JPH02133816A - Coordinate input device - Google Patents

Abstract

PURPOSE:To drive a vibration pen only in a period needed for input of coordinates and to decrease the power consumption by detecting a down- movement of the pen via a pressure detecting means and, controlling the drive of the pen based on the detecting result of the pressure detecting means. CONSTITUTION:A pressure sensor 90 contained in a vibration pen consists of a piezoelectric element, etc. Then the surface of a vibration transmission plate 8 serving as a tablet surface is pointed by the vibration pen for execution of the input of coordinates. Thus the sensor 90 outputs an electric signal in accordance with the level of the pressure applied to the top of the vibration pen. When the electric signal exceeds a fixed level, a pen-down detecting circuit 19 outputs a detection signal to a control circuit. Then the control circuit produces a signal to a vibrator driving circuit 2 and starts the drive of the vibration pen. In such a way, the vibration pen is driven only in a period needed for input of coordinates. Thus the power consumption is decreased.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention detects vibrations input from a coordinate input device, particularly a vibrating pen, using a plurality of sensors provided on a vibration transmitting plate. The present invention relates to a coordinate input device that detects coordinates on the top.

[Prior Art] A device having a configuration as shown in FIG. 7 is conventionally known as a coordinate input device that detects the coordinates of a pointed point using elastic wave vibration. The coordinate input device shown in FIG. 7 inputs coordinates to an input tablet consisting of a vibration transmission plate 78 using a vibrating pen 73, and outputs the input coordinate information to an information processing device such as a personal computer to which this coordinate input device is connected. It is something to do.

The vibrating pen 73 is a pen for generating elastic waves in a vibration transmission plate 78 that transmits elastic waves, and includes a vibrator 74 and a horn 75.
, and its support. Also, reference numeral 72 indicates a drive circuit for this pen, reference numeral 76 indicates a piezoelectric element (vibration sensor) for detecting elastic waves transmitted through the vibration transmission plate 78, and reference numeral 77 indicates a drive circuit for the pen, and reference numeral 77 indicates a piezoelectric element (vibration sensor) for detecting elastic waves transmitted through the vibration transmission plate 78. It is an anti-vibration material to prevent reflections.

Now, since the elastic wave propagates through the vibration transmission plate 78 at a certain transmission speed V, the distance @d between the pointing point of the pen and the sensor is d=v-t (where t is the transmission time)...(1 ). (2) is a constant unique to the substance used as the propagation material, so to know d, it is sufficient to measure t.Vibration waveform detection circuits 83-85, latch circuits 86-88. The clock carantuff 9 is a circuit for measuring this transmission time t.

The control device 71 drives the vibrating pen 73 and simultaneously starts the time counter 79 from zero.

The vibration generated by the vibrating pen 73 reaches the vibration sensor 76 after a time corresponding to the distance, that is, a transmission time t. The vibration is converted into an electrical signal by the vibration sensor 76, and the signal is sent to vibration waveform detection circuits 83-85 via preamplifier circuits 80-83. When the vibration waveform detection circuit detects the transmission of vibration, it outputs a vibration detection signal to the latch circuits 86 to 88. The latch circuit reads the output of the vibration waveform detection circuit 79 using this vibration detection signal as a trigger.

The control device 71 calculates the distance between each sensor and the indicated point of the pen from the thus measured transmission time based on equation (1), and then performs geometric calculation to obtain coordinate values.

In addition, even if the maximum transmission time after the pen is driven, that is, the transmission time when the distance between the sensor and the indicated point is maximum within the effective area of coordinate input, the time determined from the circuit delay time, etc. If the vibration waveform is not detected, it means that the pen is up, so measurement of the transmission time is discontinued, and the above-described control after driving the vibration pen 73 is repeated.

By repeating the above operations, the indicated point coordinates are detected.

[Problems to be Solved by the Invention] In the conventional example described above, down-down of the pen is detected by using a sensor to detect vibrations generated when the vibrating pen is driven. That is, in order to detect pen down, it was necessary to constantly drive the vibrating pen 73, albeit intermittently.

In other words, the conventional device drives the pen only to detect pen down, which has the disadvantage of wasting power.

In addition, a coordinate input device has been devised that has a switch on the pen tip and detects when the pen is down by opening and closing the switch, but this has the drawback that the strokes when opening and closing the switch give an unpleasant writing feel. ing.

The object of the present invention is to solve the above problems.

[Means for Solving the Problems] In order to solve the above problems, in the present invention, vibrations input from a vibrating pen are detected by a plurality of sensors provided on a vibration transmission plate, and the vibrations of the vibrating pen are transmitted. In a coordinate input device that detects coordinates on a board, means is provided for detecting the pressure applied to the tip of the vibrating pen when the vibrating pen is pressed against the vibration transmission plate during coordinate input, and the output of this pressure detecting means is We adopted a configuration that controls the vibration generation of the vibrating pen depending on the situation.

