1. Technical Field
The technical field relates to a visible light communication transceiver.
2. Background
Along with increasing popularity of light-emitting diode (LED) lighting, a high-speed modulation characteristic of the LED results in a fact that application potential of the LED in visible light communications (VLC) has drawn widespread attentions. A conventional VLC system can only provide about a Kb/s level unidirectional (or downstream) transmission communication.
The VLC system has advantages of short transmission distance, smaller cell coverage range, information security, no EMI interference, no need of a frequency band usage license, and suitable for providing indoor lighting, etc. Therefore, how to provide a bidirectional and high-speed (for example, greater than 100 Mb/s) VLC system is a particularly urgent research topic.
One of exemplary embodiments of the disclosure provides a visible light communication (VLC) transceiver including a substrate, a lens module and a plurality of channel units. The lens module is disposed on an optical path of the channel units. The channel units are disposed on the substrate in an array. The channel units respectively provide different bidirectional communication channels, where each of the channel units respectively includes at least one LED, the LED serves as a visible light emitter in an illumination time slot, and the LED serves as a visible light receiver in a dark time slot.
In order to make the aforementioned and other features and advantages of the disclosure comprehensible, several exemplary embodiments accompanied with figures are described in detail below.
The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure.
The second VLC transceiver 22 can convert the VLC signal of the first VLC transceiver 12 into an electric signal, and then outputs the electric signal to the communication modulation circuit 21. The communication modulation circuit 21 of the second electronic device 20 can demodulate the electric signal to obtain transmission data from the first electronic device 10.
According to the actual product design requirement, the communication channel between the first VLC transceiver 12 and the second VLC transceiver 22 can be a unidirectional communication channel or a bi-directional communication channel. Here, it is assumed that the communication channel between the first VLC transceiver 12 and the second VLC transceiver 22 is a unidirectional communication channel. The first VLC transceiver 12 includes a VLC chip 121, a lens module 122 and a lens actuation module 123. The VLC chip 121 has at least one upstream channel unit for providing at least one upstream channel, where the upstream channel unit includes at least one visible light emitter. According to the actual product design requirement, the visible light emitter includes a light-emitting diode (LED), a light emitter or other visible light-emitting devices.
The lens actuation module 123 is coupled to the lens module 122. The lens module 122 is disposed on an optical path of the VLC chip 121. The lens actuation module 123 can adjust a position, an optical axis direction or a focal length of the lens module 122. The visible light emitter of the VLC chip 121 is driven by the communication modulation circuit 11 to emit the VLC signal. The VLC signal is transmitted to the second VLC transceiver 22 through the lens module 122.
The second VLC transceiver 22 includes a VLC chip 221, a lens module 222 and a lens actuation module 223. The VLC chip 221 has a downstream channel array, where the downstream channel array includes a plurality of downstream channel units configured to respectively provide different downstream channels (input channels), and each of the downstream channel units respectively includes a visible light receiver. The visible light receivers include photodiodes, photon detectors or other visible light sensing elements. The VLC signal of the first VLC transceiver 12 is received by the VLC chip 221 through the lens module 222. The VLC chip 221 converts the VLC signal of the first VLC transceiver 12 into an electric signal, and outputs the electric signal to the communication modulation circuit 21. A detailed implementation of the VLC chip 221 is described later.
On the other hand, the lens actuation module 223 is coupled to the lens module 222 and the VLC chip 221. The lens actuation module 223 can actively control/adjust a position, an optical axis direction or a focal length of the lens module 222 according to receiving situations of the visible light receivers on the VLC chip 221. A method that the lens actuation module 223 (or 123) drives the lens module 222 (or 122) is determined according to the actual product design requirement. For example, the method that the lens actuation module 223 (or 123) drives the lens module 222 (or 122) can be similar to a driving method of an optical pickup head in an optical disk drive. For another example, the method that the lens actuation module 223 (or 123) drives the lens module 222 (or 122) can be similar to a driving method of a lens module in a digital camera.
