Vehicle-mounted camera control device

Abstract

To suppress the reduction in the recognition performance of a camera due to thermal noise and the increase in power consumption due to an unnecessary operation of cooling control.SOLUTION: An on-vehicle camera control device comprises: a camera 11 which has an image sensor 11a and is configured to acquire image data by imaging the periphery of a vehicle; a temperature sensor 12 which is configured to measure the temperature of the image sensor; an illuminance sensor 13 which is configured to measure the environmental illuminance of an imaging range of the camera; a cooling device 14 which is configured to cool the image sensor; and a control unit 10 which is configured to perform drive support control based on the image data and execute the cooling control of cooling the image sensor by actuating the cooling device when the temperature of the image sensor acquired from the temperature sensor exceeds a prescribed temperature threshold. The control unit changes the temperature threshold based on environmental illuminance related information including the environmental illuminance acquired from the illuminance sensor.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an in-vehicle camera control device capable of executing cooling control for cooling an in-vehicle camera. [Background technology]

[0002] Conventionally, an on-board camera is used to capture images of the surroundings of a vehicle, and various driving assistance controls (including automatic driving controls) are executed based on the image data obtained by capturing the images (hereinafter, the on-board camera may be simply referred to as a "camera"). If the camera becomes too hot, it may not operate normally or its recognition performance may deteriorate, which may reduce the reliability of the driving assistance control. Therefore, various techniques have been developed to prevent the camera (especially the image sensor equipped in the camera) from operating at a high temperature.

[0003] For example, Patent Document 1 describes an in-vehicle camera control device that measures the temperature near an image sensor before starting to energize the image sensor, and starts energizing the image sensor when the measured temperature is equal to or lower than a preset first threshold. Patent Document 1 describes that by determining whether to start energizing the image sensor based on the measured temperature near the image sensor not only during image capture but also before starting to energize, it becomes less likely that a situation will occur in which "electricity is energized to the image sensor even though the temperature around the image sensor is abnormally high when the power is turned on," and that this reduces the possibility of the image sensor being damaged or thermal noise being generated. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-226974 A Summary of the Invention

[0005] In addition to the above-mentioned power supply suppression, cooling control that cools the camera based on the temperature of the camera (typically the temperature near the image sensor) is known as a technology for suppressing the operation of the camera in a high temperature state. When the camera becomes hot, thermal noise due to dark current occurs randomly on the image sensor, degrading the recognition performance of the camera. For this reason, a conventional vehicle-mounted camera control device (hereinafter also referred to as a "conventional device") capable of executing cooling control is configured to set a temperature threshold in advance, and start cooling control when the temperature of the camera exceeds this temperature threshold, thereby suppressing the generation of thermal noise.

[0006] Incidentally, the allowable amount of thermal noise (i.e., the maximum amount of thermal noise that does not directly affect the recognition performance of the camera) varies depending on the illuminance around the camera, specifically, the higher the illuminance around it is, the larger the allowable amount becomes (hereinafter, the illuminance around it is also referred to as "ambient illuminance"). For this reason, conventional devices usually set a temperature threshold value that is "a temperature at which the amount of thermal noise generated is suppressed to below the minimum allowable amount of thermal noise," thereby suppressing the deterioration of recognition performance caused by thermal noise.

[0007] However, in the method of setting the temperature threshold value by the conventional device, the cooling control is executed even when the camera does not need to be cooled. That is, as described above, when the ambient illuminance is high, the allowable amount of thermal noise increases, so even if the temperature of the camera is higher than the temperature threshold, if the amount of thermal noise generated is equal to or less than the allowable amount, the camera does not need to be cooled. If the cooling control is executed even in such a case, the power consumption increases unnecessarily, which is problematic. In addition, if the cooling control is performed mechanically, for example, using a fan, the sound generated during cooling may be annoying to the vehicle occupants.

[0008] The present invention has been made to address the above-mentioned problems. That is, one of the objects of the present invention is to provide an in-vehicle camera control device that can simultaneously suppress the deterioration of the recognition performance of the camera caused by thermal noise and suppress the increase in power consumption caused by unnecessary operation of the cooling control.

