US20090026358A1 - Position Sensor - Google Patents

Abstract

A hinge position sensor comprises first and second members connected together to provide a hinge, and an optical fibre or wave-guide connected between the first and second members to provide a communication link between the first and second members. A laser or LED is coupled to the optical fibre or wave-guide to transmit optical signals between the first and second members and the optical signal is received by a photo-detector. The optical fibre or wave-guide is physically distorted by actuation of the hinge such that light escapes from the optical fibre or wave-guide. The optical power level received by the photo-detector is used to determine the position of the hinge.

Description

CROSS REFERENCE TO RELATED APPLICATION(S)
• This application is a divisional application of co-pending U.S. Non-Provisional Application No. 11/423,927, filed Jun. 13, 2006, entitled “Position Sensor”, the disclosure of which is expressly incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
• The present invention relates to an optical position sensor, particularly, but not exclusively, to a fibre optic position sensor for sensing the position of a hinged lid of a portable electronic device such as a mobile telephone or a lap-top computer.
BACKGROUND TO THE INVENTION
• It is common for a portable electronic device such as a lap-top computer or a mobile telephone to comprise a base, which includes the device's keypad, and a lid, which includes the device's screen or user display. In this type of device, the base and the lid are connected together by a hinge section such that the user display can be hinged to lie flat against the keypad when the device is not in use. By detecting when the hinge is closed, the device is able to detect when it may safely switch to a power-saving mode. This function allows the device to conserve battery power when the device is not in use.
• It is known to detect the open/closed state of this type of hinge using a mechanical sensor, such as a boss-type media detection switch or a rotary-type position detection switch. However, the use of a mechanical sensor often imposes design constraints on the electronic device and may also require that bosses be fitted to the device's exterior. A mechanical sensor often also requires extra space on the motherboard of the device for the inclusion of a detector switch.
• Alternatively, the position of the hinge may be detected using a solid-state relay. For example, it is known to magnetically detect the position of a lid with a system employing a Hall Integrated Circuit. However, this type of detector requires both space on the motherboard of the device and a level of standby power. In addition, magnetic switches of this type are liable to interfere with other types of sensor which may be integrated into the device, such as those employed by global positioning systems.
• The use of optical proximity sensors is also known. However the surfaces of a proximity sensor's emitter and receiver must be kept clean in order for the sensor to function reliably.
SUMMARY OF THE INVENTION
• According to the present invention, there is provided a hinge-position detection apparatus comprising a first member and a second member rotationally connected to one another so as to provide a hinge, a first optical fibre, a light emitter to transmit light through the optical fibre and a light detector to detect a power level of light emitted from the optical fibre, wherein the optical fibre is physically distorted by actuation of the hinge and the detected power level is used to determine the position of the hinge.
• Preferably, a physical distortion in the optical fibre causes light to escape from the optical fibre and affects the optical power level detected by the light detector.
• Preferably, the optical fibre is connected between the first member and the second member so as to traverse the hinge.
• Preferably, the determined position of the hinge is used to control the operation of an electronic device.
• More preferably, if the hinge is determined to be in a closed position, the apparatus is configured to switch one or more components of an electronic device to a power saving mode.
• Preferably, the hinge is determined to be in a closed position if the detected optical power level reaches a predetermined threshold level.
• Preferably, the light emitter is included in the first member, the light detector is included in the second member and the optical fibre is coupled between the light emitter and the light detector.
• Preferably, the light detector is positioned to directly detect the emission of light from the optical fibre, the emission of light being caused by a physical distortion in the fibre.
• More preferably, the apparatus includes a further optical fibre operable to direct the emission of light from the optical fibre to the detector.
• Preferably, the light emitter comprises an LED or a laser, and the light detector comprises a photo-sensitive device, such as a photo-diode, photo-transistor or photo-resistor.
BRIEF DESCRIPTION OF DRAWINGS
• In order that the invention may be more fully understood, embodiments thereof will now be described by way of illustrative example with reference to the accompanying drawings in which:
• FIG. 1 is an illustration of a mobile telephone handset comprising a base and a lid connected together by a hinge joint.
• FIG. 2 is a block diagram illustrating components of the handset shown inFIG. 1.
