US20010051505A1 - Infrared link - Google Patents
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- US20010051505A1 US20010051505A1 US08/994,229 US99422997A US2001051505A1 US 20010051505 A1 US20010051505 A1 US 20010051505A1 US 99422997 A US99422997 A US 99422997A US 2001051505 A1 US2001051505 A1 US 2001051505A1
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- electromagnetic waves
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W76/00—Connection management
- H04W76/10—Connection setup
Definitions
- the present invention relates to a method of transferring information between two terminal devices using infrared wavelength range.
- the invention is in particular related to two-way data transfer using the same infrared wavelength range, and terminal devices between which the data transfer is carried out.
- IrDA -standard prior known to a person skilled in the art, is a data transfer protocol for one-way serial data. Utilizing it, it is possible to transfer data between two terminal devices alternately using infrared wavelength range from 850 to 900 nm. In many cases a simultaneous, two-way (full duplex) data transfer would be a great advantage. IrDa -standard does not offer this possibility, nor any other prior known data transfer system operating in the infrared wavelength range.
- An infrared link has been invented, using which it is possible to transfer data between two terminal devices simultaneously to both directions (full duplex).
- An infrared link according to the invention is preferably realized using linearly polarized infrared light, but it is also possible to use other wavelength ranges.
- a data transfer channel to be formed using an infrared connection is divided into two separate channels using polarization.
- the polarization of light is achieved using e.g. polarizers, beam-splitters or birefracting crystals.
- data transfer to one direction is realized e.g. using vertically polarized infrared light, and correspondingly to the other direction using horizontally polarized infrared light.
- the data transfer is preferably realized using a direct light beam, but it is also possible to realize it using an optical fiber cable with suitable optical properties.
- An infrared link according to the invention facilitates interrupting of the otherwise uninterrupted data transfer connection at the request of the receiving terminal device.
- the receiving terminal device can e.g. inform of the filling up of the buffer memory of the receiver in order to interrupt the data transmission.
- data transfer errors can easily and quickly be corrected straight after they are detected, because the receiving terminal device can request for a re-transmission immediately after having detected the errors.
- two-way data transfer preferably makes data transfer faster in such occasions in which data is exchanged between two terminal devices. The bigger the volume of the data transfer required, the bigger the benefit achieved with the invention.
- a data transfer channel operating at infrared wavelength range is divided into two parts utilizing polarization.
- transmitter A can select the receiving terminal device B or C using the polarization of the infrared light it emits. This is realized e.g. by providing receiver B with a horizontal polarizer and receiver C with a vertical polarizer, and transmitter A with transmitting means which are capable of transmitting both horizontally and vertically polarized infrared light as chosen.
- dividing an infrared data transfer channel operating at infrared wavelength range into two channels, achieved by polarization preferably facilitates also the doubling of the data transfer capacity of the data transfer channel.
- a transmitter is provided with two separate transmitter units, of which one transmits data using horizontally polarized infrared light and the other using vertically polarized infrared light.
- the informations are separated from each other using horizontal and vertical polarizers or a beam splitter.
- IrDA-connection capable of 4 Mbps data transfer rate, to transfer data at a total data transfer rate of 8 Mbps.
- the system according to the invention also facilitates the realization of two 4 Mbps data transfer channels simultaneously.
- FIG. 1 presents the propagation of electromagnetic radiation, such as infrared radiation, and the directions of the vectors of an electric field and of a magnetic field in relation to the direction of propagation of the radiation,
- FIGS. 2A and 2B present the propagation of unpolarized infrared light through two polarizers at different angles between polarization axes
- FIGS. 3A, 3B and 3 C present the propagation of infrared light from a transmitter to two separate receivers using different polarizer combinations
- FIG. 3D presents a receiver provided with an adjustable polarizer
- FIG. 4 presents a system according to the invention utilizing an infrared link realized using polarizers, in which system data is transferred in both directions between two terminal devices,
- FIG. 5 presents a system according to the invention utilizing an infrared link realized using polarizers, in which system data is transferred from one terminal device to another using two separate data transfer channels,
- FIG. 6 presents refraction and reflection of infrared light when it meets the boundary surface of two different media
- FIG. 7 presents a system according to the invention utilizing an infrared link realized using beam splitters, in which system data is transferred in both directions between two terminal devices,
- FIG. 8 presents a system according to the invention utilizing an infrared link realized using beam splitters, in which system data is transferred from one terminal device to another using two separate data transfer channels, and
- FIG. 9 presents a data transfer system according to the invention comprising e.g. mobile stations according to the invention.
- the direction of the electric field describes the polarization. If the light consists of rays, the electric fields of which are oriented in the same direction, the light is said to be linearly polarized. If the vector of the electric field is horizontal, it is said that the light beam is horizontally polarized and correspondingly, if the vector of the electric field is vertical, vertically polarized.
- Extinction ratio k 2 /k 1 depends on the construction of the polarizer and the wavelength used.
- the extinction ratio is typically 10 ⁇ 3 for sheet polarizers, 10 ⁇ 4 for thin film polarizers and ⁇ 10 ⁇ 5 for crystal polarizers.
- transmittance k is a function of the following equation:
- ⁇ is the angle between the electric field vector and the polarization axis.
- I the intensity of transmitted light at angle ⁇
- I max the maximum intensity of transmitted light
- ⁇ the angle between the polarization axes of the polarizers.
