Self-Mixing Optical Proximity Sensors for Electronic Devices
1. An electronic device, comprising:
- a housing;
an adjustable component in the housing;
an incoherent self-mixing sensor in the housing; and
control circuitry in the housing that is configured to gather a sensor measurement with the incoherent self-mixing sensor and that is configured to adjust the adjustable component using the sensor measurement.
An electronic device may have optical sensors. Control circuitry may use sensor measurements in controlling adjustable components and taking other actions. The optical sensors may be self-mixing sensors such as incoherent self-mixing sensors. One or more sensors may be used in gathering sensor measurements. In configurations in which an electronic device contain multiple self-mixing sensors, multi-wavelength measurements can be gathered using incoherent light sources in the sensors that operate a set of different wavelengths. The light source of each incoherent self-mixing sensor may be a superluminescent light-emitting diode, a resonant cavity light-emitting diode, or other amplified or non-amplified spontaneous emission source. Optical systems such as lenses in a housing for an electronic device may be aligned with the self-mixing sensors. Self-mixing sensors may serve as proximity sensors, sensors for detecting touch input, sensors for measuring spectrums associated with targets of unknown materials, displacement sensors, or other sensors.
- 1. An electronic device, comprising:
a housing; an adjustable component in the housing; an incoherent self-mixing sensor in the housing; and control circuitry in the housing that is configured to gather a sensor measurement with the incoherent self-mixing sensor and that is configured to adjust the adjustable component using the sensor measurement.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
- 11. An electronic device, comprising:
incoherent self-mixing sensors each having a respective light source configured to emit light at a different respective wavelength; an adjustable component; and control circuitry configured to adjust the adjustable component using sensor data from the incoherent self-mixing sensors.
- View Dependent Claims (12, 13, 14)
- 15. An electronic device comprising:
an adjustable component with a movable member; an incoherent self-mixing sensor having a diode configured to emit light that illuminates the movable member; and control circuitry configured to adjust the adjustable component using a sensor measurement from the incoherent self-mixing sensor.
- View Dependent Claims (16, 17, 18, 19)
This application claims the benefit of provisional patent application No. 62/663,599, filed Apr. 27, 2018, which is hereby incorporated by reference herein in its entirety.
This relates generally to electronic devices, and, more particularly, to optical sensors for electronic devices.
Electronic devices may contain optical sensors. For example, earbuds may contain optical proximity sensors based on infrared light-emitting diodes and infrared photodetectors. An optical proximity sensor may use an infrared light-emitting diode to emit infrared light. The emitted infrared light may reflect or backscatter off of an object in the vicinity of the proximity sensor. The strength of the reflected or backscattered light may be measured using an infrared photodetector to determine whether the object is near or far from the sensor. An earbud can use a proximity sensor to gather information on the operating state of the earbud such as whether the earbud has been inserted into the ear of a user. A cellular telephone may also use a proximity sensor to detect whether a touch screen in the cellular telephone is adjacent to a user'"'"'s head.
Challenges can arise in gathering operating state information with an optical proximity sensor. For example, the intensity of emitted infrared light that is reflected or backscattered from a nearby object can be affected by the reflectivity and bidirectional reflectance distribution function (BRDF) of the object, which can lead to measurement inaccuracies.
An electronic device may have one or more optical sensors. Control circuitry in the electronic device may use sensor measurements from the optical sensors in controlling adjustable components and taking other actions. For example, an electronic device may have adjustable components such as a speaker, a touch screen display, a haptic output device, a motor or other actuator, and/or other components. The control circuitry can adjust components such as these using sensor measurements from the optical sensors.
The optical sensors may be self-mixing sensors such as resonant-cavity light-emitting diode self-mixing sensors or other self-mixing sensors based on incoherent light sources (e.g., a light-emitting diode, a superluminescent diode, or other amplified or non-amplified spontaneous-emission-based source of electromagnetic radiation). One or more sensors may be used in gathering sensor measurements. In configurations in which an electronic device contain multiple self-mixing sensors, spectral measurements can be gathered using light-emitting diodes in the sensors operating at a set of different wavelengths. The light-emitting diode of each resonant-cavity light-emitting diode self-mixing sensor may be a visible-light diode, an ultraviolet diode, or an infrared diode.