[0009] The vehicle-mounted camera control device according to the present invention (hereinafter referred to as the "device of the present invention") comprises: Mounted on the vehicle, a camera (11) including an image sensor (11a) and configured to capture an image of the surroundings of the vehicle and acquire image data; a temperature sensor (12) configured to measure a temperature (T) of the image sensor; An illuminance sensor (13) configured to measure an environmental illuminance (L) in an imaging range of the camera; a cooling device (14) configured to cool the image sensor; Carry out driving assistance control based on the image data; when the temperature of the image sensor acquired from the temperature sensor exceeds a predetermined temperature threshold (Tth), executing cooling control to operate the cooling device to cool the image sensor; A control unit (10) configured as described above; Equipped with. The control unit When the environmental illuminance (L) acquired from the illuminance sensor (13) is equal to or lower than a predetermined illuminance threshold (Lth), the temperature threshold (Tth) is set to a first temperature (T1); When the environmental illuminance acquired from the illuminance sensor exceeds the illuminance threshold, the temperature threshold is set to a second temperature (T2) higher than the first temperature.

[0010] heat The allowable noise level (noise that occurs on the image sensor when the camera is at high temperature) is 、 Ambient illuminance in the camera's imaging range The higher the ambient illuminance, the greater the loss in recognition performance of the camera. In other words, the higher the ambient illuminance, the less likely it is that degradation of the recognition performance of the camera due to thermal noise will occur, even if the temperature of the image sensor becomes relatively high (even if the amount of thermal noise generated increases). The device of the present invention is configured to change the temperature threshold (the temperature used to determine whether or not cooling control of the image sensor is required) to two different values ​​based on the magnitude relationship between the ambient illuminance and the illuminance threshold. The temperature threshold can be set to "a temperature at which the amount of thermal noise generated is equal to or less than the allowable amount of thermal noise according to the acquired environmental illuminance." With this configuration, the cooling control is executed, so that the temperature of the image sensor is less likely to exceed "the temperature threshold set based on the allowable amount of thermal noise according to the environmental illuminance," and therefore it is possible to suppress a deterioration in the recognition performance of the camera due to thermal noise. In addition, the temperature threshold is not a unique value, but is set based on the allowable amount of thermal noise according to the environmental illuminance. 2 ways Since the value of the cooling frequency can be changed to 0, the frequency of unnecessary operation of the cooling control can be reduced, and an increase in power consumption due to the unnecessary operation can be suppressed. In addition, when the cooling control is performed mechanically using a fan or the like, the frequency of unnecessary operation can be reduced, and thus the frequency of annoying noise generated during cooling to the vehicle occupants can be reduced. It should be noted that the "temperature of the image sensor" may also include the "temperature in the vicinity of the image sensor."

[0013] In the above description, in order to facilitate understanding of the invention, the symbols used in the embodiments are added in parentheses to the constituent elements of the invention corresponding to the embodiments, but each constituent element of the invention is not limited to the embodiment defined by the said symbols. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic configuration diagram of an in-vehicle camera control device (embodiment device) according to an embodiment of the present invention. [Diagram 2] 13 is a diagram comparing the temperature transition of the image sensor in the present embodiment device and the first comparison device. FIG. [Diagram 3] 13 is a diagram comparing the temperature transition of the image sensor in the embodiment and the second comparison device. FIG. [Figure 4] 6 is a flowchart showing a routine (temperature threshold setting process) executed by a CPU of a camera control ECU of the embodiment of the present invention. [Diagram 5] 4 is a flowchart showing a routine (cooling control process) executed by a CPU. [Figure 6] 13 is a diagram comparing the temperature transition of the image sensor between the embodiment and the third comparison device. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] (composition) An in-vehicle camera control device (hereinafter also referred to as "the embodiment device") according to an embodiment of the present invention will be described below with reference to the drawings. The embodiment device is mounted on a vehicle. As shown in FIG. 1, the embodiment device includes a camera control ECU 10. The camera control ECU 10 includes a microcomputer as a main part. ECU is an abbreviation for Electronic Control Unit. The microcomputer includes a CPU, ROM, RAM, an interface (I / F), etc., and the CPU realizes various functions by executing instructions (programs, routines) stored in the ROM. Hereinafter, the vehicle on which the embodiment device is mounted will be referred to as the "own vehicle."