- FIGS. 3 A- 3 C, 4 and 5 present the test arrangement, with which tests were conducted on the operation modes of one embodiment of an infrared link according to the invention
- FIGS. 7 and 8 present another embodiment of the invention.
- infrared transmitter elements TX 1 and TX 2 TX 1 and TX 2 for shortness
- infrared receiver elements RX 1 and RX 2 RX 1 and RX 2 for shortness
- commercially available combined infrared transceiver elements type HSDL-1000 combined Infrared Transceiver manufactured by Hewlett Packard. Equally well separate transmitter- and receiver elements could have been used.
- Adjustable signals S 1 ′ and S 2 ′ were fed to transmitter elements TX 1 and TX 2 using signal generators S 1 and S 2 .
- Signals O 1 ′ and O 2 ′ received by receiver elements RX 1 and RX 2 were analyzed using oscilloscopes O 1 and O 2 .
- As polarizers V 1 , V 2 , H 1 and H 2 sheet polarizers were used, type HR PLASTIC PID 605211. They are made of oriented molecular structure long chain polyvinyl alcohol, which cause high absorbing and polarization. The function principle of a sheet polarizer is to absorb unwanted light rays in its structures. The maximum intensity of the transmitted infrared light used in the test arrangement was at wavelength 875 nm and the maximum sensitivity of the received signal was at 880 nm.
- FIG. 3A presents how unpolarized infrared light LU propagates in free space from transmitter element TX 1 equally to receiver element RX 1 as well as to receiver element RX 2 .
- infrared light signal LU is detected equally in receiver elements RX 1 and RX 2 provided that the distances and angles of incidence between transmitter element TX 1 and receiver elements RX 1 and RX 2 are essentially equal.
- Infrared light behaves (alike visible light) in such a way that the intensity of infrared light LU received by and receiver elements RX 1 and RX 2 becomes the lower the longer the distance between transmitter element TX 1 and receiver elements RX 1 and RX 2 becomes.
- transmitter element TX 1 emits infrared light at different efficiency to different directions.
- signal S 1 ′ is supplied from signal generator S 1 to transmitter element TX 1 for transmission
- received signals O 1 ′ and O 2 ′ corresponding with transmitted signal S 1 ′ are presented in the displays of oscilloscopes O 1 and O 2 when transmitter element TX 1 and receiver elements RX 1 and RX 2 are suitably directed.
- FIG. 3B presents what happens when vertical polarizer V 1 is placed in front of transmitter element TX 1 , vertical polarizer V 2 in front of receiver element RX 1 and horizontal polarizer H 2 in front of receiver element RX 2 .
- the infrared light emitted by transmitter element TX 1 is polarized in vertical polarizer V 2 into vertically polarized infrared light LV.
- vertically polarized infrared light LV passes through vertical polarizer V 2 .
- the transmitted infrared beam can be detected using receiver element RX 1 .
- Transmitted signal S 1 ′ is detected on the display of oscilloscope O 1 as signal O 1 ′.
- vertically polarized infrared light LV does not pass through horizontal polarizer H 2 , but is absorbed in horizontal polarizer H 2 . Accordingly, signal O 2 ′ is not detected with oscilloscope O 2 ′.
- FIG. 3C presents a corresponding test arrangement changed in such a way, that vertical polarizer V 2 has been replaced with horizontal polarizer H 1 .
- the infrared light emitted by transmitter element TX 1 is polarized into horizontally polarized infrared light LH. It does not pass through vertical polarizer V 2 , and accordingly signal O 1 ′ is not detected with oscilloscope O 1 , but horizontally polarized infrared light LH passes through horizontal polarizer H 2 instead.
- Signal O 2 ′ corresponding to transmitted signal S 1 ′ can be detected using oscilloscope O 2 . Based upon the test arrangement shown in FIGS.
- the receiver to which signal S 1 ′ is transferred can be selected.
- the polarizer placed in front of the transmitter can be of rotating type, in which case the direction of the polarizing axis is freely selectable.
- FIG. 3C presents a solution to correct this situation, in which solution horizontal polarizer H 2 (FIG. 3C) in front of receiver element RX 2 has been replaced with adjustable polarizer P 1 . It is possible to realize adjustable polarizer P 1 e.g.
- receiver element RX 2 with processor 15 and rotator motor 13 .
- Processor 15 measures the level of the signal it receives from detector 12 e.g. using a level detector (not shown in the figure), based upon the data received from said detector, processor 15 controls motor 13 to rotate adjustable polarizer P 1 into the optimal position.
- processor 15 controls motor 13 to rotate adjustable polarizer P 1 into the optimal position.
- receiver RX 2 monitors also another data transfer channel which has been realized using a 90° shifted polarization axis. This is realized by rotating polarizer P 1 for 90°. A return to the original data transfer connection is made by rotating polarizer P 1 another 90°.
- FIG. 4 presents an embodiment of an infrared link according to the invention, in which simultaneous two-way (full-duplex) data transfer between two terminal devices 10 and 20 has been realized using infrared connection.
- First terminal device 10 comprises transmitter element TX 1 , receiver element RX 2 , vertical polarizer V 1 and horizontal polarizer H 1 .
- Second terminal device 20 has a similar construction, comprising transmitter element TX 2 , receiver element RX 1 , vertical polarizer V 2 and horizontal polarizer H 2 .
