KR102587998B1 - pressure sensor calibration method of an optical digital pen by use of tilt angle - Google Patents

Abstract

The present invention generally relates to pressure sensor correction technology for optical electronic pens. In particular, the present invention analyzes the light-receiving image obtained from the optical electronic pen to calculate the tilt angle of the electronic pen, and then corrects the sensitivity of the pressure sensor of the electronic pen according to the tilt angle, thereby improving the user's convenience in using the electronic pen. This is about pressure sensor correction technology for optical electronic pens based on tilt angle. According to the present invention, the user can use the optical electronic pen with a consistent feel, which has the advantage of improving the convenience of use of the optical electronic pen.

Description

Pressure sensor calibration method of an optical electronic pen based on tilt angle {pressure sensor calibration method of an optical digital pen by use of tilt angle}

The present invention generally relates to pressure sensor correction technology for optical electronic pens.

In particular, the present invention analyzes the light-receiving image obtained from the optical electronic pen to calculate the tilt angle of the electronic pen, and then corrects the sensitivity of the pressure sensor of the electronic pen according to the tilt angle, thereby improving the user's convenience in using the electronic pen. This is about pressure sensor correction technology for optical electronic pens based on tilt angle.

In general, electronic pens (smart pens, touch pens) are used to display the user's handwriting on electronic devices (e.g. laptop computers, smartphones, electronic whiteboards, etc.) and save them as files. As electronic pen functions are being applied to tablet PCs and laptop computers, and various electronic writing programs (apps) are also developing, interest in electronic pens for electronic devices is growing.

As electronic pen solutions, electromagnetic resonance type stylus pens and electrostatic type active pens are commonly used. However, it is difficult to secure performance with these technologies on displays larger than 10 inches. Additionally, since a two-dimensional sensor array must be installed on the display panel, manufacturing costs increase significantly as the display size increases, and it is difficult to respond to form factor changes (e.g. folding, rolling, sliding, etc.).

Accordingly, optical digital pens are being developed as pen solutions for electronic devices. Since the location code only needs to be formed by attaching a transparent film with a dot pattern to the display panel, there is little decrease in electronic pen performance or increase in manufacturing costs even when the display size increases, and it can also respond to changes in form factor.

[FIG. 1] and [FIG. 2] are general configuration diagrams of the optical electronic pen 10 and an optical electronic pen system using the same. Referring to [FIG. 2], the optical electronic pen system consists of an optical electronic pen 10 and a smart terminal device 30.

When writing on the display panel 20 while gripping the pen body 11, the pen tip 12 forms a motion trajectory in contact with the surface of the display panel 20. At this time, the display panel 20 may be made of various materials. It may be made of a common paper material, or it may be made of a liquid crystal display (LCD) or organic light emitting diode (OLED) device made of glass or reinforced plastic.

The electronic pen control member 14 can identify the contact between the electronic pen pen tip 12 and the display panel 20 using the pressure sensor 13 and recognizes the fact that the user is writing. Since the pressure sensor 13 is supported backwards by the pressure sensor support unit 13a, it can detect the pressure applied to the pen tip 12 when writing begins. When the electronic pen control member 14 identifies writing, it controls the IR light emitting unit 17 to emit light (e.g., infrared (IR) light) to the outer surface of the display panel 20 according to the movement of the pen tip 12. Let them investigate.

The light emitted by the IR light emitting unit 17 is reflected from the surface of the display panel 20, and the IR light receiving unit 16 receives the reflected light. A location code 21 is printed or displayed on the display panel 20. The location code 21 can be implemented as a dot pattern made according to special encoding rules.

When the IR light receiving unit 16 collects reflected light (IR reflected light), location code 21 information corresponding to the movement trace of the pen tip 12 is also acquired. The IR light receiving unit 16 may be composed of an IR filter unit 16a, a CMOS optical unit 16b, and an IR sensor unit 16c, and may further include a lens, etc. For example, the IR light receiving unit 16 may be implemented as an infrared camera module.

The coordinate calculation unit 14a of the electronic pen control member 14 analyzes the position code 21 acquired by the IR light receiving unit 16 and provides a series of coordinate information about the movement of the pen tip 12 on the display panel 20. Acquire. Coordinate information is transmitted to the terminal communication unit 31 of the smart terminal device 30 through the wireless communication unit 18.