• FIG. 3 is cross-sectional illustration of an optical fibre traversing the hinge joint of the handset.
• FIG. 4 is a cross-sectional illustration showing the coupling of the optical fibre between a laser and photo-diode.
• FIG. 5 is a cross-sectional illustration showing the escape of light from the optical fibre.
• FIG. 6 is an illustration of the direct detection of light escaping from the optical fibre.
• FIG. 7 is an illustration showing the direct detection of light escaping from the optical fibre via a second optical fibre.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• Referring toFIG. 1, a hinge position detection apparatus is part of amobile telephone handset11. Themobile telephone handset11 comprises a first member in the form of abase12 and a second member in the form of alid13. Thebase12 andlid13 are connected together by ahinge joint14, allowing thehandset11 to be movable between a closed position and an open position.
• Thetelephone handset11 is configured to operate in a cellular radio network, such as a GSM network, although it could be configured for use with other networks such as a 3G network or I-mode.
• Thetelephone handset11 is provided with auser display15, for example in the form of a liquid crystal display (LCD) panel. Thehandset11 is additionally provided with aloudspeaker16, which is located in thelid13 and is on the same surface as the user display15. Thebase12 of thehandset11 houses the remainder of the telephone's principal components, including akeypad17.
• Thekeypad17 is located on the surface of thebase12 such that, when thehinge joint14 is in the closed position, thekeypad17 directly faces theuser display15. Thus, theuser display15 andkeypad17 are not visible to the user when thehinge14 is closed. Anantenna18 is located inside thebase12 such that it does not form part of the handset's exterior.
• Referring toFIG. 2, in addition to theuser display15, theloudspeaker16, thekeypad17 and theantenna18, thehandset11 comprises amicrophone21, aSIM card22, aSIM card reader23,amplifiers24 and25, anrf subsystem26, acodec27, a micro-controller28 and amemory29.
• Therf subsystem26 contains the circuits of the telephone's transmitter and receiver. Therf subsystem26 is coupled to theantenna18 for the reception and transmission of radio signals in a cellular mobile network.
• Theantenna18 is connected through therf subsystem26 to thecodec27, which is configured to process signals under the control of the micro-controller28.
• The micro-controller28 operates according to a program stored in thememory29 and controls the operation of thehandset11. It is coupled to therf subsystem26 for supplying tuning instructions to a frequency synthesizer.
• Theuser display15 is connected to the micro-controller28 for receiving control data and thekeypad17 is connected to the micro-controller28 for supplying user input data. InFIG. 2, thememory29 is shown separately from the micro-controller28. However, thememory29 and thecontroller28 may also be included together in an integrated unit.
• Theamplifier24 amplifies demodulated audio from thecodec27 and applies it to theloudspeaker16. Acoustic signals, detected by themicrophone21, are pre-amplified by theamplifier25 and sent to thecodec27 for coding.
• Information concerning the identity of the user is held on thesmart card22 in the form of a GSM SIM card which contains the usual GSM international mobile subscriber identity (IMSI) and an encryption key K_ithat is used for encoding the radio transmission in a manner that is well known. The SIM card is removably received in theSIM card reader23.
• Referring toFIG. 3, thehandset11 further comprises an optical wave-guide, for example anoptical fibre31, which is connected between thebase12 and thelid13 via thehinge joint14. Theoptical fibre31 is connected so as to provide a transmission medium for optical communication between electronic circuits located in thebase12 and thelid13.
• Referring toFIG. 4, thebase12 of thehandset11 further includes a light emitter, for example alaser41, which is adapted to emit red laser light in the wavelength range 630-670 nanometres. However, other suitable wavelengths could also be used. Thelaser41 is coupled to the base-end of theoptical fibre31 and, as such, light emitted from thelaser41 enters theoptical fibre31 and is transmitted to thelid13. The term “light” is used herein to mean electromagnetic radiation in the visible, infra-red and ultraviolet spectrum.
• Theoptical fibre31 comprises acentral core31asurrounded by acladding layer31b.The refractive index of the core31ais of a different refractive index to that of thecladding31b,meaning that light is confined to the core31aby total internal reflection and is guided along theoptical fibre31. Theoptical fibre31 may be either a graded optical fibre or a step-index optical fibre. The light transmitted through theoptical fibre31 may carry, for example, signals for controlling the operation of theuser display15 orloudspeaker16. Alternatively, light transmitted through theoptical fibre31 may comprise control data for illumination at the lid side of thehandset11. In an alternative embodiment, thelaser41 could be replaced by a light-emitted diode (LED).
• Further referring toFIG. 4, thelid13 of thehandset11 includes a light detector, for example a photo-diode42, which is coupled to the lid-end of theoptical fibre31. The photo-diode42 is adapted to detect light transmitted through thefibre31 from thelaser41 and is coupled to electronic circuits located in thelid13 of thehandset11. Alternatively, instead of the photo-diode42, the handset may comprise another type of photo-sensitive device such as a photo-transistor or photo-resistor.
