be mechanically coupled. In some such examples, the force sensor system can be integrated into the circuitry of the ultrasonic fingerprint sensor. In some examples, the interface system 308 can include an optical sensor system, one or more cameras, or a combination thereof.

[0135] According to some examples, the device 300 can include a mirror system 310 that includes one or more mirrors. For example, the mirror system 310 can include one or more mirrors configured to reflect light from the light source system 304 away from the receiver system 302.

[0136] The device 300 can be used in a variety of different contexts, many examples of which are disclosed herein. For example, in some embodiments, a mobile device can include the device 300. In some such examples, the mobile device can be a smart phone. According to some examples, the mobile device can be a pen-type device. Reference is made below Figure 7 and Figure 8 to describe some related examples. In some embodiments, a wearable device can include the device 300. The wearable device can be, for example, a bracelet, an armband, a wristband, a watch, a ring, a headband, or a patch.

[0137] Figure 4A An example component of a device according to some disclosed embodiments is shown. As with other figures provided herein, Figure 4A the number, type, and arrangement of the elements shown are presented by way of example only. In this example, the device 300 is Figure 3 an instance of the device 300 shown in

[0138] In this example, the outer surface 205 of the platen 301 is configured to receive a target object, such as a finger 206. Although in Figure 4AThe middle finger 206 is shown positioned above the outer surface 205, but this is merely for a clearer illustration of the outer surface 205. In this example, the outer surface 205 of the platen 301 is configured as an acoustic lens: the cylindrical shape of the outer surface 205 is configured to focus the photoacoustic waves, including ultrasonic waves, generated by the light 203a from the light source system 304 within the finger 206. Thus, the outer surface 205 of the platen 301 is configured as a cylindrical acoustic lens, which can increase the intensity of the ultrasonic energy received by at least a portion of the receiver system 302. The following describes this effect in more detail with reference to Figures 10A to 10D in more detail.

[0139] In some alternative examples, the platen 301 may include another type of acoustic lens. For example, at least a portion of the outer surface 205 of the platen 301 may be configured as a spherical acoustic lens. In some such examples, the concave portion in at least a portion of the outer surface 205 may have a shape corresponding to a portion of a sphere.

[0140] According to this example, the light source system 304 includes a light-emitting portion 304a and a lens 304b. The light-emitting portion 304a may include, for example, one or more light-emitting diodes, one or more laser diodes, one or more VCSELs, one or more edge-emitting lasers, one or more neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers, or a combination thereof. In this example, the lens 304b is configured to focus the light 203a emitted by the light-emitting portion 304a into a relatively small cross-sectional area, which increases the intensity of the light 203a received by the target object (such as the finger 206) on the outer surface 205.

[0141] In this example, the platen 301 includes a platen portion 301a and a platen portion 301b. According to this example, the platen portion 301a is configured to direct the light 203a from the light source system 304 toward the outer surface 205. In this example, the platen portion 301b is configured to direct the acoustic waves, including photoacoustic waves, emitted by the target object on the outer surface 205 toward the receiver system 302.

[0142] According to this example, the platen 301 (more specifically, the platen portion 301a) and the light source system 304 are configured to transmit the light 203a from the light source system 304 to the outer surface 205 of the platen 301 along a first axis or substantially along a first axis. In Figure 4A the example, the axis 405a is an example of the first axis. In this context, "substantially along the first axis" may mean within an angular range of plus or minus 10 degrees, plus or minus 15 degrees, plus or minus 20 degrees, plus or minus 25 degrees, plus or minus 30 degrees, or another such angular range with respect to the first axis.

[0143] In this example, the platen 301 (more specifically, the platen portion 301b) is configured to transmit acoustic waves, including but not limited to ultrasonic waves, generated by a target object on the outer surface 205 along a second axis or substantially along the second axis toward the receiver system 302. In Figure 4A it, the axis 405b is an example of the second axis. In this context, "substantially along the second axis" can mean within an angular range of plus or minus 10 degrees of the second axis, within an angular range of plus or minus 15 degrees of the second axis, within an angular range of plus or minus 20 degrees of the second axis, within an angular range of plus or minus 25 degrees of the second axis, within an angular range of plus or minus 30 degrees of the second axis, or within another such angular range. According to this example, the platen portion 301b is shown to transmit arterial photoacoustic wave PA4 substantially along the axis 405b.

[0144] In this example, the second axis is not parallel to the first axis, but is separated from the first axis by an angle Θ. Such an example has the potential advantage of allowing the (one or more) platen portions configured for light transmission to be designed and optimized independently of the (one or more) platen portions configured for ultrasonic transmission. According to some alternative examples, the second 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 second axis (such as within + / - 5 degrees, within + / - 10 degrees, within + / - 15 degrees, within + / - 20 degrees, etc.). The first axis and the second axis can be defined, for example, by a coordinate system with respect to the device 300 or a part thereof. In Figure 4A the example shown, a Cartesian coordinate system is shown to be defined with respect to the surface 410 of the receiver system 302. In some embodiments, a mirror, an absorptive layer, or a combination thereof can reside on or proximate to the surface 410.

[0145] In some embodiments, the platen 301 (e.g., the platen portion 301b) can include an acoustic waveguide. In some such embodiments, the platen portion 301b can be configured to transmit ultrasonic waves generated by a target object on the outer surface 205 toward the receiver system 302 via the acoustic waveguide.

[0146] According to some examples, the platen 301 can include one or more anti-reflection layers. As used herein, the term "anti-reflection" refers to light reflection. In other words, an "anti-reflection" layer is a layer configured to reduce light reflection. In some examples, one or more anti-reflection layers can reside on or proximate to the platen 301, such as on or proximate to the outer surface 205.

[0147] Figure 4B and Figure 4CIllustrates an example component of a device according to some additional disclosed embodiments. As with other figures provided herein, Figure 4B and Figure 4C the number, type, and arrangement of the elements shown in are presented only by way of example. In these examples, the device 300 is an Figure 3 instance of the device 300 shown in. According to these examples, the device 300 includes a platen 301, a receiver system 302, and a light source system 304. In these examples, as with Figure 4A the light source system 304 includes a light-emitting portion 304a and a lens 304b. Here, the lens 304b is configured to focus the light 203a emitted by the light-emitting portion 304a into a relatively small cross-sectional area, which increases the intensity of the light 203a received by a target object (such as a finger 206) on the outer surface 205.

[0148] In these examples, the platen 301 includes a platen portion 301a and a platen portion 301b. According to these examples, the platen portion 301a is configured to direct the light 203a from the light source system 304 toward the outer surface 205. In these examples, the platen portion 301b is configured to direct sound waves (including photoacoustic waves) emitted by a target object on the outer surface 205 toward the receiver system 302. In the Figure 4B example shown in, both the platen portion 301a and the platen portion 301b have a conical shape. In the Figure 4C example shown in, both platen portions 301b have a cylindrical shape.

[0149] According to these examples, the platen portion 301a and the light source system 304 are configured to transmit the light 203a from the light source system 304 to the outer surface 205 of the platen 301 along the axis 405a or substantially along the axis 405a. In these examples, the platen portion 301b is configured to transmit sound waves (including but not limited to ultrasonic waves) generated by a target object on the outer surface 205 toward the receiver system 302 along the axis 405b or substantially along the axis 405b. In these examples, the axis 405a is separated from the axis 405b by an angle Θ. In the Figure 4B and Figure 4C example shown in, a Cartesian coordinate system is shown as being defined with respect to the outer surface 205 of the platen 301.

[0150] In the Figure 4B and Figure 4C embodiment shown in, the platen portion 301b includes a sound waveguide. At least a portion of each platen portion 301b is configured to transmit ultrasonic waves generated by a target object on the outer surface 205 toward the receiver system 302 via the sound waveguide. The inventors have determined that in a platen having radial symmetry (such as Figure 4B andFigure 4C The acoustic waveguides formed in (such as those shown in) can increase the intensity of the acoustic waves (including but not limited to ultrasonic energy) received by the receiver system 302.

[0151] According to some examples, the platen 301 can include one or more anti-reflection layers. In some examples, one or more anti-reflection layers can reside on or near the outer surface 205.

[0152] As noted elsewhere herein, in some examples, the device 300 can include a platen 301 configured to separate one or more received arterial ultrasonic waves (such as Figure 2C arterial photoacoustic wave PA4) from one or more other types of received acoustic and photoacoustic waves (such as Figure 2C photoacoustic waves PA1, PA2, PA3, PA5 and PA6, Figure 2C acoustic waves A1 and A2 or a combination of one or more of them).

[0153] Figure 4D An example component of a device according to an additional disclosed embodiment is shown. Like other figures provided herein, Figure 4D the number, type, and arrangement of the elements shown in are presented only by way of example. In this example, the device 300 is Figure 3 an instance of the device 300 shown in. According to this example, the device 300 includes a platen 301, a receiver system 302, and a light source system 304. In this example, the light source system 304 includes a light-emitting portion 304a but does not include a lens 304b. Some alternative embodiments may include a lens 304b or another component configured to couple light from the light-emitting portion 304a to the platen portion 301a.

[0154] In this example, the platen portion 301a includes an optical waveguide 415. In some cases, holes can be formed in the platen portion 301a, and an optical waveguide such as one or more optical fibers can be inserted into the holes. According to some other examples, the platen portion 301a can be manufactured to include the optical waveguide 415. Although other disclosed examples of the device 100 may not be shown as including an optical waveguide, including Figures 4A to 4C , Figure 5 , Figure 7 , Figure 8 and Figures 11A to 15B the examples shown in, some alternative examples of the device 100 can still include one or more waveguides.

[0155] According to some examples, the platen 301 can include one or more anti-reflection layers. In some examples, one or more anti-reflection layers can reside on or near the outer surface 205.

[0156] Figure 5 Shows an example component of a device according to some disclosed embodiments. As with other figures provided herein, Figure 5 the number, type, and arrangement of the elements shown in are presented only by way of example. In this example, device 300 is Figure 3 an instance of the device 300 shown in. According to this example, device 300 includes a platen 301, a receiver system 302, and a light source system 304.

[0157] Figure 5 Shows an example of the platen 301, which is configured to separate one or more arterial ultrasounds from one or more other types of waves received by the receiver system 302. In this example, the outer surface 205 of the platen 301 is configured to receive a target object, such as a finger 206. According to this example, light 203a from the light source system 304 is illuminating the outer surface of the finger 206 on and near the outer surface 205 and the region 505 within the finger 206.

[0158] In this example, light 203b is reflected from the outer surface of the finger 206 towards the receiver system 302. According to this example, light 203a causes the finger 206 to generate a photoacoustic wave PA3 from the surface of the finger 206 and causes the artery 207 to generate an arterial photoacoustic wave PA4 from within the finger 206 at approximately 3 millimeters. The acoustic wave A1 is caused by the echo of the photoacoustic wave PA3 between the receiver system 302 and the finger 206. In some examples, EMI 211 can cause the receiver system 302 to generate an acoustic wave that echoes between the receiver system 302 and the finger 206, or between the receiver system 302 and the outer surface 205 of the platen 301. As can be determined by comparing Figure 5 with Figure 2C it can be determined that Figure 5 only shows some examples of the noise sources and artifacts that may exist in an actual system.