The hardware control unit 14b of the electronic pen control member 14 controls the overall hardware of the optical electronic pen 10. Preferably, the IR light emitting unit 17 is controlled to turn on or off in response to pressure information transmitted from the pressure sensor 13. When pressure is detected, the IR light-emitting unit 17 is turned on, and when pressure is not detected, the IR light-emitting unit 17 is turned off.

The smart terminal device 30 receives a series of coordinate information from the electronic pen 10 through the terminal communication unit 31, and the trajectory calculation unit 32a of the terminal control unit 32 determines the pen tip based on the series of coordinate information. 12) Calculate the movement trajectory. The trajectory display unit 32b of the terminal control unit 32 displays the movement trace of the pen tip 12 on the terminal panel unit 33. At this time, the terminal panel unit 33 is generally a display panel 20.

Since the optical electronic pen 10 is used by a person holding it in one's hand, ease of use is very important. Accordingly, the development of various technologies to improve the ease of use of the optical electronic pen 10 is required.

Republic of Korea Patent Publication No. 10-2017-0081302 “Electronic eraser, electronic pen that doubles as an eraser, medium with printed code” Republic of Korea Patent No. 10-0408518 (2003.11.24) “Computer electronic pen data input device and coordinate measurement method”

The purpose of the present invention is to provide a pressure sensor correction technology for a general optical electronic pen.

In particular, the purpose of the present invention is to improve the user's convenience in using the electronic pen by calculating the tilt angle of the electronic pen by analyzing the light-receiving image obtained from the optical electronic pen and then correcting the sensitivity of the pressure sensor of the electronic pen according to the tilt angle. The goal is to provide pressure sensor correction technology for optical electronic pens based on tilt angle.

The problem to be solved by the present invention is not limited to this matter, and other problems to be solved can be understood from the description in this specification.

In order to achieve the above object, the tilt angle-based pressure sensor calibration method of the optical electronic pen according to the present invention includes a first step of acquiring a light-receiving image of the optical electronic pen 10; A second step of calculating a tilt angle (θ) of the electronic pen corresponding to the degree of tilt of the optical electronic pen 10 by analyzing the light-receiving image; A third step of correcting the sensitivity of the pressure sensor 13 of the optical electronic pen 10 based on the electronic pen tilt angle θ may be configured to include.

In the present invention, the second step includes analyzing the light-receiving image to identify a plurality of virtual reference lines according to the graphic indicator format of the location code; Extracting the intersection angle between a plurality of reference lines (hereinafter referred to as 'reference line intersection angle'); It may be configured to include; calculating the electronic pen tilt angle (θ) in response to the reference line intersection angle.

In addition, the second step in the present invention includes storing a correlation table between the reference line intersection angle and the electronic pen tilt angle according to the graphic indicator format of the location code; Analyzing the light-receiving image to identify a plurality of virtual reference lines according to the graphic indicator format of the position code; Extracting the intersection angle between a plurality of reference lines (hereinafter referred to as 'reference line intersection angle'); Calculating the electronic pen tilt angle (θ) by querying the reference line intersection angle in a correlation table.

At this time, in the third step, the sensitivity of the pressure sensor 13 may be gradually increased from the default value to a preset standard in proportion as the electronic pen tilt angle θ progresses from 90 degrees to 0 degrees.

Additionally, in the third step, the sensitivity of the pressure sensor 13 may be changed and set to 'default value / cos (90 degrees - θ)' in response to the electronic pen tilt angle (θ).

In the present invention, a plurality of reference line intersection angles may be extracted from the light-receiving image, and a combination of the plurality of reference line intersection angles may be searched in a correlation table to calculate the electronic pen tilt angle (θ).

Meanwhile, the computer program according to the present invention is stored in a non-volatile storage medium in order to execute the above tilt angle-based pressure sensor correction method of the optical electronic pen on the computer.

According to the present invention, the user can use the optical electronic pen with a consistent feel, which has the advantage of improving the convenience of use of the optical electronic pen.

[Figure 1] is a general configuration diagram of an optical electronic pen.
[Figure 2] is a general configuration diagram of an optical electronic pen system.
[Figure 3] is a general configuration diagram of a position code pattern film for an optical electronic pen.
[Figure 4] is a general configuration diagram of a graphic indicator for an optical electronic pen.
[Figure 5] is a conceptual diagram of compensation processing for the pressure sensor of an optical electronic pen in the present invention.
[Figure 6] is an example of a light-receiving image acquired by an optical electronic pen.
[Figure 7] is a block diagram of the pressure sensor correction device according to the present invention.
[Figure 8] is a flowchart of the pressure sensor correction process of the tilt angle-based optical electronic pen according to the present invention.
[Figure 9] is an illustration of a reference line and its intersection angle in the present invention.
[Figure 10] is an example of the correlation between the reference line intersection angle and the electronic pen tilt angle in the present invention.
[Figure 11] is an example of the correlation between the force applied to the electronic pen and the pressure sensor output value.

