PATENT DOCUMENT

Publication Number: US-8076628-B2
Application Number: US-23838008-A
Country: US
Kind Code: B2

Title: Ambient light sensor with reduced sensitivity to noise from infrared sources

Abstract:
Systems and methods are provided for detecting ambient light with reduced sensitivity to infrared sources. An electronic device may include an infrared sensor, an ambient light sensor, a decoder, and a processor. The infrared sensor may detect an intensity of infrared light. The ambient light sensor may be configured to detect incident light and to generate an electronic signal indicative of an intensity of visible light. The decoder may be configured to receive the intensity of infrared light and to generate an intensity of decoded infrared light. The processor, which may be coupled to the decoder and the ambient light sensor, may be configured to substitute an alternate electronic signal for the electronic signal if the intensity of infrared light exceeds a threshold amount.

Claims:
1. An electronic device comprising:
 an infrared sensor configured to detect an intensity of infrared light; 
 an ambient light sensor configured to detect incident light, wherein the ambient light sensor is configured to generate an electronic signal indicative of an intensity of visible light; 
 a decoder configured to receive the intensity of infrared light and to generate an intensity of decoded infrared light; and 
 a processor coupled to the decoder and the ambient light sensor, wherein the processor is configured to substitute an alternate electronic signal for the electronic signal if the intensity of the decoded infrared light exceeds a threshold amount. 
 
     
     
       2. The device of  claim 1  further comprising:
 an infrared filter interposed between the infrared sensor and an infrared source, wherein the infrared filter transmits infrared light over near-infrared wavelengths. 
 
     
     
       3. The device of  claim 1  further comprising:
 a photopic filter interposed between the ambient light sensor and an ambient light source, wherein the photopic filter transmits incident light over visible wavelengths, wherein the photopic filter receives incident light transmitted by the infrared window. 
 
     
     
       4. The device of  claim 1 , wherein the alternate electronic signal is a previous electronic signal. 
     
     
       5. The device of  claim 4  further comprising:
 a sample-and-hold circuit for providing the previous electronic signal. 
 
     
     
       6. The device of  claim 1  further comprising:
 an illumination mechanism configured to respond to the electronic signal or the alternate electronic signal. 
 
     
     
       7. An ambient light sensor module comprising:
 an infrared filter for transmitting incident light over a band of near-infrared wavelengths; 
 an infrared sensor for receiving light transmitted by the infrared filter and for detecting an intensity of infrared light over near-infrared wavelengths; and 
 an ambient light sensor for detecting an intensity of visible light and for generating an electronic signal indicative of an intensity of ambient light, wherein the ambient light sensor is configured to modify the electronic signal based on the intensity of the infrared light. 
 
     
     
       8. An ambient light sensor module comprising:
 a first sensor for detecting an intensity of all light at substantially any wavelength; 
 a second sensor for detecting an intensity of infrared light over near-infrared wavelengths; and 
 
       infrared light over near-infrared wavelengths; and
 a light processing module coupled to the first sensor and the second sensor, wherein the light processing module is configured to determine an intensity of visible light based on a difference between the intensity of all light and the intensity of infrared light, and wherein the light processing module is configured to substitute an alternative intensity of visible light for the intensity of visible light if the intensity of infrared light exceeds a threshold amount. 
 
     
     
       9. The module of  claim 8  further comprising:
 a decoding module coupled to the second sensor and the light processing module, wherein the intensity of infrared light exceeds the threshold amount if the light processing module receives a blocking signal from the decoding module. 
 
     
     
       10. The module of  claim 9 , wherein the blocking signal is one of a carrier sense signal, decoded byte signal, and a decoded bit signal.

