A novel and cost-effective method for measuring the rotation angle of a collimator in all three axes.

Abstract

The present invention relates to the field of radiation-based imaging. In particular, the present invention relates to the field of X-ray collimation. To reduce the risk of mispositioning of the amplifier chamber, which may result in an extra dose to the patient, a rotation angle measuring device is provided for measuring the rotation angle of a rotatable X-ray collimator. The rotation angle measuring device comprises a resistance strip and a plunger. The resistance strip has an elongated tape attached to a first part of the rotatable X-ray collimator, and the longitudinal range (LA) of this elongated tape is arranged to curve about the rotation axis of the rotatable X-ray collimator. The plunger is attached to a second part of the X-ray collimator. The first and second parts are arranged to rotate relative to each other during the rotation of the X-ray collimator. The plunger is arranged to be in contact with the elongated strip so that the rotation of the rotatable X-ray collimator moves the elongated strip relative to the plunger, generating an electrical signal indicating the rotation angle of the rotatable X-ray collimator.

Description

[Technical Field]

[0001] The present invention relates to the field of radiation-based imaging. In particular, the present invention relates to the field of X-ray collimation, and more specifically, to a rotation angle measurement device, a rotation angle measurement system, a rotation angle measurement method, a computer program element, and a computer-readable storage medium. [Background Art]

[0002] A collimator is a main subcomponent in an X-ray system. The collimator adjusts the X-ray irradiation field to a range necessary for actual exposure. It also enables a user to perform this adjustment. The collimator provides optical simulation of the X-ray irradiation field. In clinical workflow scenarios, a user needs to rotate the collimator based on a patient's anatomy, and measurement of the rotation angle during rotation of the collimator is important to obtain correct on-screen Amplimat chamber visualization. [Summary of the Invention] [Problem to be Solved by the Invention]

[0003] Accordingly, there may be cases where a rotation angle measurement function is required. The object of the present invention is solved by the subject matter of the independent claims, and further embodiments are incorporated in the dependent claims. It is understood that the following aspects of the present invention apply equally to the rotation angle measurement device, the rotation angle measurement system, the rotation angle measurement method, the computer program element, and the computer-readable storage medium. Accordingly, any feature, function, step and / or element described below with reference to one aspect of the present disclosure applies equally to any other aspect of the present disclosure. [Means for Solving the Problem]

[0004] According to a first aspect of the present invention, a rotation angle measuring device is provided for measuring the rotation angle of a rotatable X-ray collimator. The rotation angle measuring device comprises a resistance strip and a plunger. The resistance strip has an elongated tape attached to a first portion of the rotatable X-ray collimator. The longitudinal portion of the elongated tape is arranged to curve about the rotation axis of the rotatable X-ray collimator. The plunger is attached to a second portion of the X-ray collimator. The first and second portions are arranged to rotate relative to each other during the rotation of the X-ray collimator. The plunger is arranged to contact the elongated strip such that the rotation of the rotatable X-ray collimator moves the elongated strip relative to the plunger, generating an electrical signal indicating the rotation angle of the rotatable X-ray collimator.

[0005] Accordingly, this disclosure proposes a rotational angle measuring device having a plunger and a resistance strip arranged in different parts of a rotatable X-ray collimator, namely a first part and a second part. The first and second parts are arranged to rotate relative to each other during the rotation of the X-ray collimator. For example, during the rotation of the rotatable X-ray collimator, the first part moves, i.e., rotates. The second part does not move, i.e., remains in its position. By pressing the plunger against the resistance strip, the resistance strip generates an electrical output, e.g., a voltage output. Depending on the rotational position of the plunger, the resistance strip outputs a corresponding electrical signal indicating the rotational angle of the rotatable X-ray collimator. The proposed rotational angle measuring device can be combined with any X-ray system that requires automatic collimation with a rotational angle measuring function. The proposed rotational angle measuring device can reduce the risk of incorrect amplimatt chamber positioning, which may result in unnecessary doses to the patient. The proposed rotational angle measuring device can also help improve optimal collimation and reduce unwanted radiation areas.

[0006] This will be explained in detail below, particularly with regard to the examples shown in Figures 3A, 3B, 4A, and 4B. Figure 5A shows an example of a plunger, and Figure 5B shows an example of a resistor strip.

