JPH07110738A - Handwriting input pen device - Google Patents

Abstract

PURPOSE:To prevent the degradation in precision of detected coordinates due to the difference between axes of accleration sensors provided in a handwriting input pen and those or the output coordinate system of writing information. CONSTITUTION:Two acceleration sensors 2a and 2b are provided perpendicularly to the shaft of an input pen orthogonally to each other, and acceleration signals from these sensors 2a and 2b are integrated twice to obtain writing information in the X-axis direction and that in the Y-axis direction in the output coordinate system. In the correction value taking-in mode, a coordinate calculating device 18 obtains and stores the correction value related to the angular deviation between axes of sensors and coordinate axes of the output coordinate system based on acceleration signals for linear writing in the X-axis or Y-axis direction. The locus information input mode, coordinate calculating devices 18 to 20 convert acceleration signals from sensors 2a and 2b to acceleration signals for coincidence between axes of sensors 2a and 2b and coordinate axes of sensors 2a and 2b based on the stored correction value. Converted acceleration signals are used in the processing of twice integrating or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a handwriting pen input device for inputting character and graphic pattern information with a handwriting input pen.

[0002]

2. Description of the Related Art Conventionally, as a device of this type, two acceleration sensors arranged in the X-Y axis directions which are perpendicular to the pen axis of a handwriting input pen and orthogonal to each other are used for the pen writing operation.
Axis and Y axis direction acceleration is measured, the acceleration signal is integrated twice, and the pen's handwriting input is obtained by inputting text and graphic information by the method of obtaining the pen's X-Y axis movement distance. There was something to do.

[0003]

However, in the device having the above-mentioned structure, when the writer randomly holds the pen to write, the writer is internally provided on the XY axes of the output coordinate system (or the writing board) and the pen. It is extremely rare that the XY axis of the acceleration sensor or the writing direction and the XY axis of the acceleration sensor coincide with each other. Even if the acceleration signal obtained from the acceleration sensor is integrated twice, There was a drawback that it did not match the writing distance of.

In addition, it is rare for a writer to write vertically with an input pen standing upright with respect to the writing plate, and it is common for the writer to incline at an arbitrary angle depending on the individual difference of the writer. In the apparatus having the above structure, the acceleration signal from the acceleration sensor provided in the orthogonal axis direction on the plane perpendicular to the longitudinal axis of the pen does not represent the true acceleration. Therefore, there is a drawback that the true writing distance of the pen does not match even if the acceleration signal obtained from the acceleration sensor is integrated twice.

The present invention has been made in consideration of the above points, and prevents the accuracy of the detected coordinates from deteriorating due to the difference between the axis of the acceleration sensor provided in the handwriting input pen and the output coordinate system of the handwriting information. It is intended to provide a handwriting input pen device that can be used.

Another object of the present invention is to provide a handwriting input pen device which can obtain accurate handwriting information even when the handwriting input pen is inclined with respect to the writing surface.

[0007]

According to the present invention of claim 1, the first and second acceleration sensors are provided so as to be perpendicular to the axial direction of the input pen and orthogonal to each other, and the coordinate calculation device allows these acceleration In a handwriting input pen device that integrates an acceleration signal from a sensor twice to obtain handwriting information in the X-axis direction and the Y-axis direction in an output coordinate system, in addition to a mode for obtaining trajectory information in each direction, a correction value acquisition mode In the correction value acquisition mode, the coordinate calculation device determines the axis of each acceleration sensor and the coordinate axis of the output coordinate system based on the acceleration signal from each acceleration sensor when writing a straight line in the X-axis or Y-axis direction. In a mode of obtaining and storing a correction value related to the angular deviation of, and obtaining the trajectory information in each direction, the coordinate calculation device calculates the acceleration signal from each acceleration sensor based on the stored correction value. Converts the acceleration signal when the coordinate axes of the shaft and the output coordinate system of the acceleration sensor are the same,
It is characterized in that the converted acceleration signal is integrated twice to obtain handwriting information in the X-axis direction and the Y-axis direction in the output coordinate system.

According to the second aspect of the present invention, the first and second acceleration sensors are provided so as to be perpendicular to the axial direction of the input pen and orthogonal to each other, and the coordinate calculation device outputs the acceleration signals from these acceleration sensors. In a handwriting input pen device that integrates twice and obtains handwriting information in the X-axis direction and the Y-axis direction in the output coordinate system, a third acceleration sensor that is parallel to the axial direction of the input pen is provided, and an operation mode is also set. In addition to the mode for obtaining trajectory information in each direction, a correction value acquisition mode is provided, and in the correction value acquisition mode, the coordinate calculation device
A correction value related to the angular deviation between the axes of the first and second acceleration sensors and the coordinate axis of the output coordinate system based on the acceleration signals from the three acceleration sensors when writing a straight line in the X-axis or Y-axis direction. In a mode for obtaining and storing the information and obtaining the trajectory information in each direction, the coordinate calculation device calculates the acceleration signals from the first and second acceleration sensors based on the stored correction values. And to convert into an acceleration signal when the coordinate axes of the output coordinate system match, and obtain the handwriting information in the X-axis direction and the Y-axis direction in the output coordinate system by integrating the converted acceleration signal twice. Is characterized by.