Description:
FIELD OF THE INVENTION 
     This invention relates to systems and methods for detecting ambient light and, more particularly, to detecting ambient light with reduced sensitivity to noise from infrared sources. 
     BACKGROUND OF THE DISCLOSURE 
     Some electronic devices, such as laptop computers and cellular telephones, may be equipped with an ambient light sensor to support a variety of control functions, such as to adjust keyboard backlighting or display brightness. Some electronic devices may also be equipped with an infrared sensor for receiving infrared signals from, for example, a remote control. Infrared signals intended for the infrared sensor may interfere with operation of the ambient light sensor and cause the device to operate improperly. Thus, an ambient light sensor is needed that can suppress noise from infrared sources. 
     SUMMARY OF THE DISCLOSURE 
     Some embodiments of the invention relate to an electronic device that may include an infrared sensor, an ambient light sensor, a decoder, and a processor. The infrared sensor may detect an intensity of infrared light. The ambient light sensor may be configured to detect incident light and to generate an electronic signal indicative of an intensity of visible light. The decoder may be configured to receive the intensity of infrared light and to generate an intensity of decoded infrared light. The processor, which may be coupled to the decoder and the ambient light sensor, may be configured to substitute an alternate electronic signal for the electronic signal if the intensity of infrared light exceeds a threshold amount. 
     Some embodiments of the invention relate an ambient light sensor module that may include an infrared filter, an infrared sensor, and an ambient light sensor. The infrared filter may transmit incident light over a band of near-infrared wavelengths and may substantially reflect incident light over visible wavelengths. The infrared sensor may receive light transmitted by the infrared filter and for detecting an intensity of infrared light over near-infrared wavelengths. The ambient light sensor may be configured to detect an intensity of visible light and to generate an electronic signal indicative of an intensity of ambient light. The ambient light sensor may be configured to modify the electronic signal based on the intensity of the infrared light. 
     Some embodiments of the invention relate to a method for controlling an electronic device that may include detecting an intensity of all light at substantially any wavelength, detecting an intensity of infrared light over near-infrared wavelengths, generating an electronic signal indicative of an intensity of ambient light based on a difference between the intensity of all light and the intensity of infrared light, and generating a control signal dependent on the electronic signal or, if the intensity of infrared light exceeds a threshold intensity, generating the control signal based on an alternate electronic signal. 
     Some embodiments of the invention relate an ambient light sensor module that may include a first sensor for detecting an intensity of all light at substantially any wavelength, a second sensor for detecting an intensity of infrared light over near-infrared wavelengths, and a light processing module coupled to the first sensor and the second sensor. The light processing module may be configured to determine an intensity of visible light based on a difference between the intensity of all light and the intensity of infrared light and to substitute an alternative intensity of visible light for the intensity of visible light if the intensity of infrared light exceeds a threshold amount. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects and features of the invention will become more apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which: 
         FIG. 1  is a functional block diagram of an electronic device with an ambient light sensor module according to some embodiments of the invention; 
         FIG. 2  is a schematic circuit diagram of an exemplary ambient light sensor (“ALS”) module according to some embodiments of the invention; 
         FIG. 3  is a schematic circuit diagram of an exemplary ALS module according to some embodiments of the invention; 
         FIG. 4  is a process diagram of an exemplary method for detecting light according to some embodiments of the invention; and 
         FIG. 5  is a process diagram of an exemplary method for detecting light according to some embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     Embodiments of the invention relate to systems and methods for sensing ambient light with reduced sensitivity to noise from infrared (“IR”) sources. 
     In the following discussion of illustrative embodiments, variations of the terms “coupled” or “in communication with” refer to, without limitation, any connection or coupling, either direct or indirect, between two or more elements whether physical, logical, electrical, or combinations thereof. As one skilled in the art will appreciate, inferred coupling (that is, where one element is coupled to another element by inference) includes direct and indirect coupling between two elements in the same manner as “coupled.” The terms “a,” “an,” and the singular forms of words shall be taken to include the plural form of the same words, such that the terms mean that one or more of something is provided. The terms “comprising,” “including,” and “having,” as used in the claims and specification herein, shall be considered as indicating an open group that may include other elements not specified. The terms “visible light,” “photopic light,” and “ambient light” are used interchangeably and generally refer to any light that can be detected by the human eye. Any reference to a particular wavelength includes wavelength bands that are “about” the stated wavelength and may be slightly longer or slightly shorter than the stated wavelength. The term “based on” is not exclusive and allows for being based on additional factors that may or may not be described. 
