ROTATIONALLY ACTUATED POSITION SENSOR

Abstract: A position sensor comprises two curved surfaces concentrically aligned to form a container which is filled with a viscous fluid and a bubble of a lighter-weight fluid and placed between a radiation source and a radiation detector. The bubble changes position within the container when the sensor is moved, transmitting a beam of radiation from the radiation source through the bubble to activate a section of the radiation detector while the remainder of the radiation is blocked by the fluid. Position sensing circuitry translates a signal from the activated section of the radiation detector into position coordinates for point in space corresponding to the position of the bubble in the container. The position sensor is suitable for use in a digital controller that generates display attributes to define a locator symbol on an output device. The digital controller can include an optional button to permit a user to change the size of the locator symbol, making it appear to approach or recede, to provide a simulated three-dimensional display.

Description: ROTATIONALLY ACTUATED POSITION SENSOR Field of the Invention The present invention is related to position sensors and in particular to a sensor that uses a bubble suspended in a fluid medium to determine positions in a two-dimensional reference system. Background of the Invention A carpenter's level using a vial containing a fluid and a suspended bubble that is centered in the vial when the instrument is placed on a level surface is well-known. However, the basic carpenter's level is only useful for determining whether the surface is level and not at what angle the surface may be inclined. In recent years, the carpenter's level has been enhanced by incorporating electronic level sensing devices in place of, or in addition to, the vial, fluid, and bubble. One purpose of the improved carpenter's levels is to determine the inclination angle of the surface. However, an inclination angle cannot be used to specify a point in space, as the angle is expressed in terms of a single degree of freedom- its rotation about one axis—while a point in space must be defined in terms of at least two degrees of freedom. Other devices designated as orientation sensors work on the same principal as the carpenter's level but employ different shaped containers for the fluid and the bubble. These devices suffer from the same limitations of the carpenter's level in that they only detect changes in a single degree of freedom. In addition, these device reflect light off the bubble to determine the orientation of the device so the light must transit the fluid twice, once to bounce off the bubble, and again when reflected to a detector. Diffraction and refraction problems introduced by the light's path and also by its reflection off the bubble lead to inaccuracies in measurement unless the device is carefully manufactured and calibrated, making the production of such a device a complex and costly process. There is a need for a device that combines the ability to define positions in space in a two-dimensional coordinate system with simplicity of manufacturing and long-lived accuracy. Summary of the Invention Two curved surfaces are concentrically aligned to form a container which is filled with a viscous, radiation-absorbent fluid and a bubble of a lighter- weight, radiation-transmissive fluid that changes position within the container in response to rotational movement of the container about two axis. The container is placed between a radiation source and a radiation detector to form a position sensor. A portion of electro-magnetic radiation from the radiation source is transmitted through the bubble and activates a section of the radiation detector while the remainder of the radiation is blocked by the fluid. Points in a two- dimensional plane are equated to positions of the bubble within the container so that the section of the radiation detector that is activated by the radiation transmitted through the bubble corresponds to a point in the plane. By assigning position coordinates to each section of the radiation detector, position sensing circuitry is able to translate a signal from the activated section of the radiation detector into position coordinates for the corresponding point. The rotationally actuated position sensor is suitable for use in any apparatus that relies on a two-dimensional coordinate system, such as geographical tracking systems, and surveying equipment. The position sensor is also applicable to computer-input devices that logically use a pair of coordinates to address a point on a computer screen, and replaces the ball currently used in input devices such as mice and trackballs so that the user is no longer constrained to using the device on a surface. The position sensor also does not become jammed as ball-controlled input devices currently do which causes great user frustration. A computer-input device or digital controller which uses the position sensor can optionally include a control button that acts as a standard mouse button or generates a third display attribute. The first and second display attributes generated by the position sensor combine with the third display attribute generated by the control button to define the locator symbol in three dimensions as it moves on the display. The third display attribute determines the size of the locator symbol so that the locator symbol appears to approach and recede on the display as the its size is changed, thus simulating