- Simultaneously transmitter element TX 2 of terminal device 20 transmits dense square wave S 2 ′ generated by signal generator S 2 through horizontal polarizers H 2 and H 1 to receiver element RX 2 , from which dense square wave S 2 ′ can be detected using oscilloscope O 2 .
- Vertical polarizer V 2 prevents horizontally polarized infrared light beam LH from entering receiver element RX 1 of terminal device 20 and interfering in its operation. In this way, two-way data transfer between terminal devices 10 and 20 is possible using an infrared link according to the invention utilizing a method based upon polarization.
- polarizers V 1 , V 2 H 1 and H 2 used in the test arrangements have been realized using two polarizing sheets placed on top of each other, yielding a higher polarization grade.
- FIG. 5 presents another embodiment of an infrared link according to the invention, in which transferring two independent signals S 1 ′ and S 2 ′ from terminal device 30 to terminal device 40 has been realized.
- the propagation of sparse square wave signal S 1 ′ from transmitter element TX 1 to receiver element RX 1 is identical with the propagation presented in FIG. 4.
- Signal S 2 ′ instead, is transferred to the opposite direction.
- Terminal device 30 comprises, in addition to transmitter element TX 1 , second transmitter element TX 2 , to which dense square wave signal S 2 ′ is fed from signal generator S 2 .
- the infrared light signal transmitted by transmitter element TX 2 is horizontally polarized in horizontal polarizer H 1 .
- Horizontally polarized infrared light LH propagates through horizontal polarizer H 2 to receiver element RX 2 , from which the signal can be detected using oscilloscope O 2 . Consequently, linearly polarized infrared light beams LV and LH transmitted by terminal device 30 can be separated from each other in the infrared link according to the invention in terminal device 40 using polarizers V 2 and H 2 . It is because of this that it is possible to transfer two separate data signals S 1 ′ and S 2 ′ from terminal device 30 to terminal device 40 , or alternatively to double the data transfer rate available for a conventional infrared connection.
- infrared light beams LV and LH having polarization axes perpendicular to each other, were formed and separated from each other using polarizers V 1 , V 2 , H 1 and H 2 . It is possible to use beam splitters instead of polarizers V 1 , V 2 , H 1 and H 2 .
- the basic purpose of a beam splitter is to divide a (infrared) light beam into two parts, both parts having equal amplitudes. In practice this means amplitude ratios from approximately 30/70 to 50/50, depending on the material the beam splitter is made of.
- One beam splitter suitable for infrared frequency range is a thin film made of polytetrafluorethylene (Mylar).
- equation (4) is simplified (approximately) into form:
- FIG. 7 presents an embodiment of an infrared link according to the invention, in which also two-way, simultaneous (full-duplex) data transfer has been realized.
- the operating principle is similar to that of the system presented in FIG. 4, but in the system in FIG. 7 beam splitters BS 1 and BS 2 are used instead of polarizers V 1 , V 2 , H 1 and H 2 for polarizing the infrared light and for separating the polarized infrared beams.
- Signal S 1 ′ is transferred from transmitter element TX 1 as an infrared signal to beam splitter BS 1 , in which the vertically polarized part LV of the infrared light passes through beam splitter BS 1 .
- the infrared beam meets beam splitter BS 2 , in which horizontally polarized infrared light beam LH is reflected. Any eventual vertically polarized infrared light passes through beam splitter BS 2 and is absorbed in the constructions of device 60 . Reflected infrared light beam LH then meets beam splitter BS 1 , from which it is reflected to receiver element RX 2 for detection. In this way the two-way infrared link according to the invention can also be realized using beam splitters BS 1 and BS 2 .
- FIG. 8 presents an embodiment of the infrared link according to the invention, in which also two-way data transfer, alike the one in FIG. 5, from terminal device 70 to terminal device 80 has been realized.
- polarizers V 1 , V 2 , H 1 and H 2 have been replaced with beam splitters BS 1 and BS 2 .
- Terminal device 70 is equipped with two transmitter elements TX 1 and TX 2 , through which infrared signals are directed at a beam splitter.
- the vertically polarized part of the infrared light beam emitted by transmitter element TX 1 passes through beam splitters BS 1 and BS 2 , while the horizontally polarized part of the infrared light beam emitted by transmitter element TX 2 is reflected from both beam splitter BS 1 and BS 2 as presented in FIG. 8. Any other infrared light beams are absorbed in constructions (ref. 71 ).
- An infrared link according to the invention is suitable for use e.g. in systems alike data transfer systems 110 presented in FIG. 9, in which systems there is a need for two-way data transfer, such as data transfer between mobile station 111 , 111 ′, 111 ′′ and portable computer 118 .
- receiver- and transmitter elements 118 ′, 119 , 119 ′, 119 ′′ it is possible to use e.g. transmitter/receiver elements TX 1 , TX 2 , RX 1 , and RX 2 presented in connection with FIGS. 3A, 3B, 3 C, 4 , 5 and 7 .
- An exemplary embodiment of data transfer system 110 comprises mobile stations 111 , 111 ′, 111 ′′, base station 112 (BTS, Base Transceiver Station), base station controller 113 (BST, Base Station Controller), mobile switching center 114 (MSC, Mobile Switching Center), telecommunication networks 115 and 116 , and user terminals 117 connected to the networks either directly or over a terminal device.
- BTS Base Transceiver Station
- BST Base Station Controller
- MSC Mobile Switching Center
- telecommunication networks 115 and 116 and user terminals 117 connected to the networks either directly or over a terminal device.