     It is to be understood that the figures and descriptions of the invention have been simplified to illustrate elements that are relevant for a clear understanding of the invention while eliminating, for purposes of clarity, other elements. For example, details relating to the translation, rather than generation, of control signals that cause an electronic device to respond in a certain way are not described herein. Similarly, certain details relating to sensor hardware, such as suitable infrared-sensitive semiconductor elements, are not described herein. A discussion of these elements is not provided because they are well known in the art and because they do not facilitate a better understanding of the invention. 
       FIG. 1  is a functional block diagram of an exemplary environment  5  for operating an electronic device  1  equipped with an ambient light sensor (ALS) module  10  capable of suppressing noise from infrared sources according to some embodiments of the invention. Electronic device  1  includes ALS module  10 , a processor  26 , a memory  28 , a display device  30 , and an input device  32  coupled to a bus  34 . ALS module  10  includes a window  12 , an IR filter  9 , a photopic filter  14 , an ambient light sensor  16 , and an IR sensor  18 . By placing ambient light sensor  16  alongside IR sensor  18 , ambient light sensor  16  may detect light not only from an ambient light source  13  but also IR light source  15 , as indicated by arrows  17  and  19   a , respectively. To reduce the sensitivity of ambient light sensor  16  to noise from IR light source  15 , ambient light sensor  16  may be informed by infrared sensor  18 , such as via an electronic signal  23  as shown. 
     Processor  26  may be a processor, an application-specific integrated circuit (“ASIC”), or any combination thereof. Processor  26  can, for example, control operation of electronic device  1 , accept data signals from ambient light sensor  16  and/or IR sensor  18  and generate control signals for transmission to display device  30  and/or user input device  32 . While electronic device  1  is illustrated with a single processor, those skilled in the art will appreciate that an electronic device may include multiple processors and/or co-processors. 
     Memory  28  can include read only memory (“ROM”), random access memory (“RAM”), solid-state memory, buffer memory, hard drive memory, any other memory known in the art or otherwise, or any combination thereof. In some embodiments, memory  28  can store sensor data generated by sensors  16  and  18 , and/or any other sensor used for sensing light. In other embodiments, memory  28  also can store information related to previously or historically detected values indicative of an intensity of light for retrieval by electronic device  1 . 
     Display device  30  may be configured to provide graphics (e.g., text, still images, and/or videos) to a user of device  1 . Display device  30  may be any display, such as a backlit liquid crystal display, that can be configured to adjust, for example, backlight brightness and/or contrast based on electrical control signals. Those skilled in the art will appreciate that display parameters may be controlled by varying the amount of power to display device  30 . 
     User input device  32  may be configured to allow a user to interact with electronic device  1 . User input device  32  may be any input device, such as a keypad, keyboard, touchpad, or clickwheel, having one or more buttons configured to produce electrical luminescence, such as by using light emitting diodes. Display device  30  and user input device  32  can be integrated into one component, such as a touchscreen display. 
     IR sensor  18  may be any sensor, such as a silicon diode, configured to detect IR light and generate an analog or digital electronic signal, such as electronic signal  25 , to be used in a control scheme, such as to cause electronic device  1  to respond to changing ambient light levels. IR sensor  18  may be integrated within the housing of an electronic device  1 , such as behind and optically aligned with window  12 . 
     Window  12  may be any medium or opening designed to substantially transmit visible light. Window  12  may be visible to a user of electronic device  1  so that the user can appropriately aim an IR remote control toward window  12 . 
     IR filter  9  may be any optical filter designed to substantially transmit incident light in a range of wavelengths in the near-IR region and to substantially reflect incident light over visible wavelengths. 
     Photopic filter  14  may be any optical filter designed to substantially transmit incident light over visible wavelengths and substantially reflect incident light over a band of near-IR wavelengths. In some embodiments, photopic filter  14  may be configured to simulate the photopic response of the human eye to relatively bright or dim light. 
