JPH02109116A - Coordinate input device - Google Patents

Abstract

PURPOSE:To always perform the accurate detection of coordinates regardless of an input level by controlling the gain of an amplifying means in response to the output level of the amplifying means and at the same time invalidating the input coordinates in a gain control period. CONSTITUTION:When a vibration pen 3 touches a vibration transmitting plate 8, the ultrasonic vibrations are transmitted to the plate 8 and detected by three vibration sensors 6. Each output signal of the sensors 6 is inputted to a waveform detecting circuit 9 via a voltage control amplifier 112 and a level detecting circuit 113. Then the arriving timing of vibrations to each sensor 6 is detected through a waveform detecting process. This detecting signal is inputted to an arithmetic control circuit 1. The circuit 112 receives the gain control by the circuit 113. The prescribed AGC control is given to the waveform process and the coordinate arithmetic process which are carried out by the circuits 9 and 1. In the AGC control, the pen 3 touches the plate 8 for input of the coordinates and the coordinate value obtained by the first one of the vibration detecting signals which are intermittently inputted via the pen 3 is neglected.

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 vibration sensors provided on a vibration transmitting plate, and transmits the vibrations of the vibrating pen. This invention relates to a coordinate input device that detects coordinates on a board.

[Prior Art] Coordinate input devices using various input pens, tablets, etc. have been known as devices for inputting handwritten characters, figures, etc. to a processing device such as a computer. In this type of system, input image information consisting of characters, graphics, etc. is output to a display device such as a CRT display or a recording device such as a printer.

In particular, as a method for inputting coordinates by placing an input tablet on a display or a document, a method using ultrasonic vibration in which the tablet is made of a transparent material such as glass or plastic is known.

This type of device uses a device such as a piezoelectric element to convert elastic wave vibrations transmitted through a vibration transmission plate. /M is detected by a conversion element, and after amplifying the output of this conversion element with a predetermined gain, a predetermined waveform is detected to determine the vibration transmission timing, and coordinate values are calculated from the vibration transmission time.

[Problem to be solved by the invention] Conventionally, the output signal of a vibration sensor is amplified with a constant gain, so if the dynamic range of the detection signal is wide, the dynamic range of the amplification circuit is insufficient, and weak It may become impossible to amplify the input signal with sufficient gain. For example, when the coordinate input point is far from the vibration sensor, there is a problem that coordinate detection becomes unstable and accuracy decreases.

Conventionally, AGC control has been considered in which the gain of the amplifier circuit is automatically adjusted according to the detection signal level of the vibration sensor. It is necessary to determine the gain required until the delay time for coordinate calculation is measured. Therefore, with the conventional device, it was not possible to obtain a sufficient AGC control response, and the above problem could not be solved.

vJ of the present invention! The object of the present invention is to provide a coordinate input device that solves the above problems and allows accurate coordinate input even in the limited dynamic range of an amplification system, regardless of the signal level caused by the distance of the coordinate input point. .

[Means for Solving the Problems] In order to solve the above-mentioned problems, in the present invention, vibrations input from a vibrating vent are detected by a plurality of vibration sensors provided on a vibration transmission plate, and vibrations of the vibrating vent are detected. "Transmission board"
2. A coordinate input device for detecting coordinates at 2, which includes means for amplifying the output of the vibration sensor with a variable gain, and a gain for controlling the gain of the amplification means via a predetermined time constant according to the output level of the amplification means. a control means, and a period of time until the output of the amplification means is taken in, the vibration transmission time on the vibration transmission plate is calculated, the coordinates of the input point are detected based on this, and the gain control via the time constant is stabilized; A configuration is adopted in which a control means is provided to invalidate the initial value of the coordinates detected based on the output of the amplification means.

[Function] According to the above configuration, the gain of the amplifying means for amplifying the output of the vibration sensor can be controlled according to the output level, so that appropriate gain control can be performed according to the input level of the vibration sensor, and By invalidating the input coordinates during the gain control period, coordinate detection can be performed based only on accurate vibration transmission time.

