Coordinates input apparatus

Abstract

A system for detecting the types and statuses of position designating devices is incorporated in a coordinates input apparatus having a tablet constituting a coordinates input section, a plurality of position designating devices of different types, and a position detecting circuit for driving the tablet and detecting positions at which coordinates are input by the position designating devices. The system has an antenna coil disposed around a coordinates input range of the tablet, and a tuning circuit disposed in each of the position designating devices for transmitting radio waves in response to an external signal at an individual frequency determined in accordance with the type of the corresponding position designating device. An AC signal of predetermined frequencies is applied to the antenna coil so that it transmits radio waves. The types and statuses of the position designating devices are detected by judging the condition of the position designating circuits from signals within the antenna coil while the transmission of the radio waves is suspended. With this system, the types and statuses of a plurality of position designating devices can be detected without having to connect the devices to other circuits via cords or provide them with complicated signal generating circuits and power sources such as batteries.

We claim: 
     
       1. In a coordinates input apparatus having a tablet constituting a coordinates input section, a plurality of different types of position designating devices, and a position detecting circuit adapted to drive said tablet and detect positions at which coordinates are input by said position designating devices, a system for detecting the statuses of said position designating devices comprising: at least one antenna coil positioned relative to a coordinates input range of said tablet;   wherein each of said position designating devices has a tuning circuit disposed therein, each of said tuning circuits including a coil and capacitors working cooperatively to transmit radio waves in response to an external signal at a frequency predetermined in accordance with a corresponding type of position designating device;   wherein an AC signal having a plurality of frequencies each being identical to an individual frequency of one of said tuning circuits is intermittently and sequentially applied to said antenna coil so that radio waves are transmitted by said antenna coil, and, when the transmission of said radio waves is suspended, signals generated by said tuning circuits in response to said radio waves are received by said antenna coil to enable detection of the respective positions and operating statuses of said position designating devices; and   wherein a determination of the correspondence of the frequencies of the received signals with the types of position designating devices is used to effect a differentiation between the different types of said position designating devices.   
     
     
       2. A system according to claim 1, further comprising a switch disposed in each of said tuning circuits for turning on or off the connection between said coil and said capacitors; and wherein, when it is required to designate only a position at which coordinates are to be input, said position designating devices are used by turning on or off said switches. 
     
     
       3. A system according to claim 1, wherein said tablet further comprises a casing made of a non-metallic material such as a synthetic resin, and a tablet body, in addition to said antenna coil, said casing accommodating said tablet body and said antenna coil. 
     
     
       4. A system according to claim 1, wherein each of said position designating devices further comprises, in addition to said tuning circuit, a magnetism generator for designating positions. 
     
     
       5. A system according to claim 1, wherein said antenna coil comprises a conductive wire provided with an insulation coating such as polyvinyl chloride, said conductive wire being disposed around a coordinates input range of said tablet. 
     
     
       6. A system according to claim 1, wherein said tuning circuit has a variable capacitor. 
     
     
       7. The system of claim 1, wherein the antenna coil is disposed around the periphery of the coordinates input range. 
     
     
       8. The system of claim 1, wherein the antenna coil is disposed inside the periphery of the coordinates input range. 
     
     
       9. The system of claim 1, wherein the antenna coil is tooth-shaped for superposing over or below the coordinates input range. 
     
     
       10. The system of claim 1, wherein the antenna coil is spirally-shaped for superposing over or below the coordinates input range. 
     
     
       11. The system of claim 1, further comprising at least two antenna coils one of which is disposed inside the coordinates input range and the other of which is disposed around the coordinates input range. 
     
     
       12. The system of claim 1, further comprising a plurality of antenna coils each for forming a loop disposed around a corresponding portion of the coordinates input range. .Iadd. 
     