the movement of a three-dimensional object on a standard two-dimensional display screen. The rotationally actuated position sensor addresses the limitations found in the prior art devices. The electronic components are long-lived, the radiation source is replaceable, and, when made of high-impact plastics, the sensor is virtually indestructible. Furthermore, the sensor is simple and inexpensive to manufacture as it incorporates common materials, off-the-shelf components, and it does not incur the diffraction and refraction problems inherent in the prior art. Finally, its degree of accuracy is high, will not degrade over time, and can be calibrated to the specific application in which the sensor is employed. Brief Description of the Drawings Figure la is a perspective view of an embodiment of a position sensor. Figure lb is a cross-section view of the position sensor shown in Figure la taken along line 1-1. Figure 2 is a functional diagram of the position sensor. Figure 3a is a cross-section view of a hemispherical-shaped container in the position sensor. Figure 3b is a cross-section view of a dome-shaped embodiment of the container. Figure 4 is the cross-section view of Figure 3b with the addition of a radiation detector. Figure 5 is the cross-section view of Figure 3a showing a plurality of dimples. Figure 6a is an alternate embodiment of position sensor shown in Figure 4. Figure 6b is another alternate embodiment of position sensor shown in Figure 4. Figure 7 is a perspective view of an embodiment of a rotationally actuated three-dimensional digital controller incorporating the position sensor. Figure 8 is a block diagram of one embodiment of the digital controller. Description of the Embodiments In the following detailed description of the embodiments, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the scope of the present inventions. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present inventions is defined only by the appended claims. Numbering in the Figures is usually done with the hundreds digits corresponding to the figure number, with the exception that identical components which appear in multiple figures are identified by the same reference numbers. Figures 1 a and 1 b show two views of an embodiment of a rotationally actuated position sensor 100. Figure la is a perspective view and Figure lb is a cross-section view taken along line 1-1 of Figure la. The position sensor comprises a curved container 102 filled with a viscous fluid 104 and a lighter- weight fluid forming a bubble 106. As the sensor 100 is rotated around either a first axis 120 or second axis 122, the lighter bubble 106 moves within the viscous fluid 104 in reaction to gravity acting on the viscous fluid 104 and in accordance with the principals of fluid dynamics. The rotation of the sensor 100 around a third axis 124 does not cause the bubble to move within the container 102. The viscosity of the viscous fluid 104 is sufficient to prevent the bubble 106 from disintegrating while allowing it freedom to move within the viscous fluid 104. In one embodiment, the viscous fluid 104 is a light-weight oil and the bubble 106 contains nitrogen gas. The weight of the oil is dependent on the size of the container 102 and the desired velocity of the bubble 106. The substitution of other fluids and/or gases with these and other required qualities as discussed later will be apparent to those skilled in the art. The container 102 is positioned between a radiation source 108 and a radiation detector 110. Position sensing circuitry 1 12 is coupled to the radiation detector 1 10 to translate signals generated by the radiation detector 1 10 into position coordinates. The position sensing circuitry 1 12 is further coupled to a read-out device (not shown), such as a digital numeric display or a computer, that presents the position coordinates to a user in a desired format. The radiation source 108, the radiation detector 1 10 and the position sensing circuitry 1 12 are further electrically coupled to a power supply such as a battery or an AC source which is not shown. As shown in Figure 2, the viscous fluid 104 is substantially opaque to the wavelength of radiation emitted by the radiation source 108 but the lighter- weight fluid forming the bubble 106 is substantially transparent to the same wavelength so that a portion, or beam, 202 of the radiation passes through the bubble 106 and activates a section of the radiation detector 1 10 while the remainder of the radiation 204 is substantially blocked by the viscous fluid 104. Each section of the radiation detector 110 is assigned a pair of position coordinate values that define a point on a flat plane in a cartesian reference system. In an alternate embodiment, each pair of coordinate values defines a point in terms of spherical coordinates, such as altitude and azimuth, so that the sensor 100 can be used to determine positions on a curved plane. The position of the bubble 106 in the container 102 determines which section of the radiation detector 110 is activated by the beam 202 and thus what coordinate values are transmitted by the position sensing circuitry 112 to the read-out device. The position coordinates are relative to an origin point within the container 102. In one embodiment, the origin point is fixed within the container 102; in an alternate embodiment, the location of the origin point in the container 102 is defined by the position sensing circuitry 1 12. In a further alternate embodiment, the origin point is a previous position of