Calibration device and calibration method

Abstract

To reduce a burden on a user required for calibration.SOLUTION: A calibration device for calibrating a detection value of a sensor 1 attached to a body M includes a light receiving unit 3 disposed at a limb (first part) of the body M and configured to receive a light beam L having directivity incident at a predetermined angle from a trunk (second part) of the body M different from the first part, and calibration means 4 configured to calibrate the detection value of the sensor 1 based on position information of the light receiving unit 3 when the light receiving unit 3 receives the light beam L. Even if the user does not take a reference posture every time a predetermined time elapses, the calibration is automatically performed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a calibration device and a calibration method used, for example, in motion capture. [Background technology]

[0002] As an example of so-called inertial motion capture technology, Patent Document 1 describes a technology in which the orientation of an inertial measurement sensor can be calibrated based on the orientation of a position estimation sensor by having the object to be measured assume a specific pose (such as bending and stretching or standing up), thereby instantly aligning the orientations of the position estimation sensor and the inertial measurement sensor.

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-133212 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional calibration requires the user to assume a predetermined calibration posture (hereinafter referred to as the reference posture), which places a burden on the user. In light of this, an object of the present invention is to provide a calibration device and a calibration method that can reduce the burden on the user required for calibration. [Means for solving the problem]

[0005] The calibration device of the present invention is a calibration device that calibrates the detection value of a sensor attached to the body, and includes a light receiving unit that is placed on a first part of the body and receives directional light rays that are incident at a predetermined angle from a second part of the body different from the first part, and calibration means that calibrates the detection value of the sensor based on position information of the light receiving unit when the light receiving unit receives the light rays.

[0006] Furthermore, a calibration method according to the present invention is a calibration method for calibrating the detection value of a sensor attached to the body, in which a light receiving unit is disposed on a first part of the body, the light receiving unit receiving directional light rays incident at a predetermined angle from a second part of the body different from the first part, and the detection value of the sensor is calibrated based on position information of the light receiving unit at the time the light receiving unit receives the light rays. [Effects of the Invention]

[0007] According to the present invention, the burden on the user required for calibration can be reduced. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 illustrates a motion capture system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing a schematic structure of a light receiving unit. [Figure 3] FIG. 1 is a diagram illustrating a schematic configuration of a measurement device. [Figure 4] 4 is a flowchart showing a process in the control unit shown in FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a diagram showing an outline of a motion capture system to which the present invention is applied. This motion capture system measures the movement of a user's body M to be captured, and includes a plurality of inertial measurement sensors 1 (shown by white circles in Fig. 1) attached to essential parts of the body M, such as multiple locations corresponding to the bones and joints of a skeletal model, a plurality of light-emitting units 2, a plurality of light-receiving units 3, and a measurement device 4 that wirelessly acquires sensor signals from the plurality of inertial measurement sensors 1 and the plurality of light-receiving units 3.

[0010] The inertial measurement sensor 1 is, for example, a 6-axis IMU (Inertial Measurement Unit) that detects 3-axis acceleration and 3-axis angular velocity, or a 9-axis IMU that detects 3-axis geomagnetism in addition to acceleration and angular velocity, and wirelessly transmits each of the detected data (detected values) to the measurement device 4 as a sensor signal. Note that the inertial measurement sensor 1 may also be a 3-axis IMU. Furthermore, if the inertial measurement sensor 1 is provided in a motion sensor suit worn on the body M, the respective detected values ​​may be transmitted collectively to the measurement device 4 via a repeater. In the illustrated example, the inertial measurement sensors 1 are respectively positioned on the left and right shoulders, left and right elbows, left and right wrists, waist, left and right thighs, left and right knees, and left and right ankles of the body M.

[0011] The light-emitting units 2 are attached to two locations on the left and right sides of the waist of the body M, and two locations on the front of the waist above the left and right legs. Each light-emitting unit 2 has a light-emitting element that emits directional light beams L, such as laser beams, an electronic circuit that drives the light-emitting element, and a battery, and emits the light beams L in four directions: left and right from the waist and toward the left and right ankles. The light beams L need only be directional, and may be colored, such as red or blue-purple, i.e., visible light, or colorless, i.e., invisible light, such as infrared light.

