JP3166989B2 - Coordinate input device and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate input device, and more particularly, to a method of detecting an input elastic wave vibration by detecting a transmission delay time of the input elastic wave vibration by using a plurality of sensors provided on a vibration transmission plate. The present invention relates to an apparatus for detecting the coordinates of a vibration input point based on the information.

[0002]

2. Description of the Related Art A coordinate input device using ultrasonic vibration is a method of calculating a position coordinate by detecting a transmission delay time of a wave propagating on a tablet as an input surface, and a matrix is provided on the tablet. Since no work such as a wire is performed, an inexpensive device can be provided. Moreover, if a transparent plate glass is used as a tablet, a coordinate input device having an input surface with higher transparency than other methods can be configured.

In such a coordinate input device utilizing ultrasonic vibration, when the wavelength of an elastic wave propagating on a vibration transmission plate becomes larger than the plate pressure of the vibration transmission plate, a plate wave having a different group velocity and a different phase velocity is generated. It is well known to propagate. When this wave is used, the detection point of the phase delay time is defined as the point where the amplitude is equal to or higher than a certain level, and the detection point of the group delay time is defined as the peak of the envelope of the detection signal waveform. FIG. 7 schematically shows the relationship with the delay time. The group delay time tg indicates a relationship that is continuous but has a large fluctuation width, and the phase delay time tp indicates a stepwise relationship. This relationship is attributed to the properties of the plate wave having different phase velocities and group velocities. In this case, it is impossible to measure accurately with distance calculation using only the group delay time, and when distance calculation is performed using the phase delay time, even if the level of the detection signal waveform is electrically constant, attenuation of sound waves and Even if the influence of the pen pressure dependency is removed, the relationship between the phase delay time and the distance as shown in FIG. 7 remains in a staircase shape, and when the value ta is output in FIG. Nakano L
There is a disadvantage that it cannot be determined whether the number is 2.

In order to solve this problem, there has been proposed a method of calculating both coordinates by detecting both the group delay time and the phase delay time of a plate wave. In this method, when the distance between the sensor and the vibration input source is d, d = Vp · Tp + n · λp (1) n = int [(Vg · Tg−Vp · Tp) / λp + 1 / N] (2) Vp: plate Wave phase velocity, Tp: phase delay time Vg: group velocity of plate wave, Tg: group delay time λp: wavelength of plate wave Calculate the distance to each sensor, and geometrically coordinate from this information. Is calculated. This method is an excellent method that can calculate coordinates using a plate wave without depending on the level of a detection signal waveform.

[0005]

In the above system, the obtained coordinate accuracy depends on the delay time measurement accuracy. However, the distance measurement may include an error due to a change in the ambient temperature of the coordinate input device.

FIG. 8 shows the measured data.

[0007] FIG.
The linear distance of [mm] is measured, and the deviation from the true value at that time is plotted with a width of ± 1 [mm] from the center.

When the ambient temperature is changed, the room temperature is 22.5
What was measured accurately in [° C] is +40
At + 5 ° C., there is a certain amount of deviation from the actual distance. Due to this shift, the accuracy of coordinate determination is deteriorated.

On the other hand, a method of maintaining the accuracy by correcting the distance measurement result by providing a temperature measuring means and subtracting a deviation from the temperature, or applying a vibration to a point at a certain distance is known. For example, there is a method of performing zero point correction as described later to maintain accuracy.

However, the former method requires temperature measuring means other than a circuit necessary for actual coordinate determination, and has problems such as an increase in cost due to an increase in circuit scale and an increase in power consumption. Further, in the latter, since an extra operation is required every time the temperature changes, the operation becomes complicated, and furthermore,
A new problem arises in that an instruction to a point with a known distance must be secured with high accuracy.

The present invention has been made in view of the above conventional example, and has as its object to provide a coordinate input device capable of correcting a measurement error due to a change in environmental temperature and inputting coordinates with high accuracy.

[0012]

Means for Solving the Problems and

In order to achieve the above object, the coordinate input device of the present invention has the following configuration. A coordinate input device that calculates and outputs coordinates of a vibration input position on the vibration transmission plate by elastic wave vibration input to the vibration transmission plate, and includes a plurality of detection devices that detect vibration propagating through the vibration transmission plate. Means, measuring means for measuring each delay time from when vibration is input to detection by each of the plurality of detection means, and from each of the plurality of detection means to the vibration input position based on the delay time Calculation means for calculating the distance of, an error calculation means for calculating an error included in each distance based on the distance calculated by the calculation means, a correction means for correcting the distance according to the error, and the correction means Means for calculating a coordinate position based on the corrected distance.