     Ambient light sensor  16  may be any light sensitive element configured to detect variations in ambient light, either continuously or periodically, and to provide an output (e.g., electronic signal  21 ) to be used in a control scheme, such as to cause electronic device  1  to respond. For example, ambient light sensor  16  may be a light sensitive transistor, such as a phototransistor, configured to generate an electronic signal  21  indicative of the intensity of the ambient light detected by ambient light sensor  16 . Electronic signal  21  may be provided as an input into a logic circuit of electronic device  1 . The logic circuit, not shown, may be used to cause electronic device  1  to change one or more settings of electronic device  1  based on the intensity or brightness of the ambient light detected. Although only one ambient light sensor  16  is shown, ambient light data may be collected from two or more ambient light sensors positioned at different locations on electronic device  1 . Likewise, any number of IR sensors  18  may be used within the scope of the invention. 
     ALS module  10  may be configured to block a potentially erroneous value of electronic signal  21 , such as when an IR remote control is used in close proximity to window  12 , which may cause ambient light sensor  16  to overestimate the intensity of ambient light. In some embodiments, electronic device  1  may be configured to substitute an alternate value for electronic signal  21 , such as while a threshold intensity of IR signal is being detected by IR sensor  18 . The alternate value may be an intensity of visible light detected by ambient light sensor  16  before infrared sensor  18  detected the threshold intensity of infrared light. A sample-and-hold circuit may be configured to hold a level of the signal received by ambient light sensor  16  if IR sensor  18  receives a threshold IR signal. Likewise, the sample-and-hold circuit may be configured to disengage if IR sensor  18  receives an IR signal below the threshold intensity or if the circuit has stabilized. In some embodiments, a dual slope integration circuit may be used to offset or correct errors in the visible light output. 
       FIG. 2  is a schematic circuit diagram of an exemplary ALS module  200  according to some embodiments of the invention. ALS module  200  includes IR sensors  18   a  and  18   b , an all light sensor  208 , amplifiers  210 ,  210   a  and  210   b , analog-to-digital converters  212   a  and  212   b , an arithmetic logic unit (“ALU”)  214 , and a decoding unit  222 . All light sensor  208  may detect light at substantially any wavelength and may generate a signal  209 . Signal  209  may be amplified by amplifier  210   a  and sent to analog-to-digital converter  212   a , which may convert signal  209  into an electronic binary numerical value comprising an electronic signal  211 . 
     IR sensor  18   a  may detect IR light at near-IR wavelengths and may generate a signal  213 . Signal  213  may be amplified by amplifier  210   b  and sent to analog-to-digital converter  212   b , which may convert signal  213  into an electronic binary numerical value comprising an electronic signal  215 . ALU  214  may be configured to estimate an intensity of ambient light based on electronic signal  215  and electronic signal  211 . For example, ALU  214  may be configured to calculate a difference between signal  215  and signal  211  and then generate photopic light signal  21 . ALU  214  may also be configured to account for the presence of color filters, which may reflect visible light and cause all light sensor  208  to underestimate the intensity of ambient light. 
     IR sensor  18   b  may detect IR light at near-IR wavelengths and may generate a signal  217 . Signal  217  may be amplified by amplifier  210  and may be quantized by a quantizer  220 . Thereafter, signal  217  may be processed by a decoding device  222 . Decoding device  222  may be configured to output IR light signal  25  that estimates an intensity of IR light. 
     In some embodiments, circuit  200  periodically or continuously detects ambient light and produces a new value of signal  21  indicative of the intensity of ambient light. If, however, IR sensor  18   b  detects a threshold intensity of IR light, such as when an IR remote control is operated in close proximity to ALS module  10 , electronic signal  215  may be significantly larger than electronic signal  211 . This difference in magnitude may cause ALU  214  to output a potentially erroneous value of electronic signal  21 . Instead, ALU  214  may receive a blocking signal via electronic signal  23  from decoding unit  222  if the intensity of IR light exceeds a threshold amount. For example, if the intensity of IR light exceeds the threshold amount, electronic signal  23  may block ALU  214  from transmitting a potentially erroneous signal via electronic signal  21 . In some embodiments, circuit  200  may be configured to substitute an alternate value, such as a prior value of signal  21 , for the detected value. 
     Electronic signal  23  may include a carrier sense signal from received signal  217 . In some embodiments, decoding unit  222  may be configured to remove or separate the carrier signal from signal  217  and output a clean digital control signal  23  to ALU  214 . According to such an embodiment, clean digital control signal  23  may be determined by decoded 8-bit bytes or decoded bit frames. 
       FIG. 3  is a schematic circuit diagram of an exemplary ALS module  300  according to some embodiments of the invention. ALS module  300  is similar in many respects to ALS module  200  except that ALS module  300  uses one less diode. By combining ambient light circuit  202  and IR light circuit  204 , ALU  214  and decoding device  222  both receive infrared data generated by a single IR sensor  18 . Those skilled in the art will appreciate that, in embodiments like ALS module  300  that use one less diode may be used to achieve similar functionality at a reduced cost. Either ALS module  200  or ALS module  300  may be manufactured on a single chip. 
     Those skilled in the art will appreciate that amplifiers  210  and analog-to-digital converters  212  may be omitted from ambient light circuit  202  without departing from the invention. According to such an embodiment, ALU  214  may be configured to receive signals  209  and  213  directly. 