the bubble 106 and the position sensing circuitry 1 12 transmits the difference in position coordinates between the base position and a new position of the bubble 106 as it moves within the container 102. The sensitivity of the radiation detector 1 10 to the wavelength of the light emitted by the radiation source 108 determines the percentage of the radiation that the viscous fluid 104 must absorb (the "opaqueness" of the fluid). The required opaqueness can be an inherent property of the fluid chosen, or the viscous fluid 104 can be "dyed" to absorb the emitted wavelength. In one embodiment, the radiation emitted from the radiation source 108 is visible light and the viscous fluid 104 is a light-weight oil infused with a substance such as graphite that absorbs visible light. The use of alternate pigments to dye the viscous fluid 104 to the required opaqueness will be apparent to those skilled in the art. Figures 3a and 3b show cross sectional views of two embodiments of the container 102 of the position sensor. In both figures, the container 102 is formed from two curved surfaces 320 and 330, and the bubble 106 touches both surfaces 320 and 330. Each surface 320 and 330 is formed of continuous, smooth arcs so each surface has a single convex side 322 and 332 and a single concave side 324 and 334. The surfaces have similar curvatures and are substantially concentrically aligned so that the concave side 324 of one surface, referred to as the outer surface 320, is substantially equidistant from the convex side 332 of the other surface, referred to as the inner surface 330. The curvatures of the surfaces 320 and 330 determines the shape of the container 102 so that if the degrees of curvature are substantially 180°, a hemispherical container is formed as shown in Figure 3a, and if less than 180°, a dome-shaped container is formed as shown in Figure 3b. The use of surfaces with other degrees of curvature, including 360° to form a container in the shape of a complete sphere, will be apparent to those skilled in the art. Furthermore, the use of curved segments from surfaces of three-dimensional objects other than regular spheres, such as oblate spheroids or elliptic paraboloids, will also be apparent to those skilled in the art. The choice of surface curvature determines whether the velocity of the bubble 106 is constant throughout the container 102 and also determines the range of bubble movement when the container 102 is rotated. The surfaces 320 and 330 are formed of a thin material that is substantially transparent to the wavelength emitted by the radiation source 108. In one embodiment, a sheet of acrylic is heat-pressed to the desired curvature to form at least one of the surfaces; in another embodiment, liquid urethane plastic is poured into a mold with the desired curvature. Both these alternate embodiments provide surfaces substantially transparent to visible light. The use of alternate materials and manufacturing methods for making the container 102 will be apparent to those skilled in the art. The transmission of position coordinates caused by slight, accidental movements of the bubble 106 within the container 102 reduce the accuracy of the sensor 100. In one further alternate embodiment the viscosity of the viscous fluid 104 provides a damping effect so that minor vibrations do not cause the bubble 106 to move. In still another alternate embodiment, the construction of the container 102 combines with the position sensing circuitry 1 12 to filter out unintentional movements. The curvature of the container 102 causes the bubble 106 to return to a neutral location within the container when the sensor 100 is at rest. A dimple 310 is formed in the concave side 324 of the outer surface 320 at the neutral location. During manipulation of the sensor 100 by a user, the bubble 106 moves away from the dimple 310. If the user continues to move the sensor 100 so that the bubble 106 moves back toward the dimple 310, the bubble 106 transits the dimple 310 without stopping because of the inertia imparted by the user. However, if the bubble 106 moves toward the dimple 310 because the user is no longer moving the sensor 100 or because of minor vibrations, the bubble 106 lodges in the dimple 310 and the position sensing circuitry 1 12 registers the position change as only "noise." The sensor 100 can have more than one neutral position depending on its shape and application, and thus have more than one dimple 310 as shown in Figure 5. The dimples 310 are small enough in size so as to not significantly interfere with the radiation transmission through the bubble 106. The bubble 106 exists due to the property of fluids to form a curved surface, or a "meniscus," where the fluid comes in contact with a container. In a further alternate embodiment, the viscous fluid 104 chosen has a meniscus that is highly reflective to the wavelength of the radiation from the radiation source 108. The reflective quality of the meniscus reduces diffusion of radiation through the viscous fluid 104 in the areas where the viscous fluid 104 is thinnest and is less opaque to the radiation. The size of the areas where the bubble 106 is in contact with the surfaces 320 and 330 determines the diameter of the beam 202 of radiation transmitted through the bubble 106. The size of these areas is determined by the size of the bubble 106 and the distance between the inner and outer surfaces 330 and 320. The size of the bubble 106 is determined by the type and amount of the lighter- weight fluid introduced into