Patent Application
20160146938
This disclosure relates to a proximity sensor that employs multiple optical sensors.
Proximity sensors are employed to detect the presence or absence of an object that appears within a given distance of the sensor. In one example, a proximity sensor can detect when an object, such as a user's face, is within proximity of a cell phone. If user detection is determined, interface inputs on the phone can be disabled when the person is talking so that contact with the user's face does not inadvertently select an input while talking. Proximity sensors can utilize various electromagnetic properties such as light, acoustics, inductance, or capacitance to detect objects. Proximity sensors that utilize light typically employ a light emitting diode (LED) that emits light toward an object, which is reflected and then received by a single photodetector to detect the presence of the object. In some applications, the light must be transferred and reflected through a protective optically transparent covering, such as through the glass cover of a cell phone, for example.
This disclosure relates to a proximity sensor that employs multiple receiving sensors.
In one example, an apparatus includes a light source to generate source light through an optically transmissive medium to an object. A receiver includes a near zone light sensor and a far zone light sensor positioned on a substrate with the light source. The near zone light sensor is positioned on the substrate to, in response to the generated source light, receive reflected source light from the object and the optically transmissive medium. The far zone light sensor is positioned on the substrate to, in response to the source light, receive the reflected source light from the object and to receive a reduced quantity of the reflected source light from the optically transmissive medium compared to the near zone light sensor.
In another example, an apparatus includes a light source to generate source light through an optically transmissive medium to an object. A receiver includes a plurality of photodetectors, at least one of the plurality of photodetectors configured as a near zone light sensor and at least one of the plurality of photodetectors configured as a far zone light sensor. The plurality of photodetectors being positioned on a substrate with the light source, wherein the near zone light sensor is positioned on the substrate to receive reflected source light from the object and the optically transmissive medium. The far zone light sensor is positioned on the substrate to receive the reflected source light from the object and to receive a reduced quantity of the reflected source light reflected from a surface of the optically transmissive medium. A lens is positioned over the plurality of photodetectors to focus the source light received from the optically transmissive medium and the object on to the plurality of photodetectors. A photodetector selector switch device selectively activates a subset of the plurality of photodetectors corresponding to the near zone light sensor and the far zone light sensor such that the subset of photodectors is positioned under the lens to receive the focused source light.
In yet another example, a system includes a light source to generate source light through an optically transmissive medium to an object. A receiver includes a near zone light sensor and a far zone light sensor positioned on a substrate with the light source. The near zone light sensor is positioned on the substrate to receive reflected source light from the object and the optically transmissive medium and to provide a near sensor output signal in response to the received source light. The far zone light sensor is positioned on the substrate to receive the reflected source light from the object and to receive a reduced quantity of the reflected source light reflected from a surface of the optically transmissive medium and to provide a far sensor output signal in response to the received source light. A processor circuit detects presence of the object by comparing the near sensor output signal to a predetermined near zone threshold and comparing far sensor output signal to a predetermined far zone threshold. The presence of the object is detected if at least one of the near zone threshold or the far zone threshold is exceeded.
This disclosure relates to a proximity sensor that employs multiple receiving sensors. The proximity sensor can be provided as an apparatus to detect proximity of objects using light. The proximity sensor includes a light source such as a light emitting diode (LED), for example, to generate light through an optically transmissive medium (e.g., glass, plastic) to an object to be detected. As used herein, an optically transmissive medium can refer to any crystalline or amorphous medium that is optically transparent to at least the light transmitted by the light source of the proximity sensor. For the example of a cellular telephone, the optically transmissive medium can include the digitizer front glass that covers the liquid crystal display. A receiver in the proximity sensor includes multiple sensors that are positioned on a substrate to discriminate reflected light received from the object from light reflected by the transmissive medium.
The receiver can include a near zone light sensor and a far zone light sensor that are positioned on the substrate with the light source and are configured to detect light in the wavelength (e.g., a wavelength spectrum) emitted by the light source of the proximity sensor. The near zone light sensor can be positioned on the substrate to receive reflected light from the object and the transmissive medium. The near zone light sensor can have its output calibrated (e.g., above the level of the light reflected from the transmissive medium) to detect the presence of objects that are within a predetermined distance of the receiver. The far zone light sensor can be positioned on the substrate to receive the reflected light from the object and to receive a reduced quantity of the reflected light from the transmissive medium compared to the near zone sensor. The far zone light sensor can be positioned and/or configured such that substantially all of the reflected light from the transmissive medium in response to light from the light source is not received by the far zone sensor. As used herein, the term substantially as a modifier notes that the intended effect is to preclude receipt of the light reflected internally from the transmissive medium, although some trace amounts (e.g., about 5% or less) of the reflected light may be received. The far zone light sensor can detect the object's presence at further distances from the receiver than detected by the near zone sensor. By analyzing output from both the near and far zone light sensors, objects can be detected at varying distances from the proximity sensor while obviating the need to employ restrictive mechanical barriers to mitigate blind spots that can be caused by reflections received from the transmissive medium.