[0159] Figure 6A is a diagram showing the response of a receiver system according to one example to Figure 5 the EMI, light, and acoustic waves represented in. In this example, the horizontal axis represents time in microseconds, and the vertical axis represents amplitude in volts. In this example, the EMI is received before the time represented by the amplitude curve 605. According to this example, the amplitude curve 605 shows amplitude spikes corresponding to the arrival of PA3, PA4, and A1 at the receiver system 302. It can be observed that the amplitude of the signal of interest corresponding to PA4 is lower than the amplitudes of PA3 and A1. However, in some examples, the PA4 can be selectively sampled by using an appropriate range gate delay (RGD) and range gate window (RGW), for example, by using an RGD of approximately 7 microseconds and an RGW of approximately 0.5 microseconds.

[0160] Alternatively or additionally, the thickness of the platen 301 (such as the platen 301 shown in Figure 5 ) may be configured to separate one or more arterial sound waves (such as PA4) from one or more other types of waves (such as PA3 and A1) received by the receiver system 302. The inventors have determined that by making the thickness of the platen 301 at least a minimum thickness, sound waves (such as arterial sound waves) from an object of interest can be separated from other types of waves received by the receiver system 302. The minimum thickness depends on the speed of sound within the platen, the depth of the object(s) of interest, etc.

[0161] Figure 6B FIG. shows example components of a device according to some disclosed embodiments. As with other figures provided herein, Figure 6B the number, type, and arrangement of elements shown in are presented only by way of example. In this example, the device 300 is an instance of the device 300 shown in Figure 3 . According to this example, the device 300 includes a platen 301, a receiver system 302, and a light source system 304 (not shown). According to this example, the platen 301 is an acrylic platen. In this example, the receiver 302 is receiving photoacoustic waves from arteries 1 and 2 within the target object 601, as well as sound waves caused by EMI signals echoing within the platen 301: these sound waves are labeled "EMI round trip" in Figure 6B . The target object 601 can be, for example, a finger or a part of a wrist. As implied by the arterial depth ranges and arterial diameters shown in Figure 6B , the inventors have simulated the time-of-flight of sound waves from arteries in the depth range of 1 to 3 millimeters, each artery having a certain range of diameters.

[0162] Figure 6C is a diagram showing an example of the time-of-flight of sound waves corresponding to each artery size and depth shown in Figure 6B for a range of platen thicknesses. Figure 6B and Figure 6C The platen thicknesses, depths, diameters, etc. cited in are made only by way of example and in no way limit the scope of the present disclosure or any related applications. Figure 6C Also shown is an example of the time-of-flight of the "EMI round trip" sound waves for the same range of platen thicknesses, Figure 6B as represented in. In these examples, the platen thickness ranges from 1 millimeter to approximately 13 millimeters. In Figure 6CIn [description], the cross corresponds to the time-of-flight of artery 1, while the circle corresponds to the time-of-flight of artery 2. The smallest circle corresponds to an artery diameter of 1 mm for artery 2, the largest circle corresponds to an artery diameter of 3 mm for artery 2, and the intermediate circles correspond to artery diameters of 1.5, 2.0, and 2.5 mm for artery 2. Similarly, the smallest cross corresponds to the smallest diameter of artery 1, which is 1.0 mm, and the largest cross corresponds to the largest diameter of artery 1, which is 3.0 mm. In these examples, the artery depth is measured from the center of the artery to the skin surface. It will be understood that the depth of an actual artery is always greater than the diameter of the artery. The diamond shape corresponds to Figure 6B the "EMI round trip" acoustic wave represented in [description].

[0163] The vertical line 605 corresponding to an acrylic platen thickness of approximately 11 mm corresponds to the platen thickness at which the "EMI round trip" acoustic wave arrives after the photoacoustic wave from an artery that is 3 mm deep and 3 mm in diameter. Thus, Figure 6C it is indicated that if the platen 301 is made of acrylic, the platen 301 should be made at least 11 mm thick and preferably thicker than 11 mm (such as 12 mm or greater) in order to distinguish the photoacoustic wave generated by a 3-mm deep artery from the acoustic wave corresponding to the echo caused by EMI.

[0164] Figure 7 An example of a photoacoustic device configured as a component of a smart phone is shown. As with the other figures provided herein, Figure 7 the number, type, and arrangement of the elements shown in [description] are presented by way of example only. In this example, the device 300 is Figure 3 an instance of the device 300 shown in [description].

[0165] In this example, the receiver system 302 and the light source system 304 are located in the device segment 705, which resides between the platen 301 and the backing layer 710. According to this example, the device 300 is configured to receive a target object on the outer surface 205. As implied by the arrow 715, the light emitted by the light source system 304 and the photoacoustic wave from the target object can travel substantially along the Z-axis of the device 300. In this example, the Z-axis of the device 300 is configured to be aligned with the long axis Z' of the smart phone.

[0166] According to this example, the thickness range of the platen 301 can be from 1 mm to 20 mm, the thickness range of the device segment 705 can be from 3 mm to 7 mm, and the thickness range of the backing 710 can be from 1 mm to 10 mm. In this example, the length range of the smart phone along the Z'-axis can be from 120 - 200 mm. However, these dimensional ranges are only examples. As referred to above Figures 5 to 6CAs noted, it may be advantageous for the platen 301 to be at least thick enough to separate the signal of interest (such as the signal caused by arterial photoacoustics) from other artifacts. This minimum platen thickness will depend on the speed of sound in the platen 301 and the depth to the target(s) of interest.

[0167] Figure 8 An example of a photoacoustic device configured for a pen-type implementation is shown. As with other figures provided herein, Figure 8 the number, type, and arrangement of the elements shown are presented by way of example only. In this example, the device 300 is Figure 3 an instance of the device 300 shown in

[0168] In this example, the overall configuration of the receiver system 302, the light source system 304, and the platen 301 is similar to Figure 7 the configuration shown in : the light source system 304 is located in the device segment 705, which resides between the platen 301 and the backing layer 710. According to this example, the device 300 is configured to receive a target object on the outer surface 205.

[0169] In this example, the spring 805 is configured to allow the backing layer 710, the device segment 705, and the platen 301 to move as a unit inside the housing 801 while pressure is applied on the outer surface 205 against a target object (such as a wrist or finger). According to this example, the sensor system 810 is configured to contact the spring 805 and provide a sensor output signal corresponding to forces, pressures, displacements, etc. caused by the displacement of the backing layer 710, the device segment 705, and the platen 301 inside the housing 801. The sensor system 810 may include a motion sensor, a force sensor, or a combination thereof. In some examples, the device may include a display system having one or more displays. The display system may, for example, indicate information from the sensor system 810, information from the receiver system, information corresponding to data received from the receiver system (such as blood pressure or other cardiac data), etc. In some examples, the display system may include one or more displays residing in the housing 801 or on the housing 801 (such as on the side 815 opposite the outer surface 205).

[0170] In some examples, the dimensions of the device segment 705, the platen 301, and the backing layer 710 may be similar to or the same as Figure 7 those shown in : the thickness range of the platen 301 may range from 1 millimeter to 20 millimeters, the thickness range of the device segment 705 may range from 3 millimeters to 7 millimeters, and the thickness range of the backing 710 may range from 1 millimeter to 10 millimeters. In this example, the length of the housing 801 along the Z' axis may range from 40 to 80 millimeters. However, these dimension ranges are merely examples. As referred to above Figures 5 to 6CAs noted, it may be advantageous for the platen 301 to be thick enough to separate an interesting signal such as an arterial photoacoustic wave from other artifacts.

[0171] Figure 9A 、 Figure 9B and Figure 9C Examples of ray tracing inside a target object and two different types of platens are shown. In each example, the device 300 includes a platen 301, a receiver system 302, and a light source system 304 (not shown). As with other figures provided herein, Figures 9A to 9C the number, size, type, and arrangement of the elements shown in Figure 3 are presented only by way of example. In these examples, the device 300 is an instance of the device 300 shown in Figures 9A to 9C According to these examples, rays corresponding to the photoacoustic wave PA are emitted from a point source 905 within the target object 601 in response to light 203a, and the target object 601 can be a finger, a wrist, etc. For ease of illustration and to avoid confusion,

[0172] In Figure 9A the example shown in Figure 9B and Figure 9C the platen 301 does not include an acoustic waveguide. However, in Figure 9A and Figure 9B the example shown in Figure 9C the platen 301 includes an acoustic waveguide 901.

[0173] In all of these examples, the receiver system 302 receives only a small portion of the photoacoustic wave PA emitted from the point source 905. This is partially true because of the relatively small area of the receiver system 302 compared to the 2π steradian area over which the photoacoustic wave PA propagates. Additionally, given the typical sound speeds in the target object 601 and the platen 301 (e.g., approximately 1500 meters per second for a finger and approximately 2800 meters per second for acrylic), the photoacoustic wave PA tends to be refracted away from the receiver system 302 at the target object / platen interface.

[0174] However, compared to the receiver system 302 shown in Figure 9A the receiver systems 302 shown in Figure 9B and Figure 9C that include the waveguide 901 receive a relatively larger portion of the photoacoustic wave PA emitted from the point source 905.

[0175] Figure 10A 、 Figure 10B 、 Figure 10C andFigure 10D Examples of two additional types of platen and corresponding ray tracing diagrams are shown. In each example, the apparatus 300 includes a platen 301, a receiver system 302 ( Figure 10A and Figure 10C not shown in Figures 10A to 10D ) and a light source system 304 ( Figures 10A to 10D not shown in Figure 3 ). As with the other figures provided herein,

[0176] Figure 10A and Figure 10C show different examples of the apparatus 300 in the same orientation, where the x-z plane faces the observer, while Figure 10B and Figure 10D show cross-sectional views in the y-z plane. In these examples, Figure 10A the apparatus 300 shown in Figure 10B is the same as the apparatus 300 shown in Figure 10C and Figure 10D show embodiments of the apparatus 300 that are different from the embodiments shown in Figure 10A and Figure 10B .

[0177] Figures 10A - 10D All show a platen 301 that is generally in the shape of a rectangular prism. However, Figure 10A and Figure 10B include a platen 301 in which the entire outer surface 205 is substantially flat, while Figure 10C and Figure 10D include a platen 301 having a cylindrical groove 1005 within the outer surface 205, with the other portions of the outer surface 205 being substantially flat. In examples such as Figure 10C and Figure 10D , the cylindrical groove serves as a cylindrical acoustic lens. In the example shown in Figure 10D , the target object 601 is a finger that is pressed into the cylindrical groove 1005.

[0178] In some examples, the dimension A representing depth can be 3 mm, 4 mm, 5 mm, 6 mm, etc., while the dimension B can be 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, etc. In some alternative examples, the outer surface 205 of the platen 301 can include a spherical recess, which can serve as a spherical acoustic lens. The inventors have determined that such an acoustic lens can increase the intensity of the photoacoustic waves received by the receiver system 302 by more than twofold compared to the intensity of the photoacoustic waves received by the receiver system 302 in the absence of such an acoustic lens.