[0007] According to an exemplary embodiment of the first aspect of the present invention, the plunger has either a spring-biased plunger or a pressure-biased plunger. This will be described in detail below, particularly with respect to the example shown in Figure 5A.

[0008] According to an exemplary embodiment of the first aspect of the present invention, the second part has a source alignment flange arranged to couple the X-ray collimator to an X-ray source.

[0009] This will be explained in detail below, particularly with regard to the examples shown in Figures 3A, 3B, 4A, and 4B.

[0010] According to an exemplary embodiment of the first aspect of the present invention, the first portion has a strip mounting support portion disposed opposite to the source alignment flange.

[0011] This will be explained in detail below, particularly with regard to the examples shown in Figures 3A, 3B, 4A, and 4B.

[0012] A second aspect of the present invention provides a rotation angle measuring system comprising a rotation angle measuring device according to the first aspect and any related example, and a processing device configured to determine the rotation angle of a rotatable X-ray collimator based on an electrical signal generated by the rotation angle measuring device.

[0013] This will be explained in detail below, particularly with regard to the example shown in Figure 6.

[0014] According to an exemplary embodiment of a second aspect of the present invention, the processing device is further configured to perform calibration of a rotation angle measuring device.

[0015] Therefore, it is possible to achieve feedback on the correct degree of rotation of the collimator.

[0016] This will be explained in detail below, particularly with regard to the example shown in Figure 6.

[0017] According to an exemplary embodiment of a second aspect of the present invention, the processing device is configured to perform multi-point calibration of a rotation angle measuring device.

[0018] Multi-point calibration can include 2-point calibration, 3-point calibration, 4-point calibration, and so on.

[0019] According to an exemplary embodiment of a second aspect of the present invention, the multipoint calibration includes a seven-point calibration having angular steps of -45°, -30°, -15°, 0°, 15°, 30°, and 45°.

[0020] According to a third aspect of the present invention, an X-ray collimator is provided having a rotation angle measuring device according to the first aspect and any related example, or a rotation angle measuring system according to the second aspect and any related example.

[0021] According to a fourth aspect of the present invention, a method for measuring the rotation angle of a rotatable X-ray collimator is provided. This method is A step of controlling a rotatable X-ray collimator to adjust the rotational position, The steps include obtaining an electrical signal from a rotation angle measuring device according to the first embodiment and any related example, A step of determining the rotation angle of the rotatable X-ray collimator based on the electrical signal. It holds.

[0022] This will be explained in detail below, particularly in relation to the flowchart shown in Figure 7.

[0023] According to an exemplary embodiment of a fourth aspect of the present invention, the method further comprises the step of performing a calibration of a rotation angle measuring device.

[0024] According to an exemplary embodiment of the fourth aspect of the present invention, the step of performing calibration of the rotation angle measurement device comprises performing multi-point calibration of the rotation angle measurement device.

[0025] According to an exemplary embodiment of the fourth aspect of the present invention, the multi-point calibration comprises 7-point calibration, and the 7-point calibration has angle steps of -45°, -30°, -15°, 0°, 15°, 30° and 45°.

[0026] According to another aspect of the present invention, there is provided a computer program product comprising instructions which, when the program is executed by a processor, cause the processor to perform the steps of the method according to the fourth aspect and any related examples. The computer program may comprise instructions which, when the program is executed by a computer, cause the computer to perform the method of any one of the above-described embodiments. Therefore, the computer program element may be stored in a computer unit, which is also part of an embodiment of the present invention. This computer unit may be adapted to perform or to induce the performance of the steps of the above-described method. The computer unit may be adapted to automatically operate and / or execute instructions from a user. The computer program may be loaded into a working memory of a data processor. Accordingly, the data processor may be equipped to perform the method of the present invention. This exemplary embodiment of the present invention includes both a computer program that uses the present invention from the outset, and a computer program that converts an existing program into a program that uses the present invention through an update. Furthermore, the computer program element can provide all the steps necessary to carry out the procedure of the exemplary embodiment of the above-described method.

[0027] According to a further aspect of the present invention, there is provided a computer-readable storage medium having a computer program stored thereon. The computer program may be stored and / or distributed on any suitable medium, for example an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, for example via the Internet or other wired or wireless telecommunication systems. However, the computer program may also be presented on a network such as the World Wide Web and downloaded from such a network into the working memory of a data processor. The computer-readable storage medium may comprise instructions which, when executed by a computer, cause the computer to perform the method of any one of the embodiments described herein.

