Display device and display method

Abstract

To provide a display device capable of displaying an appropriate image to a user while suppressing the influence of ambient temperature on an angular velocity sensor.SOLUTION: A display device 100 includes: a sensitivity correction unit 102 that obtains an ambient temperature of a gyro sensor 203, obtains sensitivity associated with the temperature range of the ambient temperature, and corrects an angular velocity of the gyro sensor 203 according to the sensitivity; a first orientation estimation unit 103 that estimates a first vehicle estimated orientation based on the corrected angular velocity; a second orientation estimation unit 104 that estimates a second vehicle estimated orientation based on the angular velocity detected by the gyro sensor 203; an orientation correction unit 105 that corrects the first vehicle estimated orientation using the position and speed of a vehicle 2 and derives a third vehicle estimated orientation; a display unit 110 that displays an image according to the third vehicle estimated orientation; and an update processing unit 106 that updates the sensitivity of the temperature range described above using a calculated sensitivity based on the second vehicle estimated orientation and the third vehicle estimated orientation.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a display device for displaying an image and the like.

Background Art

[0002] Conventionally, a display device has been proposed that projects light representing an image onto a plate-shaped display medium having translucency and reflects the light from the display medium, thereby allowing a user to view a background through the display medium while visually recognizing the image as a virtual image. Such a display device can display an image related to the background within the actual background. In particular, in the field related to automobiles, a so-called head-up display (HUD) has been developed that displays an image indicating speed and various warnings as a virtual image in front of the windshield during driving.

[0003] When using such a display device, a driver as a user can view an image related to driving without significantly moving the line of sight while looking at the outside world ahead, so that driving can be performed more safely. Specifically, such a display device performs a guidance display for navigating a vehicle. That is, the display device superimposes an image such as a triangle indicating a method (also called a guidance direction) for guiding the vehicle to a destination on the road surface.

[0004] In order to correctly display such a triangular image, it is necessary to accurately grasp the azimuth in which the vehicle is facing. The navigation device of Patent Document 1 calculates the azimuth of the vehicle using the angular velocity detected by an angular velocity sensor and corrects the azimuth based on the detection results by sensors other than the angular velocity sensor in order to accurately grasp the azimuth of the vehicle.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the display device of the navigation device of Patent Document 1 described above, there is a problem that an appropriate image may not be displayed to the user depending on the ambient temperature of the angular velocity sensor.

[0007] Therefore, the present disclosure provides a display device that can display an appropriate image to the user while suppressing the influence of the ambient temperature of the angular velocity sensor.

Means for Solving the Problems

[0008] A display device according to an aspect of the present disclosure acquires the ambient temperature of an angular velocity sensor mounted on a vehicle detected by a temperature sensor, acquires the sensitivity of the angular velocity sensor associated with a temperature range including the ambient temperature from a recording medium, a sensitivity correction unit that corrects the angular velocity detected by the angular velocity sensor according to the acquired sensitivity, a first azimuth estimation unit that estimates the azimuth in which the vehicle is facing as a first vehicle estimated azimuth based on the angular velocity corrected by the sensitivity correction unit, a second azimuth estimation unit that estimates the azimuth in which the vehicle is facing as a second vehicle estimated azimuth based on the angular velocity detected by the angular velocity sensor, an azimuth correction unit that derives a third vehicle estimated azimuth by correcting the first vehicle estimated azimuth using the position of the vehicle measured by a satellite positioning system and the speed of the vehicle, a display unit that displays an image corresponding to the third vehicle estimated azimuth, and an update processing unit that calculates the sensitivity of the angular velocity sensor as a calculated sensitivity based on the second vehicle estimated azimuth and the third vehicle estimated azimuth, and updates the sensitivity stored in the recording medium in association with the temperature range using the calculated sensitivity.

[0009] Note that these general or specific aspects may be implemented in a system, method, integrated circuit, computer program, or recording medium such as a computer-readable CD-ROM, or may be implemented in any combination of a system, method, integrated circuit, computer program, and recording medium. The recording medium may also be a non-transitory recording medium.

Advantages of the Invention

[0010] The display device of the present disclosure can display an appropriate image for the user while suppressing the influence of the ambient temperature of the angular velocity sensor.

[0011] Further advantages and effects in one aspect of the present disclosure will be clarified from the specification and drawings. Such advantages and / or effects are provided by some embodiments and the features described in the specification and drawings respectively, but not all of them are necessarily provided in order to obtain one or more of the same features.

Brief Description of the Drawings

[0012]

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DETAILED DESCRIPTION OF THE INVENTION

[0013] In order to solve the above problems, a display device according to an aspect of the present disclosure acquires the ambient temperature of an angular velocity sensor mounted on a vehicle detected by a temperature sensor, acquires from a recording medium the sensitivity of the angular velocity sensor associated with a temperature range including the ambient temperature, a sensitivity correction unit that corrects the angular velocity detected by the angular velocity sensor according to the acquired sensitivity, a first azimuth estimation unit that estimates, as a first vehicle estimated azimuth, the azimuth in which the vehicle is facing based on the angular velocity corrected by the sensitivity correction unit, a second azimuth estimation unit that estimates, as a second vehicle estimated azimuth, the azimuth in which the vehicle is facing based on the angular velocity detected by the angular velocity sensor, an azimuth correction unit that derives a third vehicle estimated azimuth by correcting the first vehicle estimated azimuth using the position of the vehicle measured by a satellite positioning system and the speed of the vehicle, a display unit that displays an image corresponding to the third vehicle estimated azimuth, and an update processing unit that calculates the sensitivity of the angular velocity sensor as a calculated sensitivity based on the second vehicle estimated azimuth and the third vehicle estimated azimuth, and updates the sensitivity stored in the recording medium in association with the temperature range using the calculated sensitivity.

[0014] As a result, the angular velocity is corrected according to the sensitivity corresponding to the ambient temperature of the angular velocity sensor, and the third vehicle estimated orientation is derived using the corrected angular velocity. In a specific example, if the first vehicle estimated orientation is corrected using the history of the position of the vehicle measured by the satellite positioning system up to a certain timing and the history of the speed of the vehicle up to that time, the third vehicle estimated orientation can be derived as the accurate orientation of the vehicle at that timing. That is, the accurate third vehicle estimated orientation can be derived at each timing when the period during which those histories are obtained elapses. Here, within that period, the angular velocity detected by the angular velocity sensor may vary due to changes in the ambient temperature. However, as described above, since the angular velocity is corrected according to the sensitivity corresponding to the ambient temperature of the angular velocity sensor, fluctuations in the angular velocity sensor due to such changes in the ambient temperature can be suppressed. Therefore, even in the case as described above, the third vehicle estimated orientation can be derived as the accurate orientation of the vehicle. That is, even in an environment where the ambient temperature changes, an appropriate third vehicle estimated orientation can be derived, and as a result, the influence of the ambient temperature of the angular velocity sensor can be suppressed and an appropriate image can be displayed to the user. Further, the sensitivity stored in the recording medium in association with the temperature range is updated using the calculated sensitivity calculated based on the second vehicle estimated orientation and the third vehicle estimated orientation. Therefore, even when the angular velocity sensor deteriorates over time, its sensitivity can be maintained at an appropriate value. As a result, the accuracy of the third vehicle estimated orientation can be maintained and an appropriate image can be displayed to the user.

[0015] Further, when the vehicle turns after passing through the first point and passes through the second point, the update processing unit may calculate the calculated sensitivity based on the amount of change in the second vehicle estimated orientation estimated at each of the first point and the second point and the amount of change in the third vehicle estimated orientation derived at each of the first point and the second point.

[0016] As a result, the calculation sensitivity is calculated based on the amount of change when the vehicle turns, that is, when the direction of the vehicle changes significantly, the accuracy of the calculated sensitivity can be improved. As a result, the sensitivity update associated with the temperature range can be appropriately performed.

[0017] Further, the azimuth correction unit may estimate the deviation of the vehicle's azimuth based on (a) the first position of the vehicle measured by the satellite positioning system, (b) the second position of the vehicle measured by the satellite positioning system when the vehicle moves from the first position, and (c) the dead reckoning using the first position, the azimuth of the vehicle at the first position, the angular velocity detected by the angular velocity sensor, and the speed of the vehicle, and correct the first estimated vehicle azimuth according to the deviation of the vehicle's azimuth. For example, the azimuth correction unit may estimate the angle formed by the straight line connecting the first position and the second position and the straight line connecting the first position and the estimated position as the deviation of the vehicle's azimuth.

[0018] Thereby, a travel trajectory by the satellite positioning system is obtained from the first position and the second position, and a travel trajectory by dead reckoning is obtained from the first position and the estimated position. Then, the deviation of the vehicle's azimuth is estimated based on those travel trajectories, and the first estimated vehicle azimuth is corrected according to the deviation of the azimuth. Therefore, the deviation of the azimuth can be suppressed, and the third estimated vehicle azimuth can be derived as the accurate direction of the vehicle.

[0019] Further, a sensitivity table indicating sensitivities associated with respective ones of a plurality of different temperature ranges is stored in the recording medium, and the sensitivity correction unit may acquire, from the recording medium, the sensitivity associated with the temperature range including the ambient temperature detected by the temperature sensor in the sensitivity table, and use the acquired sensitivity for correction of the angular velocity.

[0020] As a result, for each temperature range, angular velocity correction is performed using a sensitivity table indicating the sensitivity of the angular velocity sensor corresponding to that temperature range. Therefore, the more numerous the temperature ranges are, the more precisely the angular velocity can be corrected, and furthermore, angular velocity correction can be performed for a wide range of ambient temperatures.

[0021] Also, the recording medium stores a sensitivity table indicating the sensitivity associated with each of a plurality of different temperature ranges and the reliability of the sensitivity. The sensitivity correction unit determines, in the sensitivity table, whether a determination target reliability, which is the reliability associated with the temperature range including the ambient temperature detected by the temperature sensor, is equal to or greater than a threshold value. When the determination target reliability is equal to or greater than the threshold value, the sensitivity having the determination target reliability is acquired from the recording medium, and the acquired sensitivity is used for the correction of the angular velocity. When the determination target reliability is less than the threshold value, an alternative sensitivity may be derived and the alternative sensitivity may be used for the correction of the angular velocity.

[0022] As a result, adaptive processing according to the reliability of the sensitivity can be performed. That is, when the determination target reliability is low, instead of the sensitivity having the determination target reliability, angular velocity correction is performed using an alternative sensitivity, so that correction based on an unreliable sensitivity can be suppressed and the possibility of performing appropriate correction can be increased.

[0023] Also, when the determination target reliability is less than the threshold value, the sensitivity correction unit may acquire from the recording medium a low-reliability sensitivity, which is the sensitivity having the determination target reliability, and a high-reliability sensitivity, which is the sensitivity having a reliability equal to or greater than the threshold value, and derive the alternative sensitivity by weighted averaging of the low-reliability sensitivity and the high-reliability sensitivity using weights based on the respective reliabilities of the low-reliability sensitivity and the high-reliability sensitivity.

[0024] Thus, when the reliability of the determination target is low, the use of a high reliability sensitivity can increase the possibility of deriving an alternative sensitivity having a higher reliability than the low reliability sensitivity having the reliability of the determination target. Therefore, by using such an alternative sensitivity for the correction of the angular velocity, the possibility of performing appropriate correction can be increased.

[0025] Further, when the reliability of the determination target is less than the threshold value, the sensitivity correction unit acquires, from the recording medium, a first sensitivity and a second sensitivity that are sensitivities having a reliability of not less than the threshold value, respectively, and based on the first sensitivity and the second sensitivity, the temperature ranges associated with the first sensitivity and the second sensitivity, respectively, and the temperature range associated with the reliability of the determination target, the alternative sensitivity may be derived by extrapolation, interpolation, or linear interpolation of the sensitivity.

[0026] Thus, when the reliability of the determination target is low, by utilizing the first sensitivity and the second sensitivity having a high reliability and the linearity of the sensitivity with respect to each temperature range, etc., the possibility of deriving an alternative sensitivity having a higher reliability than the sensitivity having the reliability of the determination target can be increased. Therefore, by using such an alternative sensitivity for the correction of the angular velocity, the possibility of performing appropriate correction can be increased.

[0027] Further, when the reliability of the determination target is less than the threshold value and is higher than other reliabilities shown in the sensitivity table, the sensitivity having the reliability of the determination target may be used as the alternative sensitivity.