[0179] Figure 11A and Figure 11B illustrates example components of an apparatus in accordance with some additional disclosed embodiments. As with other figures provided herein, Figure 11A and Figure 11B the number, type, and arrangement of elements shown are presented by way of example only. In these examples, apparatus 300 is Figure 3 an instance of the apparatus 300 shown in. According to these examples, apparatus 300 includes platen 301, receiver system 302, and light source system 304. In these examples, light source system 304 includes light-emitting portion 304a and lens 304b. Here, lens 304b is configured to focus light 203a emitted by light-emitting portion 304a into a relatively small cross-sectional area, which increases the intensity of light 203a received by a target object (such as finger 206) on outer surface 205 of platen 301.

[0180] In these examples, at least a portion of the outer surface of platen 301 or the acoustic impedance of a material residing on platen 301 is configured to be close to the acoustic impedance of human skin. In Figure 11A the example shown in, the acoustic impedance of gel 1101 on the surface of platen 301 is configured to be close to the acoustic impedance of human skin. Although such a gel can effectively couple acoustic waves generated in a finger or wrist to platen 301, some users may not desire to have such a gel contact their skin. Additionally, the inventors have found that some coupling gels may cause background noise.

[0181] In Figure 11B the example shown in, the solid outer layer 1105 of platen 301 has an acoustic impedance configured to be close to the acoustic impedance of human skin. Compared to embodiments involving coupling gels, such embodiments can provide advantages. These advantages can include wider end-user acceptance and avoidance of background noise that may be caused by certain coupling gels.

[0182] The typical range of the acoustic impedance of human skin is 1.53 - 1.680 megaryls. Thus, in some examples, gel 1101 or outer layer 1105 can have an acoustic impedance in the range of 1.4 - 1.8 megaryls or in the range of 1.5 - 1.7 megaryls.

[0183] According to some examples, the gel 1101 or the outer layer 1105 may have an acoustic impedance between the acoustic impedance of human skin and the acoustic impedance of the inner portion of the platen 301. For example, if the inner portion of the platen 301 is made of acrylic and has an acoustic impedance in the range of 3.08 - 3.26 megarays, then the gel 1101 or the outer layer 1105 may have an acoustic impedance in the range of 1.7 - 3.08 megarays. In another example, if the inner portion of the platen 301 is made of polycarbonate and has an acoustic impedance in the range of 2.69 - 2.7 megarays, then the gel 1101 or the outer layer 1105 may have an acoustic impedance in the range of 1.7 - 2.69 megarays.

[0184] In some examples, the outer layer 1105 may include a polymer of the silicone family, such as polydimethylsiloxane (PDMS), which is also known as dimethicone. According to some examples, the outer layer 1105 may include Aqualene TM , a material provided by InnovationPolymers, Aqualink TM 100, Aqualink TM 200 or similar materials.

[0185] Alternatively or additionally, in some examples, the outer layer 1105 may be configured to conform to the surface of human skin. In some such examples, the outer layer 1105 may have material properties similar to putty or chewing gum. In some such examples, the outer layer 1105 may be configured to plastically deform when subjected to stress caused by a typical finger press, such as a finger press in the range of 50 to 500 grams of force.

[0186] As noted elsewhere herein, some of the disclosed examples of the device 300 include a noise reduction system 305. In some examples, the noise reduction system 305 may include one or more noise reduction elements configured to at least partially decouple acoustic energy generated by the light source system 304, electrical energy generated by the light source system 304, light generated by the light source system 304, or a combination thereof from the receiver system 302.

[0187] Figure 12 , Figure 13 and Figure 14 illustrate the elements of a device including noise reduction elements. In each example, the device 300 also includes a platen 301, a receiver system 302, and a light source system 304. In these examples, the light source system 304 includes at least a light emitting element 304a and a drive circuitry 1204. As with the other figures provided herein, Figure 12 , Figure 13 and Figure 14 the number, size, type, and arrangement of the elements shown are presented by way of example only. In these examples, the device 300 isFigure 3 An example of the device 300 shown in

[0188] In Figure 12 the device includes noise reduction elements 1205a and 1205b. In this example, the noise reduction element 1205a is a light shield that at least partially shields the receiver system 302 from the light 203a emitted by the light emitting element 304a. According to this example, the noise reduction element 1205b is configured to attenuate at least some of the sound waves that would otherwise be transmitted to the receiver system 302.

[0189] However, despite the presence of the noise reduction elements 1205a and 1205b, a significant amount of acoustic noise 1201 still travels from the drive circuitry 1204 to the receiver system 302. As Figure 12 implied by the path through which the arrow representing the acoustic noise 1201 passes in

[0190] some of the acoustic noise 1201 is transmitted from the drive circuitry 1204 to the receiver system 302 via the support structure 1210 that connects the drive circuitry 1204 to the platen 301, and some of the acoustic noise 1201 is transmitted from the drive circuitry 1204 to the receiver system 302 via the support structure 1215 that connects the light emitting element 304a to the platen 301.

[0191] In Figure 13 the example shown in

[0192] the inventors have observed that compared to the example shown in Figure 12 the acoustic noise transmitted from the drive circuitry 1204 to the receiver system 302 is significantly reduced by the presence of the noise reduction elements 1205c, 1205d, and 1205e. In some examples, the amplitude of the acoustic noise can be reduced from approximately 1 volt to approximately 0.2 volts.

[0193] In Figure 14 the example shown in, device 300 includes noise reduction element 1205f and Figure 13 noise reduction elements 1205a through 1205e. In this example, noise reduction element 1205f includes one or more electromagnetic shielding transmission lines configured to reduce electromagnetic interference from light source system 304 that would otherwise be received by receiver system 302. In this example, the one or more electromagnetic shielding transmission lines are included in a cable and include connections for both a positive connection and a negative connection for light emitting element 304a. According to this example, each electromagnetic shielding transmission line is grounded.

[0194] The inventors have observed that, compared to the example shown in Figure 13 , acoustic noise transmitted from drive circuit system 1204 to receiver system 302 is further reduced by the presence of noise reduction element 1205f. In some examples, the amplitude of the acoustic noise can be reduced from approximately 0.2 volts to approximately 0.1 volts.

[0195] Figure 15A and Figure 15B show examples of devices having different types of light source systems. As with other figures provided herein, Figure 15A and Figure 15B the number, size, type, and arrangement of elements shown are presented by way of example only. In these examples, device 300 is an instance of device 300 shown in Figure 3 .

[0196] In Figure 15A the example shown in, light source system 304 does not include lens 304b, while in Figure 15B the example shown in, light source system 304 includes lens 304b. In this example, lens 304b is a collimating lens such that light 203a exiting lens 304b is collimated light. Thus, Figure 15A the light 203a shown in is scattered over a relatively large area 505a of finger 206, and Figure 15B the light 203a shown in is concentrated in a relatively small area 505b of finger 206.

[0197] The present inventor has found that using a lens 304b that focuses light 203a onto a relatively small area of a target object increases the signal-to-noise ratio of desired signals such as arterial signals. This is thought to be due in part to the illumination of a relatively large portion of the (multiple) target features (such as arteries) when the target object is illuminated using a light source system that does not have the lens 304b. Illumination of a relatively large portion of the target features (which may be at various depths beneath the skin) causes the resulting photoacoustic signal to be smeared in time. In addition, when using a light source system that does not have the lens 304b to illuminate the target object, a relatively large percentage of the incident light does not reach the (multiple) target features. In addition, focusing of the light increases the flux on the target features.

[0198] Figure 16A A graph showing the blood light absorption coefficient versus the wavelengths of hemoglobin (Hb) and oxyhemoglobin (HbO2) is shown. It can be observed that Hb has an absorption peak at approximately 750 nanometers and an even higher absorption level between 650 and 700 nanometers. HbO2 has an absorption peak at approximately 930 nanometers or 940 nanometers, with decreasing absorption levels at shorter and longer wavelengths. Although the Hb absorption levels at approximately 930 nanometers or 940 nanometers are not peaks, they are still a significant portion of the absorption levels of HbO2 in the same wavelength range.

[0199] Figure 16B A table showing the maximum permissible exposure (MPE) guidelines for the 808 nanometer and 940 nanometer wavelengths is shown. One can observe that the maximum MPE values for the per-pulse fluence and average power density at the 808 nanometer wavelength are approximately half of the maximum MPE values at the 940 nanometer wavelength. Thus, considering the relatively high MPE limits and the reasonably high absorption levels of both HbO2 and Hb, a light source (such as a laser diode) configured to emit light at wavelengths between 900 and 950 nanometers may be desirable for PAPG applications.

[0200] Figure 17A A graph showing an example of a photoacoustic (PA) signal received by a receiver system is shown. During the first few microseconds of this graph (including the time indicated by the ellipse 1701 in Figure 17A ), large peaks with the following contributions can be observed: crosstalk from the drive circuitry 1204 of the light source system 304 to the receiver system 302, such as described above with reference to Figures 12 to 14 , and irradiation of the receiver system 302 by light from the light source system 304. The tails of these peaks and the multipath of these peaks may cover the desired PA signal in some cases, thus reducing the signal-to-noise ratio (SNR) of the desired PA signal. Crosstalk from the drive circuitry 1204 to the receiver system 302 tends to scale with the current level in the drive circuitry 1204.

[0201] Figure 17B Shows an example of a single-junction laser diode implementation. Figure 17C Shows an example of a multi-junction laser diode implementation, in which the multi-junction laser diode implementation includes 5 junctions. Other multi-junction laser diode implementations may include more or fewer junctions, such as 2, 3, 4, 6, 7, 8, 9, or 10 junctions. The laser diode implementation may include, for example, a VCSEL or an edge-emitting laser (EEL). Increasing the number of junctions increases the voltage but decreases the current. Thus, the multi-junction laser diode implementation can reduce the crosstalk level from the drive circuitry 1204 to the receiver system 302, thereby providing a higher SNR.

[0202] Figure 18 Is a flowchart showing examples of some disclosed operations. Figure 18 The blocks of (and the blocks of other flowcharts provided herein) may be performed, for example, by Figure 3 the apparatus 300 of or by a similar apparatus. Like other methods disclosed herein, Figure 18 the method outlined in may include more or fewer blocks than those indicated. In addition, the blocks of the methods disclosed herein are not necessarily performed in the order indicated. In some cases, Figure 18 one or more of the blocks shown in may be performed concurrently.

[0203] In this example, block 1805 involves controlling a light source system by a control system to emit light toward a target object on or near an outer surface of a platen. Depending on the particular example, the target object may be a finger, a wrist, etc. According to this example, block 1810 involves receiving, by the control system, a signal from an ultrasonic receiver system that corresponds to ultrasonic waves generated by the target object in response to the light emitted by the light source system.

[0204] According to this example, block 1815 involves identifying, by the control system, an arterial signal from the ultrasonic receiver system that corresponds to ultrasonic waves generated by blood in an artery of the target object. For example, the arterial signal may be identified to achieve an RGD corresponding to an expected depth into the artery.

[0205] In this example, block 1820 involves estimating, by the control system, one or more cardiac characteristics based at least in part on the arterial signal. In some examples, block 1820 may involve estimating blood pressure based at least in part on the arterial signal. According to some examples, block 1820 or another aspect of method 1800 may involve extracting and evaluating heart rate waveform (HRW) features.

