Telegraphy – Systems – Position coordinate determination for writing
Patent
1993-12-29
1996-10-22
Chin, Stephen
Telegraphy
Systems
Position coordinate determination for writing
178 19, 178 20, G08C 2100
Patent
active
055679200
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a position reading apparatus for inputting position information into an external device such as computers, and specifically relates to a wireless position reading apparatus in which a body of a detecting device and a position pointer do not need connecting with a signal wire.
Further, the present invention relates to a key board apparatus which outputs switch information to a host system such as a computer, and specifically relates to a key board apparatus applying an oscillation phenomenon.
BACKGROUND ART
FIG. 35 is a block diagram of a conventional position reading apparatus. First of all, referring to this drawing there will be described operation for detecting a position in the conventional position reading apparatus.
The apparatus has a structure that exciting lines 903 and sense lines 902 are laid orthogonally, and each exciting line 903 is sequentially selected by being coupled to a first scanning circuit 908 in turn and each sense line 902 is sequentially selected by being coupled to a second scanning circuit 909 in turn. As the first scanning circuit 908 is supplied with an exciting signal s906 from an exciting circuit 915, the exciting line selected by this circuit generates an a.c. electromagnetic field. A position pointer 906 includes a resonant circuit (hidden from the Figure) which resonants with a frequency of the exciting signal s906. Therefore, when the position pointer is put on the sense lines, induction signals s901 generate on the sense lines 902 because of the coupling among the exciting lines 903, the position pointer 906 and the sense lines 902. The second scanning circuit 909 selects each of the sense lines sequentially and thereby the induction signal s901 is guided to a signal processing circuit 904 and is converted into an amplitude signal s905. Further, the amplitude signal is inputted into a position detecting circuit 905 and then the position is calculated from a distribution state as to the induction signal s901 at an intersection point of each exciting line and each sense line.
It is necessary to select a plurality of the sense lines in order to obtain the distribution state as to the induction signal s901. In such a conventional position reading apparatus as explained above, calculating the position of one point requires performing selecting operations in matrix in a way that a plurality of the sense lines are selected while each of the exciting lines is selected. For instance, if the five exciting lines and the five sense lines are to be selected respectively, the position of a point is calculated by performing twenty five times of selecting operations in total because the five sense lines are selected whenever one of the exciting lines is selected.
Next, referring to FIGS. 36A and 36B, there will be described an operation for detecting a state of switches and so on provided for the position pointer in the conventional position reading apparatus.
As shown in FIG. 36A, the position pointer 906 has a construction that the position pointer 906 includes a resonant circuit 907 and the resonant circuit 907 is connected in parallel to a switching circuit 913 in which the switch and a second capacitor are connected in series. Then, when the switch is pushed, a resonance frequency slightly changes.
Therefore, as shown in FIG. 36B, a phase of the induction signal s901 is slightly different between when the switch is on and when the switch is off. A state of the switching circuit 913 can be detected by detecting this phase change .phi..
Further when a number of switches are provided on the position pointer and many status are required or when the condition settings are required to extend in such the conventional position reading apparatus, for example, by providing a pressure detecting function with the position pointer, such requirements are realized in a manner mentioned below. Detection accuracy is ensured by providing the main body with a detecting circuit capable of detecting a slight change in phase accurately and also stabl
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patent: 4926010 (1990-05-01), Citron
patent: 4959805 (1990-09-01), Ohouchi et al.
patent: 4988837 (1991-01-01), Murakami et al.
patent: 5028745 (1991-07-01), Yamanami et al.
European Search Report dated Jul. 28, 1994, European application No. 93904347.7.
Morita Yoshiyuki
Saeki Shinji
Watanabe Toshiaki
Chin Stephen
Seiko Instruments Inc.
Shankar Vijay
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