[Example] Hereinafter, based on the example shown in the drawings, the present invention will be described in detail.The apparatus inputs coordinates to an input tablet consisting of a vibration transmission plate 8 using a vibrating ben 3, and places the coordinates on the input tablet according to the input coordinate information. The input image is displayed on a display device 11' consisting of a CRT or LCD. The vibration transmission plate 8 is made of acrylic, glass plate, etc.
The vibrations transmitted from the vibrating ben 3 are transmitted to three vibration sensors 6 provided at the corners thereof. 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 coordinates of the vibration ben 3 on the vibration transmission plate 8 can be detected.

The vibration transmitting plate 8 has its peripheral portion supported by an anti-reflection material 7 made of silicone rubber or the like in order to prevent the vibrations transmitted from the vibration vent 3 from being reflected at the peripheral portion and returning toward 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 displays dots at the position traced by the vibrating ben 3. That is, A dot is displayed at the position of the display 11'J2 corresponding to the detected coordinates of the vibrating ben 3, and the image composed of elements such as points and lines inputted by the vibrating ben 3 is as if written on paper. Appears after the trajectory of the vibrating ben as done.

In addition, according to such a configuration, a menu is displayed on the display 11', and a menu item is selected using the vibrating bezel, a prompt is displayed, and inputs such as touching the vibrating ben 3 at a predetermined position are performed. A method can also be used.

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 having a sharp tip.

FIG. 2 shows the structure of the vibrating vent 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 converted into mechanical ultrasonic vibration by the vibrator 4 and transmitted to the diaphragm 8 via the horn section 5.

The vibration frequency of the vibrator 4 is selected to a value that does not cause plate waves to be generated in 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.

Again, in FIG. 1(A), the vibration sensor 6 provided at the corner of the vibration transmission plate 8 is also constituted by a mechanical to electrical conversion element such as a piezoelectric element. The output signals of each of the three vibration sensors 6 are input to the waveform detection circuit 9 via the VCA circuit 112 and the level detection circuit 113, and the timing of vibration arrival at each sensor is detected by waveform detection processing to be described later.

This detection timing signal is input to the arithmetic control circuit 1. The VCA circuit 112 receives gain control by the level detection circuit +13.

1(B) and 1(C), FIG. 1(A)(7) VCA circuit (voltage control amplifier) 112 and level detection circuit 113.
The configuration is shown below. What is shown in Figure 1 (B) is Figure 1 (A)
In the circuit for one sensor, the input signal of the vibration sensor 6 is input to the input terminal of the operational amplifier 202 via the resistor 201 (resistance value R1). The voltage fed back to one output terminal of the operational amplifier 202 is fed back to the resistor 203 (resistance value R
2) and FET 204. FET2
04 connects the level detection circuit 11 of FIG. 1(C) to the terminal 205.
The conduction ratio is changed according to the voltage signal input from 3,
This determines the amplification factor of the operational amplifier 202.

The amplification factor a is expressed as a=(++R/Rv). Here R
In FIG. 1(B), resistance values R and Rv when R1=R2=R are source-drain resistances of the FET 204 that vary depending on a voltage Vc determined by a level detection circuit 113, which will be described later.

The level detection circuit 113 is composed of a charging/discharging circuit including a resistor, a capacitor, and a diode, as shown in FIG. 1(C). That is, the signal line from the VCA circuit 112 to the signal waveform detection circuit 9 has a resistance 301 (resistance value R
3) It is connected via the anode cathode of the diode 302 to a capacitor 304 whose one end is grounded.

On the other hand, the connection point between the diode 302 and the capacitor 304 is the anode cathode of the diode 303 and the resistor 30.
5 (resistance value R4) to the terminal 205 of the VCA circuit 112 (7) in FIG. 1(B). That is, the capacitor 304 is charged via the resistor R3 and the diode D1 with a time constant determined by the resistor 301 and the capacitance C of the capacitor 304.

In addition, the capacitor 304 transfers its charging voltage to the diode 3.
02, VCA circuit 1 via resistor 305 (resistance value R4)
Output to 12. The time constant at this time is determined by the resistance value R4 of the resistor 305 and the capacitance C of the capacitor 304.

Here, the time constant due to resistors R4 and C is set larger than the time constant due to resistors R3 and C, and therefore, as shown in FIG.
When an input waveform like D) is input to the operational amplifier 202, the voltage v at the connection point 306 of the capacitor and diode
B changes as shown in Fig. 1 (E), while the voltage VC at the terminal 205 changes as shown in Fig. 1 (F
).

