Housing-assisted self-mixing interferometry

Abstract

The present disclosure relates to an electronic device (400) including: a housing (440) including: a housing portion (442) defining an interior space of the housing (440), and a functional portion (446) monolithically formed with the housing portion (442) and configured to act as a mirror to cause reflection of light within the interior space of the housing (440); and a self-mixing interferometry sensor (410) disposed within the interior space of the housing (440) and including a light emitter (412) with a laser resonator cavity configured to emit laser light, wherein the functional portion (446) of the housing is configured to receive laser light emitted by the laser resonator cavity and to cause the received laser light to travel back towards the laser resonator cavity.

Description

HOUSING-ASSISTED SELF-MIXING INTERFEROMETRYTechnical Field

[0001] The present disclosure relates generally to an adapted housing for use in an electronic device, to an electronic device including the adapted housing, and to methods thereof (e.g., a method of forming an adapted housing, a method of providing an electronic device including the adapted housing).Background

[0002] In general, electronic devices used in everyday life, such as smartphones, tablets, wearable devices (e.g., smart watches, earbuds), house appliances (e.g., smart refrigerators, air conditioning systems, washing machines), laptops, etc. include various sensors to monitor the environment and implement certain functionalities. For example, the sensors allow detecting the actions of a user of the electronic device, and trigger a corresponding response based on what the user is doing. In this context, a relevant example are sensors based on self-mixing interferometry, which allow a fast, accurate, and sensitive detection of user’s gestures, e.g. for tracking applications, touch sensing, and the like. Improvements in sensor systems for electronic devices, and in particular in sensor systems based on self-mixing interferometry, may thus be of particular relevance for the further advancements of several applications.Brief Description of the Drawings

[0003] In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various aspects of the invention are described with reference to the following drawings, in which:FIG. l shows a self-mixing interferometry sensor, in a schematic representation according to various aspects;FIG.2A shows an earbud including a self-mixing interferometry sensor, in a schematic representation according to various aspects;FIG.2B and FIG.2C illustrate issues related to the integration of a self-mixing interferometry sensor in an electronic device, in a schematic representation according to various aspects;FIG.3A and FIG.3B show a housing adapted for use in an electronic device including a self-mixing interferometry sensor, in a schematic representation according to various aspects;FIG.4A and FIG.4B show an electronic device including the adapted housing and a self-mixing interferometry sensor, in a schematic representation according to various aspects;FIG.4C shows a detection of a touching even via the self-mixing interferometry sensor, in a schematic representation according to various aspects;FIG.5 A and FIG.5B show aspects of the configuration of the functional portion of the housing in relation to focal point and radius of curvature;FIG.6 shows a comparison between different configurations of a housing for use in combination with a self-mixing interferometry sensor, in a schematic representation according to various aspects;FIG.7 shows a schematic flow diagram of a method of providing a housing for use in an electronic device, according to various aspects; andFIG.8 shows a schematic flow diagram of a method of providing an electronic device, according to various aspects.Description

[0004] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and aspects in which the invention may be practiced. These aspects are described in sufficient detail to enable those skilled in the art to practice the invention. Other aspects may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the invention. The various aspects are not necessarily mutually exclusive, as some aspects may be combined with one or more other aspects to form new aspects. Various aspects are described in connection with methods and various aspects are described in connection with devices (e.g., a housing, an electronic device). However, it is understood that aspects described in connection with methods may similarly apply to the devices, and vice versa.

[0005] In general, self-mixing interferometry (SMI) is a sensing technique that has a wide range of applications, e.g. for ranging, odometry, particle sensing, displacement sensing, vibration sensing, among others. SMI offers high precision and enables both distance measurements and speed measurements with a relatively simple setup. Furthermore, the asymmetry of the signal of this type of interferometry makes it an ideal technique to detect also the direction of movement of a target. This is possible, among other conditions, when the coupling onto the laser emitter is high enough. SMI may also be referred to as selfmixing laser interferometry, or back-injection laser interferometry.

[0006] The principles of SMI are in general well known in the art. An abridged overview of the operation of a SMI sensor is provided in relation to FIG.l to introduce aspects relevant for the present disclosure. It is understood that the representation in FIG. l is schematic and simplified for the purpose of illustration, and a SMI sensor may have a different configuration with respect to the configuration shown, e.g. with additional or alternative components, with a different arrangement of the components, etc.

[0007] In brief, a SMI sensor 100 may include a light source 102 configured to emit a beam of light 104 (as electromagnetic wave) towards a target 106. The light 104 may hit the target 106 and at least part of the light may return back towards the SMI sensor 100 as return light 108 (e.g., reflected, back- scattered, diffused). At least part of the return light 108 may be injected into the light source 102 and cause a variation in a property of the emitted light 104. In general, the light source 102 may include a laser source, e.g. a laser diode, configured to emit laser light 104, and the self-mixing interference occurs within the laser resonator cavity. For example, the light source 102 may include a vertical-cavity surface-emitting laser (VCSEL). As other examples, the light source 102 may include a gas laser, a fiber laser, a solid-state laser, a quantum dot laser, and the like.

[0008] Considering a laser source, the self-mixing effect may be based on mixing the electromagnetic wave within a laser resonator cavity with another electromagnetic wave that has been emitted from the cavity and subsequently reintroduced into the cavity after external propagation (and back-reflection towards the SMI sensor). The external propagation may illustratively occur in an external cavity 112 formed by the optical propagation path of the laser light away from the resonator cavity and back to the resonator cavity. The external cavity 112 may be understood as an arm of an interferometer (with the other arm being the laser resonator cavity), so that changes in the length of the optical path in the external cavity cause corresponding variations of an operational parameter of the laser resonator cavity.Illustratively, a displacement or vibrations of the target 106 may change (increase or decrease) the length of the interferometer arm defined by the external cavity 112.

[0009] In a SMI sensor 100 the re-entered return light 108 injected into the laser resonator cavity mixes with resident light of the resonator cavity, so that the return light 108 causes a perturbation of the electromagnetic field within the laser resonator cavity. The perturbation of the electromagnetic field causes a corresponding (measurable) perturbation of one or more operational parameters of the laser resonator cavity. The laser becomes sensitive to the optical path travelled by the emitted (and back-reflected) laser beam 104, thus allowing to detect distance, speed, vibration, tilting, and direction of movement of a target 106 on which the emitted laser beam impinges.

[0010] The self-mixing interference may cause variation in operational parameters of the laser resonator cavity such as the gain of the laser, the optical power within the resonator cavity, or the frequency modulation of the emitted light. Variations in the optical power may be measured directly, e.g. via a photodetector 110, or indirectly, e.g. by monitoring a voltage at drive terminals of the laser resonator cavity. Considering the use of a photodetector 110, part of the light from the laser resonator cavity may be directed to the photodetector 110. For example, the laser resonator cavity may be partially transmitting at both ends of the cavity (illustratively, towards the target 106 and towards the photodetector 110), e.g. the cavity may include two partially transmitting mirrors defining the laser resonator cavity. As another example, the photodetector 110 may be disposed side-by-side with the laser resonator cavity (rather than behind it), and an optical system (e.g. including a beam splitter) may be used to direct part of the laser light from the laser resonator cavity towards the photodetector 110.

[0011] A SMI sensor 100 may be commonly employed as displacement sensor and / or vibration sensor (also referred to as vibrometer). A field of application of particular relevance for SMI sensors is constituted by their use in electronic devices, in which a SMI sensor 100 allows detecting an action by a user and interpret the action as a corresponding input or command for controlling a functionality of the electronic device. Illustratively, the SMI signal may be indicative of a gesture of the user or of a touch of the user, which may trigger a certain response from the electronic device. As another example, a SMI sensor 100 may allow detection of deformations or vibrations of the skin of a user, or vibrations caused by the voice of the user, and interpret such deformations or vibrations as a corresponding input or command from the user.

