Apparatus and Method for Controlling a Cursor on a Computer Display

This invention relates to an apparatus and method of controlling the cursor of a computer display and in particular to a cursor control device and method which translate motion of the head into motion of the cursor.

In many computer systems currently in use, a cursor serves as a major component of the interface between the machine and the operator of the machine. In graphics, data and word processing applications, the cursor indicates the current position of the data or text which can be edited or into which new data or text can be inserted. For many computers, the cursor is controlled simply by a key or keys on the keyboard. To move the cursor, the key or keys are depressed either a number of times corresponding to the number of position changes over which the cursor is to be moved or continuously until the cursor arrives at its desired position.

Recently, other types of cursor control devices have been developed. One such device, which is referred to as a "mouse", is designed to lie on a table or other flat surface and be moved about by hand. As the operator moves the mouse in a given direction on the table, the cursor moves in a corresponding direction. U.S. Pat. Nos. 3,541,541; 3,835,464; 3,892,963; 3,987,685; 4,390,873 and 4,409,479 provide examples of various mice.

These cursor control devices or mice operate in a number of different fashions. The mouse taught by U.S. Pat. No. 3,892,963, issued to Hawley, translates a mechanical action of bearings or other types of roller devices into an electrical signal which signifies an amount of position change. Such mechanical devices have, however, proven to be rather inconvenient to use for a number of reasons. First, when the computer is placed on a rather small table there may not be a sufficient area over which to move the mechanical device so that the wheels or other position change-indicating devices can accurately provide the full range of movement of the cursor. Second, after a substantial period of use, the mechanical moving parts of the mouse, such as the balls or wheels, become dirty and cease to provide continuous rolling action.

The "optical mouse" taught by U.S. Pat. No. 4,409,479 provides the advantage that movable parts are eliminated. This optical mouse, however, requires a significant amount of flat surface area over which is placed a special planar grid pattern for charting movement of the mouse. Also, dirt and dust will tend to block the light source or grid pattern if all of the components of the apparatus are not kept clean.

Principal among the other drawbacks of the mouse technology is that manipulating the mouse is difficult, and it often takes several hours to fully master. Once mouse manipulation is mastered, there is then the problem that it is often clumsy to go back and forth between the mouse and the keyboard when a task requires the entering of text or data into the computer. For the most part, the constant shifting required between the mouse and the keyboard makes mice virtually useless for word processing and accounting spread sheets, two of the more popular uses for personal computers with which mice are normally associated.

There are a number of other cursor control devices which suffer from any of the same shortcomings which are inherent in mice. Among these other cursor control devices are light pens, tablet pens, joy sticks, track balls and thumb wheels. For the most part, each of these devices also requires several hours of use to fully master, and the constant shifting between the cursor control device and the keyboard which is inherent in the use of mice also creates problems when using these cursor control devices.

One attempt to eliminate the problems caused by the aforementioned cursor control devices is disclosed in U.S. Pat. No. 4,369,439 issued to Broos. Broos provides a movable data entry keyboard which is mounted on a carriage. Cursor position signals are generated directly from position transducers associated with the carriage. In operation, when the operator entering data or text desires to move the cursor, a switch is activated and the keyboard is moved along a flat surface thereby resulting in corresponding movement of the cursor on the computer display. Operation of such a cursor control device is much simpler and quicker than the above-described cursor control devices because the operator's hands never leave the keyboard. The keyboard is, however, larger than conventional mice, and as a result, an area even greater that that required for mice is required for moving the keyboard. In addition, this cursor control device will require some start up learning time, and there will be some inconvenience associated with its use resulting from the fact that it is customary to type from a stationary keyboard. Typing from a constantly moving keyboard will never be as fast and easy as typing on a standard stationary keyboard.

It is therefore a principal object of the present invention to provide a cursor control device which is easy to use and which does not require significant start-up time for its initial use.

It is a further object of the present invention to provide a cursor control device which allows for simultaneous use of the cursor control device and the keyboard.

Still another object of the present invention is to provide a cursor control device which is operated by a natural and ordinary human movement.

An apparatus and method for controlling the cursor on a computer display is provided which translates the motion of an operator's head into movement of the cursor. A headset including ultrasonic receivers is placed over the head of an operator. A transmitter which is placed in close proximity to the computer display transmits ultrasonic signals which are picked up by the receivers of the headset. The phases of these signals are continuously compared, and the phase difference information is provided to the computer which calculates and executes appropriate cursor movement.

The above and other features and objects of the present invention will become apparent to those skilled in the art from the following detailed description which should be read in light of the accompanying drawings.

FIG. 1 is a schematic view of a computer system which includes a presently preferred embodiment of the cursor control apparatus of the present invention.

FIG. 2 is a schematic view of the orientation of receivers attached to a headset worn by an operator.