A receiver 150 in the proximity sensor 110 includes multiple sensors that are positioned on a substrate 160 to discriminate reflected light received from the near object 140 and far object 142 from light reflected by the optically transmissive medium 130 (also referred to as transmissive medium) in response to the light emitted by the source 120. As used herein, the term substrate can include a semiconductor substrate, a printed circuit board (PCB) acting as a substrate, or a combination of an integrated circuit substrate and a PCB substrate. The receiver 150 can include a near zone light sensor 170 and a far zone light sensor 180 that are positioned on the substrate 160 with the light source 120. The near zone light sensor 170 can be positioned on the substrate 160 to receive reflected light from the near object 140 and the transmissive medium 130 whereas the far zone light sensor 180 is positioned on the substrate to receive reflected light from the far object 142. Each sensor 170 and 180 includes one or more optical detectors that provide a corresponding detector output signal in response to detect light (e.g., reflected from the transmissive medium and/or an external object) in the wavelength emitted by the light source 120.
A processor circuit 190 can be operatively coupled to the substrate 160 to process output signals from the near zone light sensor 170 and the far zone light sensor 180. By way of example, the processor circuit 190 can include an analog digital converter (A/D) (not shown) to digitize outputs from the sensors 170 and 180. The processor circuit 190 can also include a processor (not shown) and memory (not shown) to process output from the A/D. The processor circuit 190 can compare outputs from the sensors 170 and 180 to predetermined thresholds to determine the presence of the object 140 within a predetermined distance to an external surface of the transmissive medium 130. For instance, the processor circuit 190 can determine that the object 140/142 is within the predetermined distance based upon one or both of the sensors 170 and 180 having its output above the predetermined thresholds. The thresholds can be fixed or adjustable in response to a user input. As used herein, the term “circuit” can include a collection of active and/or passive elements that perform a circuit function such as the proximity sensor 110 or the processor circuit 190, for example. The term circuit can also include an integrated circuit where all the circuit elements are fabricated on a common substrate, for example.
Output signals from the near zone light sensor 170 can be calibrated by the processor circuit 190 to provide an operating range that allows light to be received above the level of the light reflected from the transmissive medium 130 as to enable detecting the presence of near objects 140 that are closer to the receiver 150. For example, if no object 140 is present, the light reflected from the transmissive medium 130 can be stored as a baseline digital value by the processor circuit 190, for example. Detected light from the near zone light sensor 170 coming from the near object 140 above the baseline value can then be considered a detection of the near object 140 with the value above the baseline indicating a relative proximity of the object to the receiver. Thus, the predetermined threshold for the near zone sensor 170 can be set in the processing circuit 190 to above the baseline value, such that by exceeding the baseline by the established amount the presence of an object within the predetermined distance from the receiver (or exterior surface of the transmissive medium 130) can be detected.
The far zone light sensor 180 can be positioned on the substrate 160 to receive a reduced quantity of the reflected light from the transmissive medium 130 than received by the near zone light sensor. By virtue of spatial positioning on the substrate 160 (e.g., far zone sensor positioned further from light source on the substrate than near zone sensor), substantially none of the reflected light from the transmissive medium 130 is received by the far zone light sensor 180. That is, the far zone light sensor 180 is positioned and/or configured to receive substantially only light reflected from the far object 142 in response to reflected light emitted from the source 130 (also referred to as reflected source light). Accordingly, the far zone light sensor 180 can detect the far object's presence at further distances from the receiver 150 than detected by the near zone light sensor 170. The processor circuit 190 can compare output of the far zone light sensor 180 to a predetermined threshold set for the far zone sensor. By analyzing output from both the near zone light sensor 170 and far zone light sensor 180, objects 140/142 can be detected at varying distances with respect to predetermined threshold values set for each sensor while obviating the need to employ restrictive mechanical barriers to mitigate blind spots that can be caused by reflections received from the transmissive medium 130.
