WO2024100877A1

WO2024100877A1 - Electronic device for vehicles

Info

Publication number: WO2024100877A1
Application number: PCT/JP2022/042046
Authority: WO
Inventors: 雄基鶴田
Original assignee: 日立Astemo株式会社
Priority date: 2022-11-11
Filing date: 2022-11-11
Publication date: 2024-05-16

Abstract

The purpose of the present invention is to provide an electronic device for vehicles that is capable of optimizing the frequency of rewriting, in a memory, a correction value for correcting optical axis deviation. An electronic device 1 for vehicles changes, on the basis of a change amount of a correction value for correcting optical axis deviation of cameras 11, 12 in image data taken by the cameras 11, 12, a rewriting frequency that is a frequency at which the correction value is stored in a memory 50. The electronic device 1 for vehicles may comprise the cameras 11, 12 and an image processing device 20. The image processing device 20 may have: the memory 50; an image data acquisition unit 31 that acquires the image data from the cameras 11, 12; a calibration unit 32 that carries out calibration including calculation of the optical axis deviation correction value; a calculation unit 33 that calculates the change amount of the calculated optical axis deviation correction value; a determination unit 34 that determines the rewriting frequency on the basis of the change amount of the calculated optical axis deviation correction value; and a control unit 35 that stores, in the memory 50, the optical axis deviation correction value in accordance with the determined rewriting frequency.

Description

Car Electronics

The present invention relates to electronic devices for vehicles.

In a stereo camera device, which is an electronic device for vehicles, optical axis misalignment occurs over time. Optical axis misalignment occurs when the central axis of the camera lens shifts from its initial position, or when the central axis of the lens shifts between the left and right cameras. If the optical axis misalignment increases, the sensing accuracy of the stereo camera device deteriorates. Therefore, the stereo camera device periodically corrects the optical axis misalignment, stores the correction value for the optical axis misalignment in non-volatile memory, and backs up the correction value.

For example, Patent Document 1 discloses a camera calibration device that updates the camera parameters stored in a parameter storage unit and also includes a parameter update unit that updates the vehicle movement parameters. This parameter update unit has a function of finding optimal solutions for the camera parameters and vehicle movement parameters so that the positions of feature points in the images of each camera, which are transformed by a homography matrix, match the flow of feature points found by the road surface flow extraction unit.

JP 2020-107938 A

In the non-volatile memory in which the optical axis misalignment correction value is stored, it is necessary to take care that the number of times data is rewritten over a lifetime does not exceed the rewrite limit. If the number of rewrites exceeds the rewrite limit, data corruption may occur in the non-volatile memory, and there is a concern that the reliability of data retention in the non-volatile memory may be compromised. The camera calibration device disclosed in Patent Document 1 does not take into consideration the frequency of rewriting camera parameters, and there is a concern that the memory rewrite limit may be exceeded.

The present invention has been made in consideration of the above, and aims to provide an electronic device for a vehicle that can optimize the frequency with which the correction value for correcting optical axis misalignment is rewritten to memory.

In order to solve the above problem, the in-vehicle electronic device of the present invention is characterized in that the rewrite frequency, which is the frequency at which a correction value for correcting the optical axis misalignment of a camera is stored in memory in image data captured by the camera, is changed based on the amount of change in the correction value.

According to the present invention, it is possible to provide an electronic device for a vehicle that is capable of optimizing the frequency at which a correction value for correcting an optical axis deviation is rewritten in a memory.
Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments.

FIG. 1 is a diagram showing a configuration of a vehicle electronic device according to a first embodiment. FIG. 13 is a diagram for explaining optimization of rewrite frequency. 11 is a graph showing a transition of the optical axis deviation correction value when the amount of change in the optical axis deviation correction value is small. 4 is a graph showing the relationship between the change amount of the optical axis deviation correction value and the threshold value in the case shown in FIG. 3 . 11 is a graph showing a transition of the optical axis deviation correction value when the amount of change in the optical axis deviation correction value is large. 6 is a graph showing the relationship between the change amount of the optical axis deviation correction value and the threshold value in the case shown in FIG. 5 . 11 is a flowchart showing a process of optimizing a rewrite frequency according to the first embodiment. 13 is a graph showing threshold values set in a determination unit according to the second embodiment; 13 is a graph showing an extension time function set in a determination unit according to the third embodiment. 13 is a graph showing a shortened time function set in a determination unit according to the third embodiment. FIG. 13 is a diagram showing the configuration of a vehicle electronic device according to a fourth embodiment. 13 is a table for explaining optimization of rewrite frequency according to the fourth embodiment; 13 is a graph showing an extension time function set in a determination unit according to the fourth embodiment. 13 is a graph showing a shortened time function set in a determination unit according to the fourth embodiment; 13 is a flowchart showing a process of optimizing a rewrite frequency according to a fourth embodiment. 13 is a graph showing an extension time function set in a determination unit according to the fifth embodiment. 13 is a graph showing a shortened time function set in a determination unit according to the fifth embodiment.