[0012] The light-receiving units 3 are attached to four locations on the limbs of the body M: both wrists and both ankles. Each light-receiving unit 3 forms a photoelectric switch together with one light-emitting unit 2 attached to a corresponding location on the waist of the body M. That is, the light-receiving unit 3 attached to the left wrist forms a photoelectric switch together with the light-emitting unit 2 attached to the left side of the waist, and the light-receiving unit 3 attached to the right wrist forms a photoelectric switch together with the light-emitting unit 2 attached to the right side of the waist. Similarly, the light-receiving unit 3 attached to the left ankle forms a photoelectric switch together with the light-emitting unit 2 attached to the front of the waist above the left leg, and the light-receiving unit 3 attached to the right ankle forms a photoelectric switch together with the light-emitting unit 2 attached to the front of the waist above the right leg. When each light-receiving unit 3 receives light rays L from the light-emitting unit 2 attached to the corresponding location, it transmits a switch signal informing the measurement device 4 together with identification information used to distinguish between itself and the other light-receiving units 3.

[0013] Each light-receiving unit 3 is configured to receive light ray L only when the incident angle of the light ray L emitted by the corresponding light-emitting unit 2 is a predetermined angle. FIG. 2 shows a schematic structure of the light-receiving unit 3. The light-receiving unit 3 includes a case 31 and a light-receiving element 32 housed within the case 31. The case 31 has a hole 33 with a uniform cross section, the bottom of which is the light-receiving surface of the light-receiving element 32, and the hole 33 opens toward the outside. This hole 33 allows the light-receiving element 32 to receive the light ray L only when the light ray L is incident at a predetermined angle. This hole 33 is an incidence restricting portion that restricts the incident angle of the light ray L that can be received by the light-receiving element 32 to the predetermined angle. Note that the predetermined angle is within a predetermined, very small angle θ, and this angle range is a design tolerance determined depending on the application of the movement measurement results, etc. For example, if the limbs of a user's avatar displayed on a screen are moved based on the measurement results, this is an angle range that allows the relative positions of the user's actual limbs to be reflected in the relative positions of the avatar's limbs without creating a sense of discomfort.

[0014] The measurement device 4 includes a communication unit 41, a control unit 42, an input / output unit 43, and a memory unit 44, as well as a power supply unit 45 that supplies operating power to these units. The measurement device 4 communicates with the inertial measurement sensors 1 and each light-receiving unit 3 via the communication unit 41. The control unit 42 measures the movement of the body M based on the sensor signals received from each inertial measurement sensor 1. Specifically, the control unit 42 calculates the velocity and angle from the detected values ​​(acceleration and angular velocity) of each inertial measurement sensor 1, thereby acquiring the movement of each part of the body M to which each inertial measurement sensor 1 is attached as numerical data. The control unit 42 also calibrates each inertial measurement sensor 1 as needed. Specifically, the control unit 42 sets (resets) the detected values ​​(acceleration and angular velocity) of each inertial measurement sensor 1 to 0 as the values ​​when the user is in the reference posture. The input / output unit 43 is a user interface used for operating the measurement device 4. The memory unit 44 stores various data input from the input / output unit 43 and numerical data acquired by the control unit 42.

[0015] Here, the measurement device 4 is realized by various information processing devices, such as various PCs, smartphones, VR goggles, etc., capable of data communication between the inertial measurement sensor 1 and each light-receiving unit 3. In this case, the memory unit 44 is realized by any storage medium, such as ROM or RAM, provided in the information processing device. The control unit 42 is realized, for example, by a CPU or the like provided in the information processing device executing predetermined processing in accordance with a program pre-stored in the storage medium, i.e., a program used for motion capture. The input / output unit 43 is realized by input devices such as a keyboard or switches, and various display devices or touch panels. Note that, if the measurement device 4 is, for example, a device dedicated to motion capture, the control unit 42 may be configured to be realized by hardware.

[0016] In this embodiment configured as described above, the following preparations are made before measuring the movement of the user's body M. Specifically, the measurement device 4 stores position information indicating the position of each light-receiving unit 3 on the body M, linked to the respective identification information. Furthermore, the orientation of each light-receiving unit 3 is set so that it can receive the light beam L from the corresponding light-emitting unit 2 when the user is in a reference posture. For this operation, for example, a preparation mode may be set in advance as an operating mode in the measurement device 4. While the preparation mode is set, the control unit 42 of the measurement device 4, upon receiving a switch signal from a light-receiving unit 3 that has received the light beam L, causes the input / output unit 43 to display the identification information (e.g., unit number) of the light-receiving unit 3 and a display indicating the light-receiving state. Therefore, the orientation of each light-receiving unit 3 can be easily adjusted by performing the operation with each light-emitting unit 2 turned on.