Hereinafter, the present invention will be described in detail with reference to the drawings.

In describing the present invention, detailed descriptions of parts that overlap with the prior art may be omitted.

[Figure 3] is a general configuration diagram of the position code pattern film 40 for an optical electronic pen.

The location code pattern film 40 is a component that provides a location code 21 in the form of a dot pattern and is attached to the display panel 20. As shown in [Figure 3], the location code pattern film 40 includes a pattern layer 41, a diffusion layer 42, a protective layer 43, a blocking layer 44, an adhesive layer 45, and a light transmitting layer ( 46) may be included.

The pattern layer 41 is a layer on which a dot pattern such as [FIG. 4] is printed to implement the location code 21. Dot patterns are generally printed with infrared-absorbing ink made of phthalocyanine-based compounds, naphthalocyanine-based compounds, and amidium-based compounds.

The diffusion layer 42 is made of PET (PolyEthylene Terephthalate) material with an anti-glare coating and is a layer that improves the dot pattern recognition rate by absorbing part of the light emitted from the electronic device.

The protective layer 43 is made of PET or polycarbonate and is a layer that protects the location code pattern film 40.

The blocking layer 44 is a layer that improves the dot pattern recognition rate by reflecting about 10 to 35% of the light emitted from the electronic device.

The adhesive layer 45 is a layer that attaches the location code pattern film 40 to the front of the electronic device.

The light-transmitting layer 46 is made of an acrylic plate, a polycarbonate plate, a glass plate, etc., and is a layer that protects the display of the electronic device, strengthens its strength, and provides stable writing by the optical electronic pen 10.

[Figure 4] is a general configuration diagram of a graphic indicator 50 for an optical electronic pen.

A location code 21 is formed on the display panel 20 for the optical electronic pen. This location code 21 is implemented in the form of a dot pattern on the location code pattern film 40, and the dot pattern formed in a specific format is called a graphic indicator.

[FIG. 4] (a), a plurality of horizontal and vertical grid lines 51 and 52 are formed in the pattern layer 41, and a dot 54 is centered at the intersection 53 of these grid lines 51 and 52. It is formed spaced apart in four directions. The dot value is determined depending on the position where the dot 54 is formed around the intersection point 53, and the pattern of these dot values indicates the location information of the corresponding point. For example, the distance between the grid lines 51 and 52 is 250 to 300 ㎛, and the dots 54 have a diameter of 50 ㎛ and are formed at 1/8 to 1/4 of the grid spacing centered on the intersection 53. It can be.

[Figure 4] (b) shows an enlarged view of one grid. If the dot 54a is located on the right side of the intersection 53, the dot value is set to "1", and if the dot 54b is located above the intersection 53, the dot value is set to "2", and the dot 54c is located at the intersection point 53. If the dot (54d) is located to the left of (53), the dot value can be determined as "3", and if the dot (54d) is located below the intersection (53), the dot value can be determined as "4". At this time, the dot value may be determined differently depending on whether the dot 54a is formed at 1/8 or 1/4 of the intersection point 53. Additionally, the dots 54 may be formed diagonally around the intersection 53, and the dot values may be determined differently depending on each diagonal direction. Location information, for example, x-coordinates and y-coordinates, can be provided by combining the dot values determined in this way.

[Figure 5] is a conceptual diagram of correction processing for the pressure sensor 13 of an optical electronic pen in the present invention.

The user generally holds the electronic pen 10 in his hand and writes with it slightly tilted. In this specification, the angle between the bottom surface 22 of the display panel 20 and the longitudinal axis of the pen tip 12 is referred to as 'tilt angle (θ)', which means that the user tilts the electronic pen 10. It indicates the degree. When the electronic pen 10 is used upright, the tilt angle θ is 90 degrees. As the electronic pen 10 is tilted, the tilt angle θ becomes smaller.

However, as you tilt the electronic pen 10, you have to press the bottom surface 22 harder to write. When the electronic pen (10) is upright, writing is possible by lightly pressing the bottom surface (22). However, when the tilt angle is about 40 degrees, the electronic pen (10) must be pressed a little harder on the bottom surface (22) for writing to work. .