The following describes embodiments of the present invention with reference to the drawings. Note that components with the same reference numerals in each embodiment have the same functions in each embodiment unless otherwise specified, and the description thereof will be omitted.

[Example 1]
Fig. 1 is a diagram showing a configuration of an in-vehicle electronic device 1 according to the embodiment 1. Fig. 2 is a diagram for explaining optimization of the rewrite frequency.

The car electronic device 1 is a type of sensor device that is mounted on a vehicle and monitors the surroundings of the vehicle. The car electronic device 1 is a sensor device that has an optical system such as a lens or a mirror. The car electronic device 1 may be a monocular camera device or a stereo camera device equipped with multiple cameras. In this embodiment, the car electronic device 1 will be described as being a stereo camera device.

The car electronic device 1 detects objects around the vehicle and measures the distance to the objects by utilizing the parallax of overlapping areas of image data captured by

multiple cameras

11, 12 arranged at a predetermined horizontal interval. The car electronic device 1 shown in FIG. 1 includes the

cameras

11, 12 and an image processing device 20 that processes the image data captured by the

cameras

11, 12.

The image processing device 20 is configured, for example, by a computer system equipped with an arithmetic processing device 30 including a CPU, RAM, and ROM, a data storage device 40, and a memory 50. The image processing device 20 realizes various functions of the image processing device 20 by the CPU executing programs stored in the ROM.

As shown in FIG. 2, the calculation processing device 30 changes the frequency (hereinafter also referred to as the "rewrite frequency") of storing in the memory 50 a correction value (hereinafter also referred to as the "optical axis shift correction value") for correcting the optical axis shift of the

cameras

11, 12 in the image data captured by the

cameras

11, 12, based on the amount of change over time in the optical axis shift correction value. FIG. 2 shows that when the optical axis shift correction value becomes smaller over time, the frequency of rewriting the optical axis shift correction value in the memory 50 is decreased over time.

The calculation processing device 30 has an image data acquisition unit 31, a calibration unit 32, a calculation unit 33, a determination unit 34, and a control unit 35.

The image data acquisition unit 31 acquires image data from the

cameras

11 and 12. The calibration unit 32 performs camera calibration, including the calculation of an optical axis shift correction value, using the image data acquired by the image data acquisition unit 31. The camera calibration can be performed by a known method. The calibration unit 32 stores the calculated optical axis shift correction value in the data storage device 40. The data storage device 40 is composed of a volatile memory.

The calculation unit 33 calculates the amount of change in the optical axis shift correction value stored in the data storage device 40. The determination unit 34 determines the rewrite frequency based on the amount of change in the optical axis shift correction value calculated by the calculation unit 33. Details of the calculation unit 33 and the determination unit 34 will be described later with reference to Figures 3 to 6.

The control unit 35 saves the optical axis deviation correction value stored in the data storage device 40 in the memory 50 according to the rewrite frequency determined by the determination unit 34. The memory 50 is composed of a non-volatile memory. In particular, the memory 50 may be composed of a NAND type non-volatile memory. Although the NAND type non-volatile memory has fewer rewrite count limitations than the NOR type, it is cheaper than the NOR type.

Figure 3 is a graph showing the progress of the optical axis deviation correction value when the change in the optical axis deviation correction value is small. The vertical axis of Figure 3 shows the optical axis deviation correction value, and the horizontal axis of Figure 3 shows time.

If the optical axis shift correction value at time _tn is x( _tn ) and the optical axis shift correction value at time _tn+1 is x(tn ₊₁ ), the change amount Δx in the optical axis shift correction value is expressed as the difference between x( _tn+1 ) and x( _tn ). The calculation unit 33 calculates the change amount Δx in the optical axis shift correction value using formula (1).
Δx=x(t _n+1 )−x(t _n ) …(1)

FIG. 4 is a graph showing the relationship between the amount of change in the optical axis deviation correction value and the threshold value in the case shown in FIG. 3. The vertical axis of FIG. 4 shows the amount of change in the optical axis deviation correction value, and the horizontal axis of FIG. 4 shows time.

4 shows that the change amount Δx of the optical axis shift correction value at time t _n+1 is within the range of the threshold values -α _th to α _th . The fact that the change amount Δx of the optical axis shift correction value is within the range of the threshold values -α _th to α _th satisfies the condition of formula (2), and indicates that the magnitude of the change amount Δx is less than the threshold value α _th . The threshold values -α _th and α _th are preset in the determination unit 34.