the container 102 and the viscosity of the viscous fluid 104. In the radiation detector 1 10 as shown in Figure 4, each section of the radiation detector 1 10 is a radiation responsive grid element 402 sensitive to the wavelengths of radiation emitted by the radiation source 108. For visible light, each grid element 402 can be a sensor such as a silicon pin photodiode, part number BPV23NFL, from Telefunken of Germany. Many other photodiodes or other types of sensors from various manufacturers are also suitable. The minimum size of the grid elements 402 is determined by the diameter of the beam 202 transmitted through the bubble 106. The number of grid elements 402 and the shape of the radiation detector 110 depend upon the specific application using the sensor 100. Figure 4 also shows a portion of the radiation detector 1 10 and illustrates a grid configuration where the grid elements 402 are abutted edge to edge to form a sensor array. Such a sensor array is manufactured by affixing the grid elements 402 to a silicon base or onto a flexible sheet made of a material such as Mylar ® which can be stretched to fit over the container 102. Alternate manufacturing methods and materials suitable to construct a radiation detector of an appropriate size and shape will be apparent to those skilled in the art. In an alternate embodiment, more than one sensor is activated by the beam 202 of radiation transmitted through the bubble 106. The position sensing circuitry 112 interpolates the signals from all the activated sensors to a single coordinate pair using well-known algorithms similar to those currently in use in touch pad input devices such as the Glide Point from Cirque. In a further embodiment in which the position sensor 100 has a plurality of dimples 310 as shown in Figure 5, the radiation detector 110 has a corresponding plurality of radiation responsive grid elements 402. Figure 4 further illustrates the radiation detector 1 10 as having a curvature substantially similar to that of the outer surface 320 and affixed to the convex side 322 of the outer surface 320 of the container 102. In an alternate embodiment shown in Figure 6a, the curvature of the radiation detector 1 10 is also substantially similar to that of the outer surface 320 but is spaced apart from the outer surface 320. In still another embodiment shown in Figure 6b, the radiation detector 110 is a flat plane positioned adjacent to the outer surface 320. Other locations for the radiation detector 1 10 will be apparent to those skilled in the art. In such cases, the individual grid elements 402 are mapped to desired coordinate pairs based on their position relative to the bubble 106 and the radiation source 108. The radiation source 108 is positioned to substantially evenly illuminate the radiation detector 1 10. In one embodiment, the radiation source 108 is positioned below the concave side 334 of the inner surface 330 of the container 102 as shown in Figures la and lb. In an alternate embodiment shown in Figure 4, the radiation source 108 is positioned within a cavity bounded by the concave side 334 of the inner surface 330. The radiation can directly illuminate the container 102 or be routed through a diffuser designed to more evenly distribute the radiation. In still another embodiment, the radiation source 1 8 comprises a plurality of light pipes, one for each radiation responsive grid element 402. A particular use for the position sensor of the present invention in a digital controller for a computer system is described with reference to Figures 7 and 8. In particular, Figure 7 is a perspective view of a rotationally actuated three-dimensional digital controller 700. The embodiment of the digital controller 700 shown in Figure 7 comprises a housing 702, a rotationally actuated position sensor 704, and three control buttons 706, 708 and 770. The position sensor 704 is of the type disclosed above. In one embodiment, the housing 702 comprises elongated octagonal-shaped top and bottom surfaces and eight rectangular sides. In a further embodiment, the housing 702 is cgonomically shaped to be comfortable in different-sized hands. The top and bottom surfaces are spaced apart so that a cavity is formed in between them that is bounded by the sides. First and second control buttons 706 and 708 are disposed directly opposite one another on two of the sides. A third control button 710 is mounted on a side mutually perpendicular to the sides having the first and second control buttons 706 and 708. The position sensor 704 is disposed on the top surface of the digital controller 700. In an alternate embodiment, the position sensor 704 is disposed on the bottom surface, and in yet another alternate embodiment, the position sensor 704 is sized to fit wholly within the cavity of the digital controller 700. The position sensor 704 generates first and second display attributes in response to a user rotating the digital controller 700 about an axis 712 (shown by arc 714) and/or an axis 716 (shown by arc 718). The first, second and third control buttons 706, 708 and 710 generate signals when pressed by a user. The first and second control buttons 706 and 708 each separately generate a third display attribute while the third control button 710 generates a command, such as "execute program", to the output device 720. In a further alternate embodiment, the digital controller 700 has a single button with functions corresponding to control button 710. In still another alternate embodiment, the digital controller 700 has