JPH0616255B2 - Coordinate input device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate input device, and more particularly to a coordinate input device that detects a designated position using elastic waves.

[Prior Art] The principle of this type of device will be described. An oscillating coordinate input pen is used to specify an arbitrary position on the coordinate input plate, and an elastic wave propagating on radiation is predetermined from the specified position. The coordinate position designated by the coordinate input pen is calculated by measuring the delay time required for reception by the receiving element fixed at the position and propagating to each receiving element.

Conventionally, the elastic wave detected by the receiving element is a surface wave, and the peak position of the envelope of the detection signal (composed of a plurality of pulses) detected by the receiving element and converted into an electric signal, or a certain threshold value. The propagation delay time of the surface wave was detected at the time when the signal generated by comparing with the hold level was detected.

[Problems to be Solved by the Invention] However, when a surface wave is used as a detection wave, scratches or objects (such as a hand or a pen) on the propagation medium (coordinate input plate) cause the surface wave to be transmitted (coordinate input pen). Between) and the reception point (reception element), the propagation time of the surface wave may change or may not propagate, which makes it impossible to calculate an accurate coordinate position.

Therefore, it is conceivable to use a plate elastic wave that is less affected by obstacles, but at this time, the group velocity and the phase velocity of the plate elastic wave differ. This will be explained as shown in FIG. In the figure, 8 is a detection wave detected by the receiving element, and 9 is an envelope curve that combines the peaks of the detection wave 8. In the waveform of detection wave 8, when chasing one wave group and looking, it seems that the peaks of the detection wave (hereinafter referred to as small waves) appear at the front end of the wave group and disappear at the rear end. Or, conversely, it occurs at the rear end of the wave group and appears to disappear at the front end. Further, in the envelope 9 in which the peaks of small waves are combined in this phenomenon, the position (phase) of the small waves changes depending on the propagation delay time, so the shape of the envelope changes with the position (phase) of the small waves. Will end up. That is, if the peak of the envelope 9 that combines the peaks of small waves is detected and this is used as a signal for detecting the propagation delay time, the same change as the change of the small waves will occur. An error of ± 1/2 wavelength will occur. Further, even if a certain threshold level is set and a signal exceeding the threshold level is used as a propagation detection point, an error of ± 1/2 wavelength will occur within the range 10 of FIG. 3 for the same reason as above. There was a drawback.

The present invention has been made in view of the above-mentioned conventional technology, and it is possible to eliminate fluctuations in vibration detection timing even when using plate acoustic waves having different group velocities and phase velocities, and to enable a coordinate to be obtained with high accuracy. It is intended to provide an input device.

[Means for Solving Problems] In order to solve this problem, the present invention has the following configuration.

Calculate the gauge position.

That is, a vibration input means for inputting a vibration, a propagation member for propagating the vibration inputted by contacting the vibration input means, and a vibration provided on the propagation member and inputted by the vibration input means. Detecting means for detecting a plate acoustic wave propagating through the propagation member; envelope detecting means for detecting an envelope waveform of a signal formed by the plate elastic wave detected by the detecting means; and the envelope. In order to obtain the inflection point position of the envelope waveform detected by the detecting means, a differentiating means for differentiating the envelope twice and a zero-cross point corresponding to the inflection point position obtained by the differentiating means are detected. Zero-cross point detection means, and a vibration input in the propagation member based on the propagation delay time to the zero-cross point detected by the zero-cross point detection means and the group velocity of the plate elastic wave. And having a deriving means for deriving a coordinate.

[Operation] In the configuration of the present invention, the envelope waveform is differentiated by the differentiating means, the zero-cross point of the output differential waveform is detected, the delay time until the zero-cross point is detected is measured, and the time is measured. The position coordinates of the vibration input point are calculated based on the delay time.

Embodiments Embodiments according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is an overall configuration diagram of the coordinate input device of this embodiment.
In the figure, 1a to 1c are sensors such as piezoelectric elements, 2 is a propagation medium (eg glass) for transmitting plate wave elastic waves, 3 is a vibrating pen for generating plate wave elastic waves in the propagation medium 2, and 4 is vibration. A vibrating pen drive circuit for driving the pen 3 and a sensor 1
It is a reception waveform detection circuit that amplifies the signal of the plate acoustic wave received at a to 1c and detects a pulse signal for counting the delay time. The details of the received waveform detection circuit 5 will be described later. Reference numeral 6 denotes an operation control unit that measures the time until the signal received from the received waveform detection circuit 5 is detected and operates to detect the coordinate (position of the vibrating pen). The calculated coordinate data is an internal data storage area. Stored in. The arithmetic control unit 6 also performs control such as displaying points in real time on the display 7 based on the calculated coordinate data. Furthermore, the arithmetic control section 6 outputs a signal for driving the vibrating pen 3 to the vibrating pen drive circuit 4. Therefore, the arithmetic control unit 6 measures the time from the output of the signal to the vibrating pen drive circuit 4 to the reception of the signal indicating the reception by the reception waveform detection circuit 5.