[0028] Thus, when the reliability of the determination target is low and, for example, all other reliabilities shown in the sensitivity table are even lower than the reliability of the determination target, the sensitivity having the reliability of the determination target is directly used as the alternative sensitivity. Therefore, by using other reliabilities shown in the sensitivity table, it is possible to suppress the derivation of a less reliable sensitivity and using such a sensitivity to correct the angular velocity.

[0029] Further, when the update processing unit updates the sensitivity shown in the sensitivity table using the calculated sensitivity, the update processing unit may further update the reliability of the sensitivity shown in the sensitivity table.

[0030] Thereby, the sensitivity shown in the sensitivity table and the reliability of the sensitivity can be maintained in an appropriate state.

[0031] Further, in updating the reliability of the sensitivity, the update processing unit may update the reliability of the sensitivity according to the driving data indicating the driving state of the vehicle when the calculated sensitivity is calculated.

[0032] Since the accuracy of the calculated sensitivity varies according to the driving state of the vehicle, the reliability of the sensitivity shown in the sensitivity table is updated according to the driving data, so that the accuracy of the calculated sensitivity is reflected in the reliability and the reliability can be appropriately updated.

[0033] Further, the update processing unit may update the reliability of the sensitivity to a higher reliability as the angle of the turn of the vehicle indicated by the driving data is larger.

[0034] Since the accuracy of the calculated sensitivity increases as the angle of the turn of the vehicle increases, the reliability of the sensitivity can be appropriately updated by updating the reliability of the sensitivity to a higher reliability as the angle is larger.

[0035] Further, the update processing unit may update the reliability of the sensitivity to a higher reliability as the distance of each of the two straight line sections indicated by the driving data is longer, and the two straight line sections may be sections in which the vehicle travels straight at the respective times before and after the vehicle turns.

[0036] Since the accuracy of the calculated sensitivity increases as the distance of each of the two straight line sections increases, the reliability of the sensitivity can be appropriately updated by updating the reliability of the sensitivity to a higher reliability as the distances are longer.

[0037] Further, the update processing unit may update the reliability of the sensitivity to a higher reliability as the travel time of the vehicle indicated by the travel data is shorter.

[0038] For example, when the vehicle is stopped, an offset value used for offset correction of the angular velocity sensor is determined. Therefore, the shorter the travel time after stopping, the less likely it is that the offset value will deviate. As a result, the shorter the travel time, the higher the accuracy of the calculated sensitivity. Therefore, by updating the reliability of the sensitivity to a higher reliability as the travel time is shorter, the reliability can be appropriately updated.

[0039] Further, the update processing unit may update the reliability of the sensitivity to a higher reliability as the stop time of the vehicle indicated by the travel data is longer and as the number of stops of the vehicle is greater.

[0040] As described above, when the vehicle is stopped, an offset value used for offset correction of the angular velocity sensor is determined. Therefore, the longer the stop time and the greater the number of stops of the vehicle, the less likely it is that the offset value will deviate. As a result, the longer the stop time, the higher the accuracy of the calculated sensitivity. Therefore, by updating the reliability of the sensitivity to a higher reliability as the stop time is longer, the reliability can be appropriately updated. Similarly, the greater the number of stops of the vehicle, the higher the accuracy of the calculated sensitivity. Therefore, by updating the reliability of the sensitivity to a higher reliability as the number of stops is greater, the reliability can be appropriately updated.

[0041] Further, when the engine of the vehicle starts, the update processing unit may significantly decrease each reliability indicated in the sensitivity table as the elapsed time since the engine stopped is longer.

[0042] The longer the elapsed time since the engine stopped, the higher the likelihood that the sensitivity of the angular velocity sensor has changed significantly from its sensitivity before the stop. Therefore, by significantly decreasing each reliability indicated in the sensitivity table as the elapsed time since the engine stopped is longer, those reliabilities can be appropriately managed.

[0043] Further, when the update processing unit updates the sensitivity associated with the temperature range in the sensitivity table, it may derive the reliability of the calculated sensitivity as the calculated reliability based on the driving data, and use the weights based on the reliability associated with the temperature range in the sensitivity table and the calculated reliability. The updated sensitivity may be derived by the weighted average of the sensitivity and the calculated sensitivity.

[0044] Thereby, the sensitivity can be appropriately updated by using the reliability of the calculated sensitivity and the reliability of the sensitivity shown in the sensitivity table.

[0045] Further, when the determination target reliability is less than the threshold value, the display unit may prohibit the output of the image.

[0046] Thereby, when the determination target reliability is low, the output of the image based on the sensitivity having such determination target reliability is prohibited, so that the display of inappropriate images can be suppressed.

[0047] Further, when the determination target reliability is less than the threshold value, the display unit may change the display mode of the image and output the image in the changed display mode.

[0048] Thereby, when the determination target reliability is low, the display mode of the image is changed. For example, the display mode for AR (Augmented Reality) can be changed to a non-AR display mode, and as a result, the display of inappropriate images in the AR display mode can be suppressed.

[0049] Hereinafter, embodiments will be specifically described with reference to the drawings.

[0050] Note that all the embodiments described below show comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components, steps, order of steps, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. In addition, among the components in the following embodiments, the components not described in the independent claims indicating the most general concept are described as optional components.

[0051] Also, each figure is a schematic diagram and is not necessarily drawn precisely. In each figure, the same reference numerals are given to the same constituent members.

[0052] (Embodiment) FIG. 1 is a diagram showing an example of use of the display device in the present embodiment.

[0053] The display device 100 in the present embodiment is configured as, for example, a head-up display (HUD) and is mounted on the vehicle 2. In a specific example, the display device 100 is built into the dashboard 2b of the vehicle 2.

[0054] Such a display device 100 projects the video light showing the display object 10, which is an image, onto the windshield 2a of the vehicle 2. As a result, this video light is reflected by the windshield 2a and heads, for example, toward the user 1 who is the driver of the vehicle 2. Thereby, the user 1 visually recognizes the display object 10 as a virtual image through the windshield 2a. That is, the display device 100 causes the user 1 to visually recognize the display object 10 as a virtual image. Note that causing the user 1 to visually recognize the display object 10 as a virtual image in this way is hereinafter also referred to as the display of the display object 10, and the operation of projecting the video light is synonymous with the operation of displaying the display object 10. In addition, the windshield 2a is an example of a display medium. In the present embodiment, the display medium is the windshield 2a, but when the vehicle 2 is equipped with a combiner, the display device 100 may project the video light onto the combiner as the display medium.

[0055] The windshield 2a is a plate-shaped display medium having translucency. Therefore, while showing the user 1 a background such as a road surface through the windshield 2a, the display device 100 causes the display object 10 to be visually recognized by the user 1 as a virtual image. That is, the display object 10 can be displayed in the actual background by AR (Augmented Reality).

[0056] Further, the display object 10 is an image in the shape of indicating one direction. In a specific example, it is a triangular image. This one direction is the direction of the tip of the triangle and is also referred to as the guiding direction. The guiding direction of the display object 10 is the direction for guiding the vehicle 2 to the destination.

[0057] Therefore, when using such a display device 100, the driver, who is the user 1, can see the display object 10 without greatly moving the line of sight while looking at the outside world ahead, so that the driver can more safely grasp the guiding direction and drive the vehicle 2.

[0058] FIG. 2 is a diagram showing an example of the interior of a vehicle 2 equipped with the display device 100 in the present embodiment.

[0059] The display device 100 projects image light onto the windshield 2a in a state hidden inside the dashboard 2b. By projecting the image light by the display device 100, the display object 10 appears as a virtual image within the display range d1 on the windshield 2a.

[0060] FIG. 3 is a diagram for explaining an example of the problem of image display.

[0061] The display device that is the comparison target of the display device 100 in this embodiment is configured as a HUD and is provided in the vehicle 3, similar to the display device 100. Then, this display device projects the video light showing the display object 11, which is a triangular image, onto the windshield of the vehicle 3, so that the user can visually recognize the display object 11 as a virtual image. That is, the display object 11 appears as a virtual image within the display range d2 on the windshield. In other words, the display device displays the display object 11 within the display range d2.

[0062] Here, the display device that is the comparison target of the display device 100 estimates the orientation of the vehicle 3 as the vehicle estimated orientation using the angular velocity detected by the angular velocity sensor mounted on the vehicle 3. Then, the display device determines the guidance direction based on the vehicle estimated orientation, draws the display object 11 indicating the guidance direction, and displays the drawn display object 11. Here, the sensitivity of the angular velocity sensor to the angular velocity varies according to the ambient temperature of the angular velocity sensor.

[0063] For example, as shown in FIG. 3, the vehicle 3 travels along the guidance path between time t1 and time t4. The guidance path is a path derived by the navigation device mounted on the vehicle 3 for guiding the vehicle 3 to the destination.

[0064] At time t1, the display device estimates the orientation along the guidance path as the vehicle estimated orientation. Therefore, the display device displays the display object 11 indicating the direction along the guidance path within the display range d2. Then, after time t1, the vehicle 3 turns to the right. Here, if the sensitivity of the angular velocity sensor to the angular velocity fluctuates due to a change in the ambient temperature of the angular velocity sensor, at time t2 after the vehicle 3 turns, the display device will display the display object 11 indicating a direction deviated from the direction along the guidance path. Specifically, there is a possibility that the display device estimates the orientation tilted to the left from the direction along the guidance path as seen from the vehicle 3 as the vehicle estimated orientation. Therefore, the display device will display the display object 11 indicating a direction shifted to the right from the direction along the guidance path as seen from the vehicle 3. That is, an overlap shift of the display object 11 will occur.

[0065] On the other hand, when the vehicle 3 continues to travel further from time t2 and the travel distance of the vehicle 3 reaches a predetermined distance, for example, by using the locus of the position of the vehicle 3 measured by a satellite positioning system, the deviation of the estimated vehicle orientation can be suppressed. As a result, at time t3, the display device can estimate the orientation along the guidance path as the estimated vehicle orientation. Therefore, the display device can display the display object 11 indicating the direction along the guidance path within the display range d2.

[0066] However, subsequently, in the same manner as described above, when the sensitivity of the angular velocity sensor fluctuates, at time t4 after the vehicle 3 further turns to the right, again, a deviation occurs in the direction indicated by the display object 11. That is, the display device estimates the orientation tilted to the left from the direction along the guidance path as seen from the vehicle 3 as the estimated vehicle orientation, and as a result, displays the display object 11 indicating the direction deviated to the right from the direction along the guidance path as seen from the vehicle 3. That is, an overlapping deviation of the display object 11 occurs.

[0067] Unlike the above-described display device, the display device 100 in the present embodiment can suppress the deviation of the direction indicated by the display object 10. That is, the display device 100 performs sensitivity correction according to the ambient temperature of the angular velocity sensor on the angular velocity detected by the angular velocity sensor, thereby suppressing the influence of the ambient temperature of the angular velocity sensor and displaying the display object 10 indicating an appropriate direction.

[0068] FIG. 4 is a block diagram showing the functional configuration of the display device 100 in the present embodiment.

[0069] The display device 100 includes an offset correction unit 101, a sensitivity correction unit 102, a first azimuth estimation unit 103, a second azimuth estimation unit 104, an azimuth correction unit 105, an update processing unit 106, a sensitivity table storage unit 107, a data storage unit 108, a drawing unit 109, and a display unit 110. Further, such a display device 100 acquires signals or information from a vehicle speed output unit 201, a satellite positioning system 202, a gyro sensor 203, a temperature sensor 204, and a navigation unit 205. Then, the display device 100 estimates the vehicle estimated azimuth based on these signals or information, and displays a display object 10 indicating the direction based on the vehicle estimated azimuth.

[0070] The vehicle speed output unit 201 is provided in, for example, the vehicle 2, and outputs vehicle speed information indicating the vehicle speed of the vehicle 2. Such a vehicle speed output unit 201 is realized by, for example, an ECU (Electronic Control Unit).

[0071] The satellite positioning system 202 is, for example, a GNSS (Global Navigation Satellite System) or a GPS (Global Positioning System). For example, a receiver that receives signals transmitted from satellites and is provided in the satellite positioning system 202 is provided in the vehicle 2. Such a satellite positioning system 202 measures the position and azimuth of the vehicle 2, and outputs position information indicating the position and azimuth information indicating the azimuth of the vehicle 2 to the display device 100.

