Wearable devices

Abstract

To provide appropriate notification to individuals behind the user, tailored to their specific needs. [Solution] The wearable terminal 10 is worn by the user and monitors the area behind the user. The wearable terminal 10 includes a millimeter-wave sensor unit 13 that detects a person behind the user, a light-emitting unit 18 that notifies the person behind, a notification control means 114 that causes the light-emitting unit 18 to notify a warning level according to the detection status of the person behind, and a control means 11 that causes the notification means to notify a warning level according to the detection status of the person behind. The notification means includes a display means that displays a light or an image, and the control means causes the notification means to notify the notification in a display mode according to the warning level.

Description

Technical Field

[0001] The present invention relates to a technique for monitoring the rear of a user.

Background Art

[0002] Devices that are worn by a user and monitor the rear of the user are known (for example, Patent Documents 1 to 3).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of Invention

Problems to be Solved by the Invention

[0004] By issuing a notification that informs a person behind the user that the user is on alert, it can be expected to psychologically suppress stalking behavior. However, the persons present behind the user include not only stalkers and other tracking persons who intentionally track the user, but also persons who are merely moving in the same direction as the user. If the same notification is uniformly issued to all persons behind the user, there is a possibility of causing discomfort to persons who have no intention of tracking the user.

[0005] The present invention aims to issue an appropriate notification corresponding to a person present behind the user, in accordance with that person.

Means for Solving the Problems

[0006] One aspect of the present invention provides a wearable terminal that is worn by a user and monitors the area behind the user, comprising: detection means for detecting a person present behind the user; notification means for notifying the person behind the user; and control means for causing the notification means to notify the level of warning according to the detection status of the person behind the user.

[0007] The notification means includes a display means for emitting light or displaying an image, and the control means may cause the notification means to perform the notification in a display mode corresponding to the warning level.

[0008] The wearable terminal further comprises a suspiciousness calculation means for calculating the degree of suspiciousness of the person behind, and the control means may determine the warning level according to the degree of suspiciousness.

[0009] The wearable terminal further comprises a suspicious person detection means for determining whether the person behind it is a suspicious person, and the control means may determine the warning level according to the determination result of the suspicious person detection means.

[0010] The control means may cause the notification means to execute the notification on the condition that a specific operation is performed by the user.

[0011] The control means may cause the notification means to perform the notification according to the circumstances surrounding the user.

[0012] The wearable device may further include notification means for notifying the user of the detection status of the person behind them.

[0013] The notification means may provide notification based on a first condition regarding the detection status of the person behind, and the notification means may provide notification based on a second condition regarding the detection status of the person behind, which is different from the first condition. [Effects of the Invention]

[0014] According to the present invention, it is possible to perform appropriate notification corresponding to a person present behind a user. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] [Figure 1] A perspective view illustrating the external appearance of the wearable terminal according to the first embodiment. [Figure 2] A diagram illustrating the configuration of the wearable terminal according to the first embodiment. [Figure 3] A diagram illustrating a weighting table. [Figure 4] A flowchart showing the operation of the wearable terminal according to the first embodiment. [Figure 5] A diagram illustrating the configuration of the wearable terminal according to the second embodiment. [Figure 6] A flowchart showing the operation of the wearable terminal according to the second embodiment. [Figure 7] A diagram illustrating the configuration of a rear monitoring system according to a modification. DETAILED DESCRIPTION OF EMBODIMENTS

[0016] 1. First Embodiment (Configuration) FIG. 1 is a perspective view illustrating the external appearance of a wearable terminal 10 according to the first embodiment. The wearable terminal 10 is a shoulder-mounted type terminal that is worn on the user's shoulder. The wearable terminal 10 monitors the rear of the user, detects a suspicious tracker that tracks the user, and notifies the user. The tracker refers to a subject that moves along with the movement of the user and tracks the user.

[0017] The wearable terminal 10 is composed of a main body portion 10a positioned at the back of the neck, and arm portions 10b extending left and right from the main body portion 10a to be hung on the shoulders. The main body portion 10a has a curved shape so as to fit against the back of the neck. The arm portions 10b have a curved shape so as to be hung on the shoulders.

[0018] Figure 2 is a diagram illustrating the configuration of the wearable terminal 10 according to the first embodiment. The wearable terminal 10 includes a control unit 11, a storage unit 12, a plurality of millimeter wave sensor units 13, an Inertial Measurement Unit (IMU) 14, a communication unit 15, an output unit 16, an operation unit 17, and a light emitting unit 18. These components are connected via a bus.

[0019] The control unit 11 is a processor that controls the operation of the entire wearable terminal 10. The control unit 11 executes various processes by reading and executing programs stored in the storage unit 12. The control unit 11 includes, for example, one or a plurality of CPUs (Central Processing Units).

[0020] The storage unit 12 is a memory that stores programs executed by the control unit 11 and data required for processing. The storage unit 12 includes, for example, a ROM (Read Only Memory), a RAM (Random Access Memory), and a flash memory.

[0021] The millimeter wave sensor unit 13 uses millimeter waves to detect objects such as moving bodies (particularly persons behind the user) present around the user, and measures the distance between the detected object and the user. A moving body refers to a moving object, and includes persons and vehicles such as bicycles and motorcycles. It also includes flying objects such as drones. The millimeter wave sensor unit 13 includes, for example, a millimeter wave sensor and a dedicated processor. As shown in Figure 1, one millimeter wave sensor unit 13 is provided on each of the left and right sides of the main body 10a of the wearable terminal 10. Thereby, the millimeter wave sensor unit 13 can cover a wide range behind the user. The millimeter wave sensor unit 13 is an example of the "detection means" according to the present invention.

[0022] Specifically, the millimeter-wave sensor unit 13 first detects objects such as moving bodies present around the user. For example, the millimeter-wave sensor unit 13 uses a millimeter-wave sensor to transmit millimeter waves toward the user's rear and receives the reflected waves to detect objects behind the user. The horizontal field of view of each millimeter-wave sensor is, for example, 50° to 90°, and the detection distance is, for example, up to approximately 20m. As a result, the millimeter-wave sensor can detect a moving body approaching from behind the user at a speed of 20km / h 3 seconds before it reaches the user.

[0023] The millimeter-wave sensor may be a one-dimensional sensor that measures only distance and does not have angular resolution, or it may be a two-dimensional or three-dimensional sensor equipped with multiple transmitters and receivers.

[0024] The millimeter-wave sensor unit 13 can identify other moving objects moving at different speeds than the user by analyzing the Doppler shift of the reflected wave. For example, if the user is walking at 3 km / h, the millimeter-wave sensor unit 13 can identify other moving objects by considering reflections at the same speed as "self-reflection" and reflections at different speeds as "other-object reflection". In addition, the millimeter-wave sensor unit 13 can classify surrounding moving objects from environmental noise by analyzing the pattern of the reflected wave using AI (Artificial Intelligence).

[0025] When a moving object is detected, the millimeter-wave sensor unit 13 measures the distance between the detected moving object and the user at predetermined intervals. For example, the millimeter-wave sensor unit 13 uses a millimeter-wave sensor to transmit millimeter waves towards a moving object located behind the user, and measures the distance between the moving object and the user based on the time it takes to receive the reflected waves.

[0026] Furthermore, if the user wearing the wearable device 10 is moving, the distance measured by the millimeter-wave sensor unit 13 will include the influence of the user's movement. Therefore, the millimeter-wave sensor unit 13 may, for example, acquire the user's movement in real time based on the detection results of the inertial measurement unit 14, and then estimate and remove the influence of the user's movement from the distance measured by the millimeter-wave sensor unit 13 to correct for this influence.

[0027] In addition, the wearable terminal 10 is provided with a millimeter-wave sensor unit 13 for biometric use, separate from the millimeter-wave sensor unit 13 for distance measurement described above. The millimeter-wave sensor unit 13 for biometric use measures the user's biometric information. This biometric information includes respiratory rate and heart rate. The millimeter-wave sensor unit 13 for biometric use is positioned on the arm portion 10b of the wearable terminal 10, either at the apex near the user's carotid artery or at the tip near the user's chest. A person's chest displaces by a few millimeters with normal breathing and by several tens of microns with heartbeat. The millimeter-wave sensor unit 13 for biometric use can measure the user's respiratory rate and heart rate by detecting these minute displacements of the user's chest with a millimeter-wave sensor.