According to the third aspect of the present invention, the first and second acceleration sensors are provided so as to be perpendicular to the axial direction of the input pen and orthogonal to each other, and the coordinate calculation device receives the acceleration signals from these acceleration sensors. In a handwriting input pen device that integrates twice and obtains handwriting information in the X-axis direction and the Y-axis direction in the output coordinate system, a third acceleration sensor that is parallel to the axial direction of the input pen is provided, and an operation mode is also set. In addition to the mode for obtaining trajectory information in each direction, a correction value acquisition mode is provided, and in the correction value acquisition mode, the coordinate calculation device
A correction value related to the angular deviation between the axes of the first and second acceleration sensors and the coordinate axis of the output coordinate system based on the acceleration signals from the three acceleration sensors when writing a straight line in the X-axis or Y-axis direction. In the mode for obtaining and storing the following, and obtaining the trajectory information in each direction, the coordinate calculation device obtains the inclination angle change of the input pen accompanying the vertical writing based on the acceleration signal from the third acceleration sensor, From the change in the tilt angle and the correction value stored in the correction value acquisition mode.
The acceleration signal from the acceleration sensor is converted into an acceleration signal when the axes of the acceleration sensor and the coordinate axis of the output coordinate system match, and the converted acceleration signal is integrated twice to output the coordinate system. The handwriting information in the X-axis direction and the Y-axis direction in is obtained.

[0010]

According to the present invention, the first and second acceleration sensors are provided so as to be perpendicular to the axial direction of the input pen and orthogonal to each other. It is assumed that the handwriting input pen device obtains handwriting information in the X-axis direction and the Y-axis direction in the output coordinate system by integrating the acceleration signal of 2 times.

It is not clear how the writer holds the handwriting input pen in such a handwriting input pen device, and the axes of the acceleration sensors and the coordinate axes of the output coordinate system often do not match. Even if the handwriting information is obtained from the acceleration signal from the acceleration sensor, it is often inaccurate.

In consideration of this point, the present inventions according to claims 1 to 3 are intended to eliminate the inaccuracy due to the gripping method by correcting the acceleration signal. The value to be corrected is obtained from the acceleration signal at that time by executing straight line writing in the X-axis or Y-axis direction of the output coordinate system in the correction value fetching mode.

According to the first aspect of the present invention, in the correction value acquisition mode, based on the acceleration signals from the two installed acceleration sensors, the angular deviation between the axis of each acceleration sensor and the coordinate axis of the output coordinate system. And stores the information as a correction value. Then, in the normal mode for obtaining the trajectory information in each direction, the axis of each acceleration sensor and the coordinate axis of the output coordinate system match the acceleration signal from each acceleration sensor based on the stored correction value. Then, the converted acceleration signal is integrated twice to obtain handwriting information in the X-axis direction and the Y-axis direction in the output coordinate system.

According to the second aspect of the present invention, a third acceleration sensor parallel to the axial direction of the input pen is provided, and in the correction value taking mode, the first and second acceleration sensors are used based on the acceleration signals from the three acceleration sensors. A correction value related to the angular deviation between the axis of the second acceleration sensor and the coordinate axis of the output coordinate system is calculated and stored. That is, the correction value that also takes into consideration the inclination of the input pen with respect to the writing surface is stored. Then, in the normal mode in which the trajectory information in each direction is obtained, the acceleration signals from the first and second acceleration sensors are compared with the axes of these acceleration sensors based on the stored correction values, in consideration of the inclination. It is converted into an acceleration signal when the coordinate axes of the output coordinate system match, and the converted acceleration signal is integrated twice to obtain handwriting information in the X-axis direction and the Y-axis direction in the output coordinate system.

The present invention according to claim 3 is substantially the same as the present invention according to claim 2, but in the normal mode in which the trajectory information in each direction is obtained, the inclination of the input pen changes in writing in the vertical direction. In consideration of this, the inclination angle change of the input pen accompanying the vertical writing is calculated based on the acceleration signal from the third acceleration sensor, and the calculated inclination angle change and the correction value acquisition mode are stored. The first and second
The acceleration signal from the acceleration sensor is converted into an acceleration signal when the axes of the acceleration sensor and the coordinate axis of the output coordinate system are coincident with each other, and the converted acceleration signal is integrated twice to obtain X in the output coordinate system. It is intended to obtain handwriting information in the axial direction and the Y-axis direction.