[0206] Figure 19 Shows an example of heart rate waveform (HRW) features that may be extracted according to some embodiments.Figure 19 The horizontal axis represents time, and the vertical axis represents signal amplitude. The cardiac cycle is indicated by the time between adjacent peaks of the HRW. The systolic and diastolic time intervals are indicated below the horizontal axis. During the systolic phase of the cardiac cycle, as the pulse propagates along the artery through a specific location, the arterial wall expands according to the pulse waveform and the elastic properties of the arterial wall. Associated with the expansion is a corresponding increase in the blood volume at the specific location or region, and as the blood volume increases, there are associated changes in one or more properties in that region. Conversely, during the diastolic phase of the cardiac cycle, the blood pressure in the artery decreases and the arterial wall contracts. Associated with the contraction is a corresponding decrease in the blood volume at the specific location, and as the blood volume decreases, there are associated changes in one or more properties in that region.

[0207] Figure 19 The HRW features illustrated in involve the widths of the systolic and / or diastolic portions of the HRW curve at various "heights", which are indicated as a percentage of the maximum amplitude. For example, the SW50 feature is the width of the systolic portion of the HRW curve at the "height" of 50% of the maximum amplitude. In some embodiments, the HRW features used for blood pressure estimation may include some or all of the SW10, SW25, SW33, SW50, SW66, SW75, DW10, DW25, DW33, DW50, DW66, and DW75 HRW features. In other embodiments, additional HRW features may be used for blood pressure estimation. In some cases, such additional HRW features may include the sum and ratio of SW and DW at one or more "heights", e.g., (DW75 + SW75), DW75 / SW75, (DW66 + SW66), DW66 / SW66, (DW50 + SW50), DW50 / SW50, (DW33 + SW33), DW33 / SW33, (DW25 + SW25), DW25 / SW25, and / or (DW10 + SW10), DW10 / SW10. Other embodiments may use other HRW features for blood pressure estimation. In some cases, 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.

[0208] Figure 20An example of a device that can be used in a system for estimating blood pressure based at least in part on pulse transit time (PTT) is shown. As with the other figures provided herein, the number, type, and arrangement of elements are presented by way of example only. According to this example, system 2000 includes at least two sensors. In this example, system 2000 includes at least an electrocardiogram sensor 2005 and a device 2010 configured to be mounted on the finger of a person 2001. In this example, device 2010 is or includes a device configured to perform at least some of the PAPG methods disclosed herein. For example, device 2010 can be or can include device 200 of FIG. 2 or a similar device.

[0209] As pointed out in FIG. 2020, PAT includes two components: pre-ejection period (PEP, the time required to convert an electrical signal into mechanical pumping force and isovolumetric contraction to open the aortic valve) and PTT. The start time of PAT can be estimated based on the QRS complex - the electrical signal characteristic of ventricular electrical stimulation. As shown in FIG. 2020, in this example, the start of the pulse arrival time (PAT) can be calculated based on the R-wave peak measured by the electrocardiogram sensor 2005, and the end of PAT can be detected via analysis of the signal provided by device 2010. 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 2010 and the tangent of the maximum slope / first derivative of the sensor signal after the time of this minimum.

[0210] There are many known algorithms for blood pressure estimation based on PTT and / or PAT, some of which are summarized in Table 1 of "Cuff-Less and Continuous Blood Pressure Monitoring: a Methodological Review" by Sharma, M. et al. on May 21, 2017, in Multidisciplinary Digital Publishing Institute (MDPI) Technologies, and these algorithms are described in the corresponding text on pages 5 to 10 of "Sharma", all of which are hereby incorporated by reference.

[0211] Other embodiments of system 2000 may not include the electrocardiogram sensor 2005. In some such embodiments, the device 2015 configured to be mounted on the wrist of a person 2001 may be or may include a device configured to perform at least some of the PAPG methods disclosed herein. For example, the device 2015 may be or may include the device 200 of FIG. 2 or a similar device. According to some such examples, the device 2015 may include a light source system and two or more ultrasonic receivers. In some examples, the device 2015 may include at least one ultrasonic receiver array.

[0212] Figure 21 A cross-sectional side view 2100 of a graphical representation showing a portion of an artery, with a pulse 2102 propagating through the artery 2100. Figure 21 The box arrows in show the direction of blood flow and pulse propagation. As shown, the propagating pulse 2102 causes strain in the arterial wall 2104, which manifests as an increase in the diameter (and thus cross-sectional area) of the arterial wall - referred to as "dilation". The spatial length L of the actual propagating pulse along the artery (in the direction of blood flow) is typically comparable to the length of the limb, such as the distance from the subject's shoulder to the subject's wrist or finger, and is typically less than one meter (m). However, the length L of the propagating pulse can vary significantly between different subjects and, for a given subject, can vary significantly over time depending on various factors. The spatial length L of the pulse will generally decrease as the distance from the heart increases until the pulse reaches the capillaries.

[0213] As described above, some particular embodiments relate to devices, systems, and methods for estimating blood pressure or other cardiovascular characteristics based on an estimate of the arterial dilation waveform. The terms "estimate", "measure", "calculate", "infer", "derive", "evaluate", "determine", and "monitor" may be used interchangeably herein, where appropriate, unless otherwise specified. Similarly, derivatives from the roots of these terms may also be used interchangeably, where appropriate; for example, the terms "estimate", "measure", "calculate", "infer", and "determine" may also be used interchangeably herein. In some embodiments, the pulse wave velocity (PWV) of the propagating pulse can be estimated by measuring the pulse transit time (PTT) of the pulse as it propagates from a first physical location along the artery to a second, more distal physical location along the artery. It will be understood that this PTT is different from the PTT described above with reference to FIG. 15. However, either version of the PTT can be used for the purpose of blood pressure estimation. Assuming that the physical distance between the first physical location and the second physical location is determinable, the PWV can be estimated as the physical spatial distance traveled by the pulse divided by the time it takes for the pulse to traverse that physical spatial distance The quotient of the time taken (PTT). Generally, a first sensor located at a first physical position is used to determine the start time (also referred to herein as the "first time position") at the point where the pulse arrives at or propagates through the first physical position. A second sensor at a second physical position is used to determine the end time (also referred to herein as the "second time position") at the point where the pulse arrives at or propagates through the second physical position and continues through the remainder of the arterial branch. In such an example, the PTT represents the time distance (or time difference) between the first time position and the second time position (start time and end time).

[0214] The fact that the arterial expansion waveform is measured at two different physical positions means that the estimated PWV inevitably represents the average over the entire path distance that the pulse travels between the first physical position and the second physical position Specifically, PWV generally depends on many factors, including the density ρ of the blood, the stiffness E (or the opposite of elasticity) of the arterial wall, the arterial diameter, the thickness of the arterial wall, and blood pressure. Since the arterial wall elasticity and the baseline resting diameter (e.g., the diameter at the end of ventricular diastole) vary widely throughout the arterial system, the PWV estimate obtained from PTT measurements is inherently an average (averaged over the entire path length between the two positions where the measurements are performed along).

[0215] In traditional methods for obtaining PWV, an electrocardiogram (ECG) sensor that detects electrical signals from the heart is used at the heart to obtain the start time of the pulse. For example, the start time can be estimated based on the QRS complex - the electrical signal characteristics of ventricular electrical stimulation. In such a method, a different sensor located at a second position (e.g., a finger) is typically used to obtain the end time of the pulse. As will be understood by those of ordinary skill in the art, there are many arterial discontinuities, branches, and variations along the entire path length from the heart to the finger. Along the various segments of the entire path length from the heart to the finger, the PWV can change by up to or more than an order of magnitude. Therefore, the PWV estimate based on such a long path length is unreliable.

[0216] In various embodiments described herein, a PTT estimate is obtained based on measurements (also referred to as "arterial distension data" or more generally as "sensor data") associated with arterial distension signals obtained by each of a first arterial distension sensor 2106 and a second arterial distension sensor 2108, the first arterial distension sensor 2106 and the second arterial distension sensor 2108 being respectively proximate a first physical location and a second physical location along an artery of interest. In some particular embodiments, the first arterial distension sensor 2106 and the second arterial distension sensor 2108 are advantageously positioned proximate the first physical location and the second physical location where the arterial properties (such as wall elasticity and diameter) of the artery of interest can be considered or assumed to be relatively constant between the first physical location and the second physical location. Thus, the PWV calculated based on the PTT estimate is more representative of the actual PWV along a particular segment of the artery. Subsequently, the blood pressure P estimated based on the PWV is more representative of the true blood pressure. In some embodiments, the distance between the first arterial distension sensor 2106 and the second arterial distension sensor 2108 (and thus the distance between the first location and the second location along the artery) can range from about 1 centimeter (cm) to several tens of centimeters - long enough to distinguish the arrival of the pulse at the first physical location from the arrival of the pulse at the second physical location, but close enough to provide sufficient assurance of arterial consistency. In some specific embodiments, the distance between the first arterial distension sensor 2106 and the second arterial distension sensor 2108 can range from about 1 cm to about 30 cm, and in some embodiments, is less than or equal to about 20 cm, and in some embodiments, is less than or equal to about 10 cm, and in some specific embodiments, is less than or equal to about 5 cm. In some other embodiments, the distance between the first arterial distension sensor 2106 and the second arterial distension sensor 2108 can be less than or equal to 1 cm, such as about 0.1 cm, about 0.25 cm, about 0.5 cm, or about 0.75 cm. By way of reference, a typical PWV can be about 15 meters per second (m / s). Using a dynamic monitoring device in which the first arterial distension sensor 2106 and the second arterial distension sensor 2108 are separated by a distance of about 5 cm and assuming a PWV of about 15 m / s implies a PTT of about 3.3 milliseconds (ms).

[0217] The distance between the first arterial distension sensor 2106 and the second arterial distension sensor 2108 The magnitude values can be pre-programmed respectively into the memory within the monitoring device incorporating the sensor (e.g., the memory of the control system 206 as described above with reference to FIG. 2 or a memory configured to communicate with the control system 206). As will be understood by those of ordinary skill in the art, in such an embodiment, the spatial length L of the pulse can be greater than the distance from the first arterial dilation sensor 2106 to the second arterial dilation sensor 2108. . Thus, although Figure 21 the illustrated pulse 2102 shown in [reference] is shown as having a spatial length L comparable to the distance between the first arterial dilation sensor 2106 and the second arterial dilation sensor 2108, in fact each pulse can typically have a spatial length L that is greater than and even much greater than (e.g., by about an order of magnitude or more) the distance between the first arterial dilation sensor 2106 and the second arterial dilation sensor 2108. of spatial length L.

[0218] Example embodiments are described in the following numbered clauses:

[0219] 1. An apparatus, comprising: a platen; a light source system configured to provide light to a target object on an outer surface of the platen; an ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to light from the light source system; and a mirror layer residing between the ultrasonic receiver system and the platen, the mirror layer being configured to reflect light from the light source system.

[0220] 2. The apparatus according to clause 1, wherein the platen is configured to increase the intensity of ultrasonic energy received by at least a portion of the ultrasonic receiver system.