[Function] According to the above configuration, it is possible to detect, via the pressure detection means, that the operator has lowered the vibrating pen onto the vibration transmission plate for inputting coordinates (pen down), and this detection result can be detected. The drive of the vibrating pen can be controlled accordingly.

[Example] Hereinafter, the present invention will be described in detail based on the example shown in the drawings.

FIG. 1 shows the configuration of a coordinate input device employing the present invention. In FIG. 0, reference numeral 8 indicates a vibration transmission plate that transmits vibrations as elastic waves, and reference numeral 6 indicates a piezoelectric element (hereinafter referred to as a sensor) that detects elastic waves. Reference numerals 9 to 11 are preamplifier circuits that amplify the signal from the vibration sensor 6, and reference numerals 12 to 14 are vibration waveform detection circuits that identify a certain point in the amplified signal and generate a detection signal that depends on the transmission time. Reference numerals 15 to 17 indicate latch circuits that use the detection signal as a trigger to latch the output of the time counter 18, that is, the transmission time information.

Reference numeral 4 is a piezoelectric element for generating vibration (hereinafter referred to as a vibrator),
Reference numeral 5 denotes a horn that amplifies vibration, and constitutes the vibrating pen 3 as a whole. Reference numeral 2 denotes a vibrator drive circuit that drives the vibrator 4.

The reference numeral 1 designates a control device that controls each circuit and calculates coordinate values, and the reference numeral 7 designates a vibration isolating material that prevents reflection at the end face of the vibration transmission plate 8.

Reference numeral 90 is a pressure sensor that converts the pressure applied to the pen tip into an electrical signal, and reference numeral 19 is a pen-down detection circuit that generates a pen-down detection signal based on the electrical signal output by the pressure sensor 90.

The coordinate input device in this embodiment uses the vibration transmitting plate 8 as an input tablet to input the coordinates of a designated point using the vibrator 3, and the input coordinate information is processed by a personal computer or the like to which this coordinate input device is connected. It is designed to output to the device.

FIG. 2 shows the structure of the vibrating pen 3. A vibrator 4 built into the vibrator 3 is driven by a vibrator drive circuit 2. The drive signal for the vibrator 4 is supplied as a low-level pulse signal from the arithmetic and control circuit 1 shown in FIG. is applied to

The electrical drive signal is transmitted by the vibrator 4 to the mechanical 8.

The pressure sensor 90 is disposed between a mounting member 90a having a U-shaped cross section and a structural member inside the pen shaft. The mounting member 90a couples the pressure sensor 9o and the horn 5 with the vibrator 4 housed inside the U-shape. Like the vibrator 4, the pressure sensor 9o is composed of a piezoelectric element or the like.

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 in which the vibrator 4 mainly vibrates 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 resonance frequency to .

The elastic waves transmitted to the vibration transmission plate 8 as described above are plate waves, which have the advantage that they are less susceptible to the effects of scratches, obstacles, etc. on the surface of the vibration transmission plate 8 compared to surface waves.

Next, the overall control that the control circuit 1 performs on each circuit and the operation of each circuit will be described using FIG.

The control circuit 1 first waits for a pen down detection signal and does not perform any control until the pen down detection circuit 19 outputs the detection signal. Then, when the user points to the surface of the vibration transmission plate 8, which is the tablet surface, with the vibrating ben 3 in order to input some coordinates, the pressure applied to the pen tip of the vibrating ben 3 causes the pressure sensor 90 to generate an electric current corresponding to this pressure level. Output a signal. When this electric signal exceeds a certain level, the pen down detection circuit 19 outputs a detection signal to the control circuit 1. When the control circuit 1 receives this detection signal, it first sends a clear signal to the time counter 18. After the time counter 18 clears the count value, it enters a state of waiting for input of a start signal.

Next, the control circuit 1 sends a start signal to the time counter 18, and at the same time generates a drive signal consisting of a pulse train that corresponds to the repetition period of the resonant frequency of the vibrator 4, and outputs it to the vibrator drive circuit 2. Further, the vibration waveform detection circuit 14 starts counting for a clock having a period corresponding to the required resolution. The signal output from the control circuit 1 is sent to the vibrator drive circuit 2.
and drives the pen's vibrator 4.

Now, the elastic waves generated by the pen's photography travel through the vibration transmission plate 8 and reach the vibration sensor 6, where they are converted into electrical signals and passed through preamplifier circuits 9 to 11 to the vibration waveform detection circuit. 12 to 14. Here, the vibration waveform is detected, and this detection signal is output to the latch circuits 15-17. In the latch circuit, this detection signal is used as a trigger to control the clock counter 1.
Take in the output of 8. The vibration waveform detection signal is sent to the control circuit 1.
It is also output for . The control circuit 1 takes in the data held in the latch circuit based on this detection signal.