As disclosed herein with respect to
In another example, reflected light from the transmissive medium 130 can be reduced at the far zone light sensor 180 by utilizing a focusing lens and/or pin hole aperture in a housing of the sensor to restrict light reflected from a surface (e.g., internal or external surface) of the transmissive medium 130 from reaching the far zone light sensor 180. Several example embodiments of the far zone sensor are disclosed herein with respect to
As a further example, distance of the object 140/142 can be determined by comparing received photodetector signal values between photodetectors of the respective near zone sensor 170 and the far zone sensor 180. For example, photodetector arrays can be employed where each detector in the array receives a slightly different angle of reflected light from the object 140/142, where analyzing output (e.g., A/D values) from the different detectors in the array can be utilized to determine how far the object 140/142 is from the receiver 150.
By utilizing multiple receiving sensors in the system 100, various complexities associated with conventional single photodetector systems can be mitigated. For instance, conventional single photodetector systems have certain complexities that must be considered when receiving the reflected light. For example, as the light is generated from the LED though glass, reflections from the glass can also be picked up by the single photodetector which can be confused with signal detected from an object. At certain distances between the object to be detected and the photodetector, blind spots can occur where it cannot be determined whether or not the object is detected or merely reflections detected from the glass. One conventional solution to this problem is to employ opto-mechanical barriers in the proximity detector to guide both the LED emission pattern from the LED and the receiving field of view of the photodetector to mitigate blind spots. Such barriers add expense to the proximity sensor and require sub-millimeter positioning during manufacturing which adds further expense to the sensor.
Each of the near zone light sensor 220 and the far zone light sensor 210 can include one or more photodetectors 260 and 270, respectively to detect light reflected from the object and/or from the transmissive medium in response to light from the source 230, as described above. If multiple photodetectors are employed in the sensors 260 or 270, different threshold values can be set and analyzed for each of the respective photodetectors. In some examples, the far zone light sensor 210 can be configured with photodetectors 270 that have higher sensitivity to detect low levels of illumination, such as corresponding to objects at greater distances from the exterior surface of the transmissive medium, than the sensitivity of the near zone sensor 220. In other examples, the sensitivity level of the photodetectors 260 in the near zone light sensor 220 and the far zone light sensor 210 can be configured substantially the same. If the light source 230 is in the visible spectrum, then the photodetectors 260 and 270 would be selected for operation in the visible spectrum. If the light source 230 generates light in the infrared or UV spectrum, for example, then the photodetectors 260 and 270 would be selected for operation in the infrared or UV spectrum, respectively.
By utilizing a system approach, and employing multiple sensors 710 and 750, and suitable optical structures 720 and 780, optical signals reflected from the transmissive medium 740 and from the object 730 can be spatially separated and discriminated by the sensors 710 and 750 to achieve desirable sensor performance without the use of mechanical barriers external to the sensing apparatus. In this example, the lens 780 over the LED source 760 and lens 720 over the far zone sensor 710 collimate both the LED beam, and the field of view of the sensor 710. This prevents substantially any light reflecting from the surface (interior or exterior) of the transmissive medium 740 from entering the field of view and being detected by the far zone light sensor 710. Thus, the system can sense objects far away, which will have small reflected signals, without being encumbered by substantial internal reflections from the transmissive medium 740 in response to the light generated by the source 760.
If only a single sensor were employed as in conventional systems, a blind zone may occur when the object is at closer distances. To detect objects within the blind zone, the near zone light sensor 750 is employed. Thus, the near zone light sensor 750 is used for sensing detection the object 730 when closer to the exterior surface of the transmissive medium 740 hence the reflected optical signal from the object will be strong. The near zone sensor 750 will also receive additional reflected light from the transmissive medium, but the object 730 can still be detected based on a calibration procedure (e.g., as described above with respect to
The detector array 810 and switch device 820 can be included with an apparatus that includes a light source to generate light through a transmissive medium to an object, such as disclosed herein with respect to
In the example of
What have been described above are examples. It is, of course, not possible to describe every conceivable combination of components or methodologies, but one of ordinary skill in the art will recognize that many further combinations and permutations are possible. Accordingly, the disclosure is intended to embrace all such alterations, modifications, and variations that fall within the scope of this application, including the appended claims. As used herein, the term “includes” means includes but not limited to, the term “including” means including but not limited to. The term “based on” means based at least in part on. Additionally, where the disclosure or claims recite “a,” “an,” “a first,” or “another” element, or the equivalent thereof, it should be interpreted to include one or more than one such element, neither requiring nor excluding two or more such elements.