The electronic pen control member 14 identifies whether there is contact between the pen tip 12 and the bottom surface 22 using the pressure sensor 13 and determines whether the user has started writing or finished writing through this. When it is determined that writing has begun, the electronic pen control member 14 controls the IR light emitting unit 17 to turn on, and when it is determined that writing has ended, the electronic pen control member 14 controls the IR light emitting unit 17. Controls turn-off.

When the force with which the user presses the bottom surface 22 with the electronic pen 10 is F1, the force F2 with which the pen tip 12 presses the pressure sensor 13 is affected by the tilt angle θ. Approximately, F2 can be expressed as 'F1 x cos(90 degrees - θ)'.

When the electronic pen 10 is uprighted and the tilt angle θ is 90 degrees, the force F1 with which the electronic pen 10 presses the bottom surface 22 is fully applied to the pressure sensor 13. On the other hand, as the electronic pen 10 is tilted and the tilt angle θ becomes smaller, only a smaller portion of F1 is applied to the pressure sensor 13. For example, when the tilt angle (θ) is 40 degrees, only 64 percent of F1 is applied to the pressure sensor 13. In this case, compared to the state in which the electronic pen 10 is upright, the user must press the bottom surface 22 with the electronic pen 10 about 1.5 times harder to turn on the IR light emitting unit 17.

In the present invention, the tilt angle (θ) of the electronic pen 10 is calculated, and the sensitivity of the pressure sensor 13 is corrected accordingly.

In the above example, when the tilt angle (θ) is 90 degrees, the force F1 with which the electronic pen 10 presses the bottom surface 22 is fully applied to the pressure sensor 13, so the sensitivity of the pressure sensor 13 is set to the default value. ). When the tilt angle (θ) is 40 degrees, only 64 percent of the force F1 with which the electronic pen 10 presses the bottom surface 22 is applied to the pressure sensor 13, thereby increasing the sensitivity of the pressure sensor 13 by 56 percent. Increasing the sensitivity of the pressure sensor 13 by 56 percent corresponds to the pressure sensor 13 handling F2 multiplied by 1.56.

In this way, the sensitivity of the pressure sensor 13 increases incrementally in proportion as the tilt angle θ of the electronic pen 10 progresses from 90 degrees to 0 degrees. Approximately, the sensitivity of the pressure sensor 13 can be set to 'default value / cos (90 degrees - θ)'. At this time, when the tilt angle θ becomes 0 degrees when the electronic pen 10 is completely lying down, mathematically, the denominator becomes 0 and an error occurs in which the sensitivity of the pressure sensor 13 becomes infinite. To prevent this problem, it is desirable to set a specific upper limit for the sensitivity of the pressure sensor 13.

In the present invention, the electronic pen tilt angle (θ) is calculated by analyzing the light-receiving image obtained from the IR light-receiving unit 16 of the optical electronic pen 10.

The IR light receiving unit 16 of the optical electronic pen 10 recognizes the surface of the display panel 20 as having a shape close to an acute trapezoid. The farther away from the IR light receiving unit 16, the shorter the image is expressed in the light receiving image. This phenomenon becomes worse as the user tilts the electronic pen, which means that the light-receiving image becomes distorted.

[Figure 6] is an example of a light-receiving image acquired by an optical electronic pen. When the tilt angle is close to 90 degrees, a light-receiving image is obtained similar to the graphic indicator format of [FIG. 4], as shown in (a) of [FIG. 6]. However, as the tilt angle becomes smaller, the distortion of the light-receiving image becomes more severe, as shown in [Figure 6] (b).

[Figure 7] is a block diagram of the pressure sensor correction device 300 according to the present invention.

Referring to [Figure 7], the pressure sensor correction device 300 according to the present invention includes a light-receiving image temporary storage unit 310, a reference line identification unit 320, a line intersection angle extraction unit 330, and an electronic pen tilt angle. It is comprised of a calculation unit 340 and a pressure sensor sensitivity correction unit 350.

The pressure sensor correction device 300 is generally implemented in the electronic pen control member 14 of the optical electronic pen 10, but depending on the embodiment, it may be implemented in the terminal control unit 32 of the smart terminal device 30. there is.

The light-receiving image temporary storage unit 310 is a component that temporarily stores the light-receiving image acquired by the IR light-receiving unit 16 in memory for image analysis.

The reference line identification unit 320 is a component that analyzes the light-receiving image stored in the light-receiving image temporary storage unit 310 and identifies a plurality of virtual reference lines according to the graphic indicator format of the position code.