In another embodiment, under permission of an application environment/design conditions, the above lens actuation module 223 (or 123) can be omitted, and the lens module 222 (or 122) is fixed to an optimal position on the optical path. In other embodiments, in consideration of the actual product design requirement, the lens actuation module 223 (or 123) and the lens module 222 (or 122) can be omitted.
In the aforementioned exemplary embodiment, the VLC system is assumed to have the unidirectional communication. However, the disclosure is not limited thereto. For example, the VLC chip 221 of the second VLC transceiver 22 further includes an upstream channel array, and the upstream channel array includes a plurality of second upstream channel units for respectively providing different upstream channels (output channels). Each of the second upstream channel units respectively includes at least one visible light emitter. The visible light emitter includes an LED, a light emitter or other visible light-emitting elements. The lens module 222 is further disposed on an optical path of the second upstream channel units of the VLC chip 221. Implementation of the first VLC transceiver 12 is similar to that of the second VLC transceiver 22, so that the VLC system of
The visible light emitters LE include LEDs or other visible light-emitting elements. The visible light emitters LE are used for visible light signal uplink. The visible light receivers PD include photodiodes, photon detectors or other visible light sensing elements. The visible light receivers PD are used for visible light signal downlink. In a same channel unit, for example, in the channel unit CH(1,1), the visible light emitters LE can be connected in series, in parallel and/or independently connected to the communication modulation circuit 21 according to a design requirement. Namely, according to the design requirement, the communication modulation circuit 21 can simultaneously light all of/a part of the visible light emitters LE in the same channel unit to increase luminous flux. Alternatively, the communication modulation circuit 21 can independently drive all of/a part of the visible light emitters LE in the same channel unit to increase signal modulation degree of freedom. For example, the channel units of the VLC chip 221 can enhance communication bandwidth by using modulation technology such as spatial multiplexing or time multiplexing. Moreover, the second VLC transceiver 22 can implement multi-channel simultaneous communication in a parallel communication structure through a plurality of the channel units, so as to improve a communication speed.
For example, in another exemplary embodiment, the channel units shown in
Each of the visible light emitters LE illustrated in
Moreover, the light sensing unit resetting line PDR determines to command driving circuits 620 of a specific row of the channel units to drive the visible light receivers PD to a high voltage level. The reset visible light receivers PD can convert light signals into electric signals. The light sensing unit selection line PDS selects the driving circuits 620 of a specific column of channel units, and reads the electric signal converted by the visible light receiver PD through the selected driving circuit 620.
On the other hand, when the light sensing unit resetting line PDR is in the high voltage level, the transistor 621 is turned on, and the voltage source VDD is input to a cathode of the visible light receiver PD to form a reverse bias. Now, the transistor 622 is also turned on, and the voltage of the voltage source VDD is input to the transistor 623. When the light sensing unit resetting line PDR is in the high voltage level, if the light sensing unit selection line PDS is also in the high voltage level, a reading terminal 70 reads the electric signal from the voltage source VDD and is in the high voltage level. Then, when the light sensing unit resetting line PDR is transited to the low voltage level and the light sensing unit selection line PDS is still in the high voltage level, the transistor 621 is turned off and the transistor 623 is maintained to be turned on. When the transistor 621 is just turned off, the cathode of the visible light receiver PD is still in the high voltage level, and the reading terminal 70 still reads the voltage from the voltage source VDD. However, during a process that a visible light irradiates the visible light receiver PD, a cathode voltage of the visible light receiver PD gradually decreases. Now, the transistor 622 can be regarded as an amplifier capable of amplifying the cathode voltage of the visible light receiver PD, so that when the cathode voltage of the visible light receiver PD gradually decreases, the voltage read by the reading terminal 70 also gradually decreases. Then, when the light sensing unit selection line PDS is in the low voltage level, the transistor 623 is turned off, and now the voltage at the reading terminal 70 also drops to the low voltage level.