[0012] In general, a SMI sensor may be integrated in any suitable type of electronic device in which this type of detection may be desired. As an example, as shown in FIG.2A, a SMI sensor 200 may be of particular interest for integration in an earbud 250, because a SMI sensor 200 may match the power and performance requirements for this type of application. In this regard, FIG.2A shows an earbud 250 as an exemplary electronic device including a SMI sensor 200 integrated within a housing 220 of the earbud 250. As discussed in relation to FIG. l, the SMI sensor 200 may include a laser source 202 with a laser resonator cavity (e.g., a VCSEL) that emits laser light 204 towards the housing 220 (as target 206). The emitted laser light 204 may be directed via a lens 216 towards the interior surface of the housing 220, may hit the surface of the housing 220, and return to the SMI sensor 200 (as return light 208) where the returned light is injected into the laser resonator cavity.

[0013] The SMI sensor 200 may further include a photodetector 210 disposed side-by-side to the laser source 202 and configured to detect part of the laser light generated within the laser resonator cavity. The SMI sensor 200 may further include an analog-to-digital converter (ADC) 214 configured to convert analog properties of the laser light (e.g., as represented by an analog signal, such as a photocurrent, from the photodetector 210) into corresponding digital signal for further processing. The digital signal from the ADC 214 may thus indicate variations in the optical path travelled by the emitted laser light 204.

[0014] The digital signal from the ADC 210 may be delivered to a processing circuit (not shown), which may detect the occurrence of an event from variations in operational parameters of the laser, e.g. optical power, voltage, etc., as discussed in relation to FIG.l. In relation to an earbud 250, the signal from ADC 214 may indicate a touch 222 from a user. Illustratively, when the user applies pressure to the housing 220 a displacement is caused. The housing 220 is deformed (up to hundreds of microns) by the applied pressure with the fingers. The processing circuit may process the digital signal to recognize the application of pressure by the user and trigger a corresponding function of the earbud 250 or of another device communicatively coupled with the earbud 250, such as changing volume, changing a reproduction speed of an audio file, changing the audio file to be reproduced, and the like. Some background light 230 may pass through the housing 220 and be detected by the side- by-side photodetector 210.

[0015] Issues related to the use of a SMI sensor 200 in an earbud 250 (or in general in small electronic devices) are illustrated in FIG.2B and FIG.2C. As shown in FIG.2B, the divergence of the emitted laser light 204b in combination with the typical properties ofmaterials used for the housing 220 of electronic devices (e.g., typical plastics) cause an insufficient contrast if the SMI sensor 200b does not include a lens in the optical path between the laser source 202 and the housing 220, thus reducing the sensitivity of the SMI detection. Thus, in conventional configurations, as shown in FIG.2C (and in FIG.2A), the SMI sensor 200c may include a lens 216 added at the output of the laser source 202, to focus or collimate the emitted laser light 204c onto the housing 220, thus enhancing the contrast and making the SMI detection possible.

[0016] However, the presence of a lens 216 causes increased costs for the fabrication of the SMI sensor 200, 200c and further increases the overall height of the SMI sensor 200, 200c because to achieve a reasonable optical design for the given tolerances, the distance from laser cavity to optics 216 has to increase. In view of the constant trend towards miniaturization of electronic devices (e.g., earbuds), the increased dimensions of the SMI sensor 200 due to the presence of the lens 216 represent a significant drawback that may limit the applicability and the adoption of this sensing technique.

[0017] Illustratively, in a conventional configuration a SMI system may require a lens to have enough signal to noise ratio (SNR) to make the system usable. The placement of optics on these systems is challenging because it adds costs, and the required low z-height makes the tolerances not compatible with cheap manufacturing practices and may require active alignment.

[0018] The present disclosure may be based on the realization that rather than relying on a lens or other discrete optical elements to enhance the contrast of SMI detection, the housing of the electronic device may be adapted to embed an optical function in the housing itself. Illustratively, the present disclosure may be based on the realization that at least part of the housing may be dedicated to a functional portion integrally formed (e.g., integrally molded) with the rest of the housing, and the functional portion may be configured to implement an optical function to ensure an enhanced return (e.g., back-reflection) of the laser light towards the resonator cavity of the SMI sensor, thus enabling SMI sensing with high SNR even in absence of a lens. By way of illustration, the functional portion of the housing may act as a mirror-like portion to ensure that sufficient return light reaches the laser resonator cavity to provide a measurable variation in operational parameters of the laser.

[0019] The configuration described herein allows thus obtaining a high SNR (e.g., a high contrast) for SMI sensing while removing the need for an additional lens, thus reducing the overall costs for the SMI sensor and electronic device. In a preferred configuration, thefunctional portion of the housing may be formed in the same molding process used for shaping the housing itself, so that the functional portion may be provided without introducing additional fabrication processes or costs, but rather by a cost- and resourceefficient adaptation of already used processes. Furthermore, the absence of the lens allows reducing the overall dimensions (in particular the z-height) of the SMI sensor, thus facilitating its integration in electronic devices with small dimensions.

[0020] According to various aspects, a housing for use in an electronic device including a self-mixing interferometry sensor may be provided, the housing including: a housing portion defining an interior space of the housing; and a functional portion monolithically formed (e.g., monolithically molded) with the housing portion, wherein the functional portion is configured to act as a mirror to cause reflection of light within the interior space of the housing.

[0021] Further aspects of the present disclosure are related to an electronic device in which the housing encloses circuitry (and other components) of the electronic device, and in which the functional portion is coupled with a SMI sensor and is configured to act as mirror-like surface for providing a reflection of the laser light emitted by the SMI sensor back towards the SMI sensor.

[0022] In particular, the strategy proposed herein may be of particular relevance for use in small wearable electronic devices, e.g. earbuds (e.g., wireless earbuds), so that in the following various aspects may be described with concepts and terminology that pertain to such technical field. It is however understood that the adapted housing described herein may be provided also in other types of electronic devices, e.g. for consumer, industrial, home, or automotive market. Other exemplary electronic devices including a housing adapted as proposed herein may include domestic cleaners, white goods (e.g. refrigerators, washing machines, and the like), air purifiers, industrial machines, consumer devices, etc.

[0023] According to various aspects an electronic device may include: a housing including: a housing portion defining an interior space of the housing; and a functional portion monolithically formed with the housing portion and configured to act as a mirror to cause reflection of light within the interior space of the housing; and a self-mixing interferometry sensor disposed within the interior space of the housing and including a light emitter with a laser resonator cavity configured to emit laser light, wherein the functional portion of the housing is configured to receive laser light emitted by the laser resonator cavity and to cause (at least part of) the received laser light to travel back towards the laser resonator cavity.

[0024] Aspects of the present disclosure may thus be based on combining the use of a SMI sensor, without any lens, and the (molded) case of the electronic device (e.g., of the earbuds) that has encoded an optical function. In the proposed configuration there is no need to integrate a lens at short distances, which would otherwise make it difficult to fulfill some optical requirements of the beam. The proposed configuration may thus be understood as a housing-assisted (or case-assisted) SMI sensor capable of lens-less operation. The adapted housing may thus allow obtaining a flatter SMI sensor.

[0025] Furthermore, in a configuration in which the SMI sensor includes a photodetector (e.g., a photodiode) placed side-by-side with respect to the light emitter (e.g., a VCSEL), the optical function encoded in the housing reduces the background light level impinging onto the photodetector, improving the dynamic range of the SMI sensor.

