Pointing device with differential optomechanical sensing

Abstract

A pointing device including a ball engaging one or more shaft encoders, each shaft encoder having an encoding wheel, including a monolithic photosensitive array for detecting light pulses representative of rotary movement of the ball. The photosensitive array provides a plurality of resolutions and permits accurate tracking of rotary movement of the ball without need for a mask. Comparator and latch means operate on the output of the array and provides digital hysteresis.

What is claimed is:  
     
       1. A cursor control device for control the position of a cursor on a video display screen wherein the cursor control device uses a rotatable ball in engagement with at least two shaft encoders to convert rotational movement of the ball into digital signals representing movement of the cursor comprising 
       a housing,  
       means for supporting the ball in engagement with the at least two shaft encoders, each of said shaft encoders having thereon an encoder wheel having slots therein, and the at least two shaft encoders arranged orthogonally to permit one shaft encoder to detect movement in an X direction and another to detect movement in the Y direction,  
       light emitting means on one side of each encoding wheel for emitting light in the direction of said encoding wheel,  
       a plurality of light sensitive means on the other side of each encoding wheel for detecting when the slots in the encoding wheel permit light from the light emitting means to impinge upon at least one of the light sensitive means and for generating at least one sensor output signal having a magnitude in response thereto, with no mask interposed between the light emitting means and the light sensitive means, and  
       a plurality of comparator means responsive to a plurality of said at least one sensor output signals for comparing at least first and second of said sensor output signals and generating at least one comparator output signal representative of the relative magnitudes of said sensor output signals, each comparator means providing a comparator output signal on a first output port if the first sensor output signal is greater than the second sensor output signal, and providing a signal on a second output port if the second sensor output signal is greater than the first sensor output signal,  
       processor means responsive to the comparator output signal for providing a cursor control output representative of the movement of the ball in one dimension for each of said shaft encoders.  
     
     
       2. The invention of  claim 1  wherein each of the plurality of comparator means and light sensitive means operatively associated with a shaft encoder are fabricated within a single integrated circuit. 
     
     
       3. A control device for controlling a position on a display screen wherein the control device uses an encoder wheel to convert rotational movement into digital signals representing movement of the position comprising: 
       
         a light emitter for emitting light in the direction of said encoding wheel;  
       
       
         a plurality of light sensors for detecting when the encoding wheel permits light from the light emitter to impinge upon at least one of the light sensors and for generating at least one sensor output signal having a magnitude in response thereto, with no mask interposed between the light emitter and the light sensors; and  
       
       
         a plurality of comparators, each responsive to sensor output signals from two of said sensors for comparing at least first and second of said sensor output signals and generating at least one comparator output signal representative of the relative magnitudes of said sensor output signals, each comparator providing a first comparator output signal if the first sensor output signal is greater than the second sensor output signal, and providing a second comparator output signal if the second sensor output signal is greater than the first sensor output signal. 
       
     
     
       4. The device of  claim 3  further comprising: 
       
         a processor responsive to the comparator output signals for providing a position control output representative of the movement of said encoder wheel. 
       
     
     
       5. The device of  claim 3  further comprising: 
       
         at least one line driver for transmitting said comparator output signals to a computer. 
       
     
     
       6. The device of  claim 3  further comprising: 
       
         a processor responsive to the comparator output signals for providing a position control output representative of the movement of said encoder wheel. 
       
     
     
       7. The device of  claim 3  wherein said encoding wheel includes a plurality of slits, and said light emitter is mounted on a first side of said encoding wheel and said light sensors are mounted on a second side of said encoding wheel. 
     
     
       8. A pointing device comprising: 
       
         an encoder rotatable in response to a user movement;  
       
       
         a light emitter for emitting light in the direction of the encoder;  
       
       
         a plurality of light sensors for detecting when the encoder permits light from the light emitter to impinge upon at least one of the light sensors, each of the light sensors generating a sensor output signal; and  
       
       
         a differential sampling circuit coupled to said plurality of sensors for generating digital signals corresponding to a difference between two of said sensor output signals, said digital signals having first and second digital values, and being said first digital value when a first of said two of said sensor outputs is greater than a second of said sensor outputs, and being said second digital value when said second of said sensor outputs is greater than said first of said sensor outputs. 
       
     
     
       9. The pointing device of  claim 8  wherein said differential sampling circuit includes at least one comparator. 
     
     
       10. The pointing device of  claim 8  wherein said plurality of light sensors and said differential sampling circuit are fabricated within a single integrated circuit. 
     
     
       11. The pointing device of  claim 8  further comprising: 
       
         a processor coupled to said differential sampling circuit for providing a position control output representative of the movement of said encoder.