• Theoptical fibre31 is fabricated from suitable plastics and is flexible in such a way that it is able to bend with thehinge joint14 of thetelephone handset11. The use of plastics allows theoptical fibre31 to be adapted such that it may be bent to a very small radius. This is convenient as theoptical fibre31 should be able to comfortably bend to a radius enabling it to traverse the hinge joint14 when thehandset11 in the closed position. The use of plastics also provides advantages in terms of transmission speed and is inexpensive in comparison to alternative materials. However, it will be appreciated that materials other than plastics can be used.
• Referring toFIG. 5, as theoptical fibre31 is bent to the a radius enabling it to traverse the hinge joint14 in the closed position of thehandset11, some of the light being transmitted through thefibre31 does not meet the conditions for total internal reflection within thefibre31 at the bend. The light which does not meet the conditions for total internal reflection escapes from thefibre31, as illustrated schematically inFIG. 5 by arrows A. In consequence, the light not meeting the conditions for total internal reflection is not detected by the photo-diode42. As the radius of the bend decreases, as thelid13 is hinged to the closed position on thebase12, the amount of light escaping from theoptical fibre31 increases. Accordingly, for an optical signal of constant power transmitted from thelaser41, the optical power detected by the photo-diode42 is a function of the radius of the bend in theoptical fibre31 and, therefore, is also a function of the position of the hinge joint14.
• The optical power detected at thephotodiode42 can be used to calculate the position of the hinge joint14. Information concerning the position of the hinge joint14 may then be processed to determine whether thehandset11 is open or closed and, accordingly, may be used to control the operational mode of thehandset11.
• As shown inFIG. 3, thelaser41 and the photo-diode42 are coupled to thecontroller28, which is adapted to control the operational mode of the components of thehandset11 in dependence of the optical power level detected by the photo-diode42. These components may include, for example, theuser display15 andloudspeaker16. Accordingly, if the optical power level detected by the photo-diode42 falls below a predetermined threshold, the handset is determined to be closed and the operational mode of thelid13 is switched to a power-saving mode. Alternatively, the optical power level may be used to monitor the precise angle of the hinge and may be used for more complex control of thehandset11.
• In an alternative embodiment, thelaser41 is comprised as part of thelid13 and is coupled to the lid-end of theoptical fibre31. In this embodiment, the photo-diode42 is comprised as part of the base and is coupled to the base-end of theoptical fibre31. Light transmitted through theoptical fibre31 may carry control signals for controlling the operation of thehandset11. Theuser display15 may be a touch-sensitive display and may be operated by a user to select menu options from the display for operating thehandset11. Accordingly, the control signals transmitted through theoptical fibre31 may comprise, for example, information concerning a menu option selected by a user touching thedisplay15. This information may then be relayed to themicro-controller28 and used for controlling the operation of thehandset11.
• The photo-diode42 is configured to detect the optical power received from thelaser41. Information concerning the optical power level detected at the base-end of theoptical fibre31 by the photo-diode42 is supplied to themicro-controller28 for controlling the operational mode of thehandset11. If the detected optical power level falls below the predetermined threshold value previously described, thehandset11 is determined to be closed and themicro-controller28 switches the operational mode of thehandset11 to a power-saving mode. Alternatively, optical power level information supplied by the photo-diode42 may be processed to control the operation of one or more components of thehandset11 directly.
• Therefore, the optical power level detected by the photo-diode42 is compared against a predetermined threshold value in order to determine whether thehandset11 is in the open or closed position. If thehandset11 is determined by the hinge-position detection apparatus to be in a closed position, the components of thehandset11 are configured to operate in a power saving mode. Thehandset11 is thus able to increase the efficiency of its use of power and, accordingly, is able extend the standby time provided by a single charge of its battery (not shown).
• Referring toFIG. 6, in an alternative embodiment, a second light detector, for example asecond photodiode61, is located in thehinge joint14 of thehandset11 to detect light escaping from theoptical fibre31. Thesecond photodiode61 is positioned in the area of maximum light emission from the bend in theoptical fibre31 to maximise the efficiency of detection of the light escaping from thefibre31.
