JPH0792725B2 - Coordinate input device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coordinate input device that detects a coordinate position by the propagation delay time of an elastic wave, and more particularly to a coordinate input device with improved detection accuracy. is there.

[Prior Art] Conventionally, in this type of coordinate input device, a pen that generates vibration is pressed against a plate-shaped vibration transmission plate, and the vibration transmitted through the vibration transmission plate is detected by a sensor. There was one that calculates the pressing position.

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

[Problems to be Solved by the Invention] However, as the frequency of mechanical vibration to be generated, the resonance frequency of the vibrator is used in order to effectively utilize the function of the vibrator. The vibration generated by the vibrator is transmitted to the propagating body via a conical member (horn). This conical member is designed to resonate at the resonance frequency, but due to problems such as the method of fixing the vibrator and the method of supporting the horn, and the design as an input pen, it cannot be said that they are always the same. It will be slightly displaced. Therefore, the damping vibration when the driving of the vibrator is stopped becomes the damping vibration of the system of the horn and the vibrator, which is different from the frequency of the forced vibration when the vibrator is driven. Therefore, if the detection point for obtaining the position information is set in the damped oscillation part of the waveform output from the conversion element, the delay time detected by the superposition of both waves and the actual distance are linear ( It had the drawback of not being linear).

[Means for Solving the Problems] In order to solve the above problems, the present invention detects a plate wave input from a vibration input pen by a vibration detecting means provided in a plurality of vibration transmitting members to transmit the vibration. In the coordinate input device for deriving the coordinates of the vibration input pen on the vibration transmitting member from the group velocity and the phase velocity of the plate wave in the member and the transmission delay time of the plate wave relating to each velocity, the detection is performed by the vibration detecting means. Deriving means for detecting two pieces of time information relating to each of the group velocity and the phase velocity of the generated plate wave from the amplitude increasing portion of the signal waveform and deriving the contact coordinate position of the vibration input means with respect to the vibration transmitting member. It is characterized by having.

Embodiments Embodiments of the present invention will be described in detail below 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 of the output signal of the circuit and the output timing. 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, a reference numeral 20 is an envelope detection circuit that detects an envelope (the shape of the entire wave formed by the received signal) 13 from the signal 14 amplified by the preamplifier circuit 19, and a reference numeral 21 is an envelope. 2 envelopes for detecting the inflection point of the envelope detected by the detection circuit 20.
It is a differentiating circuit that differentiates differently. 22 is a point where the signal 21 ″ obtained by differentiating the envelope becomes zero cross, that is, a Tg signal detection circuit (for example, a zero cross comparator) that outputs a signal 22 ′ representing the propagation delay time Tg detected by using the group velocity, and 23 is A monostable multivibrator circuit that opens the gate (makes a so-called window) for a certain time from the rise of the signal 22 'representing the propagation delay time Tg, and 24 is a comparator when the gate made by the monostable multivibrator 23 is open. A comparator level supply circuit for providing a comparator level of 26. An envelope detection circuit 25.
20, envelope peak detection circuit 21, Tg signal detection circuit 22,
This is a delay time adjustment circuit that adjusts a time delay that has passed through each circuit of the monostable multivibrator 23 and the comparator level supply circuit 24. A signal obtained by inputting the signal that has passed through the delay time adjustment circuit 25 and the comparator level created by the comparator level supply circuit 24 to the comparator 26.
Let 26 'be the detection signal representing the propagation delay time Tp based on the phase velocity.

Since the propagation delay times Tg and Tp detected in this way are determined by the waveform information between the rising portion and the portion where the amplitude of the waveform is maximum in the waveform signal output by the sensor, Highly accurate position information can be obtained. In other words, the waveform output by the sensor is divided into a rising part that forcibly drives the vibrator in the vibrating pen to obtain vibration energy and a part that is obtained by the subsequent damping vibration, but the latter part is the former part. Compared to the part, the frequency of vibration is not constant and there is fluctuation due to the distance between the input source and the sensor. Therefore, if there is a point that determines the delay time in the latter part, the accuracy will be reduced accordingly.

Signals 22 'and 2 representing these propagation delay times Tg, Tp
The calculation control circuit 1 calculates using both 6'to detect the coordinate position. An example of this coordinate position detection procedure and the configuration of the digitizer employing this method will be described in detail below.