[0016] The camera control ECU 10 is connected to a camera 11, a temperature sensor 12, an illuminance sensor 13, and a cooling device 14. The camera control ECU 10 acquires signals generated / output by these sensors 11 to 13 at predetermined calculation intervals, and controls the operation of the cooling device 14 based on the acquired signals. Hereinafter, the camera control ECU 10 is also simply referred to as "ECU 10."

[0017] The camera 11 is installed on the rear surface of the room mirror (inner mirror / rear-view mirror) of the vehicle, and is configured to capture an image of the area ahead of the vehicle to obtain image data. Specifically, the camera 11 includes an optical system (not shown), an image sensor 11a, and a signal processing circuit (not shown). The optical system forms an image of light from an object present in front of the vehicle on an imaging surface (described later). The image sensor 11a includes an imaging surface (not shown) on which a plurality of pixels are arranged at equal intervals in the horizontal and vertical directions (i.e., two-dimensionally). Each pixel of the image sensor 11a is configured to convert light received via the optical system into an electrical signal and output the signal. The signal processing circuit performs processes such as gamma correction and distortion correction on the electrical signal output from the image sensor 11a to generate image data of the object.

[0018] The camera 11 recognizes (detects) a three-dimensional object existing in front of the vehicle based on image data, and calculates the relative relationship between the vehicle and the three-dimensional object. Here, the "relative relationship between the vehicle and the three-dimensional object" includes the distance from the vehicle to the three-dimensional object, the orientation and relative speed of the three-dimensional object with respect to the vehicle, etc. The three-dimensional object includes stationary objects (e.g., tunnels, elevated roads, and roadside trees) and moving objects (e.g., other vehicles and pedestrians). Note that a moving object means a movable three-dimensional object, and does not mean only a moving three-dimensional object. In addition, the camera 11 recognizes (detects) markings extending ahead of the vehicle based on the image data, and calculates the shape of the lane (the area between two adjacent markings) based on the recognized markings. Hereinafter, these calculation results are referred to as "target information". The camera 11 outputs the target information to the ECU 10. The camera 11 may be configured to output image data to the ECU 10. In this case, the ECU 10 may be configured to acquire the target information based on the image data.

[0019] The temperature sensor 12 is installed in the vicinity of the image sensor 11a and is configured to measure the temperature T in the vicinity of the image sensor 11a (hereinafter simply referred to as "the temperature T of the image sensor 11a"). Specifically, the temperature sensor 12 generates a signal corresponding to the temperature T of the image sensor 11a. The ECU 10 acquires the signal generated by the temperature sensor 12 and calculates the temperature T of the image sensor 11a based on the signal.

[0020] The illuminance sensor 13 is installed near the camera 11 and configured to measure the environmental illuminance L in front of the vehicle (i.e., the imaging range of the camera 11). Specifically, the illuminance sensor 13 generates a signal corresponding to the environmental illuminance L in front of the vehicle. The ECU 10 acquires the signal generated by the illuminance sensor 13 and calculates the environmental illuminance L of the illuminance sensor 13 based on the signal.

[0021] The cooling device 14 is installed near the camera 11 and configured to cool the camera 11 (more specifically, the image sensor 11a). Specifically, the cooling device 14 includes a fan, and upon receiving a drive command from the ECU 10, drives the fan to cool the camera 11.