A decreasing speed of the cathode voltage of the visible light receiver PD relates to a brightness of the light irradiating the visible light receiver PD. The larger the intensity of the light detected by the visible light receiver PD is, the larger a photocurrent is, and the faster the cathode voltage decreases, and the faster the voltage of the reading terminal 70 decreases. A controller and/or the communication modulation circuit 21 measures a voltage decreasing speed (for example, an absolute value of a decreasing slope) of the reading terminal 70, or measures the voltage of the reading terminal 70 at a moment before the light sensing unit selection line PDS is switched from the high voltage level to the low voltage level, and converts the intensity of the light detected by the visible light receiver PD into a voltage signal.
The controller 820 is coupled to the channel units (for example, CH(1,1), CH(1,2) and CH(2,1), etc.) of the VLC chip 221 and the lens actuation module 223. According to receiving situations (for example, a spatial uniformity of an array signal of the visible light receivers PD) of the visible light receivers PD in the channels, the controller 820 controls the lens actuation module 223 to adjust the position, the optical axis direction and/or the focal length of the lens module 222, so that the channel units of the VLC chip 221 obtain maximum transmission/reception signals. Namely, the lens module 222 can actively track a signal intensity of the light receiver array of the VLC chip 221 to improve the signal quality of high-speed multiplexing communication.
A light signal 1001 of the VLC chip 121 is transmitted to the second electronic device 20 through the lens module 122. The light signal 1001 is transmitted through the lens module 222, and is received by the downstream channel array of the VLC chip 221. The electric signal of the downstream channel array is fed into the controller, and the controller transmits a downstream signal to the communication modulation circuit 21. Moreover, the controller performs an operation similar as that shown in
In the aforementioned embodiment, each of the channel units has the visible light emitters LE and the visible light receiver PD, though the disclosure is not limited thereto. For example,
A cathode of the DC-LED 1101 and an anode of the DC-LED 1102 are coupled to the controller 820. An anode of the DC-LED 1103 and a cathode of the DC-LED 1105 are coupled to a cathode of the DC-LED 1102. An anode of the DC-LED 1104 and a cathode of the DC-LED 1103 are coupled to an anode of the DC-LED 1101. An anode of the DC-LED 1105 and a cathode of the DC-LED 1104 are coupled to the controller 820. The controller 820 is driven by an AC sine wave power 1130 to output an AC signal 1130′ to drive the LEDs shown in
When the AC signal 1130′ has a positive voltage, the DC-LEDs 1102, 1103 and 1104 are forward biased, and the DC-LEDs 1101 and 1105 are reverse biased. During such period, only when the AC signal 1130′ is greater than a threshold voltage Vth1 of the DC-LED, the DC-LEDs 1102, 1103 and 1104 emit light, so that a light-emitting period of the DC-LEDs 1102, 1103 and 1104 is referred to as an illumination time slot IT. In the illumination time slot IT, the DC-LEDs 1102, 1103 and 1104 can serve as the visible light emitters LE, and the controller 820 loads upstream data to the AC signal 1130′ in the illumination time slot IT. In the illumination time slot IT, the controller 820 does not extract downstream data of the AC signal 1130′. When the AC signal 1130′ is smaller than the threshold voltage Vth1 of the DC-LED and is greater than 0V, none of the DC-LEDs emit light, and a none light-emitting period of the AC-LED is referred to as a dark time slot DT. In the dark time slot DT and when the AC signal 1130′ is greater than 0V, the reverse biased DC-LEDs 1101 and 1105 can serve as the visible light receivers PD, and the controller 820 can extract the downstream data of the AC signal 1130′ in the dark time slot DT. In the dark time slot DT, the controller 820 does not load the upstream data to the AC signal 1130′.