When the change amount Δx of the optical axis shift correction value satisfies the condition of formula (2), the determination unit 34 extends the rewrite interval tw, which is the time interval for saving the optical axis shift correction value in the memory 50, by the extension time n [min] as shown in formula (3), to set the extended rewrite interval tw'. This enables the determination unit 34 to make the frequency of rewriting the optical axis shift correction value in the memory 50 lower than before the change. The extension time n is the change amount of the rewrite interval tw.
−α _th <Δx<α _th ... (2)
tw' = tw + n ... (3)

FIG. 5 is a graph showing the change in the optical axis deviation correction value when the change in the optical axis deviation correction value is large. The vertical axis of FIG. 5 shows the optical axis deviation correction value, and the horizontal axis of FIG. 5 shows time.

If the optical axis shift correction value at time _tn is x( _tn ) and the optical axis shift correction value at time _tn+1 is x( _tn+1 ), the change amount Δx of the optical axis shift correction value is expressed as the difference between x( _tn+1 ) and x( _tn ), similar to the case shown in Fig. 3. The calculation unit 33 calculates the change amount Δx of the optical axis shift correction value using formula (1), similar to the case shown in Fig. 3.

FIG. 6 is a graph showing the relationship between the amount of change in the optical axis deviation correction value and the threshold value in the case shown in FIG. 5. The vertical axis of FIG. 6 shows the amount of change in the optical axis deviation correction value, and the horizontal axis of FIG. 6 shows time.

6 shows that the change amount Δx of the optical axis shift correction value at time t _n+1 is outside the range of the threshold values −α _th to α _th . The fact that the change amount Δx of the optical axis shift correction value is outside the range of the threshold values −α _th to α _th means that the condition of formula (2) is not satisfied, and the magnitude of the change amount Δx is equal to or greater than the threshold value α _th .

When the change amount Δx of the optical axis shift correction value does not satisfy the condition of formula (2), the determination unit 34 shortens the rewrite interval tw by the shortening time m [min] as shown in formula (4) to set the shortened rewrite interval tw''. This enables the determination unit 34 to increase the frequency of rewriting the optical axis shift correction value in the memory 50 compared to before the change. The shortening time m is the change amount of the rewrite interval tw.
tw''=tw+m... (4)

In this way, when the magnitude of the change amount Δx of the optical axis shift correction value is less than the threshold value α _th , the determination unit 34 extends the rewrite interval tw to reduce the frequency of rewriting the optical axis shift correction value to the memory 50. When the magnitude of the change amount Δx of the optical axis shift correction value is equal to or greater than the threshold value α _th , the determination unit 34 shortens the rewrite interval tw to increase the frequency of rewriting the optical axis shift correction value to the memory 50.

FIG. 7 is a flowchart showing the rewrite frequency optimization process according to the first embodiment.

In step S1, the calculation processing device 30 stores the optical axis deviation correction value x(t _n ) at time t _n in the data storage device 40.

In step S2, the calculation processing device 30 stores the optical axis deviation correction value x(t _n+1 ) at time t _n+1 in the data storage device 40.

In step S3, the calculation processing device 30 calculates the amount of change Δx in the stored optical axis deviation correction value.

In step S4, the arithmetic processing device 30 judges whether the calculated change amount Δx of the optical axis deviation correction value satisfies _-αth < Δx < _αth . If the change amount Δx satisfies _-αth < Δx < _αth , that is, if the magnitude of the change amount Δx is less than the threshold value _αth , the arithmetic processing device 30 proceeds to step S5. If the change amount Δx does not satisfy _-αth < Δx < _αth , that is, if the magnitude of the change amount Δx is equal to or greater than the threshold value _αth , the arithmetic processing device 30 proceeds to step S6.

In step S5, the calculation processing device 30 extends the rewrite interval tw.

In step S6, the calculation processing device 30 shortens the rewrite interval tw.

In step S7, the arithmetic processing device 30 rewrites the optical axis deviation correction value in the memory 50 after the extended or shortened rewrite interval tw' or tw'' has elapsed. In other words, the arithmetic processing device 30 saves the optical axis deviation correction value stored in the data storage device 40 in the memory 50 after the extended or shortened rewrite interval tw' or tw'' has elapsed. Thereafter, the arithmetic processing device 30 ends this process.

As described above, the vehicle electronic device 1 according to the first embodiment changes the rewrite frequency, which is the frequency at which the correction values for correcting the optical axis misalignment of the

cameras

11 and 12 in the image data captured by the

cameras

11 and 12 are stored in the memory 50, based on the amount of change in the correction values.