[0026] Various options are described to configure the functional portion. As a first example, the functional portion may be shaped in a concave manner (to obtain the optical function) such that higher contrast for the SMI detection may be achieved at a low price and while keeping the small z-height (increasing the light emitter-to-“mirror” distance effectively). As an exemplary configuration, the proposed approach may be realized by molding (part of) the plastic of an earbud (host system) in a concave way (e.g., with a parabolic shape). As the system parts are molded, the change in the mold shape does not incur onto additional cost for the system, so that the “external reflector” may be provided at higher distance (case) and molded without cost adder. Considering a housing made of molded plastic, the reflectivity of the plastic is well molded and has still some direct reflective part (mirror-like) on top of the diffusive part (Lambertian-like) of its reflectivity function.

[0027] In the proposed configuration, the height is intrinsically higher (up to the housing, e.g. up to the plastic case) so that the optics is more tolerant. As an extra beneficial aspect, the functional portion may cause the housing to be slightly thicker, so that less background light leaks through to the module. The proposed system may thus achieve high contrast for SMI detection, while maintaining an overall low price, low z-height, and ensuring a lower impact of background light.

[0028] In other aspects, additionally or alternatively to the parabolic / concave shape, the functional portion may include a high reflective coating (e.g., made of metal) that is deposited selectively in correspondence of the functional portion of the housing. For example, the coating may be formed directly by three-dimensional (3D) laser structuring (e.g., laser direct structuring, LDS, 3D-MID structuring, and the like), in the same step asother connections potentially needed on the system. The coating may further enhance the reflection of light towards the SMI sensor, thus providing increased contrast and SNR for the SMI measurement.

[0029] FIG.3A and FIG.3B show a housing 300 adapted for use in an electronic device including a self-mixing interferometry sensor, in a schematic representation according to various aspects. In particular FIG.3A and FIG.3B illustrate possible configurations 300a, 300b of the housing 300, which are collectively referred to as housing 300. A “housing” (e.g., the housing 300) for an electronic device may also be referred to herein as case, casing, or encasement.

[0030] In general, the housing 300 may be configured to host components of the electronic device, e.g. circuitry, mechanical components, optical components, etc. depending on the type of electronic device. The housing 300 may thus protect the components of the electronic device, e.g. from moisture, chemical agents, mechanical shocks, and the like. In this regard, the housing 300 may have any suitable dimensions and any suitable shape depending on the intended use, e.g. depending on the type of electronic device and its end application.

[0031] The housing 300 may in general include a housing portion 302 defining an interior space 304 of the housing 300. The housing portion 302 may illustratively be configured to enclose a space 304 in which the components of the electronic device may be disposed. Stated in a different fashion, the housing portion 302 may form an encased space 304 for hosting components of the electronic device. The interior space 304 may also be referred to herein as inner space, interior volume, inner volume, interior chamber, or inner chamber.

[0032] The housing portion 302 may include a plurality of housing walls. In the exemplary configuration in FIG.3A and FIG.3B the housing portion 302 may include four housing walls 322, 324, 326, 328, but it is understood that the housing portion 302 may include any suitable number of housing walls depending on the intended shape and dimensions of the housing 300, e.g. three, four, five, six, etc. The housing walls 322, 324, 326, 328 may illustratively be the sidewalls of the interior space 304. Although not shown, the housing walls 322, 324, 326, 328 may include coupling elements for mechanically coupling (e.g., fixing) the components of the electronic device to the housing walls 322, 324, 326, 328.

[0033] In the exemplary configuration in FIG.3A and FIG.3B the housing portion 302 may be a single monolithic piece. Illustratively, the housing walls 322, 324, 326, 328 may be monolithically formed and may constitute a single integral housing surrounding the interiorspace 304. In other aspects, the housing portion 302 may include a plurality of separate portions assembled together. For example, the housing portion 302 may include a top portion and a bottom portion formed separately and assembled together to form the housing portion 302. As another example, the housing portion 302 may include a left portion and a right portion formed separately and assembled together to form the housing portion 302.

[0034] Further, in the exemplary configuration in FIG.3A and FIG.3B the housing portion 302 is shown as defining an interior space 304 closed at all sides (e.g., at the four housing walls 322, 324, 326, 328). A configuration with a closed space 304 may provide enhanced protection of the components of the electronic device. It is however understood that the housing portion 302 may also define an interior space 304 that has an aperture on at least one side or on more than one side, e.g. at least one of the housing walls may include an opening or a plurality of openings.

[0035] As mentioned, the housing 300 (e.g., the housing portion 302) may have any suitable shape depending on the electronic device for which the housing 300 should be used. In a preferred configuration, the housing 300 may have a shape configured to at least partially conform to a body part of the human body, e.g. for use in a wearable electronic device. As a preferred example, the housing 300 may have a shape such that at least part of the housing 300 may fit in a human ear, e.g. to use the housing 300 for an earbud. Illustratively, at least part of the housing 300 may be configured to be placed in the ear of a user of the electronic device.

[0036] It is however understood that the housing 300 may have any other suitable shape, e.g. for fitting around the wrist of the user in case of a smart watch, for fitting around the head of the user in case of a headband, and the like. In general, the housing 300 may have a parallelepiped shape or any other suitable shape, e.g. spherical, cylindrical, trapezoidal, pyramidal, and the like.

[0037] In a corresponding manner, the housing 300 (e.g., the housing portion 302) may have any suitable dimensions depending on the electronic device for which the housing 300 should be used. In general, the proposed strategy for coupling with a SMI sensor may be of particular relevance for small portable electronic devices, e.g. wearable electronic devices. Thus, the dimensions of the housing may be in the centimeter range. For example, a housing wall 322, 324, 326, 328 may have a lateral dimension (e.g., a width, a length, a height) in the range from 0.1 cm to 10 cm, for example in the range from 0.5 cm to 5 cm, for example in the range from 1 cm to 2 cm. As another numerical example, the interior space 304 definedby the housing portion 302 may have a volume in the range from 0.1 cm3(cubic centimeters) to 500 cm3, for example a volume in the range from 0.5 cm3to 100 cm3, for example a volume in the range from 1 cm3to 50 cm3.

[0038] According to various aspects, the housing 300 may further include a functional portion 306 for coupling with a SMI sensor of the electronic device. The functional portion 306 may be monolithically formed with the housing portion 302 (e.g., with a housing wall) and may be configured to act as a mirror-like surface. Illustratively, the functional portion 306 may be configured to act as a mirror to cause back-propagation of light within the interior space 304 of the housing. Stated in a different fashion, the functional portion 306 may be configured such that in case the functional portion 306 receives light coming from a certain direction, the functional portion 306 causes a back-propagation of at least part of the received light along that direction.

[0039] In general, considering a “bare” surface with no additional coating, the functional portion 306 may cause light that impinges onto the functional portion 306 to return back towards the interior space 304 of the housing 300 via a combination of Lambertian reflection and direct reflection. Illustratively, considering typical materials for a housing 300 (discussed below in further detail), a “bare” surface of the functional portion 306 in combination with a suitable shape of the functional portion 306 (discussed below in further detail) provides Lambertian reflection and direct reflection of incident light.

[0040] It is understood that a housing 300 may include more than one functional portion 306, e.g. a housing 300 may include a plurality of functional portions 306 each monolithically formed with the housing portion 302. For example, a plurality of functional portions 306 may be provided in case the electronic device includes a plurality of SMI sensors.

[0041] As mentioned, the functional portion 306 may be monolithically formed with the housing portion 302. Illustratively, the functional portion 306 may form an integral piece with the housing portion 302 (e.g., with a housing wall 322). The functional portion 306 may thus be fabricated together with the housing portion 302, thus providing a time- and resource-efficient fabrication process. In a preferred configuration, the housing 300 may be an injection molded housing, and the functional portion 306 may be monolithically molded with the housing portion 302 (thus forming a single molded piece).

