Optical Proximity Sensor Systems

Abstract

A device includes a display screen and an optical proximity sensor module disposed behind the display screen. The optical proximity sensor module includes: a light emitter operable to generate light having a wavelength for transmission through the display screen toward a target object; and a light sensor operable to sense light reflected by the target object and having the wavelength. The optical proximity sensor module may include a component for reducing the maximum energy density of a light beam generated by the light emitter. The component for reducing the maximum energy density of the light beam is disposed between the light emitter and the display screen so as to intercept the light beam generated by the light emitter. In some cases, there are multiple light emitters that can operate together to provide sufficient optical energy for proximity sensing without generating visible light spots on the display screen. These and other techniques can help reduce or eliminate display screen distortion caused by energy from the light emitter.

Description

Technical Field

[0001] The present disclosure relates to optical proximity sensing systems. Background Art

[0002] A recent trend in smartphone industrial design is to maximize the screen area by reducing the bezel width and de-cluttering the remaining bezel area by removing apertures for optical sensors and other apertures for microphones, speakers, and / or fingerprint reading devices. On the other hand, there is also a trend to increase the number of optical sensors to gain additional functionality. For example, in some cases, optical proximity sensors are integrated into smartphones to facilitate adjusting the display screen brightness when the user holds the smartphone close to her ear and to reduce the overall energy consumption of the display. Optical proximity sensing typically relies on emitting infrared (IR) or near infrared (NIR) light and measuring the light energy reflected back from the object to be detected.

[0003] Another trend in the smartphone market is the adoption of organic light emitting displays (OLEDs). This trend creates an opportunity to move the proximity sensor from the bezel of the smartphone to a location below the OLED. Thus, the proximity sensor is buried behind the OLED, which allows some light, including IR and NIR radiation, to pass through. However, the energy of IR or NIR light can sometimes cause screen distortion (e.g., bright spots on an OLED screen, which can be visible under certain conditions) even when the screen is displaying a black image. Summary of the invention

[0004] This disclosure describes techniques for helping to reduce or eliminate display screen distortion caused by energy from light emitters in a proximity sensor module.

[0005] For example, in one aspect, the present disclosure describes a device that includes a display screen and an optical proximity sensor module disposed behind the display screen. The optical proximity sensor module includes: a light emitter operable to generate light having a wavelength for transmission through the display screen toward a target object; and a light sensor operable to sense light reflected by the target object and having the wavelength; the optical proximity sensor module also includes a component for reducing the maximum energy density of the light beam generated by the light emitter. The component for reducing the maximum energy density of the light beam is disposed between the light emitter and the display screen so as to intersect the light beam generated by the light emitter.

[0006] Some embodiments include one or more of the following features. For example, in some cases, the display screen is an OLED display screen. For example, the component for reducing the maximum energy density of the light beam may include a microlens, a microlens array, and / or an optical diffuser. The component for reducing the maximum energy density of the light beam is operable to cause the light beam to diffuse radially so as to reduce the maximum energy density of the light beam incident on the OLED screen. In some embodiments, the light beam leaving the component for reducing the maximum energy density of the light beam has a larger half-beam, half-width than the light beam emitted by the light emitter. In some cases, the light emitter is operable to produce infrared or near-infrared light.

[0007] According to another aspect, the present disclosure describes a device including a display screen and an optical proximity sensor module disposed behind the display screen. The optical proximity sensor module includes: a plurality of light emitters operable to generate infrared or near-infrared light for transmission through the display screen toward a target object; and a light sensor operable to sense the infrared or near-infrared light reflected by the target object. The light emitters can collectively operate to provide sufficient optical energy for proximity sensing. Specifically, the light emitters disperse the optical energy used for the proximity sensing, thereby reducing distortion of the display screen.

[0008] In some cases, each of the light emitters is operable to generate an energy density such that the maximum energy density of light incident on the back side of the display screen is reduced while maintaining total energy to facilitate proximity sensing performance. For example, the display screen may be an OLED display screen.