[0028] The inertial measurement unit 14 detects the user's movement state. The user's movement state refers to the state of the user's movement, including whether or not there is movement, the distance moved, and the direction of movement. The inertial measurement unit 14 includes, for example, an accelerometer, a gyroscope, and a dedicated processor. The accelerometer measures the acceleration of the wearable terminal 10 in three axes. The gyroscope measures the angular velocity of the wearable terminal 10 in three axes.

[0029] The inertial measurement unit 14 can detect whether or not the user is moving based on the change in acceleration measured by the acceleration sensor. Furthermore, the inertial measurement unit 14 can detect the user's distance traveled based on the integral value of the acceleration measured by the acceleration sensor. In addition, the inertial measurement unit 14 can detect the user's direction of movement by combining the acceleration in the three axes measured by the acceleration sensor with the angular velocity in the three axes measured by the gyro sensor.

[0030] The communication unit 15 communicates wirelessly with a smartphone and wireless earphones (neither of which are shown) carried by the user. For example, the communication unit 15 obtains information from the smartphone and wireless earphones indicating the usage status of these devices.

[0031] The output unit 16 provides the user with a notification corresponding to the degree of suspicion of the pursuer. Since this degree of suspicion is determined based on the detection status of a person behind the user, the output unit 16 will notify the user of the detection status of a person behind the user. The output unit 16 includes, for example, a haptic device that transmits information through touch. The haptic device is provided on the arm portion 10b shown in Figure 1 and presents the user with the sensation of being tapped on the shoulder through vibration. The output unit 16 is an example of a "notification means" according to the present invention.

[0032] The control unit 17 receives operations from the user on the wearable terminal 10. The wearable terminal 10 receives specific operations that trigger a high-level warning notification to the pursuer. These specific operations instruct the start of a high-level warning notification to the pursuer, and are, for example, operations in which the user blows on the arm portion 10b of the wearable terminal 10. The control unit 17 includes, for example, a wind speed sensor. The wind speed sensor is provided on the arm portion 10b of the wearable terminal 10 and detects the user's exhaled breath.

[0033] The light-emitting unit 18 provides a notification (warning) by emitting light to a person behind the user, thereby making the person behind aware that they are being detected and that the user is watching over them. The light-emitting unit 18 includes, for example, an LED (Light Emitting Diode) and emits light. The light-emitting unit 18 can emit light in multiple colors such as red and blue. In addition, the light-emitting unit 18 can control its luminosity and flashing speed. Luminosity refers to the strength of the light. Flashing speed refers to the number of flashes per unit time. As shown in Figure 1, one light-emitting unit 18 is provided on each side of the main body 10a of the wearable terminal 10. This allows the light-emitting unit 18 to provide a notification by emitting light to a person behind the user. The light-emitting unit 18 is an example of a "notification means" and a "display means" according to the present invention.

[0034] The wearable terminal 10 further functions as a tracking detection means 111, a suspiciousness calculation means 112, a notification control means 113, and a notification control means 114. These functions are realized by the control unit 11 executing a program stored in the storage unit 12.

[0035] (Tracking detection means) The tracking detection means 111 detects a moving object as a tracker that continuously tracks a moving user to a certain extent, based on the change in distance measured by the millimeter-wave sensor unit 13 for distance measurement and the movement state of the user detected by the inertial measurement unit 14.

[0036] Specifically, the tracking detection means 111 detects a tracker when the user is moving, based on the user's movement state detected by the inertial measurement unit 14. However, the tracking detection means 111 does not need to detect a tracker if the user's movement state detected by the inertial measurement unit 14 indicates that the user is stationary.

[0037] When the user is moving, the tracking detection means 111 tracks the positional relationship between the user and surrounding moving objects in a time series based on the distance history measured by the millimeter-wave sensor unit 13 for distance measurement. For example, the millimeter-wave sensor unit 13 for distance measurement measures the distance between the user and surrounding moving objects at predetermined intervals, such as 0.5 seconds. If the difference between the previously measured distance and the currently measured distance is less than or equal to a tolerance value, the tracking detection means 111 considers them to be the same moving object and stores the distance to that moving object in the storage unit 12. If the millimeter-wave sensor unit 13 for distance measurement can measure the direction and speed of the moving object, the tracking detection means 111 may also consider them to be the same moving object if the difference between the previously measured direction and the currently measured direction, or the difference between the previously measured speed and the currently measured speed, is less than or equal to a tolerance value.

[0038] The tracking detection means 111 then detects a moving object as a tracker if, based on the distance history stored in the memory unit 12, the distance between the moving object and the user has remained approximately constant over a predetermined period in the past. The predetermined period in the past is, for example, the past minute. For example, if the cumulative time over a predetermined period in the past during which the measured distance between a moving object and the user is within a predetermined range is greater than or equal to a predetermined threshold (first threshold), the tracking detection means 111 detects the moving object as a tracker, assuming that the distance between the moving object and the user has remained approximately constant. Alternatively, if the proportion of the cumulative time over a predetermined period in the past is greater than or equal to a predetermined threshold (second threshold), the tracking detection means 111 detects the moving object as a tracker, assuming that the distance between the moving object and the user has remained approximately constant. The predetermined range is a range in which the object can be considered to be tracking the user while maintaining an approximately constant distance, for example, 10m ± 2m.

[0039] (Method for calculating the degree of suspicion) The suspiciousness calculation means 112 calculates a suspiciousness level according to the continuity of the tracking of the tracker detected by the tracking detection means 111. Suspiciousness level is an index that indicates the degree to which a person is likely to pose a threat to the user. A higher suspiciousness level indicates a higher likelihood of a threat to the user. Indicators indicating the continuity of tracking include tracking time and tracking distance.

[0040] When using tracking time, the suspiciousness calculation means 112 first measures the tracking time of the pursuer. The tracking time is the elapsed time from the time the tracking detection means 111 detects the pursuer. Note that the tracking time may include the time the pursuer was tracking the user before the tracking detection means 111 detected the pursuer. In this case, the tracking time is the elapsed time from the time the pursuer started tracking the user (i.e., the start of the period in which it was determined that the distance between the moving object and the user was approximately constant, and this time is called the "start of tracking").

[0041] Next, the suspiciousness calculation means 112 calculates a suspiciousness level proportional to the tracking time using the following formula (1). Suspicion level = k × tracking time ... (1) Here, k is a coefficient greater than or equal to 0.

[0042] When using tracking distance, the suspiciousness calculation means 112 measures the tracking distance of the pursuer and calculates the suspiciousness using the tracking distance instead of the tracking time described above. The tracking distance is the distance the user has traveled since the tracking detection means 111 detected the pursuer. The tracking distance can be obtained, for example, by calculating the distance the user has traveled since the tracking detection means 111 detected the pursuer based on the distance traveled by the inertial measurement unit 14. The tracking distance may also include the distance the pursuer traveled while tracking the user before the tracking detection means 111 detected the pursuer. In this case, the tracking distance is the distance the user has traveled since the start of tracking. The suspiciousness may also be calculated using both tracking time and tracking distance. For example, the weighted sum of the suspiciousness calculated based on tracking time and the suspiciousness calculated based on tracking distance may be calculated as the final suspiciousness.

[0043] Furthermore, the suspiciousness calculation means 112 weights the suspiciousness level according to various conditions based on the weighting table 121 stored in the memory unit 12. The conditions for weighting the suspiciousness level indicate the actions of the pursuer, the user's environment, or the user's situation that increase the threat to the user during the tracking period. The tracking period is the period during which the pursuer is detected, and refers to the elapsed time from the start of tracking.

[0044] Figure 3 is an example of a weighting table 121. The weighting table 121 stores elements, conditions, and weighting coefficients in association with each other. Elements are those considered in order to weight the suspiciousness of the tracker. In the example shown in Figure 3, the elements include "movement pattern at the start of tracking," "change in the user's direction of movement," "branching of the user's movement path," "surrounding environment," "user's biometric information," and "user's use of other devices." Conditions are specific conditions set for each element. Weighting coefficients are coefficients used to weight the suspiciousness when each condition is met. The suspiciousness calculation means 112 determines whether each element stored in the weighting table 121 meets the conditions, and if it is determined that the conditions are met, it weights the suspiciousness using the corresponding weighting coefficient.