An optical system containing optical components such as lenses may be mounted in a housing sidewall or other housing structure for an electronic device. The optical system may be aligned with one or more self-mixing sensors in the housing. Self-mixing sensors may serve as proximity sensors, sensors for detecting touch input, displacement sensors, sensors for measuring spectrums associated with targets of unknown materials, or other sensors.
An illustrative electronic device of the type that may be provided with one or more optical sensors such as self-mixing sensors is shown in
As shown in
Electrical components in device 10 such as input-output devices 12 may be used to allow data to be supplied to device 10, to allow data to be provided from device 10 to external devices, and/or to perform other functions in device 10. Control circuitry 16 and input-output devices 12 may be mounted in a housing for device 10 (e.g., a housing formed from polymer, glass, ceramic, metal, other materials, and/or combinations of these materials).
Input-output devices 12 may include buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, light-emitting diodes and other status indicators, displays (e.g., organic light-emitting diode displays, liquid crystal displays, displays with touch screens, displays without touch screens, etc.), data ports, other adjustable components (e.g., motors, haptic output devices, adjustable touch sensors in displays, etc.). A user can control the operation of device 10 by supplying commands through input-output devices 12 and may receive status information and other output from device 10 using the output resources of input-output devices 12.
Input-output devices 12 may also include sensors 18. Sensors 18 may include one or more sensors such as an ambient light sensor, a capacitive proximity sensor, a magnetic sensor, an inertial measurement unit (e.g., a sensor that includes an accelerometer, compass, and/or gyroscope for measuring motion and orientation), a force sensor, a capacitive touch sensor, a temperature sensor, a pressure sensor, a gas sensor, a microphone, a depth sensor, a three-dimensional gesture sensor, a structured light sensor for gathering depth information, a touch sensor in a touch screen display, or other sensors.
Sensors 18 may include one or more optical sensors such as self-mixing sensors. Self-mixing sensors may contain a device that emits visible or invisible electromagnetic radiation (e.g., an amplified or non-amplified spontaneous-emission-based source of electromagnetic radiation). A portion of this emitted radiation can be coupled back to this radiation-emitting device via reflection or scattering from an object, which can be defined by a reflectivity and bidirectional reflectance distribution function in the beam path and creates feedback (e.g., by altering the carrier density in a solid state device). This feedback can be measured by electrical sensing, optical sensing, and/or other sensing arrangements, and used in producing sensor output.
Optical self-mixing sensors for device 10 may be based on resonant-cavity light-emitting diodes (resonant-cavity LEDs or RC-LEDs). Such light-emitting diodes have coherence lengths on the order of tens of microns so that for operating ranges that are larger than tens of microns, they are incoherent. Accordingly, self-mixing sensors based on resonant-cavity light-emitting diodes may sometimes be referred to herein as incoherent self-mixing sensors. If desired, incoherent self-mixing sensors can be implemented using other low-coherence or incoherent light sources such as superluminescent diodes and light-emitting diodes other than RC-LEDs.
Incoherent self-mixing sensors (e.g., resonant-cavity light-emitting diode self-mixing sensors, etc.) may be used in forming optical proximity detectors and other sensing devices in device 10. An optical proximity detector may detect when a person'"'"'s body part (e.g., ear, head, fingers, etc.) or other external object is near to the optical proximity detector. In some configurations, resonant-cavity light-emitting diode self-mixing sensors may be used in an electronic device to detect finger gestures, key press input and/or other purposeful user input (e.g., self-mixing sensors may serve as touch sensors that detect finger contact with a surface in a keyboard and thereby receive key press input. Self-mixing sensors may also detect touch sensor input as a user moves one or more fingers or other objects across a touch surface and may perform other user input functions (e.g., by detecting button press input, and/or other user input).