[0013]

FIG. 1 shows the structure of a coordinate input device according to this embodiment. In the figure, 1 controls the entire apparatus,
This is an arithmetic control circuit that calculates a coordinate position. A vibrator driving circuit 2 vibrates the pen tip in the vibrating pen 3. Reference numeral 8 denotes a vibration transmission plate made of a transparent member such as an acrylic or glass plate. The coordinate input by the vibration pen 3 is performed by touching the vibration transmission plate 8. In practice, the area indicated by the symbol A indicated by a solid line in the drawing (hereinafter referred to as an effective area)
The inside is designated by the vibration pen 3. A vibration isolator 7 is provided on the outer periphery of the vibration transmission plate 8 to prevent (reduce) the reflected vibration from returning to the center, and a mechanical vibration such as a piezoelectric element is applied to the boundary at the boundary. Are fixed.

Reference numeral 9 denotes a signal waveform detection circuit for outputting a vibration indicating that the vibration is detected by each of the vibration sensors 6a to 6d to the arithmetic and control circuit 1. Reference numeral 11 denotes a display such as a liquid crystal display capable of displaying in units of dots, and is disposed behind the vibration transmission plate. Then, by driving the display drive circuit 10, dots are displayed at the positions traced by the vibration pen 3 and can be viewed through the vibration transmission plate 8 made of a transparent member.

The vibrator 4 built in the vibrating pen 3 is driven by the vibrator driving circuit 2. The driving signal of the vibrator 4 is supplied as a low-level pulse signal from the arithmetic and control circuit 1, amplified by the vibrator driving circuit 2 with a predetermined gain, and applied to the vibrator 4. The electric drive signal is converted into mechanical ultrasonic vibration by the vibrator 4 and the pen tip 5
Is transmitted to the vibration transmission plate 8 via the

Here, the vibration frequency of the vibrator 4 is selected to a value capable of generating a plate wave on the vibration transmission plate 8 such as glass. In addition, when the vibrator is driven, a mode of vibrating in the vertical direction in FIG. Further, by setting the vibration frequency of the vibrator 4 to the resonance frequency including the pen tip 5, vibration conversion can be performed with higher efficiency.

The elastic wave transmitted to the vibration transmitting plate 8 as described above is a plate wave, and has an advantage that the surface of the vibration transmitting plate 8 is less susceptible to scratches or obstacles than surface waves. Have.

<Description of Arithmetic Control Circuit> In the above-described configuration, the arithmetic control circuit 1 operates every predetermined period (for example, every 5 ms).
Then, a signal for driving the vibrator driving circuit 2 to drive the vibrator 4 in the vibrating pen 3 is output, and time counting by an internal timer (constituted by a counter) is started. The vibrations generated by the vibration pen 3 are transmitted to the vibration sensors 6a to 6a.
It arrives with a delay according to the distance to d.

The vibration waveform detecting circuit 9 includes the vibration sensors 6a to 6a.
6d is detected, and a signal indicating the timing of arrival of the vibration at each vibration sensor is generated by a waveform detection process described later. The arithmetic and control circuit 1 inputs this signal for each sensor and outputs the signal to each vibration sensor. Detecting the vibration arrival time from 6a to 6d and calculating the coordinate position of the vibration pen.

The arithmetic and control circuit 1 drives the display drive circuit 10 based on the calculated position information of the vibration pen 3 to control the display on the display 11,
Alternatively, coordinates are output to an external device by serial or parallel communication (not shown). FIG. 3 is a block diagram showing a schematic configuration of the arithmetic and control circuit 1 according to the embodiment. Each component and its operation are described below.

In the figure, reference numeral 31 denotes a microcomputer for controlling the arithmetic control circuit 1 and the whole coordinate input device, and includes an internal counter, a ROM for storing operation procedures, a RAM for use in calculations and the like, and a nonvolatile for storing constants and the like. It is composed of a non-volatile memory and the like.