[0221] 3. The apparatus according to clause 1 or clause 2, wherein the platen includes a sound waveguide.

[0222] 4. The apparatus according to any one of clauses 1 to 3, wherein the platen includes a sound lens.

[0223] 5. The apparatus according to clause 4, wherein the sound lens resides on or proximate to the outer surface of the platen.

[0224] 6. The apparatus according to clause 4 or clause 5, wherein the sound lens includes a spherical lens or a cylindrical lens.

[0225] 7. The apparatus according to any one of clauses 1 to 6, wherein the platen, the light source system, or a combination thereof is configured to transmit light from the light source system to the outer surface of the platen along a first axis or substantially along a first axis.

[0226] 8. The device according to clause 7, wherein the platen is configured to transmit ultrasonic waves generated by the target object along a second axis or substantially along the second axis, the second axis being different from the first axis.

[0227] 9. The device according to clause 7, wherein the platen is configured to transmit ultrasonic waves generated by the target object along a second axis or substantially along the second axis, the second axis being parallel to the first axis.

[0228] 10. The device according to any one of clauses 1 to 9, wherein at least one surface of the platen includes an anti-reflection layer.

[0229] 11. The device according to any one of clauses 1 to 10, wherein the ultrasonic receiver system includes two or more receiver elements adjacent to a region of the platen, and light from the light source is transmitted through the region of the platen towards the target object.

[0230] 12. The device according to any one of clauses 1 to 11, wherein the platen, the light source system, or a combination thereof is configured to transmit light in the near-infrared range.

[0231] 13. The device according to any one of clauses 1 to 12, wherein the device is or includes a mobile device, and wherein an outer surface of the platen corresponds to or is close to an outer surface of the mobile device.

[0232] 14. The device according to clause 13, wherein the mobile device includes a cellular phone.

[0233] 15. The device according to clause 13, wherein the mobile device includes a pen or a stylus.

[0234] 16. The device according to clause 15, wherein the pen or the stylus includes a force sensor, a motion sensor, a spring, or a combination thereof.

[0235] 17. The device according to any one of clauses 1 to 16, wherein the thickness of the platen, the speed of sound of the platen, or a combination thereof is configured to separate ultrasonic waves generated by blood in an artery from other ultrasonic waves.

[0236] 18. The device according to any one of clauses 1 to 17, wherein the platen provides an ultrasonic sound attenuation in the range of 0.3 to 3.0 decibels per centimeter per megahertz.

[0237] 19. The device according to any one of clauses 1 to 18, wherein the acoustic impedance of at least the outer surface of the platen is configured to approximate the acoustic impedance of human skin.

[0238] 20. The device according to any one of clauses 1 to 19, wherein at least the outer surface of the platen is configured to conform to the surface of human skin.

[0239] 21. The device according to any one of clauses 1 to 20, wherein the speed of sound in the platen is in the range from 800 to 3000 meters per second.

[0240] 22. The device according to any one of clauses 1 to 21, further comprising a control system configured to: control the light source system to emit light; receive a signal from the ultrasonic receiver system corresponding to the ultrasonic waves generated by the target object; identify an arterial blood signal from the ultrasonic receiver system corresponding to the ultrasonic waves generated by the blood in the artery of the target object; and estimate one or more cardiac characteristics at least partially based on the arterial blood signal.

[0241] 23. The device according to any one of clauses 1 to 21, further comprising a control system configured to: control the light source system to emit light; receive a signal from the ultrasonic receiver system corresponding to the ultrasonic waves generated by the target object; identify one or more arterial wall signals from the ultrasonic receiver system corresponding to the ultrasonic waves generated by one or more arterial walls of the target object; and estimate one or more cardiac characteristics at least partially based on the one or more arterial wall signals.

[0242] 24. The device according to any one of clauses 1 to 23, further comprising one or more optical waveguides.

[0243] 25. The device according to clause 24, wherein at least a portion of one of the one or more optical waveguides resides in a portion of the platen.

[0244] 26. A device comprising: a platen; a light source component for providing light to a target object on or near the outer surface of the platen; an ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to light from the light source component; and a mirror layer residing between the ultrasonic receiver system and the platen, the mirror layer being configured to reflect light from the light source component.

[0245] 27. The device according to clause 26, wherein the platen is configured to increase the intensity of the ultrasonic energy received by at least a portion of the ultrasonic receiver system.

[0246] 28. The device according to clause 26 or clause 27, wherein the platen includes an acoustic waveguide.

[0247] 29. The device according to any one of clauses 26 to 28, wherein the platen includes an acoustic lens.

[0248] 30. A method includes: controlling, by a control system, a light source system to emit light toward a target object on an outer surface of a platen; receiving, by the control system, a signal from an ultrasonic receiver system corresponding to ultrasonic waves generated by the target object; identifying, by the control system, an arterial signal from the ultrasonic receiver system, the arterial signal corresponding to ultrasonic waves generated by blood in an artery of the target object, ultrasonic waves generated by one or more arterial walls of the target object, or a combination thereof; and estimating, by the control system, one or more cardiac characteristics based at least in part on the arterial blood signal.

[0249] 31. The method according to clause 30, wherein controlling the light source system to emit light includes controlling the light source system to emit laser pulses.

[0250] 32. An apparatus includes: a platen; a light source system configured to provide light to a target object on an outer surface of the platen, the light source system including one or more laser diodes and a drive circuit; an ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to light from the light source system; and a noise reduction system including one or more noise reduction elements configured to at least partially decouple acoustic energy generated by the light source system, electrical energy generated by the light source system, light generated by the light source system, or a combination thereof from the ultrasonic receiver system.

[0251] 33. The apparatus according to clause 32, wherein the noise reduction system includes one or more electromagnetic shielding transmission lines of the light source system.

[0252] 34. The apparatus according to clause 33, wherein the one or more electromagnetic shielding transmission lines are configured to reduce electromagnetic interference from the light source system received by the ultrasonic receiver system.

[0253] 35. The apparatus according to any one of clauses 32 to 34, wherein the noise reduction system includes one or more air gaps between the light source system and the ultrasonic receiver system.

[0254] 36. The apparatus according to any one of clauses 32 to 35, wherein the noise reduction system includes one or more sound absorbing layers configured to reduce acoustic energy generated by the light source system and received by the ultrasonic receiver system.

[0255] 37. The apparatus according to clause 36, wherein at least one of the one or more sound absorbing layers resides in or proximate to the ultrasonic receiver system.

[0256] 38. The apparatus according to clause 36 or clause 37, wherein at least one of the one or more sound absorbing layers resides in or proximate to the light source system.

[0257] 39. The device according to any one of clauses 32 - 38, wherein the noise reduction system comprises one or more light absorbing layers configured to reduce the amount of light generated by the light source system and received by the ultrasonic receiver system.

[0258] 40. The device according to clause 39, wherein at least one of the one or more light absorbing layers resides in or proximate to the ultrasonic receiver system.

[0259] 41. The device according to any one of clauses 32 to 40, wherein the noise reduction system comprises one or more reflective layers configured to reduce the amount of light generated by the light source system and received by the ultrasonic receiver system.

[0260] 42. The device according to clause 41, wherein at least one of the one or more reflective layers resides between the platen and at least a portion of the ultrasonic receiver system.

[0261] 43. The device according to any one of clauses 32 to 42, wherein the light source system comprises at least one multi - junction laser diode.

[0262] 44. The device according to any one of clauses 32 to 43, wherein the light source system comprises a lens configured to collimate the light generated by the light source system.

[0263] 45. The device according to any one of clauses 32 to 44, wherein the platen, the light source system, or a combination thereof is configured to transmit light from the light source system to the outer surface of the platen along a first axis or substantially along the first axis.

[0264] 46. The device according to clause 45, wherein the platen is configured to transmit ultrasonic waves generated by the target object along a second axis or substantially along the second axis, the second axis being different from the first axis.

[0265] 47. The device according to clause 45, wherein the platen is configured to transmit ultrasonic waves generated by the target object along a second axis or substantially along the second axis, the second axis being parallel to the first axis.

[0266] 48. The device according to clause 47, wherein the ultrasonic receiver system comprises two or more receiver elements adjacent to a region of the platen, and light from the light source system is transmitted through the region of the platen towards the target object.

[0267] 49. The apparatus according to any one of clauses 32 to 48 further includes a control system configured to: control the light source system to emit light; receive a signal from the ultrasonic receiver system corresponding to the ultrasonic waves generated by the target object; identify one or more arterial wall signals from the ultrasonic receiver system corresponding to the ultrasonic waves generated by one or more arterial walls of the target object; and estimate one or more cardiac characteristics at least partially based on the one or more arterial wall signals.

[0268] 50. The apparatus according to any one of clauses 32 to 49, wherein the light source system is configured to transmit light in a wavelength range of 800 to 900 nanometers.

[0269] 51. The apparatus according to any one of clauses 32 to 50, wherein the light source system is configured to transmit light in a wavelength range of 500 to 600 nanometers.

[0270] 52. The apparatus according to any one of clauses 32 to 51, wherein the light source system includes one or more light emitting diodes, one or more vertical cavity surface emitting lasers, one or more edge emitting lasers, or a combination thereof.

[0271] 53. The apparatus according to any one of clauses 32 to 52, wherein the drive circuit is configured to cause the light source system to emit light pulses having a pulse width in a range from 3 nanoseconds to 1000 nanoseconds.

[0272] 54. The apparatus according to any one of clauses 32 to 53, wherein the drive circuit is configured to cause the light source system to emit light pulses at a pulse repetition frequency in a range from 1 kilohertz to 100 kilohertz.

[0273] 55. The apparatus according to any one of clauses 32 to 54, wherein the apparatus is a mobile device or includes a mobile device, and wherein the outer surface of the platen corresponds to or is close to the outer surface of the mobile device.

[0274] 56. The apparatus according to clause 55, wherein the mobile device includes a cellular phone.

[0275] 57. The apparatus according to clause 55, wherein the mobile device includes a pen or a stylus.

[0276] 58. The apparatus according to clause 57, wherein the pen or the stylus includes a force sensor, a motion sensor, a spring, or a combination thereof.

[0277] 59. The device according to any one of clauses 32 to 58 further includes a control system configured to: control the light source system to emit light; receive a signal from the ultrasonic receiver system corresponding to the ultrasonic waves generated by the target object; identify one or more arterial signals from the ultrasonic receiver system, the one or more arterial signals corresponding to ultrasonic waves generated by blood in the arteries of the target object, ultrasonic waves generated by one or more arterial walls, or a combination thereof; and estimate one or more cardiac characteristics at least partially based on the one or more arterial signals.

[0278] 60. The device according to any one of clauses 32 to 59 further includes one or more optical waveguides.

[0279] 61. The device according to clause 60, wherein at least a portion of one of the one or more optical waveguides resides in a portion of the platen.

[0280] 62. A device includes: a platen; a light source component for providing light to a target object on the outer surface of the platen, the light source component including one or more laser diodes and a drive circuit; an ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to light from the light source component; and a noise reduction system including one or more noise reduction elements configured to at least partially decouple acoustic energy generated by the light source component, electrical energy generated by the light source component, light generated by the light source component, or a combination thereof from the ultrasonic receiver system.