Therefore, the car electronic device 1 according to the first embodiment can reduce the rewrite frequency when the change amount of the optical axis shift correction value is small, for example, and therefore can reduce the number of rewrites of the memory 50. Therefore, the car electronic device 1 according to the first embodiment can suppress the number of rewrites of the memory 50 exceeding the rewrite limit, which can cause the data retention reliability of the memory 50 to be impaired. At the same time, the car electronic device 1 according to the first embodiment can increase the rewrite frequency when the change amount of the optical axis shift correction value is large, for example, and therefore can back up the latest optical axis shift correction value corresponding to the newest optical axis shift as much as possible. Therefore, the car electronic device 1 according to the first embodiment can correct the optical axis shift using the latest optical axis shift correction value, and therefore can suppress the deterioration of sensing accuracy due to the correction of the optical axis shift using the old optical axis shift correction value. In this way, the car electronic device 1 according to the first embodiment can optimize the rewrite frequency of the optical axis shift correction value to the memory 50 according to the change amount of the optical axis shift correction value. Therefore, according to the first embodiment, it is possible to provide a car electronic device 1 capable of optimizing the frequency of rewriting the correction value for correcting the optical axis shift to the memory 50.

Furthermore, the vehicle electronic device 1 according to the first embodiment includes

cameras

11 and 12, and an image processing device 20 that processes image data captured by the

cameras

11 and 12. The image processing device 20 includes a memory 50, an image data acquisition unit 31 that acquires image data from the

cameras

11 and 12, a calibration unit 32 that performs calibration including the calculation of an optical axis shift correction value, a calculation unit 33 that calculates the amount of change in the calculated optical axis shift correction value, a determination unit 34 that determines the rewrite frequency based on the amount of change in the calculated optical axis shift correction value, and a control unit 35 that stores the optical axis shift correction value in the memory 50 according to the determined rewrite frequency.

As a result, the in-vehicle electronic device 1 according to the first embodiment can optimize the rewrite frequency by incorporating the calculation unit 33, the determination unit 34, and the control unit 35 into the image processing device 20 of the existing stereo camera device. Therefore, the in-vehicle electronic device 1 according to the first embodiment can easily optimize the rewrite frequency of the optical axis deviation correction value in the memory 50.

Furthermore, in the vehicle electronic device 1 according to the first embodiment, when the magnitude of the change in the optical axis shift correction value is less than the threshold value, the decision unit 34 extends the rewrite interval, which is the time interval for storing the optical axis shift correction value in the memory 50, to reduce the rewrite frequency, and when the magnitude of the change in the optical axis shift correction value is equal to or greater than the threshold value, the decision unit 34 shortens the rewrite interval to increase the rewrite frequency.

As a result, the car electronic device 1 according to the first embodiment can reduce the number of times the memory 50 is rewritten to ensure reliable data retention, while backing up the latest optical axis shift correction value and reliably suppressing deterioration of sensing accuracy. Therefore, the car electronic device 1 according to the first embodiment can reliably optimize the frequency of rewriting the optical axis shift correction value to the memory 50.

Furthermore, in the vehicle electronic device 1 according to the first embodiment, the memory 50 is a NAND type non-volatile memory.

In other words, the car electronic device 1 according to the first embodiment can use a NAND type non-volatile memory as the memory 50 for storing the optical axis deviation correction value, which has been difficult to adopt in conventional stereo camera devices because it is cheaper than a NOR type but has fewer limitations on the number of times it can be rewritten. This allows the car electronic device 1 according to the first embodiment to achieve low costs while optimizing the frequency with which the optical axis deviation correction value is rewritten to the memory 50.

Furthermore, in the vehicle electronic device 1 according to the first embodiment, the

cameras

11 and 12 are multiple cameras provided in a stereo camera device.

As a result, the car electronic device 1 according to the first embodiment can back up the latest optical axis shift correction value corresponding to the newest optical axis shift as much as possible in a stereo camera device in which optical axis shift is more likely to directly lead to deterioration in sensing accuracy than in a monocular camera device. Therefore, the car electronic device 1 according to the first embodiment can optimize the frequency of rewriting the optical axis shift correction value to the memory 50 so that the sensing accuracy in the stereo camera device does not deteriorate.

[Example 2]
Fig. 8 is a graph showing the threshold values set in the determination unit 34 according to the embodiment 2. The vertical axis of Fig. 8 indicates the amount of change in the optical axis deviation correction value, and the horizontal axis of Fig. 8 indicates time.

In the determination unit 34 according to the second embodiment, as shown in Fig. 8, not only the thresholds _αth and _-αth but also the thresholds _βth and _-βth are preset. The threshold _βth is set to a value larger than the threshold _αth . The condition regarding the threshold _βth is expressed as in Equation (5).
−β _th <Δx<β _th ... (5)

The determination unit 34 according to the second embodiment determines the rewrite interval tw based on the conditions of the formulas (2) and (5) as follows.
When the condition of the formula (2) is satisfied, the determination unit 34 extends the rewrite interval tw by an extension time n [min], and sets the extended rewrite interval as tw'.
If the condition of the formula (5) is not satisfied, the determination unit 34 shortens the rewrite interval tw by the shortening time m [min], and sets the shortened rewrite interval as tw''.
When the condition of the formula (2) is not satisfied and the condition of the formula (5) is satisfied, the determination unit 34 maintains the current rewriting interval tw.