[0028] It should be noted that embodiments of the present invention are described with reference to different subject-matters. In particular, some embodiments are described with reference to method-type claims, whereas other embodiments are described with reference to device-type claims. However, those skilled in the art will understand from the above and the following description that, unless otherwise stated, in addition to any combination of features belonging to one type of subject-matter, any combination of features relating to different subject-matters is also considered to be disclosed in the present application. However, combining all features can provide synergistic effects exceeding the simple sum of these features. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above-defined aspects and further aspects of the present invention will be apparent from and explained with reference to the exemplary embodiments described hereinafter. The present invention will be described in more detail hereinafter with reference to exemplary embodiments, but the present invention is not limited thereto. [Figure 1] Figure 1 shows an example of an X-ray collimator in an X-ray imaging apparatus. [Figure 2A] Figure 2A shows the X-ray collimator in a first angular position. [Figure 2B]Figure 2B shows the X-ray collimator at the second angular position. [Figure 3A] Figure 3A shows a perspective view of the X-ray collimator. [Figure 3B] Figure 3B shows a top view of the X-ray collimator. [Figure 4A] Figure 4A shows the X-ray collimator at the first angular position. [Figure 4B] Figure 4B shows the X-ray collimator at the second angular position. [Figure 5A] Figure 5A shows an example of a plunger. [Figure 5B] Figure 5B shows an example of a resistance strip. [Figure 6] Figure 6 shows an example of a rotation angle measurement system. [Figure 7] Figure 7 shows a flowchart illustrating the method for measuring the rotation angle. [Modes for carrying out the invention]

[0030] An X-ray collimator is a major subcomponent in an X-ray system. Figure 1 shows an example of an X-ray collimator 100 in an X-ray imaging device 200. The X-ray imaging device 200 has an X-ray source 110 and an X-ray detector 120. The X-ray source 110 and the X-ray collimator 100 are housed in a housing 130. As shown in Figure 1, before interaction with the collimator, the X-ray beam 140 emitted from the X-ray source 110 is a divergent beam. Therefore, without the X-ray collimator 100, the dimensions of the cross-section of the X-ray beam 140 when it reaches the X-ray detector 120 would be much larger than the area of ​​the desired region of interest (ROI), such as the patient's lungs in a "chest X-ray". The purpose of the X-ray collimator 100 is to limit the dimensions of the beam's cross-section and create a field of view 150 in which this beam cross-section matches the patient's ROI in terms of size and shape.

[0031] In many examinations, such as lateral chest examinations and orthopedic examinations, it is often necessary to rotate the collimator to reduce areas that are unnecessarily irradiated. This is done by manually rotating the collimator by a medical professional. A dosimetry device can be positioned between the X-ray detector 120 and the subject, which is an arrangement of multiple measurement areas, for example, five measurement areas. An example of a dosimetry device is an ionization chamber called an amplimatt chamber. A human operator can select some (or all) of the measurement areas before starting X-ray irradiation. Only this selected group of measurement areas is then used during subsequent X-ray irradiation of subjects to measure the radiation dose during actual X-ray irradiation. Inputting the rotation position of the collimator is crucial for proper display of the on-screen amplimatt chamber visualization. Figure 2A shows the X-ray collimator 100 at a 0-degree angular position in the correct amplimatt chamber position. At the indicated position, it is possible to measure the correct radiation dose during actual X-ray irradiation. However, if the X-ray collimator is at an angle other than 0 degrees and the system has not received any input regarding this, the system may assume that the collimator is at 0 degrees and control all functions if applicable. For example, Figure 2B shows that the X-ray collimator 100 is rotated 45 degrees around the rotation axis 160. This results in an incorrect amplifier chamber position, leading to inaccurate radiation dose measurements and potentially causing unnecessary doses to the patient during the examination.

[0032] To address the above issues, this disclosure proposes a rotation angle measuring device for performing the rotation angle measuring function of a collimator. An exemplary arrangement of the rotation angle measuring device on an X-ray collimator is shown in Figures 3A and 3B. As shown in both figures, the rotation angle measuring device 10 has a plunger 12 and a resistance strip 14.

