JPH01124015A - Coordinate input device - Google Patents

Abstract

PURPOSE:To obtain highly accurate positional information by detecting the arrival delay time of a plate-like elastic wave only by the wave-form information of a part increasing its waveform out of received waveforms. CONSTITUTION:A Tg signal detecting circuit 22 outputs a signal 22' expressing a propagation delay time Tg detected by using the zero crossing point of a signal 21' obtained by differentiating an envelope, i.e. a group speed. A signal 26' obtained by inputting a signal passed through a delay time adjusting circuit 25 and a comparating level formed by a comparating level supplying circuit 24 to a comparator 26 is outputted as a detecting signal indicating a propagation delay time Tp based upon a phase speed. The propagation delay time values Tg, Tp detected by said procedure are determined by the waveform information obtained between a rise part of a waveform and the part of its maximum amplitude out of waveforms outputs by a sensor. Consequently, highly accurate positional information can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a coordinate input device that detects a coordinate position using the propagation delay time of an elastic wave, and particularly relates to a coordinate input device that improves detection accuracy. be.

[Prior Art] Conventionally, this type of coordinate input device presses a pen that generates vibration against a plate-shaped vibration transmission plate, uses a sensor to detect vibrations transmitted through the vibration transmission plate, and determines the pen's vibration from the transmission time of the vibration. There was something that calculated the pressing position.

Here, the signal obtained by the sensor has a certain time width, so in order to determine the arrival time of the vibration, the peak of the envelope was found and the time of the peak was taken as the arrival time of the vibration. .

[Problems to be Solved by the Invention] However, in order to effectively utilize the functions of the vibrator, the resonance frequency of the vibrator is used as the frequency of the mechanical vibration to be generated. The vibrations generated by the vibrator are transmitted to the propagation body via a conical member (horn). This conical member is designed to resonate at the above-mentioned resonance frequency, but due to problems such as how to fix the vibrator, how to support the horn, and the design of the input vent, it cannot necessarily be said that they match. It will shift to some extent. Therefore, the damped vibration when the drive of the vibrator is stopped becomes a damped vibration of the system of the horn and the vibrator, and is different from the frequency of the forced vibration when the vibrator is driven. Therefore, if the detection point for obtaining position information is set at the damped vibration part of the waveform output from the conversion element, the delay time and actual distance detected by the superposition of both waves described above will be linear ( The disadvantage was that it was not linear.

[Means for Solving the Problem 1] In order to solve this problem, the present invention includes means for determining the arrival time of the vibration in the portion where the amplitude of the signal detected by the sensor increases. Become. , [Examples] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows the received waveform detection circuit 9 used in this embodiment, and FIG. 2 is a waveform diagram showing the waveform and output timing of the output signal of the circuit. In FIG. 1, 6' indicates one of the plurality of sensors 6. 19 is this sensor 6'
A preamplifier circuit that amplifies the signal received by the receiver.

20 is an envelope detection circuit that detects the envelope (the overall shape of the wave formed by the received signal) 13 from the signal 14 amplified by the preamplifier circuit 19, and 21 is the inflection point of the envelope detected by the envelope detection circuit 2o. This is a differentiating circuit that differentiates the envelope twice to detect.

22 is a Tg signal detection circuit (for example, a zero-cross comparator) that outputs a signal 22' representing the point where the signal 21' obtained by differentiating the envelope crosses zero, that is, the propagation delay time Tg detected using the group velocity; A monostable multivibrator circuit which opens the gate for a certain period of time (creating a so-called window) from the rise of the signal 22' representing the propagation delay time Tg, 24 is a monostable multivibrator circuit 23 which opens the gate for a certain period of time after the rise of the signal 22'. This is a comparator level supply circuit that provides a comparator level for the comparator 26. 25 is envelope detection circuit 2
0, envelope peak detection circuit 21°Tg signal detection circuit 22. Monostable multiviralator23. This is a delay time adjustment circuit that adjusts the amount of time delayed through each circuit of the comparator level supply circuit 24. The signal passing through the delay time adjustment circuit 25 and the comparator level created by the comparator level supply circuit 24 are input to the comparator 26, and the resulting signal 26' is detected representing the propagation delay time Tp based on the phase velocity. Signal.

The propagation delay times Tg and Tp detected in this way are determined by the waveform information between the rising part and the part where the waveform amplitude is maximum in the waveform signal output by the sensor. More accurate location information can be obtained.

In other words, the waveform output by the sensor is divided into a rising part that obtains vibration energy by forcibly driving the vibrator in the vibrating pen, and a part obtained by the subsequent damped vibration, but the latter part is the former part. Compared to other parts, the frequency of vibration is not constant and fluctuates depending on the distance between the input source and the sensor. Therefore, if there is a point in the latter part for determining the delay time, the accuracy will be reduced accordingly.

A signal 22' representing these propagation delay times Tg and Tp
and 26', the arithmetic and control circuit 1 performs calculations to detect the coordinate position. An example of this coordinate position detection procedure and the configuration of a digitizer employing this method will be described in detail below.