Therefore, each time a vibration waveform is input from the vibration sensor 6, a voltage corresponding to the amplitude of the input waveform is generated in the capacitor 304, but this voltage is applied to the VCA circuit 1 with a large time constant.
12, and automatic gain control with a slow rate of change is performed. As described above, the signal input to the signal waveform detection circuit 9 is controlled to have a substantially constant amplitude even if the amplitude of the input waveform changes.

The waveform processing after the signal waveform detection circuit 9 and the coordinate calculation processing will be described in detail later, but here we will explain the above-mentioned 48
The effects of the code processing system will be explained. The biggest difference between the above signal processing system and the conventional technology is that in the past, the main focus was on making the ACG response as quick as possible, but in the above embodiment, the AGC control is activated with a predetermined time constant. It is. This kind of AGC
The purpose of this control is to ignore the vibration detection waveform input for the first time when the vibration pen 3 is not in contact with the vibration transmission plate 8 in the control described later.6 In this embodiment, the vibration pen 3 A state in which it is not in contact with the transmission plate 8,
In other words, from the pen-up state, the vibration ben 3 moves to the vibration transmission plate 8.
The coordinate values obtained by the first vibration detection signal that is intermittently inputted from the vibrating pen 3 after the vibrating pen 3 enters the pen-down state in which coordinates are input are ignored. it is,
This is because the coordinates of this point cannot be detected with sufficient accuracy because the amplification factor determined by the VCA circuit 112 is not stable.

Conversely, if a relatively large time constant is set for the feedback control of the VCA circuit 112 as described above, the VCA circuit 112
If the period until the circuit 112 is able to perform stable amplification factor control is made to correspond to the vibration input interval of the vibrator 3, it will be possible to control the amplification factor based on the first or several vibration inputs when the pen-up state shifts to the pen-down state. By ignoring the coordinate values, accurate coordinate values can be reliably detected even when the input signal from the vibration sensor is small, for example, when the coordinate input is performed at a point far from the vibration sensor.

Vibration input is performed intermittently from the vibration vent 3, and coordinate calculation is performed for each vibration input, but by setting this detection cycle sufficiently fast compared to the operating speed of the vibration vent 3, the above-mentioned result can be achieved. Even if the input coordinates are ignored immediately after pen-down, accurate images, figures, etc. can be input. Note that the period or number of times the coordinate values are ignored immediately after pen-down may be determined according to the feedback time constant of the VCA circuit 112.

Next, the coordinate detection processing after the signal waveform detection circuit 9 will be explained.

The arithmetic control circuit 1 detects the vibration transmission time to each sensor based on the detection timing input from the waveform detection circuit, and further detects the coordinate input position of the vibration ben 3 on the vibration transmission plate 8 from this vibration transmission time.

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. 3 shows the structure of the arithmetic control circuit shown in FIG. 1.

Here, the structure of the drive system of the vibrating ben 3 and the vibration detection system using the vibration sensor 6 are mainly shown.

The microcomputer 11 includes an internal counter, ROM, and RAM. The drive signal generation circuit 12
It outputs a drive pulse of a predetermined frequency to the vibrator drive circuit 2 shown in the figure, and is activated by the microcomputer 11 in synchronization with the coordinate calculation circuit.

The count 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 number 43 for measuring vibration transmission time from the output of the vibration sensor 6 as described later. These timing information are input to the input ports 15, respectively.

The timing signal input from the waveform detection circuit 9 is input to the input port 15 and stored in the storage area corresponding to each vibration sensor 6 in the latch circuit 14, and the result is transmitted to the microcomputer 11.

That is, the vibration transmission time is expressed as the latch value of the output data of the counter 13, and the coordinate calculation is performed using this vibration transmission time value. At this time, the determination circuit 16 makes a complete determination as to whether or not all waveform detection timing information from the plurality of vibration sensors 6 has been input, and the microcomputer 1
Notify 1.

Output control processing for the display device 11' is performed via the input/output port 17.

FIG. 4 explains the detected waveform input to the waveform detection circuit 9 of FIG. 1 and the vibration transmission time measurement process based on the detected waveform. What is indicated by reference numeral 41 in FIG. 4 is a drive signal pulse applied to the vibrating vent 3. Ultrasonic vibrations transmitted from the vibration ben 3 driven by such a waveform to the vibration transmission plate 8 pass through the vibration transmission plate 8 and are detected by the vibration sensor 6.