[0009] The present disclosure also describes a method comprising: causing each of a plurality of VCSELs in an optical proximity sensor module disposed behind a display screen to generate infrared or near-infrared light for transmission through the display screen toward a target object. Each of the VCSELs generates a maximum power level of 2.0 mW, preferably a maximum power level of 1.5 mW. The method also includes sensing the infrared or near-infrared light reflected by the target object, and processing a signal corresponding to the sensed infrared or near-infrared light for proximity sensing. In some embodiments, the method includes applying a drive current in the range of 2 mA to 3 mA to each of the plurality of VCSELs. In some cases, such a method can help eliminate or reduce screen distortion.

[0010] Other aspects, features, and advantages will be apparent from the following detailed description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1Various features of a host device including an optical proximity sensor module behind a display screen are shown.

[0012] Figure 2 Details of an optical proximity sensor module according to a first embodiment are shown.

[0013] Figure 3A According to some embodiments, Figure 2 Further details of the proximity sensor.

[0014] Figure 3B yes Figure 3A Top view of the .

[0015] Figure 3C is through Figure 3B A cross-sectional view of line AA.

[0016] Figure 4 A first example of a microlens array is shown.

[0017] Figure 5 A second example of a microlens array is shown.

[0018] Figure 6 Details of an optical proximity sensor module according to a second embodiment are shown.

[0019] Figure 7 Details of an optical proximity sensor module according to a third embodiment are shown. DETAILED DESCRIPTION

[0020] As in Figure 1 As shown in , a host device 10, such as a portable computing device (e.g., a smart phone, a personal digital assistant (PDA), a laptop, or a wearable) includes an OLED-type or other display screen 12 that may be disposed directly below a front glass 20. An optical proximity sensor module 14 is disposed directly below a portion of the display screen 12 and is operable to emit light (e.g., infrared or near-infrared radiation) toward a target object external to the host device 10 and sense light reflected by the target object back toward the sensor module 14.

[0021] An electronic control unit (ECU) 16 is operable to receive, process, and analyze signals from the proximity sensor module 14, and in response, perform a specified action depending on, for example, the amount of light detected. In some cases, for example, the ECU 16 may cause the brightness of the display screen 12 to be adjusted. In some cases, the detection / release event is interrupt driven and occurs when the proximity result exceeds an upper and / or lower threshold setting. For example, the ECU 16 may be a processor for a sensor hub or some other processor in the portable computing device 10. The overall brightness of the OLED may be controlled, for example, by applying PWM modulation to each pixel using a transistor in series with the pixel or by adjusting the overall range of current that can drive each pixel.

[0022] As in Figure 2 As shown in the example of , the proximity sensor module 14 includes an emitter 22 (such as a light emitting diode (LED) or a vertical cavity surface emitting laser (VCSEL) operable to emit IR or NIR radiation (e.g., at a wavelength of 940nm)) and a factory calibrated LED driver. The proximity sensor module 14 also includes a light sensor 24, such as a photodiode receiver, operable to sense light having the same wavelength emitted by the emitter 22. The photodiode receiver may include associated circuitry operable to process signals from the photodiode. Each of the light emitter 22 and the photodiode receiver 24 may, for example, be implemented as a respective die (i.e., a semiconductor chip) and may be mounted on a printed circuit board or other substrate 34.

[0023] Some light emitters produce a light beam whose energy density is generally shaped like a bell curve, that is, its energy density has a maximum at or close to the central optical axis of the emitter and decreases with distance from the central optical axis. The maximum energy density produced by the emitter 22 can be sufficiently high to produce distortion on the LED screen 12 if steps are not taken to prevent the distortion.

[0024] As in Figure 2As further shown in the example of , the proximity sensor module 14 includes a component for reducing the maximum energy density generated by the light emitter 22 and incident on the OLED screen 12. Therefore, in some embodiments, the proximity sensor module 14 includes a microlens or a microlens array 26 disposed in the path of the light beam 28 emitted by the emitter 22. The microlens or microlens array 26 intercepts the light beam 28 before the light beam 28 is incident on the back side of the OLED screen 12 and causes the light beam 28 to be radially diffused to a certain extent, thereby reducing the maximum energy density of the light beam 30 incident on the OLED screen. Therefore, in general, the microlens or microlens array 26 produces a wider light beam 30 (e.g., a light beam with a larger half beam, half width) than the light beam 28 generated by the emitter 22 alone. Reducing the maximum energy density of the light beam 30 incident on the OLED screen 12 can reduce or eliminate screen distortion (or at least reduce or eliminate the user's perception of such distortion). In addition, in some cases, the microlens array 26 can be implemented to provide a more uniform light beam 30. In some cases, microlenses or microlens array 26 may be operated so that light beams 30 exiting the microlenses or microlens array are substantially perpendicular to the surface of the OLED display. This feature may help reduce the amount of light that may be reflected by OLED screen 12 that strikes light sensor 24, thereby reducing optical crosstalk.