no buttons and is used only to generate the first and second display attributes while commands are generated through a standard keyboard or similar input device. Use of more or fewer buttons with the same or different functions, and different locations for the buttons, as well as the inclusion of triggers, keys, or other user-operated functions will be apparent to those skilled in the art. The digital controller 700 is communicatively coupled to a read-out or output device 720 having a display screen 722. The first and second display attributes generated by the digital controller 700 defines a position for a locator symbol 724 on the display screen 722 while the third display attribute determines a size for the locator symbol 724. In one embodiment, a first transceiver (806 in Figure 8) coupled to the digital controller 700 broadcasts electro-magnetic signals representing the display attributes to a second, corresponding transceiver 726 coupled to the output device 720. Such transceivers are common, industry-standard components used in wireless computer input devices. That the electro-magnetic signals can be frequency modulated pulses, or infrared light, or other portions of the electro-magnetic spectrum will be apparent to those skilled in the art, as will alternatively coupling the digital controller 700 to the output device 720 through copper wire, fiber optic cabling, or similar hard-wired connections. In one embodiment, the output device 720 is a computer having a central processing unit (CPU) coupled to a computer monitor or screen equivalent to display screen 722. The CPU executes application software that supports a simulated three-dimensional display using the locator symbol 724, which may be a cursor, a graphics tool, a game character, or the like. Standard pointing device driver software supplies the first and second display attributes to the application software along with information on the state of the control buttons 706 and 708. The application software translates the state of the control button 706 and 708 into the third display attribute to create the appropriate sized locator symbol 724 and to position it on the display screen 722 in the location specified by the first and second display attributes. Any currently available driver software that supports the second and/or third buttons on a standard mouse pointing device can be used in conjunction with the three-dimensional digital controller 700 without modification. The same driver software can be used with the alternate embodiment of the digital controller 700 which have only control button 710 or no control buttons, or alternate driver software that supports only a single button mouse can be substituted. As described above, the size of the radiation detector (1 10 of Figure lb) within the position sensor 704 is dependent on the number of sensors it contains as well as the desired range of motion. In one embodiment, rotation of the digital controller 700 in an arc of 90° around axis 716 moves the locator symbol 724 from one side of the display screen 722 to the other side. Similarly, rotation of the digital controller 700 in an arc of 90° around axis 712 moves the locator symbol 724 from the top of the display screen 722 to the bottom. Thus, the size of radiation detector in this embodiment is no larger than necessary to track the bubble as it moves along these two arcs. The device driver software is also used to modify the relationship between the movement of the symbol and the movement of the bubble in a manner similar to that used by standard mouse driver software to determine how far the mouse must move in order to move a cursor a fixed distance on the screen. In order to increase the speed of symbol movement, the device driver maps an arc of much less than 90° to the movement of the symbol 724 from top to bottom and/or from side to side of the display screen 722. Other determining factors for the size and shape of the radiation detector include: the size and shape of the container (102 of Figure la) and the size and shape of the digital controller 700. As described above, the radiation detector may be affixed to and have a substantially similar curvature as that of the container, or may be separate from the container and be curved or flat. The amount of the container covered by the radiation detector depends on the how the device driver maps the arcs of rotation of the digital controller 700 to the movement of the locator symbol 724. Additional sizes and shapes for the radiation detector other than those described above will be apparent to those skilled in the art. The position sensor 704 of the digital controller 700 operates as described above, wherein the movement of the bubble in the container controls the movement of the locator symbol 724. In one embodiment, the screen coordinates are relative to an origin point on the display screen 722 and a bubble position within the container is defined as a base position representing the origin point. The position coordinate values that are assigned to the sections of the radiation detector are relative to the base position and thus to the origin point on the screen. In one alternate embodiment, the base position is fixed; in another alternate embodiment, the location of the base position is defined by the position sensing circuitry of the position sensor 704. In a further alternate embodiment, the base position is a previous position of the bubble 206 and the first and second attributes are equated to the difference between the position coordinate