[0281] 63. The device according to clause 62, wherein the noise reduction system includes one or more electromagnetic shielding transmission lines of the light source component.

[0282] 64. The device according to clause 63, wherein the one or more electromagnetic shielding transmission lines are configured to reduce electromagnetic interference received by the ultrasonic receiver system from the light source component.

[0283] 65. A method includes: controlling, by a control system, a light source system to emit light to a target object on the outer surface of a platen; receiving, by the control system, a signal from an ultrasonic receiver system corresponding to ultrasonic waves generated by the target object; identifying, by the control system, an arterial signal from the ultrasonic receiver system, the arterial signal corresponding to ultrasonic waves generated by blood in the arteries of the target object, ultrasonic waves generated by one or more arterial walls of the target object, or a combination thereof; and estimating, by the control system, one or more cardiac characteristics at least partially based on the arterial blood signal.

[0284] 66. The method according to clause 65, wherein controlling the light source system to emit light includes controlling the light source system to emit laser pulses.

[0285] 67. A device, comprising: a platen; a light source system configured to provide light to a target object on an outer surface of the platen, the light source system including one or more laser diodes and a drive circuit, the one or more laser diodes including at least one multi-junction laser diode; and an ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to light from the light source system.

[0286] 68. The device according to clause 67, further comprising a noise reduction system including one or more noise reduction elements configured to at least partially decouple acoustic energy generated by the light source system, electrical energy generated by the light source system, light generated by the light source system, or a combination thereof from the ultrasonic receiver system.

[0287] 69. The device according to clause 68, wherein the noise reduction system includes one or more electromagnetic shielding transmission lines of the light source system.

[0288] 70. The device according to clause 69, wherein the one or more electromagnetic shielding transmission lines are configured to reduce electromagnetic interference from the light source system received by the ultrasonic receiver system.

[0289] 71. The device according to any one of clauses 68 to 70, wherein the noise reduction system includes one or more air gaps between the light source system and the ultrasonic receiver system.

[0290] 72. The device according to any one of clauses 68 to 71, wherein the noise reduction system includes one or more sound-absorbing layers configured to reduce acoustic energy generated by the light source system and received by the ultrasonic receiver system.

[0291] 73. The device according to clause 72, wherein at least one of the one or more sound-absorbing layers resides in or near the ultrasonic receiver system.

[0292] 74. The device according to clause 72 or clause 73, wherein at least one of the one or more sound-absorbing layers resides in or near the light source system.

[0293] 75. The device according to any one of clauses 68 to 74, wherein the noise reduction system includes one or more light-absorbing layers configured to reduce the amount of light generated by the light source system and received by the ultrasonic receiver system.

[0294] 76. The device according to clause 75, wherein at least one of the one or more light-absorbing layers resides in or near the ultrasonic receiver system.

[0295] 77. The device according to any one of clauses 68 to 76, wherein the noise reduction system includes one or more reflective layers configured to reduce the amount of light generated by the light source system and received by the ultrasonic receiver system.

[0296] 78. The device according to clause 77, wherein at least one of the one or more reflective layers resides between the platen and at least a portion of the ultrasonic receiver system.

[0297] 79. The device according to any one of clauses 67 to 78, wherein the light source system includes a lens configured to collimate the light generated by the light source system.

[0298] 80. The device according to any one of clauses 67 to 79, wherein the platen, the light source system, or a combination thereof is configured to transmit light from the light source system to an outer surface of the platen along a first axis or substantially along the first axis.

[0299] 81. The device according to clause 80, wherein the platen is configured to transmit ultrasonic waves generated by the target object along a second axis or substantially along the second axis, the second axis being different from the first axis.

[0300] 82. The device according to clause 80, wherein the platen is configured to transmit ultrasonic waves generated by a target object along a second axis or substantially along the second axis, the second axis being parallel to the first axis.

[0301] 83. The device according to any one of clauses 67 to 82, further comprising a control system configured to: control the light source system to emit light; receive a signal from the ultrasonic receiver system corresponding to ultrasonic waves generated by a target object; identify one or more arterial wall signals from the ultrasonic receiver system corresponding to ultrasonic waves generated by one or more arterial walls of the target object; and estimate one or more cardiac characteristics at least in part based on the one or more arterial wall signals.

[0302] 84. The device according to any one of clauses 67 to 83, wherein the ultrasonic receiver system includes two or more receiver elements adjacent to a region of the platen, and light from the light source system is transmitted through the region of the platen towards the target object.

[0303] 85. The device according to any one of clauses 67 to 84, wherein the light source system is configured to transmit light in a wavelength range of 800 to 950 nanometers.

[0304] 86. The device according to any one of clauses 67 to 85, wherein the light source system is configured to transmit light in a wavelength range of 500 to 600 nanometers.

[0305] 87. The device according to any one of clauses 67 to 86, wherein the light source system includes one or more light-emitting diodes, one or more vertical-cavity surface-emitting lasers, one or more edge-emitting lasers, or a combination thereof.

[0306] 88. The device according to any one of clauses 67 to 87, wherein the drive circuit is configured to cause the light source system to emit light pulses having a pulse width in a range from 3 nanoseconds to 1000 nanoseconds.

[0307] 89. The device according to any one of clauses 67 to 88, wherein the drive circuit is configured to cause the light source system to emit light pulses at a pulse repetition frequency in a range from 1 kilohertz to 100 kilohertz.

[0308] 90. The device according to any one of clauses 67 to 89, wherein the device is or includes a mobile device, and wherein the outer surface of the platen corresponds to or is close to the outer surface of the mobile device.

[0309] 91. The device according to clause 90, wherein the mobile device includes a cellular phone.

[0310] 92. The device according to clause 90, wherein the mobile device includes a pen or a stylus.

[0311] 93. The device according to clause 92, wherein the pen or the stylus includes a force sensor, a motion sensor, a spring, or a combination thereof.

[0312] 94. The device according to any one of clauses 67 to 93, further comprising a control system configured to: control the light source system to emit light; receive a signal from the ultrasonic receiver system corresponding to ultrasonic waves generated by a target object; identify one or more arterial blood signals from the ultrasonic receiver system corresponding to ultrasonic waves generated by blood in an artery of the target object; and estimate one or more cardiac characteristics at least in part based on the one or more arterial blood signals.

[0313] 95. The device according to any one of clauses 67 to 94, further comprising one or more optical waveguides.

[0314] 96. The device according to clause 95, wherein at least a portion of one of the one or more optical waveguides resides in a portion of the platen.

[0315] 97. A device, comprising: a platen; a light source component for providing light to a target object on an outer surface of the platen, the light source component including one or more laser diodes and a drive circuit, the one or more laser diodes including at least one multi-junction laser diode; and an ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to light from the light source component.

[0316] 98. The device according to clause 97, further comprising a noise reduction system including one or more noise reduction elements configured to at least partially decouple acoustic energy generated by the light source component, electrical energy generated by the light source component, light generated by the light source component, or a combination thereof from the ultrasonic receiver system.

[0317] 99. The device according to clause 98, wherein the noise reduction system includes one or more electromagnetic shielding transmission lines of the light source component.

[0318] 100. A method, comprising: controlling, by a control system, a light source system to emit light to a target object on an outer surface of a platen; receiving, by the control system, a signal corresponding to ultrasonic waves generated by the target object from an ultrasonic receiver system; identifying, by the control system, an arterial signal from the ultrasonic receiver system, the arterial signal corresponding to ultrasonic waves generated by blood in an artery of the target object, ultrasonic waves generated by one or more arterial walls of the target object, or a combination thereof; and estimating, by the control system, one or more cardiac characteristics based at least in part on the arterial blood signal.

[0319] 101. The method according to clause 100, wherein controlling the light source system to emit light includes controlling the light source system to emit laser pulses.

[0320] 102. A device, comprising: a platen; a light source system configured to provide light to a target object on an outer surface of the platen; and an ultrasonic receiver configured to receive ultrasonic waves generated by the target object in response to light from the light source system, wherein one or more platen characteristics including the thickness of the platen, the speed of sound of the platen, or a combination thereof are configured to separate one or more arterial ultrasonic waves generated by blood in an artery, arterial walls, or a combination thereof from one or more other types of received ultrasonic waves.

[0321] 103. The device according to clause 102, wherein the one or more other types of received ultrasonic waves include reflected ultrasonic waves that have been reflected from the target object by the ultrasonic receiver.

[0322] 104. The device according to clause 103, wherein the one or more platen characteristics cause the reflected ultrasonic waves emitted by the ultrasonic receiver to be received by the ultrasonic receiver after the one or more arterial ultrasonic waves.

[0323] 105. The device according to any one of clauses 102 to 104, wherein the speed of sound in the platen is in the range of 800 to 3000 meters per second.

[0324] 106. The device according to any one of clauses 102 to 105, wherein the thickness of the platen is in the range of 5 to 40 millimeters.

[0325] 107. The device according to any one of clauses 102 to 106, wherein the platen is configured to increase the intensity of the ultrasonic energy received by at least a portion of the ultrasonic receiver.

[0326] 108. The device according to any one of clauses 102 to 107, wherein the platen includes a sound waveguide.

[0327] 109. The device according to any one of clauses 102 to 108, wherein the platen includes a sound lens.

[0328] 110. The device according to clause 109, wherein the sound lens resides on the outer surface of the platen or is close to the outer surface of the platen.

[0329] 111. The device according to clause 109 or clause 110, wherein the sound lens includes a spherical lens or a cylindrical lens.

[0330] 112. The device according to any one of clauses 102 to 111, wherein the platen, the light source system, or a combination thereof is configured to transmit light from the light source system to the outer surface of the platen along a first axis or substantially along the first axis.

[0331] 113. The device according to clause 112, wherein the platen is configured to transmit ultrasonic waves generated by the target object along a second axis or substantially along the second axis, the second axis being different from the first axis.

[0332] 114. The device according to clause 112, wherein the platen is configured to transmit ultrasonic waves generated by the target object along a second axis or substantially along the second axis, the second axis being parallel to the first axis.

[0333] 115. The device according to any one of clauses 102 to 114 further includes a control system configured to: control the light source system to emit light; receive a signal corresponding to the ultrasonic waves generated by the target object from the ultrasonic receiver system; identify one or more arterial wall signals corresponding to the ultrasonic waves generated by one or more arterial walls of the target object from the ultrasonic receiver system; and estimate one or more cardiac characteristics based at least in part on the one or more arterial wall signals.

[0334] 116. The device according to any one of clauses 102 to 115, wherein the ultrasonic receiver includes two or more receiver elements adjacent to a region of the platen, and light from the light source is transmitted through the region of the platen towards the target object.

[0335] 117. The device according to any one of clauses 102 to 116, wherein the platen, the light source system, or a combination thereof is configured to transmit light in the near-infrared range.

[0336] 118. The device according to any one of clauses 102 to 117, wherein the device is a mobile device or includes a mobile device, and wherein an outer surface of the platen corresponds to or is close to an outer surface of the mobile device.

