JPH04313781A - Coordinate input device - Google Patents

Abstract

PURPOSE:To improve the measuring accuracy by executing a signal processing after executing full-wave rectification of a detection output of AC of a vibration sensor, and utilizing effectively both positive and negative cycles of a vibration detection waveform for the, signal processing. CONSTITUTION:When the tip of an indicator 2 is pressed against the surface of an operating plate 1 and a switch is turned on, a vibration pulse is generated intermittently in a prescribed period from the indicator 2, and its vibration is propagated along the surface of the operating plate 1. Each vibration sensor 3-6 detects this vibration, and outputs a vibration waveform of AC. This vibration detecting signal is inputted to a full-wave rectifying circuit 8 through a pre-amplifier 7, respectively, to generate a vibration waveform subjected to full-wave rectification. The vibration detecting signal is compared with thresholds A, B by comparators 9a, 9b, and an output of the comparator 9b is inputted to a coordinate arithmetic part 13 as a vibration detection timing signal of the sensors 3-6, and a coordinate value of an indicated point by the indicator 2 is derived. Also, in the case the time for exceeding both the thresholds A, B is too long, the arithmetic processing of the coordinate value is invalidated.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] This invention applies vibration to the surface of an operation panel such as a glass plate using a pen-shaped indicator, and transmits the vibration to a plurality of devices installed around the operation panel. The present invention relates to a coordinate input device that detects with a vibration sensor and calculates coordinate values of a point indicated by an indicator (vibration application point) from the detection signal.

0002

[Prior art] Acoustic emission (AE)
) This type of coordinate input device applying the principle of measurement is explained in Japanese Patent Application Laid-Open No. 63-244068,
This method is suitable for applications in which a document is placed on the glass plate of a copying machine and an indicator is placed over the document to specify a partial copy area of the document.

In the conventional coordinate input device of this type, a plurality of vibration sensors are installed around the surface of the operation panel, and a pen (indicator) containing a suitable excitation means is used to vibrate the operation panel. The coordinate value of the indicated point (the point where the vibration was applied) is calculated based on the difference between the timing when the vibration was added and the timing when the vibration was detected by each sensor.

0004

In this type of coordinate input device, the vibration detection signal output from the vibration sensor (piezoelectric element) has an AC vibration waveform as shown in FIG. In the conventional device, the vibration detection timing was determined by comparing the levels of this alternating current signal and an appropriate unipolar threshold value A. This caused the following problems. (1) Since the level is discriminated only based on the polarity of one side of the AC vibration waveform, it is inevitable that an error of half a cycle of the vibration frequency will occur, making it impossible to improve the accuracy. (2) Since the level is discriminated only by the polarity of one side of the sensor output, it is necessary to connect the plurality of sensors to the circuit with the same polarity, which takes time and effort to implement the circuit. (3) If the vibration applied by the indicator is not appropriate, the level of the vibration waveform of the sensor output will slowly increase. The waveform cycle used as the vibration detection timing often differs. The error caused by this was very large in conventional devices.

The present invention was made in view of the above-mentioned conventional problems, and its purpose is to realize a coordinate input device that can be implemented without regard to the polarity of the sensor and has fewer errors than the conventional coordinate input device. .

[0006]

[Means for Solving the Problem] Therefore, in the present invention, an operation plate through which vibrations propagate, a plurality of vibration sensors installed around the operation plate surface, and a plurality of vibration sensors that come into contact with an arbitrary position on the operation plate surface are provided. an indicator that applies a vibration pulse of a predetermined frequency to the position, a timing determination means for determining the vibration detection timing of the plurality of vibration sensors, and a timing determination means for determining the vibration detection timing of each of the vibration sensors determined by the determination means. A coordinate input device comprising a calculation means for performing a comparison calculation to obtain a coordinate value of a vibration application point by the indicator, wherein the timing determination means is provided with a full-wave rectified alternating current detection signal output from the vibration sensor. Further, in the second invention, a full-wave rectification circuit is provided for converting the pulse wave into a pulse wave, and the timing determining means compares the levels of the full-wave rectified detection signal with two different threshold values A and B to detect a small pulse wave. means for detecting the time between the timing at which the threshold value A is exceeded and the timing at which the large threshold value B is exceeded; and means for invalidating the corresponding detection signal when the time period is greater than a specified value. Established.

[0007]

[Operation] By performing full-wave rectification of the output of the sensor, both polarities of the vibration waveform are effectively utilized for level discrimination and timing determination, thereby improving accuracy. Furthermore, since the polarity of the sensor becomes meaningless, there is no need to take this into account during implementation.