The line intersection angle extraction unit 330 is a component that extracts the intersection angle between the reference lines identified by the reference line identification unit 320, that is, the reference line intersection angle.

The electronic pen tilt angle calculation unit 340 is a component that calculates the electronic pen tilt angle (θ) based on the reference line intersection angle extracted by the line intersection angle extraction unit 330. At this time, the correlation between the reference line intersection angle and the electronic pen tilt angle (θ) can be known in advance by the graphic indicator format of the position code.

The pressure sensor sensitivity correction unit 350 corrects the sensitivity of the pressure sensor 13 as described above with reference to [FIG. 5] according to the electronic pen tilt angle θ obtained by the electronic pen tilt angle calculation unit 340. It is a component that does this. Preferably, the sensitivity of the pressure sensor 13 increases in proportion as the electronic pen tilt angle θ progresses from 90 degrees to 0 degrees.

[Figure 8] is a flow chart of the pressure sensor correction process of the tilt angle-based optical electronic pen according to the present invention.

Step (S100): First, the pressure sensor correction device 300 acquires a light-receiving image of the optical electronic pen 10. For example, an infrared photographed image generated by the IR light receiving unit 16 of the optical electronic pen 10 is provided.

Step (S110): Next, the pressure sensor correction device 300 analyzes the light-receiving image and calculates the electronic pen tilt angle θ corresponding to the degree of tilt of the optical electronic pen 10.

In the present invention, a first embodiment of calculating the electronic pen tilt angle (θ) will be described.

First, the light-receiving image is analyzed to identify a plurality of virtual reference lines according to the graphic indicator format of the location code, and the intersection angle between these reference lines, that is, the 'reference line intersection angle', is extracted.

The location code 21 formed on the display panel 20 for the optical electronic pen 10 has a dot pattern formed (printed) in a specific format. According to the graphic indicator format, several virtual reference lines (baselines) are defined for reading location codes.

These virtual reference lines are identified through image analysis of the light-receiving image, and the intersection angle between these reference lines is extracted.

[Figure 9] is an exemplary diagram of a reference line and its intersection angle in the present invention. [FIG. 9] As shown in (a) to (c), virtual reference lines set in the dot pattern are identified, and the intersection angle between them is extracted. These reference line intersection angles appear differently depending on the tilt angle. Although the reference line is set according to a single graphic indicator format, the degree of distortion is reflected differently depending on the degree of inclination of the electronic pen 10.

Accordingly, the electronic pen tilt angle (θ) is calculated in response to the reference line intersection angle. Referring to [FIG. 9], if the reference line intersection angle is 36 degrees and 37 degrees, the electronic pen tilt angle (θ) is calculated to be 43 degrees. Similarly, if the reference line intersection angle is 40 degrees and 43 degrees, the electronic pen tilt angle (θ) is calculated to be 60 degrees, and if the reference line intersection angle is 43 degrees and 45 degrees, the electronic pen tilt angle (θ) is calculated to be 70 degrees.

At this time, in order to improve the reliability of the calculation result of the electronic pen tilt angle (θ), a plurality of reference line intersection angles (e.g., 36 degrees, 37 degrees) are extracted from the light-receiving image, and the electronic pen is calculated from the combination of these reference line intersection angles. It is desirable to configure it to calculate the tilt angle (θ).

In the present invention, a second embodiment of calculating the electronic pen tilt angle (θ) is described. Detailed descriptions of parts that overlap with the first embodiment described above may be omitted.

First, a correlation table is stored between the reference line intersection angle and the electronic pen tilt angle (θ) according to the graphic indicator format of the position code. [Figure 10] is an example of the correlation between the reference line intersection angle and the electronic pen tilt angle (θ) in the present invention. The relationship between the reference line intersection angle and the electronic pen tilt angle (θ) can be known in advance by the graphic indicator format of the position code, so it is organized in a table and stored in advance.

The light-receiving image is analyzed to identify a plurality of virtual reference lines according to the graphic indicator format of the position code, and the intersection angle between these reference lines (reference line intersection angle) is extracted. Then, the reference line intersection angle is checked in the correlation table to calculate the electronic pen tilt angle (θ).

At this time, in order to improve the reliability of the calculation result of the electronic pen tilt angle (θ), a plurality of reference line intersection angles (e.g., 36 degrees, 37 degrees) are extracted from the light-receiving image, and the combination of these reference line intersection angles is correlated. It is desirable to configure it to calculate the electronic pen tilt angle (θ) by checking the table.