[0022] (Details of operation) Next, the operation of the ECU 10 will be described in detail. The ECU 10 is configured to execute various driving assistance controls (including automatic driving control) based on the target information (however, other ECUs not shown may be configured to execute these controls based on the target information). When the camera 11 becomes hot, thermal noise due to dark current is randomly generated on the image sensor 11a, which may reduce the recognition performance of the camera 11, thereby reducing the reliability of the driving assistance control. For this reason, a temperature threshold has been previously set in the camera (strictly speaking, the image sensor), and when the temperature of the camera exceeds this temperature threshold, cooling control is started to suppress the generation of thermal noise. Here, the allowable amount of thermal noise (i.e., the maximum amount of thermal noise that does not directly affect the recognition performance of the camera) changes depending on the environmental illuminance (specifically, the higher the environmental illuminance, the larger it becomes). However, in conventional devices, the ambient illuminance was not taken into consideration when setting the temperature threshold, so the temperature threshold was set to "a temperature at which the amount of thermal noise generated is kept below the minimum allowable amount of thermal noise." As a result, cooling control was performed even when there was no need to cool the camera, which could result in an unnecessary increase in power consumption or a nuisance to vehicle occupants due to the sound generated during cooling.

[0023] Therefore, the ECU 10 is configured to set the temperature threshold to two values ​​based on the environmental illuminance. Specifically, when the environmental illuminance L acquired from the illuminance sensor 13 is equal to or less than a predetermined illuminance threshold Lth, the ECU 10 sets the temperature threshold Tth of the image sensor 11a to a first temperature T1, and when the environmental illuminance L exceeds the illuminance threshold Lth, the ECU 10 sets the temperature threshold Tth to a second temperature T2 higher than the first temperature T1. Here, the illuminance threshold Lth is a threshold for distinguishing the brightness ahead of the vehicle into a "relatively bright case" and a "relatively dark case", and can be determined in advance by experiment or simulation. The first temperature T1 is "any temperature at which the amount of thermal noise generated is less than the allowable amount of thermal noise according to the illuminance threshold Lth", and the second temperature T2 is "any temperature at which the amount of thermal noise generated is more than the allowable amount of thermal noise according to the illuminance threshold Lth". Both the first temperature T1 and the second temperature T2 can be determined in advance by experiment or simulation. As is clear from the above description, the first temperature T1 may be set to "a temperature at which the amount of generated thermal noise is suppressed to or below the minimum allowable amount of thermal noise."

[0024] When the temperature T of the image sensor 11a is higher than the temperature threshold Tth, the ECU 10 drives the fan of the cooling device 14 to execute cooling control, and ends the cooling control when the temperature T becomes equal to or lower than the target temperature Ttgt through the cooling control. Here, the target temperature Ttgt can be set to a value obtained by subtracting a predetermined difference ΔT from the temperature threshold Tth. That is, when L≦Lth is satisfied, the ECU 10 executes cooling control when the temperature T of the image sensor 11a is higher than the first temperature T1, and ends the cooling control when the temperature T reaches the target temperature Ttgt (=T1-ΔT) through the cooling control. On the other hand, when L>Lth is satisfied, the ECU 10 executes cooling control when the temperature T of the image sensor 11a is higher than the second temperature T2 (>T1), and ends the cooling control when the temperature T reaches the target temperature Ttgt (=T2-ΔT) through the cooling control. In reality, in order to suppress hunting, cooling control is executed when the temperature T exceeds the temperature threshold value Tth for a predetermined duration. However, in this embodiment, for the sake of convenience, the duration is omitted.

[0025] According to this configuration, when L≦Lth holds (i.e., when the tolerance of thermal noise is relatively small), the temperature threshold Tth (=T1) is set relatively low, so that the temperature T of the image sensor 11a exceeds the temperature threshold Tth more frequently, and cooling control is frequently performed. Therefore, even when the tolerance of thermal noise is relatively small, it is difficult for the amount of thermal noise to exceed the tolerance, and as a result, it is possible to suppress the deterioration of the recognition performance of the camera 11 caused by thermal noise. On the other hand, when L>Lth holds (i.e., when the tolerance of thermal noise is relatively large), the temperature threshold Tth (=T2) is set relatively high, but since the tolerance of thermal noise is relatively large, it is difficult for the amount of thermal noise generated to exceed the tolerance. Also, by setting the temperature threshold Tth relatively high, it is difficult for the temperature T of the image sensor 11a to exceed the temperature threshold Tth, and unnecessary operation of cooling control can be suppressed. In other words, it is possible to reduce the frequency of unnecessary operation of cooling control while suppressing deterioration of the recognition performance of the camera 11 caused by thermal noise.