[0042] There may be various configurations for obtaining a “mirror-acting” portion of the housing 300. As a first example, as shown in FIG.3A, the functional portion 306a may havea concave shape. Illustratively, the functional portion 306a may have a curved surface with a concave shape, e.g. the functional portion 306a may be shaped as a concave mirror with the concave mirror surface facing towards the inner space 304 of the housing 300. The functional portion 306a may for example be shaped as a plano-concave mirror having a planar surface at the side where the functional portion 306a is integrally formed with the housing portion 302, and a concave surface at the side facing the inner space 304.

[0043] A concave functional portion 306a may have any suitable shape for the concave part. As a preferred configuration, which has been found to provide enhanced coupling without excessively pushing fabrication tolerances, the concave functional portion 306a may have a parabolic shape. It is however understood that other shapes for the concave part may be provided, such as a spherical shape or a hyperbolic shape.

[0044] In this configuration, the functional portion 306a may illustratively act as a dome that collects light (emitted by the SMI sensor) and provides reflection or collimation of light back towards the interior space 304 of the housing 300 (e.g., towards the SMI sensor). In this configuration, the functional portion 306a may thus protrude from the housing wall 322 towards the interior of the housing 300, and a border region of the functional portion 306a may be thicker than a center region 308a of the functional portion 306a.

[0045] The concave shape of the functional portion 306a may be adapted according to the overall dimensions of the housing 300 (and corresponding electronic device). In a preferred configuration, considering fabrication tolerances for a small sized electronic device, the concave functional portion 306a may have a radius of curvature with an absolute value in the range from 0.5 mm to 5 mm, for example in the range from 0.75 mm to 2 mm, for example an absolute value of about 1 mm. In a corresponding manner, a lateral dimension of the concave region 308a may be adapted according to the overall dimensions of the housing 300. As a numerical example, the concave region of the functional portion 306a may have a lateral dimension (e.g., a diameter) at its maximum aperture in the range from 0.5 cm to 5 cm, for example in the range from 1 cm to 2 cm.

[0046] It is understood that a concave shape may be particularly suitable to implement the enhanced contrast for SMI detection described herein, but in principle the functional portion 306a may also have other shapes capable of providing collection and reflection / collimation of incoming light back towards the direction from which the light originated.

[0047] According to various aspects, in addition or in alternative to shaping the functional portion 306 (e.g., as concave mirror) a surface treatment or coating may be provided to(further) enhance the reflection of light towards the interior of the housing 300 by the functional portion 306. As an example, the surface of the functional portion 306 facing towards the interior of the housing 300 (e.g., the surface facing towards a SMI sensor) may have a surface treatment configured to increase a reflectivity of the functional portion 306. Illustratively, the surface treatment may increase the reflectivity in a wavelength range of interest, e.g. the operating range of the SMI sensor. The surface treatment may thus cause the functional portion 306 to have greater reflectivity compared to an untreated portion of the housing 300, e.g. with respect to parts of the housing portion 302 without the surface treatment.

[0048] For example, the surface treatment may reduce a surface roughness of the functional portion 306 compared to an untreated portion of the housing 300. In this configuration, the functional portion 306 may have a surface roughness less than the surface roughness of other parts of the housing portion 302, e.g. of another part of the housing 300 facing the interior space 304.

[0049] According to various aspects, as shown in FIG.3B, in addition or in alternative to shaping the functional portion 306 (e.g., as concave mirror), the functional portion 306b may include a reflective coating 310b. The reflective coating 310b may be configured to be reflective for light in a wavelength range of interest, e.g. the wavelength range of emission of a light emitter of the SMI sensor. Considering a concave shape for the functional portion 306, the reflective coating 310b may be disposed to cover, fully or at least in part, the concave region of the functional portion 306. The reflective coating 310b may illustratively be a reflective layer disposed / formed in correspondence of the functional portion 306b. In a preferred configuration, the functional portion 306 may include both a concave shape (e.g., a parabolic shape) and a reflective coating disposed on the concave region, thus providing reflection as close as possible to a specular reflection to enhance the SMI detection.

[0050] The reflective coating 310b may include or may be made of any suitable material capable of providing reflection of (laser) light in the desired wavelength range. As an exemplary configuration, which may be provided with a simple, yet efficient fabrication process, the reflective coating 310b may include or may be made of a metal material (e.g., silver, gold, aluminum, etc.). For example, the reflective coating 310b may include a metal powder. It is understood that the reflective coating 310b may also include a plurality of layers, e.g. a plurality of metal layers, in which the refractive index of the individual layers is selected to enhance a combined reflection by the plurality of layers. It is also understoodthat other types of materials may be used for the reflective coating 310b, e.g. an oxide-based material or a nitride-based material as other examples.

[0051] In general, the housing 300 (e.g., the housing portion 302 and the monolithically formed functional portion 306) may include any suitable material. For example, the housing 300 may include or may be made of any suitable material that allows fabrication via injection molding. As an example, the housing 300 may include or may be made of a plastic material, e.g. acrylonitrile butadiene styrene (ABS), polycarbonate (PC), a blend of PC and ABS, polyphenylene ether (PPE), polybutadiene terephthalate (PBT), and the like. As another example, the housing 300 may include or may be made of a polymer material, such as liquid crystal polymer. In some aspects, the material of the housing 300 may be at least partially reflective for light in a wavelength range of interest, e.g. the material of the housing 300 may be configured to provide Lambertian and direct reflection of at least part of light incident on the housing 300 (e.g., on the functional portion 306). In case a reflective coating 310b is used, there is in principle no need for the material of the housing 300 to have reflective properties for light in the wavelength range of interest.

[0052] In general, the coupling with a SMI sensor may be the most relevant use case for the housing 300 configured as described herein. It is however understood that, in principle, the housing 300 may be suitable for use in combination with other types of light-based sensors within an electronic device.

[0053] FIG.4A and FIG.4B show an electronic device 400 including a housing 440 and a SMI sensor 410, in a schematic representation according to various aspects. In particular FIG.4A and FIG.4B illustrate possible configurations 400a, 400b of the electronic device 400, which are collectively referred to as electronic device 400. As mentioned, the electronic device 400 may be any suitable type of electronic device. In a preferred configuration, the electronic device 400 may be a wearable electronic device, e.g. an earbud (for example a wireless earbud), as shown in FIG.4C. In other aspects, the electronic device 400 may be a watch, a tablet, a smartphone, a home appliance, etc.

[0054] In general, the electronic device 400 may include a housing 440 and a SMI sensor 410 disposed within the interior space defined by the housing 440. In the simplified representation in FIG.4A and FIG.4B only a portion of the housing 440 is shown, to better illustrate the relationship between the functional portion of the housing 440 and the SMI sensor 410. It is however understood that the housing 440 may have any configuration discussed for the housing 300 in FIG.3A and FIG.3B, e.g. any suitable number of housingwalls, a closed or partially open interior space, any suitable shape or dimensions, etc. In general, the housing 440 may be an adapted housing configured as the housing 300 and may include a housing portion 442 defining an interior space, and a functional portion 446 for enhancing SMI detection.

[0055] It is also understood that the electronic device 400 may include any suitable component in addition to the SMI sensor 410. Illustratively, the electronic device 400 may include any suitable circuitry, mechanical components, optical components, etc. disposed within the interior space defined by the housing 440, depending on the intended application of the electronic device.

[0056] The SMI sensor 410 may in general be configured as the SMI sensor 100 described in relation to FIG.l. For example, the SMI sensor 410 may include a light emitter 412 with a laser resonator cavity configured to emit laser light 424. According to the configuration proposed herein, the functional portion 446 of the housing 440 may be configured to receive the laser light 424 emitted by the light emitter 412 (from the laser resonator cavity) and to cause at least part of the received laser light 424 to travel (in other words, propagate) back towards the SMI sensor 410 (towards the laser resonator cavity). Illustratively, the functional portion 446 may be configured to reflect the received laser light 424 back towards the SMI sensor 410 (as return light). In particular, FIG.4A shows a configuration of a functional portion 446a having a concave region 448a (e.g., a parabolic region), and FIG.4B shows a configuration of a functional portion 446b including a reflective coating 450b (e.g., in addition to the concave shape for the functional portion).