[0045] (Action pattern at the start of tracking) The "Action Pattern at the Start of Tracking" element has two conditions: "Start of tracking after ambushing" and "Start of tracking after turning." In both conditions, the tracker must start moving in a direction approximately equal to the user's direction of movement at the start of tracking. "Start of tracking after ambushing" refers to an action pattern in which the tracker waits in a stationary position where the user will pass, and then starts tracking the user after the user has passed. If the tracker starts tracking the user after ambushing, the suspiciousness calculation means 112 determines that the "Start of tracking after ambushing" condition is met and assigns a weight to the suspiciousness. This is because a tracker who performs such an action when starting to track a user is highly likely to be intentionally tracking the user.

[0046] Whether or not the condition of "initiating tracking after lying in wait" is met can be determined, for example, by the millimeter-wave sensor unit 13 for distance measurement detecting such tracking behavior patterns of the tracker. For example, the suspiciousness calculation means 112 determines that the condition of "initiating tracking after lying in wait" is met if the millimeter-wave sensor unit 13 for distance measurement detects a tracking behavior pattern in which the tracker begins tracking the user after lying in wait, and determines that the condition is not met if such behavior pattern is not detected.

[0047] For the condition "ambush followed by pursuit," a weighting coefficient "w1" is set. "w1" is a value greater than 0. When the condition "ambush followed by pursuit" is met, the degree of suspicion is weighted to be greater than when the condition is not met. For example, when the condition "ambush followed by pursuit" is met, the degree of suspicion calculation means 112 weights the degree of suspicion by multiplying it by the weighting coefficient "w1".

[0048] "Starting tracking after turning" refers to a behavioral pattern in which a pursuer moves in a different direction from the user, passes the user, and then changes direction to begin tracking the user. If a pursuer starts tracking the user after changing direction, the suspiciousness calculation means 112 determines that the condition of "starting tracking after turning" is met and assigns a weight to the suspiciousness level. This is because a pursuer who performs such an action when starting to track a user is highly likely to be intentionally tracking the user.

[0049] Whether or not the condition for "start tracking after turn" is met can be determined, for example, by the millimeter-wave sensor unit 13 for distance measurement detecting such a tracking person's movement pattern. For example, the suspiciousness calculation means 112 determines that the condition for "start tracking after turn" is met if the millimeter-wave sensor unit 13 for distance measurement detects a tracking person's movement pattern in which tracking of the user begins after a change of direction, and determines that the condition is not met if such a movement pattern is not detected.

[0050] For the condition "pursuit begins after turn," a weighting coefficient of "w2" is set. "w2" is a value greater than 0 and greater than "w1." This is because the action of starting a pursuit after a change of direction is considered a more suspicious action than the action of starting a pursuit after lying in wait. When the condition "pursuit begins after turn" is met, the degree of suspiciousness is weighted to be greater than when the condition is not met. For example, when the condition "pursuit begins after turn" is met, the suspiciousness calculation means 112 weights the degree of suspiciousness by multiplying it by the weighting coefficient "w2."

[0051] (Changes in the direction of user movement) The element of "change in user's direction of movement" is defined as "change of direction." "Change of direction" refers to a change in the user's direction of movement. If a user changes direction of movement during the tracking period, the suspiciousness calculation means 112 determines that the "change of direction" condition is met and assigns a weight to the suspiciousness. This is because if a tracker continues to track a user even after the user has changed direction of movement, there is a possibility that the tracker is intentionally tracking the user.

[0052] Whether or not the "change of direction" condition is met can be determined, for example, based on the change in the user's direction of movement detected by the inertial measurement unit 14. For example, the suspiciousness calculation means 112 determines that the "change of direction" condition is met if there is a change in the user's direction of movement detected by the inertial measurement unit 14 during the tracking period, and determines that the condition is not met if there is no change in the user's direction of movement. The suspiciousness calculation means 112 also counts the number of times the user's direction of movement has changed.

[0053] For the "change of direction" condition, a weighting coefficient of "w3" is set. "w3" is a value greater than 0. When the "change of direction" condition is met, the degree of suspicion is weighted so that the more times the user changes direction of movement, the higher the degree of suspicion. This is because if the pursuer continues to follow the user even though the user has changed direction of movement many times, there is a high possibility that the pursuer is persistently pursuing the user. For example, when the "change of direction" condition is met, the degree of suspicion calculation means 112 weights the degree of suspicion by multiplying the degree of suspicion by the value obtained by multiplying the weighting coefficient "w3" by the number of times the direction of movement has been changed. As a result, the more times the user changes direction of movement, the higher the degree of suspicion of a pursuer who continues to follow the user even after the change of direction of movement. In this embodiment, the degree of suspicion is determined according to whether or not the user changes direction of movement and the number of times, but the degree of suspicion does not necessarily have to be determined according to both of these, and may be determined according to either one of them.

[0054] (Branching of user travel routes) For the element of "branching of the user's movement path," the condition "passing a branching point" is set. "Passing a branching point" indicates that the user has passed a branching point. A branching point is a point where a path splits into multiple paths, including intersections, T-junctions, and Y-junctions. If the user passes a branching point during the tracking period, the suspiciousness calculation means 112 determines that the condition "passing a branching point" is met and assigns a weight to the suspiciousness level. This is because if the tracker continues to track the user after the user has passed a branching point, there is a possibility that the tracker is intentionally tracking the user.

[0055] Whether or not the condition of "passing a junction" is met can be determined, for example, by the millimeter-wave sensor unit 13 for distance measurement detecting the junction. At a junction, the road splits, so the distance between the user and stationary objects such as buildings and walls along the road changes significantly. The millimeter-wave sensor unit 13 for distance measurement can use this change in distance to detect the junction. The millimeter-wave sensor unit 13 can distinguish between moving objects in the surrounding area and stationary objects along the road by analyzing the Doppler shift of the reflected wave. For example, the millimeter-wave sensor unit 13 for distance measurement can distinguish between moving objects and stationary objects based on the difference in Doppler patterns caused by the difference between the relative velocity of a moving object to the user and the relative velocity of a stationary object to the user. Alternatively, the millimeter-wave sensor unit 13 for distance measurement may distinguish between moving objects and stationary objects in the surrounding area by analyzing the reflected wave pattern using AI. For example, the suspiciousness calculation means 112 determines that the condition "passing a branching point" is met if the millimeter-wave sensor unit 13 for distance measurement detects a branching point during the tracking period, and determines that this condition is not met if no branching point is detected. The suspiciousness calculation means 112 also counts the number of times the user passes through a branching point.

[0056] For the condition "passing a branching point," a weighting coefficient of "w4" is set. This weighting coefficient "w4" is a value greater than 0 and less than "w3." When the condition "passing a branching point" is met, the degree of suspicion is weighted so that the more times the branching point is passed, the higher the suspicion level. This is because if the user has passed through branching points many times, and the pursuer continues to follow the user, there is a high probability that the pursuer is persistently following the user. For example, when the condition "passing a branching point" is met, the suspicion level calculation means 112 weights the suspicion level by multiplying it by the value obtained by multiplying the weighting coefficient "w4" by the number of times the branching point has been passed. As a result, the more times the user passes through branching points, the higher the suspicion level of the pursuer who continues to follow the user after passing through branching points. In this embodiment, the degree of suspicion is determined according to the presence or absence of branches in the travel path taken by the user and the number of times the branches have been passed, but the degree of suspicion does not necessarily have to be determined according to both of these, and may be determined according to either one of them.

[0057] (Surrounding environment) For the "surrounding environment" element, the condition of a "high-risk environment" is set. A "high-risk environment" refers to a place with a high risk, including, for example, an area with little foot traffic. If the user is in a high-risk place during the tracking period, the suspiciousness calculation means 112 determines that the "high-risk environment" condition is met and weights the suspiciousness accordingly. This is because the risk of crime increases in high-risk places.