Furthermore, if the level of the vibration waveform of the sensor output slows down for some reason, the accuracy of calculating the coordinate values is no longer guaranteed as described above, but in this case, the thresholds A and B are The time difference between the timings exceeded becomes larger than the specified value, the vibration waveform at this time becomes invalid, and the process moves to detecting the next vibration to be applied.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic configuration of a coordinate input device according to an embodiment of the present invention. Reference numeral 1 denotes an operation panel made of a glass plate, and vibration sensors 3, 4, 5, and 6 are installed at the center of the operation panel near the four sides of its surface, respectively. Here, the direction connecting the vibration sensors 3 and 4 is the X axis, and the vibration sensors 5 and 6 are the Y axis, and the position on the operation panel 1 is expressed using this orthogonal coordinate system. 2 is a pen-like indicator that is operated by hand. The indicator 2 includes piezoelectric ceramics as an oscillation source, a drive circuit for driving the same at a predetermined frequency, a switch, a power source battery, and the like. When you press the tip of the indicator 2 against the surface of the operation panel 1 and turn on the switch,
Vibration pulses are intermittently generated from the indicator 2 at a predetermined period, and the vibrations propagate along the surface of the operation panel 1. Each of the vibration sensors 3 to 6 detects this vibration and outputs an AC vibration waveform as shown in FIG.

The vibration detection signals outputted from each of the vibration sensors 3 to 6 are respectively inputted to a full-wave rectifier circuit 8 via a preamplifier 7, and become full-wave rectified vibration waveforms as shown in FIG. The full-wave rectifier circuit 8 includes an inverting amplifier 81, two diodes 82 and 83, and an inverting adder 84.

The full-wave rectified vibration detection signals of each of the vibration sensors 3 to 6 are sent to the comparator 9a, which is the smaller threshold value A.
It is compared with the larger threshold value B by the comparator 9b. Flip-flop 10 is set when the level of the vibration detection signal (full-wave rectified signal) exceeds threshold value A for the first time, and then reset when it exceeds threshold value B. The timer 11 counts the time T during which the flip-flop 10 is set. This situation is shown in FIG.

On the other hand, the outputs of the comparators 9b for the outputs of the vibration sensors 3 to 6 are input to the coordinate calculation unit 13 as vibration detection timing signals for each sensor. The coordinate calculation unit 13 processes these vibration detection timings using a well-known algorithm to obtain the coordinate values of the point indicated by the indicator 2.

Further, the time T counted by each timer 11 for the output of each vibration sensor 3 to 6 is input to an invalidity determining section 12. The invalidity determination unit 12 checks whether each count time T is within a preset specified value, and if any of the count times T exceeds the specified value, a notification is sent to the coordinate calculation unit 13. Then, a command is given to invalidate the coordinate calculation based on the current vibration detection signal. Note that the invalidity determining unit 12 performs control to clear the flip-flop 10 and the timer 11 in preparation for processing the next vibration detection signal.

When the rise of the vibration detection signal is steep as shown in FIG. 2(A) (this is a preferable state),
The count time T by the timer 11 is small, and the calculation of coordinate values is effective. On the other hand, as shown in Figure 2 (B),
If the rise of the vibration detection signal is slow (this tends to occur when the pressing force of the indicator 2 against the operation panel 1 is insufficient), the count time T by the timer 11 becomes larger than the specified value, and the calculation of the coordinate values becomes invalid. Become.

[0015]

[Effects of the Invention] In this invention, the AC detection output of the vibration sensor is full-wave rectified before signal processing.
Both positive and negative cycles of the vibration detection waveform are effectively used for signal processing, improving measurement accuracy. In addition, by full-wave rectification, the connection polarity of the vibration sensor can be set freely, eliminating the conventional trouble of mounting a plurality of vibration sensors with the same connection polarity.

Furthermore, the full-wave rectified vibration detection signal is level-discriminated using two thresholds, large and small, and if the time between exceeding both thresholds is too long, the coordinate values are calculated using the vibration detection signal. is disabled, so inaccurate coordinate values will not be output when vibration cannot be applied correctly using the indicator. The reliability of the device is therefore increased.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a coordinate input device according to an embodiment of the present invention.

[Figure 2] Waveform diagram for explaining the operation of the above device

[Figure 3] Waveform diagram to explain problems with conventional equipment

[Explanation of symbols]

1 Operation board 2 Indicator 3-6 Vibration sensor 8 Full wave rectifier circuit 9a, 9b Comparator

Claims (2)

[Claims] Claim 1: An operation plate through which vibrations propagate; a plurality of vibration sensors installed around the operation plate surface; An indicator that applies pulses, a timing determination unit that determines the timing of vibration detection by the plurality of vibration sensors, and a timing determination unit that compares and calculates the vibration detection timing of each of the vibration sensors determined by the determination unit to detect the vibration caused by the indicator. A coordinate input device comprising a calculation means for determining the coordinate value of an application point, wherein the timing determination means performs full-wave rectification of an alternating current detection signal output from the vibration sensor to convert it into a pulse wave. A coordinate input device characterized by including a rectifier circuit. 2. The timing determining means compares the levels of the detection signal full-wave rectified by the full-wave rectifier circuit with two different threshold values A and B, and determines the timing at which the small threshold value A is exceeded. and a timing at which a large threshold value B is exceeded; and means for invalidating the corresponding detection signal when the time is greater than a specified value. The coordinate input device according to claim 1.