[0057] In general, the light emitter 412 may be or include any suitable laser source. In a preferred configuration, the light emitter 412 may be or include a VCSEL. It is however understood that other types of laser sources may be provided, as discussed in relation to FIG. l. The light emitter 412 (e.g., the laser resonator cavity) may be configured to emit light 424 in any suitable wavelength range. In a preferred configuration, the light emitter 412 may be configured to emit light 424 with wavelength in the infrared range (e.g., in the range from about 800 nm to about 5000 nm, for example in the range from about 820 nm to about 1200 nm), which is a relevant wavelength range for user applications because the emitted light is not visible to the human eye, and thus it does not cause any unpleasant effect for the user. It is however understood that in principle the light emitter 412 may be configured to emit light 424 in other wavelength ranges, e.g. the visible range (e.g., from about 380 nm to about 800 nm) and / or ultraviolet range (e.g., from about 100 nm to about 400 nm).

[0058] According to various aspects, the light emitter 412 and the functional portion 446 may be spatially disposed with respect to one another so as to maximize the contrast for the SMI detection. In general, the functional portion 446 may be in spatial correspondence with the emission of light 424 by the light emitter 412. For example, the light emitter 412 may be aligned with the (geometrical) center of the functional portion 446. As an example, in case of a VCSEL, the center of the functional portion 446 may be aligned with the top mirror of the VCSEL (illustratively, an imaginary line from the center of the top mirror of the VCSEL to the center of the functional portion 446 may be perpendicular to the surface of the top mirror of the VCSEL). According to various aspects, the light emitter 412 and the functional portion 446 may be spatially disposed with respect to one another such that the light emitter 412 emits light 424 along an emission direction that is substantially parallel to an axis of symmetry (illustratively, the “optical axis”) of the functional portion 446.

[0059] As mentioned above, the presence of the functional portion 446 allows a simpler and thinner arrangement for the SMI sensor 410. In particular, the presence of the functional portion 446 may enable SMI detection without a lens or other type of focusing / collimating element, so that in some aspects the SMI sensor 410 may be free of a lens (or in general free of an optical element for focusing or collimating the emitted light) in the optical path between the light emitter 412 and the functional portion 446. Furthermore in the configuration described herein a longer distance may be provided between the SMI sensor 410 and the “optics” (illustratively the functional portion 446), thus relaxing the tolerance requirements. As a numerical example, a distance between the light emitter 412 and a center of the functional portion 446 may be in the range from 200 pm to 2 mm, for example in the range from 500 pm to 1 mm.

[0060] In the proposed configuration, the contrast of the SMI detection may thus be enhanced by the functional portion 446 causing return light to travel back to the SMI sensor 410. The functional portion 446 and the light emitter 412 may be configured (e.g., spatially disposed) such that the return light from the functional portion 446 enters the laser resonator cavity, thus causing interference with the light resident in the cavity, and altering one or more operational parameters of the laser, as discussed in relation to FIG.l. In this regard, the electronic device 400 may further include a processing circuit 402 configured to identify a variation of one or more operational parameters of the laser resonator cavity caused by the interference of the laser light generated in the cavity with the laser light returned to the laser resonator cavity by the functional portion 446.

[0061] In general, the processing circuit 402 may be configured to receive a detection signal from the SMI sensor 410, and the detection signal may be representative of the one or more operational parameters of the laser resonator cavity. For example, the processing circuit 402 may be part of the SMI sensor 410, e.g. the processing circuit 402 may be part of the same integrated circuit (on the same substrate 418) as the other components of the SMI sensor 410 (e.g., the light emitter 412, a photodetector 414, etc.). In other aspects, the processing circuit 402 may be external to the SMI sensor 410. For example, the processing circuit 402 may be part of a central processing circuit of the electronic device 400, and the central processing circuit may carry out a principal function for the operation of the electronic device 400 and further signal processing for SMI detection.

[0062] By way of illustration, the processing circuit 402 may be configured to monitor over time the one or more operational parameters of the laser resonator cavity and determine whether a variation occurs and a magnitude of such variation. As mentioned in relation to FIG. l, the variation in the operational parameters may correspond to a certain event occurring in the “external cavity” of the SMI sensor 410. Any suitable operational parameter of the laser may be considered. As relevant examples, the one or more operational parameters of the laser resonator cavity may include an amplitude modulation of the laser light, a frequency modulation of the laser light, an optical power of the laser light (e.g., a gain of the laser), a voltage at drive terminals of the laser resonator cavity, or combinations thereof.

[0063] Accordingly, the detection signal received by the processing circuit 402 may be representative of the amplitude of the laser light, of the frequency of the laser light, of the optical power of the laser light, of the voltage at the drive terminals, or of any combination of such parameters. For example, for generating a detection signal representing the voltage, the SMI sensor 410 may include a voltage sensor coupled with the drive terminals and configured to provide a voltage detection signal representative of the voltage at the drive terminals (e.g., at the anode / cathode of a VCSEL).

[0064] As another example, for generating a detection signal representative of the laser light within the laser resonator cavity the SMI sensor 410 may include a photodetector 414 configured to detect part of the laser light generated in the laser resonator cavity and to provide a (light) detection signal representative of the laser light generated in the cavity. The photodetector 414 may have any suitable configuration, e.g. the photodetector 414 may be or include a photodiode (or a plurality of photodiodes), such as a pin photodiode, an avalanchephotodiode, a single-photon avalanche photo diode, a photodiode configured according to Charged Coupled Device (CCD) technology, a photodiode configured according to Complementary-Metal-Oxide-Semiconductor (CMOS) technology, and the like.

[0065] In general, the photodetector 414 may be configured to be sensitive for light in the wavelength range of the laser light generated by the laser cavity, and may be configured to generate a signal (e.g., a current, or a voltage) representing the light impinging onto the photodetector 414. In some aspects, the photodetector 414 may include one or more optical filters configured to block light with wavelength outside of the wavelength range of interest, e.g. outside of the wavelength range of the emission of the light emitter 412.

[0066] In some aspects, the processing circuit 402 may receive the detection signal directly from the photodetector 414 and / or voltage sensor. In other aspects, the SMI sensor 410 may further include an anal og-to-digi tai converter 416 configured to convert an analog detection signal from the photodetector 414 and / or voltage sensor into a digital detection signal, and deliver the digital detection signal to the processing circuit 402. It is understood that the analog-to-digital converter 416 may be absent from the SMI sensor 410 in some configurations, e.g. in case the processing circuit is configured to carry out analog processing, or in case an analog-to-digital converter is available externally to the SMI sensor 410.

[0067] Various configurations may be possible for positioning the photodetector 414. As an example, as shown in FIG.4A and FIG.4B the photodetector 414 may be disposed at a side of the light emitter 412, e.g. side-by-side to the laser resonator cavity. In this scenario, the SMI sensor 410 may include an optical component configured to direct part of the laser light 424 to the photodetector 414. For example, the SMI sensor 410 may include a beam splitter configured to let a first portion (e.g., more than 50%, for example more than 75%, for example more than 90%) of the laser light 424 pass through and propagate towards the functional portion 446, and to deviate a second portion of the laser light 424 (e.g., a fraction complementary to the first portion) towards the photodetector 414. A configuration with a side-by-side photodetector 414 may allow a reduction of the z-dimension of the SMI sensor 410.