[0072] The gyro sensor 203 is an example of an angular velocity sensor, detects the angular velocity of the yaw angle of the vehicle 2, and outputs an angular velocity signal indicating the detected angular velocity.

[0073] The temperature sensor 204 is configured as, for example, a thermistor, detects the ambient temperature around the gyro sensor 203 as the ambient temperature, and outputs a temperature signal indicating the detected ambient temperature.

[0074] The navigation unit 205 acquires, for example, the above-described position information from the satellite positioning system 202, searches for a route for the vehicle 2 to reach the destination using map data, and outputs route information indicating the guidance route, which is the searched route, and the position of the vehicle 2.

[0075] The offset correction unit 101 acquires an angular velocity signal from the gyro sensor 203 and performs offset correction on the angular velocity signal. For example, the offset correction unit 101 performs offset correction by subtracting an offset value from the angular velocity indicated by the angular velocity signal. Then, the offset correction unit 101 outputs the angular velocity signal subjected to the offset correction to the sensitivity correction unit 102 and the second azimuth estimation unit 104. For example, the offset correction unit 101 treats the angular velocity indicated by the angular velocity signal output from the gyro sensor 203 when the vehicle 2 is stopped as the offset value. Specifically, the offset correction unit 101 determines whether the vehicle speed has been 0 for the past 3 seconds and the change amount of the acceleration of the vehicle 2 is equal to or less than a threshold value based on the vehicle speed information output from the vehicle speed output unit 201. Note that the offset correction unit 101 may acquire the acceleration of the vehicle 2 from an acceleration sensor mounted on the vehicle 2. Then, when the offset correction unit 101 determines that the vehicle speed is 0 and the change amount of the acceleration is equal to or less than the threshold value, that is, when it determines that the vehicle 2 is stopped, the offset correction unit 101 treats the average value of the angular velocity indicated by the angular velocity signal output from the gyro sensor 203 during the past 3 seconds as the offset value.

[0076] The sensitivity correction unit 102 acquires the angular velocity signal subjected to offset correction from the offset correction unit 101. Then, the sensitivity correction unit 102 performs sensitivity correction on the angular velocity indicated by the angular velocity signal, that is, the angular velocity subjected to offset correction. In this sensitivity correction, the sensitivity correction unit 102 acquires a temperature signal from the temperature sensor 204. Further, the sensitivity correction unit 102 acquires the sensitivity associated with the temperature range including the ambient temperature indicated by the temperature signal from the sensitivity table storage unit 107. Then, the sensitivity correction unit 102 corrects the angular velocity according to the sensitivity. For example, the sensitivity correction unit 102 corrects the angular velocity by multiplying the angular velocity by the sensitivity. The sensitivity correction unit 102 outputs an angular velocity signal indicating the angular velocity subjected to sensitivity correction to the first azimuth estimation unit 103.

[0077] That is, the sensitivity correction unit 102 in the present embodiment acquires the ambient temperature of the gyro sensor 203 mounted on the vehicle 2 detected by the temperature sensor 204, acquires the sensitivity of the gyro sensor 203 associated with the temperature range including the ambient temperature from the sensitivity table storage unit 107, and corrects the angular velocity detected by the gyro sensor 203 and subjected to offset correction according to the acquired sensitivity.

[0078] The first azimuth estimation unit 103 acquires an angular velocity signal from the sensitivity correction unit 102. This angular velocity signal indicates the angular velocity subjected to offset correction and sensitivity correction. The first azimuth estimation unit 103 estimates the azimuth in which the vehicle 2 is facing as the first vehicle estimated azimuth by integrating the angular velocity. Note that the integration of the angular velocity is the time integration of the angular velocity. The first azimuth estimation unit 103 outputs first azimuth estimation information indicating the first vehicle estimated azimuth to the azimuth correction unit 105.

[0079] In this way, the first azimuth estimation unit 103 in the present embodiment estimates the azimuth in which the vehicle 2 is facing as the first vehicle estimated azimuth based on the angular velocity corrected by the sensitivity correction unit 102.

[0080] The second azimuth estimation unit 104 acquires the angular velocity signal from the offset correction unit 101. This angular velocity signal indicates the angular velocity without sensitivity correction. The second azimuth estimation unit 104 estimates the azimuth in which the vehicle 2 is facing as the second vehicle estimated azimuth by integrating the angular velocity after offset correction and before sensitivity correction. The second azimuth estimation unit 104 outputs second azimuth estimation information indicating the second vehicle estimated azimuth to the update processing unit 106.

[0081] As described above, the second azimuth estimation unit 104 in the present embodiment estimates the azimuth in which the vehicle 2 is facing as the second vehicle estimated azimuth based on the angular velocity detected by the gyro sensor 203 and without sensitivity correction.

[0082] The azimuth correction unit 105 acquires the first azimuth estimation information from the first azimuth estimation unit 103, and derives the third vehicle estimated azimuth by correcting the first vehicle estimated azimuth indicated by the first azimuth estimation information. Specifically, the azimuth correction unit 105 derives the third vehicle estimated azimuth by correcting the first vehicle estimated azimuth to the relative azimuth with respect to the initial azimuth. This initial azimuth is, for example, the azimuth of the vehicle 2 indicated by the azimuth information output from the satellite positioning system 202. There is an error in this azimuth. That is, there is a deviation in the azimuth. Therefore, the azimuth correction unit 105 estimates the azimuth deviation at each timing when a predetermined condition is satisfied, and updates the initial azimuth so that the deviation is reduced. Then, the azimuth correction unit 105 outputs third azimuth estimation information indicating the derived third vehicle estimated azimuth to the update processing unit 106 and the drawing unit 109.

[0083] As described above, the azimuth correction unit 105 estimates the azimuth deviation. Specifically, the azimuth correction unit 105 acquires not only the first azimuth estimation information but also vehicle speed information from the vehicle speed output unit 201, and acquires position information and azimuth information from the satellite positioning system 202. The azimuth correction unit 105 performs dead reckoning using the first vehicle estimated azimuth indicated by the first azimuth estimation information, for example, the initial azimuth indicated by the azimuth information, and the vehicle speed indicated by the vehicle speed information. The azimuth correction unit 105 derives the traveling locus of vehicle 2 by this dead reckoning. Further, the azimuth correction unit 105 derives the traveling locus of vehicle 2 based on the position of vehicle 2 indicated by the position information. The azimuth correction unit 105 estimates the above-described azimuth deviation based on the deviation of these traveling loci. Then, the azimuth correction unit 105 updates the initial azimuth by reflecting the azimuth deviation in the initial azimuth, for example, by adding or subtracting the azimuth deviation to / from the initial azimuth, and corrects the first vehicle estimated azimuth to the relative azimuth with respect to the initial azimuth. Thereby, the third vehicle estimated azimuth is derived.

[0084] Note that the estimation of the azimuth deviation is executed, for example, at each timing when the condition that vehicle 2 travels a predetermined distance or more is satisfied, in order to improve the accuracy of the estimation. Therefore, when vehicle 2 has not traveled a predetermined distance or more, the third vehicle estimated azimuth is derived based on the azimuth deviation estimated immediately before.

[0085] As described above, the azimuth correction unit 105 in the present embodiment derives the third vehicle estimated azimuth by correcting the first vehicle estimated azimuth using at least the position of vehicle 2 measured by the satellite positioning system 202 and the speed of vehicle 2.

[0086] The update processing unit 106 acquires a temperature signal from the temperature sensor 204, acquires second azimuth estimation information from the second azimuth estimation unit 104, and acquires third azimuth estimation information from the azimuth correction unit 105. That is, the update processing unit 106 acquires the ambient temperature of the gyro sensor 203 and the second vehicle estimated azimuth and the third vehicle estimated azimuth estimated or derived at the ambient temperature. Then, the update processing unit 106 updates the sensitivity table stored in the sensitivity table storage unit 107 using these ambient temperature, second vehicle estimated azimuth, and third vehicle estimated azimuth. The sensitivity table indicates the sensitivity of the gyro sensor 203 associated with each of a plurality of different temperature ranges.

[0087] Specifically, the update processing unit 106 first generates or updates driving history data. The driving history data indicates, for example, the association of the second vehicle estimated azimuth, the third vehicle estimated azimuth, and the ambient temperature obtained at each of a plurality of timings. Further, the update processing unit 106 calculates the sensitivity of the gyro sensor 203 corresponding to each ambient temperature based on the generated or updated driving history data. That is, the update processing unit 106 calculates the sensitivity of the gyro sensor 203 based on two second vehicle estimated azimuths and two third vehicle estimated azimuths associated with substantially the same ambient temperature shown in the driving history data. Note that the substantially same ambient temperature may be the same ambient temperature, may be an ambient temperature within a few percent error range, may be an ambient temperature within a predetermined range, or may be an ambient temperature within the same temperature range among the above-described plurality of temperature ranges.

[0088] Then, for each detected ambient temperature, the update processing unit 106 generates or updates sensitivity history data indicating the sensitivity of the gyro sensor 203 calculated for that ambient temperature. When updating the sensitivity table, the update processing unit 106 calculates the average value of the sensitivities associated with each temperature within the same temperature range indicated in the sensitivity history data. Then, the update processing unit 106 updates the sensitivity by replacing the sensitivity associated with the above-mentioned temperature range in the sensitivity table with the calculated average value. In other words, the update processing unit 106 performs calibration on the sensitivity.

[0089] In this way, the update processing unit 106 in the present embodiment calculates the sensitivity of the gyro sensor 203 as the calculated sensitivity based on the second vehicle estimated azimuth estimated by the second azimuth estimation unit 104 and the third vehicle estimated azimuth derived by the azimuth correction unit 105, and updates the sensitivity stored in the sensitivity table storage unit 107 in association with the temperature range using the calculated sensitivity. The temperature range is a temperature range including the ambient temperature detected by the temperature sensor 204 when the second vehicle estimated azimuth and the third vehicle estimated azimuth are estimated or derived.

[0090] The sensitivity table storage unit 107 is a recording medium for storing the above-mentioned sensitivity table. The data storage unit 108 is a recording medium for storing the driving history data for updating the sensitivity table and the sensitivity history data. These recording media are a hard disk drive, RAM (Random Access Memory), ROM (Read Only Memory), or semiconductor memory, etc. Note that such a recording medium may be volatile or non-volatile.

[0091] The drawing unit 109 acquires the third orientation estimation information from the orientation correction unit 105, and generates a display object 10 indicating the orientation based on the third vehicle estimated orientation indicated by the third orientation estimation information. That is, the drawing unit 109 draws the display object 10. When drawing the display object 10, the drawing unit 109 acquires route information from the navigation unit 205. Then, based on the route information, the drawing unit 109 specifies the orientation along the guidance route at the position of the vehicle 2, and draws a display object 10 having a shape inclined from the third vehicle estimated orientation to the orientation along the guidance route, that is, a display object 10 indicating the orientation toward the guidance route side from the third vehicle estimated orientation. The drawing unit 109 outputs an image signal indicating the display object 10 drawn in this way to the display unit 110.

[0092] The display unit 110 acquires an image signal from the drawing unit 109, and displays the display object 10 according to the image signal. For example, the display unit 110 includes a light source and an optical system, and generates video light indicating the display object 10 so that the display object 10 can be visually recognized by the user 1. Then, the display unit 110 projects the video light onto the windshield 2a. As a result, the display object 10 is visually recognized by the user 1. That is, the display unit 110 projects the video light indicating the display object 10 onto the windshield 2a, reflects the video light toward the user 1 side in the vehicle 2 by the windshield 2a, and allows the display object 10 to be visually recognized as a virtual image by the user 1 through the windshield 2a.

[0093] As described above, the display unit 110 in the present embodiment displays the display object 10 which is an image corresponding to the third vehicle estimated orientation.

[0094] FIG. 5 is a diagram for explaining the calculation of sensitivity.

[0095] The update processing unit 106 generates or updates, for example, the travel history data 108a shown in FIG. 5. Specifically, as described above, the update processing unit 106 acquires the ambient temperature of the gyro sensor 203 and the second vehicle estimated azimuth and the third vehicle estimated azimuth estimated or derived at that ambient temperature. Further, the update processing unit 106 acquires position information from the satellite positioning system 202. The update processing unit 106 associates the position indicated by the position information, the ambient temperature detected at that position, and the second vehicle estimated azimuth and the third vehicle estimated azimuth estimated or derived at that ambient temperature with the time when the vehicle 2 traveled that position. Thereby, travel data is generated. If the travel history data 108a is not stored in the data storage unit 108, the update processing unit 106 generates the travel data as the travel history data 108a and stores it in the data storage unit 108. On the other hand, if the travel history data 108a is stored in the data storage unit 108, the update processing unit 106 updates the travel history data 108a by adding the latest travel data to the already stored travel history data 108a.