FIG. 3 is a schematic diagram of the signal processing circuitry for the cursor control device of the present invention.

FIG. 4 is a circuit diagram of an amplifier schematically shown in FIG. 3.

FIG. 5 is a circuit diagram of a phase comparator schematically shown in FIG. 3.

Appendix 1, which follows the specification, contains a listing of computer instructions in 8086 Assembly Language and Applesoft.RTM. for controlling the cursor of a computer display according to the present invention.

In the embodiment of FIG. 1, there is shown the presently preferred configuration of the cursor control apparatus of the present invention. A computer display 10, in the form of a cathode ray tube (CRT) display, is positioned a distance away from an operator 12 with only air separating the computer display 10 from the operator 12. A transmitter 14 is placed in close proximity to the CRT 10 and is preferably centrally located with respect to the screen 11 of the CRT 10. In the embodiment of FIG. 1 the transmitter 14 is centered on top of the computer display 10. A headset 16, placed around the head of the operator 12, preferably includes three ultrasonic receivers 18, 20 and 22. These receivers are used for receiving signals sent by an ultrasonic transmitter 14, as will be described in detail below. In the embodiment of FIG. 1, the headset 16 is connected to a circuitry box 24 which in turn is connected to thhe ultrasonic transmitter 14. There is also a connection from the circuitry 24 to the computer port 28 which is reserved for cursor control information.

To control a cursor with the cursor control device and method of the present invention, an operator places the headset 16 containing the receivers 18, 20, 22 over his head. An actuating switch 30, which is preferably included on the keyboard 32, is depressed to activate cursor movement. The operator then moves his head in the direction in which he desires to move the cursor on the screen he is facing. Only rotational movements of the head either upward, downward or to a side will effect movement of the cursor. Movements toward or away from the screen will for the most part not cause movement of the cursor. Once the cursor has arrived at its desired location on the computer output device, the actuating switch 30 is deactivated so as to lock the cursor in that desired position, and further movement of the head will not cause corresponding movement of the cursor.

Referring now to FIG. 2, the headset 16 with three ultrasonic receivers 18, 20, 22 is shown around the head of the operator 12. The left and right receivers 18, 22 are arranged so that when the headset is placed on the operator's head, they both lie along a substantially horizontal line. The cursor control apparatus works especially well when receivers 18, 22 are placed along a true horizontal line. Preferably, the headset 16 is positioned on the operator's head in such a way that the left and right receivers 18, 22 are situated slightly above the level of the ears--the lower, the better. The top receiver 20 is located at a substantially central location between receivers 18, 22 and at a location a distance above the left and right receivers 18, 22. Other arrangements of the receivers may also be utilized provided that all of the receivers do not lie along the same line. The above-described arrangement is preferred because the horizontal dimension is pure and the vertical dimension is easily computed. Also, if the cursor is only to be moved over a one dimensional path, then only two receivers are needed.

In one embodiment of the cursor control apparatus of the present invention, the circuitry 24 includes an oscillator 40, which provides an oscillating signal for the ultrasonic transmitter 14. While transponders operating at various ultrasonic frequencies are suitable for use in the present apparatus, a 40 kHz transponder has been chosen for the preferred embodiment because it is readily available, it is well beyond the range of hearing, and it provides waves of a wavelength of about 1/3 of an inch. Waves of such lengths facilitate detection and control of the wavelength cycles. It is important that the transponder chosen be as wide beamed as possible so that if an operator is not directly facing the computer display, movement of the operator's head can still be detected.

In operation, the 40 kHz oscillator 40, shown in FIG. 3, sends signals of this chosen frequency to the transmitter 14. The transmitter 14 in turn sends an ultrasonic wave through the air which is picked up by the three receivers 18, 20 and 22. Each of the received signals are amplified by amplifiers 42 (which will be described in greater detail below) in order to facilitate signal processing. The amplified signal from the right receiver 22 and from left receiver 18 are compared by phase comparator 44 (which will also be described in greater detail below) to produce a signal proportional to the phase relationship of those two signals and which is fed to the computer via port 28 to be used to calculate the horizontal position component (i.e. along the X axis). The amplified signals from the left receiver 18 and from the top receiver 20 are also compared to provide the phase relationship of these signals for determining a vertical position component (i.e. along a Y axis) by necessary calculations.

Referring to FIG. 4, the amplifier 42 includes two stages of negative feedback amplification and a further amplifier for converting the amplified analog signal into a digital signal. In the first stage 50, resistor 52 is provided to stabilize the circuit by loading the input signal. Resistor 54 reduces the input signal, and resistor 56 provides negative feedback control for amplifier 58. The power for operating amplifier 42 is taken from the computer's 5 V supply voltage. A voltage divider 60 is used for dividing this 5 V power supply into the 1.5 V necessary for operating the amplifiers. The second amplifier stage 64 is capacitively coupled to the first stage 50 by capacitor 62. In the second stage 64, a resistor 66 provides DC bias, and resistor 68 provides gain control for this feedback amplifier circuit. A feedback capacitor 70 is also provided for reducing gain at high frequencies. The amplified signal from amplifier 72 is fed to amplifier 74 which provides a digital signal from the amplified analog signal supplied by the second amplifier stage 64.