The car electronic device 1 according to the second embodiment can not only extend or shorten the rewrite interval but also maintain the status quo, so that the rewrite frequency can not only be lowered or increased but also maintained as it is. Therefore, the car electronic device 1 according to the second embodiment can optimize the rewrite frequency of the optical axis deviation correction value in the memory 50 with greater precision than the first embodiment.

[Example 3]
Fig. 9 is a graph showing an extension time function set in the determination unit 34 according to the embodiment 3. The vertical axis of Fig. 9 indicates the amount of change in the optical axis deviation correction value, and the horizontal axis of Fig. 9 indicates the extension time. Fig. 10 is a graph showing a reduction time function set in the determination unit 34 according to the embodiment 3. The vertical axis of Fig. 10 indicates the amount of change in the optical axis deviation correction value, and the horizontal axis of Fig. 10 indicates the reduction time.

In the decision unit 34 according to the first embodiment, the extension time n and shortening time m, which are the amounts of change in the rewrite interval tw, are constant values. In contrast, in the decision unit 34 according to the third embodiment, an extension time function f(Δx) as shown in FIG. 9 is defined for the extension time n, which is the amount of change in the rewrite interval tw. Similarly, in the decision unit 34 according to the third embodiment, shortening time functions f'(Δx) and f''(Δx) as shown in FIG. 10 are defined for the shortening time m, which is the amount of change in the rewrite interval tw. As a result, in the decision unit 34 according to the third embodiment, the extension time n and shortening time m, which are the amounts of change in the rewrite interval tw, can be variable values.

When the condition of formula (2) is satisfied, the determination unit 34 according to the third embodiment calculates the extension time n by substituting the change amount Δx of the optical axis deviation correction value into the extension time function f(Δx) as shown in formula (6). Then, the determination unit 34 according to the third embodiment determines the extended rewriting interval tw′ from formula (3).
n = f(Δx) ... (6)

When the condition of formula (2) is not satisfied, the determination unit 34 according to the third embodiment calculates the shortened time m by substituting the change amount Δx of the optical axis deviation correction value into the shortened time functions f'(Δx) and f''(Δx) as shown in formulas (7) and (8). Then, the determination unit 34 according to the third embodiment determines the shortened rewriting interval tw'' from formula (4).
m = f'(Δx) ... (7)
m = f ″(Δx) ... (8)

In this way, a function indicating the relationship between the amount of change in the optical axis deviation correction value and the amount of change in the rewrite interval is preset in the determination unit 34 according to the third embodiment. The determination unit 34 according to the third embodiment determines the rewrite frequency by substituting the amount of change in the optical axis deviation correction value calculated by the calculation unit 33 into the function to calculate the amount of change in the rewrite interval.

As a result, the car electronic device 1 according to the third embodiment can set the change amount of the rewrite interval to a variable value that varies according to the amount of change in the optical axis shift correction value, and can therefore be optimized more appropriately according to the amount of change in the optical axis shift correction value. Therefore, the car electronic device 1 according to the third embodiment can optimize the frequency of rewriting the optical axis shift correction value to the memory 50 with even greater precision than the first embodiment.

[Example 4]
Fig. 11 is a diagram showing a configuration of the vehicle electronic device 1 according to the fourth embodiment. Fig. 12 is a table for explaining the optimization of the rewrite frequency according to the fourth embodiment.

Due to the physical characteristics of the memory 50, data corruption is more likely to occur when data is rewritten at high temperatures than at room temperature, and data retention reliability is more likely to be impaired. Therefore, the car electronic device 1 of Example 4 determines the rewrite frequency taking into account the temperature of the car electronic device 1.

The car electronic device 1 according to the fourth embodiment further includes a temperature sensor 60 for detecting the temperature of the car electronic device 1, as shown in FIG. 11. The temperature of the car electronic device 1 detected by the temperature sensor 60 may be the temperature of the

cameras

11 and 12, the temperature of the memory 50, or the ambient temperature of these. The temperature sensor 60 is composed of various temperature sensors including a thermistor. The temperature detected by the temperature sensor 60 is stored in the data storage device 40. The decision unit 34 according to the fourth embodiment decides the rewrite frequency based on the amount of change in the optical axis deviation correction value and the temperature of the car electronic device 1. Specifically, the decision unit 34 according to the fourth embodiment makes the rewrite frequency lower when the temperature of the car electronic device 1 is high than when the temperature of the car electronic device 1 is normal temperature.