FIG. 3 shows the structure of an information input/output device employing the present invention. The apparatus shown in FIG. 1 not only detects coordinates but also displays input information. That is, the illustrated information input device inputs coordinates to an input tablet made of a vibration transmission plate 8 using a vibrating ben 3, and displays coordinates on a display 11' made of a CRT placed over the input tablet according to the input coordinate information. It displays the input image.

In the figure, a vibration transmission plate 8 is made of acrylic, glass, or the like and transmits vibrations transmitted from the vibration ben 3 to three vibration sensors 6 provided at its corners. In this embodiment, the coordinates of the vibration ben 3 on the vibration transmission plate 8 are detected by measuring the transmission time of the ultrasonic vibration transmitted from the vibration ben 3 to the vibration sensor 6 via the vibration transmission plate 8.

The vibration transmitting plate 8 is supported by an anti-reflection material 7 made of silicone rubber or the like at its peripheral portion in order to prevent the vibration transmitted from the vibration vent 3 from being reflected from the peripheral portion and returning to the central portion. ing.

The vibration transmission plate 8 is arranged on a display device 11' capable of displaying dots, such as a CRT (or liquid crystal display), and is configured to display dots at positions deflected by the vibration ben 3.

That is, a dot is displayed at a position on the display 11' corresponding to the coordinates of the detected vibration vent 3, and
An image composed of elements such as points and lines inputted by the method appears after the trajectory of the vibrating ben, as if written on paper.

In addition, according to such a configuration, a menu is displayed on the display 11', and the menu item is selected by the vibrating bezel, or a prompt is displayed and the vibrating ben 3 is brought into contact with a predetermined position. You can also use

The vibration ben 3 transmits ultrasonic vibration to the vibration transmission plate 8.
It has a vibrator 4 made of a piezoelectric element or the like inside, and transmits ultrasonic vibrations generated by the vibrator 4 to a vibration transmission plate 8 via a horn portion 5.

The vibrator 4 of the vibrator 3 is driven by a vibrator drive circuit 2 at a predetermined frequency.

An electrical drive signal generated by the drive circuit 2 is converted into mechanical ultrasonic vibration by the vibrator 4, and transmitted to the diaphragm 8 via the horn portion 5 configured as described above.

The vibration frequency of the vibrator 4 is selected to a value that can generate plate waves on the vibration transmission plate 8 made of acrylic, glass, or the like. Further, when driving the vibrator, a vibration mode is selected that mainly vibrates the vibrator 4 or the vibrator 4 in the vertical direction in FIG. 2 with respect to the vibration transmission plate 8. Also, the vibration frequency of the vibrator 4 is set to
Efficient vibration conversion is possible by setting the resonant frequency to .

The elastic waves transmitted from the vibration vent 3 configured as described above to the vibration transmission plate 8 are plate waves, and are less susceptible to scratches on the surface of the vibration transmission plate 8, obstacles, etc. than surface waves. It has the advantage of

The vibration sensors 6 provided at the corners of the vibration transmission plate 8 are also constituted by mechanical to electrical conversion elements such as piezoelectric elements. The output signals of each of the three vibration sensors 6 are input to the waveform detection circuit 9, and are converted into detection signals that can be processed by the arithmetic control circuit 1 at the subsequent stage. The arithmetic and control circuit 1 performs a vibration transmission time measurement process and detects the coordinate position of the vibration bend 3 on the vibration transmission plate 8.

The detected coordinate information of the vibrating ben 3 is processed in the arithmetic control circuit 1 according to the output method by the display 11'.

That is, the arithmetic control circuit controls the output operation of the display 11' via the video signal processing device 10 based on the input coordinate information.

FIG. 4 shows the structure of the arithmetic control circuit l of FIG.

The microcomputer 11 includes an internal counter, ROM, and RAM. The microcomputer 11 gives a start signal to the drive signal generation circuit 12 to start driving the vibrator drive circuit 2, and also starts a counter 13 for measuring the vibration transmission time in synchronization with the start of vibration.

i] value of the counter 13 is latched into the latch circuit 14 by the microcomputer 11.

On the other hand, the waveform detection circuit 9 outputs timing information of a detection signal for measuring vibration transmission time for coordinate detection, as described above, from the output of the vibration sensor 6.

The timing signal input from the waveform detection circuit 9 is input to the input port 15, and the latch circuit 1 is input by the determination circuit 16.
4 and the result is transmitted to the microcomputer 11. That is, the vibration transmission time is expressed as the latch value of the output take of the counter 13, and coordinate calculations are performed based on this vibration transmission time value. Display 1
1' output control processing is performed via the input/output port 18.

The plate wave used in this embodiment is a dispersive wave, and therefore, with respect to the propagation distance within the vibration transmission plate 8,
The envelope and phase relationship of the detected waveform changes over the transmission distance during vibration transmission. Therefore, a method of detecting the distance between the vibration sensor 3 and the vibration sensor 6 using Tg and Tp (see FIGS. 1 and 2) obtained by the received waveform detection circuit will be described. Here, the speed at which the envelope advances is defined as group velocity Vg and phase velocity Vp. First, focusing only on the envelope, when a certain specific point, in this example, an inflection point in the rising part of the waveform (the second-order differential value is 0, see FIG. 2), is detected, the The distance d is the vibration transmission time Tg, and d = Vg - Tg (1) Furthermore, in order to determine more accurate coordinate values, processing is performed based on phase signal detection, and d = n. Enter p+■p11tp
...(2) Here, λp is the wavelength of the elastic wave, and n is an integer.