• Thesecond photodiode61 is coupled to themicro-controller28 such that information concerning the power of the optical light escaping from thefibre31 may be relayed back to thecontroller28 and processed to determine whether thehandset11 is in the open or closed position. Alternatively, thephotodiode61 may be configured to communicate the detected power level back to thecontroller28 by wireless means, for example via a Bluetooth connection. In contrast with the previously described embodiments of the invention, the optical power level detected by the photo-diode61 is inversely proportional to the radius of the hinge joint14; as the radius of the bend in theoptical fibre31 decreases, the optical power level detected by the photo-diode61 increases. By sensing the emitted light directly, the apparatus is able minimise the effect of errors due to losses caused by temperature fluctuations and aging of theoptical fibre31. In addition to determining whether the hinge joint14 is open or closed, the relationship between the power level detected by the photo-diode61 and the radius in the bend of theoptical fibre31 may be used to provide detailed information regarding the position of the hinge joint14. For example, the optical power level detected by the photo-diode61 may be used for calculating the angle of the hinge joint14.
• Alternatively, instead of the second photo-diode61, the handset may comprise a different type of photo-sensitive device such as a photo-transistor or photo-resistor.
• Thecontroller28 processes the optical power level information supplied by the photo-diode61 to control the operational mode of thehandset11. If the optical power level detected by the photo-diode61 increases above a predetermined threshold value, thehandset11 is determined to be closed and themicro-controller28 switches the operational mode of thehandset11 to a power saving mode. Alternatively, the optical power level detected by the photo-diode61 may be used to control the operational mode of one or more individual components of thehandset11 directly.
• Referring toFIG. 7, in an alternative embodiment, the second photo-diode61 is comprised as part of thebase12 of thehandset11 and a second optical wave-guide, for example a secondoptical fibre71, is positioned to receive light escaping from the bend in the firstoptical fibre31 and to direct the light. Alternatively, instead of the secondoptical fibre71, the handset may comprise alternative means for directing the light. The alternative means may comprise, for example, a light pipe comprising a length of plastic without cladding in which the plastic/air interface confines light to the light pipe. Theoptical fibre71, optical wave-guide or light pipe may be used either with or without a light-collectingapparatus72, for example comprising lenses, for collecting light escaping from theoptical fibre31.
• The light inlet to theoptical fibre71 is positioned adjacent to the point of maximum emission of the firstoptical fibre31 during bending thereof. The optical power level detected by the photo-diode61 is used, either by thecontroller28 or directly, to control the operational mode of thehandset11. If the optical power level detected by the photo-diode61 increases above a predetermined threshold, thehandset11 is determined to be closed and thehandset11 is switched to a power saving mode.
• The inclusion of the secondoptical fibre71 provides more flexibility in the design of thehandset11 as the position of the second photo-diode61 is not dictated by the position of maximum light emission from the firstoptical fibre31. Accordingly, the photo-diode61 may be positioned at a convenient position in thebase12 of thehandset11. Alternatively, the photo-diode61 may be positioned in thelid13 of thehandset11.
• Theoptical fibre31 may be surrounded by a protective jacket (not shown). In the described embodiments where light escaping from the bend in thefibre31 is detected directly, if an LED is used instead of thelaser41, the jacket is removed at the point of maximum emission in order to allow the photo-diode61 to detect the power level of the light escaping from thefibre31. However, if thelaser41 is used as described, the protective jacket may be adapted such that the laser light is partially transmitted through the jacket. In this case, there is no need to remove the jacket in order for the photo-diode61 to detect the light.
• The control of the operational mode of thehandset11 has been described as being dependent on a detected power level of light at a photo-diode. However, the control of the handset could equally be dependent on a calculated signal-loss.
• The implementation of the described hinge position detection apparatus involves minimal adaptation of the hardware of thehandset11. The components used for detection of the hinge's position are largely already present in many otherwise conventional mobile telephone handsets. Furthermore, apart from theoptical fibre31, no moving parts are used and, thus, the hinge-position detection apparatus can be considered to be extremely reliable. The hinge-position detection apparatus is not sensitive to electric or magnetic fields and will also not interfere with surrounding equipment, for example a GPS system, making use of such fields.
• The above-described embodiments and alternatives may be used either singly or in combination to achieve the effects provided by the hinge-position detection apparatus. Although the hinge-position detection apparatus has been described with reference to amobile telephone handset11, the system is equally applicable to other types of electronic device which include a hinge section. These types of device include, for example, hand-held and lap-top computers, hand-held video games and personal digital assistants.