[0058] Whether or not the conditions for a "high-risk environment" are met can be determined, for example, by the millimeter-wave sensor unit 13 for distance measurement detecting people in the surrounding area. If the number of people in the surrounding area detected by the millimeter-wave sensor unit 13 for distance measurement is small, it indicates that the user is in an area with little foot traffic. Therefore, the suspiciousness calculation means 112 determines that the conditions for a "high-risk environment" are met if the number of people in the surrounding area detected by the millimeter-wave sensor unit 13 for distance measurement during the tracking period is less than or equal to a predetermined number, and determines that the conditions are not met if the number is greater than the predetermined number. Alternatively, the suspiciousness calculation means 112 may determine that the conditions for a "high-risk environment" are met when the user's surrounding environment changes to a high-risk environment, such as when the user moves from a busy area to a less busy area during the tracking period.

[0059] A weighting coefficient of "w5" is set for the "high-risk environment" condition. "w5" is a value greater than 0. When the "high-risk environment" condition is met, the level of suspicion is higher than when the condition is not met. For example, when the "high-risk environment" condition is met, the level of suspicion calculation means 112 weights the level of suspicion by multiplying it by the weighting coefficient "w5".

[0060] (User biometric information) For the "user's biometric information" element, the condition "increased respiratory rate or heart rate" is set. "Increased respiratory rate or heart rate" indicates that the user is in a state of tension, specifically when the respiratory rate or heart rate exceeds a predetermined value. If the respiratory rate or heart rate during the tracking period exceeds the predetermined value, the suspiciousness calculation means 112 determines that the condition "increased respiratory rate or heart rate" is met and weights the suspiciousness level accordingly. This is to reflect the sense of danger that the user intuitively feels in the suspiciousness level.

[0061] Whether or not the condition "increased respiratory rate or heart rate" is met can be determined, for example, by the biological millimeter-wave sensor unit 13 detecting the respiratory rate or heart rate. The suspiciousness calculation means 112 determines that the condition "increased respiratory rate or heart rate" is met if the respiratory rate or heart rate detected by the biological millimeter-wave sensor unit 13 during the tracking period is equal to or greater than a predetermined value, and determines that the condition is not met if it is less than the predetermined value.

[0062] For the condition "increased respiratory rate or heart rate," a weighting coefficient of "w6" is set. "w6" is a value greater than 0. When the condition "increased respiratory rate or heart rate" is met, the level of suspicion is higher than when this condition is not met. For example, when the condition "increased respiratory rate or heart rate" is met, the level of suspicion calculation means 112 weights the level of suspicion by multiplying it by the weighting coefficient "w6".

[0063] (User's usage of other devices) The element "User's use of other devices" has the condition "Using a smartphone or wireless earphones." "Using a smartphone or wireless earphones" indicates that the user is using a smartphone or wireless earphones. If the user is using a smartphone or wireless earphones during the tracking period, the suspiciousness calculation means 112 determines that the condition "Using a smartphone or wireless earphones" is met and assigns a weight to the suspiciousness level. This is because when a user is using a smartphone or wireless earphones, they may be less vigilant about their surroundings.

[0064] Whether or not the condition "using a smartphone or wireless earphones" is met can be determined, for example, by the communication unit 15 communicating with the smartphone or wireless earphones and obtaining information indicating the usage status from the smartphone or wireless earphones. The suspiciousness calculation means 112 determines that the condition "using a smartphone or wireless earphones" is met if the information obtained by the communication unit 15 during the tracking period indicates that the user is using a smartphone or wireless earphones, and determines that this condition is not met if the information indicates that the user is not using these devices.

[0065] For the condition "using a smartphone or wireless earphones," a weighting coefficient of "w7" is set. "w7" is a value greater than 0. When the condition "using a smartphone or wireless earphones" is met, the level of suspicion is higher than when this condition is not met. For example, when the condition "using a smartphone or wireless earphones" is met, the level of suspicion calculation means 112 weights the level of suspicion by multiplying it by the weighting coefficient "w7".

[0066] In this embodiment, the degree of suspicion is weighted by multiplying it by a weighting coefficient, but the method of weighting is not limited to this. For example, the degree of suspicion may be weighted by adding a weighting coefficient to the degree of suspicion. Alternatively, the degree of suspicion may be determined without weighting, based on conditions such as the tracking operator's movement pattern at the start of tracking, changes in the user's direction of movement, the number of branches in the user's movement path, the user's surrounding environment, the user's biometric information, and the user's use of other devices. For example, a configuration may be adopted in which the degree of suspicion, such as "high," "medium," or "low," is determined by comparing the value calculated using the above formula (1) with a threshold, and the degree of suspicion calculation means 112 may change this threshold depending on whether these conditions are met or not.

[0067] (Notification control means) The notification control means 113 causes the output unit 16 to output a notification corresponding to the level of suspicion calculated by the level of suspicion calculation means 112. Specifically, the notification control means 113 causes the output unit 16 to output vibrations corresponding to the level of suspicion. At this time, the notification control means 113 increases the vibration intensity as the level of suspicion increases. In this way, the notification control means 113 notifies the user of the level of suspicion of the pursuer through the vibration intensity.

[0068] For example, if the level of suspicion is below the third threshold, the notification control means 113 does not output vibration from the output unit 16. If the level of suspicion is above the third threshold but below the fourth threshold which is greater than the third threshold, the notification control means 113 outputs a weak vibration from the output unit 16, giving the user the sensation of being lightly tapped on the shoulder. If the level of suspicion is above the fourth threshold, the notification control means 113 outputs a strong vibration from the output unit 16, giving the user the sensation of being strongly tapped on the shoulder. This allows the user to understand that there is a suspicious follower and the degree of suspicion of that follower. The third and fourth thresholds are examples of the second conditions in this invention.

[0069] In this embodiment, the vibration intensity is varied according to the level of suspicion, but the vibration period and vibration pattern may also be varied according to the level of suspicion. For example, the notification control means 113 may shorten the vibration period as the level of suspicion increases.

[0070] (Notification control means) The notification control means 114 causes the light-emitting unit 18 to emit light to provide notification at a warning level corresponding to the suspiciousness level calculated by the suspiciousness level calculation means 112. Since this suspiciousness level is determined based on the detection status of a person in the background, the notification control means 114 causes the light-emitting unit 18 to emit light at a warning level corresponding to the detection status of a person in the background. The warning level is an indicator of the strength of the notification. The higher the warning level, the stronger the notification. The notification control means 114 is an example of a "control means" according to the present invention.

[0071] Specifically, the notification control means 114 first determines a warning level corresponding to the level of suspicion calculated by the suspicion level calculation means 112. For example, if the level of suspicion is 5th threshold or higher, the notification control means 114 determines a high warning level, and if it is below 5th threshold, it determines a low warning level. The 5th threshold is a value that serves as a criterion for determining whether or not to consider the pursuer as a suspicious person, and is an example of the first condition in the present invention.

[0072] Next, the notification control means 114 causes the light-emitting unit 18 to emit light in a light-emitting pattern corresponding to the determined warning level. The light-emitting pattern includes the light-emitting color, luminous intensity, and flashing speed. The notification control means 114 varies at least one of the light-emitting color, luminous intensity, and flashing speed depending on the warning level. The light-emitting pattern is an example of a "display pattern" according to the present invention.

[0073] When different colors of light are used, the notification control means 114 makes the light color more conspicuous the higher the warning level. For example, the notification control means 114 makes the light-emitting part 18 emit light in a non-emphasizing color such as blue when the warning level is low, and makes the light-emitting part 18 emit light in an emphasizing color such as red when the warning level is high.

[0074] When varying the luminosity, the notification control means 114 increases the luminosity as the warning level increases. For example, the notification control means 114 makes the light-emitting part 18 emit light at a low luminosity when the warning level is low, and makes the light-emitting part 18 emit light at a high luminosity when the warning level is high.

[0075] When varying the flashing speed, the notification control means 114 increases the flashing speed as the warning level increases. In other words, the notification control means 114 shortens the flashing interval as the warning level increases. For example, the notification control means 114 lights up or flashes the light-emitting unit 18 slowly when the warning level is low, and flashes the light-emitting unit 18 at high speed when the warning level is high.

[0076] As a result, the notification control means 114 can issue a strong notification to deter highly suspicious pursuers, while issuing a weak notification to less suspicious pursuers to inform them of their presence without causing discomfort.

[0077] Furthermore, the notification control means 114 may trigger a high-warning alert based on a specific operation performed by the user. In other words, the notification control means 114 does not have to trigger a high-warning alert until the user performs a specific operation. For example, for a low-warning alert, the notification control means 114 starts the alert when a pursuer is detected and a warning level corresponding to their suspiciousness is determined. On the other hand, for a high-warning alert, the notification control means 114 starts the alert after a pursuer is detected, a warning level corresponding to their suspiciousness is determined, and the user performs a specific operation. This is to prevent a high-warning alert from being triggered against the user's intention.