[0017] Next, after the above preparations have been made, a preset measurement mode is set in the measurement device 4, and the measurement device 4 starts measuring the movement of the body M. During this time, in the measurement device 4, the control unit 42 receives detection values ​​from each inertial measurement sensor 1 at a predetermined reception rate, and obtains data indicating the movement of the main parts of the body M based on the received detection values.

[0018] Meanwhile, in parallel with this, the control unit 42 performs the process shown in Fig. 4. That is, the control unit 42 checks whether or not a switch signal has been received from each light-receiving unit, thereby checking whether or not the light ray L has been received by any of the light-receiving units 3 (step S1). Here, if reception of the light ray L cannot be confirmed (step S1: NO), the control unit 42 does not perform the subsequent process. As a result, the detection values ​​of each inertial measurement sensor 1 are used as they are to acquire data indicating the movement of the main parts of the body M.

[0019] On the other hand, if reception of light ray L is confirmed (step S1: YES), this triggers the control unit 42 to first identify the light receiving unit 3 that received light ray L based on the identification number included in the switch signal, and then identify the inertial measurement sensor 1 closest to that light receiving unit 3 (step S2). At this time, for example, if the light receiving unit 3 that received light ray L was worn on the left wrist, the inertial measurement sensor 1 closest to the left wrist, or in the example shown in Figure 1, the inertial measurement sensor 1 worn in the same position, is identified as the closest inertial measurement sensor 1.

[0020] The control unit 42 then performs calibration by setting (resetting) the detection value received at the next timing from the identified inertial measurement sensor 1 to 0, assuming that the detection value is the value when the part of the body M on which the light receiving unit 3 identified by the identification number is attached is in the same position as when the user is in the reference posture (step S3). This eliminates measurement errors caused by drift due to temperature changes over time or due to body temperature, etc., for the part of the body M on which the light receiving unit 3 is attached, and enables accurate position measurement. Note that when this calibration process, i.e., calibration, is performed, the user may be notified by, for example, displaying a message or emitting an alarm.

[0021] As described above, in this embodiment, when any of the light-receiving units 3 receives a light ray L from the corresponding light-emitting unit 2, the inertial measurement sensor 1 attached to the position closest to that light-receiving unit 3 is identified at that timing based on the position information of the light-receiving unit 3 that received the light ray L, and the detection value of that inertial measurement sensor 1 is automatically calibrated. Therefore, while the movement of the user's body M is being measured, calibration is performed automatically without the user having to assume the reference posture, for example, every time a predetermined time has passed, thereby reducing the burden on the user required for calibration. Moreover, the user does not need to stop operation for calibration and can continue operation regardless of the execution of calibration.

[0022] 2, each light-receiving unit 3 is configured to include a hole 33 that functions as an incidence restricting portion that restricts the angle of incidence of light ray L that can be received by the light-receiving element 32 to a predetermined angle. Therefore, by adjusting the orientation of the light-receiving unit 3 in advance, calibration can be performed at the correct timing without being erroneously performed when the part where the light-receiving unit 3 is attached is not in the same position as when the user is in the reference posture. In this embodiment, each light-receiving unit 3 is provided with a hole 33 whose bottom faces the light-receiving surface of the light-receiving element 32 and functions as an incidence restricting portion. However, for example, an optical system having a similar function may be provided on the incident surface side of the light-receiving element 32.

[0023] In this embodiment, the light-receiving units 3 are arranged on the limb side, and the light-emitting units 2 are arranged on the torso side. In other words, the light-receiving units 3 that notify the measurement device 4 of the timing of receiving the light beam L are arranged at areas where the user's movement M is measured, with a large amount of movement and a wide range of motion. Conversely, the light-emitting units 2 are arranged at areas where the user's movement M is measured, with a small amount of movement and a narrow range of motion. This eliminates a delay between the timing of receiving the light beam L by the light-receiving units 3 and the timing of calibrating the detection value of the inertial measurement sensor 1, enabling more appropriate calibration. Note that the positions of the light-receiving units 3 and the light-emitting units 2 may be reversed in the present invention. Even in this case, calibration is automatically performed while the movement of the user's body M is being measured, without the user having to assume the reference posture every predetermined time, thereby reducing the burden on the user required for calibration.