Claims (19)

1. An apparatus comprising:

a first member and a second member connected together to provide a pivoting joint;

an optical wave-guide;

a processor;

a light emitter to transmit an optical signal through the optical wave-guide; and

a light detector to detect the optical signal from the optical wave-guide;

wherein the processor is configured to process the detected signal to determine the signal-loss through the optical wave-guide and to use the determined signal-loss to determine the position of the joint.

2. An apparatus according toclaim 1, wherein the processor is configured to use the determined position of the joint to control the implementation of a power saving mode in the apparatus.

3. An apparatus according toclaim 2, wherein if the determined signal-loss increases above a predetermined threshold, the joint is determined to be closed.

4. An apparatus according toclaim 2, wherein if the determined signal-loss falls below a predetermined threshold, the joint is determined to be open.

5. An apparatus according toclaim 1, wherein the optical wave-guide comprises an optical fiber.

6. An apparatus according toclaim 1 comprising a mobile telephone.

7. An apparatus comprising:

a lid and a base;

a light emitter to transmit optical signals;

a light detector for detecting the power level of optical signals; and

an optical wave-guide;

wherein the optical wave-guide is coupled to the light emitter and is connected between the lid and the base to provide a transmission medium for the optical signals, wherein the apparatus is configured to use the optical power level detected by the light detector to determine the position of the lid relative to the base, and wherein the apparatus is configured to use the position of the lid to employ a power-saving mode in the apparatus.

8. The apparatus according toclaim 7, wherein the optical wave-guide comprises an optical fiber.

9. The apparatus according toclaim 7, wherein if a determined signal-loss detected by the light detector increases above a predetermined threshold, the lid is determined to be closed.

10. The apparatus according toclaim 7, wherein if a determined signal-loss detected by the light detector falls below a predetermined threshold, the lid is determined to be open.

11. A method comprising:

transmitting an optical signal through an optical wave-guide;

detecting an optical power level of an optical signal from the optical wave guide;

determining the position of a lid of an apparatus relative to a base of the apparatus using the detected optical power level;

employing a power saving mode in the apparatus based on the determined position of the lid of the apparatus.

12. The method ofclaim 11, wherein transmitting comprises transmitting the optical signal through an optical fiber.

13. An apparatus comprising:

means for transmitting an optical signal through an optical wave-guide;

means for detecting an optical power level of an optical signal from the optical wave-guide;

means for determining the position of a lid of an apparatus relative to a base of the apparatus using the detected optical power level;

means for employing a power saving mode in the apparatus based on the determined position of the lid of the apparatus.

14. The apparatus ofclaim 13, wherein the optical wave-guide comprises an optical fiber.

15. One or more computer readable media storing machine-readable instructions which, when executed by a computer apparatus, control the computer apparatus to perform a method comprising:

determining the position of a lid of an apparatus relative to a base of the apparatus using a detected optical power level of an optical signal from an optical wave-guide;

employing a power saving mode in the apparatus based on the determined position of the lid of the apparatus.

16. The computer readable media ofclaim 15, wherein the optical wave guide comprises an optical fiber.

17. The computer readable media ofclaim 15, wherein the detected optical power level comprises a signal loss detected by a light detector that detects the optical signal from the optical wave-guide.

18. The computer readable media ofclaim 17, wherein if the detected signal loss increases above a predetermined threshold, the lid is determined to be closed.

19. The computer readable media ofclaim 17, wherein if the detected signal loss decreased below a predetermined threshold, the lid is determined to be closed.

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