System, method, and apparatus for bi-directional infrared communication

An infrared (IR) communication device for audible sound communication over an infrared beam. The IR communication device includes an IR receiver, an IR transmitter, a speaker, and a microphone 210. The IR receiver receives the incoming IR beam. The IR transmitter 206 generates the IR output beam. A pair of IR communication devices form an IR communication system with a pair of IR communication channels. Simplex and full duplex IR communication may be provided over one or a pair of IR communication channels.

FIELD OF THE INVENTION

The invention relates generally to the field of wireless communication devices. Particularly, the invention relates to infrared (IR) communication devices.

BACKGROUND OF THE INVENTION

The electromagnetic spectrum has frequencies associated with it in which electromagnetic radiation may be radiated. The electromagnetic spectrum can be divided into frequency regions that exhibit common properties useful in science and technology. For example, the audible range of frequencies is approximately between 20 Hertz (Hz) to 20,000 Hz which humans can here. There is a radio frequency band of the electromagnetic spectrum which is allocated for radio, including cellular phones, and television communication systems. Electromagnetic radiation in the radio frequency bands tends to bend around, reflect off of and pass through objects, and thus, is favorable to communication systems. There is a narrow band referred to as the visible spectrum between 3.95×1014Hz to 7.90×1014Hz over which the radiant energy is visible to a human eye. The visible spectrum may divided into frequencies of color. Just below the visible spectrum is the infrared (IR) frequency spectrum which is in the range between 3×1011Hz to 4×1014Hz which is not visible to the human eye. More typically, the frequency of electromagnetic radiation in the IR frequency spectrum is expressed in wavelengths because of its light properties. In this case, the wavelength of light (λ) is proportional to the inverse of the frequency (f) and can be expressed in equation form as λ=C/f where C is the speed of light.

Infrared (IR) radiation having properties of light travels in a straight, or line-of-sight, path. IR radiation is blocked by opaque objects and typically reflects well off of only hard, mirror-like surfaces. Thus, electromagnetic radiation in the IR frequency spectrum, referred to as IR radiation, is not typically used in communication systems.

A communication system can be full duplex or simplex. A full duplex communication system provides constant bi-directional communication between users such as a telephone. A simplex communication system provides bi-directional communication between users but not at the same time. A user at each end selects whether he or she wants to talk or listen. A user at one end can not both listen and talk at the same time in a simplex communication system.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the invention, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, the invention may be practiced without these specific details. In other instances well known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the invention.

Referring toFIG. 1A, a bi-directional infrared communication system100is illustrated. Between a first IR communication device101A and a second IR communication device101B, are two infrared communication channels102A and102B. The IR communication channel102A transmits audible sounds or voice sounds from one IR communication device110A to another IR communication device101B. The IR communication channel102B transfers audible sounds or voice sounds from one IR communication device101B to another IR communication device101A.

Audible sounds and audible voice sounds are coupled into an IR communication device for communication over the IR communication channels. The terms audible voice, audible voice sounds, audible sound, voice sound, audible sound/voice input, audible sound/voice output, and reproduced sound is used herein to refer to the audible representation, which may be heard by humans, of both voice sounds initially generated by a voice of a human user and which are reproduced by a speaker, and other audible sounds, other that the voice of a human user, which is generated by mechanical or other means in space and coupled into the microphone, and other audible sounds which are reproduced by a speaker in space. The terms voice signal, voice transmit signal, voice receive signal, received voice signal, electrical transmit voice signal, and electrical received voice signal is used herein to refer to both voice sounds and other audible sounds communicated by electrical signals. The terms infrared voice signal and infrared signal is used herein to refer to the electrical signal representation of both voice sounds and other audible sounds communicated by infrared signals through space.

The IR communication device101A includes an IR receiver104A, an IR transmitter106A, a speaker108A, and a microphone110A. The IR communication device101B includes an IR receiver104B, an IR transmitter106B, a speaker108B, and a microphone110B. The combination of the infrared transmitter and the infrared receiver may also be referred to as an infrared transceiver.

In one direction of communication, a user120provides an audible sound or audible voice sound103A to the microphone110A. The audible sound or audible voice sound103A is converted or transduced by the microphone110A into an electrical signal which is coupled to the IR transmitter106A. The IR transmitter106A converts or transduces the electrical signal into an infrared voice signal which is transferred over the IR communication channel102A to the IR communication device101B. The IR receiver104B of the IR communication device101B receives the IR voice signal on the IR communication channel102A. The IR receiver104B of the IR communication device101B converts or transduces the IR voice signal into an electrical voice signal and couples it to the speaker108B. The speaker108B converts or transduces the electrical voice signal into an audible sound or audible voice sound105A for an end user122to hear.

