DEVICE FOR INDICATING A POSITION

Abstract: The invention relates to a device for indicating a position, a sensor supplying an electrical signal in dependence of the position of the device relative to a reference. According to the invention, the device is characterized in that it is provided with capacitors (C1, C2, C3, C4) which have fixed electrode plates (2, 11, 12, 13, 14) between which a common space (3) is present, while a body (4) of a dielectric material is present in the space (3) and is capable of moving in the space (3), so that the position can be derived from the location of the body (4) with respect to the electrode plates (2, 11, 12, 13, 14) of the individual capacitors (C1, C2, C3, C4). The capacitance values of the individual capacitors (C1, C2, C3, C4) vary as a function of the location of the body (4) in the space (3) between the electrode plates (2, 11, 12, 13, 14).

Description: Device for indicating a position. The invention relates to a device for indicating a position. Such a device comprises a sensor which supplies an electric signal depending on the position of the device with respect to a reference. Such a device may be provided with various types of sensors. It is thus possible to use small coils as the sensors, which give a signal in dependence on a reference magnetic field, or to use photosensitive sensors which give a signal in dependence on their position relative to a reference light source. A device of the kind mentioned in the opening paragraph is known from US Patent No. 5,440,326. The known device is a pointing device in which the position relative to a gyroscope, which is used as a reference, is measured by means of an electro- optical sensor. The known device described has the disadvantage that its construction is mechanically intricate because of the use of a gyroscope. The invention has for its object inter alia to counteract said disadvantage. According to the invention, the device is for this purpose characterized in that the device is provided with capacitors which comprise fixed electrode plates between which a common space is present, a body of a dielectric material being arranged in said space and being capable of moving in said space such that the position can be derived from the location of the body in relation to electrode plates of different capacitors. The device according to the invention accordingly comprises a number of capacitors whose capacitance values can be electrically read out. The capacitance values of the various capacitors vary in dependence on the location of the body in the space between the electrode plates. This is because the capacitance value of a capacitor is influenced by the presence of a dielectric body between the electrode plates of this capacitor. The body of dielectric material is capable of moving in the space between the electrode plates, for example when the device is pivoted under the influence of the force of gravity, or when acceleration forces are exerted on the device. Depending on the position of the device, accordingly, the body will be present to a greater or lesser extent between the electrode plates of a given capacitor. The capacitance values of the different capacitors thus provide information on the position of the device. Any location of the body may be chosen to be the reference. The actual location is then determined in relation to this reference location. The values of the capacitances of the various capacitors can be measured electrically in a simple manner. The device according to the invention is easy to manufacture as a microsystem, for example by means of techniques known from semiconductor manufacture, but alternatively also as a macrosystem. Preferably, the device is characterized in that the capacitors comprise a common first electrode plate and individual second electrode plates which are arranged symmetrically around the center of the space. Reading and processing of the measured capacitance values of the capacitors of such a device are simple. In an advantageous embodiment, the space is filled with a liquid. The liquid damps movements of the body so that a quieter signal is obtained under circumstances with, for example, many vibrations. In addition, a liquid reduces the adhesion of the body to walls of the space, so that the risk of errors owing to, for example, stick-slip effects is reduced. The body of dielectric material and the space may be shaped so as to obtain a desired sensitivity for certain positions. Preferably, the space has a rectangular box shape and the body has a cylindrical shape. The risk of the body getting stuck in corners of the space is very small then. The sensitivity of the device to the change in the capacitance values of the capacitors may be increased in that a body having a high dielectric constant is chosen. Preferably, the body comprises a material having a dielectric constant higher than 800. The use of a body having such a high dielectric constant leads to a comparatively high sensitivity of the device. The body may be so provided that it can move