When the AC signal 1130′ has a negative voltage, the DC-LEDs 1105, 1103 and 1101 are forward biased, and the DC-LEDs 1102 and 1104 are reverse biased. During such period, only when the AC signal 1130′ is smaller than a negative threshold voltage Vth2 of the DC-LED, the DC-LEDs 1105, 1103 and 1101 emit light, so that a light-emitting period of the DC-LEDs 1105, 1103 and 1101 is referred to as the illumination time slot IT. In the illumination time slot IT, the DC-LEDs 1105, 1103 and 1101 can serve as the visible light emitters LE, and the controller 820 loads the upstream data to the AC signal 1130′ in the illumination time slot IT, and does not extract the downstream data of the AC signal 1130′. When the AC signal 1130′ is greater than the negative threshold voltage Vth2 of the DC-LED and is smaller than 0V, none of the DC-LEDs emit light. When the AC-LED is in the dark time slot DT and the AC signal 1130′ is smaller than 0V, the reverse biased DC-LEDs 1102 and 1104 can serve as the visible light receivers PD, and the controller 820 can extract the downstream data of the AC signal 1130′ in the dark time slot DT, and does not load the upstream data to the AC signal 1130′.
In other words, when an amplitude of the AC signal 1130′ approaches to zero, the dark time slot DT is detected through a zero crossing detector of the controller 820, and now the controller 820 stops loading signals to the light source circuit (e.g. the channel unit CH(1,1)), and starts to extract data signals in the light source circuit. According to such feature, in the illumination time slot IT, the AC-LED serves as the visible light emitter LE used for lighting and carrying communication signals, and in the dark time slot DT, the reverse biased LEDs in the AC-LED serve as the visible light receivers PD used for receiving signals. In this way, the same AC-LED device can serve as the visible light emitter LE and the visible light receiver PD by timing, so as to achieve an integrated communication transceiver. Under such structure, the DC-LEDs 1101-1105 can serve as the visible light receivers PD, and semiconductor epitaxial structures thereof can be optimally designed to improve photoelectric conversion efficiency of the light sensors.
For another example,
The DC-LEDs 1106 and 1107 alternately emit light under different bias directions. During a period that the AC signal 1130′ output by the controller 820 has the positive voltage to make the DC-LED 1107 bearing a forward bias and the DC-LED 1106 bearing a reverse bias, when the DC-LED 1107 is lighted (in the illumination time slot IT), it can serve as the visible light emitter LE (for lighting and signal communication), and now the controller 820 loads the upstream data to the AC signal 1130′ in the illumination time slot IT. During the period that the AC signal 1130′ has the positive voltage, in the dark time slot DT, the DC-LED 1106 bears the reverse bias to serve as the visible light receiver PD (for receiving the light signal). Conversely, the situation in a period that the AC signal 1130′ output by the controller 820 has the negative voltage to make the DC-LED 1106 bearing a forward bias and the DC-LED 1107 bearing a reverse bias can be deduced by analogy. Therefore, the same AC-LED device can serve as the visible light emitter LE and the visible light receiver PD by timing configuration, so as to achieve the functionality of an integrated communication transceiver.
For another example,
The single string of LED (i.e. the DC-LED) shown in
In summary, in response to requirements of bandwidth and upload communication technology, the embodiments of the disclosure provide a bi-directional communication and high-speed VLC transceiver, in which an array of the visible light emitters LE and an array of the visible light receivers PD are integrated to form a single light signal transceiver chip, and the lens module focuses and projects the light signal onto the visible light receivers PD. The aforementioned embodiments satisfy demands of high bandwidth (greater than 10 MHz) and bi-directional communication structure (uplink+downlink) in development of VLC technology. In the single transceiver chip, the array of the visible light emitters LE can enhance communication bandwidth by using modulation technology such as spatial multiplexing or time multiplexing. Moreover, if the array of the visible light emitters LE is a multicolor array light source, the multicolor array light source can provide a wavelength multiplexing modulation to increase the communication bandwidth. In the aforementioned embodiment, the lens module capable of actively tracking a signal strength is integrated to ensure signal quality of high-speed multiplexing communication.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.
Number | Date | Country | Kind |
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101107501 | Mar 2012 | TW | national |
This application is a divisional application of U.S. application Ser. No. 13/445,916, filed on Apr. 13, 2012, now pending. The prior U.S. application claims the priority benefit of Taiwan application serial no. 101107501, filed on Mar. 6, 2012. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification.
Number | Date | Country | |
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Parent | 13445916 | Apr 2012 | US |
Child | 14983597 | US |