Referring now to FIG. 5, there is shown the phase comparator 44 which compares the phase relationships between the signals transmitted to receivers 18, 20 and 22. The phase comparator 44 includes JK flip-flops 80, 82, 84. Suitable flip-flops are manufactured by Motorola and sold under the designation SN74LS112A. In operation, all the flip-flops are initially in an off state, i.e. all Q outputs are low. Once the computer signals it is ready, a transition signal from the computer causes the first JK flip-flop 80 to set, thereby causing Q to go low. As a result, JK flipflop 84 is reset. Then, when an amplified signal from one of the receivers is fed to flip-flop 82, flip-flop 82 becomes set, and the Q output of flip-flop 82 goes low resetting flip-flop 80. As a result, flip-flop 80 cannot be set until flip-flop 82 has finished processing the amplified signal received from the receiver. Also, at this point, flip-flop 84 is no longer being actively reset. In the preferred form, the signal (signal 1) received by flip-flop 82 is sent by the left receiver 18, and the signal (signal 2) received by flip-flop 84 is sent by either the top 20 or right receiver 22. The output from flip-flop 82 provides a width-modulated pulse to the computer which is used to determine the appropriate direction and amount of movement of the cursor. The width of the pulse is determined by the amount of time flip-flop 82 is set. Flip-flop 82 becomes reset once the signal from either the right 22 or top receiver 20 sets flip-flop 84 thereby causing Q to go low thereby resetting flip-flop 82. This rather complicated phase comparator is necessitated by the fact that, while a simple logic circuit (such as an AND gate) can perform phase comparisons, such simple logic circuits will not give a signed phase comparison. In the present invention, the phase comparator must provide a signed output so that the computer can determine in which direction the head moves.

In determining the correct position changes, the phase relationships are examined as frequently as is practical in order to keep track of the movement of the head. These calculations must take place at least once during each half wavelength of movement. In one embodiment, in order to obtain suitable performance, the wave is sampled at 1000 times per second thereby allowing the system to track movements of over 10 feet per second. This rate is more than adequate for head movements since the head will not practically move more than 10 feet per second. Since the 40 kHz ultrasonic wave has a length of about 1/3 of an inch, and a time base of 4 MHz is easily achievable, a phase measurement resolution of 100 counts per cycle is convenient. This translates to a resolution of 300 parts per inch, which will enable the apparatus to track rather fine movements.

Movement of the headset is translated into movement of the cursor through measurements of phase changes in the ultrasonic wave picked up by receivers 18, 20, 22. The computer 26 tracks and stores changes in phase counts from one measurement to the next. The phase count measurements are processed to provide position change information signals for moving the cursor on the computer display. When the control switch 30 is activated, the computer 26 accepts the position change information signals and moves the cursor accordingly.

By using the relationships between the waves picked up by the receivers, only upward, downward or sideward rotational movements are recognized. Since there is no change in the phase reltionships of signals received by two receivers when an operator moves his head in a straight path toward or away from the transmitter 14, there will be no change in the cursor position caused by such movement.

The software in Appendix 1, which controls the computer processes described above, may be modified so as to adjust a scale factor which determines the amount of cursor movement caused by a given amount of head movement. The software also includes a provision for a hysteresis dead zone which is necessitated by the fact that it is very difficult for an operator to keep his/her head perfectly still. This dead zone allows small head movements to be made without causing corresponding cursor movement. Preferably, the software includes the capability of allowing the scale factor to be adjustable by the operator. Also, the scale factor can be made dependent on the velocity of the head movement.

While the apparatus and method for providing cursor movement corresponding to movement of a user's head of the present invention has been described with reference to a preferred embodiment, various modifications and alterations will occur to those skilled in the art from the foregoing detailed description and the accompanying drawings. For example, the various connections from the head set to the circuitry to the computer and the computer display may be optical fibers or wireless connection using infrared, ultrasonic or radio signals. In addition, relative movement can be determined on the basis of a pulse time interval as opposed to phase comparison. Also, while the invention has been described with reference to a CRT, the device and method of the present invention are equally applicable to any other computer display which has a position indicating symbol. Finally, while the preferred embodiment includes a transmitter mounted on a CRT and three receivers on the operator's head, the invention could also be practiced with a transmitter on the operator's head and three receivers on the CRT. These and other modifications and variations are intended to fall within the scope of the appended claims. ##SPC1##