[0096] Next, the update processing unit 106 calculates the sensitivity of the gyro sensor 203 using the travel history data 108a. For example, the update processing unit 106 searches the travel history data 108a for two second vehicle estimated azimuths and two third vehicle estimated azimuths associated with substantially the same ambient temperature. In a specific example, when the ambient temperature "T01" and the ambient temperature "T02" are substantially the same temperature, the update processing unit 106 finds the second vehicle estimated azimuths "ψ201" and "ψ202" and the third vehicle estimated azimuths "ψ301" and "ψ302". Next, the update processing unit 106 calculates the change amount "ψ302 - ψ301" of the third vehicle estimated azimuths "ψ301" and "ψ302". Similarly, the update processing unit 106 calculates the change amount "ψ202 - ψ201" of the second vehicle estimated azimuths "ψ201" and "ψ202". Then, the update processing unit 106 calculates the sensitivity of the gyro sensor 203 by dividing the change amount "ψ302 - ψ301" of the third vehicle estimated azimuth by the change amount "ψ202 - ψ201" of the second vehicle estimated azimuth.

[0097] Here, the update processing unit 106 may use the second vehicle estimated azimuth and the third vehicle estimated azimuth associated with the positions traveled before and after the vehicle 2 turns in the travel history data 108a for calculating the sensitivity. For example, after the vehicle 2 travels to the first point at time "t03", it turns right and travels to the second point at time "t04". At this time, in the travel history data 108a, the second vehicle estimated azimuth and the third vehicle estimated azimuth change by approximately 90° between time "t03" and "t04". Also, the ambient temperature "T03" at time "t03" and the ambient temperature "T04" at time "t04" are substantially the same, and the ambient temperature does not change between time "t03" and "t04". In this case, the update processing unit 106 uses the second vehicle estimated azimuth "ψ203" and the third vehicle estimated azimuth "ψ303" associated with time "t03", and the second vehicle estimated azimuth "ψ204" and the third vehicle estimated azimuth "ψ304" associated with time "t04" for calculating the sensitivity.

[0098] In this way, when the vehicle 2 turns after passing the first point and passes the second point, the update processing unit 106 calculates the calculated sensitivity based on the change amount of the second vehicle estimated azimuth estimated at each of the first point and the second point, and the change amount of the third vehicle estimated azimuth derived at each of the first point and the second point. Thereby, since the calculated sensitivity is calculated based on the change amount when the vehicle 2 turns, that is, since the calculated sensitivity is calculated when the direction of the vehicle 2 changes greatly, the accuracy of the calculated sensitivity can be improved. As a result, the sensitivity table storage unit 107 (that is, the sensitivity table) can appropriately update the sensitivity associated with the temperature range.

[0099] Here, for example, the update processing unit 106 may preferentially use the second vehicle estimated azimuth and the third vehicle estimated azimuth corresponding to the amount of change for sensitivity calculation as the amount of change in each of the second vehicle estimated azimuth and the third vehicle estimated azimuth is larger. That is, the update processing unit 106 may preferentially use the second vehicle estimated azimuth and the third vehicle estimated azimuth respectively associated with two positions where the vehicle 2 has traveled before and after the turn for sensitivity calculation as the turning angle is larger. Further, the update processing unit 106 may preferentially use the second vehicle estimated azimuth and the third vehicle estimated azimuth respectively associated with two positions where the vehicle 2 has traveled before and after the turn for sensitivity calculation as the travel of the vehicle 2 before and after the turn is closer to straight-ahead travel and the travel distance at that time is longer. Thereby, the accuracy of the calculated sensitivity can be further improved. Note that the update processing unit 106 may determine that the travel of the vehicle 2 is closer to straight-ahead travel as the variation in the second vehicle estimated azimuth or the third vehicle estimated azimuth is smaller, and may derive the travel distance of the vehicle 2 based on the position indicated by the position information sequentially output from the satellite positioning system 202.

[0100] Note that the travel data included in the travel history data 108a shown in FIG. 5 may further indicate the first vehicle estimated azimuth or may indicate the travel distance. Further, the travel data only needs to indicate at least the second vehicle estimated azimuth, the third vehicle estimated azimuth, and the ambient temperature, and does not need to indicate the time and the position.

[0101] FIG. 6 is a diagram showing an example of update of the sensitivity table in the embodiment.

[0102] As shown in FIG. 5, when the update processing unit 106 calculates the sensitivity of the gyro sensor 203 corresponding to the ambient temperature using the travel history data 108a, it associates the sensitivity with the ambient temperature. Then, as shown in FIG. 6, the update processing unit 106 generates sensitivity history data 108b indicating the associated sensitivity and ambient temperature. That is, if the sensitivity history data 108b is not yet stored in the data storage unit 108, the update processing unit 106 generates the sensitivity history data 108b indicating the associated sensitivity and ambient temperature and stores the sensitivity history data 108b in the data storage unit 108. On the other hand, if the sensitivity history data 108b is already stored in the data storage unit 108, the update processing unit 106 adds the associated sensitivity and ambient temperature to the sensitivity history data 108b. As a result, the sensitivity history data 108b is updated. Note that the sensitivity history data 108b shown in FIG. 6 indicates the sensitivity (i.e., the calculated sensitivity) as "Gn0, Gn1, Gn2", etc.

[0103] The update processing unit 106 updates the sensitivity table 107a shown in FIG. 6 by calculating the average value of the sensitivities indicated by the sensitivity history data 108b. For example, in the sensitivity table 107a, a plurality of temperature ranges and the initial values of the sensitivities for each of the plurality of temperature ranges are shown in advance. Each of the plurality of temperature ranges is, for example, as shown in FIG. 6, "-40 to -30 °C", "-30 to -20 °C", "-20 to -10 °C", etc. The initial value may be a predetermined sensitivity (e.g., 1) or the sensitivity calculated immediately before. Note that the plurality of temperature ranges shown in FIG. 6 is an example, and the temperature ranges in the present disclosure are not limited to that example and may be any. Also, the temperature range "a to b °C" expressed using the numerical values a and b may mean a °C or higher and less than b °C, or higher than a °C and b °C or lower.

[0104] The update processing unit 106 calculates, for each of the plurality of temperature ranges, the average value of the sensitivities associated with one or more ambient temperatures within that temperature range in the sensitivity history data 108b. Then, the update processing unit 106 updates the sensitivity table 107a by replacing, for each of the plurality of temperature ranges, the sensitivity associated with that temperature range in the sensitivity table 107a with the average value calculated for that temperature range. Further, each time a new combination of ambient temperature and sensitivity is added to the sensitivity history data 108b, the update processing unit 106 may update the sensitivity of the temperature range including that ambient temperature, as indicated by the sensitivity table 107a, as described above. Note that the sensitivity table 107a shown in FIG. 6 indicates the sensitivity (i.e., the average value of the calculated sensitivities) by "G0, G1, G2", etc.

[0105] The sensitivity correction unit 102 acquires, from the sensitivity table storage unit 107, the sensitivity associated with the temperature range including the ambient temperature detected by the temperature sensor 204 in such a sensitivity table 107a, and uses the acquired sensitivity for correcting the angular velocity (i.e., sensitivity correction). Thereby, for each temperature range, correction of the angular velocity is performed using the sensitivity table 107a indicating the sensitivity of the gyro sensor 203 corresponding to that temperature range. Therefore, the more the number of such temperature ranges, the more precisely the angular velocity can be corrected, and furthermore, the angular velocity can be corrected for a wide range of ambient temperatures.

[0106] FIG. 7 is a diagram for explaining the azimuth correction by the azimuth correction unit 105. Specifically, FIG. 7 schematically shows an example of the traveling locus of the vehicle 2 on the horizontal plane defined by the XY coordinate system. The vehicle 2 moves, for example, from the lower left side (i.e., the origin side of the XY coordinates) to the upper right side (i.e., the plus side in the X-axis direction and the Y-axis direction) on this horizontal plane. The solid line in FIG. 7 indicates the actual traveling locus of the vehicle 2. This actual traveling history is not recognized by the azimuth correction unit 105 or the like, but is shown for comparison with the traveling locus by the satellite positioning system 202 and the traveling locus by dead reckoning. The dashed line in FIG. 7 indicates the traveling locus by the satellite positioning system 202, and the alternate long and short dash line in FIG. 7 indicates the traveling locus by dead reckoning.

[0107] The azimuth correction unit 105 acquires the position information output from the satellite positioning system 202 at any time, and identifies the traveling locus by the satellite positioning system 202 from position A1 to position A2 based on the positions indicated by the position information. Further, the azimuth correction unit 105 acquires the first azimuth estimation information output from the first azimuth estimation unit 103 at any time, and acquires the vehicle speed information output from the vehicle speed output unit 201 at any time. Then, the azimuth correction unit 105 performs dead reckoning starting from position A1. That is, the azimuth correction unit 105 performs dead reckoning based on position A1, the initial azimuth when position A1 is measured, the first vehicle estimated azimuth indicated by the first azimuth estimation information, and the vehicle speed indicated by the vehicle speed information. Thereby, the traveling locus by dead reckoning from position A1 to position B1 is identified. Note that position B1 is the position estimated by dead reckoning when position A2 is measured.

[0108] Next, the azimuth correction unit 105 estimates the angle formed by the straight line connecting position A1 and position A2 and the straight line connecting position A1 and position B1 as the azimuth deviation. Then, the azimuth correction unit 105 updates the initial azimuth by adding or subtracting the deviation (i.e., the above-mentioned formed angle) to / from the initial azimuth, and corrects the first vehicle estimated azimuth to the relative azimuth with respect to the initial azimuth. By this correction, the third vehicle estimated azimuth is derived.

[0109] In this way, the orientation correction unit 105 in the present embodiment estimates the deviation of the orientation of the vehicle 2 and corrects the first vehicle estimated orientation according to the deviation of the orientation of the vehicle 2. That is, the orientation correction unit 105 uses (a) the first position of the vehicle 2 measured by the satellite positioning system 202, (b) the second position of the vehicle 2 measured by the satellite positioning system 202 when the vehicle 2 moves from the first position, (c) the first position, the orientation of the vehicle 2 at the first position (i.e., the initial orientation), the angular velocity detected by the gyro sensor 203, and the speed of the vehicle 2 to estimate the deviation of the orientation of the vehicle 2 based on dead reckoning. Further, the orientation correction unit 105 estimates the angle formed by the straight line connecting the first position and the second position and the straight line connecting the first position and the estimated position as the deviation of the orientation of the vehicle 2. Thereby, the traveling trajectory by the satellite positioning system 202 is obtained from the first position and the second position, and the traveling trajectory by dead reckoning is obtained from the first position and the estimated position. Then, the deviation of the orientation of the vehicle 2 is estimated based on those traveling trajectories, and the first vehicle estimated orientation is corrected according to the deviation of the orientation. Therefore, the deviation of the orientation can be suppressed, and the third vehicle estimated orientation can be derived as the accurate orientation of the vehicle 2.

[0110] FIG. 8 is a flowchart showing the overall processing of the display device 100.

[0111] The display device 100 executes a sensitivity table update process (step S100) and a display process using the sensitivity table 107a (step S200). The sensitivity table update process is a process of updating the sensitivity table 107a stored in the sensitivity table storage unit 107. The display process using the sensitivity table 107a is a process of further correcting the offset-corrected angular velocity using the sensitivity indicated in the sensitivity table 107a and displaying the display object 10 based on the corrected angular velocity. Such a sensitivity table update process and a display process using the sensitivity table 107a may be executed in parallel or in series.

[0112] FIG. 9 is a flowchart showing an example of a schematic process of the sensitivity table update process. That is, the flowchart of FIG. 9 shows the process of step S100 in FIG. 8 in detail.

[0113] First, the update processing unit 106 generates or updates the driving history data 108a (step S110). That is, the generation / update process of the driving history data 108a is performed. Next, the update processing unit 106 generates or updates the sensitivity history data 108b using the driving history data 108a (step S120). That is, the generation / update process of the sensitivity history data 108b is performed.