FIG. 3 shows the structure of an information input / output device adopting the present invention. The device of FIG. 1 not only detects coordinates but also displays input information. That is, the illustrated information input device causes the input tablet made of the vibration transmission plate 8 to input coordinates by the vibration pen 3, and the display 11 'composed of the CRT arranged on the input tablet according to the inputted coordinate information. The input image is displayed.

In the figure, reference numeral 8 is a vibration transmission plate made of acrylic, glass plate or the like, and transmits the signal transmitted from the vibration pen 3 to the vibration sensor 6 provided at three corners thereof. In this embodiment, the coordinate of the vibration pen 3 on the vibration transmission plate 8 is detected by measuring the transmission time of the ultrasonic vibration transmitted from the vibration pen 3 to the vibration sensor 6 via the vibration transmission plate 8.

The vibration transmitting plate 8 has its peripheral portion supported by an antireflection material 7 made of silicon rubber or the like in order to prevent the vibration transmitted from the vibrating pen 3 from being reflected at the peripheral portion and returning toward the central portion. ing.

The vibration transmission plate 8 is a CRT (or a liquid crystal display, etc.),
It is arranged on a display device 11 'capable of displaying dots and is adapted to display dots at a position traced by the vibrating pen 3. That is, a dot display is performed at a position on the display 11 'corresponding to the detected coordinates of the vibrating pen 3.
An image composed of elements such as points and lines input by the vibrating pen 3 appears after the locus of the vibrating pen as if writing was performed on paper.

In addition, according to such a configuration, a menu display is provided on the display 11 ', and the menu item is selected by the vibrating pen, or a prompt is displayed to bring the vibrating pen 3 into contact with a predetermined position. Can also be used.

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

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

The electric 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 unit 5 configured as described above.

The vibration frequency of the vibrator 4 is selected at a place where a plate wave can be generated on the vibration transmission plate 8 such as acrylic or glass. Further, when driving the vibrator, the second
A vibration mode in which the vibrator 4 mainly vibrates in the vertical direction in the figure is selected. Further, by setting the vibration frequency of the vibrator 4 as the resonance frequency of the vibrator 4, it is possible to perform efficient vibration conversion.

The elastic wave transmitted from the vibrating pen 3 configured as described above to the vibration transmission plate 8 is a plate wave, and is less affected by scratches or obstacles on the surface of the vibration transmission plate 8 than surface waves. Has the advantage.

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

The detected coordinate information of the vibrating pen 3 is processed in the arithmetic and control circuit 1 according to the output system 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 1 of FIG.

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

The count value of the counter 13 is latched by the microcomputer 11 in the latch circuit 14.

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

The timing signal input from the waveform detection circuit 9 is input to the input port 15 and compared with the count value in the latch circuit 14 by the determination circuit 16 and the result is obtained by the microcomputer 11
Be transmitted to. That is, the vibration transmission time is expressed as a latch value of the output data of the counter 13, and the coordinate calculation is performed based on this vibration transmission time value. The output control process of the display 11 'is performed via the input / output port 18.

The relationship between the envelope of the detected waveform and the phase with respect to the propagation distance in the transmission plate 8 used in this embodiment is as follows.
It changes according to the transmission distance during vibration transmission. Therefore, a method for detecting the distance between the vibration pen 3 and the vibration sensor 6 using Tg and Tp (see FIGS. 1 and 2) obtained by the reception waveform detection circuit will be described. Here, the velocity at which the envelope advances is referred to as group velocity Vg, and the phase velocity is referred to as Vp. First, focusing only on the envelope, an inflection point at a certain specific point, that is, the rising portion of the waveform in this embodiment (the second differential value is 0, see FIG. 2).
Is detected, the distance d between the vibration pen 3 and the vibration sensor 6 is the vibration transmission time as Tg. D = Vg · Tg (1) Further, in order to determine the coordinate value with higher accuracy, A process based on the detection is performed, and d = n · λp + Vp · tp (2) where λp is the wavelength n of the elastic wave and is an integer.

From the expressions (1) and (2), the integer n is expressed 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 within ± 1/2 wavelength.

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

As described above, the obtained distance is for one sensor, but it can be obtained for each of the other sensors by the same process and is input to the arithmetic control circuit 1. To be done.