In another direction of communication, the end user122talks and provides an audible sound or audible voice sound103B to the microphone110B of the IR communication device101B. The microphone110B converts or transduces the audible sound or audible voice sound into an electrical voice signal. The electrical voice signal is coupled to the IR transmitter106B. The IR transmitter106B converts or transduces the electrical voice signal into an infrared voice signal and transmits the IR voice signal over the IR communication channel102B to the IR communication device101A. The IR voice signal is received by the IR receiver104A and converted or transduced into an electrical voice signal which is supplied to the speaker108A. The speaker108A converts or transduces the electrical voice signal into an audible sound or audible voice sound105B which is provided to the end user120. The end user120may listen to the audible sound or audible voice sound105B using his/her hearing. In this manner, bi-directional voice communication can occur across the two IR communications channels102A and102B.

Referring now toFIG. 1B, IR communication devices101A,102B, and101C are illustrated. The IR communication devices101A,101B and101C are line of sight communication devices restricted to the spread of a transmitted IR signal and the angle of reception of the IR receiver. InFIG. 1B, IR communication devices101A and101B can communicate with each other over a line of sight112. IR communication device101B′ is a shifted or turned version of the IR communication device101B. InFIG. 1B, the IR communication device101C can communicate with the shifted position IR communication device101B′ to communicate over a line of sight114. Each of the IR communication devices101C and101B′ may be moved or turned somewhat off of the line of sight114and still maintain the IR communication channels between them.

Referring now toFIG. 2, an embodiment of an IR communication device200is illustrated. The IR communication device200represents an embodiment of the IR communication devices101A-101C. The IR communication device200may be used as a toy for voice or vocal communication between a pair of users or children. In which case, a pair of IR communication devices200may be packaged together as a toy set for children. Audible sounds other than audible voice sounds may also be communicated from one IR communication device to another.

The IR communication device may be alternately be referred to as an IR walkie-talkie, a two-way IR communication set, an IR transceiver, an IR phone, or an IR communicator. The IR communication device200is hand-held and portable. The IR communication device200is powered by a battery to eliminate any tethers and facilitate portability. Additionally, the IR communication device200provides bi-directional IR signal communication.

The IR communication device200receives an audible sound/voice input203. The audible sound/voice input203represents either an audible voice sound or another audible sound. In response to the audible sound/voice input203, the IR communication device200generates an outgoing IR beam202A for one of the IR communication channels. The IR communication device200receives an incoming IR beam202B from another of the IR communication channels. In response to the IR beam input202B, the IR communication device200generates an audible sound/voice output205. The audible sound/voice output205represents either an audible voice sound or another type of audible sound.

The IR communication device200includes an IR receiver204, an IR transmitter206, a speaker208, and a microphone210. The IR communication device200further includes a housing201to hold the components together as a unit or set. The IR receiver204receives the incoming IR beam202B. The IR transmitter206generates the IR output beam202A. The IR communication device200may further include an on/off switch or button212and a sight216. The on/off switch212powers on and powers off the IR communication device200. The sight216allows a user to point the transmitter and receiver of the IR communication device200towards another IR communication device to establish a line of sight and the two IR communication channels102A and102B. The sight216may include an eye cup218at one end and an opening220at an opposite end. The sight216may include optics222, such as a lens, within its hollow cylindrical sleeve in order to provide additional magnification to obtain the line of sight with the other IR communication device200at an opposite end of the communication channel.

The microphone210of the IR communication device200, illustrated as being hidden by a grill or cover, receives the audible sound/voice input203. The speaker208of the IR communication device200, illustrated as being hidden by a grill or cover, generates the audible sound/voice output205.

The IR communication device200may further include a talk switch or button214. The talk switch or button214may switch the IR communication device from listening to talking. In one embodiment, the talk switch or button214disables the speaker208to avoid signal feedback. In another embodiment, the talk switch or button214need not disable the speaker208if sufficient optical and/or electrical isolation is provided in the design of the IR communication device200to avoid signal feedback.