[0114] Next, when a new sensitivity is added to the sensitivity history data 108b in association with the ambient temperature in the process of step S120, the update processing unit 106 identifies the temperature range including the ambient temperature from the sensitivity table 107a. Then, the update processing unit 106 calculates the average value of the sensitivities associated with each ambient temperature in that temperature range in the sensitivity history data 108b (step S131). Next, the update processing unit 106 updates the sensitivity table 107a by associating the average value calculated for that temperature range with that temperature range in the sensitivity table 107a (step S132). If a sensitivity is already associated with that temperature range in the sensitivity table 107a, the update processing unit 106 replaces the existing sensitivity with the above-mentioned average value.

[0115] Then, the update processing unit 106 determines whether the driving of the vehicle 2 continues (step S133). Here, when the update processing unit 106 determines that the driving continues (YES in step S133), the process from step S110 is repeatedly executed. On the other hand, when the update processing unit 106 determines that the driving does not continue (NO in step S133), the sensitivity table update process ends.

[0116] FIG. 10 is a flowchart showing an example of the generation / update process of the travel history data 108a. That is, the flowchart of FIG. 10 shows the process of step S110 in FIG. 9 in detail.

[0117] First, the update processing unit 106 initializes the travel distance of the vehicle 2 (step S111). For example, the update processing unit 106 sets the travel distance to 0. Then, the update processing unit 106 determines whether the travel distance of the vehicle 2 has reached a threshold or more (step S112). For example, the update processing unit 106 may acquire information indicating the travel distance from a device external to the display device 100, or may specify the travel distance based on the position information output from the satellite positioning system 202. Further, the threshold of the travel distance is, for example, 10 m. Here, if it is determined that the travel distance has not reached the threshold or more (NO in step S112), the update processing unit 106 repeatedly executes the process of step S112.

[0118] On the other hand, if it is determined that the travel distance has reached the threshold or more (YES in step S112), the update processing unit 106 acquires the second azimuth estimation information from the second azimuth estimation unit 104, acquires the third azimuth estimation information from the azimuth correction unit 105, and acquires a temperature signal from the temperature sensor 204. That is, the update processing unit 106 acquires travel data including the second vehicle estimated azimuth indicated by the second azimuth estimation information, the third vehicle estimated azimuth indicated by the third azimuth estimation information, and the ambient temperature indicated by the temperature signal (step S113). At this time, the update processing unit 106 may acquire position information from the satellite positioning system 202 and include the position of the vehicle 2 indicated by the position information in the travel data. Further, the update processing unit 106 may also include the time when the second vehicle estimated azimuth and the like are acquired in the travel data.

[0119] Then, the update processing unit 106 updates the travel history data 108a by adding the travel data to the travel history data 108a stored in the data storage unit 108 (step S114). If the travel history data 108a is not stored in the data storage unit 108, the update processing unit 106 generates the travel data as the travel history data 108a and stores it in the data storage unit 108.

[0120] FIG. 11 is a flowchart showing an example of the generation and update process of the sensitivity history data 108b. That is, the flowchart of FIG. 11 shows the process of step S120 in FIG. 9 in detail.

[0121] First, the update processing unit 106 acquires two pieces of travel data each containing substantially the same ambient temperature from the travel history data 108a updated in step S110. At this time, the update processing unit 106 acquires two pieces of travel data that satisfy a predetermined condition, for example, obtained before and after the turning of the vehicle 2. In other words, as shown in FIG. 5, when the travel data includes a position, the update processing unit 106 selects two points that satisfy a predetermined condition and are associated with substantially the same ambient temperature (step S121).

[0122] Next, the update processing unit 106 calculates the sensitivity of the gyro sensor 203 with respect to the ambient temperature based on the second vehicle estimated azimuth and the third vehicle estimated azimuth of each of the two points shown in the travel history data 108a (step S122).

[0123] Then, the update processing unit 106 updates the sensitivity history data 108b by adding the sensitivity calculated in step S122 in association with the ambient temperature to the sensitivity history data 108b stored in the data storage unit 108 (step S123). If the sensitivity history data 108b is not stored in the data storage unit 108, the update processing unit 106 generates data including the calculated sensitivity and the ambient temperature as the sensitivity history data 108b and stores it in the data storage unit 108.

[0124] FIG. 12 is a flowchart showing an example of display processing using the sensitivity table 107a. That is, the flowchart of FIG. 12 shows the processing of step S200 in FIG. 8 in detail.

[0125] First, the offset correction unit 101 acquires an angular velocity signal from the gyro sensor 203 (step S201), and the sensitivity correction unit 102 acquires a temperature signal from the temperature sensor 204 (step S202). Next, the offset correction unit 101 performs offset correction on the angular velocity indicated by the angular velocity signal acquired in step S201 (step S203). Then, the sensitivity correction unit 102 performs sensitivity correction using the sensitivity table 107a stored in the sensitivity table storage unit 107 on the angular velocity for which offset correction has been performed in step S203 (step S210). At this time, the ambient temperature of the gyro sensor 203 indicated by the temperature signal acquired in step S202 is used for sensitivity correction. That is, in step S210, sensitivity correction processing using the ambient temperature is performed.

[0126] Next, the first azimuth estimation unit 103 calculates the first vehicle estimated azimuth. That is, the first azimuth estimation unit 103 calculates the first vehicle estimated azimuth by integrating the angular velocity sensitivity-corrected by the sensitivity correction processing in step S210 (step S221). Then, the azimuth correction unit 105 corrects the first vehicle estimated azimuth calculated in step S221 using the position of the vehicle 2 measured by the satellite positioning system 202 and the vehicle speed indicated by the vehicle speed information output from the vehicle speed output unit 201 (step S222). By the correction in this step S222, the third vehicle estimated azimuth is derived or calculated.

[0127] Next, the drawing unit 109 draws the display object 10 which is AR content using the route information output from the navigation unit 205 and the third vehicle estimated azimuth calculated in step S222. The display unit 110 displays the display object 10 by projecting the video light indicating the display object 10 onto the windshield 2a (step S223).

[0128] Then, the display device 100 determines whether or not the vehicle 2 is continuing to travel (step S224). Here, if the display device 100 determines that the travel is continuing (YES in step S224), it repeatedly executes the process from step S201. On the other hand, if the display device 100 determines that the travel is not continuing (NO in step S224), it ends the display process using the sensitivity table 107a.

[0129] FIG. 13 is a flowchart showing an example of the sensitivity correction process. That is, the flowchart of FIG. 13 shows the process of step S210 in FIG. 12 in detail.

[0130] First, the sensitivity correction unit 102 refers to the sensitivity table 107a stored in the sensitivity table storage unit 107 (step S211). Next, the sensitivity correction unit 102 grasps the ambient temperature of the gyro sensor 203 indicated by the temperature signal acquired in step S202 of FIG. 12, and acquires the sensitivity associated with the temperature range including the ambient temperature in the sensitivity table 107a (step S212). That is, the sensitivity correction unit 102 reads out the sensitivity associated with the ambient temperature detected by the temperature sensor 204 from the sensitivity table 107a.

[0131] Then, the sensitivity correction unit 102 calculates the sensitivity-corrected angular velocity by multiplying the angular velocity that has been offset-corrected in step S203 of FIG. 12 by the sensitivity acquired in step S212 (step S213).

[0132] As described above, in the present embodiment, the angular velocity is corrected according to the sensitivity corresponding to the ambient temperature of the gyro sensor 203, and the third vehicle estimated azimuth is derived using the corrected angular velocity. In a specific example, if the first vehicle estimated azimuth is corrected using the history of the position of the vehicle 2 measured by the satellite positioning system up to a certain timing and the history of the speed of the vehicle 2 up to that time, the third vehicle estimated azimuth can be derived as the accurate orientation of the vehicle 2 at that timing. That is, an accurate third vehicle estimated azimuth can be derived at each timing when the period during which those histories are obtained elapses. Here, within that period, the angular velocity detected by the gyro sensor 203 may vary due to changes in the ambient temperature. However, as described above, since the angular velocity is corrected according to the sensitivity corresponding to the ambient temperature of the gyro sensor 203, fluctuations of the gyro sensor 203 due to such changes in the ambient temperature can be suppressed. Therefore, even in the case as described above, the third vehicle estimated azimuth can be derived as the accurate orientation of the vehicle 2. That is, even in an environment where the ambient temperature changes, an appropriate third vehicle estimated azimuth can be derived, and as a result, the influence of the ambient temperature of the gyro sensor 203 can be suppressed and an appropriate display object 10 can be displayed to the user 1. Further, the sensitivity stored in the sensitivity table storage unit 107 in association with the temperature range is updated using the calculated sensitivity calculated based on the second vehicle estimated azimuth and the third vehicle estimated azimuth. Therefore, even when the gyro sensor 203 deteriorates over time, its sensitivity can be maintained at an appropriate value. As a result, the accuracy of the third vehicle estimated azimuth can be maintained and an appropriate display object 10 can be displayed to the user 1.

[0133] (Modification Example 1) In the above-described embodiment, for each temperature range of the sensitivity table 107a in the initial state, a value indicating, for example, 1 may be associated in advance as the initial value of the sensitivity. On the other hand, the sensitivity may not be associated with each temperature range of the sensitivity table 107a in the initial state. And, as the number of driving data added to the driving history data 108a increases, the number of temperature ranges associated with the sensitivity in the sensitivity table 107a increases. However, if there are many temperature ranges in the sensitivity table 107a that are not associated with the sensitivity, it is difficult to sufficiently perform the sensitivity correction. Therefore, the update processing unit 106 in this modification interpolates the sensitivity for such a sensitivity table 107a. That is, the update processing unit 106 associates the sensitivity with respect to the temperature range in the sensitivity table 107a where the sensitivity is not yet associated without using the driving history data 108a.

[0134] FIG. 14 is a diagram showing an example of the update of the sensitivity table 107a in this modification.

[0135] For example, the sensitivity table 107a shows the sensitivity "G5" associated with the temperature range "10 to 20°C" and the sensitivity "G6" associated with the temperature range "20 to 30°C". And the sensitivity is not shown in other temperature ranges of the sensitivity table 107a.

[0136] In such a case, the update processing unit 106 may derive the sensitivity corresponding to other temperature ranges by linear interpolation or extrapolation. For example, when the sensitivities "G5" and "G6" are "0.8" and "0.9", respectively, the update processing unit 106 derives "0.7" as the sensitivity corresponding to the temperature range "0 to 10°C" and derives "1.0" as the sensitivity corresponding to the temperature range "30 to 40°C". And the update processing unit 106 writes the sensitivity derived in this way in the sensitivity table 107a in association with the temperature range. Thereby, the sensitivity is interpolated.

[0137] Also, in the sensitivity table 107a shown in FIG. 14, extrapolation is used for sensitivity interpolation, but interpolation may also be used. For example, in the sensitivity table 107a, the sensitivity "G3" is associated with the temperature range "-10 to 0 °C". In such a case, the update processing unit 106 derives the sensitivity "G4" corresponding to the temperature range "0 to 10 °C" by linear interpolation or interpolation using the temperature range "-10 to 0 °C" and its sensitivity "G3", and the temperature range "10 to 20 °C" and its sensitivity "G5". Then, the update processing unit 106 writes the sensitivity "G4" in association with the temperature range "0 to 10 °C" into the sensitivity table 107a. Sensitivity is also interpolated by such interpolation.

[0138] FIG. 15 is a diagram showing another example of the update of the sensitivity table 107a in this modified example.

[0139] For example, the sensitivity table 107a shows the sensitivity "G5" associated with the temperature range "10 to 20 °C" and the sensitivity "G6" associated with the temperature range "20 to 30 °C", similar to the example shown in FIG. 14. And no sensitivity is shown in other temperature ranges of the sensitivity table 107a.

[0140] In such a case, the update processing unit 106 acquires the sensitivity tables 107b used in one or more other vehicles 4 from each vehicle 4 via a communication network such as the Internet. Then, the update processing unit 106 interpolates the sensitivity of the sensitivity table 107a of the vehicle 2 using those sensitivity tables 107b. Each vehicle 4 is equipped with a display device 100, and the update processing unit 106 of the display device 100 transmits the sensitivity table 107b to the cloud server via the communication network. The cloud server accumulates the sensitivity tables 107b of those vehicles 4. Then, the update processing unit 106 of the display device 100 mounted on the vehicle 2 requests the cloud server to transmit the sensitivity table 107b.