[0016]

【Example】

(A) First Embodiment Hereinafter, a first embodiment of the handwriting input pen device according to the present invention will be described in detail with reference to the drawings.

The handwriting input pen device of this embodiment comprises a handwriting input pen and a coordinate calculation device (for example, a computer). First, the handwriting input pen will be described with reference to FIG. FIG. 2 is a perspective view showing the handwriting input pen with a part of the case cut away.

In FIG. 2, a case 11 for accommodating various components has a generally cylindrical shape with an upper part closed, and a lower part is gradually reduced in diameter and the lowermost part is opened.

A pen tip member 1 having a shape obtained by dividing an ellipsoid into two or a paraboloid shape has a part thereof protruding outward from an opening of a case 11 and rubs a writing surface (for example, a display surface) 9 during writing. It is something that moves. The pen tip member 1 is attached to the damper 12a by penetrating an annular lower damper 12a that is fixed to a reduced diameter portion inside the case 11 and has a downward diameter.

One end of a support rod 14 is attached to the upper surface of the pen tip member 1 (it is not necessary). This support rod 1
4 is attached to this damper 12b by penetrating an annular upper damper 12b fixed at an appropriate position inside the case 11, and its upper end edge is provided on the upper surface of the upper damper 12b. It is attached to the lower surface of the sensor fixing plate 13.

Two acceleration sensors 2a and 2b are mounted on the upper surface of the sensor fixing plate 13 so that their detection directions are orthogonal to each other and are perpendicular to the axis of the pen. The detection signals (acceleration signals) from the acceleration sensors 2a and 2b can be given to an external coordinate calculation device via the cable 3.

Here, the sensor fixing plate 13 is made of a lightweight elastic material such as plastic in order to reduce the weight of the handwriting input pen device. The support rod 14 is preferably made of a light metal such as aluminum for weight saving, but may be a thin steel wire material such as a piano wire.

Lower damper 12a and upper damper 12b
Are, for example, viscoelastic materials (putty etc.), Styrofoam,
It is made of a material with a very low elastic modulus such as buff material and resin cotton. These dampers 12a and 12b mechanically semi-insulate the pen tip member 1 and the acceleration sensors 2a and 2b from the case 11 to reduce the impact force received by the case 11 and protect the acceleration sensors 2a and 2b from the impact force. It is for.
Further, the vibration of the pen tip member 1 is not transmitted to the case 11, and the vibration is not attenuated even if the case 11 is touched with a hand.

In FIG. 2, two dampers 12a, 1a are provided.
2B is shown, the damper may be formed by filling a lighter material such as styrofoam or viscoelastic material in the entire inside of the case 11 or below the fixing plate 13 to form a damper. The device can be lightened.

In the first embodiment, the button switch 10 is provided on the outer periphery of the case 11, and although the illustration of the internal cable is omitted, this on / off information is also calculated via the cable 3 as an external coordinate calculation. The device is designed so that it can be fed. The method of using this information will be described later.

Next, the functions and detailed configurations of the acceleration sensors 2a and 2b will be described with reference to the drawings.

Each acceleration sensor 2a, 2b is a pen tip member 1.
The acceleration is measured by following the movement of. For example, the acceleration sensor 2a measures the acceleration in the X-axis direction, and the acceleration sensor 2a
The acceleration in the Y-axis direction is measured at b. The acceleration signals measured by the acceleration sensors 2a and 2b are transmitted via a cable 3 to an external coordinate calculation device (for example, a computer; see FIG. 1). As is well known, when the acceleration is integrated twice with time, it can be converted into a distance, new coordinates can be obtained from the distance in each direction, and an external coordinate calculation device performs such processing. That is, the external coordinate calculation device integrates twice to calculate the movement distances of the pen tip member 1 in the X-axis and Y-axis directions, and the trajectory of the two-dimensional movement of the pen tip member 1 is obtained as the XY coordinate.

Obtained handwriting information (a series of coordinate data)
Is often displayed on the display surface even when it is used for character recognition or the like. Even when the writing board 9 is different from the display surface, if the reference point of the display surface and the reference point P of the writing board 9 are made to correspond to each other, the XY coordinate conversion can be easily performed, and the display surface can be accurately displayed. it can.

In the first embodiment, the acceleration sensors 2a, 2b may be of any type, and commonly used ones can be applied. For example, the one shown in FIG. 3 can be applied.

