JPS5824827B2 - coordinate reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coordinate reading device that reads the coordinates of a designated position by detecting a magnetic field.

Coordinate reading devices with various configurations have already been proposed and put into practical use, but a coordinate reading device that detects alternating current magnetic fields with different phases is one that enables highly accurate coordinate reading with a relatively simple configuration. The device was first proposed.

For example, as shown in FIG. 1, a flat plate 2 is placed on an alternating current magnetic field generating section 1, and a position on the flat plate 2 is indicated by a pen-shaped magnetic field detector 3.

The alternating current magnetic field generating section 1 has a diameter of φ1. φ2. φ3. . . . Magnetic fields with different phases are generated by excitation from the drive circuit 6, and the detection signal of the magnetic field detector 3 is phase-detected by the phase detector 4 according to the reference excitation phase, and then sent to the processing device 5. The processing device 5 adds the detection output, identifies the coordinates of the indicated position of the magnetic field detector 3 from the detection output, and outputs the coordinate information.

The magnetic field detector 3 is constituted by a resonant circuit tuned to the fundamental frequency of the alternating current magnetic field generator 1 in order to increase detection sensitivity and improve S/N.

Therefore, near the resonance point of the resonant circuit, the phase change rate is large,
The resonant frequency changes due to changes in temperature and the like.

For example, since the magnetic field detector 3 is pen-shaped and held in the hand, the body temperature of the user is conducted during use and the temperature rises, which may change the resonance frequency as described above.

When the resonant frequency of the magnetic field detector 3 changes, the detection output of the phase detector 4 also changes, resulting in an error in coordinate reading.

An object of the present invention is to compensate for errors in coordinate reading as described above and to enable accurate coordinate reading.

The actual case will be explained in detail below.

FIG. 2 is a block diagram of an actual case of the present invention. Like the magnetic field generating section 1 in FIG. The detector 13 gives an indication, and the detected signal is applied to the phase detector 14.

The magnetic field detector 13 includes, for example, a coil 13a and a capacitor 1.
3b is provided, and the alternating current magnetic field generating section 1
It is set to tune to the fundamental frequency of 1.

When used for inputting handwritten characters, the magnetic field detector 13 has the structure of a writing instrument such as a pen, ballpoint pen, or pencil that can write characters on a sheet of paper placed on the flat plate 12.
An alternating current magnetic field generating section 17 that generates an alternating current magnetic field of a reference phase is provided at a position on the flat plate 12 that is not used for coordinate reading,
A switch 19 is provided which operates when the AC magnetic field generator 17 and the magnetic field detector 13 are coupled at the chain line position.

Note that 15 is a processing device, 16 is a drive circuit for causing the AC magnetic field generator 11 to generate AC magnetic fields with different phases, 18 is a drive circuit for causing the AC magnetic field generator 17 to generate an AC magnetic field with a reference phase, and 20 21 is a memory, and 21 is an arithmetic unit.

χ−f( of the relationship between the phase θ of the magnetic field on the flat plate 12 and the position χ
can be accurately identified by the processing device 15 if there is no change in temperature or the like, but as described above, a phase error Δθ occurs due to fluctuations in the resonant frequency of the resonant circuit of the magnetic field detector 13.

Therefore, before or during use, the magnetic field detector 13 is coupled to the AC magnetic field generator 17 of the reference phase, and at that time, the switch 19 is turned on at the tip of the magnetic field detector 13 or manually to notify the processing device 15.

The processing device 15 stores the detection output of the phase detector 14 at this time in the memory 20.

When the magnetic field detector 13 detects the alternating current magnetic field of the reference phase, if the detection output of the phase detector 14 is zero, it is coupled to the alternating current magnetic field generator 17, and the resonant frequency of the resonant circuit of the magnetic field detector 13 is If there is no change, the detection output of the phase detector 14 at the time when the switch 19 is turned on becomes zero.

However, if the resonant frequency of the resonant circuit changes, a corresponding detection output will appear.

That is, a phase error Δθ will occur.

Information on this phase error Δθ, that is, error component Δχ=f(Δθ)
is stored in the memory 20.

j The area where there is a linear relationship between the phase θ of the magnetic field on the flat plate 12 and the position χ is used as the usage area, and the detection obtained by indicating the position χ1 on the flat plate 12 with the magnetic field detector 13 If the phase is θ1, the processing device 15 calculates Δχ−f(Δθ) of the storage content 4 of the memory 20.
is read out and the arithmetic unit 21 calculates χ1=f(θ1)−f(Δθ), thereby outputting the correct coordinate position χ1 with the phase error corrected.

That is, in an ideal state, the coordinate position χ1 (=f(θ1)) obtained from the output of the phase detector 14 does not include an error component due to the phase error Δθ, but as described above, due to fluctuations in the resonance frequency etc., it actually contains an error component due to the phase error Δθ, so phase error information obtained by coupling the magnetic field detector 13 to the AC magnetic field generator 17 of the reference phase is stored in the memory 20 in advance. Ok,
By reading out the phase error information from the memory 20 and subtracting it, it is possible to obtain the correct coordinate position χ1 with the phase error corrected.

Note that the reference phase can of course be any phase other than the phase at which the output of the phase detector 14 is zero, and in that case, if there is no phase error, a predetermined constant phase detection output will be obtained.

Further, the drive circuits 16 and 18 can also be shared.

Also, the memory 20 is updated every time the switch 19 is turned on.
The phase detected by the magnetic field detector 13 can be corrected using the latest phase error Δθ.

Further, the position of the AC magnetic field generator 17 can also be the resting position of the magnetic field detector 13.

As explained above, the present invention provides an alternating current magnetic field generator 17 with a reference phase outside the coordinate reading range, and processes phase information when the magnetic field detector 13 is coupled to the alternating magnetic field generator 17 as phase error information. stored in the memory 20 of the device 15;
The detection phase of the magnetic field detector 13 obtained by coupling with the alternating current magnetic field generator 11 that generates alternating magnetic fields with different phases is corrected by the phase error Δθ stored in the memory 20 in the processing device 15. Thereby, errors in the detection phase due to changes in the resonance frequency of the resonance circuit of the magnetic field detector 13 can be corrected, and accurate coordinate reading can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for explaining the previously proposed coordinate reading device, and FIG. 2 is a block diagram for explaining the present invention in detail. 11 is an alternating current magnetic field generator, 12 is a flat plate, 13 is a magnetic field detector, 14 is a phase detector, 15 is a processing device, 16, is 1
17 is a reference phase alternating current magnetic field generator; 19 is a switch; 20 is a memory; and 21 is a calculation unit.

Claims (1)

[Claims] 1 Coordinate reading in which an alternating current magnetic field whose phase differs depending on the position on a flat plate is generated by an alternating current magnetic field generator, and the coordinates of the indicated position of the magnetic field detector are identified by a processing device based on the detection phase of the alternating magnetic field detected by a magnetic field detector. In the apparatus, an AC magnetic field generator of a reference phase is provided outside the coordinate reading range on the flat plate, and a memory is provided that stores the detected phase when the AC magnetic field generator and the magnetic field detector are combined as phase error information. A coordinate reading device, characterized in that it is provided in the processing device.