[0026] A specific description will be given with reference to FIG. 2. FIG. 2 shows a comparison of the transition of the temperature T of the image sensor 11a in the case where L>Lth is satisfied (i.e., when the area in front of the vehicle is relatively bright) between the present embodiment and an in-vehicle camera control device according to Comparative Example 1 (hereinafter referred to as the "first comparison device"). In FIG. 2, the transition of the temperature T of the image sensor 11a in the present embodiment is shown by a solid line, and the transition of the temperature Tc1 of the image sensor 11a in the first comparison device is shown by a dashed line. In the example of FIG. 2, since L>Lth is satisfied, the present embodiment sets the temperature threshold Tth to the second temperature T2. In contrast, the first comparison device sets the temperature threshold Tth without considering the environmental illuminance L as in the past, and in this example, the temperature threshold Tth is set to the first temperature T1. Note that the present embodiment and the first comparison device have the same configuration except for the difference in the setting of the temperature threshold Tth (this also applies to the second comparison device and the third comparison device described later). Moreover, the temperature Tm is the maximum temperature that can guarantee normal operation of the camera 11. In this example, the temperature Tm is higher than the second temperature T2.

[0027] As shown in FIG. 2, the temperature T of the image sensor 11a of the present embodiment slowly rises from time t0 due to, for example, solar radiation or self-heating of the camera 11, and reaches the first temperature T1 at time t1. Since the present embodiment sets the temperature threshold Tth to the second temperature T2, the temperature T continues to rise after time t1, and after time t3, the temperature Tc1 of the image sensor 11a of the first comparison device similarly rises slowly from time t0. Since the first comparison device sets the temperature threshold Tth to the first temperature T1, when the temperature Tc1 reaches the first temperature T1 at time t1, the cooling control is started at that time. When the temperature Tc1 falls due to the cooling control and reaches the target temperature Ttgt at time t2, the cooling control is ended at that time. After time t2, the temperature Tc1 is similarly maintained in equilibrium at the target temperature Ttgt by entering the shade or being cooled by air conditioning.

[0028] In this way, the first comparison device sets the temperature threshold Tth as a unique value regardless of the environmental illuminance L, so that the temperature threshold Tth must be set low to suppress the deterioration of recognition performance caused by thermal noise, and therefore, as in the example of Fig. 2, cooling control is executed even in a situation where cooling control is not actually required. In contrast, the present embodiment device reduces the frequency of unnecessary cooling control operation while suppressing the deterioration of recognition performance caused by thermal noise by raising the temperature threshold Tth from the first temperature T1 to the second temperature T2 when the environmental illuminance L is higher than the illuminance threshold Lth. The environmental illuminance L corresponds to an example of "environmental illuminance related information".

[0029] In addition, when L>Lth is established, the ECU 10 judges whether or not there is a "factor that causes the environmental illuminance L to fall below the illuminance threshold Lth (i.e., a factor that causes L≦Lth to be established)" within the distance D in the traveling direction (i.e., forward) from the current position of the vehicle based on the target information. When the factor does not exist, the ECU 10 sets the temperature threshold Tth to the second temperature T2. On the other hand, when the factor exists, the ECU 10 sets the temperature threshold Tth to the first temperature T1. Here, the "factor that causes the environmental illuminance L to fall below the illuminance threshold Lth" is a tunnel, an overpass, a forest, etc. That is, when the vehicle enters a tunnel, an overpass, a forest, etc., the area ahead of the vehicle becomes suddenly dark, and the environmental illuminance L falls suddenly to the illuminance threshold Lth or below. The distance D is set to a value obtained by multiplying the "time required to reduce the temperature T of the image sensor 11a by the temperature range T2-T1 when cooling control is performed with maximum cooling capacity" by the "average vehicle speed (e.g., 50 km / h)".