In FIG. 3, a plate-shaped piezoelectric element member 6 having two peripheral or opposing ends fixed by a fixing plate 5.
The mass body 7 is fixed to the central part of the device, and electrodes 8a and 8b can be attached to both surfaces in the detection direction. When the mass body 7 receives an external force and moves in the A direction or the B direction in accordance with the writing operation of the input pen, the piezoelectric element member 6 is distorted, and the amount of distortion (acceleration) is generated between the electrodes 8a and 8b. A potential difference of a magnitude corresponding to is generated.
If the positive or negative direction is determined in advance because the electrode 8a has a high potential or the electrode 8b has a high potential depending on the movement direction of the A direction or the B direction, the acceleration direction becomes clear. An acceleration sensor or the like having a structure in which the piezoelectric element member 6 is a cantilever and a mass is provided at the tip can also be applied. Since the acceleration during the writing operation is very small, the force that the mass body 7 receives is also small.
Therefore, it is preferable that the piezoelectric element member 6 be processed into a thin plate so that even a small force causes distortion and a sufficient potential difference for measurement can be obtained.

Generally, the piezoelectric element member 6 is made of a ceramic material, and since this material is a brittle material, it is damaged when subjected to a large force such as an impact force or a shear stress. By the way, the impact force that occurs when an object falls is 100g (g is the gravitational acceleration).
It is said that the piezoelectric element member 6 is likely to be damaged when receiving such a large impact force. Further, an acceleration sensor utilizing the piezo effect of silicon single crystal is also easily damaged when it receives an impact force. Therefore, even if the input pen falls due to carelessness by the writer, it is essential to reduce the impact force and protect the input pen. Therefore, the dampers 12a and 12b are provided as described above.

Next, the configuration and processing of the coordinate calculation device (for example, mainly composed of a computer) will be described with reference to FIG. FIG. 1 is a block diagram showing a detailed configuration of the coordinate calculation device. Note that, here, a case will be described in which a writing surface is used as the writing board 9 and writing is performed using an input pen.

In FIG. 1, a sampling signal is given to the acceleration sensors 2a and 2b from a clock oscillator (not shown) in the coordinate calculation device.
2b measures the acceleration and returns the acceleration signal to the coordinate calculation device.

When a person writes a character or a figure, the writing speed is 10 m / s at the fastest, and the change frequency of acceleration during the writing operation is generally said to be 10 to 1000 Hz. However, the acceleration signals from the acceleration sensors 2a and 2b are likely to have harmonic noise. Therefore, the filter circuit 15 corresponding to each acceleration sensor 2a, 2b
a and 15b are the acceleration signals filtered to 100
Eliminates harmonic noise above 0 Hz. The noise-removed acceleration signal in each direction is supplied to the amplifiers 16a, 1 for each direction.
After being amplified by 6b, A / D conversion circuits 17a, 1
It is converted into a digital signal by 7b and input to the correction circuit 18.

As will be described in detail later, the correction circuit 18 corrects and converts the input acceleration signal for each direction and outputs the corrected and converted acceleration signal for each direction to the integrating circuits 19a and 19b twice. The two-time integration circuits 19a and 19b time-integrate the digital acceleration signals in each direction twice to convert the digital acceleration signals into distances, and the coordinate conversion circuit 20 calculates the coordinates at the previous sampling time and the obtained distance from the current sampling time. Get the XY coordinates. The coordinate sequence forming such a handwriting is given to the display 21 and displayed on the display surface 9, or given to the character recognition device 22 for character recognition.

Here, the integration time is from receiving a sampling signal to receiving the next sampling signal. Therefore, when the sampling frequency is increased, the accuracy of detecting the writing distance is improved. If the signals from the acceleration sensors 2a and 2b are the accelerations of the display surface 9 in the X-axis and Y-axis directions, the two-time integrated value of each becomes the writing distance in the X-axis and Y-axis directions. When plotted on the display surface 9 as coordinates, written characters or figures are displayed.

Whether or not the pen tip member 1 is in contact with the display surface (writing board) 9 depends on whether or not the portion forming a character or a figure is moved or the portion not forming a character or a figure is moved (in the air). The movement may be distinguished by, for example, constantly pressing the button switch 10 when moving a portion forming a character or a graphic, and when the pen tip member 1 is in contact with the display surface 9. The vibration component of may be extracted from the acceleration signal to be distinguished,
As a result, it is possible to display only the parts that form the characters and figures.

By the way, when the writer randomly holds the input pen, the XY axes of the display surface (output coordinate system) 9
In many cases, the axes of the acceleration sensors 2a and 2b provided inside the input pen do not match. In this case, the acceleration sensor 2
The acceleration signals from a and 2b have values different from the true acceleration of the writing operation of the input pen, and the characters and figures written by the input pen cannot be displayed accurately.

Therefore, it is conceivable that the writer is requested to provide a mark indicating the coordinate system on the input pen and hold the input pen so as to match the coordinate system of the display surface 9. However, even in this case, it is difficult to completely match the two coordinate systems. Further, the writer may randomly rotate the input pen while writing a plurality of characters or figures, and the XY axes may be displaced.