values of the base position and those of a new position of the bubble as the bubble moves within the container. In addition to having a base position equated to the previous position of the bubble, another alternate embodiment also designates a neutral position within the container to which the bubble returns when the digital controller 700 is at rest. Movement of the bubble to the neutral position from the base position does not change the screen coordinates of the locator symbol 724. This feature is analogous to the "return to zero" found in most computer joysticks and permits the user to put down the digital controller 700 without changing the position of the locator symbol 724. Figure 8 is a block diagram of still another alternate embodiment of the digital controller 700. The position sensor 704 and the first control button 706 are electrically coupled to a switching circuitry 804 which is further coupled to a battery 802. The switching circuitry 704 controls distribution of power to the digital controller 700 in response to a user action. In one embodiment, the switching circuitry 804 comprises timer circuitry and the user action is moving or not moving the controller. Power is distributed to the controller when the controller is in use, and not distributed to the controller 700 when it is not in use and a time-out period has elapsed. The time-out period can be selectable by the user or pre-set by the manufacturer of the digital controller 700. In an alternate embodiment, the switching circuitry 804 comprises capacitive coupling manufactured as part of the housing 702 so that while a user is touching the housing (the user action), power is distributed to the controller 700. Figure 8 also shows the first transceiver 806 electrically coupled to the position sensor 704 and the first button 706 so that the first transceiver 806 broadcasts the display attributes to the second transceiver 726. It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims: WHAT IS CLAIMED IS: 1. A position sensor (100) characterized by: inner (330) and outer (320) curved surfaces substantially concentrically aligned to form a container (102) therebetween, wherein the container is substantially filled with two fluids of differing characteristics (104, 106) such that a bubble (106) is created that changes position within the container as the sensor is moved; a source of electro-magnetic radiation (108) positioned to illuminate the container (102) so that a portion of the radiation (202) is transmitted through the bubble; and a radiation detector (1 10) positioned opposite the radiation source (108) so that the portion of the radiation (202) transmitted through the bubble (106) activates a section of the detector (110) corresponding to the position of the bubble within the container. 2. The sensor of claim 1, further characterized in that one fluid is viscous (104) and the other fluid (106) is lighter in weight than the viscous fluid. 3. The sensor of claim 2, further characterized in that the lighter- weight fluid is nitrogen gas and the viscous fluid is a light-weight oil infused with graphite that substantially absorbs visible light emitted by the radiation source. 4. The sensor of claim 2, further characterized in that a meniscus formed by the viscous fluid is reflective to the radiation emitted by the radiation source (108). 5. The sensor of claim 1, further characterized in that the radiation source (108) comprises a plurality of light pipes. 6. The sensor of claim 1, further characterized in that the radiation detector (1 10) comprises a plurality of radiation responsive grid elements (402) that are activated by the radiation emitted by the radiation source (108). 7. The sensor of claim 1 , further characterized by: position sensing circuitry (1 12) that equates a point in a two-dimensional coordinate system to the position of the bubble (106) within the container (102) and translates a signal generated by the activated section of the detector (1 10) into position coordinates for the point. 8. The sensor of claim 7, further characterized in that the two-dimensional coordinate system is a cartesian coordinate system for referencing positions lying in a flat plane. 9. The sensor of claim 7, further characterized in that the two-dimensional coordinate system is a spherical coordinate system for referencing positions lying in a curved plane. 10. The sensor of claim 7, further characterized in that the position coordinates are relative to an origin point within the two-dimensional coordinate system. 1 1. The sensor of claim 7, further characterized in that the origin point is a fixed location within the container. 12. The sensor of claim 7, further characterized in that the location of the origin point within the container changes as the sensor is moved. 13. The sensor of claim 1, further characterized in that the inner (330) and outer (320) surfaces each has a curvature and each further comprises a convex side (332, 322) and a concave side (334, 324). 14. The sensor of claim 13, further characterized in that the curvatures of the inner (330) and outer (320) surfaces form a hemispherical container. 15. The sensor of claim 13, further characterized in that the curvature of the inner (330) and outer (320) surfaces form a container shaped substantially similar to one-half of an oblate spheroid. 16. The sensor of claim 13, further characterized in that the concave side (324) of the outer surface (320) is substantially equidistant from the convex side (332) of the inner surface (330) throughout the container (102) so that the bubble (106) does not substantially change as it moves within the container. 