- mobile stations 111 , 111 ′, 111 ′′ and other and user terminals 117 are connected to each other through telecommunication networks 115 and 116 . It is also possible to transfer data utilizing the infrared link according to the invention between mobile stations 111 , 111 ′, 111 ′′ according to the invention.
Abstract
Description
- The present invention relates to a method of transferring information between two terminal devices using infrared wavelength range. The invention is in particular related to two-way data transfer using the same infrared wavelength range, and terminal devices between which the data transfer is carried out.
- In the modern information society numerous portable terminal devices are used, such as advanced computers, mobile stations and pocket computers. It is very often necessary to transfer information from these terminal devices to some other device, such as a normal computer, and correspondingly to receive data from this other device. This data transfer is typically realized either using a cable specially manufactured for this purpose, but nowadays more and more extensively using an infrared connection. An infrared connection is a fast, and on short distances reliable, way to transfer data.
- Previously an infrared connection between two devices was realized using different manufacturers' own standards (proprietary standards). This naturally reduced the compatibility of terminal devices of different brands and infrared connections becoming more common. In applications in which compatibility was not required, such as remote control of domestic appliances, using infrared connections quickly became common. It would be in the advantage of different manufacturers, but above all in advantage of end users, if there were one general standard for data transfer realized using infrared connection. One of the solutions aiming at this target is IrDA (Infrared Data Association) -standard.
- IrDA -standard, prior known to a person skilled in the art, is a data transfer protocol for one-way serial data. Utilizing it, it is possible to transfer data between two terminal devices alternately using infrared wavelength range from 850 to 900 nm. In many cases a simultaneous, two-way (full duplex) data transfer would be a great advantage. IrDa -standard does not offer this possibility, nor any other prior known data transfer system operating in the infrared wavelength range.
- Now an infrared link has been invented, using which it is possible to transfer data between two terminal devices simultaneously to both directions (full duplex). An infrared link according to the invention is preferably realized using linearly polarized infrared light, but it is also possible to use other wavelength ranges. A data transfer channel to be formed using an infrared connection is divided into two separate channels using polarization. The polarization of light is achieved using e.g. polarizers, beam-splitters or birefracting crystals. In this way, when data is transferred between two terminal devices, data transfer to one direction is realized e.g. using vertically polarized infrared light, and correspondingly to the other direction using horizontally polarized infrared light. The data transfer is preferably realized using a direct light beam, but it is also possible to realize it using an optical fiber cable with suitable optical properties.
- An infrared link according to the invention facilitates interrupting of the otherwise uninterrupted data transfer connection at the request of the receiving terminal device. In such a case the receiving terminal device can e.g. inform of the filling up of the buffer memory of the receiver in order to interrupt the data transmission. Correspondingly, data transfer errors can easily and quickly be corrected straight after they are detected, because the receiving terminal device can request for a re-transmission immediately after having detected the errors. In addition to above, two-way data transfer preferably makes data transfer faster in such occasions in which data is exchanged between two terminal devices. The bigger the volume of the data transfer required, the bigger the benefit achieved with the invention.
- In an infrared link according to the invention a data transfer channel operating at infrared wavelength range is divided into two parts utilizing polarization. In one embodiment of the invention it is possible to use the created two data transfer channels for data transfer to a certain two terminal device. In this way, when data is transferred from transmitter A to receiver B or C, transmitter A can select the receiving terminal device B or C using the polarization of the infrared light it emits. This is realized e.g. by providing receiver B with a horizontal polarizer and receiver C with a vertical polarizer, and transmitter A with transmitting means which are capable of transmitting both horizontally and vertically polarized infrared light as chosen.
- In another embodiment of the invention dividing an infrared data transfer channel operating at infrared wavelength range into two channels, achieved by polarization, preferably facilitates also the doubling of the data transfer capacity of the data transfer channel. This has been realized in such a way that a transmitter is provided with two separate transmitter units, of which one transmits data using horizontally polarized infrared light and the other using vertically polarized infrared light. In a receiver the informations are separated from each other using horizontal and vertical polarizers or a beam splitter. In this way it is possible, using an IrDA-connection capable of 4 Mbps data transfer rate, to transfer data at a total data transfer rate of 8 Mbps. Because the data transfer channels separated from each other using polarization are independent of each other, the system according to the invention also facilitates the realization of two 4 Mbps data transfer channels simultaneously.
- The features characteristic of the infrared link according to the invention are presented in the characterizing parts of
claims - The invention is described in detail in the following with reference to enclosed figures, of which
- FIG. 1 presents the propagation of electromagnetic radiation, such as infrared radiation, and the directions of the vectors of an electric field and of a magnetic field in relation to the direction of propagation of the radiation,
- FIGS. 2A and 2B present the propagation of unpolarized infrared light through two polarizers at different angles between polarization axes,
- FIGS. 3A, 3B and3C present the propagation of infrared light from a transmitter to two separate receivers using different polarizer combinations,
- FIG. 3D presents a receiver provided with an adjustable polarizer,
- FIG. 4 presents a system according to the invention utilizing an infrared link realized using polarizers, in which system data is transferred in both directions between two terminal devices,
- FIG. 5 presents a system according to the invention utilizing an infrared link realized using polarizers, in which system data is transferred from one terminal device to another using two separate data transfer channels,
- FIG. 6 presents refraction and reflection of infrared light when it meets the boundary surface of two different media,
- FIG. 7 presents a system according to the invention utilizing an infrared link realized using beam splitters, in which system data is transferred in both directions between two terminal devices,
- FIG. 8 presents a system according to the invention utilizing an infrared link realized using beam splitters, in which system data is transferred from one terminal device to another using two separate data transfer channels, and
- FIG. 9 presents a data transfer system according to the invention comprising e.g. mobile stations according to the invention.