In the first embodiment, therefore, a correction circuit 18 for correcting the acceleration signals from the acceleration sensors 2a and 2b is provided so that accurate coordinates can be obtained even when the two coordinate systems do not match. I have to. This correction circuit 1
The process of 8 is executed by software, for example.

The process of the correction circuit 18 includes a process performed when the handwriting information is input and a process for fetching the correction value performed before that.

First, the process of fetching the correction value will be described in detail with reference to the flowchart of FIG.

For example, the point P at the upper right corner of the display surface 9
An electrode that can take out a trigger signal is provided on the
Is the reference point. When the pressing signal is given from the reference point P electrode, the correction circuit 18 determines that the correction value acquisition processing is instructed, and starts the processing of FIG. The writer is instructed in advance to press the reference point P and write in the X-axis direction on the display surface 9 when the correction value acquisition process is executed.

When the processing shown in FIG. 4 is started, the correction circuit 18 fetches the digital acceleration signal related to the detection of each acceleration sensor 2a, 2b (step 100).

Here, when the X axis (for example, the lateral direction) of the display surface 9 and the axis of the acceleration sensor 2a coincide with each other, only the acceleration sensor 2a outputs, and the output of the acceleration sensor 2b becomes zero. On the other hand, when there is a deviation of an angle θ between the X axis of the display surface 9 and the axis of the acceleration sensor 2a, the accelerations shown in the following equations (1) and (2) are calculated from the acceleration sensors 2a and 2b. The signal is output.

Αa (x) = α (x) × cos θ (1) αb (y) = α (x) × sin θ (2) where αa (x) is the output of the acceleration sensor 2a and αb
(Y) is the output of the acceleration sensor 2b, and α (x) is the true acceleration of the display surface 9 in the X-axis direction.

The correction circuit 18 receives the input acceleration signal α
From a (x) and αb (y), the angle θ between the X axis of the display surface 9 and the axis of the acceleration sensor 2a (difference between the two coordinate systems) is calculated according to the equation (3) (step 101).

Θ = tan ⁻¹ {αb (y) / αa (x)} (3) Therefore, when the axes of the acceleration sensors 2a and 2b are rotated by θ, they coincide with the X-Y axes of the display surface 9. become. That is, when the values of the acceleration signals of the acceleration sensors 2a and 2b are corrected by the angle θ, the true acceleration signals in the X-axis direction and the Y-axis direction of the display surface 9 (output coordinate system) are obtained.

The correction circuit 18 obtains cos θ and sin θ necessary for such rotation processing, stores them as correction values, and ends the series of processing (step 102).

Next, the correction process performed by the correction circuit 18 during normal handwriting information input will be described. Correction circuit 18
Is the input acceleration signals αa (x) and αb (y)
Is converted into an acceleration signal according to the X-axis and Y-axis directions of the display surface 9 by using the correction values cos θ and sin θ, and then integrated twice.

Acceleration sensor 2 during normal handwriting input
The acceleration signal αa (x) from a and the acceleration signal αb (y) from the acceleration sensor 2b are the true acceleration α (x) of the display surface 9 in the X-axis direction and the true acceleration of the display surface 9 in the Y-axis direction. It is expressed by equations (4) and (5) using α (y).

Αa (x) = α (x) cos θ + α (y) sin θ (4) αb (y) = α (y) cos θ + α (x) sin θ (5) Therefore, the XY axis direction True acceleration of α (x), α (y)
Can be expressed by equations (6) and (7) obtained by modifying equations (4) and (5).

Α (x) = {αa (x) cos θ−αb (y) sin θ} ÷ {cos θ ² −sin θ ² } (6) α (y) = {αb (y) cos θ− αa (x) sin θ} ÷ {cos θ ² −sin θ ² } (7) Therefore, when the normal handwriting information is input, the correction circuit 1
8 is the input acceleration signal α from the acceleration sensor 2a.
a (x) and the acceleration signal αb from the acceleration sensor 2b
Using (y) the correction values cos θ and sin θ, (6)
According to the formula and the formula (7), the display surface 9 is converted into a true acceleration α (x) in the X-axis direction and a true acceleration α (y) in the Y-axis direction of the display surface 9, and the twice integration circuit 19a,
19b. Therefore, after that, the true acceleration α
(X) and α (y) are time-integrated twice and converted into a true moving distance according to the XY coordinate system of the display surface 9,
Further converted to true XY coordinates.

According to the first embodiment, even if the writer randomly holds the input pen, the deviation between the coordinate axis of the output coordinate system and the axis of the acceleration sensor is detected to correct the acceleration signal. Therefore, the handwriting information can be input correctly.