[0068] In other aspects, the photodetector 414 may be aligned with the laser resonator cavity. For example, the photodetector 414 may be disposed at the bottom of the light emitter 412 considering a top emission towards the functional portion 446. Considering a VCSEL, the photodetector 414 may be disposed (e.g., integrated) in correspondence with thebottom mirror of the VCSEL, and the bottom mirror of the VCSEL may be configured to allow a portion of the laser light to pass through towards the photodetector 414.

[0069] As mentioned, the processing circuit 402 may be configured to receive the detection signal, determine the occurrence of a variation in one or more operational parameters of the laser resonator cavity, and associate the variation in the operational parameters to a corresponding event. In principle, the proposed configuration may be for use with a SMI sensor 410 used for any suitable application, such as force sensing, touch button, pressure sensing, deformation sensing, through-device sound conduction sensing, vibration sensing, and the like.

[0070] In a preferred configuration, the processing circuit 402 may be configured to associate the variation in the operational parameters to a touching event on the housing 440. This scenario is illustrated in FIG.4C, which shows an earbud 460 as exemplary electronic device 400, and a touch 462 by a user on the housing 440 of the earbud 460, e.g. a “tapping” with a finger on the housing 440. The exemplary configuration in FIG.4C shows a functional portion 446 without reflective coating 450b, but it is understood that the aspects discussed in relation to FIG.4C apply in a corresponding manner to a configuration in which the functional portion 446 includes a reflective coating 450b.

[0071] The processing circuit 402 may be configured to identify the occurrence of a touching event 462 on the housing 440 based on the variation of the one or more operational parameters. As shown, a touching by a finger of a user causes a displacement of the housing 440 (illustratively, a compression), thus causing a corresponding variation in the optical length of the “interferometer arm” external to the SMI sensor 410. A variation in the operational parameters may thus be indicative of a touch 462 by a user that is tapping on the housing 440 (e.g., in correspondence of the functional portion 446).

[0072] In some aspects, the processing circuit 402 may be configured to determine (e.g., identify, estimate) one or more properties of the touching event 462 based on the variation of the one or more operational parameters. For example, the processing circuit 402 may be configured to determine a force of the touching event 462, a speed of the touching event 462 and / or a direction of the touching event 462 (e.g., a sliding of the finger on the housing 440).

[0073] It is understood that the processing circuit 402 may be adapted to identify other types of events and / or properties based on the variation of the one or more operational parameters, depending on the intended use of the SMI sensor 410 and electronic device 400.

[0074] According to various aspects, the processing circuit 402 may be further configured to trigger a function of the electronic device 400 based on the result of the SMI detection, e.g. upon detecting a touching event 462 (and / or based on the properties of the touching event 462). Illustratively, the event detection may cause the processing circuit 402 to cause a corresponding response by the electronic device 400. For example, the processing circuit 402 may transmit an instruction to a central processing circuit of the electronic device 400 indicating the occurred touching event and prompting a corresponding action. As another example, the processing circuit 402 may transmit the instruction to a circuit outside of the electronic device 400 (for example, to a smartphone wirelessly coupled with the earbud). As a further example, the processing circuit 402 may control the execution of the action by itself.

[0075] In principle, the occurrence of the detected (touching) event may trigger any suitable response depending on the type of electronic device 400. As examples, considering the case in which the electronic device 400 is a earbud, the processing circuit 402 may be configured to cause, upon detection of the touching event 462, one or more of: a change in volume of audio reproduced via the earbud, a change in reproduction speed of audio reproduced via the earbud, a change in which audio file is reproduced via the earbud, and the like.

[0076] FIG.4A and FIG.4B show further possible components that the SMI sensor 410 may include. For example, in various aspects the SMI sensor 410 may include a substrate 418 on which the components of the SMI sensor 410 are disposed. The substrate 418 may be for example a printed circuit board (PCB) substrate. In this configuration, the SMI sensor 410 may be an integrated circuit, e.g. the components of the SMI sensor 410 may be integrated on the (same) substrate 418.

[0077] As a further example, in various aspects the SMI sensor 410 may include a packaging 422. The packaging 422 may encapsulate the components of the SMI sensor 410. For example, the material of the packaging 422 may be transparent for light with wavelength in the emission range of the light emitter 412. As another example, the packaging 422 may be opaque for light with wavelength in the emission range of the light emitter 412, thus reducing the effect of background light. In this second configuration, the packaging 422 may include an opening to allow the light 424 to propagate towards the functional portion 446 and return back towards the laser cavity.

[0078] As a further aspect, the presence of the functional portion 446 may reduce the influence of background light 430 on the SMI detection. Illustratively, the monolithicallyformed functional portion 446 makes the housing 440 thicker in correspondence of the SMI detector 410, so that the housing 440 itself may filter / block more of the background light 430 (e.g., ambient light, solar light) compared to a configuration without the functional portion. Furthermore, in the configuration with the reflective coating, the coating itself may provide a blocking function for light coming from the outside of the housing 440.

[0079] In FIG.4A to FIG.4C a configuration of the electronic device 400 with a single SMI sensor 410 and a single functional portion 446 is illustrated. It is however understood that in some aspects the electronic device 400 may include a plurality of SMI sensors 410, and the housing 440 may include a plurality of monolithically formed functional portions 446 in correspondence of the plurality of SMI sensors 410.

[0080] FIG .5A and FIG.5B illustrate aspects of the configuration of the functional portion of the housing in relation to focal point and radius of curvature.

[0081] According to various aspects, as shown in FIG.5 A, the functional portion 502 (an exemplary realization of the functional portion 306, 446) may be configured to define a focal point 506 located beyond the light emitter 504 (e.g., the VCSEL). Illustratively, considering a concave shape for the functional portion 502, the focal point 506 of the “concave mirror” may be designed to be downstream of an emitting surface of the light emitter 504 considering a direction pointing from the concave mirror to the light emitter 504. This configuration for the focal of the mirror allows more flexible tolerance from the light emitter to housing assembly (e.g., the VCSEL to case assembly). Some potential coupling may be lost, but the overall arrangement may be fabricated in a simpler manner.

[0082] Analogous considerations apply to the radius of curvature of a concave functional portion, as shown in FIG.5B for functional portions 510, 520, 530, 540 with different radius of curvature. In particular, FIG.5B shows a first concave functional portion 510 with radius of curvature -3.0 mm, a second concave functional portion 520 with radius of curvature -2.0 mm, a third concave functional portion 530 with radius of curvature -1.0 mm, and a fourth concave functional portion 540 with radius of curvature -0.5 mm. In general, it has been found that a radius of curvature around -1 mm provides optimal coupling for SMI detection considering typical dimensions of light emitter, SMI sensor, and electronic device for the application of interest (e.g., for use in an earbud).

[0083] FIG.6 shows a comparison between different configurations of a housing for use in combination with a self-mixing interferometry sensor, in a schematic representation according to various aspects. In particular, FIG.6 shows the enhanced coupling provided bythe engineering of the housing with respect to conventional configurations in which the housing does not include a functional portion. FIG.6 shows different configurations in which the light emitter 612 (e.g., the VCSEL) of a SMI sensor 610 emits light towards a housing 602a, 602b, 602c, 602d.

[0084] In a first configuration 620 the housing 602a does not include a functional portion as described herein, and further the SMI sensor 610 does not include a lens or focusing optical element. In this configuration 620 the coupling factor may be calculated aswhere f2apertureis the aperture of the light emitter 612 (e.g., the VCSEL aperture), and 2n describes a half hemisphere (considering a total space of 4n steradians).

[0085] In a second configuration 630 the housing 602b does not include a functional portion as described herein, but the SMI sensor 610 does include a lens 614 for focusing the emitted light. In this configuration 630 the coupling factor may be calculated as ~where f2iensis the aperture of the lens 614, which is much larger than the aperture of the light emitter, thus achieving an enhanced coupling compared to the first configuration 620.