- Light travels in the form of transverse electromagnetic waves. The electric field and the magnetic field vectors are perpendicular to the direction of propagation and to each other as shown in FIG. 1. Defining the direction of propagation P of a ray and the direction of the electric field vector E defines actually a three-dimensional vector space, the vectors of which are: the direction of beam propagation P, electric field E and magnetic field H. Most incoherent light sources consist of large number of emitting atoms or molecules. The vectors of the electric fields of the rays emitted from these light sources have random directions—such light rays are called unpolarized.
- The direction of the electric field describes the polarization. If the light consists of rays, the electric fields of which are oriented in the same direction, the light is said to be linearly polarized. If the vector of the electric field is horizontal, it is said that the light beam is horizontally polarized and correspondingly, if the vector of the electric field is vertical, vertically polarized.
- When a linearly polarized light beam is directed at a polarizer, the amount of the light passing through depends on the angle between the polarization axis of the light beam and the polarization axis of the polarizer. When the axes are parallel, the light passing through reaches its maximum intensity. In such a case the ratio between the light passed through and the light reaching the polarizer is called major principal transmittance k1. When the polarizer in turned into a position in which the intensity of the linearly polarized light transmitted through the polarizer is at minimum, correspondingly minor principal transmittance k2 is obtained. The ratio between major and minor transmittance k2/k1 is called extinction ratio. Extinction ratio k2/k1 depends on the construction of the polarizer and the wavelength used. The extinction ratio is typically 10−3 for sheet polarizers, 10−4 for thin film polarizers and <10−5 for crystal polarizers. When a polarizer is rotated in relation to the polarization axis of a linearly polarized light beam, transmittance k is a function of the following equation:
- k=(k 1 −k 2)cos2 θ+k 2, (1)
- in which θ is the angle between the electric field vector and the polarization axis.
-
- presuming that k1>>k2
- When unpolarized light beam1 (FIG. 2A) passes through
polarizer 2,light 3 becomes linearly polarized. When this linearlypolarized light 3 is directed through anotherpolarizer 4, the intensity of the transmittedlight 5 depends on the angle betweenpolarization axes 2′, 4′ ofpolarizers light 5 is at highest, and correspondingly when the angle θ is 90° (FIG. 2B) the intensity of transmittedlight 5 is at lowest. At other angles θ, the intensity of transmittedlight 5 is obtained using equation - I≈Imax cos2θ (3)
- in which
- I=the intensity of transmitted light at angle θ,
- Imax=the maximum intensity of transmitted light
- θ=the angle between the polarization axes of the polarizers.
- FIGS.3A-3C, 4 and 5 present the test arrangement, with which tests were conducted on the operation modes of one embodiment of an infrared link according to the invention, and FIGS. 7 and 8 present another embodiment of the invention. In the tests it was used as infrared transmitter elements TX1 and TX2 (TX1 and TX2 for shortness) and as infrared receiver elements RX1 and RX2 (RX1 and RX2 for shortness) commercially available combined infrared transceiver elements, type HSDL-1000 combined Infrared Transceiver manufactured by Hewlett Packard. Equally well separate transmitter- and receiver elements could have been used. Adjustable signals S1′ and S2′ were fed to transmitter elements TX1 and TX2 using signal generators S1 and S2. Signals O1′ and O2′ received by receiver elements RX1 and RX2 were analyzed using oscilloscopes O1 and O2. As polarizers V1, V2, H1 and H2 sheet polarizers were used, type HR PLASTIC PID 605211. They are made of oriented molecular structure long chain polyvinyl alcohol, which cause high absorbing and polarization. The function principle of a sheet polarizer is to absorb unwanted light rays in its structures. The maximum intensity of the transmitted infrared light used in the test arrangement was at wavelength 875 nm and the maximum sensitivity of the received signal was at 880 nm.
- In the test arrangements and in their description vertically and horizontally polarized infrared lights are used. This is done because there are established notations for unpolarized, vertically- and horizontally polarized infrared light, and the concepts are unambiguous. Equally well it is possible to use, instead of vertically- and horizontally polarized infrared light beams, infrared light beams that have another polarization angle. It is essential that the angle between the angle of polarization axes of the polarized infrared light beams is approximately 90°. The more the angle between the polarization axes differs from 90°, the more unstable the operation of the system gets.
- FIG. 3A presents how unpolarized infrared light LU propagates in free space from transmitter element TX1 equally to receiver element RX1 as well as to receiver element RX2. In the arrangement in FIG. 3A infrared light signal LU is detected equally in receiver elements RX1 and RX2 provided that the distances and angles of incidence between transmitter element TX1 and receiver elements RX1 and RX2 are essentially equal. Infrared light behaves (alike visible light) in such a way that the intensity of infrared light LU received by and receiver elements RX1 and RX2 becomes the lower the longer the distance between transmitter element TX1 and receiver elements RX1 and RX2 becomes. Also the directing of transmitter element TX1 has an essential importance, because transmitter element TX1 emits infrared light at different efficiency to different directions. When signal S1′ is supplied from signal generator S1 to transmitter element TX1 for transmission, received signals O1′ and O2′ corresponding with transmitted signal S1′ are presented in the displays of oscilloscopes O1 and O2 when transmitter element TX1 and receiver elements RX1 and RX2 are suitably directed.