[0033] Figure 3A shows a perspective view of the X-ray collimator 100. The X-ray collimator 100 includes a collimator assembly 20 and one or more adjustment knobs 30 for adjusting the shutter of the collimator assembly 20. Figure 3B shows a top view of the collimator assembly 20. In the example shown, the collimator assembly 20 includes a base 22 with an opening, a source alignment flange 40 used to couple the X-ray collimator to an X-ray source (e.g., an X-ray tube or tube assembly), and a shutter 50 for variably shielding X-ray radiation passing through the opening. In the example shown, the source alignment flange 40 is shown as a projection and a ring. In some other examples, the source alignment flange 40 may have a different shape that fits or couples to the X-ray source 110. In the example shown, a strip mounting support 60 is provided and positioned on the base 22 of the collimator assembly 20. Even if this strip mounting support 60 is shown as a projection and a semicircle, it is also understood that the source alignment flange 60 may have a different shape. The strip mounting support portion 60 is positioned opposite the source alignment flange 40. The inner surface of the strip mounting support portion 60 faces the source alignment flange 40 and is curved around the rotation axis 160 of the rotatable X-ray collimator 100.

[0034] The X-ray collimator 100 can rotate clockwise or counterclockwise. During rotation of the X-ray collimator, the source alignment flange 40 and the strip mounting support 60 rotate relative to each other. For example, Figure 4A shows the X-ray collimator 100 positioned in a first rotation position. In the first rotation position shown, the plunger 12 is in contact with the midpoint of the elongated tape of the resistance strip 14. This angular position may be defined as the 0-degree angular position. Figure 4B shows the X-ray collimator 100 moved to a second rotation position. As seen in Figure 4B, only the plunger 12 attached to the source alignment flange 40 moves, i.e., rotates. The strip mounting support 60 does not move, i.e., remains in its position. Therefore, during rotation of the X-ray collimator 100, the source alignment flange 40 and the strip mounting support 60 rotate relative to each other. This relative movement results in a change in the rotation position of the plunger 12 on the resistance strip 14. The rotation angle measuring device 10 then outputs an electrical signal, such as an analog voltage, indicating the rotation angle of the rotatable X-ray collimator.

[0035] Figure 5A shows an example of a plunger 12. In this example, the plunger 12 is a spring-biased plunger having a spring 11. However, it is understood that the plunger 12 may be of any form, for example, a pressure-biased plunger. The plunger 12 is a non-conductive mechanism. By pressing the plunger 12 against the resistance strip 14, the resistance strip 14 generates a desired electrical output.

[0036] Figure 5B shows an example of a resistance strip 14. In the example shown, the resistance strip 14 has an elongated tape 15 having an elongated region LA. The resistance strip 14 has an active region 17 made of a resistive material. The resistance strip 14 further has an electrical channel 19 configured to supply an electrical output. As an example, the electrical channel 19 may include two resistive output channels and one electrical collector channel. These two resistive circuits can be separated by laminating spacer adhesive, and contact between these two circuits occurs by pressure from a plunger to the upper circuit, which is pushed down until this upper circuit contacts the lower circuit, thereby producing a potential difference output in the form of a voltage divider.

[0037] To measure the rotation angle of the X-ray collimator, the resistance strip 14 is mounted on the inner surface of the strip mounting support 60, and the longitudinal range LA of the elongated tape is arranged to curve around the rotation axis of the rotatable X-ray collimator 100. Furthermore, the plunger 12 is positioned to contact the elongated strip so that the rotation of the rotatable X-ray collimator moves the elongated strip relative to the plunger, generating an electrical signal indicating the rotation angle of the rotatable X-ray collimator. Depending on the rotation position of the plunger, the resistance strip 14 outputs an analog voltage as the output of the voltage divider described above. This analog voltage signal is converted to a digital value by an analog-to-digital converter located, for example, in the collimator's microcontroller. From this digital voltage value, the equivalent collimator rotation angle is calculated, for example, in increments of 0.1 degrees, and transmitted to the system's software.

[0038] Figure 6 shows a rotation angle measurement system. This rotation angle measurement system includes the rotation angle measurement device 10 described above and a processing device 70 configured to acquire an electrical signal from the rotation angle measurement device and determine the rotation angle of a rotatable X-ray collimator based on this electrical signal.