freely in the space. Preferably, the space comprises a preferred location for the dielectric body. According to the invention, at least one of the electrode plates in the device is then provided with a depression which serves as a preferred location for the body. The body, for example, fits into the depression then. It is also possible, according to the invention, that the body is held in a preferred location by means of a spring. When no external forces are exerted on the body any more in the latter case, the body can return into a starting position again as defined by the spring. In an advantageous embodiment, the device comprises a mechanism for applying a voltage to all electrode plates such that the dielectric body can be brought into a preferred location by electrostatic means. The application of a voltage to the electrode plates is capable of influencing the location of the dielectric body. If the capacitors are symmetrically arranged around a center, for example, an equal, sufficiently high voltage applied to all capacitors will result in the dielectric body moving into the center. The mechanism for applying a voltage to all capacitors may also be used for realizing an electrostatic feedback. The dielectric body, for example, is then held in a central location by a certain voltage at all capacitors. When a force is exerted on the body now, this body will tend to displace itself. This displacement can be prevented in that a suitable voltage is applied to certain capacitors. The body then remains in position. The additional voltage necessary for this is detected and is a measure for the force which has occurred and for the position which the body would have occupied owing to this force without the electrostatic feedback. The capacitors may be provided in the device in the form of a separate measuring unit (sensor). Preferably, the device comprises a substrate on which both the capacitors and an electronic circuit for reading out or processing electrical signals obtained through the capacitors are provided. A substrate is present in that case, for example a printed circuit board or a silicon wafer, on which electronic units are provided for processing or reading of electrical signals which are influenced by the capacitance values of the capacitors, i.e. the position of the device, or the orientation of the body in the space. The device according to the invention may be used for measuring the position of an appliance relative to gravity. Thus, for example, the device according to the invention may be mounted in a car, for example with the electrode plates of the capacitor parallel to a bottom of the car. The orientation of the car can then be measured. The dielectric body will displace itself in its space if the car is pivoted owing to braking or owing to an overhang of the car in bends. The displacement of the body results in a different location of the body. This location can be derived from the measured capacitance values of the capacitors. The derived location may then be used, for example, for adapting the height of the car locally, so that the car overhang can be compensated for. It is also possible by means of the device according to the invention to detect whether the device has been subject to accelerations. The body of dielectric material will move to a different location when the device experiences an acceleration. This change in location can be read out. The invention also relates to a remote control device called pointing device which is provided with an arrangement for indicating a position by means of capacitors which comprise fixed electrode plates within which a common space is present, a body of a dielectric material being arranged in the space and being free to move in the space, so that the position can be derived from the location of the body relative to the electrode plates of individual capacitors. The remote control device is used, for example, with the electrode plates perpendicular to the direction of the force of gravity. The dielectric body is displaced in the space when the remote control device is pivoted. The location of the dielectric body is changed thereby. This change is read out in the form of the change of capacitance values of the capacitors. The change in location is subsequently, possibly after electronic processing, supplied to an electronic unit, for example via a bus system, for example to a TV, computer, or other interactive device. The location of the dielectric body is then translated into, for example, the position of a cursor on a screen or an option from a menu. When the remote control device is pivoted, the location of the dielectric body changes once more, so that, for example, the cursor position or menu option is also changed. The remote control device according to the invention can be given a very simple and robust construction. The invention will be explained in more detail below by way of example with reference to drawings, in which: Fig. 1 is a plan view of a first embodiment of a device according to the invention, Fig. 2 is