Technical Field

The present invention relates to an apparatus for controlling a movable reference point on a display. The invention relates more particularly, but not exclusively, to an apparatus having mechanical means for actuation by an operator to provide a force, and conversion means for converting the force into electrical signals which are used for controlling the translational movements of a cursor on a video display.

Background Art

For purposes of the ensuing discussion, the terms reference point and cursor shall be used interchangeably, notwithstanding the recognition that a typical cursor pattern encompasses more than a single pixel position on a video display.

A variety of cursor controls exist in the prior art. In the context of personal computer systems, keyboard keys routinely control cursor translations and locations. Even with combinations of keys, the direct control of cursor movements are still commonly limited to translations incremented at 45° angles and at relatively fixed rates.

The angular limitations of keyboard key based controls have been overcome by the joy stick, the track ball, and more recently, the mouse forms of cursor controls. Joy sticks are on-off controls which both enable cursor movements and specify the directions of such movements. Joy stick type controls specify cursor movements at 90° intervals, and occasionally at 45° angular intervals. The track ball, a form of inverted mouse, as well as the mouse itself, are not restricted to large increments cf

angular direction nor rates of movement, but do inherently require significant translational actions by the operator. In the case of a track ball, manual rotation of the ball in the perceived direction and at the desired rate produces corresponding cursor effects. The mouse on the other hand, requires manual translation of the mouse structure over a miniaturized area analogous to the video display in order to produce corresponding translations of the cursor.

A variation of the such prior art arrangements is embodied in an apparatus described in the IBM Technical Disclosure Bulletin, Vol. 26, No. 7B, pages 3746 and 3747, December of 1983, wherein a keyboard cursor control is responsive to a logic combination of four individual keys so as to identify cursor translation demands at 45° angular orientations. Again, the angles of permissible translation are limited to 45° increments. A somewhat more refined cursor control is disclosed in U.S. Patent No. 4,246,452 in which the angular increments are reduced.

Disclosure of the Invention

It is an object of the present invention to provide an apparatus for improving operator control of the translational movement of a reference point on a display.

According to the present invention there is provided an apparatus for controlling a movable reference point on a display, the apparatus including mechanical means for applying a force and conversion means for converting the force into electrical signals determining the direction in which said reference point is to be moved, characterized in that said conversion means comprises a plurality of force- sensitive transducers and further characterized by means for processing the electrical signals produced

by said transducers so as to produce an output which controls the movement of said reference point at a rate dependent on the magnitude of the force.

In a preferred embodiment the mechanical means includes a planar structure mounted for rocking movement about a point, serving as a polar centroid, and the mechanical means is mechanically coupled to a resilient member for providing a resilient recentering force on the planar structure. In one embodiment the planar structure is disk-like and mounted on a keyboard for a computer.

Brief Description of the Drawings

Embodiments of the present invention will now be described by way of examples, with reference to the accompanying drawings in which:

Fig. 1 is a perspective view of the keyboard with an integrated cursor control disk.

Fig. 2 is a cross-section schematically illustrating one embodiment of the disk and force sensing structure.

Fig. 3 is a cross-section of an alternate embodiment for the surface plane of the keyboard.

Fig. 4 is a cross-section of an arrangement in which the disk-like structure is mounted external to the planar surface of the keyboard.

Fig. 5 is a schematic of the embodiment first depicted in Fig. 4 along a different section line, to illustrate representative arrangements of the strain sensors.

Fig. 6 is a schematic cross-section in which forces are detected by compressor sensors.

Fig. 7 is a schematic block diagram illustrating a representative arrangement for detecting the forces on the disk and resolving the forces into orthogonal and vector values.

Best Mode for Carrying Out the Invention

Referring to Fig. 1- there :is illustrated an apparatus comprising a keybσard 1, including various alphanumeric and functional keys 2, in a form commonly known and used. The difference resides in the presence of a disk-like cursor control structure 3, which is attached as an integral part of the keyboard 1, yet movable with respect to the plane defined by exterior surface 4. Movement the disk-like cursor control 3 is characterized by a rocking action, about a centrally disposed point 6 on the disk axis, in all 360° by the application of a force to such disk member 3. Preferably, the force applied by the operator is opposed by a resilient restoring force inherent in the structure of the cursor control apparatus. It should be readily apparent that the illustrated cursor control apparatus is fully capable of residing in an assembly independent of the keyboard 1.