[0141] Specifically, the update processing unit 106 of the vehicle 2 requests the transmission of the sensitivity table 107b of the vehicle 4 that satisfies the first condition and the second condition. The first condition is that the sensitivity is shown for a temperature range not associated with the sensitivity in the sensitivity table 107a. The second condition is that the sensitivity closest to the sensitivity in the sensitivity table 107a is shown for the same temperature range as the temperature range associated with the sensitivity in the sensitivity table 107a. Then, when the update processing unit 106 of the vehicle 2 acquires the sensitivity table 107b that satisfies those conditions from the cloud server, it copies the sensitivity indicated by the sensitivity table 107b to the sensitivity table 107a. That is, the update processing unit 106 finds the same temperature range as the temperature range not associated with the sensitivity in the sensitivity table 107a from the sensitivity table 107b. Then, the update processing unit 106 associates the sensitivity associated with that temperature range in the sensitivity table 107b with that temperature range in the sensitivity table 107a of the vehicle 2. Thereby, the sensitivity is interpolated in the sensitivity table 107a of the vehicle 2.

[0142] (Modification Example 2) In the sensitivity table 107a in the above-described embodiment and Modification Example 1, the sensitivity is associated with the temperature range. In the sensitivity table in this modification example, not only the sensitivity but also the reliability of the sensitivity is associated with the temperature range.

[0143] FIG. 16 is a diagram showing an example of the sensitivity table in this modification example.

[0144] The sensitivity table 107c in this modification example has, for example, as shown in FIG. 16, the sensitivity and the reliability of the sensitivity associated with each temperature range. For example, for the temperature range "0 to 10°C", the sensitivity "G4" and the reliability "T4" of the sensitivity "G4" are associated. That is, in this modification example, the sensitivity table storage unit 107 stores the sensitivity table 107c indicating the sensitivity and the reliability of the sensitivity associated with each of a plurality of different temperature ranges.

[0145] For example, in the initial state of the sensitivity table 107c, for each temperature range, a preset initial value of sensitivity and a preset initial value of reliability may be associated. Then, when the update processing unit 106 updates the sensitivity of the sensitivity table 107c, it also updates the reliability of that sensitivity. That is, when the update processing unit 106 updates the sensitivity shown in the sensitivity table 107c using the calculated sensitivity, it further updates the reliability of that sensitivity shown in the sensitivity table 107c. Thereby, the sensitivity shown in the sensitivity table 107c and the reliability of that sensitivity can be maintained in an appropriate state.

[0146] In a specific example, in updating the reliability of the sensitivity, the update processing unit 106 updates the reliability of the sensitivity according to the driving data indicating the driving state of the vehicle 2 when the calculated sensitivity is calculated. Since the accuracy of the calculated sensitivity varies according to the driving state of the vehicle 2, by updating the reliability of the sensitivity shown in the sensitivity table 107c according to the driving data, the accuracy of the calculated sensitivity can be reflected in the reliability and the reliability can be appropriately updated.

[0147] More specifically, the update processing unit 106 updates the reliability of the sensitivity to a higher reliability as the turning angle of the vehicle 2 indicated by the running data is larger. For example, as shown in the example of FIG. 5, after the vehicle 2 travels the first point at time "t03", it turns right and travels the second point at time "t04". In this case, the update processing unit 106 calculates the sensitivity of the gyro sensor 203 as the calculated sensitivity using the second vehicle estimated azimuths "ψ203" and "ψ204" and the third vehicle estimated azimuths "ψ303" and "ψ304" shown in the travel history data 108a. At this time, the update processing unit 106 uses the change amount of the second vehicle estimated azimuth "ψ204 - ψ203" or the change amount of the third vehicle estimated azimuth "ψ304 - ψ303" as the turning angle of the vehicle 2, and calculates a higher reliability as the angle is larger. Then, the update processing unit 106 updates the reliability by replacing the reliability of the sensitivity associated with the temperature range including the ambient temperatures "T03" and "T04" in the sensitivity table 107c with the calculated reliability. Since the accuracy of the calculated sensitivity increases as the turning angle of the vehicle 2 is larger, the reliability can be appropriately updated by updating the reliability to a higher reliability as the angle is larger.

[0148] Further, the update processing unit 106 may update the reliability of the sensitivity to a higher reliability as the distance of each of the two straight line sections indicated by the travel history data 108a is longer. The two straight line sections are sections in which the vehicle 2 travels straight at each of the times before and after the vehicle 2 turns. Since the travel history data 108a consists of a plurality of travel data, it can be said that the two straight line sections are indicated by the travel data.

[0149] For example, as shown in the example of FIG. 5, after the vehicle 2 travels to the first point at time "t03", it turns right and travels to the second point at time "t04". In this case, the update processing unit 106 identifies each position "XY03", "XY02", "XY01", etc. that the vehicle 2 has traveled to by time "t03" as indicated by the travel history data 108a. Then, the update processing unit 106 searches for one or more positions arranged linearly from the position "XY03" among the plurality of identified positions. The update processing unit 106 determines the distance between the position farthest from the position "XY03" among the one or more positions and the position "XY03" as the distance of the linear section at the previous point in time when the vehicle 2 turns. Similarly, the update processing unit 106 identifies each position "XY04", "XY05", "XY06", etc. that the vehicle 2 has traveled to after time "t04" as indicated by the travel history data 108a. Then, the update processing unit 106 searches for one or more positions arranged linearly from the position "XY04" among the plurality of identified positions. The update processing unit 106 determines the distance between the position farthest from the position "XY04" among the one or more positions and the position "XY04" as the distance of the linear section at the subsequent point in time when the vehicle 2 turns. The update processing unit 106 updates the reliability using the distances of these linear sections. Note that each travel data included in the travel history data 108a may directly indicate the distance of the linear section up to the timing when the travel data is obtained. Since the accuracy of the calculation sensitivity increases as the distance of each of the two linear sections increases, the reliability can be appropriately updated by updating the sensitivity reliability to a high reliability as the distances increase. Note that the linear section is a section in which the vehicle 2 travels straight, in other words, a section in which each position where the vehicle 2 travels is arranged linearly, but the straight travel and the straight line do not have to be strict straight travel and straight line. For example, if the approximate straight line obtained from those positions and the distance between each position are equal to or less than a threshold value, it may be interpreted that the vehicle 2 travels straight and each position is arranged linearly.

[0150] In addition, each piece of driving data included in the driving history data 108a may indicate the driving time of the vehicle 2 up to the timing when the driving data is obtained. The driving time is the time from when the vehicle 2 most recently stopped to when the vehicle 2 is continuously driving. In such a case, the update processing unit 106 may update the reliability of the sensitivity to a higher reliability as the driving time of the vehicle 2 indicated by the driving data when the calculated sensitivity is calculated is shorter. For example, when the vehicle 2 is stopped, an offset value used for offset correction of the gyro sensor 203 is determined. Therefore, the shorter the driving time after stopping, the less likely it is that the offset value will deviate. As a result, since the accuracy of the calculated sensitivity increases as the driving time is shorter, the reliability can be appropriately updated by updating the reliability of the sensitivity to a higher reliability as the driving time is shorter.

[0151] In addition, each piece of driving data included in the driving history data 108a may indicate the stop time and the number of stops. The stop time may be the time when the vehicle 2 most recently stopped at the timing when the driving data is obtained. The number of stops may be the number of times the vehicle 2 stopped in a certain period before the timing when the driving data is obtained. In such a case, the update processing unit 106 may update the reliability of the sensitivity to a higher reliability as the stop time of the vehicle 2 indicated by the driving data when the calculated sensitivity is calculated is longer, and as the number of stops of the vehicle 2 is larger. As described above, when the vehicle 2 is stopped, an offset value used for offset correction of the gyro sensor 203 is determined. Therefore, the longer the stop time, and the larger the number of stops of the vehicle 2, the less likely it is that the offset value will deviate. As a result, since the accuracy of the calculated sensitivity increases as the stop time is longer, the reliability can be appropriately updated by updating the reliability of the sensitivity to a higher reliability as the stop time is longer. Similarly, since the accuracy of the calculated sensitivity increases as the number of stops of the vehicle is larger, the reliability can be appropriately updated by updating the reliability of the sensitivity to a higher reliability as the number of stops is larger.

[0152] In addition, when the engine of the vehicle 2 starts, the update processing unit 106 may decrease each reliability shown in the sensitivity table 107c more as the elapsed time since the engine stopped is longer. The update processing unit 106 may obtain information indicating the elapsed time from a device external to the display device 100. For example, the update processing unit 106 may decrease each reliability by the same value, or may decrease each reliability by the same ratio. As the elapsed time since the engine stopped is longer, the sensitivity of the gyro sensor 203 is more likely to have changed significantly from its sensitivity before the stop. Therefore, by decreasing each reliability shown in the sensitivity table more as the elapsed time since the engine stopped is longer, those reliabilities can be appropriately managed.

[0153] When the sensitivity correction unit 102 uses the sensitivity table 107c shown in FIG. 16, it refers to the reliability shown in the sensitivity table 107c and determines the sensitivity used for sensitivity correction of the angular velocity based on the reliability. That is, in the sensitivity table 107c, the sensitivity correction unit 102 determines whether or not the determination target reliability, which is the reliability associated with the temperature range including the ambient temperature detected by the temperature sensor 204, is equal to or greater than a threshold value. When the determination target reliability is equal to or greater than the threshold value, the sensitivity correction unit 102 acquires the sensitivity having the determination target reliability from the sensitivity table storage unit 107 and uses the acquired sensitivity for sensitivity correction of the angular velocity. On the other hand, when the determination target reliability is less than the threshold value, the sensitivity correction unit 102 derives an alternative sensitivity and uses the alternative sensitivity for sensitivity correction of the angular velocity. Thereby, an adaptive process according to the reliability of the sensitivity can be performed. That is, when the determination target reliability is low, instead of the sensitivity having the determination target reliability, an alternative sensitivity is used for correction of the angular velocity, so that correction based on an unreliable sensitivity can be suppressed and the possibility of performing appropriate correction can be increased. Note that the threshold value of the determination target reliability described above may be, for example, 0.5.

[0154] FIG. 17 is a diagram showing an example of derivation of an alternative sensitivity in this modified example.

[0155] [1: Extrapolation (linear interpolation)] When the above-described reliability of the determination target is less than the threshold value, the sensitivity correction unit 102 acquires a first sensitivity and a second sensitivity, which are sensitivities having a reliability of not less than the threshold value, from the sensitivity table storage unit 107. That is, the sensitivity correction unit 102 reads out the first sensitivity and the second sensitivity associated with reliabilities of not less than the threshold value from the sensitivity table 107c. Then, the sensitivity correction unit 102 derives an alternative sensitivity by extrapolating or linearly interpolating the sensitivity based on the first sensitivity and the second sensitivity, the temperature ranges associated with the first sensitivity and the second sensitivity, respectively, and the temperature range associated with the reliability of the determination target. Thereby, when the reliability of the determination target is low, the possibility of deriving an alternative sensitivity having a higher reliability than the sensitivity having the reliability of the determination target can be increased by using the first sensitivity and the second sensitivity having a high reliability and the linearity of the sensitivity with respect to each temperature range. Therefore, by using such an alternative sensitivity for the sensitivity correction of the angular velocity, the possibility of performing appropriate correction can be increased.

[0156] In a specific example, the threshold value is 0.5. Also, the temperature range including the ambient temperature detected by the temperature sensor 204 at the present time is "-10 to 0°C". In this case, the sensitivity correction unit 102 determines whether the reliability of the determination target, which is the reliability associated with the temperature range "-10 to 0°C" (that is, 0.3), is not less than the threshold value "0.5". At this time, the sensitivity correction unit 102 determines that the reliability of the determination target is not more than the threshold value, that is, the reliability of the determination target is less than the threshold value. As a result, the sensitivity correction unit 102 reads out the first sensitivity "0.98" and the second sensitivity "0.97" associated with reliabilities of not less than the threshold value "0.5" from the sensitivity table 107c. Then, the sensitivity correction unit 102 performs extrapolation or linear interpolation of the sensitivity based on the first sensitivity "0.98" and the second sensitivity "0.97", the temperature ranges "20 to 30°C" and "10 to 20°C" associated with the first sensitivity "0.98" and the second sensitivity "0.97", respectively, and the temperature range "-10 to 0°C" associated with the reliability of the determination target "0.3".