a cross-section taken on the line A- A' in Fig. 1 of a device according to the invention, Fig. 3 is a plan view of a second embodiment of a device according to the invention, Fig. 4 is a cross-section taken on the line A-A' in Fig. 3 of a device according to the invention, Fig. 5 is a cross-section of a third embodiment of a device according to the invention, Fig. 6 is a cross-section of a fourth embodiment of a device according to the invention, and Fig. 7 is a remote control device provided with a device with capacitors according to the invention. The Figures are purely diagrammatic and not drawn true to scale. Corresponding parts have generally been given the same reference numerals in the Figures. Fig. 1 is a plan view and Fig. 2 a cross-section of a device for indicating a position. Such a device comprises a sensor 1 which supplies an electrical signal in dependence on the position of the device in space. The device according to the invention is provided with capacitors Cl, C2, C3, C4 which comprise fixed electrode plates 2, 11, 12, 13, 14. A common space 3 is bounded by the electrode plates 2, 11, 12, 13, 14. A body 4 of a dielectric material is present in the space 3 and capable of moving the space 3. The position can be derived from the location of the body 4 relative to the electrode plates 2, 11, 12, 13, 14 of individual capacitors Cl, C2, C3, C4. In the device according to Figs. 1 and 2, the capacitors Cl, C2, C3 and C4 have a common first electrode plate 2 and individual second electrode plates 11, 12, 13, 14 which are symmetrically arranged around the center of the space 3. Reading out and processing of the measured capacitance values of the capacitors of such a device are simple operations. In the situation as shown in Figs. 1 and 2, with the body 4 in the center of the space 3, all capacitors Cl, C2, C3 and C4 will have the same capacitance value. If the body 4 is displaced, for example owing to pivoting of the device, for example over line A-A' in the direction of location A, the capacitance value of C3 will increase and the capacitance values of Cl, C2 and C4 will decrease. The changes in the capacitance values of the capacitors Cl, C2, C3 and C4 thus provide an indication of the location of the body 4 in the space 3. The space 3 in this embodiment has a rectangular box shape while the body 4 is cylindrical. The risk of the body 4 getting stuck in corners of the space 3 is very small then. The device according to the invention can be manufactured in a simple manner. In this first embodiment, a printed circuit board 5 provided with a 35 μm thick copper layer 2 is used as the first electrode plate 2. This printed circuit board is provided with a 10 μm thick insulating glue layer 6 by a standard photolithographic technique. This layer serves for insulation and for fixing the first electrode plate relative to the second electrode plates 11, 12, 13, 14. The second electrode plates are manufactured from copper plates with a thickness of 35 μm. The space 3 is provided in the copper plates in that the copper plates are depressed 20 μm by means of a punch. The space 3 then has a height 7 of 30 μm (thickness of insulating layer 6 plus depression depth of copper plates). The lateral dimensions of the space 3 in this example are 5 x 5 mm. A body 4 of lead-zirconium titanate (PZT) is present in the space. PZT has a dielectric constant e of approximately 1000. This body 4 is etched from a PZT plate in a photolithographic process. The diameter and thickness of the body 4 are 25 mm and 20 μm. The electrode plates 11, 12, 13, 14 are glued onto the insulating layer 6. The electrode plates are connected in a standard manner, for example by means of bonding wires or conductor tracks and solder on the printed circuit board. The device is closed off with a standard cover. The device according to the invention is thus comparatively easy to manufacture by standard techniques. Figs. 3 and 4 show a second embodiment. In this example, the space comprises a preferred location for the dielectric body. The body is suspended to four springs 15 for this purpose. These springs comprise a meander structure in a 10 μm thick copper foil. The springs were manufactured in that a copper foil was brought into a pattern in an etching process. The springs are fastened to the substrate 5 and to the body 4 by means of a glue 16. The arrangement of the device in this second embodiment is largely identical to the arrangement of the first embodiment. Holes have merely been provided in the electrode plates where the springs are passed through the electrode plates. The body has been given a preferred location in the center of the space by means of the springs 15. Fig. 5 shows a third embodiment where the space again comprises a preferred location for the body. This third embodiment again is largely identical to the first embodiment, but here the lower electrode plate 2 is differently shaped. A depression in which the body 4 fits has been provided in the electrode plate 2. The height of the space is approximately 300 μm