In some configurations, incoherent self-mixing sensors can be used to measure the horizontal or vertical displacement with respect to the direction of light propagation of a movable structure in device 10. For example, a resonant-cavity light-emitting diode self-mixing sensor may monitor movement of a diaphragm in a speaker or other movable structures in an electronic device component. By monitoring the excursions of a speaker diaphragm, audio drive signals can be adjusted to compensate for speaker distortion and/or scenarios in which a speaker has a potential for being over driven may be avoided. Another possibility is the detection of horizontal movement when the target surface has a spatially varying reflectance and/or bidirectional reflectance distribution function. In this case, the time-varying feedback can be used to deduce the horizontal movement. This can be used, for example, with an optical watch crown in an electronic device such as a wristwatch.
If desired, incoherent self-mixing sensors can be used to measure the optical properties of gases, solids, or liquids. For example, one or more incoherent self-mixing sensors may be used to gather infrared light measurements on the environment in which an electronic device is operating. Such light measurements may be sensitive to the optical properties of the air surrounding the device and/or the optical properties of objects in the vicinity of the device. In some arrangements, spectral data may be gathered that can be used in identifying materials in the environment of an electronic device. For example, incoherent self-mixing sensor measurements can be used to gather spectral curves for objects in the vicinity of an electronic device and/or measurements on the air surrounding an electronic device.
Incoherent self-mixing sensors can be used in any suitable type of electronic device (e.g., one or more of devices 10 of
During insertion of earbud 20 into an ear of a user, a user'"'"'s fingers may grasp stalk portion 22-1 (as an example). Earbud 20 may have one or more self-mixing sensors at locations such as locations 26. The self-mixing sensors may serve as proximity sensors and/or touch sensors (as examples). Self-mixing sensors may be formed on ear portion 22-2 (e.g., to form proximity sensors that monitor when ear portion 22-2 is adjacent to portions of a user'"'"'s ear and thereby determine when earbud 20 is in a user'"'"'s ear). If desired, self-mixing sensors may also be formed on stalk portion 22-1. In configurations in which self-mixing sensors are located on stalk portion 22-1, the sensors can be used to monitor when a user is grasping stalk 22-1. Stalk-mounted sensors and/or sensors on ear portion 22-2 (e.g., a one-dimensional or two-dimensional arrays of sensors) may serve as a touch sensor to gather user finger input. For example, a touch sensor formed from self-mixing sensors may gather finger touch input such as user taps on stalk portion 22-1, user finger swipes along the length of stalk portion 22-1, and/or other user input (sometimes referred to as finger gestures or finger input).
Semiconductor active region 38 may be formed between mirrors 36. Active region 38 may, if desired, include quantum well structures configured to allow light-emitting diode 32 to produce light at a desired output wavelength. The left-hand mirror in light-emitting diode 32 of
If desired, other types of incoherent light sources may be used in forming incoherent self-mixing sensor 30. For example, an edge-emitting light-emitting diode may be used that produces light output from edge of a light-emitting diode die or a surface-emitting light-emitting diode may be used that produces light output from the surface of a light-emitting diode die. Typical bandwidths for these light-emitting diodes are about 100 nm (full-width half maximum). In some configurations, superluminescent diodes may be used as incoherent light sources. A superluminescent light-emitting diode may be formed from an edge-emitting diode structure that generates output partially from stimulated emission. The output of a superluminescent light-emitting diode is higher than the edge-emitting or surface-emitting light-emitting diode and may be characterized by a bandwidth of 30-40 nm (as an example).
During operation, resonant-cavity light-emitting diode 32 may be controlled by applying a signal to terminals 40 using control circuitry 16 (e.g., a bias circuit in circuitry 16). This causes light-emitting diode 32 to emit light 46. Light 46 illuminates target 48, which reflects a portion of emitted light 46 back towards light-emitting diode 32 as reflected light 50. Target 48 may be an optically flat surface (e.g., a specular reflector), may be an optically rough surface with diffusive/scattering properties, and/or can be defined by a bidirectional reflectance distribution function that is suitable for the operation of sensor 30.