[0030] According to this configuration, when the factor for which L≤Lth holds is detected D distance ahead, even though the ambient illuminance L at the current time exceeds the illuminance threshold value Lth, the temperature threshold value Tth is lowered from the second temperature T2 to the first temperature T1. For this reason, when the temperature T of the image sensor 11a at the current time satisfies T1<T<T2, cooling control is started at that time. As described above, since the distance D is set to "the distance traveled when traveling for the time required to lower the temperature T by the temperature range of T2 - T1 at an average vehicle speed", when the host vehicle has traveled the distance D, the image sensor 11a is cooled and its temperature T will surely fall below the first temperature T1. For this reason, even if L≤Lth actually holds after traveling the distance D and as a result the allowable amount of thermal noise rapidly decreases, since the image sensor 11a has been pre-cooled and its temperature T satisfies T≤T1, it becomes difficult for a situation to occur in which the amount of thermal noise generated at the temperature T exceeds the allowable amount of thermal noise, and it becomes possible to reduce the frequency of execution of the stop control or shorten the period of execution. Here, the stop control is control for temporarily stopping the operation of the camera 11 in order to ensure recognition performance, and is executed during the period in which the temperature T exceeds the temperature threshold value Tth (in other words, in the present embodiment, it ends when the temperature T has dropped to the temperature threshold value Tth by the cooling control).

[0031] A specific description will be given with reference to FIG. 3. FIG. 3 shows a comparison between the present embodiment and an on-board camera control device according to Comparative Example 2 (hereinafter referred to as "second comparison device") in terms of the transition of the temperature T of the image sensor 11a in a situation where the vehicle enters a tunnel at time t5 from a state where L>Lth is established (i.e., the vehicle is relatively bright ahead), and travels through the tunnel from time t5 onwards. In FIG. 3, the transition of the temperature T of the image sensor 11a of the present embodiment is shown by a solid line, and the transition of the temperature Tc2 of the image sensor 11a of the second comparison device is shown by a dashed line. Unlike the first comparison device, the second comparison device is capable of changing the temperature threshold Tth to the first temperature T1 or the second temperature T2 based on the magnitude relationship between the environmental illuminance L and the illuminance threshold Lth. That is, the present embodiment differs from the second comparison device in that the temperature threshold Tth is set to the first temperature T1 when "a factor that establishes L≦Lth" exists within the distance D from the current position of the vehicle when L>Lth is established.

[0032] As shown in FIG. 3, the temperature Tc2 of the image sensor 11a of the second comparison device is in an equilibrium state after time t0 and satisfies T1 < Tc2 < T2. At this time, since the temperature threshold Tth is set to the second temperature T2 (because L > Lth holds), cooling control is not performed. Then, when entering the tunnel at time t5, since L ≤ Lth holds, the temperature threshold Tth is lowered from the second temperature T2 to the first temperature T1 at time t5. Then, since the temperature Tc2 exceeds the temperature threshold Tth (= T1), cooling control is started and stop control is executed at time t5. The stop control continues until the temperature Tc2 reaches the temperature threshold Tth (i.e., until time t7). As a result, the operation of the camera 11 is temporarily stopped during the period from time t5 to time t7. Note that the cooling control ends when the temperature Tc2 reaches the target temperature Ttgt (time t8). On the other hand, the temperature T of the image sensor 11a of the present apparatus is also in an equilibrium state after time t0 and satisfies T1 < T < T2, so cooling control is not executed. Then, when recognizing a tunnel ahead by a distance D at time t4, even though L > Lth at the current time, the temperature threshold Tth is lowered from the second temperature T2 to the first temperature T1. Then, since the temperature T exceeds the temperature threshold Tth (= T1), cooling control is started at time t4. As a result, at the time of entering the tunnel at time t5, the temperature T is surely below the temperature threshold Tth (= T1), so stop control is not performed. Note that the cooling control continues until the target temperature Ttgt is reached at time t6.