Such a correction process is a simple calculation process as described above, and does not impair the real-time property.

(B) Second Embodiment Next, a second embodiment of the handwriting input pen device according to the present invention will be described in detail with reference to the drawings.

First, the handwriting input pen according to the second embodiment will be described. Here, FIG. 5 shows the structure of the handwriting input pen in the second embodiment.
The same or corresponding portions as those in FIG. 2 showing the handwriting input pen of the embodiment are designated by the same reference numerals.

As shown in FIG. 5, the handwriting input pen of the second embodiment has an acceleration in the axial direction of the input pen (hereinafter referred to as the Z-axis direction) as compared with the handwriting input pen of the first embodiment. The difference is that the acceleration sensor 2c to be measured is provided on the sensor fixing plate 3. The acceleration sensor 2c newly added in the second embodiment may have a conventionally well-known configuration, and may be the same as the acceleration sensors 2a and 2b.

Although the support rod 14 and the button switch 10 are not shown in FIG. 5, they may be provided also in the second embodiment. The difference in this point lies in the difference from the second embodiment. It has nothing to do with characteristics.

Also in this second embodiment, basically,
Based on the acceleration signals from the acceleration sensors 2a and 2b,
The moving distance is calculated to sequentially obtain the coordinates at each point on the handwriting. However, the correction process performed by the correction circuit according to how the writer holds the input pen is different from that of the first embodiment. Therefore, the coordinate calculation process in the second embodiment will be described focusing on the correction process.

Although the detailed construction of the coordinate calculating device for the second embodiment is omitted, it is the same as the first embodiment and is different from the first embodiment in that it has three acceleration sensors 2a.
2A to 2c are input to the correction circuit in three lines, and the correction process executed by the correction circuit is different.

When the writer randomly holds the input pen, it is rare that the XY axes on the display surface and the axes of the acceleration sensors 2a and 2b provided in the input pen coincide with each other. Further, as shown in FIG. 6, the writer generally writes with the input pen inclined by a certain angle with respect to the normal direction (Z-axis direction) of the display surface 9. Therefore, the acceleration signals from the acceleration sensors 2a and 2b used for calculating the distance have different values from the true acceleration of the writing operation of the input pen, and the characters or figures written by the input pen cannot be displayed accurately. Therefore, it is necessary to correct the acceleration signals from the acceleration sensors 2a and 2b.

As described above, the second embodiment, like the first embodiment, is intended to reduce an error caused by how the writer grips the input pen. However, the second embodiment differs from the first embodiment in that the error is reduced in consideration of the inclination of the display surface 9 with respect to the Z-axis direction.

Also in this second embodiment, the correction process is
It can be divided into a pre-process for taking in the correction value and a process for actually correcting when inputting handwriting information.

First, the preprocessing for taking in the correction value will be described. Also in this second embodiment, in the preprocessing, the writer is caused to press the reference point P at the upper right corner of the display surface 9 and the writing is performed with the input pen in the X-axis direction (for example, lateral direction) of the display surface 9. Let

First, assuming that the detection planes of the acceleration sensors 2a and 2b are parallel to the display surface (XY plane) 9, the Cartesian coordinate system of the acceleration sensors 2a and 2b is set to the XY coordinates of the display surface 9. Think to match the system. In this case, the same idea as in the first embodiment can be applied. Therefore, it can be seen that in order to make the two coordinate systems coincide with each other, the coordinate system should be rotated by the angle θ represented by the above equation (3).

As shown in FIG. 6, the inclination of the input pen display surface 9 with respect to the X axis is γ, and the inclination of the input pen with respect to the YZ plane in the coordinate system of the display surface 9 is δ.

The angle γ and the angle δ are approximately calculated in the same manner as described above. That is, assuming that the detection planes of the acceleration sensors 2a and 2c are parallel to the XZ plane in the coordinate system of the display surface 9, the angle γ is expressed by the following equation (8), considering that both coordinate systems are made to coincide. It is possible,
In addition, assuming that the detection planes of the acceleration sensors 2b and 2c are parallel to the YZ plane in the coordinate system of the display surface 9, considering that both coordinate systems are matched, the angle δ.
Can be expressed by the following equation (9).

Γ = tan ⁻¹ {αa (x) / αc (z)} (8) δ = tan ⁻¹ {αb (y) / αc (z)} (9) where αc (z) Is an acceleration signal of the acceleration sensor 2c.

At the time of writing in the preprocessing, the angles θ, γ and δ as described above are obtained and stored as correction values.

Next, consider a change in the inclination of the input pen during writing. In the writing operation in the X-axis direction (which is also the writing operation performed in the preprocessing), the movement is a variation angle Φ (generally 40 ° ≧ Φ ≧ 0 °) around the point A of the wrist shown in FIG. However, there is almost no change in the inclination γ with respect to the X axis on the XY plane of the display surface 9, and the angle γ may be regarded as constant.