at the area of the depression, whereas it is 30 μm at the area of an outer side of the electrode plate. The electrode plate accordingly has a tapering shape. The body will have a preference for the depression owing to this shape. A fourth embodiment is shown in Fig. 5. This embodiment is manufactured by techniques as used in the semiconductor industry (IC technology). The electrode plates 2, 11, 12, 13, 14 and the body 4 are constructed as comparatively thin layers on a substrate 5. The device in this example comprises a silicon substrate 5. This substrate is given an insulating layer 8 of silicon oxide. A 2 μm thick TiPtAu layer 2 is provided on this substrate 5 by means of a standard sputtering technique and is patterned by means of standard photolithographic and etching techniques. The TiPtAu layer forms the first electrode plate 2. The dielectric body 4 is made from PZT, and the insulating layer 6 from silicon nitride. The second electrode plates 11, 12, 13 and 14 are also made from TiPtAu. The freely movable body 4 is manufactured in a known manner by means of so-called sacrificial layers. The body 4 is completely surrounded during manufacture by layers which can be preferentially etched relative to the material of the body 4. Silicon oxide is used for the sacrificial layer in this example. This silicon oxide can be etched away preferentially relative to silicon nitride, PZT, and TiPtAu. The silicon oxide layer 8 is covered while the sacrificial layers are being etched. A thin layer of silicon oxide is first provided on the electrode plate 2 during manufacture of the device, whereupon the body 4 is provided in that a layer of PZT is applied and patterned. The layer of PZT may be provided in a known manner by means of sol-gel techniques. Holes 9 are provided in the body 4. The body 4 is then covered in a standard manner with a planarizing layer of silicon oxide, after which a pattern is provided in this silicon oxide. The silicon oxide remains at the area of the space in this example. Then the second electrode plates 11, 12, 13, 14 are provided. These electrode plates are provided with the holes 9. Then the silicon oxide layer is etched away at the area of the space by means of HF. The etching liquid is capable of reaching the sacrificial layers around the body 4 comparatively easily through the holes 9 in the second electrode plates 11, 12, 13, 14 and through the holes 9 in the body 4 and of etching them away. A device is created thereby having a space with dimensions 500 x 500 x 3 μm. The body 4 has a diameter and height of 250 and 2 μm, respectively. Aluminum connection plugs 20, 110, 120, 130, 140 are provided on the first electrode plate 2 and on the second electrode plates 11, 12, 13, 14. The space 3 in this embodiment is filled with a liquid 10, in this example a silicone oil. The liquid 10 damps movements of the body 4, so that changes in the capacitance values take place less abruptly. In addition, the liquid reduces the adhesion between the body 4 and walls of the space 3, so that the risk of errors caused by, for example, stick-slip effects is reduced. This fourth embodiment of the device has the advantage that the device can be manufactured with comparatively small dimensions and with a high accuracy by means of standard techniques. Fig. 7 shows a remote control device or pointing device provided with a device 1 for indicating a position, having capacitors Cl, C2, C3, C4 with fixed electrode plates 2, 11, 12, 13, 14 between which a common space 3 is present, while a body 4 of a dielectric material is present in the space 3 and capable of movement in the space 3, so that the position can be derived from the location of the body 4 relative to the electrode plates 2, 11, 12, 13, 14 of the individual capacitors Cl, C2, C3, C4. The remote control device is accordingly provided with a sensor which measures the location of the dielectric body 4. The remote control device is then used, for example, with the electrode plates 2, 11, 12, 13, 14 perpendicular to the direction of the force of gravity. Tilting of the remote control device will displace the dielectric body 4 in the space 3. The location of the dielectric body 4 is changed thereby. This change is read out in the form of a change in the capacitance values of the capacitors Cl, C2, C3, C4. These changes are processed by a processing unit 15 into a signal 16 which corresponds to a signal indicating up, down, left, or right. This signal 16 is transmitted in a standard manner to a computer 17 by means of infrared radiation. The location of the dielectric body 4 is then translated into the position of a cursor on a computer screen. The remote control device thus acts as a replacement of a mouse. Tilting of the remote control device changes the position of the cursor on the computer screen. The remote control device according to the invention can be manufactured with a very simple and robust construction. The invention is not limited to the embodiments described above; variations are possible within the scope of the invention. Four