17. The sensor of claim 13, further characterized in that a dimple (310) is formed in the concave side (322) of the outer surface (320) to trap the bubble ( 106). 18. The sensor of claim 17, further characterized in that the dimple is one of a plurality of dimples, and the radiation detector (1 10) comprises a plurality of radiation responsive grid elements (402) corresponding to the plurality of dimples. 19. The sensor of claim 13, further characterized in that the radiation detector (1 10) has a substantially similar curvature as the outer surface (320) of the container (102). 20. The sensor of claim 19, further characterized in that the radiation detector (1 10) is spaced apart from the convex side (322) of the outer surface (320). 21. The sensor of claim 19, further characterized in that the radiation detector (1 10) is affixed to the convex side (322) of the outer surface (320). 22. The sensor of claim 13, further characterized in that the radiation source (108) is positioned within a cavity bounded by the concave side (334) of the inner surface (330). 23. The sensor of claim 13, further characterized in that the radiation source (108) is positioned adjacent to the concave side (334) of the inner surface (330). 24. Means for generating position coordinates for points in a two-dimensional coordinate system characterized by: means (104, 106) for creating a bubble (106) within a curved container (102); means (108) for irradiating the container (102) so that a portion of the radiation (202) is transmitted through the bubble (106); means (110) for detecting the radiation (202) transmitted through the bubble (106), the detection means (1 10) positioned opposite the irradiation means (108) so that the portion of the radiation (202) transmitted through the bubble activates a section of the detection means; and means (112) for translating a signal from the activated section of the detection means (1 10) into position coordinates in the two-dimensional coordinate system. 25. A method of generating position coordinates for points in a two-dimensional coordinate system in a curved container (102) substantially filled with two fluids ( 104, 106) of differing characteristics so that a bubble ( 106) is formed that changes position within the container in response to movements of the container, the method characterized by the steps of: rotating the container (102) in at least one direction corresponding to the curvature of the container; illuminating the container with radiation from a radiation source (108) so that a portion of the radiation (202) is transmitted through the bubble and remaining portions of the radiation (204) is blocked by the fluid (104); activating a section of a radiation detector (1 10) with the radiation transmitted through the bubble (106); and translating a signal from the activated section of the radiation detector (110) into position coordinates for the point corresponding to the position of the bubble (106) in the container (102). 26. A rotationally actuated digital controller (700) interfaced to an output device (720) that moves a locator symbol (724) defined by first and second display attributes on the output device, the digital controller characterized by: a housing (702); and a position sensor (704) coupled to the housing that generates the first and second display attributes for the locator symbol, wherein the position sensor comprises: inner (330) and outer (320) curved surfaces substantially concentrically aligned to form a container (102) therebetween, wherein the container is substantially filled with two fluids of differing characteristics (104, 106) such that a bubble (106) is created that changes position within the container as the sensor is moved; a source of electro-magnetic radiation (108) positioned to illuminate the container (102) so that a portion of the radiation (202) is transmitted through the bubble; a radiation detector (110) positioned opposite the radiation source (108) so that the portion of the radiation (202) transmitted through the bubble (106) activates a section of the detector (110) corresponding to the position of the bubble within the container; and position sensing circuitry (1 12) to translate a signal generated by the activated section of the detector into the first and second display attributes that are sent to the output device. 27. The digital controller of claim 26, further characterized by: at least one control button (706, 708, 710) coupled to the housing that generates a command which is sent to the output device. 28. The digital controller of claim 26, further characterized by: a first transceiver (804) electrically coupled to the position sensor, wherein the first transceiver broadcasts electro-magnetic signals representing the first and second display attributes; and a second transceiver (726) electrically coupled to the output device to receive the electro-magnetic signals representing the first and second display attributes. 