       FIG. 4  is a process diagram of an exemplary method  400  for controlling an electronic device according to some embodiments of the invention. Method  400  begins in step  402  as the electronic device detects an intensity of incident light at substantially any wavelength (i.e., “all light”). At step  404 , the electronic device may detect an intensity of infrared light over a band of near-infrared wavelengths. At step  406 , the electronic device may generate an electronic signal indicative of an intensity of ambient light, which may be derived from a difference between the detected intensity of all light and the detected intensity of infrared light. At step  408 , the electronic device may respond to the electronic signal generated at step  406 , such as by adjusting keyboard backlighting or adjusting display brightness. For example, an increase in ambient light may result in a proportional increase in backlight intensity. 
       FIG. 5  is a process diagram of an exemplary method  500  for controlling an electronic device according to some embodiments of the invention. Method  500  begins in step  502  as the electronic device detects an intensity of ambient light. For example, ALU  214  may calculate an intensity of ambient light based on a difference between an intensity of all light (electronic signal  211 ) and an intensity of infrared light (electronic signal  215 ). 
     In step  504 , the electronic device may determine whether a threshold intensity of infrared light has been detected. If the electronic device detects an intensity of infrared light below the threshold, the intensity of ambient light calculated in step  502  may be stored, in step  506 , and output, in step  508 . For example, ALU  214  may be informed by electronic signal  23  as to whether electronic signal  217  exceeds the threshold. If electronic signal  23  indicates that infrared sensor  18  detected an intensity of infrared light below the threshold amount, then the intensity of ambient light determined in step  502  may be stored, such as by using a store-and-hold circuit, and may be output in step  508 . In some embodiments, the absence of electronic signal  23  may indicate that the intensity of infrared light is below the threshold amount. 
     If the electronic device detects an intensity of infrared light above the threshold, the intensity of ambient light calculated in step  502  may be blocked in step  510 . For example, ALU  214  may block the intensity of ambient light determined in step  502  (based on electronic signals  211  and  215 ) from being output as electronic signal  21 . At step  512 , the electronic device may substitute the intensity of ambient light stored in step  506  for the intensity of ambient light determined in step  502 . For example, ALU  214  may be configured to substitute a previous value of electronic signal  21  if electronic signal  23  indicates that sensor  18  detected an intensity of infrared light above the threshold amount. The substitution of step  512  may continue as long as a threshold intensity of infrared light is being detected. 
     While the systems and methods are described with respect to controlling keyboard backlighting and display brightness, it should be noted that the invention is applicable to any illuminating mechanism equipped with a light emitting diode or any other light producing means that can be controlled to emit light with variable intensities. 
     The order of execution or performance of the methods illustrated and described herein is not essential, unless otherwise specified. That is, elements of the methods may be performed in any order, unless otherwise specified, and that the methods may include more or less elements than those disclosed herein. For example, it is contemplated that executing or performing a particular element before, contemporaneously with, or after another element is within the scope of the invention. 
     One of ordinary skill in the art should appreciate that the invention may take the form of an entirely hardware embodiment or an embodiment containing both hardware and software elements. In particular embodiments, such as those embodiments that relate to methods, the invention may be implemented in software including, but not limited to, firmware, resident software, and microcode. 
     One of ordinary skill in the art should also appreciate that the methods and systems of the application may be practiced in embodiments other than those described herein. It will be understood that the foregoing is only illustrative of the invention disclosed herein, and that various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention or inventions.

Metadata:
Filing Date: 20080925
Publication Date: 20111213
Grant Date: 20111213
Priority Date: 20080925
Inventors: MAHOWALD PETER H.
Assignee: APPLE INC
CPC Classifications: [{"code": "G01J1/1626", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/04", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01J1/32", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0407", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/029", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/1626", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/04", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01J1/0219", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/0407", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/029", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/0219", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/32", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/02", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 42036661