As a result, the car electronic device 1 of Example 4 can reliably reduce the number of times the memory 50 is rewritten at high temperatures when the data retention reliability of the memory 50 is easily impaired, thereby ensuring data retention reliability. At the same time, the car electronic device 1 of Example 4 can back up the latest optical axis shift correction value to suppress deterioration of sensing accuracy. Therefore, the car electronic device 1 of Example 4 can optimize the frequency of rewriting the optical axis shift correction value to the memory 50 with even greater accuracy than Example 1.

12 shows how the rewrite interval tw is changed for each section of the temperature T of the vehicle electronic device 1 when the magnitude of the change amount Δx of the optical axis shift correction value is small (for example, less than 1.0 pix), large (for example, 1.0 pix or more and 2.0 pix or less), and extremely large (for example, more than 2.0 _pix ). In FIG. 12, the boundary value (for example, 1.0 pix) that distinguishes between the case where the magnitude of the change amount Δx of the optical axis shift correction value is small and the case where the magnitude of the change amount Δx of the optical axis shift correction value is large and the case where the magnitude of the change amount Δx of the optical axis shift correction value is extremely large (for example, 2.0 pix) may be the limit value of the magnitude of the change amount Δx of the optical axis shift correction value corresponding to the limit value of the allowable sensing accuracy.

In FIG. 12, the amount of change in the rewrite interval tw is expressed as either "Medium Extension", "Large Extension", "Extra Large Extension", "Medium Shortening", "Small Shortening", or "Minimal Shortening". For example, "Large Extension" means that the rewrite interval tw is extended, and that the extension time, which is the amount of change in the rewrite interval tw, is large. For example, "Minimal Shortening" means that the rewrite interval tw is shortened, and that the shortening time, which is the amount of change in the rewrite interval tw, is extremely small.

12, when the magnitude of the change amount Δx of the optical axis shift correction value is less than the threshold value (α _th ), the decision unit 34 according to the fourth embodiment extends the rewrite interval tw and makes the extension time, which is the amount of change in the rewrite interval tw when the temperature T of the car electronic device 1 is high, longer than when the temperature T of the car electronic device 1 is at room temperature, thereby reducing the rewrite frequency. On the other hand, when the magnitude of the change amount Δx of the optical axis shift correction value is equal to or greater than the threshold value (α _th ), the decision unit 34 according to the fourth embodiment shortens the rewrite interval tw and makes the shortening time, which is the amount of change in the rewrite interval tw when the temperature T of the car electronic device 1 is high, shorter than when the temperature T of the car electronic device 1 is at room temperature, thereby increasing the rewrite frequency.

As a result, the car electronic device 1 of Example 4 can determine the rewrite interval so as to ensure data retention reliability and suppress deterioration of sensing accuracy, depending on the amount of change in the optical axis shift correction value and the temperature of the car electronic device 1. Therefore, the car electronic device 1 of Example 4 can optimize the rewrite frequency more appropriately than Example 1. Therefore, the car electronic device 1 of Example 4 can optimize the rewrite frequency of the optical axis shift correction value to the memory 50 more accurately than Example 1.

FIG. 13 is a graph showing an extension time function set in the determination unit 34 according to the fourth embodiment. The vertical axis of FIG. 13 indicates the amount of change in the optical axis deviation correction value, and the horizontal axis of FIG. 13 indicates the extension time. FIG. 14 is a graph showing a reduction time function set in the determination unit 34 according to the fourth embodiment. The vertical axis of FIG. 14 indicates the amount of change in the optical axis deviation correction value, and the horizontal axis of FIG. 14 indicates the reduction time.

In FIG. 13, the extension time function f(Δx) is an example of an extension time function used in the case of "Extension (medium)" shown in FIG. 12. The extension time function g(Δx) is an example of an extension time function used in the case of "Extension (large)" shown in FIG. 12. The extension time function h(Δx) is an example of an extension time function used in the case of "Extra Large" shown in FIG. 12. In FIG. 14, the shortening time functions f'(Δx) and f"(Δx) are examples of shortening time functions used in the case of "Shortening (medium)" shown in FIG. 12. The shortening time functions g'(Δx) and g"(Δx) are examples of shortening time functions used in the case of "Shortening (small)" shown in FIG. 12. The shortening time functions h'(Δx) and h"(Δx) are examples of shortening time functions used in the case of "Shortening (minimal)" shown in FIG. 12.

In the determination unit 34 according to the fourth embodiment, as in the third embodiment, an extension time function as shown in FIG. 13 and a shortening time function as shown in FIG. 14 may be defined for the extension time and shortening time, which are the change amounts of the rewrite interval.