Reference numeral 33 denotes a timer (constituting, for example, a counter) for counting a reference clock (not shown), which is a start signal for causing the vibrator driving circuit 2 to start driving the vibrator 4 in the vibrating pen 3. When a signal is input, the timing starts. As a result, the start of timing and the detection of vibration by the sensor are synchronized, and the delay time until vibration is detected by the sensors (6a to 6d) can be measured.

The circuits constituting the other components will be described step by step.

The vibration arrival timing vibrations from the vibration sensors 6 a to 6 d output from the vibration wave detection circuit 9 are transmitted to the latch circuits 34 a to 34 d via the detection signal input port 35.
Is input to

Each of the latch circuits 34a to 34d includes
It corresponds to each of the vibration sensors 6a to 6d, and when a timing signal from the corresponding sensor is received, the time value of the timer 33 at that time is latched. When the determination circuit 36 determines that all the detection signals have been received in this way, it outputs a signal to that effect to the microcomputer 31.

When the microcomputer 31 receives the signal from the determination circuit 36, the latch circuits 34a-34
The arrival time of the vibration from d to each vibration sensor is read from the latch circuit, and a predetermined calculation is performed to calculate the coordinate position of the vibration pen 3 on the vibration transmission plate 8.

By outputting the coordinate position information to the interface circuit via the I / O port 37, the coordinate value can be output to the external device.

<Description of Vibration Propagation Time Detection (FIGS. 4 and 5)
Hereinafter, the principle of measuring the vibration arrival time up to the vibration sensor 3 will be described.

FIG. 4 is a diagram for explaining a detection waveform inputted to the vibration waveform detection circuit 9 and a process of measuring a vibration transmission time based on the detection waveform. Hereinafter, the case of the vibration sensor 6a will be described, but other vibration sensors 6b, 6c,
The same is true for 6d.

It has already been described that the measurement of the vibration transmission time to the vibration sensor 6a starts simultaneously with the output of the start signal to the vibrator drive circuit 2. At this time, the drive signal 41 is applied from the transducer drive circuit 2 to the transducer 4. The ultrasonic vibration transmitted from the vibration pen 3 to the vibration transmission plate 8 by the signal 41 advances over a time tg corresponding to the distance to the vibration sensor 6a, and is detected by the vibration sensor 6a. A signal indicated by reference numeral 42 indicates a signal waveform detected by the vibration sensor 6a.

Since the vibration used in this embodiment is a plate wave, the relationship between the envelope 421 and the phase 422 of the detected waveform depends on the propagation distance in the vibration transmission plate 8 during the transmission of the vibration. Will change accordingly. Here, the traveling speed of the envelope 421, that is, the group velocity is Vg, and the phase velocity of the phase 422 is Vp. The distance between the vibration pen 3 and the vibration sensor 6a can be detected from the group velocity Vg and the phase velocity Vp.

First, focusing only on the envelope 421, the speed is Vg. When a peak on a specific waveform point, for example, an inflection point or a signal shown in FIG. The distance between 6a is given by d = Vg · tg (3), where tg is the vibration transmission time. This equation is for one of the vibration sensors 6a, but the same equation is used for the other three vibration sensors 6b.
6d and the distance between the vibrating pen 3 can be similarly expressed.

Further, in order to determine coordinates with higher accuracy, processing based on detection of a phase signal is performed.

The time from a specific detection point of the phase waveform signal 422, for example, the application of vibration to the zero cross point after a certain signal level 46 is represented by tp45 (a window signal 44 having a predetermined width with respect to the signal 47 is generated. (Obtained by comparison with the signal 422), the distance between the vibration sensor and the vibration pen is as follows: d = n · λp + Vp · tp (1) Here, λp is the wavelength of the elastic wave, and n is an integer.

From the above equations (1) and (3), the above integer n
Is represented as n = [(Vg · tg−Vp · tp) / λp + 1 / N] (2)

Here, N is a real number other than "0", and an appropriate value is used. For example, if N = 2, then n can be determined if there is a change in tg or the like within ± 1/2 wavelength. The distance between the vibration pen 3 and the vibration sensor 6a can be accurately measured by substituting n obtained as described above into the expression (2). The generation of the signals 43 and 45 for the measurement of the two vibration transmission times tg and tp described above
This is performed by the vibration waveform detection circuit 9, which is configured as shown in FIG.

FIG. 5 is a block diagram showing the configuration of the vibration waveform detection circuit 9 of the embodiment.