In this way, the transmission time for each sensor is measured. The control circuit 1 calculates coordinate values by performing distance calculations and geometric calculations from the transmission time data for each sensor. The obtained coordinate values are transferred to the host information processing device.

Next, in order to obtain the coordinate values of the next input point that are input continuously, the control from the above-described time counter 18 clearing operation is repeated.

Now, if the signal waveform detection signal is not output even after the time determined by the maximum transmission time and circuit delay time after driving the pen, that is, outputting the start signal, the vibration pen 3 A state away from 8,
That is, since the pen is in the pen-up state, measurement of the transmission time is discontinued and the pen-down detection circuit 19 enters a standby state until it outputs a detection signal again. Note that an internal kakunta of the control circuit 1 is used to measure this time.

By performing the above control processing, the vibrating pen is not driven when the pen is up, but is driven only when the pen is down, and the indicated point coordinates can be detected in real time.

Next, details of waveform detection and coordinate calculation will be explained.

FIG. 3 explains the signal waveform from the vibration sensor 6 that is input to the waveform detection circuits 12 to 14 shown in FIG. 1 and the vibration transmission time measurement process based on the signal waveform. In FIG. 3, reference numeral 41 indicates a drive signal pulse applied to the vibrating pen 3. The ultrasonic vibration transmitted from the vibration pen 3 driven by such a waveform to the vibration transmission plate 8 passes through the vibration transmission plate 8 and takes a time tg corresponding to the distance to the vibration sensor 6, and then The vibration sensor 6 is reached. Reference numeral 42 in FIG. 3 indicates a signal waveform detected by the vibration sensor 6. The plate wave used in this embodiment is a dispersive wave, and therefore the relationship between the envelope 421 and phase 422 of the detected waveform changes depending on the vibration transmission distance.

Here, the speed at which the envelope advances is assumed to be group velocity Vg, and the phase velocity is assumed to be Vp. The distance between the vibration sensor 3 and the vibration sensor 6 can be detected from the difference in group velocity and phase velocity.

First, if we focus only on the envelope 421, its velocity is Vg, and when a point on a certain waveform, for example a peak, is detected as indicated by reference numeral 43 in FIG. 111d is d = V g −t g where the vibration transmission time is tg
- (1) Although this equation relates to one of the vibration sensors 6, the distances between the other two vibration sensors 6 and the vibration ben 3 can be expressed using the same equation.

Furthermore, in order to determine coordinate values with higher precision, processing based on phase signal detection is performed. Phase waveform 4 in Figure 4
If the time from 22 specific detection points, for example, vibration application to the zero cross point after passing the peak, is tp, then the distance between the vibration sensor and the vibration pen is d=n·λp+Vp−tp (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 n-[(
Vg-tg-Vp-tp)/λp+I/Nl...(3
). Here, N is a real number other than 0, and an appropriate value is used. For example, if N=2 and the fluctuation of the group delay time tg is within ±1/2 wavelength, n can be determined.

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

The two vibration transmission times tg and tp shown in FIG. 3 are measured by the waveform detection circuits 12 to 14 shown in FIG. The vibration waveform detection circuit can be configured as shown in FIG.

In FIG. 4, the output signal of the vibration sensor 6 is inputted via preamplifier circuits 9 to 11 to an envelope detection circuit 51 comprising an absolute value circuit, a low-pass filter, etc., and only the envelope of the detection signal is extracted. The timing of the extracted envelope peak is detected by an envelope peak detection circuit 53 composed of a differentiating circuit, etc., and an envelope delay time detection signal T8 is generated from this peak detection signal by a signal detection circuit 54 composed of a comparator etc. , the arithmetic control circuit 1, and the latch circuit 15.

Further, a Tp detection circuit 57 consisting of a comparator and the like is detected from the original signal delayed by the delay time adjustment circuit 52.
A phase delay time detection signal "rp" is formed and output to the arithmetic control circuit 1 and the latch circuit 15.The Tp detection circuit 57 detects the Tg multiplied signal by the multivibrator 55 and the comparator level supply circuit 56. It is adjusted to operate only for a certain period of time, making it possible to detect the zero cross point after the peak.

Here, if the number of sensors is generalized to h, then h detection signals are output for each of the envelope delay times Tgl to h and the phase transfer times Tp1 to h. As described above, since the time counter 18 is started in synchronization with the driving of the vibrating pen 3, the latch circuits 15 to 17 receive data indicating the transmission times of the envelope and the phase. Further, the control circuit 1 takes in the data held in the latch circuits 15 to 17 each time based on each detection signal. In this way, the envelope and phase transit time for each sensor are measured.