[0157] In a more specific example, the sensitivity correction unit 102 first calculates the median value of each of the above temperature ranges “20 to 30 °C”, “10 to 20 °C” and “-10 to 0 °C”. That is, the sensitivity correction unit 102 calculates the median values “25 °C”, “15 °C” and “-5 °C”. Then, the sensitivity correction unit 102 derives an alternative sensitivity “0.95” by (first sensitivity “0.98” - second sensitivity “0.97”) / (median value “25” - median value “15”)×(median value “-5 °C” - median value “15 °C”) + second sensitivity “0.97”. This alternative sensitivity “0.95” is used for the sensitivity correction of the angular velocity instead of the sensitivity “0.8” in the temperature range “-10 to 0 °C”. In the example shown in FIG. 17, the alternative sensitivity is derived by extrapolation, but the alternative sensitivity may also be derived by interpolation. For example, if the sensitivity in the temperature range “-20 to -10 °C” and the reliability above the threshold for that sensitivity are shown in the sensitivity table 107c, the sensitivity correction unit 102 derives the alternative sensitivity by interpolation using that temperature range “-20 to -10 °C” and its sensitivity. That is, the sensitivity correction unit 102 derives the alternative sensitivity in the temperature range “-10 to 0 °C” by interpolation using the temperature range “-20 to -10 °C” and its sensitivity, and the temperature range “10 to 20 °C” and its sensitivity.

[0158] Further, the sensitivity correction unit 102 may select each of the top two temperature ranges close to the temperature range “-10 to 0 °C” associated with the determination target reliability “0.3” as the temperature ranges used for extrapolation, interpolation or linear interpolation. Note that the number of selected temperature ranges is not limited to two, and may be three or more.

[0159] [2: Weighted average using reliability] When the above-described reliability of the determination target is less than the threshold value, the sensitivity correction unit 102 acquires from the sensitivity table storage unit 107 a low-reliability sensitivity which is the sensitivity having the reliability of the determination target and a high-reliability sensitivity which is the sensitivity having a reliability equal to or higher than the threshold value. That is, the sensitivity correction unit 102 reads the low-reliability sensitivity and the high-reliability sensitivity from the sensitivity table 107c. Then, the sensitivity correction unit 102 derives an alternative sensitivity by weighted averaging the low-reliability sensitivity and the high-reliability sensitivity using weights based on the respective reliabilities of the low-reliability sensitivity and the high-reliability sensitivity. Thereby, when the reliability of the determination target is low, by using the high-reliability sensitivity, it is possible to increase the possibility of deriving an alternative sensitivity having a reliability higher than the low-reliability sensitivity having the reliability of the determination target. Therefore, by using such an alternative sensitivity for the sensitivity correction of the angular velocity, it is possible to increase the possibility of performing appropriate correction.

[0160] In a specific example, as described above, the threshold value is 0.5. Also, the temperature range including the ambient temperature detected by the temperature sensor 204 at the current time is "-10 to 0°C". In this case, the sensitivity correction unit 102 determines that the reliability of the determination target (that is, 0.3), which is the reliability associated with the temperature range "-10 to 0°C", is less than the threshold value "0.5". As a result, the sensitivity correction unit 102 reads from the sensitivity table 107c a low-reliability sensitivity "0.8" which is the sensitivity having the reliability of the determination target "0.3" and a high-reliability sensitivity "0.97" which is the sensitivity having a reliability equal to or higher than the threshold value "0.5". Then, the sensitivity correction unit 102 derives an alternative sensitivity by weighted averaging the low-reliability sensitivity "0.8" and the high-reliability sensitivity "0.97" using weights based on the respective reliabilities "0.3" and "0.8" of the low-reliability sensitivity "0.8" and the high-reliability sensitivity "0.97". That is, the sensitivity correction unit 102 derives an alternative sensitivity "0.923636" by (low-reliability sensitivity "0.8" × reliability "0.3" + high-reliability sensitivity "0.97" × reliability "0.8") / (reliability "0.3" + reliability "0.8"). This alternative sensitivity "0.923636" is used for the sensitivity correction of the angular velocity instead of the sensitivity "0.8" in the temperature range "-10 to 0°C". Note that the alternative sensitivity "0.923636" may be treated as "0.92" in consideration of significant figures.

[0161] Further, the sensitivity correction unit 102 may use, for weighted average, the high-sensitivity value associated with the temperature range closest to the temperature range "-10 to 0°C" of the determination target reliability "0.3" among the one or more high-reliability sensitivities shown in the sensitivity table 107c.

[0162] [3: Combination of extrapolation (linear interpolation) and weighted average using reliability] The sensitivity correction unit 102 may derive an alternative sensitivity by a combination of extrapolation (linear interpolation) and weighted average using reliability. Specifically, the sensitivity correction unit 102 first derives a provisional alternative sensitivity "0.95" for the temperature range "-10 to 0°C" by the above-described extrapolation or linear interpolation. Further, the sensitivity correction unit 102 derives the reliability of the provisional alternative sensitivity "0.95". For the derivation of this reliability, for example, the reliabilities "0.8" and "0.9" associated with the temperature ranges "10 to 20°C" and "20 to 30°C" used for the extrapolation or linear interpolation are used. That is, the sensitivity correction unit 102 derives the reliability "0.85" of the provisional alternative sensitivity "0.95" by (reliability "0.8" + reliability "0.9") / 2. Next, the sensitivity correction unit 102 derives the final alternative sensitivity by weighted average using the provisional alternative sensitivity "0.95" and the reliability "0.85" of the alternative sensitivity "0.95" instead of the high-reliability sensitivity "0.97" and the reliability "0.8" of the high-reliability sensitivity "0.97". That is, the sensitivity correction unit 102 derives the final alternative sensitivity "0.91087" by (low-reliability sensitivity "0.8" × reliability "0.3" + provisional alternative sensitivity "0.95" × reliability "0.85") / (reliability "0.3" + reliability "0.85"). This final alternative sensitivity "0.91087" is used for the sensitivity correction of the angular velocity instead of the sensitivity "0.8" for the temperature range "-10 to 0°C". Note that the alternative sensitivity "0.91087" may be treated as "0.91" considering significant figures.

[0163] Further, when the reliability to be determined is less than the threshold value and higher than other reliabilities shown in the sensitivity table 107c, the sensitivity correction unit 102 may use the sensitivity having the reliability to be determined as the substitute sensitivity. That is, in this case, even if the reliability to be determined is low, the sensitivity correction unit 102 directly uses the sensitivity having the reliability to be determined for the sensitivity correction of the angular velocity. As a result, when the reliability to be determined is low and, for example, all other reliabilities shown in the sensitivity table 107c are lower than the reliability to be determined, the sensitivity having the reliability to be determined is directly used as the substitute sensitivity. Therefore, by using other reliabilities shown in the sensitivity table 107c, it is possible to suppress deriving a less reliable sensitivity and correcting the angular velocity using such a sensitivity.

[0164] Also, when updating the sensitivity of the sensitivity table 107c in this modified example, the update processing unit 106 may use the weighted average as described above. That is, when the update processing unit 106 updates the sensitivity associated with the temperature range in the sensitivity table 107c, it derives the calculated reliability of the sensitivity based on the driving data as the calculated reliability. Then, the update processing unit 106 derives the updated sensitivity by performing a weighted average of the sensitivity and the calculated sensitivity using the weights based on the reliability associated with the temperature range in the sensitivity table 107c and the calculated reliability. For example, the update processing unit 106 derives the calculated reliability by the same method as the update of the reliability described above. Also, as an example, the reliability associated with the temperature range is "T", the calculated reliability is "Tc", the sensitivity associated with the temperature range is "G", and the calculated sensitivity is "Gc". In such a case, the update processing unit 106 derives the updated sensitivity by a weighted average such as (G×T + Gc×Tc) / (T + Tc). Thereby, the sensitivity can be appropriately updated using the reliability of the calculated sensitivity (i.e., the calculated reliability) and the reliability of the sensitivity shown in the sensitivity table 107c. When the sensitivity shown in the sensitivity table 107c is updated in this way, the reliability "T" of the sensitivity may be updated using the reliability "T" and the calculated reliability "Tc". For example, the update processing unit 106 may derive the updated reliability by the formula "1 - (1 - T)×(1 - Tc)" and replace the reliability "T" shown in the sensitivity table 107c with the updated reliability.

[0165] In the above example, even if the reliability of the sensitivity shown in the sensitivity table 107c is low, the display device 100 derives an alternative sensitivity and displays the display object 10. However, it may be difficult to display the display object 10 indicating an appropriate orientation even when the angular velocity is corrected by the alternative sensitivity. Alternatively, if there is not even one sensitivity having a reliability equal to or higher than the threshold value shown in the sensitivity table 107c, it may be difficult to derive the alternative sensitivity. In such a case, the display device 100 may not display the display object 10. That is, when the determination target reliability is less than the threshold value, the display unit 110 may prohibit the output of the image that is the display object 10. Thereby, when the determination target reliability is low, the output of the display object 10 based on the sensitivity having such a determination target reliability is prohibited, so that the display of an inappropriate display object 10 can be suppressed. Note that when the determination target reliability is less than the threshold value and the turning angle of the vehicle 2 exceeds a predetermined angle, the display unit 110 may prohibit the output of the display object 10 after the turning.

[0166] Alternatively, when the determination target reliability is less than the threshold value, the display unit 110 may change the display mode of the image that is the display object 10 and output the image in the changed display mode. In the above example, the display object 10 is displayed in the display mode of the AR content. The display unit 110 changes the display mode of the AR content to the display mode of the non-AR content. In other words, the display unit 110 changes the display mode for AR to the display mode for non-AR. The display mode of the AR content is a display mode in which a triangular image is parallel to the road surface and is disposed at a position separated from the road surface by a predetermined distance upward. The display mode of the non-AR content is a display mode in which the triangular image is not parallel to the road surface and the positional relationship between the triangle and the background including the road surface is not determined. Thereby, the display of an inappropriate image due to the display mode of the AR content can be suppressed. Note that when the determination target reliability is less than the threshold value and the turning angle of the vehicle 2 exceeds a predetermined angle, the display unit 110 may change the display mode of the display object 10 after the turning and display the display object 10 in the changed display mode.

[0167] FIG. 18 is a flowchart showing an example of the sensitivity correction process in this modified example. That is, the flowchart of FIG. 18 shows the process of step S210 in FIG. 12 in detail.

[0168] First, the sensitivity correction unit 102 refers to the sensitivity table 107c stored in the sensitivity table storage unit 107 (step S211). Next, the sensitivity correction unit 102 grasps the ambient temperature of the gyro sensor 203 indicated by the temperature signal acquired in step S202 of FIG. 12, and acquires the reliability associated with the temperature range including the ambient temperature in the sensitivity table 107c (step S214). That is, the sensitivity correction unit 102 reads out the reliability associated with the ambient temperature detected by the temperature sensor 204 from the sensitivity table 107c.

[0169] Then, the sensitivity correction unit 102 determines whether or not the reliability acquired in step S214 is equal to or greater than a threshold value (step S215). This reliability is the above-described determination target reliability. Here, when the sensitivity correction unit 102 determines that the determination target reliability is equal to or greater than the threshold value (YES in step S215), the sensitivity correction unit 102 acquires the sensitivity associated with the detected ambient temperature in the sensitivity table 107c (step S212). Next, the sensitivity correction unit 102 calculates the sensitivity-corrected angular velocity by multiplying the angular velocity subjected to offset correction in step S203 of FIG. 12 by the sensitivity acquired in step S212 (step S217).

[0170] On the other hand, when the sensitivity correction unit 102 determines in step S215 that the determination target reliability is less than the threshold value (NO in step S215), the sensitivity correction unit 102 derives an alternative sensitivity (step S216). That is, the sensitivity correction unit 102 derives the sensitivity corresponding to the detected ambient temperature as the alternative sensitivity using the sensitivity associated with the reliability equal to or greater than the threshold value in the sensitivity table 107c. Then, in step S217, the sensitivity correction unit 102 calculates the sensitivity-corrected angular velocity by multiplying the angular velocity by the alternative sensitivity derived in step S216.