In FIG. 5, the output signal of the vibration sensor 6a is amplified by a preamplifier circuit 51 to a predetermined level. The amplified signal is filtered by a band-pass filter 511 to remove unnecessary frequency components from the detection signal, and is input to, for example, an envelope detection circuit 52 including an absolute value circuit and a low-pass filter. Is taken out. The timing of the envelope peak is detected by the envelope peak detection circuit 53. The peak detection circuit detects a signal tg (fourth signal) which is an envelope delay time detection signal having a predetermined waveform by a tg signal detection circuit 54 including a monomultivibrator or the like.
A signal 43) is formed and input to the arithmetic and control circuit 1.

On the other hand, reference numeral 55 denotes a signal detection circuit, which is an envelope signal 42 detected by the envelope detection circuit 52.
A pulse signal 47 of a portion exceeding a predetermined level threshold signal 46 in 1 is formed. Reference numeral 56 denotes a short-stable multivibrator, which opens the gate signal 44 having a predetermined time width triggered by the first rising of the pulse signal 47. 57 is t
This is a p-comparator, which detects the first rising zero-cross point of the phase signal 422 while the gate signal 44 is open, and supplies the phase delay time signal tp45 to the arithmetic and control circuit 1. The circuit described above is for the vibration sensor 6a, and the other vibration sensors are provided with the same circuit. <Description of Circuit Delay Time Correction> The vibration transmission time latched by the latch circuit includes a circuit delay time et and a phase offset time toff. The errors caused by the above always include the same amount when the vibration is transmitted from the vibration pen 3 to the vibration transmission plate 8 and the vibration sensors 6a to 6d.

Therefore, for example, the distance from the position of the origin O in FIG. 6 to the vibration sensor 6a is R1 (= X /
2), the input of the vibration at the origin O with the vibrating pen 3 and the actually measured vibration transmission time from the origin O to the sensor 6a are represented by t.
gz ', tpz', and if the true transmission time from the origin O to the sensor is tgz, tpz, these are the circuit delay time et and the phase offset toff: tgz '= tzz + et (4) ) There is a relationship.

On the other hand, an actual measurement value t at an arbitrary input point P
Similarly, g ′ and tp ′ are as follows: tg ′ = tg + et (6) tp ′ = tp + et + toff (7) When the difference between the equations (4), (6), (5), and (7) is obtained, tg'-tgz '= (tg + et)-(tgz + et) = tg-tgz (8) tp'-tpz '= (tp' + et + toff)-(tpz + et + toff) = tp-tpz (9) The circuit delay time et and the phase offset toff included in each transmission time are removed, and input is performed from the position of the origin O. The difference in the true transmission delay time according to the distance at which the position of the sensor 6a between the points P is tactile can be obtained, and the above (1)
The distance difference can be obtained by using the equation (2).

Since the distance from the vibration sensor 6a to the origin O is stored in advance in an unexpected memory or the like and is known, the distance between the vibration pen 3 and the vibration sensor 6a can be determined. The same applies to the other sensors 6b to 6d.

The actual measured values tgz 'and tpz' at the origin O are stored in a non-volatile memory at the time of shipment, and (1)
The equations (8) and (9) are executed before the calculation of the equation (2), so that highly accurate measurement can be performed.

<Description of Coordinate Position Calculation (FIG. 6)> Next, the principle of detecting the coordinate position on the vibration transmitting plate 8 by the vibration pen 3 will be described.

Now, near the middle point of the four sides on the vibration transmission plate 8,
When the two vibration sensors 6a to 6d are provided at the positions of the symbols S1 to S4, the linear distances da to dd from the position P of the vibration pen 3 to the positions of the vibration sensors 6a to 6d are based on the principle described above. You can ask. Further, based on the linear distances da to dd calculated by the arithmetic and control circuit 1, the coordinates (x, y) of the position P of the vibration pen 3 can be obtained from the theorem of three squares as in the following equation.

X = (da + db) · (da−db) / 2X (10) y = (da + dd) · (da−dd) / 2Y (11) or x = (dc + dd) · (dc−dd) / 2X ( 10) ′ y = (db + dd) · (db−dd) / 2Y (11) ′ where X and Y are the distance between the vibration sensors 6a and 6b (or between 6c and 6d), respectively, and between the vibration sensors 6a and 6c ( Or between 6b and 6d).