Further, the writing operation in the Y-axis direction is a circular movement centering on the second indirect point B of the index finger, and the inclination angle of the input pen with respect to the Y-axis in the YZ axis plane also changes. That is, during the writing operation in the Y-axis direction, if the angle β changes by circular motion (generally 25 ° ≧ β ≧ 15 °), the tilt angle of the input pen with respect to the Y-axis in the YZ axis plane also changes by β. To do. At this time, the acceleration sensor 2c is acted upon by the centrifugal force f shown in the equation (10) for the circular motion, and the acceleration signal αc (z) corresponding to the centrifugal force f.
Is output from the acceleration sensor 2c.

F = m × r × ω ² = m × αc (z) (10) Here, m is a mass, ω is an angular velocity, and r is a distance from the center of rotation to the acceleration sensor 2c, which is constant.

Therefore, the inclination angle of the input pen with respect to the Y axis in the coordinate system of the display surface 9 during writing in the Y axis direction is (β + δ), and it is necessary to calculate and correct the angle β during writing. Here, assuming that the detection planes of the acceleration sensors 2a and 2c are parallel to the XZ plane in the coordinate system of the display surface 9, the change angle β is the angular velocity ω, so the change angle β is obtained. Is approximately (1
It can be represented by the formula 1).

Β = √ {Δαc (z)} × ΔT ÷ r (11) where Δαc (z) is the acceleration sensor 2 during writing.
The output change of c, ΔT is the sampling period. (1
Since the distance r in the equation (1) can be given as a constant, and the sampling period ΔT is constant,
From the equation (11), the output change Δαc of the acceleration sensor 2c
It can be seen that the change angle β can be obtained when (z) is obtained.

When various angles θ, γ, δ, β related to the inclination of the input pen are obtained as described above, the acceleration signals αa (x from the acceleration sensors 2a, 2b are geometrically approximated. ), Αb (y), the true acceleration α in the X-axis direction and the Y-axis direction in the coordinate system of the display surface 9
(X) and α (y) can be obtained according to the following equations (12) and (13).

Α (x) = {αa (x) cos θcos δ−αb (y) sin δcos γ} ÷ cos δcos γ (cos θ ² −sin θ ² ) ... (12) α (y) = {αb ( y) cos θcos (δ−β) −αb (y) sin δcos γ} ÷ cos (δ−β) cos γ (cos θ ² −sin θ ² ) ... (13) As described above, the handwriting information is input. Before performing, the correction values are taken in to obtain and store the correction values θ, γ, δ, and when the handwriting information is input, the inclination angle change β is obtained, and these values θ, γ, δ, β are obtained. Based on the acceleration signals αa (x) and αb (y) from the acceleration sensors 2a and 2b, the X-axis direction and Y in the coordinate system of the display surface 9
The true axial accelerations α (x) and α (y) are obtained. Then, the obtained true accelerations α (x) and α (y) are integrated twice to obtain the true writing distance, and further the true coordinates are obtained to obtain accurate handwriting information.

The handwriting information thus obtained is not only displayed on the display surface 9 as in the first embodiment, but also used for character recognition by collation with reference character information.

As described above, according to the second embodiment, since the acceleration sensor 2c is provided to correct the acceleration signal in consideration of the inclination of the input pen, the handwriting more accurate than that of the first embodiment is made. You can get information.

Further, according to the second embodiment, since the acceleration signal is corrected by taking into consideration the inclination angle change during the input of handwriting information, it is possible to obtain more accurate handwriting information.

Therefore, the handwriting information can be correctly input even if the writer randomly holds the input pen, and it is possible to prevent the handwriting information from being influenced by individual differences in how the writer holds the handwriting. it can.

Further, even in the second embodiment, the correction calculation is not so complicated, and the real-time property of handwriting information input is not impaired.

(C) Other Embodiments Note that the writing direction of the straight line to be written to take in the correction value may be the Y-axis direction, unlike the embodiment.

In addition, the mode of the correction value acquisition processing is
The button switch 10 may be instructed by pressing the button switch several times.
May be used.

Further, the signal may be exchanged between the handwriting input pen and the coordinate calculating device by radio.

Furthermore, some or all of the components of the coordinate calculation device may be built in the handwriting input pen side.

[0087]

As described above, according to the present invention, the correction value relating to the angular deviation between the axes of the first and second acceleration sensors and the coordinate axis of the output coordinate system is obtained in the correction value acquisition mode. In the mode of storing and obtaining locus information, the acceleration signals from the first and second acceleration sensors are matched with the axes of these acceleration sensors and the coordinate axes of the output coordinate system based on the stored correction values. The handwriting information can be accurately input because the handwriting information is converted into an acceleration signal when the handwriting is present and the converted acceleration signal is integrated twice to obtain handwriting information in the X-axis direction and the Y-axis direction in the output coordinate system. A handwriting input pen device can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of a coordinate calculation device according to a first embodiment.