From the above equations (1) and (2), the above integer n is shown as n=[(Vg-Tg-Vp-tp)/λp+1/N] (3). Here, N is a real number other than 0, and an appropriate value is used. For example, if N=2, n can be determined if it is within ±1/2 wavelength. n obtained as described above can be determined.

By substituting n obtained as described above into equation (2), the distance between the vibration vent 3 and the vibration sensor 6 can be accurately measured.

As explained above, the distance obtained is for one sensor, but it can also be obtained for each other sensor by the same process, and the distance can be calculated by the calculation control circuit 1. is input.

When three vibration sensors 6 are arranged at the corners of the vibration transmission plate 8 at positions S1 to S3 as shown in FIG. The straight line distances d1 to d3 can be found.

Furthermore, the coordinates (X) of the position P of the vibrating ben 3 are determined based on the linear distances d1 to d3 of the arithmetic and control circuit l levers.

Y) can be obtained from the 3-square theorem as follows.

x=X/2+ (dl+d2)(di-d2)/2X
...(4) x=Y/2+ (dl+d3) (di-d3)/
2Y...(5) Here, X and Y are S2. This is the distance along the x and Y axes between the vibration sensor 6 at the position S3 and the sensor at the subtraction point (position S1).

In the manner described above, the position coordinates of the vibrating ben 3 can be detected in real time.

<Example 2> Depending on the product specifications, it may not be necessary to configure a highly accurate coordinate input device using Tg and "rp. In this case, as explained in the previous example, the Tg multiplied signal (The accuracy is lower than the Tg, Tp method).In this case, it is also possible to calculate the coordinates in the part where the waveform increases, rather than determining a specific detection point from the entire output waveform. If you set points, it will be more accurate than the former.

<Example 3> In the detection signal when the drive waveform is set as shown in 12 in Fig. 6,
A detection method for the portion corresponding to the pen drive vibration excitation portion will be described.

Reference numeral 14 in FIG. 6 indicates a signal detected by a sensor, and the envelope 13 is detected by an envelope detection circuit 20. Furthermore, the differential circuit 21 performs differentiation twice. At this time 1
A threshold of 101 is provided for the differential waveform 21' to obtain a waveform of 102. Using these 102 pulses as a window (strobe signal), the zero-crossing point of the twice differentiated waveform is detected. This results in a waveform of 103. Here, input the rising edge of pulse 103 to the flip-flop, and
2' waveform is obtained. The rising edge of this waveform is detected as tg, and then tp can be obtained using the first embodiment.

<Example 4> In Example 3, tg at the first excitation part of the detection signal
, tp can also be detected at the second excitation portion.

tg detection at the first vibration portion is detected at the falling edge of 22'. This tg causes a time delay with respect to the detection signal 14 due to envelope detection 2-concave differentiation or the like. Utilizing this time delay, tp can be detected at the second excitation portion. In other words, the delay time adjustment circuit 25 is not specially provided, and tg and tp can be detected using the circuit delay of the signal processing system and the two vibration parts.

[Effects of the Invention] As explained above, more accurate position information can be obtained by detecting the arrival delay time of the plate wave elastic wave using only the waveform information of the increasing part of the received waveform. It is designed so that it can be obtained.

[Brief explanation of the drawing]

FIG. 1 shows a received waveform detection circuit according to an embodiment. FIG. 2 is a waveform diagram showing the waveform and output timing of the output signal of the circuit of FIG. 1. FIG. 3 is an explanatory diagram of the device. FIG. 4 is a block diagram of the arithmetic control circuit. FIG. 5 is a diagram showing the arrangement of vibration sensors. FIG. 6 is a diagram showing signals of another embodiment. FIG. 7 is a block diagram showing the configuration of another embodiment. 1... Arithmetic control circuit 2... Vibrator drive circuit 3... Vibration pen 6... Vibration sensor 7... Anti-reflection material 8... Vibration transmission plate 9... Signal waveform detection circuit Explanation diagram of the moving device

Claims (1)

[Claims] 1) A vibrating pen that generates mechanical vibration is brought into contact with a signal input plate made of a vibration propagation medium, and an elastic wave propagated to the vibration propagation medium is placed at a predetermined position of the vibration propagation medium. Coordinate input for detecting the position coordinates of the vibrating pen by detecting the mechanical vibration with a conversion element provided therein and converting it into an electric signal, and measuring the propagation delay time of the elastic wave based on the detected electric signal. A coordinate input device, characterized in that the position coordinates of the vibrating pen are detected using waveform information of a portion of the waveform of the electric signal outputted from the conversion element, the amplitude of which increases sequentially. 2) In the device according to claim 1, the propagation delay time of the object to be counted is both a group propagation delay time related to the group velocity due to dispersion of the elastic wave and a phase propagation delay time related to the phase velocity. A coordinate input device characterized by detecting.