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

In the above configuration, when the temperature around the apparatus changes, a certain distance measurement error (offset distance) occurs as described above. This is because the propagation delay time has a time difference (offset time) according to the temperature (different from the phase offset described above). The main offset is generated by the input pen, and it has been experimentally found that each sensor has substantially the same value. Now here,
The true distance from each sensor to a certain input point is da, db,
dc, dd, and the distances calculated from the vibration transmission delay time are da ', db', dc ', dd', and the offset distance is Δd: da '= da + Δd (12) db' = db + Δd (13) dc '= Dc + Δd (14) dd' = dd + Δd (15)

In the configuration of FIG. 6, the relationship between the distances is 3
According to the square theorem, a relationship of da ² + dd ² = db ² + dc ² (16) is obtained.

Now, when the same calculation is performed for da ′, db ′, dc ′, and dd ′, considering the equation (16), da ′ ² + dd ′ ² −db ′ ² −db ′ ² = 2Δd ((da-db) + (dd-dc)) (17)

From the equations (12) to (15), since da-db = da'-db '(18) dd-dc = dd'-dc' (19), the offset distance Δd is 2Δd = (da ′ ²⁾ + dd ' ² -db' ² -dc ' ² ) / (da' + dd'-db'-dc ') (20) However, except for the point of da' + dd '= db' + dc '(21) Then, the distance of each sensor is actually measured at the point where the equation (20) can be calculated, the offset distance Δd is calculated, and this value is subtracted from the actually measured value to remove an error due to a temperature change.

[0052]

[Other embodiments] Offset distance Δ calculated by the above procedure
By storing d and performing the coordinate calculation using the value as an error due to temperature for a certain period of time, it becomes possible to correct the coordinates without affecting the calculation speed of the coordinate calculation. How to determine the fixed period may be determined according to the use situation, for example, when performing coordinate sampling at a certain sampling cycle,
It is also possible to calculate the offset distance each time the number of times of sampling reaches a specified value, and to update the stored correction value. Of course, it is also possible to measure at regular time intervals.

Alternatively, it is also possible to determine an input area, for example, an area such as a menu in advance, and to recalculate the offset distance when an input is made at that location.

The correction calculation of the coordinates may be performed using the same value only during the input period using the data of the first point where the input is started.

FIG. 9 shows a flowchart of the coordinate correction of the coordinate input device in this embodiment. The apparatus has the same configuration as the previous embodiment, but the microcomputer 31 calculates the offset distance according to the procedure of FIG.

First, at each timing as described above, that is, when an input is made in a predetermined period or in a predetermined area, for example,
The offset determination operation is started from step S91. As described in the previous embodiment, the operation from pen driving to a series of data acquisition is performed in step S92. At this time, the state of the pen is tested in step S93, and if data cannot be obtained in the pen-up state, the drive in step S92 is repeated. If data is acquired by pen-down, step S
At 94, a distance calculation is performed for each sensor. In step S95, it is determined whether or not calculation of equation (20) is possible for the calculated distance.
The offset distance is calculated in 96, and the calculated value of the offset distance is stored in the RAM or the like in the microcomputer 31 in step S97. If not, the process returns to pen driving (step S92) and the same operation is repeated again.

Here, in the determination of step S95, (2
Although the judgment is made under the condition of the expression (1), not only the case where the expression (21) is strictly satisfied is excluded, but also, for example, | da '+ dd'-db'-dc' | <ERth (22) In addition, the case where the absolute value of the left side is smaller than a certain value ERth is not calculated, and the calculation of the offset distance is not performed near the point where the equation (21) is satisfied.
The error generated when the denominator of the equation (0) is smaller than the numerator can be reduced, and the accuracy can be improved. ER
The value of th may be arbitrarily determined according to the accuracy of the apparatus.

Although the above-described calculation of the offset distance has been performed for the distance between the pen and the sensor, the offset time can be similarly calculated by converting the distance to the transmission delay time.

Further, in the previous embodiment, it is described that the correction is performed based on the calculation result of a certain computable point.
By taking a method of sampling a plurality of points and using the average thereof, more accurate correction can be performed.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of one device. Needless to say, the present invention can be applied to a case where the present invention is achieved by supplying a program to a system or an apparatus.