[0078] Furthermore, the notification control means 114 may cause different light-emitting units 18 to emit light depending on which millimeter-wave sensor unit 13 detects the pursuer. For example, if the millimeter-wave sensor unit 13 located on the left side of the main body unit 10a detects a pursuer, the notification control means 114 may cause only the light-emitting unit 18 located on the left side of the main body unit 10a to emit light, and not cause the light-emitting unit 18 located on the right side to emit light.

[0079] As described above, notification to the person behind is carried out based on the first condition, while notification to the user is carried out based on the second condition, which differs from the first condition. In other words, notification to the person behind is carried out even when the level of suspicion is low, while notification to the user is not carried out when the level of suspicion is low. This allows the person behind to become aware early on that they have been detected and that the user is being monitored. On the other hand, it prevents excessive notifications to the user, thus preventing unnecessary anxiety.

[0080] (operation) Figure 4 is a flowchart illustrating the operation of the wearable terminal 10 according to the first embodiment. This operation is performed continuously while the wearable terminal 10 is being worn by the user.

[0081] In step S101, the millimeter-wave sensor unit 13 for distance measurement of the wearable terminal 10 repeats the detection process until it detects a moving object in the vicinity of the user using the millimeter-wave sensor (the determination in step S101 is NO). When a moving object in the vicinity of the user is detected (the determination in step S101 is YES), this process proceeds to step S102.

[0082] In step S102, the millimeter-wave sensor unit 13 of the wearable terminal 10 measures the distance between the moving object detected in step S101 and the user at predetermined intervals using the millimeter-wave sensor, and stores the measured distance in the storage unit 12. If multiple moving objects are detected in step S101, the millimeter-wave sensor unit 13 measures the distance between each of these moving objects and the user.

[0083] In step S103, the inertial measurement unit 14 of the wearable terminal 10 detects the user's movement state and stores it in the memory unit 12. For example, the inertial measurement unit 14 detects whether or not the user is moving based on the acceleration detected by the acceleration sensor. The inertial measurement unit 14 also detects the user's distance and direction of movement based on the acceleration detected by the acceleration sensor and the angular velocity detected by the gyro sensor.

[0084] In step S104, the tracking detection means 111 of the wearable terminal 10 detects a tracker that is following the moving user based on the distance history stored in the memory unit 12 and the user's movement status. For example, the tracking detection means 111 detects a moving object as a tracker when the cumulative time during which the distance between the moving user and the moving object is within a predetermined range reaches 1 minute. If no tracker is detected (the determination in step S104 is NO), the process ends because the moving objects around the user are not tracking the user. On the other hand, if a tracker is detected (the determination in step S104 is YES), the process proceeds to step S105.

[0085] In step S105, the suspiciousness calculation means 112 of the wearable terminal 10 calculates the suspiciousness of the pursuer detected in step S104. For example, the suspiciousness calculation means 112 measures the pursuer's tracking time (or tracking distance) and calculates the suspiciousness using the formula (1) described above. The suspiciousness calculation means 112 also weights the suspiciousness based on the weighting table 121 shown in Figure 3.

[0086] For example, if the pursuer changes direction and begins pursuing the user, the condition "pursuit begins after turn" is met. In this case, the suspiciousness calculation means 112 multiplies the suspiciousness by the weighting coefficient "w2" associated with the "pursuit begins after turn" condition in the weighting table 121.

[0087] If the user changes direction twice during the tracking period, the "change of direction" condition is met. In this case, the suspiciousness calculation means 112 multiplies the suspiciousness by the value obtained by multiplying the weighting coefficient "w3" associated with the "change of direction" condition in the weighting table 121 by the number of changes in direction of movement, "2 times".

[0088] If a user passes through a branching point three times during the tracking period, the condition "passing a branching point" is met. In this case, the suspiciousness calculation means 112 multiplies the suspiciousness by the value obtained by multiplying the weighting coefficient "w4" associated with the condition "passing a branching point" in the weighting table 121 by the number of times the branching point was passed, which is "3 times".

[0089] If, during the tracking period, the user moves to an area with few people and the number of people around them falls below a predetermined number, the condition of a "high-risk environment" is met. In this case, the suspiciousness calculation means 112 multiplies the suspiciousness by the weighting coefficient "w5" associated with the "high-risk environment" condition in the weighting table 121.

[0090] If the user's heart rate exceeds a predetermined value during the tracking period, the condition "increased respiratory rate or heart rate" is met. In this case, the suspiciousness calculation means 112 multiplies the suspiciousness by the weighting coefficient "w6" associated with the condition "increased respiratory rate or heart rate" in the weighting table 121.

[0091] If the user is using wireless earphones during the tracking period, the condition "using a smartphone or wireless earphones" is met. In this case, the suspiciousness calculation means 112 multiplies the suspiciousness by the weighting coefficient "w7" associated with the condition "using a smartphone or wireless earphones" in the weighting table 121.

[0092] In step S106, the notification control means 113 of the wearable terminal 10 outputs a notification from the output unit 16 according to the level of suspicion calculated in step S105. For example, if the level of suspicion is above the fourth threshold, the notification control means 113 outputs a strong vibration from the output unit 16, giving the user the sensation of being strongly tapped on the shoulder. This allows the user to know that there is a highly suspicious person following them.

[0093] In step S107, the notification control means 114 of the wearable terminal 10 determines a warning level corresponding to the level of suspicion calculated in step S105. For example, if the level of suspicion is 5 or higher, the notification control means 114 determines a high warning level.

[0094] In step S108, if the warning level determined in step S107 is low (the determination in step S108 is NO), the notification control means 114 of the wearable terminal 10 can consider the pursuer not to be a suspicious person, and the process proceeds to step S109.

[0095] In step S109, the notification control means 114 of the wearable terminal 10 causes the light-emitting unit 18 to emit a low-level warning notification to the pursuer. For example, the notification control means 114 causes the light-emitting unit 18 to emit blue light at a low intensity.

[0096] On the other hand, in step S108, if the warning level determined in step S107 is high (the determination in step S108 is YES), the pursuer can be considered a suspicious person, and the process proceeds to step S110.

[0097] In step S110, the notification control means 114 of the wearable terminal 10 waits until a specific operation is performed by the user (the determination in step S110 is NO). For example, when the user blows on the arm portion 10b of the wearable terminal 10, the operation unit 17 detects the user's breath using the wind speed sensor and accepts the specific operation. When the operation unit 17 accepts the specific operation by the user (the determination in step S110 is YES), the process proceeds to step S111.

[0098] In step S111, the notification control means 114 of the wearable terminal 10 causes the light-emitting unit 18 to emit a high-intensity warning to the pursuer. For example, the notification control means 114 causes the light-emitting unit 18 to emit a high-intensity red light.

[0099] The wearable device 10 monitors the person following the user by repeating the processes in steps S101 to S111 above, outputs a notification to the user according to the degree of suspicion, and notifies the person following the user of the level of suspicion according to the degree of suspicion.

[0100] According to the first embodiment, by wearing the wearable terminal 10, the user can monitor their rear and receive warnings from pursuers with a level of suspicion corresponding to their level of suspiciousness. Furthermore, by providing strong warnings to highly suspicious pursuers, it is expected that this will deter suspicious individuals who are intentionally pursuing the user and act as a psychological deterrent against continuing the pursuit. On the other hand, by providing weaker warnings to less suspicious pursuers, such as simply letting them know that the user is being monitored, it is possible to prevent causing discomfort to individuals who do not intend to pursue the user.

[0101] Furthermore, by using the light-emitting unit 18, it is possible to visually notify people behind the device. In particular, at night or in dark places, the notification by light becomes more noticeable, increasing the effectiveness of the notification.

[0102] Furthermore, by making specific user actions the conditions for high-level warnings, it is possible to prevent high-level warnings from being issued against the user's intentions. In addition, high-level warnings can be issued at a time that the user deems necessary, such as when the user senses danger or when they determine that a warning is necessary.