After traveling within the vibration transmission plate 8 for a time tg corresponding to the distance to the vibration sensor 6, the vibration reaches the vibration sensor 6. Reference numeral 42 in FIG. 4 indicates a signal waveform detected by the vibration sensor 6. The plate wave used in this embodiment is a dispersive wave, so the envelope 42 of the detected waveform
The relationship between 1 and phase 422 changes depending on the vibration transmission distance.

Here, the speed at which the envelope advances is defined as group velocity Vg and phase velocity 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. @Jld is d=Vg -tg 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
22 specific detection points, for example, if the time from vibration application to the zero cross point after passing the peak is tp, then the distance between the vibration sensor and the vibration vent is d=n ・λp+Vp −tp
... (2) becomes. Here, λp is the wavelength of the elastic wave, n
is an integer.

From the above equations (1) and (2), the above integer n is n-[(Vg-tg -Vp Hjp)/λp,
It is expressed as l/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 (2), the distance between the vibration vent 3 and the vibration sensor 6 can be accurately measured.

In order to measure the two vibration transmission times tg and tp shown in FIG. 3, the waveform detection circuit 9 can be configured as shown in FIG. 5, for example.

The amplified signal is input to the envelope detection circuit 52, and only the envelope of the detection signal is extracted. The timing of the peak of the extracted envelope is detected by the envelope peak detection circuit 53. From the peak detection signal, an envelope delay time detection signal Tg having a predetermined waveform is formed by a signal detection circuit 54 composed of a mono-multivibrator or the like, and is input to the arithmetic control circuit 1.

Further, a phase delay time detection signal Tp is formed by the detection circuit 58 from this Tg times signal timing and the original signal delayed by the delay time adjustment circuit 57, and the arithmetic control circuit 1
is input.

That is, the Tg multiplied signal is converted into a pulse of a predetermined width by the monostable multivibrator 55. Further, the comparator level supply circuit 56 outputs tp according to this pulse timing.
Form a threshold for detecting flaw signals. As a result,
A comparator level supply circuit 56 forms a signal 44 having a level and timing as indicated by reference numeral 44 in FIG.
The signal is input to the detection circuit 58.

That is, the monostable multivibrator 55 and the comparator level supply circuit 56 are used to ensure that the phase delay time measurement is activated only for a certain period of time after the envelope peak is detected.

This signal is sent to a detection circuit 5 consisting of a comparator etc.
8 and is delayed and compared with the detected waveform as shown in FIG. 4, and as a result, a tp detection pulse 45 is formed.

The circuit shown above is for one vibration sensor 6, and the same circuit is provided for each of the other sensors.

If the number of sensors is generalized to h, then h detection signals each having envelope delay times Tgl to h and phase delay times Tpl to h are input to the arithmetic control circuit 1.

In the arithmetic control circuit shown in FIG.
The h signal is input from the input port 15, and the count value of the counter I3 is taken into the latch circuit 14 using each timing as a trigger. Since the counter 13 is started in synchronization with the driving of the vibrating pen as described above, the latch circuit 14 receives data indicating the respective delay times of the envelope and the samurai phase.

When three vibration sensors 6 are arranged at the corners of the vibration transmission plate 8 at positions S to S3 as shown in FIG. Straight line distance 11dl to d3 of vibration sensor 6 to position jη
can be found.

Furthermore, the arithmetic control circuit 1 calculates the straight line distance l1lllld1~d.
3, the coordinates (x, y) of the position P of the vibrating pen 3 can be determined from the 3-square theorem as shown in the following equation.

x-X/2 + (dl + d2) (di-d
2)/2X −(4)y−y/2+ (di
+ d3) (di - d3)/2Y ・
(5) Here, X and Y are the distances along the X and Y axes between the vibration sensor 6 at the positions S2 and S3 and the sensor at the origin (position Sl).

As described above, the position coordinates of the vibrating pen 3 can be detected in real time. Note that the detected coordinates obtained by the above calculation are ignored immediately after the pen is down, as described above.

Although the example in which gain control is performed using an analog circuit has been described above, digital gain control may be performed using a configuration as shown in FIG.