Fig. 2 illustrates a representative arrangement for mounting disk 3 into keyboard 1 to provide features according to one embodiment of the present invention. Keyboard 1 includes an upper surface 4 and a bottom, surface 7. Shaft 11 of disk 3 projects through an opening 8 in upper surface 4 and is pivotally centered in such opening 8 by flexible 0- ring 9, or the like. Shaft 11 of disk 3 is sufficiently rigid to transfer lateral forces, such as rocking movement force 12 about an axial point 13 generally centered within opening 8. Force 12 creates linear and non-linear lateral translations at the base 14 of shaft 11. Base 14 of shaft 11 is itself attached to the center of a cross-shaped resilient member 16, which member is rigidly attached at four ends, e.g. two ends 17 and 18, to bottom surface 7 of keyboard 1. Each of the four arms of the cross-shape resilient member 16 includes, according to the preferred embodiment, a strain sensor to detect the

extension (strain gauge 19) and the compression (strain gauge 21) forces associated with the imposition of force 12 on disk 3. It should be apparent that irrespective of the location of force 12 on the surface of disk 3, the compression and extension strain measurements are resolved from polar to cartesian coordinate vectors by virtue of the orthogonal arrangement of the cross-shaped gauge pattern. Likewise, it should be evident that the composite magnitude of the force 12 is relatively measurable by the extension and compression forces sensed in the various strain gauges.

Movements of the video display cursor can be non-linearly related to the forces acting on disk 3. Consequently, the non-linear flexing of O-ring 9, resilient member 16, shaft 11 and disk 3, do not materially detract from the functionality of the apparatus.

The orthogonal arrangement of the strain gauges by pairs in a crossing pattern (generally in Fig. 5), wherein gauges 19 and 21 are operable as complements along one axis, is a preferred arrangement for sensing strain, in that such arrangement lends itself to classic bridge circuit detection responsive to differential strain.

The relevance of such a differential arrangement maybe more fully appreciated by considering the abnormal situation in which the force is directed vertically downward along shaft 11. Although a downward displacement of resilient member 16 center region near 14 will result, both strain gauges 19 and 21 will detect extension forces. With a differential sensing circuit, the output signals nevertheless remain substantially zero in value. Likewise, the extension and compression forces illustrated in Fig. 2 for strain gauges 19 and 21 will result in some movement of the orthogonally oriented

crossing arms, and a detection of associated stains. Again, however, in the context of a conventional . bridge detection circuit arrangement both of such.' strain gauges will experience an extension force and a net zero bridge detector response. Though such principles are well known to designers of bridge configured strain gauge weighing systems, they are here uniquely implemented in the context of a cursor control apparatus to provide a low-cost structure capable of receiving cursor movement commands in analog polar coordinates and resolving such commands into cartesian coordinates with amplitudes related to the magnitude of the operator supplied control force.

Fig. 3 illustrates a slightly different arrangement for mounting disk 3 in the top surface 4 of the keyboard. For this arrangement the disk 3 projects materially above the plane defined by surface 4 of the keyboard, in contrast to being recessed into the plane of the keyboard. This embodiment reduces the likelihood that contaminates will be trapped in the keyboard recess and eventually enter through opening 8.

Fig. 4 illustrates a somewhat different arrangement which nevertheless relies upon the fundamental principles of the present invention. A cross-section at 5-5 of the structure depicted in Fig. 4 is shown in Fig. 5. In the arrangement of Fig. 4, the center point 23, about which disk-like structure 24 rocks in response to a force 12, is fixedly attached to keyboard surface 4 at center 26 of cross- shaped resilient member 27. The thick and rigid outer- perimeter of member 24 projects downward and connects to resilient member 27 through joints 28, 29, 31 and 32.

For the arrangement in Figs. 4 and 5, the presence of a force 12 at a point, for example 33, causes strain gauge 34 to undergo compression as

strain gauge 36 is subject to extension, which for the classic resistance strain gauge produces respective decreases and increases in the oh ic values of resistors R3 and R4. Note again that the force is applied in polar coordinates but resolved into analog vectors of cartesian coordinates.

Another disk configuration is schematically depicted in Fig. 6. Here four pressure responsive sensors 37, arranged in pairs along orthogonal axes, detect the force 12 and resolve the force into respective cartesian coordinate magnitudes. Again, the disk 3 effectively pivots about a general central point defined by the opening 8 in keyboard surface 4.

Fig. 7 schematically illustrates the electronic circuit functions associated with the generation of video display control signals to represent force 12 (Figs. 2 and 4). The respective pairs of extension and compression resistors R1/R2 and R3/R4 provide cartesian coordinate measures of the polar coordinate to define the force 12 as analog signals which are in relative proportion to the magnitude of the force. According to a preferred arrangement the vector magnitude of such x and y signals is also calculated, and thereafter used to define, for example, the relative velocity or acceleration characteristics of the cursor movement. It should also be apparent that the various measurements will most likely be digitized prior to being used to drive the video display. Furthermore, with a rapid advance of digital sensor technology and the pervasive preference for digital signal processing, it is fully contemplated that the analog strain and pressure sensors described herein will be replaced by functionally equivalent digital force sensing devices.