[0103] Furthermore, by issuing notifications to users based on their level of suspicion, users can understand the presence of a stalker and their level of suspicion. This allows users to recognize the threat posed by stalkers and to increase their vigilance only against highly suspicious stalkers. As a result, users can protect themselves from the threat posed by stalkers.

[0104] 2. Second Embodiment In the first embodiment described above, the degree of suspicion of the pursuer was calculated, but in the second embodiment, instead of calculating the degree of suspicion, appropriate notification is given depending on whether the pursuer is suspicious or not. In the second embodiment, the same reference numerals as used in the first embodiment are used for components that are the same as those used in the first embodiment, and their detailed description is omitted.

[0105] (composition) Figure 5 is a diagram illustrating the configuration of a wearable terminal 10A according to the second embodiment. Similar to the wearable terminal 10 according to the first embodiment, the wearable terminal 10A includes a control unit 11, a storage unit 12, a millimeter-wave sensor unit 13, an inertial measurement unit 14, a communication unit 15, an output unit 16, an operation unit 17, and a light-emitting unit 18. In addition to the tracking detection means 111 similar to the first embodiment, the wearable terminal 10A also functions as a suspicious person determination means 115, a notification control means 113A, and a notification control means 114A. These functions are realized by the control unit 11 executing a program stored in the storage unit 12. Note that the wearable terminal 10A does not necessarily have the suspiciousness calculation means 112 according to the first embodiment.

[0106] The suspicious person determination means 115 determines whether a moving object behind the user is a suspicious person based on the continuity of the tracking detected by the tracking detection means 111. A suspicious person is defined as a person who may pose a threat to the user. Indicators of the continuity of tracking include tracking time and tracking distance.

[0107] When using tracking time, the suspicious person determination means 115 first measures the tracking time of the pursuer, similar to the suspiciousness calculation means 112 in the first embodiment. Then, the suspicious person determination means 115 determines that the pursuer is a suspicious person if the measured tracking time is equal to or greater than the sixth threshold, and determines that the pursuer is not a suspicious person if it is less than the sixth threshold. This sixth threshold is a tracking time that can be considered as intentionally tracking the user.

[0108] When using tracking distance, the suspicious person determination means 115 first measures the tracking distance of the pursuer, similar to the suspiciousness calculation means 112 in the first embodiment. Then, the suspicious person determination means 115 determines that the pursuer is a suspicious person if the measured tracking distance is greater than or equal to the seventh threshold, and determines that the pursuer is not a suspicious person if it is less than the seventh threshold. This seventh threshold is a tracking distance at which it can be considered that the pursuer is intentionally tracking the user.

[0109] The notification control means 113A causes the output unit 16 to output a notification according to the determination result of the suspicious person determination means 115. Since the suspicious person determination means 115 determines whether a person is suspicious based on the detection status of a person behind, the notification control means 113A will output a notification from the output unit 16 according to the detection status of a person behind. For example, if the pursuer is determined not to be suspicious, the notification control means 113A will not output vibration from the output unit 16. On the other hand, if the pursuer is determined to be suspicious, the notification control means 113A will output strong vibration from the output unit 16, giving the user the sensation of being strongly tapped on the shoulder.

[0110] The notification control means 114A causes the light-emitting unit 18 to emit light at a warning level corresponding to the determination result of the suspicious person determination means 115. Since the suspicious person determination means 115 determines whether a person is suspicious based on the detection status of a person behind, the notification control means 114A causes the light-emitting unit 18 to emit light at a warning level corresponding to the detection status of a person behind. Specifically, the notification control means 114A first determines a warning level according to the determination result of the suspicious person determination means 115. For example, if the notification control means 114A determines that the pursuer is not a suspicious person, it determines a low warning level, and if the pursuer is determined to be a suspicious person, it determines a high warning level. Subsequently, the notification control means 114A emits light from the light-emitting unit 18 in a light-emitting pattern corresponding to the determined warning level, similar to the notification control means 114 in the first embodiment.

[0111] (operation) Figure 6 is a flowchart showing the operation of the wearable terminal 10A according to the second embodiment. In the second embodiment, detailed explanations of processes that are the same as those in the first embodiment are omitted. The processes in steps S201 to S204 are the same as the processes in steps S101 to S104 according to the first embodiment.

[0112] In step S205, the suspicious person detection means 115 of the wearable terminal 10A determines whether the pursuer detected in step S204 is a suspicious person. For example, the suspicious person detection means 115 measures the pursuit time of the pursuer, and if the measured pursuit time is equal to or greater than the sixth threshold, it determines that the pursuer is a suspicious person.

[0113] In step S206, the notification control means 113A of the wearable terminal 10A outputs a notification from the output unit 16 according to the determination result in step S205. For example, if the pursuer is determined to be a suspicious person, the notification control means 113A outputs a strong vibration from the output unit 16, giving the user the sensation of being strongly tapped on the shoulder.

[0114] In step S207, the notification control means 114A of the wearable terminal 10 determines the warning level according to the determination result in step S205. For example, if the notification control means 114A determines that the pursuer is a suspicious person, it determines a high warning level. The processing in steps S208 to S211 is the same as the processing in steps S108 to S111 according to the first embodiment.

[0115] According to the second embodiment, a warning can be issued to the pursuer according to the level of suspicion without having to calculate the level of suspicion. Furthermore, by issuing a strong warning to a suspicious person, it is expected that a psychological deterrent will be exerted against those who are intentionally pursuing the user, preventing them from continuing their pursuit. On the other hand, by issuing a weaker warning to pursuers other than suspicious individuals, such as one that simply makes them aware that the user is being watched / monitored, it is possible to prevent causing discomfort to individuals who do not intend to pursue the user.

[0116] 3. Variant The present invention is not limited to the first and second embodiments described above, and can be implemented in various forms. The first and second embodiments may be used individually, in combination with one or more modifications, or switched between as needed during implementation.

[0117] (Variation 1) In the first and second embodiments described above, the light-emitting unit 18 was used as an example of a notification means for notifying a person behind the user, but the notification means is not limited to the light-emitting unit 18. The notification means can be any means that can notify a person behind the user. For example, the notification means may be a speaker that outputs sound or an image display unit such as a liquid crystal display. An image display unit is an example of a "display means" according to the present invention.

[0118] The speaker is provided, for example, in the main body 10a of the wearable terminal 10 or 10A. The notification control means 114 or 114A causes the speaker to emit an audible notification to a person behind the user, with a warning level corresponding to the degree of suspicion or the result of the suspicious person determination. Specifically, the notification control means 114 or 114A causes the speaker to output sound in an audio output mode corresponding to the warning level. The audio output mode includes volume, tone, and content of the sound. The notification control means 114 or 114A causes at least one of the volume, tone, or content of the sound to differ depending on the warning level.

[0119] When varying the volume, the notification control means 114 or 114A increases the volume as the warning level increases. For example, the notification control means 114 or 114A outputs sound from the speaker at a low volume when the warning level is low, and outputs sound from the speaker at a high volume when the warning level is high.

[0120] When differentiating the tone, the notification control means 114 or 114A makes the tone more intimidating the higher the warning level. For example, the notification control means 114 or 114A outputs a female voice from the speaker when the warning level is low, and a male voice from the speaker when the warning level is high.

[0121] When the content of the voice message is to be different, the notification control means 114 or 114A uses voice message corresponding to the warning level. For example, in the case of a low warning level, the notification control means 114 or 114A outputs the message "Please go ahead" from the speaker, and in the case of a high warning level, it outputs the message "Rear area is on alert" from the speaker.

[0122] The image display unit is provided, for example, on the main body 10a of the wearable terminal 10 or 10A. The notification control means 114 or 114A causes the image display unit to notify a person behind the user by displaying an image with a warning level corresponding to the degree of suspicion or the result of the suspicious person determination. Specifically, the notification control means 114 or 114A causes the image display unit to display an image in a display mode corresponding to the warning level. For example, in the case of a low warning level, the notification control means 114 or 114A displays an image of eyes that give a gentle impression on the image display unit, and in the case of a high warning level, it displays an image of eyes that give a threatening impression on the image display unit.

[0123] This modified version allows for notification to a person behind the user using a method other than light emission. Furthermore, by combining the light-emitting unit 18 with a speaker or image display unit, more effective notification can be achieved.