- FIG. 3B presents what happens when vertical polarizer V1 is placed in front of transmitter element TX1, vertical polarizer V2 in front of receiver element RX1 and horizontal polarizer H2 in front of receiver element RX2. The infrared light emitted by transmitter element TX1 is polarized in vertical polarizer V2 into vertically polarized infrared light LV. When it meets vertical polarizer V2, the polarization axis of which accordingly is essentially parallel to that of vertical polarizer V1, vertically polarized infrared light LV passes through vertical polarizer V2. In this case the transmitted infrared beam can be detected using receiver element RX1. Transmitted signal S1′ is detected on the display of oscilloscope O1 as signal O1′. Whereas, vertically polarized infrared light LV does not pass through horizontal polarizer H2, but is absorbed in horizontal polarizer H2. Accordingly, signal O2′ is not detected with oscilloscope O2′.
- FIG. 3C presents a corresponding test arrangement changed in such a way, that vertical polarizer V2 has been replaced with horizontal polarizer H1. In this case the infrared light emitted by transmitter element TX1 is polarized into horizontally polarized infrared light LH. It does not pass through vertical polarizer V2, and accordingly signal O1′ is not detected with oscilloscope O1, but horizontally polarized infrared light LH passes through horizontal polarizer H2 instead. Signal O2′ corresponding to transmitted signal S1′ can be detected using oscilloscope O2. Based upon the test arrangement shown in FIGS. 3B and 3C it is observed that, depending on polarizers V1 and H1 exchanged in front of transmitter element TX1, the receiver to which signal S1′ is transferred can be selected. This facilitates the utilization of the invention e.g. in remote controllers in such a way that when the remote controller is set in a horizontal position it controls a device different from the device it would control if it were in vertical position. Alternatively, the polarizer placed in front of the transmitter can be of rotating type, in which case the direction of the polarizing axis is freely selectable.
- If the polarization axis of horizontal polarizer H1 (FIG. 3C) in front of transmitter element TX1 is not perfectly horizontal, or if the whole transmitter element TX1 is obliquely, it inflicts an angle error in the polarization axis of horizontally polarized infrared light LH. In this case the extinction of horizontally polarized infrared light LH is higher than in an ideal situation when it passes through horizontal polarizer H2. FIG. 3D presents a solution to correct this situation, in which solution horizontal polarizer H2 (FIG. 3C) in front of receiver element RX2 has been replaced with adjustable polarizer P1. It is possible to realize adjustable polarizer P1 e.g. by mounting a linear polarizer on receiver element RX2 in such a way that it can be rotated. This type of construction is prior known to a person skilled in the art e.g. from lens and filter systems used in photography. When polarized infrared light 11 having a certain polarization angle θ arrives at adjustable polarizer P1, part of polarized infrared light 11 passes through it. This part can be detected using
detector 12, and further as signal O2′ on the display of oscilloscope O2. By rotating adjustable polarizerP1 using knob 14, it is possible by observing signal O2′ to rotate adjustable polarizer P1 into such a position in which the intensity of signal O2′ is at maximum. Now the angle of polarization axis of polarizer P1 matches exactly polarization angle θ ofinfrared light 11, and the data transfer is less sensitive to external interference. - It is possible to realize the adjustment described in the previous section also automatically by providing receiver element RX2 with
processor 15 androtator motor 13.Processor 15 measures the level of the signal it receives fromdetector 12 e.g. using a level detector (not shown in the figure), based upon the data received from said detector,processor 15 controls motor 13 to rotate adjustable polarizer P1 into the optimal position. When the optimal position has been verified, it is possible to set receiver RX2 to monitor also another data transfer channel which has been realized using a 90° shifted polarization axis. This is realized by rotating polarizer P1 for 90°. A return to the original data transfer connection is made by rotating polarizer P1 another 90°. - FIG. 4 presents an embodiment of an infrared link according to the invention, in which simultaneous two-way (full-duplex) data transfer between two
terminal devices terminal device 10 comprises transmitter element TX1, receiver element RX2, vertical polarizer V1 and horizontal polarizer H1. Secondterminal device 20 has a similar construction, comprising transmitter element TX2, receiver element RX1, vertical polarizer V2 and horizontal polarizer H2. When sparse square wave S1′ is fed from signal generator S1 to transmitter element TX1 ofterminal device 10, the generated infrared light beam passes through polarizers V1 and V2 to receiver element RX1, from which it can be detected using oscilloscope O1. Horizontal polarizer H1 prevents horizontally polarized infrared light beam LH from entering receiver element RX2 ofterminal device 10, and in this way infrared light beam LV does not interfere in its operation. Simultaneously transmitter element TX2 ofterminal device 20 transmits dense square wave S2′ generated by signal generator S2 through horizontal polarizers H2 and H1 to receiver element RX2, from which dense square wave S2′ can be detected using oscilloscope O2. Vertical polarizer V2 prevents horizontally polarized infrared light beam LH from entering receiver element RX1 ofterminal device 20 and interfering in its operation. In this way, two-way data transfer betweenterminal devices -
- This means that when the polarization axes of the polarizers are perpendicular to each other, 5% of the light passes through the polarizers compared with the situation when the polarization axes are parallel. The longest operating distance of the test system was found to be over one meter. The extinction ratio of the polarizing sheets used in the tests k2/k1=25.0·10−3 is not the best possible. It is obvious that by choosing polarizers with a lower extinction ratio (for example thin film or crystal polarizers) and by using more powerful infrared transmitter elements, it is possible to increase the operating distance of the system significantly.