[0039] A “processor” is an example of a processing device 70, which uses one or more microprocessors programmed to perform various functions described herein using software (e.g., microcode). The processing device may be implemented with or without a processor, or it may be implemented as a combination of dedicated hardware for performing some functions and a processor (e.g., one or more programmed microprocessors and associated circuits) for performing other functions. Examples of components of the device used in various embodiments of this disclosure include, but are not limited to, conventional microprocessors, application-specific integrated circuits (ASICs), and field-programmable gate arrays (FPGAs). In various embodiments, the processor may be associated with one or more storage media (commonly referred to herein as “memory,” e.g., volatile and non-volatile computer memory). In some embodiments, the storage media may be encoded with one or more programs that, when executed on one or more processors and / or controllers, perform at least some of the functions described herein. Various storage media may be mounted within a computing device, or they may be transportable so that one or more programs stored in the storage media can be loaded into a computing device and various embodiments of this disclosure described herein can be implemented. The terms “program” or “computer program” are used herein in a general sense and refer to any type of computer code (e.g., software or microcode) that can be used to program one or more processors. For example, a processing unit 70, or a portion of its components, may reside within a control panel operating as software routines. These components may be programmed in a suitable scientific computing platform, such as Matlab® or Simulink®, and then converted into C++ or C routines held in a library and linked when invoked by the control panel.

[0040] To achieve accurate collimator rotation angle feedback, the processing device 70 may be further configured to perform calibration of the rotation angle measuring device, for example, multi-point configuration of the rotation angle measuring device. As an example, to achieve rotation angle accuracy of + / -0.5 degrees, the resistance strip 14 installed in the collimator housing may be calibrated in seven steps, such as -45°, -30°, -15°, 0°, 15°, 30°, and 45°. At each of these angle steps, the corresponding digital value is stored in the collimator's microcontroller, and the result is stored in a lookup table. This lookup table helps to interpolate between angle values ​​with the required accuracy.

[0041] Figure 7 shows a flowchart illustrating a rotation angle measurement method 300 for measuring the rotation angle of a rotatable X-ray collimator. In block 310, the method 300 includes the step of controlling the rotatable X-ray collimator to adjust its rotational position. In block 320, the method 300 includes the step of obtaining an electrical signal from a rotation angle measurement device described herein. In block 330, the method 300 further includes the step of determining the rotation angle of the rotatable X-ray collimator based on the electrical signal.

[0042] In some embodiments, the method 300 may further include a step of performing a calibration of a rotational angle measuring device, such as a multi-point calibration of the rotational angle measuring device. For example, the multi-point calibration includes a seven-point calibration, the seven-point calibration having angle steps of -45°, -30°, -15°, 0°, 15°, 30°, and 45°.

[0043] In another exemplary embodiment of the present invention, a computer program or computer program element is provided, characterized by adapting the method steps of a method according to one of the embodiments described above to be performed on a suitable system.

[0044] Therefore, the computer program elements may be stored in a computer unit which is also part of an embodiment of the present invention. This computer unit may be adapted to perform or guide the execution of the steps of the method described above. Furthermore, this computer unit may be adapted to operate the components of the apparatus described above. The computer unit may be adapted to automatically operate and / or execute user instructions. The computer program may be loaded into the working memory of a data processor. Therefore, this data processor may be equipped to perform the method of the present invention.

[0045] This exemplary embodiment of the present invention includes both a computer program that uses the present invention from the outset and a computer program that, through an update, modifies an existing program to use the present invention.

[0046] Furthermore, computer program elements can provide all the steps necessary to carry out the procedures of the exemplary embodiment of the method described above.

[0047] According to a further exemplary embodiment of the present invention, a computer-readable medium such as a CD-ROM is provided, which stores the computer program elements described above.

[0048] Computer programs may be stored and / or distributed on suitable media such as optical storage media or solid-state media supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0049] However, computer programs can be presented on networks such as the World Wide Web and downloaded from such networks into the working memory of a data processor. According to a further exemplary embodiment of the present invention, a medium is provided that enables a computer program element to be downloaded, and this computer program element is configured to perform a method according to any of the embodiments of the present invention described above.

[0050] It should be noted that embodiments of the present invention are described with reference to different subject matter. In particular, some embodiments are described with reference to method-form claims, while others are described with reference to device-form claims. However, those skilled in the art will understand from the above and below descriptions that, unless otherwise specified, any combination of features belonging to a certain form of subject matter, as well as any combination of features relating to different subject matter, are also disclosed in this application. However, by combining all features, a synergistic effect greater than the simple sum of these features can be obtained.