[0086] Turning now to a third configuration 640 in which the housing 602c does include a concave functional portion 604c and the SMI sensor 610 is free of a lens (e.g., as discussed in relation, to FIG.4A), the coupling factor may be calculated as+is the aperture of the light emitter 612, (lmirroris theaperture of the concave functional portion 604c, and R and L represent the fraction of direct reflection (R) and Lambertian reflection (L) for the bare material of the housing 602c. As can be seen, this configuration provides an enhancement compared to the first configuration 620, and still ensures a sufficient coupling (and contrast) for SMI detection while having a simpler setup without a lens 614. The enhancement with respect to the first configuration 620 (also applicable to the second configuration 630) may be provided by the concave shape that provides an aperture much smaller than the half hemisphere 2n.

[0087] A further enhancement may be provided with a fourth configuration 650 in which the housing 602d includes a concave functional portion 604d with a reflective coating 606d, and the SMI sensor 610 is free of a lens (e.g., as discussed in relation, to FIG.4B). In this configuration 650, the coupling factor may be calculated as providing afurther increase for the coupling factor with respect to the “simple” concave functional portion of the third configuration 640.

[0088] FIG.7 shows a schematic flow diagram of a method 700 of providing a housing for an electronic device. The method 700 may in general include forming a housing for an electronic device, wherein the housing includes a housing portion and a functional portion monolithically formed with the housing portion, with the functional portion configured to cause a reflection of light towards the interior of the housing. In principle, various possibilities may exist for providing a housing as described herein. In a preferred configuration, which allows a simple and scalable fabrication, injection molding may be used to form the housing with the integrally formed functional portion. It is understood that the aspects described in relation to the housing 300, 440 apply to the method 700, and vice versa.

[0089] According to various aspects, the method 700 may include, in 710, providing a mold for molding a housing for an electronic device. The mold may define a chamber for injecting a molding material. According to the proposed configuration, the mold may define a housing portion of the housing and further may define the shape of a functional portion of the housing. The method 700 may include clamping to close the parts forming the mold (e.g., the two halves of the mold). For example, the mold may define the shape of the housing and a concave shape in correspondence of the functional portion.

[0090] The method 700 may further include, in 720, injecting a molding material into the chamber defined by the mold. The injected molding material may assume the profile defined by the mold, thus defining the housing portion and the functional portion of the housing. The method 700 may further include, in 730, a hardening of the injected molding material. For example the method 700 may include a “cooling” step in which the injected molding material cools down and solidifies. The method 700 may further include, in 740, removing (ejecting) from the mold the molded housing including the housing portion and the functional portion monolithically molded with the housing portion.

[0091] In some aspects, the method 700 may further include providing a reflective coating on the functional portion. For example, the method 700 may include depositing a reflective layer (e.g., a metal layer) on the functional portion. As another example, the method 700 may include coating the functional portion with a reflective powder, e.g. a metal powder. In some aspects, the metal deposition may be carried out contextually with metal deposition for other parts of an electronic device, e.g. for forming other circuits or interconnections.

[0092] FIG.8 shows a schematic flow diagram of a method 800 of providing an electronic device including a housing and a SMI sensor, according to various aspects. It is understoodthat the aspects described in relation to the electronic device 400 apply to the method 800, and vice versa.

[0093] The method 800 may include, in 810, providing a housing for the electronic device, wherein the housing includes a housing portion defining an interior space of the housing and a functional portion monolithically formed with the housing portion and configured to act as a mirror to cause reflection of light within the interior space of the housing. For example, the method 800 may include providing a housing according to the method 700 described in relation to FIG.7.

[0094] The method 800 may further include, in 820, disposing a SMI sensor within the interior space of the housing. In particular, the method 800 may include disposing the SMI sensor such that light emitted by a laser resonator cavity of a light emitter of the SMI sensor hits the functional portion of the housing, and light traveling back from the functional portion of the housing towards the light emitter enters the laser resonator cavity. For example, the method 800 may include aligning the light emitter with the functional portion, e.g. with the geometrical center of the functional portion.

[0095] Below are some examples that relate to what is described here and shown in the figures.

[0096] Example 1 is an electronic device including: a housing including: a housing portion defining an interior space of the housing; and a functional portion monolithically formed with the housing portion and configured to act as a mirror to cause reflection of light within the interior space of the housing; and a self-mixing interferometry sensor disposed within the interior space of the housing and including a light emitter with a laser resonator cavity configured to emit laser light. The functional portion of the housing is configured to receive laser light emitted by the laser resonator cavity and to cause the received laser light to travel back towards the laser resonator cavity.

[0097] In Example 2, the subject matter of Example 1 can optionally include that the housing is an injection molded housing. The functional portion is monolithically molded with the housing portion.

[0098] In Example 3, the subject matter of Example 1 or 2 can optionally include that the functional portion has a concave shape. A concave region of the functional portion faces the light emitter.

[0099] In Example 4, the subject matter of Example 3 can optionally include that the concave region of the functional portion has a radius of curvature with an absolute value in the range from 0.5 mm to 2 mm.

[0100] In Example 5, the subject matter of any one of Examples 1 - 4 can optionally include that a surface of the functional portion facing the light emitter has a surface treatment configured to increase a reflectivity of the functional portion with respect to an untreated portion of the housing.

[0101] In Example 6, the subject matter of any one of Examples 1 - 5 can optionally include that a surface of the functional portion facing the light emitter has a surface roughness less than a surface roughness of at least a portion of the housing portion facing the interior space of the housing.

[0102] In Example 7, the subject matter of any one of Examples 1 - 6 can optionally include that the functional portion includes a reflective coating configured to be reflective for light with wavelength in an emission wavelength range of the light emitter.

[0103] In Example 8, the subject matter of Example 7 can optionally include that the reflective coating includes or is made of a metal material.

[0104] In Example 9, the subject matter of any one of Examples 1 - 8 can optionally include that the self-mixing interferometry sensor is free of a lens in the optical path between the light emitter and the functional portion.

[0105] In Example 10, the subject matter of any one of Examples 1 - 9 can optionally include that the functional portion is configured to have a focal point located beyond the light emitter considering a direction pointing from the functional portion towards the light emitter.

[0106] In Example 11, the subject matter of any one of Examples 1 - 10 can optionally further include a processing circuit configured to: identify a variation of one or more operational parameters of the laser resonator cavity caused by an interference of the laser light generated in the cavity with the laser light travelling back to the laser cavity; and identify a touching event on the housing based on the identified variation of the one or more operational parameters of the laser resonator cavity.

[0107] In Example 12, the subject matter of Example 11 can optionally include that the self-mixing interferometry sensor further includes a photodetector configured to: generate a detection signal representative of the laser light generated in the laser resonator cavity; and provide the detection signal to the processing circuit.

[0108] In Example 13, the subject matter of Example 11 or 12 can optionally include that the processing circuit is configured to identify one or more properties of the touching event on the housing based on the identified variation of the one or more operating parameters of the laser resonator cavity. The one or more properties of the touching event include: a force of the touching event; a speed of the touching event; and / or a direction of the touching event.

[0109] In Example 14, the subject matter of any one of Examples 1 - 13 can optionally include that the housing has a shape such that at least part of the housing may fit into an ear of a user of the electronic device.

[0110] Example 15 is an injection molded housing for an electronic device, the injection molded housing including: a housing portion defining an interior space of the injection molded housing; and a functional portion monolithically molded with the housing portion. The functional portion has a concave shape and is configured to act as a mirror to cause reflection of light within the interior space of the injection molded housing.