Emitted light 46 and therefore reflected light 50 may have any suitable wavelength such as a visible light wavelength (e.g., 390 nm to 700 nm), an ultraviolet light wavelength (e.g., less than 390 nm), an infrared wavelength, a near-infrared wavelength (e.g., 0.75-1.4 microns), a short-wavelength infrared (e.g., 1.4-3 microns), a mid-wavelength infrared wavelength (e.g., 3-8 microns), a wavelength of at least 1 micron, at least 1.5 microns, at least 2 microns, at least 3 microns, at least 3.5 microns, at least 5 microns, less than 10 microns, less than 8 microns, or other suitable wavelength. In some configurations, multiple light-emitting diodes 32 may be incorporated into device 10. In these configurations, output light 46 may have any suitable set of shared and/or different wavelengths such as these.
Target 48 may be, for example, a user'"'"'s body part (e.g., ears, fingers, etc.), a glass or polymer layer in a building, vehicle, electronic device, or other object, a thin-film interference filter formed from a stack of dielectric layers configured to form a wavelength-dependent optical filter and/or a dielectric mirror, a metallic reflector, other optical filters and/or mirrors, a gaseous substance (e.g., ambient air), a liquid, solid materials such as ceramic, crystalline materials such as sapphire, natural materials such as wood or leather, polymers, inorganic dielectrics, metals, other materials, and/or combinations of any two or more of these materials.
Some of light 50 that is directed back towards light-emitting diode 32 (e.g., light that reflected backwards due to a specular reflection from target 48 and/or that is backscattered from a diffuse surface of target 48) reenters light-emitting diode 32 and perturbs the carrier density in light-emitting diode 32 through the modification of the steady-state photon density and distribution within the device. This perturbation of the carrier density in light-emitting diode 32 causes changes in the current and junction voltage and emitted optical power of light-emitting diode 32 in relation to the amount of light 50 that reenters light-emitting diode. These changes in the electrical characteristics of light-emitting diode 32 can be detected using sensing circuitry in control circuitry 16. Circuitry 16 may, as an example, include a voltage sensor that measures the junction voltage of light-emitting diode 32 across active region 38 and/or a current sensor that measures the current flowing through diode 32 (e.g., the current flowing through terminals 40).
In another embodiment, a photodiode placed under, above, or adjacent to the emitter can be used to detect changes in the emitted optical power. These changes can then be used to produce a sensor output.
In some configurations, the self-mixing behavior of light-emitting diode 32 may be used to form a distance sensor capable of estimating distance between sensor 30 and a target object. For a diffusive target, the intensity of light 50 that is reenters light-emitting diode 32 is proportional to 1/X2, where X is the distance separating light-emitting diode 32 of sensor 30 and target 48. As a result, sensor 30 may be used to measure distance X between sensor 30 and target 48 when the target reflectance and bidirectional reflectance distribution function is known. If desired, sensor 30 may, as an example, be configured to serve as a proximity sensor (e.g., a distance sensor in which the light signal reflecting from objects is compared to a threshold distance or is otherwise processed to determine whether the objects are located within the vicinity of sensor 30).
The amount of light 50 that is sensed by light-emitting diode 32 is also affected by the optical properties of target 48. This allows sensor 30 to gather information on the material(s) making up target 48. As an example, if a first target 48 strongly absorbs or transmits light at a particular wavelength or set of wavelengths, whereas a second target 48 reflects this light, control circuitry 16 can determine that the first and second targets 48 are formed from different materials and/or can use spectral measurements to identify particular materials.
In arrangements in which multi-spectral measurements (measurements at multiple wavelengths) can be made using sensors 30, control circuitry 16 can use target spectral characteristics in identifying the nature of targets 48. Consider, as an example, the graph of
During operation, light 46 that is emitted by light-emitting diode 32 may pass through optical system 62 and reflected or scattered light 50 may pass through optical system 62. In configurations in which light 46 is in the visible spectrum, optical system 62 may be formed from material that is transparent at visible light wavelengths (e.g., glass, polymer, sapphire, etc.). At longer wavelengths (e.g., infrared wavelengths up to mid-wavelength infrared, as an example), other materials may be used (e.g., chalcogenide glass, calcium fluoride, silicon, germanium, zinc selenide, and/or other materials that are transparent at these infrared wavelengths).