[0124] (Modification 2) In the first and second embodiments described above, the notification control means 114 or 114A would issue a low-warning notification if the degree of suspicion was less than the fifth threshold or if the pursuer was determined not to be suspicious, but it is not limited to this. If the degree of suspicion is less than the fifth threshold or the pursuer is not suspicious, the threat to the user is small, so the notification control means 114 or 114A does not need to issue a notification. This modification makes it possible to suppress notifications to people who are not suspicious and avoid causing discomfort.

[0125] (Variation 3) In the first and second embodiments described above, the notification control means 114 or 114A may further control the emission pattern of the light-emitting unit 18 in accordance with changes in the distance between the user and the person behind them, and the relative speed between the user and the person behind them. This distance and speed can be measured using the millimeter-wave sensor unit 13. For example, if the person behind the user is approaching the user or accelerating in the direction of approaching the user, the notification control means 114 or 114A may continuously change the hue of the light-emitting color of the light-emitting unit 18 to a more conspicuous color in a gradient manner, gradually increase the luminosity, or gradually increase the flashing speed. According to this modification, a stronger notification can be given to the pursuer in situations where there is a high probability that the pursuer will harm the user.

[0126] (Modification 4) In the first and second embodiments described above, the notification control means 114 or 114A may control the execution of a high-warning alert depending on the circumstances surrounding the user. The circumstances surrounding the user include the number of people in the surrounding area and the distance between the people and the user. The number of people in the surrounding area and the distance between the people and the user can be detected using the millimeter-wave sensor unit 13. For example, if there are multiple people around the user, the notification control means 114 or 114A will execute a high-warning alert to the pursuer if it determines a high-warning level based on the suspiciousness level or the determination of a suspicious person. On the other hand, if there are only the person to be notified around the user and no other people, the notification control means 114 or 114A will execute a low-warning alert instead of a high-warning alert to the pursuer, even if it determines a high-warning level based on the suspiciousness level or the determination of a suspicious person. This is because, if there are no other people around the user besides the suspicious stalker, the user will not be able to call for help if the stalker attempts to harm the user. This modification helps to suppress provoking the stalker in situations where the user is unable to easily ask for help.

[0127] (Variation 5) In the first and second embodiments described above, an example of a user identification operation was explained as the user blowing on the arm portion 10b of the wearable terminal 10 or 10A, but the user identification operation is not limited to this. The user identification operation can be any operation that instructs the start of a high-warning notification. It is preferable that the user identification operation is one that requires little effort from the user. For example, user identification operations include the user gripping the wearable terminal 10 or 10A, pressing an operation button, and voice input operations.

[0128] When the user grips the wearable terminal 10 or 10A, the arm portion 10b of the wearable terminal 10 or 10A is equipped with an electrostatic sensor or a pressure sensor. When the user grips the arm portion 10b, the electrostatic sensor or pressure sensor detects this operation. When the user presses an operation button, the arm portion 10b of the wearable terminal 10 or 10A is equipped with an operation button. When the user presses the operation button, the operation button detects this operation. When the user uses voice input, the arm portion 10b of the wearable terminal 10 or 10A is equipped with a microphone. When the user makes a voice command to initiate a high-warning alert, the microphone detects this voice input. Even with this modified configuration, it is possible to prevent high-warning alerts from being issued against the user's intention.

[0129] (Experimental variation 6) In the first and second embodiments described above, the millimeter-wave sensor unit 13 was given as an example of a detection means for detecting a person behind the user, but the detection means is not limited to the millimeter-wave sensor unit 13. Any means that can detect a person behind the user is acceptable as the detection means. For example, the detection means may be configured using an image sensor such as a camera or an ultrasonic sensor provided on the wearable terminal 10 or 10A.

[0130] When an image sensor is used, the detection means detects a person behind the user by analyzing the image data captured by the image sensor. When an ultrasonic sensor is used, the detection means detects a person behind the user by receiving the reflection of ultrasonic waves transmitted by the ultrasonic sensor. Furthermore, the detection means may be configured by combining at least two of the millimeter-wave sensor unit 13, the image sensor, and the ultrasonic sensor. Even with this modified configuration, it is possible to detect a person behind the user.

[0131] Similarly, the distance measuring means for measuring the distance between the user and surrounding moving objects is not limited to the millimeter-wave sensor unit 13, but may also be configured using, for example, an image sensor or an ultrasonic sensor.

[0132] (Example 7) In the first and second embodiments described above, an inertial measurement unit 14 was given as an example of a movement detection means for detecting the user's movement state, but the movement detection means is not limited to the inertial measurement unit 14. Any means that can detect the user's movement state may be used as the movement detection means. For example, the movement detection means may be configured using an acceleration sensor, an image sensor such as a camera, a millimeter-wave sensor, an ultrasonic sensor, or a GPS (Global Positioning System) receiver provided on the wearable terminal 10 or 10A.

[0133] When using an acceleration sensor, the movement detection means detects the user's movement state based solely on the three-axis acceleration measured by the acceleration sensor. When using an image sensor, the movement detection means detects the user's movement state by analyzing the image data captured by the image sensor. When using an ultrasonic sensor or millimeter-wave sensor, the movement detection means detects the user's movement state by having the ultrasonic sensor or millimeter-wave sensor measure the user's relative position and relative velocity with respect to surrounding objects. When using a GPS receiver, the movement detection means detects the user's movement state by having the GPS receiver acquire the user's location information. The user's movement state can also be detected in this modified configuration.

[0134] (Variation 8) In the first embodiment described above, a method using the millimeter-wave sensor unit 13 was given as an example of a method for detecting the branching points that the user has passed through. However, the method for detecting the branching points that the user has passed through is not limited to the method using the millimeter-wave sensor unit 13. Any method can be used to detect the branching points that the user has passed through. For example, a GPS receiver may be provided in the wearable terminal 10, and the branching points that the user has passed through may be detected by referring to map information pre-stored in the memory unit 12. The map information includes information about road branching points such as intersections. The suspiciousness calculation means 112 can detect the branching points that the user has passed through by identifying the user's travel route based on the user's location information acquired using the GPS receiver and comparing the identified travel route with the map information. The branching points that the user has passed through can also be detected in this modified configuration.

[0135] (Extreme variation 9) In the first embodiment described above, a low-traffic area was given as an example of a high-risk environment. However, a high-risk environment is not limited to low-traffic areas; for example, it could be a dark area or a quiet area. Whether or not an area is dark can be determined, for example, by equipping the wearable terminal 10 with an illuminance sensor and using this illuminance sensor. If the illuminance detected by the illuminance sensor is low, it indicates that the user is in a dark area. The suspiciousness calculation means 112 determines that the conditions for a "high-risk environment" are met if the illuminance detected by the illuminance sensor is below a predetermined value.

[0136] Furthermore, whether or not an area is quiet can be determined, for example, by equipping the wearable device 10 with a microphone and using this microphone. If the ambient volume detected by the microphone is low, it indicates that the user is in a quiet area. The suspiciousness calculation means 112 determines that the conditions for a "high-risk environment" are met if the volume detected by the microphone is below a predetermined value. According to this modified version, high-risk environments can be accurately detected by taking into account various environmental conditions such as foot traffic, darkness, and quietness.

[0137] (Variation 10) In the first embodiment described above, the millimeter-wave sensor unit 13 was given as an example of a means for detecting the user's biometric information, but the means for detecting the user's biometric information is not limited to the millimeter-wave sensor unit 13. Any means may be used to detect the user's biometric information. For example, the means for detecting the user's biometric information may be a heart rate monitor or respiratory sensor provided on the wearable terminal 10. In addition, the suspiciousness calculation means 112 may acquire the user's biometric information via the communication unit 15 from other devices such as a watch-type wearable terminal equipped with a heart rate monitor or respiratory sensor. The user's biometric information can also be detected in this modified configuration.

[0138] (Variation 11) In the first embodiment described above, the elements and conditions shown in Figure 3 were given as examples of elements and conditions considered for weighting the suspiciousness of the pursuer, but the invention is not limited to these. For example, the suspiciousness calculation means 112 may weight the suspiciousness if the user's movement speed is changed during the tracking period. This is because if a pursuer continues to follow the user after the user changes their movement speed, there is a possibility that the pursuer is intentionally tracking the user. According to this modification, the suspiciousness of a pursuer who continues to follow the user after the user changes their movement speed can be increased.