With the configuration described above, the vibrations generated by the vibrating pen 3 are respectively received by the sensors 1a to 1c transmitted through the propagation medium 2, and the delay time of the signal is detected to calculate the coordinate position on the propagation medium. As a method of detecting the propagation delay time, the waveform received by the sensor 1a (similarly for the sensors 1b and 1c) has a waveform as shown in FIG. Also, the envelope signal 9 is propagated at a group velocity, and is propagated at different velocities. As this phenomenon, the waveform of the detection signal 8 does not appear in a constant phase, and the waveform has a different phase depending on the distance between the vibrating pen 3 and the sensor 1a. Therefore, when the peak of the detection signal 8 is detected with a threshold of a certain level, a peak exists within the range 10 in FIG. 3, and when this is detected and the propagation delay time is detected, it corresponds to the width of the range 10. Error will occur. Therefore,
In order to reduce this error and increase the accuracy, in the present embodiment, the shape of the envelope signal 9 as shown in FIG. 2 is used for detection.

Details of the detection waveform 8 are shown in FIG. The envelope of the detected waveform is detected and the part of the range 11 is used. That is, the slope of the envelope 12 of the range 11 is created by the envelope connecting the peaks of a plurality of small waves. Therefore, the slope of the range 11 is formed without being affected by the position (phase) of the small wave having the above-mentioned drawback, and one point in this slope is always detected. For example, as shown in FIG. 5, the envelope 12 is differentiated twice, the zero-cross point is detected, and the signal 15 is used as a signal of the propagation delay time to be calculated by the calculation control unit 6 to obtain the coordinate position. . The waveform obtained by differentiating the envelope 12 once is 13 in FIG. 5, and the waveform obtained by differentiating twice is 14.
Further, reference numeral 15 is a signal for receiving and detecting the plate elastic wave.

This detection point becomes a zero-cross point having a steeper slope than the zero-cross point of the first differential waveform, and the detection becomes more accurate.

FIG. 6 shows a specific configuration example of the reception waveform detection circuit 5 that performs the above-described operation processing. Although only the sensor 1a is described here, the same applies to the other sensors 1b and 1c.

Now, the waveform received by the sensor 1a is amplified by the preamplifier 16, and the envelope detection circuit 17 detects the envelope. This envelope is differentiated twice by differentiating circuits 18 and 19. The first zero-cross point of this waveform is detected by the zero-cross detection circuit 20, and this signal is sent to the calculation / control section 6 to calculate the coordinate position.

As described above, according to the present embodiment, when the coordinate position detection is performed using the plate elastic wave, the position detection difficulty due to the difference between the group velocity and the phase velocity is solved, and a highly accurate coordinate input device is provided. Becomes Further, if the detection is performed based on the inclination of the front part of the envelope, the detection point obtained therefrom can be detected as the coordinate position based on the group velocity. As a result, a transparent coordinate input device using glass or the like can be manufactured, and an input / output integrated digitizer with high accuracy can be manufactured.

Further, as described in the present embodiment, basically, it is only necessary to be able to capture the delay time based on the accurate group velocity. Therefore, a point having a waveform obtained by differentiating the envelope twice is set as the coordinate position. Alternatively, it may be detected as the position of the beginning of the waveform obtained here or the position of a certain threshold.

[Effects of the Invention] As described above, according to the present invention, even when using plate acoustic waves having different group velocities and phase velocities, there is no fluctuation in the vibration detection timing, so it is possible to obtain the indicated position with high accuracy. become.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of the present embodiment, FIG. 2 is a diagram showing a received signal waveform, FIG. 3 is a diagram showing an existing range of a peak of a signal serving as a carrier, FIG. 4 is a diagram showing a detected waveform, FIG. 5 is a diagram showing the waveform processed by the differentiating circuit, and FIG. 6 is a diagram showing the configuration of the received waveform detecting circuit. In the figure, 1a to 1c ... Sensor, 2 ... Propagation medium, 3 ... Vibration pen, 4 ... Vibration pen drive circuit, 5 ... Received waveform detection circuit,
6 ... Arithmetic / control section, 7 ... Display, 8 ... Received signal waveform, 9 ... Diagram showing envelope of received signal, 10 ... Possible range of peak of received signal waveform, 16 ... Preamplifier circuit, 17
... Envelope detection circuit, 18, 19 ... Differentiation circuit, 20 ... Zero cross detection circuit.

Claims (1)

[Claims] 1. A vibration input means for inputting vibration, a propagation member for propagating vibration inputted by contacting the vibration input means, and a propagation member provided on the propagation member and inputted by the vibration input means. Detecting means for detecting a plate elastic wave propagating through the propagation member by vibrating vibration, and envelope detecting means for detecting an envelope waveform of a signal formed by the plate elastic wave detected by the detecting means, In order to obtain the inflection point position of the envelope waveform detected by the envelope detection means, differentiating means for differentiating the envelope twice, and a zero-cross point corresponding to the inflection point position obtained by the differentiating means A zero cross point detecting means for detecting a vibration input to the propagation member based on the propagation delay time to the zero cross point detected by the zero cross point detecting means and the group velocity of the plate elastic wave. Coordinate input device characterized in that it comprises a derivation means for deriving the coordinates of the point.