[0171] (Other aspects) As described above, the display device of the present disclosure has been described based on embodiments and modifications thereof. However, the present disclosure is not limited to those embodiments and modifications. As long as the gist of the present disclosure is not deviated from, various modifications conceived by those skilled in the art applied to the above embodiments and modifications may also be included in the present disclosure.

[0172] For example, in the above embodiments and modifications, a triangular image is displayed as the display object 10. However, the shape of the display object 10 is not limited to a triangle and may be any shape such as an arrowhead shape or an arrow shape. Further, the display object 10 may be in the form of a long carpet and may be displayed so as to overlap the road surface. Further, although the display object 10 is displayed to guide the vehicle 2 to the destination, as long as it is displayed based on the orientation of the vehicle 2 (i.e., the third vehicle estimated orientation), it may be displayed for other purposes or uses. For example, the display object 10 may be an image indicating the orientation of the vehicle 2 itself.

[0173] In the above embodiments, each component may be configured by dedicated hardware or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU (Central Processing Unit) or a processor reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory. For example, a plurality of components other than the sensitivity table storage unit 107, the data storage unit 108, and the display unit 110 included in the display device 100 may be realized by one or more processors. These one or more processors execute the respective processes of the above-described plurality of components by executing a computer program stored in a recording medium. Here, the software program or the computer program for realizing the display device 100 and the like of the above embodiments causes a computer to execute each step included in the flowcharts shown in FIGS. 8 to 13 and FIG. 18, for example.

[0174] Note that the following cases are also included in the present disclosure.

[0175] (1) Specifically, at least one of the above devices is a computer system composed of a microprocessor, ROM (Read Only Memory), RAM (Random Access Memory), hard disk unit, display unit, keyboard, mouse, etc. A computer program is stored in the RAM or hard disk unit. When the microprocessor operates according to the computer program, at least one of the above devices achieves its function. Here, the computer program is composed of a combination of a plurality of instruction codes indicating instructions to the computer in order to achieve a predetermined function.

[0176] (2) Part or all of the components constituting at least one of the above devices may be composed of one system LSI (Large Scale Integration). A system LSI is a super multifunctional LSI manufactured by integrating a plurality of components on one chip, and specifically, it is a computer system including a microprocessor, ROM, RAM, etc. A computer program is stored in the RAM. When the microprocessor operates according to the computer program, the system LSI achieves its function.

[0177] (3) Part or all of the components constituting at least one of the above devices may be composed of an IC card or a single module detachable from the device. The IC card or module is a computer system composed of a microprocessor, ROM, RAM, etc. The IC card or module may include the above super multifunctional LSI. When the microprocessor operates according to the computer program, the IC card or module achieves its function. This IC card or this module may have tamper resistance.

[0178] (4) The present disclosure may be the method described above. It may also be a computer program that realizes these methods by a computer, or a digital signal consisting of a computer program.

[0179] Further, the present disclosure may be a computer program or a digital signal recorded on a computer-readable recording medium, such as a flexible disk, a hard disk, a CD (Compact Disc)-ROM, a DVD, a DVD-ROM, a DVD-RAM, a BD (Blu-ray (registered trademark) Disc), a semiconductor memory, etc. It may also be a digital signal recorded on these recording media.

[0180] Further, the present disclosure may be a computer program or a digital signal transmitted via a telecommunication line, a wireless or wired communication line, a network represented by the Internet, data broadcasting, etc.

[0181] Further, it may be implemented by another independent computer system by recording and transferring a program or a digital signal to a recording medium, or by transferring a program or a digital signal via a network or the like.

Industrial Applicability

[0182] The display device of the present disclosure has an effect of being able to display an appropriate image for a user while suppressing the influence of the ambient temperature of the angular velocity sensor, and can be applied to, for example, an in-vehicle head-up display.

Explanation of Signs

[0183] 1 User 2, 3, 4 Vehicle 2a Windshield 2b Dashboard 10, 11 Display Object 100 Display Device 101 Offset correction unit 102 Sensitivity correction unit 103 First azimuth estimation unit 104 Second azimuth estimation unit 105 Azimuth correction unit 106 Update processing unit 107 Sensitivity table storage unit 107a, 107b, 107c Sensitivity tables 108 Data storage unit 108a Travel history data 108b Sensitivity history data 109 Drawing unit 110 Display unit 201 Vehicle speed output unit 202 Satellite positioning system 203 Gyro sensor 204 Temperature sensor 205 Navigation unit d1, d2 Display ranges

Claims

1. Obtaining the ambient temperature of an angular velocity sensor mounted on a vehicle detected by a temperature sensor, obtaining the sensitivity of the angular velocity sensor associated with a temperature range including the ambient temperature from a recording medium, and correcting the angular velocity detected by the angular velocity sensor according to the obtained sensitivity; a sensitivity correction unit; A first azimuth estimation unit that estimates the azimuth in which the vehicle is facing as a first vehicle estimated azimuth based on the angular velocity corrected by the sensitivity correction unit; A second azimuth estimation unit that estimates the azimuth in which the vehicle is facing as a second vehicle estimated azimuth based on the angular velocity detected by the angular velocity sensor; An azimuth correction unit that derives a third vehicle estimated azimuth by correcting the first vehicle estimated azimuth using the position of the vehicle measured by a satellite positioning system and the speed of the vehicle; A display unit that displays an image corresponding to the third vehicle estimated azimuth; When the vehicle turns after passing through a first point and passes through a second point, based on the change amount of the second vehicle estimated azimuth estimated at each of the first point and the second point, and the change amount of the third vehicle estimated azimuth derived at each of the first point and the second point, calculating the sensitivity of the angular velocity sensor as a calculated sensitivity, and updating the sensitivity stored in the recording medium in association with the temperature range using the calculated sensitivity; an update processing unit; Comprising: The azimuth correction unit: (a) The first position of the vehicle measured by the satellite positioning system; (b) The second position of the vehicle measured by the satellite positioning system when the vehicle moves from the first position; (c) Based on the first position, the azimuth of the vehicle at the first position, the angular velocity detected by the angular velocity sensor, and the estimated position of the vehicle when the second position is measured, which is estimated based on dead reckoning using the speed of the vehicle, Estimating the deviation of the azimuth of the vehicle; Correcting the first vehicle estimated azimuth according to the deviation of the azimuth of the vehicle; A display device.

2. The azimuth correction unit: Estimating the angle formed by the straight line connecting the first position and the second position and the straight line connecting the first position and the estimated position as the deviation of the azimuth of the vehicle; The display device according to Claim 1.

3. The recording medium stores a sensitivity table indicating sensitivities associated with a plurality of different temperature ranges respectively; The sensitivity correction unit acquires, from the recording medium, the sensitivity associated with a temperature range including the ambient temperature detected by the temperature sensor in the sensitivity table, and uses the acquired sensitivity for correcting the angular velocity. The display device according to claim 1 or 2.

4. The recording medium stores a sensitivity table indicating the sensitivity associated with each of a plurality of different temperature ranges and the reliability of the sensitivity. The sensitivity correction unit determines whether a determination target reliability, which is the reliability associated with a temperature range including the ambient temperature detected by the temperature sensor in the sensitivity table, is equal to or greater than a threshold value, If the determination target reliability is equal to or greater than the threshold value, acquires, from the recording medium, the sensitivity having the determination target reliability, and uses the acquired sensitivity for correcting the angular velocity. If the determination target reliability is less than the threshold value, derives an alternative sensitivity and uses the alternative sensitivity for correcting the angular velocity. The display device according to claim 1 or 2.

5. The sensitivity correction unit If the determination target reliability is less than the threshold value, acquires, from the recording medium, a low-reliability sensitivity, which is the sensitivity having the determination target reliability, and a high-reliability sensitivity, which is the sensitivity having a reliability equal to or greater than the threshold value, and derives the alternative sensitivity by weighted averaging of the low-reliability sensitivity and the high-reliability sensitivity using weights based on the respective reliabilities of the low-reliability sensitivity and the high-reliability sensitivity. The display device according to claim 4.

6. The sensitivity correction unit If the determination target reliability is less than the threshold value, acquires, from the recording medium, a first sensitivity and a second sensitivity, which are sensitivities having a reliability equal to or greater than the threshold value, and derives the alternative sensitivity by extrapolation, interpolation, or linear interpolation of the sensitivity based on the first sensitivity and the second sensitivity, the temperature ranges associated with the first sensitivity and the second sensitivity, and the temperature range associated with the determination target reliability. The display device according to claim 4.

7. The sensitivity correction unit If the determination target reliability is less than the threshold value and is higher than other reliabilities shown in the sensitivity table, uses the sensitivity having the determination target reliability as the alternative sensitivity. The display device according to any one of claims 4 to 6.

8. The update processing unit When updating the sensitivity shown in the sensitivity table using the calculated sensitivity, the reliability of the sensitivity shown in the sensitivity table is further updated. The display device according to any one of claims 4 to 7. **Claim 9** The update processing unit In the update of the reliability of the sensitivity The reliability of the sensitivity is updated according to the driving data indicating the driving state of the vehicle when the calculated sensitivity is calculated. The display device according to claim 8. **Claim 10** The update processing unit The greater the angle of turning of the vehicle indicated by the driving data, the higher the reliability of the sensitivity is updated. The display device according to claim 9. **Claim 11** The update processing unit The longer the distance of each of the two straight-line sections indicated by the driving data, the higher the reliability of the sensitivity is updated. The two straight-line sections are sections in which the vehicle travels straight at the respective times before and after the vehicle turns. The display device according to claim 9 or 10. **Claim 12** The update processing unit The shorter the driving time of the vehicle indicated by the driving data, the higher the reliability of the sensitivity is updated. The display device according to any one of claims 9 to 11. **Claim 13** The update processing unit The longer the parking time of the vehicle indicated by the driving data and the more the number of parking times of the vehicle, the higher the reliability of the sensitivity is updated. The display device according to any one of claims 9 to 12. **Claim 14** The update processing unit When the engine of the vehicle starts, the longer the elapsed time since the engine stopped, the greater the reduction in each reliability shown in the sensitivity table. The display device according to any one of claims 4 to 13. **Claim 15** The update processing unit When updating the sensitivity associated with the temperature range in the sensitivity table Based on the driving data, the reliability of the calculated sensitivity is derived as the calculated reliability. The updated sensitivity is derived by the weighted average of the sensitivity and the calculated sensitivity using the weights based on the reliability associated with the temperature range in the sensitivity table and the calculated reliability. The display device according to any one of claims 9 to 13. **Claim 16** The display unit When the determination target reliability is less than the threshold value Prohibit the output of the image. The display device according to any one of claims 4 to 15. **Claim 17** The display unit When the determination target reliability is less than the threshold value, change the display mode of the image and output the image in the changed display mode. The display device according to any one of claims 4 to 15.

18. A display method in which a computer displays an image, obtain the ambient temperature of the angular velocity sensor mounted on the vehicle detected by a temperature sensor, obtain the sensitivity of the angular velocity sensor associated with the temperature range including the ambient temperature from a recording medium, and correct the angular velocity detected by the angular velocity sensor according to the obtained sensitivity. Estimate the direction in which the vehicle is facing as a first vehicle estimated direction based on the angular velocity corrected according to the sensitivity. Based on the angular velocity detected by the angular velocity sensor, the direction in which the vehicle is facing is estimated as a second vehicle estimated direction. Derive a third vehicle estimated direction by correcting the first vehicle estimated direction using the position of the vehicle measured by a satellite positioning system and the speed of the vehicle. Display an image corresponding to the third vehicle estimated direction on a display unit. When the vehicle turns after passing through a first point and passes through a second point, calculate the sensitivity of the angular velocity sensor as a calculated sensitivity based on the change amount of the second vehicle estimated direction estimated at each of the first point and the second point and the change amount of the third vehicle estimated direction derived at each of the first point and the second point, and update the sensitivity stored in the recording medium in association with the temperature range using the calculated sensitivity. In the correction of the first vehicle estimated direction, (a) the first position of the vehicle measured by the satellite positioning system, (b) the second position of the vehicle measured by the satellite positioning system when the vehicle moves from the first position, (c) based on the first position, the direction of the vehicle at the first position, the angular velocity detected by the angular velocity sensor, and the estimated position of the vehicle when the second position is measured based on dead reckoning using the speed of the vehicle, estimate the deviation of the vehicle's direction, correct the first vehicle estimated direction according to the deviation of the vehicle's direction. Display method.

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