As shown in FIG. 5, when the three vibration sensors 6 are arranged at the corners of the vibration transmission plate 8 at the positions of S1 to S3, the vibration sensors 6 are moved from the position P of the vibrating pen 3 by the processing described above.
The linear distances d1 to d3 to the position can be obtained. Further, the arithmetic control circuit 1 can obtain the coordinates (X, Y) of the position P of the vibrating pen 3 based on the linear distances d1 to d3 from the Pythagorean theorem as follows.

x = X / 2 + (d1 + d2) (d1-d2) / 2X (4) x = Y / 2 + (d1 + d3) (d1-d3) / 2Y (5) where X and Y are the positions of S2 and S3. Vibration sensor 6 and deduction (position S
It is the distance along the X and Y axes of the sensor in 1).

As described above, the position coordinates of the vibrating pen 3 can be detected in real time.

<Example 2> Depending on the product spec, it may not be necessary to configure a highly accurate coordinate input device using Tg and Tp. In this case, as described in the previous embodiment, the coordinates may be calculated using only the Tg signal (the accuracy is lower than that of the Tg, Tp method). Also in this case, the accuracy is higher in the case where the detection points are provided in the part where the waveform increases as compared with the case where the specific detection points are determined from the entire output waveform.

<Embodiment 3> A method of detecting a portion corresponding to the pen drive vibrating portion in the detection signal when the drive waveform is as shown in FIG. 12 will be described.

Reference numeral 14 in FIG. 6 denotes a signal detected by the sensor, and the envelope 13 is detected by the envelope detection circuit 20. Further, the differentiating circuit 21 performs second differentiation. At this time, a threshold of 101 is provided for the once differentiated waveform 21 'to obtain a waveform of 102. This 102 pulse is used as a window (strobe signal) to detect the zero-cross point of the second-order differential waveform. This is
There are 103 waveforms. Here, the rising edge of the pulse 103 is input to the flip-flop to obtain a waveform 22 '. The rising edge of this waveform is detected as tg, and thereafter, according to the first embodiment,
You can ask for tp.

<Fourth Embodiment> In the third embodiment, tg at the first excitation portion of the detection signal,
It is also possible to detect tp in the second vibration part.

The tg detection at the first vibration part is detected at the trailing edge of 22 '. This tg causes a time delay with respect to the detection signal 14 due to envelope detection second-order differentiation or the like. By using this time delay, tp can be detected in the second vibration part. That is, the delay time adjusting circuit 25 is not specially provided, and tg and tp can be detected by utilizing the circuit delay of the signal processing system and the two exciting portions.

[Effects of the Invention] As described above, by detecting the arrival delay time of the elastic wave in the plate wave only with the waveform information of the part where the amplitude increases in the received waveform, the position information with higher accuracy can be obtained. Is to be able to obtain.

[Brief description of drawings]

FIG. 1 is a received waveform detection circuit of the embodiment. FIG. 2 is a waveform diagram showing waveforms and output timings of output signals of the circuit of FIG. FIG. 3 is an explanatory view of the device. FIG. 4 is a block diagram of the arithmetic control circuit. FIG. 5 is a vibration sensor layout. 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 ... Oscillator drive circuit 3 ... Vibration pen 6 ... Vibration sensor 7 ... Antireflection material 8 ... Vibration transmission plate 9 ... Signal waveform detection circuit

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kiyoshi Kaneko 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Noriyuki Suzuki Noriyuki Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Jun Tanaka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Shigeki Mori 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. ( 56) References JP-A-61-33523 (JP, A) JP-B 5-86568 (JP, B2)

Claims (2)

[Claims] 1. A plate wave input from a vibration input pen is detected by a plurality of vibration detecting means provided in a vibration transmitting member,
In the coordinate input device for deriving the coordinates of the vibration input pin on the vibration transmitting member from the group velocity and the phase velocity of the plate wave in the vibration transmitting member and the transmission delay time of the plate wave related to each velocity, the vibration detection Two pieces of time information relating to each of the group velocity and the phase velocity of the plate wave detected by the means are detected from the amplitude increasing portion of the signal waveform, and the contact coordinate position of the vibration input means with respect to the vibration transmitting member is derived. A coordinate input device comprising: derivation means. 2. The vibration input pen is driven by a modulation drive signal composed of a plurality of pulse signal trains, and the derivation means is a transmission delay related to group velocity at a first amplitude increasing portion of a detection signal waveform of the vibration detection means. One of the transmission delay times relating to time or the phase velocity is detected, the other transmission delay time is detected in the second amplitude increasing portion, and the contact position coordinates are derived based on them. The coordinate input device according to the first section.