[0061]

As described above, according to the present invention, the vibration transmission
Vibration propagating through the plate is detected and multiple
Each delay until detected by each detection means
Measuring the time, based on the delay time, the plurality of detecting means
Calculate the distance from each to the vibration input position, and calculate
Errors included in each distance based on the distance calculated by the step
Calculating the difference and correcting the distance according to the error;
Coordinate position based on the distance corrected by
Therefore, input at a known or arbitrary position before inputting coordinates
There is an effect that a coordinate error can be input by correcting a measurement error due to a change in environmental temperature or the like without performing an operation .

[Brief description of the drawings]

FIG. 1 is a block diagram of a coordinate input device.

FIG. 2 is a diagram illustrating a configuration of a vibration pen.

FIG. 3 is an internal configuration diagram of an arithmetic control circuit in the embodiment.

FIG. 4 is a time chart of signal processing.

FIG. 5 is a block diagram of a signal detection circuit.

FIG. 6 is a diagram showing a coordinate system of the coordinate system input device.

FIG. 7 is a relationship diagram between a group delay time and a phase delay time.

FIG. 8 is a diagram illustrating a change in a distance error with respect to a temperature change.

FIG. 9 is a flowchart of an offset distance calculation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Operation control circuit, 2 ... Vibrator drive circuit, 3 ... Vibration input pen, 4 ... Vibrator, 5 ... Pen tip, 6a-6d ... Vibration sensor, 7 ... Vibration-proof material, 8 ... Vibration transmission plate, 9 ... This is a signal waveform detection circuit.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yuichiro Yoshimura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Katsuyuki Kobayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Ryozo Yanagisawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-61-214017 (JP, A) JP-A-1-237712 (JP) , A) JP-A-2-130620 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G06F 3/03

Claims (8)

(57) [Claims] 1. A coordinate input device that calculates and outputs coordinates of a vibration input position on the vibration transmission plate by elastic wave vibration input to the vibration transmission plate, wherein the vibration propagating through the vibration transmission plate is A plurality of detecting means for detecting, a measuring means for measuring a respective delay time from when a vibration is input until the vibration is detected by each of the plurality of detecting means, and a plurality of detecting means based on the delay time. a calculating means for calculating the distance to the vibration input position, an error calculation means for calculating an error included in each distance based on the distance calculated by the calculated detecting means, the calculated by the calculation means in accordance with said error A coordinate input device comprising: a correction unit that corrects a distance; and a unit that calculates a coordinate position based on the distance corrected by the correction unit. 2. The apparatus according to claim 1, further comprising a storage unit configured to store the error, wherein the correction unit corrects the distance according to the error stored in the storage unit.
2. The coordinate input device according to 1. 3. The error calculating means has means for determining that an error included in the distance calculated by the calculating means cannot be calculated, and does not perform error calculation if calculation is impossible. The coordinate input device according to claim 1, wherein 4. An error included in the distance measured by the measuring unit is caused by a fluctuation in vibration transmission delay time due to a change in environmental temperature, and is caused by a difference between each of the plurality of coordinate detecting units and a vibration input point. 2. The coordinate input device according to claim 1, wherein the distance includes an error included in the same value. 5. A coordinate input method for calculating and outputting coordinates of a vibration input position on the vibration transmission plate according to elastic wave vibration input to the vibration transmission plate, wherein the vibration is input after the vibration is input. A measuring step of measuring each delay time until each of the plurality of detection means for detecting the vibration propagating through the transmission plate, and a step of measuring the delay time from each of the plurality of detection means to the vibration input position based on the delay time A calculating step for calculating the distance; an error calculating step for calculating an error included in each distance based on the distance calculated in the calculating step; and a correcting step for correcting the distance calculated by the calculating means according to the error. And a step of calculating a coordinate position based on the distance corrected in the correction step. 6. The coordinate input method according to claim 5, wherein the correcting step corrects the distance in accordance with an error stored in a storage unit that stores the error. 7. The error calculating step includes a step of determining that an error included in the distance calculated in the calculating step cannot be calculated. If the calculation cannot be performed, the error calculation is not performed. The coordinate input method according to claim 5, wherein 8. An error included in the distance measured in the measuring step is caused by a vibration transmission delay time fluctuating with a change in environmental temperature, and is caused by a difference between each of the plurality of coordinate detecting means and the vibration input point. 6. The coordinate input method according to claim 5, wherein each of the distances is an error included in the same value.