FIG. 2 is a partially cutaway perspective view showing a configuration of a handwriting input pen according to the first embodiment.

FIG. 3 is a schematic cross-sectional view showing a configuration example of an acceleration sensor.

FIG. 4 is a flowchart showing a correction value acquisition process of the first embodiment.

FIG. 5 is a partially cutaway perspective view showing a configuration of a handwriting input pen according to a second embodiment.

FIG. 6 is an explanatory diagram of an angular relationship during a writing operation.

[Explanation of symbols]

1 ... Pen point member, 2a, 2b, 2c ... Acceleration sensor, 9
... Writing board (for example, display surface), 18 ... Correction circuit,
19a, 19b ... Integrator circuit twice, 20 ... Coordinate conversion circuit.

Claims (3)

[Claims] 1. A first acceleration sensor and a second acceleration sensor are provided so as to be perpendicular to an axial direction of an input pen and orthogonal to each other, and a coordinate calculation device integrates acceleration signals from these acceleration sensors twice, In the handwriting input pen device that obtains handwriting information in the X-axis direction and the Y-axis direction in the output coordinate system, a correction value acquisition mode is provided in addition to a mode that obtains trajectory information in each direction, and the above coordinate calculation is performed in the correction value acquisition mode. The device is X
Based on the acceleration signals from the first and second acceleration sensors during linear writing in the axis or Y-axis direction, the angular deviation between the axes of the first and second acceleration sensors and the coordinate axes of the output coordinate system In a mode for obtaining and storing a correction value according to the above, and obtaining the trajectory information in each direction, the coordinate calculation device calculates the acceleration signals from the first and second acceleration sensors based on the stored correction values. The handwriting information in the X-axis direction and the Y-axis direction in the output coordinate system is converted into an acceleration signal when the axes of the acceleration sensor and the coordinate axis of the output coordinate system match, and the converted acceleration signal is integrated twice. Handwriting input pen device characterized by obtaining 2. The first and second acceleration sensors are provided so as to be perpendicular to the axial direction of the input pen and orthogonal to each other, and the coordinate calculation device integrates the acceleration signals from these acceleration sensors twice, In a handwriting input pen device that obtains handwriting information in the X-axis direction and the Y-axis direction in an output coordinate system, a third acceleration sensor parallel to the axial direction of the input pen is provided, and locus information in each direction is also set as an operation mode. In addition to the mode for obtaining the correction value, a correction value acquisition mode is provided, and in the correction value acquisition mode, the coordinate calculation device
Correction related to the angular deviation between the axes of the first and second acceleration sensors and the coordinate axes of the output coordinate system based on the acceleration signals from the three acceleration sensors when writing a straight line in the axis or Y-axis direction In a mode in which a value is obtained and stored, and trajectory information in each direction is obtained, the coordinate calculation device calculates acceleration signals from the first and second acceleration sensors based on the stored correction values. Converting to an acceleration signal when the sensor axis and the coordinate axis of the output coordinate system match, and integrating the converted acceleration signal twice to obtain handwriting information in the X-axis direction and the Y-axis direction in the output coordinate system. Handwriting input pen device featuring. 3. The first and second acceleration sensors are provided so as to be perpendicular to the axial direction of the input pen and orthogonal to each other, and the coordinate calculation device integrates the acceleration signals from these acceleration sensors twice, In a handwriting input pen device that obtains handwriting information in the X-axis direction and the Y-axis direction in an output coordinate system, a third acceleration sensor parallel to the axial direction of the input pen is provided, and locus information in each direction is also set as an operation mode. In addition to the mode for obtaining the correction value, a correction value acquisition mode is provided, and in the correction value acquisition mode, the coordinate calculation device
Correction related to the angular deviation between the axes of the first and second acceleration sensors and the coordinate axes of the output coordinate system based on the acceleration signals from the three acceleration sensors when writing a straight line in the axis or Y-axis direction In the mode in which the value is obtained and stored and the trajectory information in each direction is obtained, the coordinate calculation device obtains the change in the inclination angle of the input pen accompanying the vertical writing based on the acceleration signal from the third acceleration sensor. From the obtained inclination angle change and the correction value stored in the correction value acquisition mode, the acceleration signals from the first and second acceleration sensors are converted into the axes of these acceleration sensors and the coordinate axes of the output coordinate system. A handwriting input pen device, characterized by converting to an acceleration signal when they match and integrating the converted acceleration signal twice to obtain handwriting information in the X-axis direction and the Y-axis direction in the output coordinate system.