[0111] The terms “processor”, “processing circuit”, or “control circuit” as used herein may be understood as any kind of technological entity that allows handling of data. The data may be handled according to one or more specific functions that the processor / processing circuit / control circuit may execute. Further, a processor / processing circuit / control circuit as used herein may be understood as any kind of circuit, e.g., any kind of analog or digital circuit. A processor / processing circuit / control circuit may thus be or include an analog circuit, digital circuit, mixed-signal circuit, logic circuit (e.g., a hard-wired logic circuit or a programmable logic circuit), microprocessor, Central Processing Unit (CPU), Graphics Processing Unit (GPU), Digital Signal Processor (DSP), Field Programmable Gate Array (FPGA), integrated circuit, Application Specific Integrated Circuit (ASIC), etc., or any combination thereof. It is understood that any two (or more) of the processors / processing circuits / control circuits detailed herein may be realized as a single entity with equivalent functionality or the like, and conversely that any single processor / processing circuit / control circuit detailed herein may be realized as two (or more) separate entities with equivalent functionality or the like.

[0112] The word “over” or “on”, used herein to describe forming a feature “over” or “on” a side or surface, may be used to mean that the feature may be formed “directly over” or “directly on”, e.g., in direct physical contact with, the side or surface. The word “over” or “on” may be alternatively used to mean that the feature may be formed “indirectly over” or“indirectly on” the implied side or surface with one or more additional layers disposed therebetween.

[0113] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration”. Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

[0114] The phrase “at least one” and “one or more” may be understood to include a numerical quantity greater than or equal to one (e.g., one, two, three, four, [...], etc.). The phrase “at least one of’ with regard to a group of elements may be used herein to mean at least one element from the group consisting of the elements. For example, the phrase “at least one of’ with regard to a group of elements may be used herein to mean a selection of: one of the listed elements, a plurality of one of the listed elements, a plurality of individual listed elements, or a plurality of a multiple of individual listed elements.

[0115] All acronyms defined in the above description additionally hold in all claims included herein.

[0116] While the invention has been particularly shown and described with reference to specific aspects, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes, which come within the meaning and range of equivalency of the claims, are therefore intended to be embraced.List of reference signs 424 Laser light430 Background light100 SMI sensor102 Light source104 Emitted light 440 Housing106 Target 442 Housing portion108 Return light 446 Functional portion110 Photodetector 446a Functional portion112 External cavity 446b Functional portion 200 SMI sensor 448a Concave region 200b SMI sensor 450b Reflective coating 200c SMI sensor 502 Functional portion 202 Laser source 504 Light emitter204 Emitted laser light 506 Focal point 204b Emitted laser light 510 Functional portion 204c Emitted laser light 520 Functional portion 206 Target 530 Functional portion208 Return light 540 Functional portion210 Photodetector 602a Housing214 Analog-to-Digital Converter 602b Housing216 Lens 602c Housing220 Housing 602d Housing222 Touch 604c Functional portion230 Background light 604d Functional portion250 Earbud 606d Reflective coating300 Housing 610 SMI sensor 300a Housing 612 Light emitter 300b Housing 620 First configuration302 Housing portion 630 Second configuration304 Interior space 640 Third configuration306 Functional portion 650 Fourth configuration 306a Functional portion 700 Method 306b Functional portion 710 Method step 308a Concave region 720 Method step 310b Reflective coating 730 Method step 322 Housing wall 740 Method step324 Housing wall 800 Method326 Housing wall 810 Method step328 Housing wall 820 Method step400 Electronic device 400a Electronic device 400b Electronic device 402 Processing circuit 410 SMI sensor 412 Light emitter 414 Photodetector416 Analog-to-Digital Converter 418 Substrate422 Packaging

Claims

Claims1. An electronic device (400) comprising: a housing (440) comprising: a housing portion (442) defining an interior space of the housing (440); and a functional portion (446) monolithically formed with the housing portion (442) and configured to act as a mirror to cause reflection of light within the interior space of the housing (440); and a self-mixing interferometry sensor (410) disposed within the interior space of the housing (440) and comprising a light emitter (412) with a laser resonator cavity configured to emit laser light, wherein the functional portion (446) of the housing is configured to receive laser light emitted by the laser resonator cavity and to cause the received laser light to travel back towards the laser resonator cavity; wherein the functional portion (446) has a concave shape, and wherein a concave region (448a) of the functional portion (446) faces the light emitter (412).

2. The electronic device (400) according to claim 1, wherein the housing (440) is an injection molded housing, and wherein the functional portion (446) is monolithically molded with the housing portion (442).

3. The electronic device (400) according to claim 1 or 2,wherein the concave region (448a) of the functional portion (446) has a radius of curvature with an absolute value in the range from 0.5 mm to 2 mm.

4. The electronic device (400) according to any one of claims 1 to 3, wherein a surface of the functional portion (446) facing the light emitter (412) has a surface treatment configured to increase a reflectivity of the functional portion with respect to an untreated portion of the housing (440).

5. The electronic device (400) according to any one of claims 1 to 4, wherein a surface of the functional portion (446) facing the light emitter (412) has a surface roughness less than a surface roughness of at least a portion of the housing portion (442) facing the interior space of the housing (440).

6. The electronic device (400) according to any one of claims 1 to 5, wherein the functional portion (446) comprises a reflective coating (450b) configured to be reflective for light with wavelength in an emission wavelength range of the light emitter (412).

7. The electronic device (400) according to claim 6, wherein the reflective coating (450b) comprises or is made of a metal material.

8. The electronic device (400) according to any one of claims 1 to 7, wherein the self-mixing interferometry sensor (410) is free of a lens in the optical path between the light emitter (412) and the functional portion (446).

9. The electronic device (400) according to any one of claims 1 to 8,wherein the functional portion (446) is configured to have a focal point located beyond the light emitter (412) considering a direction pointing from the functional portion (446) towards the light emitter (412).

10. The electronic device (400) according to any one of claims 1 to 9, further comprising: a processing circuit (402) configured to: identify a variation of one or more operational parameters of the laser resonator cavity caused by an interference of the laser light generated in the cavity with the laser light travelling back to the laser cavity; and identify a touching event (462) on the housing (440) based on the identified variation of the one or more operational parameters of the laser resonator cavity.

11. The electronic device (400) according to claim 10, wherein the self-mixing interferometry sensor (410) further comprises a photodetector (414) configured to: generate a detection signal representative of the laser light generated in the laser resonator cavity; and provide the detection signal to the processing circuit (402).

12. The electronic device (400) according to claim 10 or 11, wherein the processing circuit (402) is configured to identify one or more properties of the touching event (462) on the housing based on the identified variation of the one or more operating parameters of the laser resonator cavity, wherein the one or more properties of the touching event comprise: a force of the touching event; a speed of the touching event; and / or a direction of the touching event.

13. The electronic device (400) according to any one of claims 1 to 12, wherein the housing (440) has a shape such that at least part of the housing (440) may fit into an ear of a user of the electronic device (400).

14. An injection molded housing (300) for an electronic device, the injection molded housing (300) comprising: a housing portion (302) defining an interior space (304) of the injection molded housing (300); and a functional portion (306) monolithically molded with the housing portion (302), wherein the functional portion (306) has a concave shape and is configured to act as a mirror to cause reflection of light within the interior space (304) of the injection molded housing (300); wherein the functional portion (446) has a concave shape, and wherein a concave region (448a) of the functional portion (446) faces the light emitter (412).

15. A method of manufacturing an injection molded housing (300) for an electronic device, the method comprising: providing a housing for the electronic device, wherein the housing includes a housing portion defining an interior space of the housing and a functional portion monolithically formed with the housing portion and configured to act as a mirror to cause reflection of light within the interior space of the housing; and disposing a self-mixing interferometry sensor within the interior space of the housing.

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