capacitors Cl, C2, C3, C4 were used in the embodiments. It is possible to use a different number of capacitors. Two capacitors are used in the simplest case. The position is then determined by means of these two capacitors. It is possible then to derive two directions from the capacitance values of the two capacitors, for example corresponding to left and right in a pointer device. It is also possible to use more capacitors locally or in the entire device so as to obtain a more accurate position reading. The capacitors need not be arranged symmetrically around the center of the space. If a possibility is sought of measuring certain locations of the body in the space with additional accuracy, this portion of the space may be fitted with additional capacitors. The size of the body may be chosen in dependence on the application. Thus the body may be smaller than the individual capacitors, so that the body may be present in its entirety between the electrode plates of one capacitor, but alternatively the body may be so large that it is always present between the electrode plates of a number of capacitors. The first electrode plate was common to several capacitors in the examples. This is not necessary the case. It is quite possible also to subdivide the first electrode plate so that, for example, each capacitor has its own first electrode plate. Intermediate solutions are also possible, for example two capacitors having a common first electrode plate. The electrode plates may very well be made from a material other than gold, for example from a metal such as aluminum, chromium, copper, tungsten, or from suicides or conductive monocrystalline, polycrystalline, or non-crystalline semiconductor materials such as silicon. Furthermore, the sacrificial layers may be manufactured from a material other than silicon oxide. It is essential for the material of the sacrificial layer to be capable of selective etching relative to the material of the electrode plates and the material of the dielectric body. Such combinations are known. It is also possible for the two electrode plates to be made from different materials. It is thus possible, for example that a conductive silicon substrate is used for the first electrode plate while upper, second electrode plates of metal are used. The device may be manufactured as a stand alone device. It is alternatively possible, however, for the device to be manufactured in the so-called back end of a semiconductor manufacturing process. The metal and dielectric layers available in that process are utilized in that case. The substrate used for the device then comprises, for example, semiconductor devices which serve for measuring the capacitance values of the capacitors Cl, C2, C3, C4 and for processing these values further.

Claims: CLAIMS: 1. A device for indicating a position, characterized in that the device is provided with capacitors which comprise fixed electrode plates between which a common space is present, a body of a dielectric material being arranged in said space and being capable of moving in said space such that the position can be derived from the location of the body in relation to electrode plates of different capacitors. 2. A device as claimed in Claim 1, characterized in that the capacitors comprise a common first electrode plate and individual second electrode plates which are arranged symmetrically around the center of the space. 3. A device as claimed in any one of the preceding Claims, characterized in that the space is filled with a liquid. 4. A device as claimed in any one of the preceding Claims, characterized in that the space has a rectangular box shape and the body has a cylindrical shape. 5. A device as claimed in any one of the preceding Claims, characterized in that the dielectric body comprises a material having a dielectric constant higher than 800. 6. A device as claimed in any one of the preceding Claims, characterized in that at least one of the electrode plates is provided with a depression which serves as a preferred location for the body. 7. A device as claimed in any one of the preceding Claims, characterized in that that the body is held in a preferred location by means of a spring. 8. A device as claimed in any one of the preceding Claims, characterized in that the device comprises a mechanism for applying a voltage to all electrode plates such that the dielectric body can be brought into a preferred location by electrostatic means. 9. A device as claimed in any one of the preceding Claims, characterized in that the device comprises a substrate on which both the capacitors and an electronic circuit for reading out or processing electrical signals obtained through the capacitors are provided. 10. A remote control device, characterized in that it is provided with a device as claimed in any one of the Claims 1 to 9.

Inventors: DE SAMBER MARK ANDRE, DE SAMBER, MARK, ANDRE
Applicants: PHILIPS ELECTRONICS NV, PHILIPS NORDEN AB, PHILIPS ELECTRONICS N.V.
Application year: 1997
Main classification: G01B7
IPC codes: G01B7, G01D5