- FIG. 5 presents another embodiment of an infrared link according to the invention, in which transferring two independent signals S1′ and S2′ from
terminal device 30 toterminal device 40 has been realized. As components of the system the same components were used than in the embodiment of the two-way infrared link presented in connection with FIG. 4. The propagation of sparse square wave signal S1′ from transmitter element TX1 to receiver element RX1 is identical with the propagation presented in FIG. 4. Signal S2′, instead, is transferred to the opposite direction.Terminal device 30 comprises, in addition to transmitter element TX1, second transmitter element TX2, to which dense square wave signal S2′ is fed from signal generator S2. The infrared light signal transmitted by transmitter element TX2 is horizontally polarized in horizontal polarizer H1. Horizontally polarized infrared light LH propagates through horizontal polarizer H2 to receiver element RX2, from which the signal can be detected using oscilloscope O2. Consequently, linearly polarized infrared light beams LV and LH transmitted byterminal device 30 can be separated from each other in the infrared link according to the invention interminal device 40 using polarizers V2 and H2. It is because of this that it is possible to transfer two separate data signals S1′ and S2′ fromterminal device 30 toterminal device 40, or alternatively to double the data transfer rate available for a conventional infrared connection. - In the embodiments presented in FIGS. 4 and 5 infrared light beams LV and LH, having polarization axes perpendicular to each other, were formed and separated from each other using polarizers V1, V2, H1 and H2. It is possible to use beam splitters instead of polarizers V1, V2, H1 and H2. The basic purpose of a beam splitter is to divide a (infrared) light beam into two parts, both parts having equal amplitudes. In practice this means amplitude ratios from approximately 30/70 to 50/50, depending on the material the beam splitter is made of. One beam splitter suitable for infrared frequency range is a thin film made of polytetrafluorethylene (Mylar).
-
- If medium M1 is air, equation (4) is simplified (approximately) into form:
- θ≈arctan (n2)
- Variations in the vicinity of Brewster's angle are slow, thus the above described phenomena can be detected on a narrowish range around Brewster's angle.
- FIG. 7 presents an embodiment of an infrared link according to the invention, in which also two-way, simultaneous (full-duplex) data transfer has been realized. As a whole system, the operating principle is similar to that of the system presented in FIG. 4, but in the system in FIG. 7 beam splitters BS1 and BS2 are used instead of polarizers V1, V2, H1 and H2 for polarizing the infrared light and for separating the polarized infrared beams. Signal S1′ is transferred from transmitter element TX1 as an infrared signal to beam splitter BS1, in which the vertically polarized part LV of the infrared light passes through beam splitter BS1. If so wished, it is possible to install additional
vertical polarizer 51 between transmitter element TX1 and beam splitter BS1. However, it is not necessary, because due to the operating principle of beam splitter BS1 any horizontally polarized infrared light is reflected and is absorbed in the constructions ofdevice 50. For next, vertically polarized infrared light LV passes through beam splitter BS2, after which signal O1′ corresponding to signal S1′ can be detected in the display of oscilloscope O1. To the opposite direction information (signal S2′) is transferred using transmitter element TX2. After optionalhorizontal polarizer 61 the infrared beam meets beam splitter BS2, in which horizontally polarized infrared light beam LH is reflected. Any eventual vertically polarized infrared light passes through beam splitter BS2 and is absorbed in the constructions ofdevice 60. Reflected infrared light beam LH then meets beam splitter BS1, from which it is reflected to receiver element RX2 for detection. In this way the two-way infrared link according to the invention can also be realized using beam splitters BS1 and BS2. - FIG. 8 presents an embodiment of the infrared link according to the invention, in which also two-way data transfer, alike the one in FIG. 5, from
terminal device 70 toterminal device 80 has been realized. Alike in the solution presented in FIG. 7, polarizers V1, V2, H1 and H2 have been replaced with beam splitters BS1 and BS2.Terminal device 70 is equipped with two transmitter elements TX1 and TX2, through which infrared signals are directed at a beam splitter. The vertically polarized part of the infrared light beam emitted by transmitter element TX1 passes through beam splitters BS1 and BS2, while the horizontally polarized part of the infrared light beam emitted by transmitter element TX2 is reflected from both beam splitter BS1 and BS2 as presented in FIG. 8. Any other infrared light beams are absorbed in constructions (ref. 71). - An infrared link according to the invention is suitable for use e.g. in systems alike data transfer
systems 110 presented in FIG. 9, in which systems there is a need for two-way data transfer, such as data transfer betweenmobile station portable computer 118. As receiver- andtransmitter elements 118′, 119, 119′, 119″ it is possible to use e.g. transmitter/receiver elements TX1, TX2, RX1, and RX2 presented in connection with FIGS. 3A, 3B, 3C, 4, 5 and 7. An exemplary embodiment ofdata transfer system 110 according to the invention comprisesmobile stations telecommunication networks user terminals 117 connected to the networks either directly or over a terminal device. Indata transfer systems 110 according to the inventionmobile stations user terminals 117 are connected to each other throughtelecommunication networks mobile stations