The IR communication device200may further include a filter or lens cover211to filter out unwanted light frequencies or wavelengths as well as provide one or more lenses for the IR receiver204and the IR transmitter206. The filter may bandpass desirable light in the IR spectrum and filter out other stray light sources. The function of the one or more lenses for the IR receiver and the IR transmitter is described further below.

Referring now toFIG. 3, a schematic diagram of the electrical components, optical components, and opto-electronic components of the IR communication device is illustrated. The components and the modulation technology of the IR communication device provide a low cost solution and enable it to be sold as a toy for children.

The optical components include a first lens302A and a second lens302B illustrated in FIG.3. While illustrated as separate lenses, the first lens302A and the second lens302B may be the same lens shifted from one position to another or they may be two separate lenses. The first lens302A focuses the IR output from the IR LED306into the IR transmit beam202A. The second lens302B focuses the input IR beam202B onto the photo diode304.

The opto-electronic components of the IR communication device include an IR photo diode304and an IR light emitting diode (LED)306. The IR photo diode304provides the functionality of the IR receiver204. The IR LED306provides the functionality of the IR transmitter206.

The power supply310, consisting of a battery312and a filtering capacitor311, is switched on and off to the electrical and opto-electronic components by means of the on/off switch212. One pole of the on/off switch212couples to the power node301with the other pole coupled to the power supply310. The power node301couples to the components as illustrated inFIG. 3. Aground or negative power node300couples to the components as illustrated in FIG.3. In one embodiment, the battery312is a 9 volt battery and the capacitor311is a 470 uf capacitor.

The talk switch or button214causes a pair of electrical switches214A and214B to alternately be closed and opened. InFIG. 3, switch214A is illustrated as being opened while switch214B is closed, in one case for example. When the talk button or switch214is pushed, switch214A closes while switch214B opens. When the talk button or switch214is released, switch214A is opened and switch214B is closed. In this manner, the IR communication device may switch back and forth between transmitting an IR beam202A over an IR communication channel and receiving an IR beam202B over an IR communication channel. The electrical switches214A and214B can be replaced by active transistor devices or logic devices to momentarily connect and interrupt signal flow in order to provide similar functionality.

The speaker208transduces an electrical voice signal into an audible voice sound or other type of audible sound as the audible sound/voice output205. The microphone210transduces an audible sound or audible voice sound, the audible sound/voice input203, into an electrical voice signal.

The microphone210is coupled to an input of an amplifier320. Amplifier320includes resistors321-325, capacitors326-328, and an operational amplifier329coupled together as shown in FIG.3. The amplifier320amplifies the electrical voice signal generated by the microphone210into an electrical current signal for coupling through switch214A into the IR transmitter206. In one embodiment, the operational amplifier329is an LM 358 OPAMP; the resistors321-325are 2.2 Kohm, 10 Kohm, 10 Kohm, 10 Kohm, and 100 Kohm resistors respectively; and the capacitors326-328are 1 uf, 100 pf, and 470 uf capacitors respectively.

The IR transmitter206includes the IR LED306, a bipolar junction transistor (BJT)330, and resistors331-332coupled together as illustrated in FIG.3. The IR transmitter206receives the amplified current signal representing the voice signal of the microphone210and directly modulates the forward current of the IR LED306. The amplified microphone current signal is coupled into the base of the bipolar junction transistor330in order to vary the forward current through the IR LED306. The IR transmitter206functions to convert or transduce an electrical signal input into an infrared light signal output. The output IR light radiation from the LED306is a point source and is coupled into the first lens302to generate the IR output beam202A. The first lens302collimates the point source into a collimated IR light beam. In one embodiment, the BJT 330 is a JE9013 BJT; and the resistors331-332are 100 Kohm and 24 ohm resistors respectively.

The IR receiver204includes the photo diode304, and an operational amplifier340, a resistor341and a capacitor342. The photo diode304generates a current in response to receiving the focused IR light beam of the input IR beam202B through the second lens302B. The operational amplifier340, in conjunction with the resistor341and the capacitor342, amplifies the current generated by the photo diode304. The amplified current output of the IR receiver204is coupled to one pole of the switch214B. The IR receiver204functions to convert or transduce an infrared light signal input into an electrical signal output. In one embodiment, the operational amplifier340is an LM 358 OPAMP; the resistor341is a 100 Kohm resistor; and the capacitor342is a 100 pf capacitor.