[0139] (Example 12) In the first and second embodiments described above, a haptic device that outputs notifications through touch was used as an example of an output unit 16, but the output unit 16 is not limited to a haptic device. The output unit 16 can be any means that can output notifications. For example, the output unit 16 may be a light-emitting unit such as an LED or an image display unit such as a liquid crystal display.

[0140] Multiple light-emitting units are provided on the arm portion 10b of the wearable terminal 10 or 10A, and the light-emitting units output a notification corresponding to the level of suspicion. The notification control means 113 or 113A may increase the number of light-emitting units to emit light as the level of suspicion increases.

[0141] The image display unit is provided on the arm portion 10b of the wearable terminal 10 or 10A and outputs a notification according to the level of suspicion based on the image. The notification control means 113 or 113A may cause the image display unit to display a numerical value or icon representing the level of suspicion.

[0142] Furthermore, the output unit 16 may be provided outside the wearable terminal 10 or 10A. For example, the notification control means 113 or 113A may transmit the level of suspicion to another device, such as a smartphone or a watch-type wearable terminal equipped with an image display unit, and cause the other device to display a numerical value or icon representing the level of suspicion on its image display unit.

[0143] This modified version allows for the visual communication of the degree of suspicion of the pursuer. Furthermore, by combining a haptic device with a light-emitting or image-displaying unit, the degree of suspicion can be communicated through both touch and sight, thus promoting more effective warnings.

[0144] (Example 13) In the first and second embodiments described above, two stages of notification were provided depending on the degree of suspicion or the determination of the person as suspicious. However, the number of notification stages is not limited to two. For example, the notification control means 114 or 114A may execute three or more stages of notification depending on the degree of suspicion or the determination of the person as suspicious. This modification allows for more detailed and appropriate notification to the pursuer.

[0145] Similarly, the notification control means 113 or 113A may output three or more levels of notifications from the output unit 16 depending on the level of suspicion or the result of the determination of a suspicious person. According to this modification, the user can grasp the level of suspicion in more detail and take appropriate action according to the situation.

[0146] (Variation 14) In the first embodiment described above, the wearable terminal 10 functioned as a tracking detection means 111, a suspiciousness calculation means 112, a notification control means 113, and a notification control means 114, but some of these functions may be provided by an external device.

[0147] Figure 7 illustrates the configuration of a rear-view monitoring system 100 according to this modified example. The rear-view monitoring system 100 comprises a wearable terminal 10B and a server device 20. These devices are connected via a communication line 30, including the Internet and a mobile communication network. The server device 20 comprises a control unit 21, a storage unit 22, and a communication unit 23. The control unit 21 and storage unit 22 are the same as the control unit 11 and storage unit 12 of the wearable terminal 10. The communication unit 23 communicates with the wearable terminal 10B via the communication line 30. By executing a program stored in the storage unit 22, the control unit 21 functions as a tracking detection means 111 and a suspiciousness calculation means 112. The wearable terminal 10B functions as a notification control means 113 and a notification control means 114. Note that the wearable terminal 10B does not necessarily have a tracking detection means 111 and a suspiciousness calculation means 112.

[0148] In this case, the wearable terminal 10B transmits sensor information, including the measurement results from the millimeter-wave sensor unit 13 and the detection results from the inertial measurement unit 14, to the server device 20 via the communication unit 15. The server device 20 uses the sensor information received from the wearable terminal 10B to detect the pursuer and calculate the degree of suspicion, and transmits the calculated degree of suspicion to the wearable terminal 10B via the communication unit 23. The wearable terminal 10B outputs a notification from the output unit 16 corresponding to the degree of suspicion received from the server device 20. The wearable terminal 10B also causes the light-emitting unit 18 to issue a warning notification corresponding to the degree of suspicion received from the server device 20.

[0149] Similarly, in the second embodiment, the server device 20 may also have a tracking detection means 111 and a suspicious person determination means 115 for the wearable terminal 10A. According to this modification, the processing load on the wearable terminal 10B can be reduced by performing part of the processing of the wearable terminal 10 or 10A according to the first or second embodiment on the server device 20 side.

[0150] (Variation 15) The configuration and operation of the wearable terminal 10 or 10A described in the first and second embodiments above are illustrative and not limited thereto. The wearable terminal 10 or 10A may have a configuration different from the configuration described in the first and second embodiments above, or it may be configured without some of the configurations. Furthermore, the processing steps of the wearable terminal 10 or 10A may be rearranged or some processing steps may be omitted, as long as they are not contradictory.

[0151] (Variation 16) Another aspect of the present invention may provide a method having steps of processing performed in a wearable terminal 10 or 10A. Yet another aspect of the present invention may provide a program to be executed in a wearable terminal 10 or 10A. This program may be provided stored on a computer-readable recording medium or provided by download via the Internet or the like.

[0152] (Example 17) In the first and second embodiments described above, the tracking detection means 111 was configured to detect a moving object as a tracker based on the distance measured by the millimeter-wave sensor unit 13 for distance measurement and the user's movement state detected by the inertial measurement unit 14. However, the detection of a tracker is not limited to a configuration that is based on both distance and the user's movement state.

[0153] For example, the tracking detection means 111 may detect a moving object as a tracker based solely on the change in distance measured by the millimeter-wave sensor unit 13 for distance measurement, without using the user's movement status. In this modified example, it is not necessary to provide an inertial measurement unit 14 that detects the user's movement status. According to this modified example, a tracker can be detected even without detecting the user's movement status.

[0154] Furthermore, the tracking detection means 111 may detect a pursuer based on the user's movement state detected by the inertial measurement unit 14 and the change in the relative speed of the other moving object relative to the user, without using the distance between the user and the other moving object. Specifically, the millimeter-wave sensor unit 13 measures the relative speed of the other moving object relative to the user. The tracking detection means 111 detects as a pursuer any other moving object where, when the user is moving, the cumulative time during a predetermined period in which the relative speed measured by the millimeter-wave sensor unit 13 is approximately 0 is equal to or greater than a first threshold, or where the proportion of the cumulative time during the predetermined period is equal to or greater than a second threshold. Here, a relative speed of approximately 0 means that the relative speed measured by the millimeter-wave sensor unit 13 is within a predetermined range including 0. In this modified example, the millimeter-wave sensor unit 13 does not need to measure the distance between the user and the other moving object. According to this modified example, a pursuer can be detected without measuring the distance between the user and the other moving object. [Explanation of Symbols]

[0155] 10, 10A, 10B: Wearable terminal, 10a: Main unit, 10b: Arm unit, 11: Control unit, 12: Memory unit, 13: Millimeter-wave sensor unit, 14: Inertial measurement unit, 15: Communication unit, 16: Output unit, 17: Operation unit, 18: Light-emitting unit, 20: Server device, 21: Control unit, 22: Memory unit, 23: Communication unit, 100: Rear monitoring system, 111: Tracking detection means, 112: Suspiciousness calculation means, 113, 113A: Notification control means, 114, 114A: Notification control means, 115: Suspicious person determination means

Claims

1. A wearable device that is attached to a user and monitors the area behind the user, A detection means for detecting a person located behind the user, A notification means for notifying the person in the rear, A control means that causes the notification means to issue a warning level corresponding to the detection status of the person in the background, A wearable device equipped with [a specific feature / feature].

2. The notification means includes a display means for displaying light or an image, The control means causes the notification means to perform the notification in a display manner corresponding to the warning level. The wearable device according to claim 1.

3. The system further comprises a means for calculating the degree of suspicion of the person in the background, The control means determines the warning level according to the level of suspicion. The wearable device according to claim 1.

4. The system further includes a means for determining whether the person in the background is a suspicious person or not. The control means determines the warning level according to the determination result of the suspicious person determination means. The wearable device according to claim 1.

5. The control means causes the notification means to execute the notification based on a specific operation performed by the user. The wearable device according to claim 1.

6. The control means causes the notification means to execute the notification according to the circumstances surrounding the user. The wearable device according to claim 1.

7. The system further comprises a notification means for notifying the user of the detection status of the person behind them. The wearable device according to claim 1.

8. The notification means provides notification based on a first condition regarding the detection status of the person behind, and the notification means provides notification based on a second condition regarding the detection status of the person behind, which is different from the first condition. The wearable terminal according to claim 7.

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