[0051] Although the present invention is illustrated and described in detail in the drawings and the above description, such illustrations and descriptions should be considered illustrative or empirical and not limiting. The present invention is not limited to the disclosed embodiments. Other variations of the disclosed embodiments can be understood and practiced by those skilled in the art practicing the claimed invention from a consideration of the drawings, this disclosure and the dependent claims.

[0052] In the claims, the term “having” does not exclude other elements or steps, nor does it exclude the existence of multiple elements or steps even if it is not stated that there are multiple. A single processor or other unit may perform the functions of several of the items enumerated in the claims. The mere fact that certain means are enumerated in different dependent claims does not imply that combinations of these means cannot be used advantageously. No reference numeral in the claims should be construed as limiting its scope. [Explanation of Symbols]

[0053] 10 Rotation Angle Measuring Device 11 springs 12 plungers 14 Resistor strips 15. Long, thin tape 17 Active area 19 Electrical Channels 20 Collimator Assembly 30 Adjustment knobs 40. Source Alignment Flange 50 shutters 60 Strip mounting support section 70 Processing Devices 100 X-ray collimator 110 X-ray source 120 X-ray detectors 130 Housing 140 X-ray beam 150 field of view 160 Rotation axis 200 X-ray imaging device 300 Rotation Angle Measurement Method LA Long and narrow range

Claims

1. A rotation angle measuring device for measuring the rotation angle of a rotatable X-ray collimator, wherein the rotation angle measuring device is Plunger and, Resistor strip and It has, The resistance strip has an elongated tape attached to a first portion of the rotatable X-ray collimator, and the longitudinal portion of the elongated tape is arranged to curve around the rotation axis of the rotatable X-ray collimator. The plunger is attached to the second portion of the rotatable X-ray collimator, and the first portion and the second portion are arranged to rotate relative to each other during the rotation of the X-ray collimator. The plunger is positioned to contact the elongated resistance strip such that the rotation of the rotatable X-ray collimator moves the elongated resistance strip relative to the plunger and generates an electrical signal indicating the rotation angle of the rotatable X-ray collimator. Rotation angle measuring device.

2. The plunger is Spring-biased plunger, and Pressure-biased plunger A rotation angle measuring device according to claim 1, having one of the above.

3. The rotation angle measuring device according to claim 1 or 2, wherein the second part comprises a source alignment flange arranged to couple the X-ray collimator to an X-ray source.

4. The rotation angle measuring device according to claim 3, wherein the first portion has a strip mounting support portion disposed opposite to the radiation source alignment flange.

5. A rotation angle measuring device according to any one of claims 1 to 4, A processing device configured to determine the rotation angle of a rotatable X-ray collimator based on an electrical signal generated by the rotation angle measuring device, A rotation angle measuring system having the following features.

6. The rotation angle measuring system according to claim 5, wherein the processing device is further configured to perform calibration of the rotation angle measuring device.

7. The rotation angle measuring system according to claim 6, wherein the processing device is configured to perform multi-point calibration of the rotation angle measuring device.

8. The aforementioned multi-point calibration includes a seven-point calibration. The seven-point calibration has angular steps of -45°, -30°, -15°, 0°, 15°, 30°, and 45°. The rotation angle measuring system according to claim 7.

9. A rotation angle measuring device according to any one of claims 1 to 4, or Rotation angle measuring system according to any one of claims 5 to 8 An X-ray collimator having the following features.

10. A method for measuring the rotation angle of a rotatable X-ray collimator, The steps include controlling the rotatable X-ray collimator to adjust the rotational position, A step of acquiring an electrical signal from a rotation angle measuring device according to any one of claims 1 to 4, A step of determining the rotation angle of the rotatable X-ray collimator based on the electrical signal. A method for measuring rotational angle, comprising the following features.

11. The rotation angle measuring method according to claim 10, further comprising the step of performing calibration of the rotation angle measuring device.

12. The rotation angle measuring method according to claim 11, wherein the step of performing calibration of the rotation angle measuring device comprises performing multi-point calibration of the rotation angle measuring device.

13. The aforementioned multi-point calibration has seven-point calibration, The rotation angle measurement method according to claim 11, wherein the seven-point calibration has angle steps of -45°, -30°, -15°, 0°, 15°, 30°, and 45°.

14. A computer program element having an instruction that, when the program is executed by the processor, causes the processor to perform a step according to any one of claims 10 to 13.

15. A computer-readable storage medium storing the computer program elements described in claim 14.

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