As a result, the car electronic device 1 according to the fourth embodiment can set the extension time and shortening time, which are the change amounts of the rewrite interval, to variable values that change according to the change amount of the optical axis shift correction value and the temperature of the car electronic device 1. Therefore, the car electronic device 1 according to the fourth embodiment can further appropriately optimize the change amount of the rewrite interval according to the change amount of the optical axis shift correction value and the temperature of the car electronic device 1. Therefore, the car electronic device 1 according to the fourth embodiment can optimize the frequency of rewriting the optical axis shift correction value to the memory 50 with even greater accuracy than the first and third embodiments.

FIG. 15 is a flowchart showing the rewrite frequency optimization process according to the fourth embodiment.

In step S11, the calculation processing device 30 stores the optical axis deviation correction value x(t _n ) at time t _n in the data storage device 40.

In step S12, the calculation processing device 30 stores the optical axis shift correction value x(t _n+1 ) at time t _n+1 in the data storage device 40.

In step S13, the calculation processing device 30 calculates the amount of change Δx in the stored optical axis deviation correction value.

In step S14, the arithmetic processing unit 30 stores in the data storage unit 40 the temperature T of the vehicle electronic device 1 at the time t _n+1 .

In step S15, the arithmetic processing device 30 judges whether the calculated change amount Δx of the optical axis shift correction value satisfies _-αth < Δx < _αth . If the change amount Δx satisfies _-αth < Δx < _αth , that is, if the magnitude of the change amount Δx is less than the threshold value _αth , the arithmetic processing device 30 proceeds to step S16. If the change amount Δx does not satisfy _-αth < Δx < _αth , that is, if the magnitude of the change amount Δx is equal to or greater than the threshold value _αth , the arithmetic processing device 30 proceeds to step S18.

In step S16, the calculation processing device 30 determines the extension time function to be used from the stored temperature T of the vehicle electronic device 1.

In step S17, the calculation processing device 30 extends the rewrite interval tw according to the determined extension time function.

In step S18, the calculation processing device 30 determines the shortened time function to be used from the stored temperature T of the vehicle electronic device 1.

In step S19, the calculation processing device 30 shortens the rewrite interval tw according to the determined shortened time function.

In step S20, the arithmetic processing device 30 rewrites the memory 50 after the extended or shortened rewrite interval tw' or tw'' has elapsed. In other words, the arithmetic processing device 30 saves the optical axis deviation correction value stored in the data storage device 40 in the memory 50 after the extended or shortened rewrite interval tw' or tw'' has elapsed. Thereafter, the arithmetic processing device 30 ends this process.

[Example 5]
Fig. 16 is a graph showing an extension time function set in the determination unit 34 according to Example 5. The vertical axis of Fig. 16 indicates the amount of change in the optical axis deviation correction value, and the horizontal axis of Fig. 16 indicates the extension time. Fig. 17 is a graph showing a reduction time function set in the determination unit 34 according to Example 5. The vertical axis of Fig. 17 indicates the amount of change in the optical axis deviation correction value, and the horizontal axis of Fig. 17 indicates the reduction time.

In Fig. 16, the extension time function f(Δx) is an example of an extension time function used when the number of times the memory 50 is rewritten is equal to or less than a predetermined value γ _th . The extension time function j(Δx) is an example of an extension time function used when the number of times the memory 50 is rewritten exceeds a predetermined value γ _th . In Fig. 17, the shortening time functions f'(Δx) and f''(Δx) are examples of shortening time functions used when the number of times the memory 50 is rewritten is equal to or less than a predetermined value γ _th . The shortening time functions j'(Δx) and j''(Δx) are examples of shortening time functions used when the number of times the memory 50 is rewritten exceeds a predetermined value γ _th .

When the number of times the memory 50 is rewritten exceeds a predetermined value γ _th , the determination unit 34 according to the fifth embodiment can reduce the number of times the memory 50 is rewritten by the following method.
The optical axis deviation correction value is not rewritten (stored) in the memory 50.
Only the rewrite interval tw is extended, and the rewrite interval tw is not shortened.
The extension time function f(Δx) and the shortening time functions f'(Δx) and f''(Δx) set in the determination unit 34 in Example 3 are changed to the extension time function j(Δx) and the shortening time functions j'(Δx) and j''(Δx) shown in Figures 16 and 17.

As a result, the car electronic device 1 of Example 5 can further reduce the number of times the memory 50 is rewritten compared to Example 3, thereby further ensuring data retention reliability. At the same time, the car electronic device 1 of Example 5 can back up the latest optical axis shift correction value and suppress deterioration of sensing accuracy. Therefore, the car electronic device 1 of Example 5 can optimize the frequency of rewriting the optical axis shift correction value to the memory 50 with even greater accuracy than Example 3.