[0337] 119. The device according to clause 118, wherein the mobile device includes a cellular phone.

[0338] 120. The device according to clause 118, wherein the mobile device includes a pen or a stylus.

[0339] 121. The device according to clause 120, wherein the pen or the stylus includes a force sensor, a motion sensor, a spring, or a combination thereof.

[0340] 122. The device according to any one of clauses 102 to 121, wherein the platen provides an acoustic attenuation of ultrasonic waves in the range of 0.3 to 6.0 decibels per centimeter per megahertz.

[0341] 123. The device according to any one of clauses 102 to 122, wherein the ultrasonic waves received by the ultrasonic receiver are in the range of 0.5 megahertz to 1.5 megahertz, and wherein the platen provides an acoustic attenuation of ultrasonic waves in the range of 0.3 to 12.0 decibels per centimeter per megahertz.

[0342] 124. The device according to clause 123, wherein a portion of the platen residing between the outer surface and the ultrasonic receiver has a thickness in the range of 0.25 cm to 0.75 cm.

[0343] 125. The device according to any one of clauses 102 to 124, wherein the ultrasonic waves received by the ultrasonic receiver are in the range from 1.5 megahertz to 3.0 megahertz, and wherein the platen provides an acoustic attenuation of the ultrasonic waves in the range from 0.3 to 3.0 decibels per centimeter per megahertz.

[0344] 126. The device according to clause 125, wherein a portion of the platen residing between the outer surface and the ultrasonic receiver has a thickness in the range from 0.5 cm to 2.0 cm.

[0345] 127. The device according to any one of clauses 102 to 126, wherein the ultrasonic waves received by the ultrasonic receiver are in the range from 3.0 megahertz to 7.0 megahertz, and wherein the platen provides an acoustic attenuation of the ultrasonic waves in the range from 0.3 to 3 decibels per centimeter per megahertz.

[0346] 128. The device according to any one of clauses 102 to 127, wherein a portion of the platen residing between the outer surface and the ultrasonic receiver has a thickness in the range from 2.0 cm to 6.0 cm.

[0347] 129. The device according to any one of clauses 102 to 128, wherein the ultrasonic waves received by the ultrasonic receiver are in the range from 7.0 megahertz to 13.0 megahertz, and wherein the platen provides an acoustic attenuation of the ultrasonic waves less than 0.15 decibels per centimeter per megahertz.

[0348] 130. The device according to clause 129, wherein a portion of the platen residing between the outer surface and the ultrasonic receiver has a thickness in the range from 2.0 cm to 6.0 cm.

[0349] 131. The device according to any one of clauses 102 to 130, wherein the acoustic impedance of at least the outer surface of the platen is configured to be close to the acoustic impedance of human skin.

[0350] 132. The device according to any one of clauses 102 to 131, wherein at least the outer surface of the platen is configured to conform to the surface of human skin.

[0351] 133. The device according to any one of clauses 102 to 132, wherein at least one surface of the platen includes an anti-reflection layer.

[0352] 134. The device according to any one of clauses 102 to 133 further includes a control system configured to: control the light source system to emit light; receive a signal from the ultrasonic receiver corresponding to the ultrasonic waves generated by the target object; identify an arterial blood signal from the ultrasonic receiver corresponding to the ultrasonic waves generated by the blood in the artery of the target object; and estimate one or more cardiac characteristics at least partially based on the arterial blood signal.

[0353] 135. The device according to any one of clauses 102 to 134 further includes one or more optical waveguides.

[0354] 136. The device according to clause 135, wherein at least a portion of one of the one or more optical waveguides resides in a portion of the platen.

[0355] 137. A method includes: controlling, by a control system, a light source system to emit light toward a target object on an outer surface of a platen; receiving, by the control system, a signal from an ultrasonic receiver system corresponding to the ultrasonic waves generated by the target object; identifying, by the control system, an arterial signal from the ultrasonic receiver system that corresponds to the ultrasonic waves generated by the blood in the artery of the target object, the ultrasonic waves generated by one or more arterial walls of the target object, or a combination thereof; and estimating, by the control system, one or more cardiac characteristics at least partially based on the arterial blood signal.

[0356] 138. The method according to clause 137, wherein controlling the light source system to emit light includes controlling the light source system to emit laser pulses.

[0357] 139. A device includes: a platen; a light source component for providing light to a target object on an outer surface of the platen; and an ultrasonic receiver configured to receive ultrasonic waves generated by the target object in response to light from the light source component, wherein one or more platen characteristics including the thickness of the platen, the speed of sound of the platen, or a combination thereof are configured to separate one or more arterial ultrasonic waves received from the blood in the artery, from the arterial wall, or from a combination thereof from one or more other types of received ultrasonic waves.

[0358] 140. The device according to clause 139, wherein the one or more other types of received ultrasonic waves include reflected ultrasonic waves that have been reflected from the target object by the ultrasonic receiver.

[0359] 141. The device according to clause 140, wherein the one or more platen characteristics cause the reflected ultrasonic waves emitted by the ultrasonic receiver to be received by the ultrasonic receiver after the one or more arterial ultrasonic waves.

[0360] 142. A device, comprising: a platen having an outer surface, the acoustic impedance of the outer surface being configured to be close to the acoustic impedance of human skin, the outer surface being configured to conform to the surface of human skin; a light source system configured to provide light to a target object on or near the outer surface of the platen; and an ultrasonic receiver configured to receive ultrasonic waves generated by the target object in response to light from the light source system.

[0361] 143. The device according to clause 142, wherein the acoustic impedance of the outer surface is within a range of plus or minus 5% of the acoustic impedance of human skin.

[0362] 144. The device according to clause 142, wherein the acoustic impedance of the outer surface is within a range of plus or minus 10% of the acoustic impedance of human skin.

[0363] 145. The device according to any one of clauses 142 to 144, wherein the acoustic impedance of the outer surface is within a range of 1.4 to 1.7 megaraies.

[0364] 146. The device according to any one of clauses 142 to 145, wherein the outer surface is configured to conform to the ridges and valleys of a finger pad.

[0365] 147. The device according to any one of clauses 142 to 146, wherein the outer surface is configured to releasably adhere to the surface of human skin.

[0366] 148. The device according to any one of clauses 142 to 147, wherein the platen is configured to increase the intensity of ultrasonic energy received by at least a portion of the ultrasonic receiver.

[0367] 149. The device according to any one of clauses 142 to 148, wherein the platen includes an acoustic waveguide.

[0368] 150. The device according to any one of clauses 142 to 149, wherein the platen includes an acoustic lens.

[0369] 151. The device according to clause 150, wherein the acoustic lens resides on or near the outer surface of the platen.

[0370] 152. The device according to clause 150 or clause 151, wherein the acoustic lens includes a spherical lens or a cylindrical lens.

[0371] 153. The device according to any one of clauses 142 to 152, wherein the platen, the light source system, or a combination thereof is configured to transmit light from the light source system to the outer surface of the platen along a first axis or substantially along a first axis.

[0372] 154. The apparatus according to clause 153, wherein the platen is configured to transmit ultrasound generated by the target object along a second axis or substantially along the second axis, the second axis being different from the first axis.

[0373] 155. The apparatus according to clause 153, wherein the platen is configured to transmit ultrasound generated by the target object along a second axis or substantially along the second axis, the second axis being parallel to the first axis.

[0374] 156. The apparatus according to any one of clauses 142 to 155, further comprising a control system configured to: control the light source system to emit light; receive a signal from the ultrasound receiver system corresponding to the ultrasound generated by the target object; identify one or more arterial wall signals from the ultrasound receiver system corresponding to the ultrasound generated by one or more arterial walls of the target object; and estimate one or more cardiac characteristics at least in part based on the one or more arterial wall signals.

[0375] 157. The apparatus according to any one of clauses 142 to 156, wherein the ultrasound receiver comprises two or more receiver elements adjacent to a region of the platen, and light from the light source is transmitted through the region of the platen towards the target object.

[0376] 158. The apparatus according to any one of clauses 142 to 157, wherein the platen, the light source system, or a combination thereof is configured to transmit light in the near-infrared range.

[0377] 159. The apparatus according to any one of clauses 142 to 158, wherein the apparatus is a mobile device or includes a mobile device, and wherein an outer surface of the platen corresponds to or is close to an outer surface of the mobile device.

[0378] 160. The apparatus according to clause 159, wherein the mobile device includes a cellular phone.

[0379] 161. The apparatus according to clause 159, wherein the mobile device includes a pen or a stylus.

[0380] 162. The apparatus according to clause 161, wherein the pen or the stylus includes a force sensor, a motion sensor, a spring, or a combination thereof.

[0381] 163. The apparatus according to any one of clauses 142 to 162, wherein the thickness of the platen, the speed of sound of the platen, or a combination thereof is configured to separate ultrasound generated by blood in an artery from other ultrasound.

[0382] 164. The device according to any one of clauses 142 to 163, wherein the platen provides ultrasonic sound attenuation in the range of from 0.3 to 3.0 decibels per centimeter per megahertz.

[0383] 165. The device according to any one of clauses 142 to 164, wherein the speed of sound in the platen is in the range of from 800 to 3000 meters per second.

[0384] 166. The device according to any one of clauses 142 to 165, wherein at least one surface of the platen includes an antireflection layer.

[0385] 167. The device according to any one of clauses 142 to 166, further comprising a control system configured to: control the light source system to emit light; receive a signal from the ultrasonic receiver corresponding to the ultrasonic waves generated by the target object; identify an arterial blood signal from the ultrasonic receiver corresponding to the ultrasonic waves generated by the blood in the artery of the target object; and estimate one or more cardiac characteristics at least in part based on the blood arterial signal.

[0386] 168. The device according to any one of clauses 142 to 167, further comprising one or more optical waveguides.

[0387] 169. The device according to clause 168, wherein at least a portion of one of the one or more optical waveguides resides in a portion of the platen.

[0388] 170. A device comprising: a platen having an outer surface, the acoustic impedance of the outer surface being configured to be close to the acoustic impedance of human skin, the outer surface being configured to conform to the surface of human skin; a light source component for providing light to a target object on or close to the outer surface of the platen; and an ultrasonic receiver configured to receive ultrasonic waves generated by the target object in response to light from the light source component.

[0389] 171. The device according to clause 170, wherein the acoustic impedance of the outer surface is in the range of plus or minus 5% of the acoustic impedance of human skin.

[0390] 172. The device according to clause 170, wherein the acoustic impedance of the outer surface is in the range of plus or minus 10% of the acoustic impedance of human skin.

[0391] 173. A method includes: controlling, by a control system, a light source system to emit light toward a target object on an outer surface of a platen; receiving, by the control system, a signal from an ultrasonic receiver system corresponding to ultrasonic waves generated by the target object; identifying, by the control system, an arterial signal from the ultrasonic receiver system, the arterial signal corresponding to ultrasonic waves generated by blood in an artery of the target object, ultrasonic waves generated by one or more arterial walls of the target object, or a combination thereof; and estimating, by the control system, one or more cardiac characteristics based at least in part on the arterial blood signal.

[0392] 174. The method of clause 173, wherein controlling the light source system to emit light includes controlling the light source system to emit laser pulses.