[0033] In this way, the second comparison device can set the temperature threshold Tth to two values ​​according to the environmental illuminance L, and therefore has the advantage of being able to suppress unnecessary operation of the cooling control while suppressing deterioration of the recognition performance of the camera 11. However, in a situation where the environmental illuminance L drops suddenly, such as in a tunnel, the temperature threshold Tth is suddenly changed, and even if cooling control is performed, a period occurs in which the temperature Tc2 exceeds the temperature threshold Tth, so that in order to ensure the recognition performance, a stop control must be performed, which is inconvenient. In contrast, the present embodiment device is configured to be able to execute the cooling control in advance by lowering the temperature threshold Tth when a factor that causes the environmental illuminance L to drop suddenly (i.e., to become equal to or lower than the illuminance threshold Lth), such as a tunnel, exists ahead, even if L>Lth is established. With this configuration, even if the environmental illuminance L drops suddenly at the time of entering a tunnel, etc., and the allowable amount of thermal noise drops suddenly, the amount of thermal noise generated at the temperature T at the time of entry is unlikely to exceed the allowable amount of thermal noise, so that the recognition performance can be guaranteed without executing the stop control. Information regarding "whether there is a factor that will cause the environmental illuminance L to drop below the illuminance threshold value Lth within a distance D in the traveling direction (i.e., forward) from the current position of the vehicle" corresponds to an example of "environmental illuminance related information."

[0034] In this embodiment, the determination of "whether or not there is a factor that makes L≦Lth true within the distance D" is based on the target object information acquired by the camera 11, but the present invention is not limited to this configuration, and the above determination may be performed using, for example, a navigation system (not shown). That is, the present embodiment may include a memory in which map information is stored, and the current position of the vehicle may be identified from a GPS signal acquired by a GPS receiver, and the current position may be mapped onto the map information to perform the above determination.

[0035] (Specific operation) Next, a detailed description will be given of the operation of the ECU 10. The CPU of the ECU 10 is configured to repeatedly execute, in parallel, the routines (temperature threshold Tth setting process and cooling control process) shown in the flowcharts of Figures 4 and 5 every time a predetermined time elapses while the ignition switch is in the ON position.

[0036] At a predetermined timing, the CPU starts the process from step 400 in FIG. 4 and proceeds to step 410 to acquire the environmental illuminance L from the illuminance sensor 13. Next, the CPU proceeds to step 420 to determine whether the environmental illuminance L exceeds the illuminance threshold Lth. If L≦Lth, the CPU determines "No" in step 420 and proceeds to step 430 to set the temperature threshold Tth to the first temperature T1. Thereafter, the CPU proceeds to step 495 to temporarily end this routine. On the other hand, if L>Lth, the CPU determines "Yes" in step 420 and proceeds to step 440.

[0037] In step 440, the CPU judges whether or not a factor that L≦Lth is satisfied exists within the distance D from the current position of the vehicle based on the target information. If the factor does not exist, the CPU judges "No" in step 440, proceeds to step 450, and sets the temperature threshold Tth to the second temperature T2 (>T1). After that, the CPU proceeds to step 495, and ends this routine. On the other hand, if the factor exists, the CPU judges "Yes" in step 440, proceeds to step 430, and sets the temperature threshold Tth to the first temperature T1 (even though L>Lth is satisfied at the present time). After that, the CPU proceeds to step 495, and ends this routine. This concludes the explanation of the temperature threshold Tth setting process.

[0038] 5 and proceeds to step 510 to determine whether cooling is in progress (i.e., whether cooling control is being executed). If cooling control is not being executed, the CPU determines "No" in step 510 and proceeds to step 520.

[0039] In step 520, the CPU acquires the temperature threshold value Tth that was set by the temperature threshold value Tth setting process (see FIG. 4), and proceeds to step 530. In step 530 , the CPU obtains the temperature T of the image sensor 11 a from the temperature sensor 12 , and proceeds to step 540 .

[0040] In step 540, the CPU determines whether or not the temperature T exceeds the temperature threshold value Tth. If T≦Tth, the CPU determines "No" in step 540 and proceeds to step 595 to temporarily end this routine. That is, cooling control is not executed. On the other hand, if T>Tth, the CPU determines "Yes" in step 540 and proceeds to step 550 to start cooling (that is, start cooling control).