[Other embodiments]
In the vehicle electronic device 1 according to the first to third embodiments, the rewrite interval is extended and shortened, but the vehicle electronic device 1 may only extend the rewrite interval and not shorten it. Also, the vehicle electronic device 1 may set at least one of a lower limit and an upper limit to the rewrite interval and change the frequency of rewriting the optical axis deviation correction value to the memory 50 within a predetermined range.

The car electronic device 1 may also rewrite the memory 50 (save the optical axis deviation correction value in the memory 50) during at least one of the periods when the speed of the vehicle in which the car electronic device 1 is mounted is zero [km/h] and when the ignition of the vehicle is off. Since the processing load of the arithmetic processing device 30 is large while the vehicle is running, rewriting the memory 50 while the vehicle is running increases the amount of heat generated by the arithmetic processing device 30, which may adversely affect the data retention reliability and sensing accuracy of the memory 50. Therefore, the car electronic device 1 rewrites the memory 50 while the vehicle is stopped and the processing load of the arithmetic processing device 30 is small, thereby suppressing an increase in the amount of heat generated by the arithmetic processing device 30 and suppressing adverse effects on the data retention reliability and sensing accuracy of the memory 50.

Furthermore, when the number of times the memory 50 is rewritten exceeds a predetermined value γ _th , the car electronic device 1 may change the storage area of the optical axis deviation correction value to another storage area within the memory 50 or another storage area outside the memory 50. In this way, the car electronic device 1 may reduce the number of times the memory 50 is rewritten.

The present invention is not limited to the above-described embodiments, and includes various modified examples. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those having all of the configurations described. It is also possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

Furthermore, the above-mentioned configurations, functions, processing units, processing means, etc. may be realized in part or in whole by hardware, for example by designing them as integrated circuits. The above-mentioned configurations, functions, etc. may also be realized by software, in which a processor interprets and executes a program that realizes each function. Information on the programs, tapes, files, etc. that realize each function can be stored in a memory, a recording device such as a hard disk or SSD (solid state drive), or a recording medium such as an IC card, SD card, or DVD.

Furthermore, the control lines and information lines shown are those considered necessary for the explanation, and do not necessarily show all control lines and information lines on the product. In reality, it can be assumed that almost all components are interconnected.

1...Vehicle electronic device, 11, 12...Camera, 20...Image processing device, 31...Image data acquisition unit, 32...Calibration unit, 33...Calculation unit, 34...Decision unit, 35...Control unit, 50...Memory, 60...Temperature sensor

Claims

1. An electronic device for a vehicle, comprising: a correction value for correcting an optical axis shift of a camera in image data captured by the camera; and a rewrite frequency, which is a frequency at which the correction value is stored in a memory, based on an amount of change in the correction value.
The camera;
an image processing device that processes the image data captured by the camera,
The image processing device includes:
The memory;
an image data acquisition unit that acquires the image data from the camera;
a calibration unit that performs calibration including calculation of the correction value;
A calculation unit that calculates the amount of change in the calculated correction value;
a determination unit that determines the rewriting frequency based on the calculated change amount of the correction value;
The electronic device for a vehicle according to claim 1 , further comprising: a control unit configured to store the correction value in the memory in accordance with the determined rewrite frequency.
The determination unit is
When the magnitude of the change amount of the correction value is less than a threshold value, a rewrite interval, which is a time interval for storing the correction value in the memory, is extended to reduce the rewrite frequency;
The electronic device for a vehicle according to claim 2 , wherein, when the magnitude of the amount of change in the correction value is equal to or greater than the threshold value, the rewrite interval is shortened to increase the rewrite frequency.
a function indicating a relationship between an amount of change in a rewrite interval, which is a time interval for storing the correction value in the memory, and an amount of change in the correction value, is preset in the determination unit;
The electronic device for a vehicle according to claim 2 , wherein the determination unit determines the rewrite frequency by substituting the calculated change amount of the correction value into the function to calculate the change amount of the rewrite interval.
A temperature sensor for detecting a temperature of the vehicle electronic device is further provided.
The electronic device for a vehicle according to claim 2 , wherein the determination unit sets the rewriting frequency when the temperature is high to be lower than the rewriting frequency when the temperature is normal.
The determination unit is
when the magnitude of the change amount of the correction value is less than a threshold value, extending a rewrite interval, which is a time interval for storing the correction value in the memory, and reducing the rewrite frequency by making the change amount of the rewrite interval at the high temperature larger than that at the normal temperature;
The electronic device for a vehicle according to claim 5, characterized in that, when the magnitude of the change in the correction value is equal to or greater than the threshold value, the rewrite interval is shortened and the change amount of the rewrite interval at the high temperature is made smaller than that at the normal temperature, thereby increasing the rewrite frequency.
2. The electronic device for a vehicle according to claim 1, wherein the memory is a NAND type non-volatile memory.
The electronic device for a vehicle according to claim 1 , wherein the camera is a plurality of cameras provided in a stereo camera device.