[0393] As used herein, a phrase referring to "at least one" of a list of items means any combination of those items, including a single member. By way of example, "at least one of a, b, or c" is intended to cover: a, b, c, a - b, a - c, b - c, and a - b - c.

[0394] The various illustrative logical, logical block, module, circuit, and algorithmic processes described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. The interchangeability of hardware and software has been generally described in functional terms and illustrated in the various illustrative components, blocks, modules, circuits, and processes described above. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

[0395] The hardware and data processing apparatus for implementing the various illustrative logical, logical block, module, and circuit described in connection with the aspects disclosed herein may be implemented or performed with a general - purpose single - chip or multi - chip processor, a digital signal processor (DSP), an application - specific integrated circuit (ASIC), a field - programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general - purpose processor may be a microprocessor or any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some embodiments, particular processes and methods may be performed by circuitry specific to a given function.

[0396] In one or more aspects, the described functionality may be implemented in hardware, digital electronic circuitry, computer software, firmware (including the structures disclosed in this specification and structural equivalents thereof), or any combination thereof. Embodiments of the subject matter described in this specification may also be implemented as one or more computer programs, i.e., one or more modules of computer program instructions encoded on a computer storage medium for execution by, or to control the operation of, a data processing apparatus.

[0397] If implemented in software, the functionality may be stored on a computer-readable medium (such as a non-transitory medium) or transmitted as one or more instructions or code on a computer-readable medium (such as a non-transitory medium). The processes of the methods or algorithms disclosed herein may be implemented in a processor-executable software module that may reside on a computer-readable medium. Computer-readable media includes both computer storage media and communication media, including any medium that can be enabled to transfer a computer program from one place to another. The storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, non-transitory media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection may properly be termed a computer-readable medium. As used herein, disks and discs include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, where disks typically reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. Additionally, the operations of a method or algorithm may reside as code and instructions in or among one or any combination or set of machine-readable and computer-readable media, which may be incorporated into a computer program product.

[0398] Various modifications to the embodiments described in this disclosure will be apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the claims, principles, and novel features disclosed herein. The word "exemplary" is used herein, if at all, specifically to mean "serving as an example, instance, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

[0399] Certain features that are described in the context of separate embodiments in this specification can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented separately in multiple embodiments or in any suitable sub-combination. Additionally, although features may be described above as acting in certain combinations and even initially claimed as such, in some cases, one or more features from a claimed combination can be deleted from that combination, and the claimed combination can be directed to a sub-combination or a variant of a sub-combination.

[0400] Similarly, although operations are depicted in the figures in a particular order, this should not be construed as requiring that the operations be performed in the particular order shown or in a sequential order, or that all of the operations shown be performed, to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Additionally, the separation of the various system components in the above-described embodiments should not be construed as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Further, other embodiments are within the scope of the appended claims. In some cases, the acts recited in the claims can be performed in a different order and still achieve the desired result.

[0401] It will be understood that, unless features in any particular described embodiment are explicitly identified as being incompatible with each other, or the surrounding context implies that they are mutually exclusive and cannot readily be combined in a complementary and / or supportive sense, the entire disclosure contemplates and envisions that the specific features of these complementary embodiments can be selectively combined to provide one or more comprehensive but slightly different technical solutions. Accordingly, it will also be understood that the above description is given by way of example only, and that modifications in detail can be made within the scope of the disclosure.

[0402] Various modifications to the embodiments described in this disclosure will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the appended claims are not intended to be limited to the embodiments shown herein, but are to be accorded the widest scope consistent with the disclosure, the principles disclosed herein, and the novel features.

[0403] In addition, certain features that are described in the context of separate embodiments in this specification can also be implemented in combination in a single embodiment. Conversely, the various features that are described in the context of a single embodiment can also be implemented separately in multiple embodiments or in any suitable sub-combination. Further, although features may be described above as acting in certain combinations and even initially claimed as such, in some cases, one or more features from a claimed combination can be deleted from that combination, and the claimed combination can be directed to a sub-combination or a variant of a sub-combination.

[0404] Similarly, although operations are depicted in the drawings in a particular order, this should not be construed as requiring that such operations be performed in the particular order shown or in a sequential order, or that all of the illustrated operations be performed, to achieve a desired result. Additionally, the drawings may schematically depict yet another example process in the form of a flowchart. However, other operations not depicted can be incorporated into the example process that is schematically illustrated. For example, one or more additional operations can be performed before, after, concurrently with, or between any of the operations that are illustrated. Further, each of the operations that are described and illustrated can itself include and collectively refer to multiple sub-operations. For example, each of the operations described above can itself involve the execution of a process or algorithm. Additionally, in some embodiments, the various operations that are described and illustrated can be combined or performed in parallel. Similarly, the separation of the various system components in the embodiments described above should not be construed as requiring such separation in all embodiments. Accordingly, other embodiments are also within the scope of the appended claims. In some cases, the acts recited in the claims can be performed in a different order and still achieve a desired result.

Claims

1. A device, comprising: A platen; A light source system configured to provide light to a target object on an outer surface of the platen, the light source system including one or more laser diodes and a drive circuit, the one or more laser diodes including at least one multi-junction laser diode; And An ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to light from the light source system.

2. The device according to claim 1 further comprises: A noise reduction system including one or more noise reduction elements configured to at least partially decouple acoustic energy generated by the light source system, electrical energy generated by the light source system, light generated by the light source system, or a combination thereof from the ultrasonic receiver system.

3. The device according to claim 2, wherein The noise reduction system includes one or more electromagnetic shielding transmission lines of the light source system.

4. The device according to claim 3, wherein, The one or more electromagnetic shielding transmission lines are configured to reduce electromagnetic interference from the light source system received by the ultrasonic receiver system.

5. The device according to claim 2, wherein The noise reduction system includes one or more air gaps between the light source system and the ultrasonic receiver system.

6. The device according to claim 2, wherein The noise reduction system includes one or more sound-absorbing layers configured to reduce acoustic energy generated by the light source system and received by the ultrasonic receiver system.

7. The apparatus according to claim 6, wherein, At least one of the one or more sound-absorbing layers resides in or near the ultrasonic receiver system.

8. The apparatus according to claim 6, wherein, At least one of the one or more sound-absorbing layers resides in or near the light source system.

9. The device according to claim 2, wherein, The noise reduction system includes one or more light-absorbing layers configured to reduce the amount of light generated by the light source system and received by the ultrasonic receiver system.

10. The device according to claim 9, wherein, At least one of the one or more light-absorbing layers resides in or near the ultrasonic receiver system.

11. The device according to claim 2, wherein The noise reduction system includes one or more reflective layers configured to reduce the amount of light generated by the light source system and received by the ultrasonic receiver system.

12. The apparatus according to claim 11, wherein, At least one of the one or more reflective layers resides between the platen and at least a portion of the ultrasonic receiver system.

13. The device according to claim 1, wherein, The light source system includes a lens configured to collimate light generated by the light source system.

14. The device according to claim 1, wherein the platen, the light source system, or a combination thereof is configured to transmit light from the light source system to the outer surface of the platen along a first axis or substantially along the first axis.

15. The apparatus according to claim 14, wherein, The platen is configured to transmit ultrasonic waves generated by the target object along a second axis or substantially along the second axis, the second axis being different from the first axis.

16. The apparatus according to claim 14, wherein, The platen is configured to transmit ultrasonic waves generated by the target object along a second axis or substantially along the second axis, the second axis being parallel to the first axis.

17. The device according to claim 1, further comprising a control system configured to: Control the light source system to emit light; Receive a signal from the ultrasonic receiver system corresponding to the ultrasonic waves generated by the target object; Identifying one or more arterial wall signals corresponding to ultrasonic waves generated by one or more arterial walls of the target object from the ultrasonic receiver system; and Estimating one or more cardiac characteristics based at least in part on the one or more arterial wall signals.

18. The device according to claim 1, wherein, The ultrasonic receiver system includes two or more receiver elements adjacent to a region of the platen, and light from the light source system is transmitted through the region of the platen toward the target object.

19. The device according to claim 1, wherein The light source system is configured to transmit light in a wavelength range of 800 to 950 nanometers.

20. The apparatus according to claim 1, wherein The light source system is configured to transmit light in a wavelength range of 500 to 600 nanometers.

21. The apparatus according to claim 1, wherein the light source system includes one or more light emitting diodes, one or more vertical cavity surface emitting lasers, one or more edge emitting lasers, or a combination thereof.

22. The device according to claim 1, wherein, The drive circuit is configured to cause the light source system to emit light pulses having a pulse width in a range from 3 nanoseconds to 1000 nanoseconds.

23. The apparatus according to claim 1, wherein The drive circuit is configured to cause the light source system to emit light pulses at a pulse repetition frequency in a range from 1 kilohertz to 100 kilohertz.

24. The device according to claim 1, wherein The apparatus is a mobile device or includes a mobile device, and an outer surface of the platen corresponds to or is close to an outer surface of the mobile device.

25. The device according to claim 24, wherein The mobile device includes a cellular phone.

26. The apparatus according to claim 24, wherein, The mobile device includes a pen or a stylus.

27. The apparatus according to claim 26, wherein the pen or the stylus includes a force sensor, a motion sensor, a spring, or a combination thereof.

28. The apparatus according to claim 1, further comprising a control system configured to: Control the light source system to emit light; Receive signals corresponding to ultrasonic waves generated by a target object from the ultrasonic receiver system; Identify one or more arterial blood signals from the ultrasonic receiver system, the one or more arterial blood signals corresponding to ultrasonic waves generated by blood within an artery of the target object; and Estimate one or more cardiac characteristics based at least in part on the one or more arterial blood signals.

29. The apparatus according to claim 1, further comprising one or more optical waveguides.

30. The apparatus according to claim 29, wherein, At least a portion of one of the one or more optical waveguides resides in a portion of the platen.

31. An apparatus, comprising: A platen; A light source component for providing light to a target object on an outer surface of the platen, the light source component including one or more laser diodes and a drive circuit, the one or more laser diodes including at least one multi-junction laser diode; And An ultrasonic receiver system configured to receive ultrasonic waves generated by the target object in response to light from the light source component.

32. The apparatus according to claim 31, further comprising: A noise reduction system including one or more noise reduction elements configured to at least partially decouple acoustic energy generated by the light source component, electrical energy generated by the light source component, light generated by the light source component, or a combination thereof from the ultrasonic receiver system.

33. The apparatus according to claim 32, wherein, The noise reduction system includes one or more electromagnetic shielding transmission lines of the light source component.

34. A method, comprising: Control a light source system to emit light towards a target object on an outer surface of a platen by a control system; Receive, by the control system, a signal corresponding to ultrasonic waves generated by the target object from an ultrasonic receiver system; Identify, by the control system, an arterial signal from the ultrasonic receiver system, the arterial signal corresponding to ultrasonic waves generated by blood within an artery of the target object, ultrasonic waves generated by one or more arterial walls of the target object, or a combination thereof; And Estimate, by the control system, one or more cardiac characteristics based at least in part on the arterial blood signal.

35. The method according to claim 34, wherein controlling the light source system to emit light comprises controlling the light source system to emit laser pulses.

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