[0024] In this embodiment, the light-emitting units 2 are attached to two locations on the left and right sides of the waist of the body M and two locations on the front of the waist above the left and right legs, respectively, and the light-receiving units 3 are attached to four locations on the limbs of the body M: the left and right wrists and the ankles, respectively. In other words, four pairs of light-emitting units 2 and light-receiving units 3 are used. However, depending on the type of movement of the body M to be measured, any number of combinations can be used. The above-described effect can be achieved even when only one pair of the light-emitting unit 2 and the light-receiving unit 3 is used. Furthermore, the light-receiving unit 3 may be attached to the head in addition to the limbs of the body M, for example, in the form of a headband. In this case, the movement of the head in addition to the limbs can be measured as the movement of the user's body M. Naturally, if, for example, only the movement of the head is to be measured as the movement of the user's body M, the light-receiving unit 3 may be attached only to the head.

[0025] Furthermore, in this embodiment, the case where each light-emitting unit 2 is placed in a part (second part) of the body M different from the part (first part) of the body M where the corresponding light-receiving unit 3 is placed has been described. However, for example, the light-emitting unit 2 and the light-receiving unit 3 may be integrated and placed in the same part (first part) of the body M, while a prism or mirror that reflects the light emitted by the light-emitting unit 2 may be placed in another part (second part). However, it is less costly to separate each light-emitting unit 2 from each light-receiving unit 3 as in this embodiment.

[0026] Furthermore, in the present embodiment, the case where calibration is performed using only the timing at which the light receiving unit 3 receives the light ray L as a switch has been described, but calibration may also be performed at the following timings in addition to or separately from this. For example, it is possible to learn the movement habits (movement patterns) of the user's body M using machine learning such as deep learning, constantly predict the next movement based on the pattern of the previous movement, and perform calibration on the inertial measurement sensor 1 located near or at the same position as the light receiving unit 3 when it is determined that the predicted position of any part of the body M where any light receiving unit 3 is provided coincides with or is substantially the same as the position at which the light ray L can be received, even without actually receiving the light ray L.

[0027] The above describes the embodiments and modifications of the present invention, but the present invention is not limited to these and includes the inventions set forth in the claims and their equivalents. [Explanation of symbols]

[0028] 1...inertial measurement sensor, 2...light-emitting unit, 3...light-receiving unit, 4...measuring device, 31...case, 32...light-receiving element, 33...hole, 41...communication unit, 42...control unit, 43...input / output unit, 44...storage unit, 45...power supply unit, L...light beam, M...body

Claims

1. A calibration device for calibrating a detection value of a sensor attached to a body, a light receiving unit disposed on a first part of the body and configured to receive directional light rays incident at a predetermined angle from a second part of the body different from the first part; a calibration unit that calibrates the detection value of the sensor based on position information of the light receiving unit when the light receiving unit receives the light beam; A calibration device comprising:

2. 2. The calibration device according to claim 1, wherein a light emitting unit that emits the light beam is disposed in the second portion.

3. the light receiving unit includes a light receiving element that receives the light beam, and an incidence restricting unit that restricts the incidence angle of the light beam that can be received by the light receiving element to the predetermined angle.

3. The calibration device according to claim 1 or 2.

4. the first part is at least one of the limbs of the body, the second region is the torso of the body; 3. The calibration device according to claim 1 or 2.

5. the first parts are four parts of the body, i.e., both wrists and both ankles, and the light receiving units are disposed at the four parts, respectively; the second region is four regions, i.e., a region corresponding to a wrist and an ankle on the right side of the waist of the body and a region corresponding to a wrist and ankle on the left side of the waist, and the light-emitting unit is disposed at each of the four regions; 3. The calibration device according to claim 2.

6. A calibration method for calibrating a detection value of a sensor attached to a body, comprising: a light receiving unit is disposed on a first part of the body, the light receiving unit receiving directional light rays incident at a predetermined angle from a second part of the body different from the first part; calibrating the detection value of the sensor based on position information of the light receiving unit at the time when the light receiving unit receives the light beam; Calibration method.

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