To measure a sample such as an air sample or a sample of other gas, optical system 62 may include multiple lenses such as lenses 64 of
In the illustrative arrangement of
Illustrative sensing (and biasing) circuits that may be used for gathering signals from resonant-cavity light-emitting diode 32 in sensor 30 are shown in
In the example of
If resistor 84 of
To address this issue, sensor 30 of
In the arrangement of
During the operations of block 102, device 10 may use control circuitry 16 (e.g., sensing circuitry such as the illustrative circuitry of
During the operations of block 104, control circuitry 16 may process sensor readings from sensor(s) 30 and/or other data (e.g., data from sensors 18 and/or other data sources). The processing operations of block 104 may be used, for example, to detect the presence of an external object such as a user'"'"'s finger, head, or other body part, an external object such as an object in the user'"'"'s environment (e.g., a building, furniture, etc.), to detect the presence of object moving relative to device 10 (e.g., stationary objects through which device 10 is navigating and/or moving objects and/or moving parts in device components), to measure material properties of materials in target 48 (e.g., to distinguish glass from polymer using infrared measurements and/or visible light measurements such as spectral measurements made with sensors 30 operating at a set of multiple different respective wavelengths), and/or to otherwise process the data gathered from light-emitting diode 32. In some configurations, touch input can be detected (e.g., touch gestures such as finger taps, finger swipes, pinch-to-zoom gestures, etc.). Proximity data can be gathered indicating whether objects are in the vicinity of device 10 and sensor 30. For example, data from sensor 30 can be processed to estimate the distance between sensor 30 and external objects over a distance of at least 1 mm, at least 10 mm, at least 10 cm, less than 50 mm, less than 12 mm, or other suitable distance. This distance information may, if desired, be compared to distance threshold information to determine whether objects are in the vicinity of sensor 30 or are not in the vicinity of sensor 30.
During the operations of block 106, control circuitry 16 can take suitable action based on self-mixing sensor data from sensor 30. For example, user input, information on the distance between self-mixing sensor 30 and target 48 (e.g. displacement information for a moving device component and/or information on the separation between sensor 30 and a user body part or other external object), information on the material that forms target 48, and/or other self-mixing sensor information (raw and/or preprocessed data from block 104) can be used in controlling processing circuitry in device 10 or an associated electronic device (e.g., an electronic device such as device 10 or that is linked to device 10 via a wired or wireless communications link). A user may, for example, supply text input, button press input, touch gesture input, three-dimensional gesture input, or other input to a computer or other device. A moving device such as a vehicle may use sensor information to adjust steering motors and/or other adjustable components to avoid obstacles (e.g., obstacles such as glass or plastic walls that appear transparent at visible light wavelength but that are detectable at infrared wavelengths). In a portable electronic device such as a cellular telephone, sensor 30 may serve as a proximity sensor and control circuitry 16 can use proximity information to place device 10 in different modes of operation based on whether external objects are present in the vicinity of device 10. For example, when no objects are near to sensor 30, control circuitry 16 may place control circuitry 16 (and device 10) in a normal operating mode in which a touch screen display in device 10 is configured to gather touch sensor input (e.g., from a user'"'"'s fingers), whereas when objects are present near to sensor 30, control circuitry 16 may temporarily deactivate the touch sensor in the touch screen display so that contact with the user'"'"'s head or other nearby object does not inadvertently contact the touch sensor in the touch screen display and supply the touch sensor with erroneous input. In general, any suitable actions may be taken during the operations of block 106 (e.g., controlling adjustable device components such as displays and status indicators to display information, to control adjustable device components such as speakers to provide audio output, to control adjustable components such as touch sensors so that touch sensors are active or inactive, to control adjustable haptic devices to supply haptic output, to control wired and/or wireless components to transmit information to external devices, to control motors and/or other actuators to control movement of wheels, aircraft components, other vehicle steering components, and/or other parts of a moving vehicle, to control motors and actuators in non-vehicular equipment, and/or to control other adjustable circuitry/components in device 10 and/or other equipment).
The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.