In FIG. 7, the feedback circuit of the operational amplifier 202 to which the output of the vibration sensor 6 is input includes a resistor 203 and a resistor 10.
04 and a switch 1005. resistance 1004
are the resistance values R3 and R4, each with one end connected in parallel.
..., and the other end of these resistors is the switch 1005
connected to one end of independently controlled contacts. The other end of each element of switch 1005 is grounded. Therefore,
By weighting each resistance value of the resistor 1004 and selecting an appropriate resistance value via the switch 1005, the amplification factor of the operational amplifier 202 can be controlled as desired.

In this case, the level detection circuit 113 is an A/D converter as shown in the figure.
converter 1006 and microcomputer 100
It can be configured from 7. In other words, A/D converter 1006
The output of the operational amplifier 202 is converted into a digital value and input to the microcomputer 1007. The microcomputer 1007 stores data having the largest value among the input digital signals in a predetermined memory, and increases the gain of the operational amplifier 202 if the newly input value is smaller than this maximum value. The switch 1005 is controlled to. Gain control similar to that described above is also possible with such a digital circuit.

The configuration shown in FIG. 7 has the advantage 7-k that the degree of freedom in the control range is increased by selecting each resistance value of the resistor 1004 without being influenced by the characteristics of the analog circuit.

[Effects of the Invention] As is clear from the above, according to the present invention, vibrations input from a vibrating pen are detected by a plurality of vibration sensors arranged on a vibration transmitting plate, and the vibrations inputted from a vibrating pen are detected by a plurality of vibration sensors arranged on a vibration transmitting plate of the vibrating pen. In the coordinate input device for detecting the coordinates at
gain control means for controlling the gain of the amplification means via a predetermined time constant in accordance with the output level of the stage; and a gain control means for taking the output of the amplification means and calculating the vibration transmission time at the vibration transmission plate Detects the input point IIJfi based on the input point, and invalidates the initial value of the coordinate detected based on the output of the amplification means for a period until the gain control via the time constant is stabilized. Since the configuration is equipped with a control means, the gain of the amplification means that amplifies the output of the vibration sensor can be controlled according to the output level, so appropriate gain control can be performed according to the input level of the vibration sensor. By invalidating the input coordinates during the gain control period, only the accurate vibration transmission time can be detected. Therefore, there is an excellent advantage that accurate coordinate detection can be performed at all times regardless of the magnitude of the input level due to the distance or proximity of the vibration input point.

[Brief explanation of drawings]

FIG. 1(A) is an explanatory diagram showing the configuration of a coordinate input device adopting the present invention, FIG. 1(B) is a circuit diagram showing the configuration of the VCA circuit of FIG. 1(A), FIG. (C) is Figure 1 (A)
Figure 1 (D) is a circuit diagram showing the configuration of the level detection circuit of
-(F) are diagrams showing the control characteristics of the level detection circuit in FIG. 1(C), FIG. 2 is an explanatory diagram showing the structure of the vibrating pen in FIG. 1, and FIG. FIG. 4 is a block diagram showing the structure of the arithmetic control circuit, FIG.
FIG. 6 is an explanatory diagram showing the arrangement of the vibration sensor, and FIG. 7 shows a different configuration of the VCA circuit and level detection circuit in FIGS. 2 and 3. FIG. 1... Arithmetic control circuit 3... Vibration pen 4... Vibrator 6... Vibration sensor 8... Vibration transmission plate 15.16... Input boat 52... Envelope detection circuit 54.58 ... Signal detection circuit 59 ... A/D conversion circuit 112 - VCA circuit 113 ... Level detection circuit

Claims (1)

[Claims] 1) In a coordinate input device that detects vibration input from a vibrating pen using a plurality of vibration sensors provided on a vibration transmission plate to detect the coordinates of the vibration pen on the vibration transmission plate, the output of the vibration sensor is variable. means for amplifying with a gain; gain control means for controlling the gain of the amplification means via a predetermined time constant according to the output level of the amplification means; and vibration transmission on a vibration transmission plate that takes in the output of the amplification means. Calculating the time, detecting the coordinates of the input point based on the time, and invalidating the initial value of the coordinates detected based on the output of the amplifying means for a period until the gain control via the time constant is stabilized. A coordinate input device characterized by comprising a control means.