[0025] FIG. 3A to FIG. 3C 1 shows further details of the proximity sensor module 14 according to some embodiments. In some cases, the microlens array 26 covers approximately 480 μm directly above the emitter 22. 2 For other embodiments, different areas of microlens array 26 may be appropriate. Figure 4 A specific example of a microlens array 26 is shown, which includes circular microlenses 26A arranged at a pitch d1. In some cases, the pitch d1 is equal to 95 μm, but for other embodiments, different values ​​may be appropriate. Figure 5 Another example of a microlens array 26 is shown, which includes hexagonal microlenses 26B arranged at a pitch d2. In some cases, the pitch d2 is equal to 95 μm, but for other embodiments, different values ​​may be appropriate.

[0026] In some embodiments, the component for reducing the maximum energy density includes an optical diffuser instead of or in addition to a microlens or microlens array.

[0027] As in Figure 2 as well as FIG. 3A to FIG. 3CAs further shown in FIG. 1 , module 14 may also include an optical element 32 (such as a lens) above light sensor 24 and operable to direct incoming light (e.g., light reflected by a target object) toward the light sensing element of sensor 24. Providing such an optical element 32 may help improve sensitivity and noise suppression.

[0028] In some embodiments, as in Figure 6 As shown in the example of , multiple light emitters 22 are provided in the proximity sensor module 114 and are positioned relative to each other so as to disperse the resulting light spot incident on the OLED screen 12. In this case, each of the emitters 22 can be operated to produce a lower maximum energy density, so that the density of IR or NIR light incident on the back of the OLED screen 12 is reduced while maintaining the total energy to achieve satisfactory proximity sensing performance. For example, in some cases, instead of applying a current of 15mA to each VCSEL light emitter 22, a current of 5mA is applied. For other embodiments, different current values ​​may be appropriate. In some cases, 3mW / mm 2 The maximum optical power density is incident on the back of the OLED screen 12. In some cases, each VCSEL is operated to produce a maximum power level of about 2.0 mW and preferably a maximum power level of about 1.5 mW (corresponding to a drive current of about 2 mA to 3 mA for some VCSELs) to prevent screen distortion. In addition, although Figure 6 The example of illustrative embodiments shows three emitters 22, but other embodiments may use only two emitters or may use more than three emitters. Regardless, multiple emitters 22 are used to provide sufficient optical energy for proximity sensing without concentrating the light energy in the same area so as to adversely affect the OLED screen pixels (e.g., to avoid creating light spots on the OLED screen that are visible to the human eye, or to reduce distortion that may otherwise occur).

[0029] Figure 7 Shows the combination Figure 2 3. The proximity sensor module 214 includes a Figures 2 to 5 The described components 26 for reducing the maximum energy density (e.g., microlenses, microlens arrays, or diffusers) and the like in combination Figure 6 A plurality of light emitters 22 are depicted.

[0030] The designs of smart phones and other host computing devices referenced in this disclosure may include one or more processors, one or more memories (e.g., RAM), storage (e.g., disk or flash memory), a user interface (e.g., which may include a keypad, a TFT LCD or OLED display screen, a touch or other gesture sensor, a camera or other optical sensor, a compass sensor, a 3D magnetometer, a 3-axis accelerometer, a 3-axis gyroscope, one or more microphones, etc., and software instructions for providing a graphical user interface), interconnects (e.g., a bus) between these elements, and an interface for communicating with other devices (which may be wireless (such as GSM, 3G, 4G, CDMA, WiFi, WiMax, Zigbee or Bluetooth) and / or wired (such as through an Ethernet local area network, a T-1 Internet connection, etc.)).