Another pole of switch214B couples to an input of an audio amplifier350and the power node301through resistors322and344. Switch214B is closed in order for the audio amplifier350to receive the amplified current output signals from the IR receiver204. The audio amplifier350includes a variable resistor351, an operational amplifier352, and capacitors353-355coupled together as illustrated in FIG.3. The variable resistor351is controlled by the volume control knob213in order to vary the input signal to the audio amplifier352and therefore control the audible output or volume of the speaker208. In one embodiment, the operational amplifier352is an LM 386 OPAMP; the variable resistor351varies from 1 to 10 kohm; the resistor344has a resistance of 1 megaohm; and the capacitors353-355are 1 uf, 10 uf, and 250 uf capacitors respectively.

The audio amplifier350couples to the speaker208. In one embodiment, the speaker208is a ¼W, 8 ohm speaker. The speaker208functions to convert or transduce an electrical signal into sound pressure to reproduce an audible sound or audible voice sound as the audible sound/voice output205.

As previously discussed, the IR communication device may use one or more lenses. The one or more lenses may be used to collimate the light from a point source of the IR LED or focus collimated light from an focal plane to a point source of the IR photodiode.

Referring now toFIG. 4A, a light ray diagram for the IR LED306and the lens302A is illustrated. The lens302A in one embodiment is a fresnel lens. The center points of the optical axis of the IR LED306and the lens302A are aligned along a center line402. The IR LED306and the lens302A are separated by a distance referred to as the focal length FlTX. The IR LED306radiates at a beam angle θB. In one embodiment, the beam angle θBis twenty degrees for example. The lens302A can collimate the light so that is spreads off of the center line402by a transmission angle θTX. In one embodiment, the transmission angle θTXis one and one half degrees for example. In this manner the IR output light beam202A can travel a long distance as a high intensity IR light beam.

Referring now toFIG. 4B, a light ray diagram for the IR photodiode304and the lens302B is illustrated. The lens302B in one embodiment is a fresnel lens. The center points of the optical axis of the IR photo diode304and the lens302B are aligned along a center line412. The IR photodiode304and the lens302B are separated by a distance referred to as the focal length FlRCV. Incoming IR light202B in the focal plane along center line412and off of the center line by a reception angle θRCV, is focused by the lens302B down to a point of the reception area of the IR photodiode304. In one embodiment, the reception angle θRCVis one and one half degrees. In one embodiment, the reception area of the IR photodiode304is seven square millimeters for example. The radiant sensitive area of the IR photodiode304is positioned at or near the focal point of lens302B. In one embodiment for example, the focal length of lens302B is 2.4 inches.

Typically, the IR LED306and the IR photodiode304are a matched pair. That is, the IR LED306and the IR photodiode304are constructed to transmit and receive IR radiation around the same center frequency or wavelength. For example, the IR LED306and the IR photodiode304have a center wavelength of 850 nanometers (nm) around which they can transmit and receive IR radiation. As another example, the IR LED306and the IR photodiode304have a center wavelength of 950 nanometers (nm) around which they can transmit and receive IR radiation. Other center wavelengths and frequencies may be used.

The IR communication device200may be used for simplex or full duplex bi-directional communication with proper optical and/or electrical isolation to avoid signal feedback. Each of the IR communication channels102A and102B may have the same center frequency or wavelength of IR radiation or they may have a different center frequency or wavelength of IR radiation. Using one IR communication channel, all the voice signals communicated in each direction are found on the same center wavelength or frequency. Because the IR radiation is light, there is little interference when signals cross over the IR communication channel between the IR communication devices200.

Alternatively, two IR communication channels may be provided, one for each direction of communication. In this case a different center frequency or wavelength is provided for the IR communication channel102A from that of the IR communication channel102B. The IR LED306and IR photodiode304are matched across a pair of IR communication devices improving the quality of the IR communication between IR communication devices in the case of simplex or full duplex bi-directional communication.

Referring now toFIG. 4C, a light ray diagram illustrates the functionality of one IR communication channel and the line of sight between two IR communication devices200.FIG. 4Cillustrates a single IR communication channel between an IR communication device which is transmitting and another IR communication device at an opposite end which is receiving. The IR communication devices are separated by a distance XIR, referred to as an infrared communication distance

At each end of the light ray diagram may be a lens of the IR communication device. The lens in front of the IR receiver provides an angle of reception which is twice the angle of θRCV(2×θRCV). The lens in front of the IR transmitter on an opposite end of the communication channel provides an angle of transmission which is twice the angle of θTX(2×θTX). In one embodiment the angle of reception 2×θRCVis equal to the angle transmission 2×θTX.