Claims (10)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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FI965267 | 1996-12-30 | ||
FI965267A FI106332B (en) | 1996-12-30 | 1996-12-30 | Infrared link |
Publications (2)
Publication Number | Publication Date |
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US20010051505A1 true US20010051505A1 (en) | 2001-12-13 |
US6434363B2 US6434363B2 (en) | 2002-08-13 |
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US08/994,229 Expired - Fee Related US6434363B2 (en) | 1996-12-30 | 1997-12-19 | Infrared link |
Country Status (4)
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US (1) | US6434363B2 (en) |
AU (1) | AU5400898A (en) |
FI (1) | FI106332B (en) |
WO (1) | WO1998029973A1 (en) |
Cited By (2)
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US20160013882A1 (en) * | 2013-03-04 | 2016-01-14 | Nec Corporation | Transmission/reception device, optical space transmission system, and transmission/reception method |
US20210352257A1 (en) * | 2019-05-02 | 2021-11-11 | Disney Enterprises, Inc. | Illumination-based system for distributing immersive experience content in a multi-user environment |
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GB9825412D0 (en) * | 1998-11-19 | 1999-01-13 | Central Research Lab Ltd | A transceiver |
GB0000908D0 (en) * | 2000-01-14 | 2000-03-08 | Scient Generics Ltd | Parallel free-space optical communications |
FR2812981B1 (en) * | 2000-08-10 | 2002-10-18 | Alstom | PROTECTION FOR AN ELECTRICAL NETWORK HAVING AN INFRARED DATA TRANSMISSION LINK USING THE WAP PROTOCOL |
US6546345B1 (en) * | 2000-08-30 | 2003-04-08 | Sun Microsystems, Inc. | System and method for measuring extinction ratio and deterministic jitter |
US6678536B2 (en) * | 2000-12-07 | 2004-01-13 | Mark Wendell Fletcher | Wireless microphone |
US20030073431A1 (en) * | 2001-10-16 | 2003-04-17 | Jheroen Dorenbosch | Transferring communications over a network |
SG114535A1 (en) * | 2002-03-14 | 2005-09-28 | Agilent Technologies Inc | Optical transceiver for data transfer and control applications |
WO2009105115A2 (en) | 2008-02-22 | 2009-08-27 | T-Mobile Usa, Inc. | Data exchange initiated by tapping devices |
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US3600587A (en) * | 1969-06-10 | 1971-08-17 | Us Army | Frequency shift keying laser communication system |
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FR2641918B1 (en) * | 1988-12-28 | 1991-05-03 | Sgn Soc Gen Tech Nouvelle | DEVICE FOR INFRARED TRANSMISSION OF DATA PRESENTED IN ASYNCHRONOUS MODE |
JPH0321129A (en) * | 1989-06-19 | 1991-01-29 | Hitachi Ltd | Bidirectional optical communication system |
DE4026073A1 (en) * | 1990-08-17 | 1992-02-20 | Telefunken Systemtechnik | Control point coupling mobile data terminal to fixed data processor - has two components forming transceiver for electromagnetic waves, and air path as transmission line |
US5315645A (en) * | 1990-12-10 | 1994-05-24 | Tek Electronics Manufacturing Corporation | Communication apparatus utilizing digital optical signals |
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JPH05145496A (en) * | 1991-11-15 | 1993-06-11 | Canon Inc | Two-way optical transmitter |
FI109496B (en) | 1992-08-18 | 2002-08-15 | Nokia Corp | Apparatus and method for providing digital infrared communication between a base unit of a radiotelephone device and another device |
JPH06164518A (en) * | 1992-11-09 | 1994-06-10 | Sony Corp | Duplex transmission device |
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JP3303515B2 (en) * | 1994-03-18 | 2002-07-22 | キヤノン株式会社 | Optical communication system and optical communication system using the same |
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1996
- 1996-12-30 FI FI965267A patent/FI106332B/en not_active IP Right Cessation
-
1997
- 1997-12-19 US US08/994,229 patent/US6434363B2/en not_active Expired - Fee Related
- 1997-12-19 WO PCT/FI1997/000810 patent/WO1998029973A1/en active Application Filing
- 1997-12-19 AU AU54008/98A patent/AU5400898A/en not_active Abandoned
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
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US20160013882A1 (en) * | 2013-03-04 | 2016-01-14 | Nec Corporation | Transmission/reception device, optical space transmission system, and transmission/reception method |
US9705631B2 (en) * | 2013-03-04 | 2017-07-11 | Nec Corporation | Transmission/reception device, optical space transmission system, and transmission/reception method |
US20210352257A1 (en) * | 2019-05-02 | 2021-11-11 | Disney Enterprises, Inc. | Illumination-based system for distributing immersive experience content in a multi-user environment |
US11936842B2 (en) * | 2019-05-02 | 2024-03-19 | Disney Enterprises, Inc. | Illumination-based system for distributing immersive experience content in a multi-user environment |
Also Published As
Publication number | Publication date |
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WO1998029973A1 (en) | 1998-07-09 |
US6434363B2 (en) | 2002-08-13 |
AU5400898A (en) | 1998-07-31 |
FI106332B (en) | 2001-01-15 |
FI965267A0 (en) | 1996-12-30 |
FI965267A (en) | 1998-07-01 |
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