[0031] Various aspects of the subject matter and functional operations described in this specification may be implemented in digital electronic circuits or computer software, firmware or hardware including the structures disclosed in this specification and their structural equivalents, or in a combination of one or more thereof. Therefore, aspects of the subject matter described in this specification may be implemented as one or more computer program products, that is, one or more computer program instruction modules encoded on a computer-readable medium for execution by a data processing device or for controlling the operation of a data processing device. The computer-readable medium may be a machine-readable storage device, a machine-readable storage substrate, a memory device, a material composition that implements a machine-readable propagation signal, or a combination of one or more thereof. In addition to hardware, the device may also include code that creates an execution environment for the computer program in question, for example, code that constitutes processor firmware.

[0032] A computer program (also referred to as a program, software, software application, script, or code) may be written in any form of programming language, including compiled or interpreted languages, and may be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program may be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files storing one or more modules, subroutines, or code portions). A computer program may be deployed to execute on one computer, or on multiple computers located at one location or distributed across multiple locations and interconnected by a communication network.

[0033] The processes and logic flows described in this specification may be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows may also be performed by, and the apparatus may be implemented as, special purpose logic circuitry, such as an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0034] By way of example, processors suitable for executing a computer program include both general-purpose and special-purpose microprocessors, and any one or more processors of any kind of digital computer. In general, the processor will receive instructions and data from a read-only memory or a random access memory, or both. The essential elements of a computer are a processor for executing instructions and one or more memory devices for storing instructions and data. Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and memory devices, including by way of example: semiconductor memory devices (e.g., EPROM, EEPROM, and flash memory devices); magnetic disks (e.g., internal hard disks or removable disks); magneto-optical disks; and CD ROM and DVD-ROM disks. The processor and memory may be supplemented by or incorporated into special-purpose logic circuits.

[0035] Although this specification contains many details, these details should not be regarded as limitations on the invention or the scope of protection, but should be regarded as descriptions of features unique to specific embodiments of the invention. Certain features described in this specification in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any suitable sub-combination. In addition, although the features are described above as working in certain combinations and even initially claimed as such, one or more features from the claimed combination may be removed from the combination in some cases, and the claimed combination may be directed to a sub-combination or a variation of the sub-combination.

[0036] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desired results. In certain circumstances, multitasking and parallel processing may be advantageous.

[0037] A number of embodiments have been described. However, various modifications may be made without departing from the spirit and scope of the invention. Therefore, other embodiments are within the scope of the following claims.

Claims

1. A device comprising: Display screen; as well as An optical proximity sensor module is provided behind the display screen, and the optical proximity sensor module comprises: a plurality of light emitters operable to generate infrared or near infrared light for transmission through the display screen toward a target object and operable to generate an energy density such that a maximum energy density of light incident on a back side of the display screen is reduced while maintaining total energy to facilitate proximity sensing performance; and a light sensor operable to sense infrared or near infrared light reflected by the target object, The plurality of light emitters are capable of operating together to provide sufficient optical energy for proximity sensing, and the light emitters disperse the optical energy used for the proximity sensing, thereby reducing distortion of the display screen.

2. The device of claim 1, wherein the display screen is an OLED display screen.

3. The apparatus of claim 1 or 2, wherein the plurality of light emitters comprises a plurality of VCSELs, each of the plurality of VCSELs being operated to produce a maximum power level of 2.0 mW.

4. The apparatus of claim 1 or 2, wherein the plurality of light emitters comprises a plurality of VCSELs, each of the plurality of VCSELs being operated to produce a maximum power level of 1.5 mW.

5. The device according to claim 1 or 2, wherein the plurality of light emitters are configured to emit light at 3 mW / mm 2 or less light power density to illuminate the back side of the display screen.

6. A method comprising: causing each of a plurality of VCSELs in an optical proximity sensor module disposed behind a display screen to generate infrared or near-infrared light for transmission through the display screen toward a target object, and being operable to generate an energy density such that a maximum energy density of light incident on a back side of the display screen is reduced while maintaining total energy to facilitate proximity sensing performance; sensing infrared or near-infrared light reflected by the target object; as well as Signals corresponding to the sensed infrared or near infrared light are processed for proximity sensing.

7. The method of claim 6, wherein each of the plurality of VCSELs produces a maximum power level of 2.0 mW.

8. The method of claim 6 or 7, comprising applying a drive current in the range of 2 mA to 3 mA to each of the plurality of VCSELs.

Images