Step (S120): Next, as described above with reference to [FIG. 5], the pressure sensor correction device 300 adjusts the pressure sensor 13 of the optical electronic pen 10 based on the electronic pen tilt angle θ. Correct the sensitivity. The sensitivity of the pressure sensor 13 is gradually increased in proportion as the tilt angle θ of the electronic pen 10 progresses from 90 degrees to 0 degrees. Approximately, the sensitivity of the pressure sensor 13 can be set to 'default value / cos (90 degrees - θ)'.

[FIG. 11] is an example of the correlation between the force F1 pressing the bottom surface 22 with the electronic pen 10 and the output value of the pressure sensor 13. [Figure 11] shows the results obtained through experiments by the inventor of the present invention. Referring to [FIG. 11], even if the user holds the Zenza pen 10 and presses the bottom surface 22 with the same force (F1), the output value of the pressure sensor 13 gradually decreases as the tilt angle (θ) decreases. can confirm. Because of this, the more the electronic pen 10 is tilted, the more the user feels as if the electronic pen 10 must be pressed harder to operate.

According to the present invention, by calculating the tilt angle (θ) of the electronic pen and correcting the difference in sensitivity of the pressure sensor 13 as shown in [FIG. 11], the user can use the optical electronic pen 10 with the same feeling no matter how much it is tilted. becomes available.

Meanwhile, the present invention can be implemented in the form of computer-readable code on a computer-readable non-volatile recording medium. These non-volatile recording media include various types of storage devices, such as hard disks, SSDs, CD-ROMs, NAS, magnetic tapes, web disks, and cloud disks. Additionally, the present invention may be implemented in the form of a computer program stored on a medium in order to execute a specific procedure in combination with hardware.

Claims (7)

A first step of acquiring a light-receiving image of the optical electronic pen 10;
a second step of analyzing the light-receiving image to calculate a tilt angle (θ) of the electronic pen corresponding to the degree of tilt of the optical electronic pen (10);
A third step of correcting the sensitivity of the pressure sensor 13 of the optical electronic pen 10 based on the electronic pen tilt angle θ;
A pressure sensor correction method for an optical electronic pen based on tilt angle, including:
In claim 1,
The second step is,
Analyzing the light-receiving image to identify a plurality of virtual reference lines according to a graphic indicator format of the location code;
extracting an intersection angle between the plurality of reference lines (hereinafter referred to as 'reference line intersection angle');
calculating an electronic pen tilt angle (θ) in response to the reference line intersection angle;
A pressure sensor correction method for a tilt angle-based optical electronic pen, comprising:
In claim 1,
The second step is,
Storing a correlation table between the intersection angle between virtual reference lines and the electronic pen tilt angle according to the graphic indicator format of the position code;
Analyzing the light-receiving image to identify a plurality of virtual reference lines according to a graphic indicator format of the location code;
extracting an intersection angle between the plurality of reference lines (hereinafter referred to as 'reference line intersection angle');
calculating the electronic pen tilt angle (θ) by querying the reference line intersection angle in the correlation table;
A pressure sensor correction method for a tilt angle-based optical electronic pen, comprising:
In claim 1,
In the third step, the sensitivity of the pressure sensor 13 is gradually increased from the default value to a preset standard in proportion to the electronic pen tilt angle θ progressing from 90 degrees to 0 degrees. A pressure sensor correction method for an optical electronic pen based on tilt angle.

In claim 4,
Tilt angle, characterized in that in the third step, the sensitivity of the pressure sensor 13 is changed and set to 'default value / cos (90 degrees - θ)' in response to the electronic pen tilt angle (θ). A method of calibrating the pressure sensor of an optical electronic pen.
In claim 5,
The second step is,
Storing a correlation table between the intersection angle between virtual reference lines and the electronic pen tilt angle according to the graphic indicator format of the position code;
Analyzing the light-receiving image to identify a plurality of virtual reference lines according to a graphic indicator format of the location code;
extracting a plurality of intersection angles (hereinafter referred to as 'reference line intersection angles') between the plurality of reference lines;
Calculating an electronic pen tilt angle (θ) by querying the correlation table for a combination of the plurality of reference line intersection angles;
A pressure sensor correction method for a tilt angle-based optical electronic pen, comprising:
A computer program stored in a storage medium for executing the pressure sensor correction method of a tilt angle-based optical electronic pen according to any one of claims 1 to 6 on a computer.

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