29. A rotationally actuated three-dimensional digital controller (700) interfaced to an output device (720) that moves a locator symbol (724) defined by three display attributes on the output device, the digital controller characterized by: a housing (702); a position sensor (704) coupled to the housing that generates first and second display attributes for the locator symbol, wherein the position sensor characterized by : inner (330) and outer (320) curved surfaces substantially concentrically aligned to form a container (102) therebetween, wherein the container is substantially filled with two fluids of differing characteristics (104, 106) such that a bubble (106) is created that changes position within the container as the sensor is moved; a source of electro-magnetic radiation (108) positioned to illuminate the container (102) so that a portion of the radiation (202) is transmitted through the bubble; a radiation detector (1 10) positioned opposite the radiation source (1 8) so that the portion of the radiation (202) transmitted through the bubble (106) activates a section of the detector (1 10) corresponding to the position of the bubble within the container; and position sensing circuitry (1 12) to translate a signal generated by the activated section of the detector into the first and second display attributes that are sent to the output device; and a first control button coupled to the housing that generates a third display attribute for the locator symbol that is sent to the output device. 30. The digital controller of claim 29, wherein: the output device is characterized by a display screen (722); the first and second display attributes are characterized by a pair of position coordinate values that define a point on the display screen where the locator symbol is displayed. 31. The digital controller of claim 30, wherein the position coordinates values are relative to an origin point on the display screen. 32. The digital controller of claim 31, wherein a bubble position within the container of the position sensor is defined as a base position representing the origin point. 33. The digital controller of claim 32, wherein the base position is fixed. 34. The digital controller of claim 32, wherein the base position changes as the digital controller is moved. 35. The digital controller of claim 29, wherein the third display attribute determines the size of the symbol. 36. The digital controller of claim 35, further characterized by a second control button, wherein the first control button increases the size of the symbol and the second control button decreases the size of the symbol. 37. The digital controller of claim 29, further characterized by: a first transceiver (806) electrically coupled to the position sensor and the first control button, wherein the first transceiver broadcasts electro¬ magnetic signals representing the display attributes; and a second transceiver (726) electrically coupled to the output device to ! receive the electro-magnetic signals representing the display attributes. 38. The digital controller of claim 29, further characterized by: switching circuitry (804) electrically coupled to a power supply (402) and further coupled to the position sensor and the first control button, wherein the switching circuitry controls the distribution of power to the digital controller in response to a user action. 39. The digital controller of claim 38, wherein the power supply is characterized by a battery (402). 40. The digital controller of claim 38, wherein the switching circuitry is characterized by timer circuitry and the user action is not moving the controller so that power is not distributed after a time-out period has elapsed. 41. The digital controller of claim 38, wherein the switching circuitry is characterized by capacitive coupling located in the housing and the user action is touching the housing so that power is distributed to the controller while the user action continues. 42. A computer system characterized by: a central processing unit coupled to a memory and further coupled to a display screen, wherein the central processing unit generates a locator symbol on the display screen; and a rotationally actuated three-dimensional digital controller (700) communicatively coupled to the central processing unit, the digital controller characterized by: inner and outer curved surfaces substantially concentrically aligned to form a container therebetween, wherein the container is filled with a viscous fluid and a lighter-weight fluid such that a bubble is created that changes position within the container as the digital controller is moved; a source of electro-magnetic radiation positioned to illuminate the container so that a portion of the radiation is transmitted through the bubble; a radiation detector positioned opposite the radiation source so that the portion of the radiation transmitted through the bubble activates a section of the detector corresponding to the position of the bubble within the container; and position sensing circuitry to translate a signal generated by the activated section of the detector into first and second display attributes for the locator symbol. 43. The computer system of claim 42 and further characterized by a first control button that generates a third display attribute for the locator symbol. 44. A position sensor (100) characterized by: inner (330) and outer (320) curved surfaces substantially concentrically aligned to form a container (102) therebetween, wherein the container is substantially filled with two fluids of differing characteristics (104, 106); a source of electro-magnetic radiation (108) positioned so that a portion of the radiation (202) is transmitted through at least one of the fluids; and a radiation detector (1 10) positioned to receive such transmitted radiation.

Inventors: NICKUM LARRY A, NICKUM, LARRY, A.
Applicants: GATEWAY 2000 INC, GATEWAY 2000, INC.
Application year: 1997
Main classification: G06F3
IPC codes: G01C9, G06F3