In order to detect coordinate values, if a sensor is provided on one side of the vibration transmission plate 8, the number of sensors is at least two,
Moreover, it is also possible to provide a larger number of them if necessary. For example, as shown in FIG. 5, three sensors Sl, S2, and S3 are arranged at the corners of the vibration transmission plate 8, and each sensor is detected from the position P of the vibration vent 3 by the process explained in connection with FIG. Straight paths 111dl to d3 to the sensor positions can be determined.

Furthermore, the control circuit 1 performs the following calculation based on the straight paths 1idl to d3, thereby controlling the vibration vent 3.
The locus i(x, y) of the input point P can be found.

x=X/2+ (ct1+d2)(d1-d
2) /2X...(4) y=y/2+ (dl+d3)(di-d3)/2Y
(5) Here, xlY is the distance along the X and Y axes between the vibration sensor 6 at the positions S2 and S3 and the sensor at the origin (position St).

According to this embodiment, when the pen of the vibrating ben 3 is brought down, the pen down is detected by the means for detecting the pressure applied to the pen tip of the vibrating ben 3, and the driving of the vibrating ben 3 is started, so that coordinate input is possible. Power consumption can be reduced by driving the vibrating vent 3 only for a necessary period.

Furthermore, pen-down detection is performed automatically without requiring any switch operation, so the operation is simple. Furthermore, pen-down is not detected by a mechanical switch or the like as in the past, and there is no switch stroke, so there is an advantage that the writing quality is not affected.

In the above example, an independent pressure sensor is used to detect pen down, but with the configuration shown in FIG. 6, the vibrator 4 of the vibrator 3 itself can be used as a pressure sensor. By configuring the vibrator 4 from a piezoelectric element, the pressure applied to the vibrator 4 can be detected through its output.

In FIG. 6, whether the vibrator 4 of the vibrator 3 is used as a vibrator or a pressure sensor is switched by an analog switch 21. During the coordinate detection period, the analog switch 21 connects the pen down detection circuit 20 to the vibrator 4, and during the coordinate input period based on the pen down detection, the vibrator drive circuit 2 is connected to the vibrating ben 3.

The pen-down detection circuit 20 may be configured to output a pen-down detection signal when the output signal of the vibrator 4 exceeds a certain level, and the other configurations are the same as in the previous embodiment.

According to such a configuration, since the vibrator 4 itself can be used as a pressure sensor, there is an excellent effect that the configuration is simpler and cheaper.

It goes without saying that the pressure sensor is not limited to a piezoelectric element, and various other elements such as a magnetostrictive sensor and a strain gauge can be used.

[Effects of the Invention] As is clear from the above, according to the present invention, the vibration input from the vibration pen is detected by a plurality of sensors provided on the vibration transmission plate, and the coordinates of the vibration pen on the vibration transmission plate are determined. In a coordinate input device that detects Since the configuration for controlling the generation of vibration is adopted, pen-down of the vibrating pen can be detected via the pressure detection means, and the driving of the vibrating pen can be controlled according to the detection result. Therefore, it is possible to provide an efficient coordinate input device with low power consumption through control such as driving the vibrating pen only during the period necessary for inputting coordinates.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the configuration of a coordinate input device adopting the present invention, Fig. 2 is an explanatory diagram showing the structure of the vibrating pen in Fig. 1, and Fig. 3 is an explanatory diagram showing a signal waveform for distance detection. 4 is a circuit diagram showing the configuration of the vibration waveform detection circuit, FIG. 5 is an explanatory diagram showing the arrangement of the vibration sensor, and FIG. 6 is an explanation showing an example of a different coordinate input device. 7 are explanatory diagrams showing the structure of a conventional coordinate input device. 1... Arithmetic control circuit 3... Vibration pen 4... Vibrator 6... Vibration sensor 8... Vibration transmission plate
9 to 11... Preamplifier circuit 12 to 14... Vibration waveform detection circuit 15 to 1 flap... Latch circuit 19.20... Pen down detection circuit 21... Analog switch 90... Pressure sensor Figure 2 Figure 3

Claims (1)

[Claims] 1) In a coordinate input device that detects the coordinates of the vibration pen on the vibration transmission plate by detecting the vibration input from the vibration pen using a plurality of sensors provided on the vibration transmission plate, the vibration pen transmits the vibration when inputting the coordinates. 1. A coordinate input device comprising means for detecting pressure applied to the tip of the vibrating pen when pressed against a plate, and controlling generation of vibration of the vibrating pen in accordance with the output of the pressure detecting means.