Patent Application
20140014839
The present invention generally relates to a sensor design based on light sensing, and more specifically to a sensor design based on light sensing with light detection circuit for ambient light sensing, proximity sensing, object presence detection and gesture recognition applications. The invention is also applicable to a host device which uses such sensor for achieving one or multiple of the functions, including ambient light sensing, proximity sensing, object presence detector, and/or gesture recognition.
Light sensing technologies are widely used in many applications. For example, ambient light sensors (ALS) can be used in laptop PCs and cell phones to sense the ambient lighting levels and to automatically adjust the backlight of the LCD screen to extend the battery life. Light sensors are also applied to measuring spatial distance or position. For example, proximity sensor is often found in mobile devices. Conventionally proximity sensors can be realized through different implementations, such as, inductive sensor, capacitive sensor, magnetic sensors and photoelectric sensors, wherein photoelectric sensors based on light sensing is gaining popularity. Other important applications, such as, object presence detection and gesture recognition sensing have also attracted much attention.
On the other hand, as smart devices become ubiquitous, more and more sensors are included in these smart devices to enrich the human device interaction. Therefore, a light sensor with multiple functions shows promising utility applied to the mobile devices and smart appliances.
The primary object of the present invention is to provide a sensor design based on light sensing technologies and light detection circuit for ambient light sensing, proximity sensing, object presence detection and gesture recognition capabilities.
To achieve the objective, the present invention provides a sensor comprised of a visible light photodiode an IR photodiode, an amplifier, an auto-gain control (AGC), an A/D converter (ADC), a digital filter, a multiplexer, a timing controller, a temperature sensor, a voltage reference, an oscillator, an IR_LED driver for driving n IR LEDs, a control register, a data register, an I2C interface and an interrupt interface. Both the visible light photodiode and the IR photodiode convert the photons into the electrons. The electrons are converted into voltage by the amplifier. The timing controller sets the integration time which the amplifier is activated. The amplifier gain is programmable by shorting the feedback capacitor partially. The ADC converts the amplified analog signal into digital count out. The digital count out is sent to digital filter and compute for signal that is related to ambient light Lux level, distance or gesture. The digital filter receives outputs from ADC, and outputs to the multiplexer. The multiplexer receives outputs from ADC and digital filter, and outputs to data register. The temperature sensor is for sensing temperature and outputs to both digital filter and multiplexer. The IR driver drives n IR LEDs IR_LED0-IR_LEDn. The control register set the timing controller. The data register receives output from the multiplexer. The I2C interface is connected to serial clock line (SCL) and serial data lines (SDA). The interrupt interface outputs to interrupt bus (INTB). SCL, SDA and INTB are then all connected externally to a host.
The foregoing and other objects, features, aspects and advantages of the present invention will become better understood from a careful reading of a detailed description provided herein below with appropriate reference to the accompanying drawings.
The present invention can be understood in more detail by reading the subsequent detailed description in conjunction with the examples and references made to the accompanying drawings, wherein:
The function of each of the aforementioned elements is described as follows. Visible light sensor 101 is for receiving the visible light in the ambience, and IR sensor 102 is for receiving the IR light emitted by the IR LEDs and reflected by the object. It is worth noting that IR sensor is associated with pixel 0, and visible light sensor 101 is associated with pixel 1. Amplifier 103 translates the sensed light into analog signals and then amplifies the signal through gain selection. AGC 104 adjusts appropriate integration time and gain as the settings to the sensor operation according to the luminance of the sensed light. At least an ADC 105 is included in the present invention to convert the analog signal into digital signal, and the converted digital signal is fed to digital filter 106 for filtering and to multiplexer 107, respectively. Multiplexer 107 selects between the filtered digital signal from digital filter 106 and unfiltered digital signal from ADC 105 directly, and outputs the selected digital signal to data register 114 for storage. Timing controller 108 is responsible for the overall timing sequence control for the entire sensor. Temperature sensor 109 is for sensing the temperature, voltage reference 110 provides a bias voltage to the part of analog circuit of the sensor, and oscillator 111 is the clock source to the entire sensor. IR_LED driver 112 is for driving the n IR LEDs, labeled IR_LED0-IR_LEDn respectively. Control register 113 is for storing instruction set and data register 114 is for storing data resulted from measurement, respectively. I2C interface 115 is for transmitting and receiving instructions and data from a host machine, such as, a PC mobile device, and thus is interfacing with external serial clock line and serial data lines respectively. Interrupt interface 116 is for interrupting the aforementioned host for informing the status of the sensor. The results and measurements of light sensing by the sensor of the present invention is then further utilized and/or displayed on host.
To achieve the objectives of performing ambient light sensing (ALS), proximity sensing (PS), object position detection sensing (OPDS) and gesture recognition sensing (GRS) respectively, the sensor of the present invention operates differently. To perform ALS, the sensor uses visible light sensor 101 to sense the luminance of the visible light in the ambience. To perform PS, the sensor drives one or more IR LEDs to emit IR. The emitted is then reflected by an object and received by IR sensor 102 for further computing the proximity of the object. To perform OPDS, the sensor drives the n IR LEDs arranged on the X-Y plane to emit IR sequentially. The sequentially emitted IR is then reflected by an object and received by IR sensor 102 at different points of time. The sensed IR at different points of time is then utilized by the aforementioned host to obtain a corresponding position of the object on the X-Y plane. Similarly, to perform GRS, the sensor drives the n IR LEDs arranged in n-dimensional space to emit IR sequentially. The sequentially emitted IR is then reflected by an object and received by IR sensor 102 at different points of time. The sensed IR at different points of time is then utilized by the aforementioned host to obtain a corresponding position of the object in the n-dimensional space and determines, for example, the hand gesture. It is worth noting that because visible light sensor 101 is associated with pixel 1 while IR sensor is associated with pixel 0, ALS operation would require working with pixel 0 and pixel 1, but PS, OPDS and GRS works only with pixel 0. The details of the operation of the sensor based on light sensing are described as follows.
It is worth noting that in ALS, PS and OPDS/GRS processes, the result is written to the data register, and an interrupt can be sent to the host so that the host can read data from the data register through the SDA lines. The sensor can also define a threshold, and sends the interrupt signal to the host only when the result exceeds the defined threshold.
Although the present invention has been described with reference to the preferred embodiments, it will be understood that the invention is not limited to the details described thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.