The distance XIRis more a function of the optical gain on the receiving side of the communication channel. The line of sight between the IR communication devices at each end of the communication channel is a function of the beam spread and the angle of acceptance. The beam spread is the amount the IR transmitted beam from one end of the IR communication channel is spread out to the angle of transmission 2×θTX. In one embodiment 2×θTXis 3 degrees and the angle of reception or acceptance 2×θRCVis 5 degrees. Each of the lenses in front of the IR receiver and the IR transmitter can affect θRCVand θTXrespectively.

In a preferred embodiment, a fresnel lens is used in front of the IR receiver to provide and improve optical gain on the receiving side of the IR communication channel. Using a fresnel lens in front of each of the IR transmitter and receiver has resulted in a range of XIRfrom approximately five feet to three thousand feet. In another embodiment, no lens is used in front of the IR photodiode304such that the range of distance of XIRis substantially reduced to approximately zero feet to fifty feet.

Because of the line-of-sight communication between the IR communication devices, its difficult for a third party to tap or eavesdrop on the communication between end users. Thus, the modulation or encoding scheme can be simple and not complex resulting in lower costs and still provide protected communication between end users.

Referring now toFIGS. 5A,5B,5C, and5D, exemplary waveforms illustrate how a voice signal representing audible sounds or voice sounds is detected by the microphone and directly modulated onto the IR transmitter at one end of the IR communication channel; and then detected at the infrared receiver and presented to the speaker at the other end of the IR communication channel.

InFIG. 5A, waveform502is illustrated. Waveform502represents a current waveform which is generated by the microphone receiving audible sounds or voice sounds and the amplifier320amplifying the voice signal of the microphone. The current waveform502is coupled through to the IR transmitter206.

FIG. 5Billustrates a waveform504to indicate the current flowing through the infrared LED306and the resultant infrared LED output signal202A. The relationship of the infrared LED current to infrared radiant output intensity is generally a linear function. Therefore, the infrared transmitter206generates infrared light at intensity levels that are directly responsive to the amplified microphone signal502of FIG.5A.

FIG. 5Cshows waveforms506A and506B to illustrate the current that may be generated by the photodiode of the IR receiver204of FIG.2. Waveform506A is illustrated as having a lower amplitude current signal than that of waveform506B. A lower or higher amplitude of current signal is a direct result of the amount of infrared light incident on the photodiode304of the IR receiver204. Waveforms506A and506B may also represent the transmitter and receiver being separated by different distances XIR. For example, waveform506A may indicate that the transmitter and receiver are separated by a first distance XIRof 2000 feet and waveform506B may represent that the transmitter and receiver are separated by a second distance XIRof 500 feet. Alternatively, waveforms506A and506B may represent the transmitter and receiver being separated by an equal distance of 50 feet for example and the resultant difference in photodiode current between the waveforms is due to a change in optical gain characteristics through the use of different lenses or different focal lengths, etc. In this case the waveform506A may illustrate an IR receiver204that does not have a focusing lens302B in front of the IR photodiode304to achieve optical gain and waveform506B may illustrate an IR receiver204that does have a focusing lens302B in front of the IR photodiode304of the IR receiver204.

FIG. 5Dillustrates waveform508which is the audio current that is presented to the speaker. The current amplitude of the waveform508is amplified from that of the current amplitude of waveform506A or506B, illustrated inFIG. 5C, in order to properly drive the speaker208. The frequency and amplitude of the waveform508is representative of the audible output generated by the speaker208.

In this manner, the IR communication devices200at each end directly modulate an audible sound or voice in the audible frequency band between approximately 20 Hz to 20 kHz into an IR signal at the transmitting end for transmission over an IR communication channel and demodulate the received IR signal into an audible sound or audible voice sound between approximately 20 Hz to 20 kHz on the receiving end.

The disclosed embodiment does not employ a modulated center carrier frequency in order to achieve a lower cost. However, a center carrier frequency may be employed with the audible voice or sound modulated or mixed onto a center carrier frequency by using amplitude modulation (AM) or frequency modulation (FM) and then provided to the IR LED for transmission using an IR signal. Corresponding reception and demodulation or demixing on the receive end is used in order to obtain the baseband signal of the audible voice sound or audible sound. Details of this alternate embodiment of the infrared communication device would be understood by those ordinarily skilled in the art after reading through this disclosure.