     
       13.  A method of identifying which one of plural objects is in proximity to a tablet and the position of the one object relative to the tablet, each of the objects including a tuned circuit having a different resonant frequency, comprising the steps of supplying AC energy at the different resonant frequencies to a coil in the tablet, the tuned circuit on the particular object in proximity to the coil having substantially the same frequency as the AC energy supplied to the coil causing a change in the current flowing in the coil at said same frequency, sensing the change in the current flowing in the coil at said same frequency, responding to the current change at said same frequency to indicate the particular object having the tuned circuit with the same resonant frequency as the frequency of the applied AC energy, and detecting the position of the identified object by coupling energy between the object and the tablet, said tablet including a two dimensional array of detectors, at least some of which interact with the coupled energy..Iaddend. .Iadd.14. The method of claim 13 wherein the energy at the different frequencies is sequentially supplied to the coil..Iaddend. .Iadd.15. The method of claim 14 wherein the change is detected by supplying the coil during a first interval with the AC energy at one of the predetermined frequencies, and responding to energy coupled back to the coil from the tuned circuit during a second interval while the coil is not supplied with the AC energy at the one predetermined frequency..Iaddend. .Iadd.16. In combination, a tablet including a coil, plural objects adapted to be selectively in proximity to the tablet, each of the objects including a tuned circuit having a different resonant frequency, means for supplying AC energy at the different resonant frequencies to the coil, the tuned circuit on the particular object in proximity to the tablet having substantially the same frequency as the AC energy supplied to the coil causing a change in the current flowing in the coil at said same frequency, means for sensing the change in the current flowing in the coil at said same frequency, means responsive to the current change at said same frequency for indicating the particular object having the tuned circuit with the same resonant frequency as the frequency of the applied AC energy and means for detecting the position of the identified object relative to the tablet, said position detecting means coupling energy between the object and the tablet, said tablet including a two-dimensional array of detectors at least some of which interact with the coupled energy..Iaddend. .Iadd.17. The combination of claim 16 wherein the energy at the different frequencies is sequentially supplied to the coil..Iaddend. .Iadd.18. The combination of claim 17 wherein the change is detected by supplying the coil during a first interval with the AC energy at one of the predetermined frequencies, the means for sensing being activated to be responsive to energy coupled back to the coil from the tuned circuit during a second interval while the coil is not supplied with the AC energy at the one predetermined frequency..Iaddend. .Iadd.19. Apparatus for determining which one of plural objects is in proximity to a region and for determining the position of said one object relative to the region, each of the objects including a tuned circuit having a different resonant frequency, comprising a tablet defining the region, the tablet including a coil, means for supplying AC energy at the different resonant frequencies to the coil, the tuned circuit on the particular object in the region having substantially the same frequency as the AC energy supplied to the coil causing a change in the current flowing in the coil at said same frequency, means for sensing the change in the current flowing in the coil at said same frequency and responding to the current change at said same frequency to indicate the particular object having the tuned circuit with the same resonant frequency as the frequency of the applied AC energy, and means for detecting the position of the identified object relative to the tablet, said position detecting means coupling energy between the object and the tablet, said tablet including a two dimensional array of detectors at least some of which interact with the coupled energy..Iaddend. .Iadd.20. The apparatus of claim 19 wherein the energy at the different frequencies is sequentially supplied to the coil..Iaddend. .Iadd.21. The apparatus of claim 20 wherein the change is detected by supplying the coil during a first interval with the AC energy at one of the predetermined frequencies, the means for sensing being activated to be responsive to energy coupled back to the coil from the tuned circuit during a second interval while the coil is not supplied with the AC energy at the one predetermined frequency..Iaddend. .Iadd.22. Apparatus for determining the position of and which one of plural characteristics is included in an implement relative to a detecting surface, the implement including a tuned circuit having a predetermined resonant frequency identifying the characteristic, a different resonant frequency being associated with each characteristic, comprising a tablet in the region for coupling energy to the implement,   a coil associated with the tablet for supplying AC energy at the different resonant frequencies to the tuned circuit, the tuned circuit on the implement having substantially the same frequency as the AC energy supplied to the coil causing a change in the current flowing in the coil at said same frequency, and   means for sensing the change in the current flowing in the coil at said same frequency and responding to the current change at said same frequency for indicating the identified characteristic associated with the tuned circuit with the same resonant frequency as the frequency of the applied AC energy, and responsive to energy coupled between the tablet and the implement for indicating the position of the implement relative to the tablet..Iaddend. .Iadd.23. The apparatus of claim 22 wherein the energy at the different frequencies is sequentially supplied to the coil..Iaddend. .Iadd.24. The apparatus of claim 23 wherein the change is detected by supplying the coil during a first interval with the AC energy at one of the predetermined frequencies, the means for sensing being activated to be responsive to energy coupled back to the coil from the tuned circuit during a second interval while the coil is not supplied with the AC energy at the one predetermined frequency..Iaddend. .Iadd.25. In combination, a position sensing tablet, a coil associated with the tablet, an implement having one of plural characteristics adapted to be selectively placed proximate the tablet, the tablet and the implement having structures for coupling energy between them, the implement including a tuned circuit having a resonant frequency associated with the one characteristic, different ones of said characteristics having different resonant frequencies associated therewith, means for supplying AC energy at the different resonant frequencies to the coil, the tuned circuit on the implement in proximity to the coil having substantially the same frequency as the AC energy supplied to the coil causing a change in the current flowing in the coil at said same frequency, means for sensing the change in the current flowing in the coil at said same frequency and responding to the current change at said same frequency for indicating the characteristic of the implement having the tuned circuit with the same resonant frequency as the frequency of the applied AC energy and responding to the energy coupled between the implement and the tablet for indicating the position of the implement on the tablet..Iaddend. .Iadd.26. The combination of claim 25 wherein the energy at the different frequencies is sequentially supplied to the coil..Iaddend. .Iadd.27. The combination of claim 26 wherein the change is detected by supplying the coil during a first interval with the AC energy at one of the predetermined frequencies, the means for sensing being activated to be responsive to energy coupled back to the coil from the tuned circuit during a second interval while the coil is not supplied with the AC energy at the one predetermined frequency..Iaddend.