Computer graphics processing and selective visual display system – Display peripheral interface input device – Touch panel
Reexamination Certificate
1998-09-14
2001-05-29
Hjerpe, Richard (Department: 2776)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Touch panel
C345S173000, C345S174000, C345S175000, C345S176000, C345S177000
Reexamination Certificate
active
06239789
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a position detecting method and apparatus in a position detector such as a digitizer or tablet and, more particularly, to an improvement in a method and apparatus for scanning many sensor coils provided side by side on a sensor unit of the position detector.
2. Description of Related Art
A variety of position detecting methods in position detectors have been known. For example, U.S. Pat. No. 5,466,896, the disclosure of which is hereby incorporated by reference, and Japanese published patent application No. 3-147012 disclose an electromagnetic transfer system.
FIG. 7
is a schematic block diagram illustrating the basic operation of a position detector employing an electromagnetic transfer system.
A position indicator
110
shown in
FIG. 7
has a resonance circuit
101
composed of a coil and a capacitor. A position detector
111
is constituted by a sensor unit
102
, a coil selector
103
, a send/receive selector
104
, a high-frequency signal generator
105
, a receiving circuit
106
, and a signal processing unit
107
. The position indicator
110
preferably has a pen shape or a puck shape. The pen shape suggests a writing tool that indicates a position when it is held in a hand of an operator. The puck shape suggests a cursor that continues to indicate a position even when the operator releases it, i.e. it can be left alone. The operator holds the position indicator
110
to specify a position (pointing entry), enter hand-written characters, drawing, or to perform other coordinate input operation on a computer. The position indicator
110
includes at least a coil or the resonance circuit
101
.
The sensor unit
102
has a plate-like sensor surface, a point on which is defined by an X-Y rectangular coordinate. The sensor unit
102
is formed by arranging many sensor coils
100
side by side in an X-axis direction
108
and a Y-axis direction
109
. In
FIG. 7
, only the sensor coils arranged in the X-axis direction are shown in order to avoid confusion. There are actually a few tens of the sensor coils; however, only three sensor coils are illustrated in the drawing for clarity.
In the position detector
111
which employs the electromagnetic transfer system, electromagnetic waves are transferred between the sensor coils
100
on the sensor unit
102
and the position indicator
110
in order to determine the coordinate value of a position specified by the position indicator according to a signal received by the sensor coils
100
. Further, the position detector
111
is preferably provided with means for entering information from the switch of the position indicator or information on writing pressure in addition to the information on the coordinate value of the position indicator.
Two sets of sensor units are normally provided. The two sets of coils are preferably orthogonalized in the X-axis direction and the Y-axis direction, respectively, in order to perform coordinate detection in two directions, namely, the X-axis direction and the Y-axis direction. In this case, it should be noted that “the sensor coils in the X-axis direction” means that they are arranged in the X-axis direction rather than meaning that they are extended in the X-axis direction. As illustrated in
FIG. 7
, the lengthwise direction of the sensor coils in the X-axis direction agrees with the Y-axis direction.
The high-frequency signal generator
105
is a circuit for generating an AC signal of a predetermined frequency (e.g. a predetermined value in a range from a few hundreds of kilohertz to a few megahertz). The receiving circuit
106
is a circuit composed primarily of an amplifier. The signal processing unit
107
is composed primarily of a processor (CPU) and a storage circuit; it carries out XY-coordinate calculation according to the output of the receiving circuit
106
. The processor of the signal processing unit
107
functions to control the coil switching of the coil selector
103
and the switching of the send/receive selector
104
. For the purpose of clarity, the signal lines for controlling the coil selector
103
and the signal lines for controlling the send/receive selector
104
are omitted in FIG.
7
. The coil selector
103
may be constituted by a well-known multiplexer. Likewise, the send/receive selector
104
may be constituted by a well-known switching circuit.
The position detecting process in the electromagnetic transfer system will now be described. It is assumed that the foregoing processor of the signal processing unit
107
has set the send/receive selector
104
for the send mode, namely, for the high-frequency signal generator
105
, and the processor has set the coil selector
103
to select one particular sensor coil
100
in a sensor coil group of the sensor unit
102
.
The high-frequency signal generator
105
generates a high-frequency signal and applies that signal to the selected sensor coil
100
via the send/receive selector
104
and the coil selector
103
. The sensor coil
100
then produces an electromagnetic wave that will be referred to as “transmitter signal.” When the position indicator
110
is placed near the sensor surface under this condition, the resonance circuit
101
in the position indicator
110
resonates due to the transmitter signal. Then, the processor of the signal processing unit
107
sets the send/receive selector
104
to the receive mode, namely, for the receiving circuit
106
, to stop the issuance of the transmitter signal from the sensor coil
100
. In other words, the supply of the high-frequency signal from the high-frequency signal generator
105
is stopped.
Under this condition, the oscillatory phenomenon in the resonance circuit
101
incorporated in the position indicator
110
does not stop immediately; damping oscillation continues for a while. Hence, the coil of the resonance circuit
101
generates an electromagnetic wave that will be referred to as a “response electromagnetic wave.” The sensor coil
100
receives this response electromagnetic wave, and the signal received by the sensor coil
100
at this time will be referred to as a “received signal”. The received signal is sent to the receiving circuit
106
, where it is processed, via the coil selector
103
and the send/receive selector
104
. The signal which has been processed by the receiving circuit
106
is further handed to the signal processing unit
107
which performs XY coordinate calculation and the analysis of switch information according to the amplitude, phase, and so on of the processed signal. The obtained coordinate value and switch information are sent out to a host apparatus not shown, i.e. an external computer.
The resonance circuit
101
in the position indicator
110
shown in
FIG. 7
is represented as a coil or the resonance circuit
101
because the resonance phenomenon is not necessary as long as magnetic coupling takes place between the sensor coils.
The sending and receiving operation of the sensor coils
100
is repeated while switching in sequence among the multiple sensor coils
100
on the sensor unit
102
in a position detecting direction. The operation of switching among the multiple sensor coils
100
in sequence will be referred to as “scanning”.
It has already been mentioned that, among the components making up the position detector
111
, the coil selector
103
composed mainly of a multiplexer is primarily responsible for selecting and switching among the multiple sensor coils
100
. Also, it has already been mentioned that the coil selector
103
is connected to the processor of the signal processing unit
107
by a signal line, which is not shown, and it is controlled by the processor. The program describing the operation of the processor is stored in a storage device called a ROM (read-only memory) of the signal processing unit
107
. The storage device is preferably a component of the position detector. The processor reads the program stored in the ROM and executes the scanning according to the program. Accordingly, the position d
Katsurahira Yuji
Sekizawa Yasushi
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Hjerpe Richard
Lesperance Jean
Wacom Co. Ltd.
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