[0041] Next, the CPU proceeds to step 560 and determines whether the temperature T has reached the target temperature Ttgt (=Tth-ΔT). If T>Ttgt, the CPU determines "No" at step 560, proceeds to step 595, and ends this routine for the time being. In this case, the CPU passes through step 595, determines "Yes" at step 510 of the next period, and performs the determination at step 560. If the temperature T has reached the target temperature Ttgt while repeating this process, the CPU determines "Yes" at step 560, proceeds to step 570, and stops cooling (i.e., ends the cooling control). Thereafter, the CPU proceeds to step 595 and ends this routine for the time being. This concludes the explanation of the cooling control process.

[0042] (Modification) Next, an in-vehicle camera control device (hereinafter, also referred to as a "modification device") according to a modification of the present invention will be described with reference to FIG. 6. When the temperature T of the image sensor 11a exceeds the stop temperature threshold Tsth, the modification device executes stop control until the temperature T falls below the stop temperature threshold Tsth. In this modification, cooling control is not executed. The modification device can set the stop temperature threshold Tsth to two values ​​based on the environmental illuminance L. Specifically, when L≦Lth is satisfied, the modification device sets the stop temperature threshold Tsth to a third temperature T3, and when L>Lth is satisfied, the modification device sets the stop temperature threshold Tsth to a fourth temperature T4 higher than the third temperature T3.

[0043] FIG. 6 shows a diagram comparing the transition of the temperature T of the image sensor 11a when L > Lth holds, with the modified device and an in-vehicle camera control device according to Comparative Example 3 (hereinafter referred to as the "third comparison device"). In FIG. 6, the transition of the temperature T of the image sensor 11a of the modified device is shown by a solid line, and the transition of the temperature Tc3 of the image sensor 11a of the third comparison device is shown by a broken line. In the example of FIG. 6, since L > Lth holds, the modified device sets the stop temperature threshold Tsth to the fourth temperature T4. On the other hand, the third comparison device sets the stop temperature threshold Tsth without considering the ambient illuminance L as before, and in this example, it is set to the third temperature T3.

[0044] As shown in FIG. 6, from time t0 to time t9, the ignition switch is off (i.e., the camera 11 is not operating). During this period, the temperature T3c of the image sensor 11a of the third comparison device has become relatively high due to solar radiation or the like, and T3 < T3c < T4 holds. When the ignition switch is turned on at time 9 in this state and the camera 11 tries to start operating, since the temperature T3c exceeds the stop temperature threshold Tsth (= T3), stop control is executed and the camera 11 stops operating. When the temperature T3c decreases and reaches the third temperature T3 at time 10, for example, by cooling the camera 11 by air conditioning or the host vehicle entering the shade, the stop control ends and the camera 11 starts operating. In this example, the temperature T3c is in an equilibrium state at time 11. On the other hand, even when the temperature T of the image sensor 11a of the modified device is relatively high (T3 < T < T4) when the ignition switch is turned on at time t9, since the stop temperature threshold Tsth is set to the fourth temperature T4 (because L > Lth), stop control is not executed.

[0045] According to this configuration, it is possible to suppress unnecessary operations of the stop control while ensuring the recognition performance of the camera 11.

[0046] The above describes the vehicle-mounted camera control device according to the present embodiment and its modified examples. However, the present invention is not limited to the above embodiment and modified examples, and various modifications are possible without departing from the purpose of the present invention.

[0047] For example, the temperature threshold Tth may be a function of the environmental illuminance L. That is, the temperature threshold Tth is not limited to a configuration limited to two values ​​(the first temperature T1 and the second temperature T2). The same applies to the stop temperature threshold Tsth. [Explanation of symbols]

[0048] 10: camera control ECU, 11: camera, 11a: image sensor, 12: temperature sensor, 13: illuminance sensor, 14: cooling device

Claims

[Claim 1] Mounted on the vehicle, a camera having an image sensor and configured to capture an image of the surroundings of the vehicle and acquire image data; a temperature sensor configured to measure a temperature of the image sensor; an illuminance sensor configured to measure an ambient illuminance in an imaging range of the camera; a cooling device configured to cool the image sensor; Carry out driving assistance control based on the image data; when the temperature of the image sensor acquired from the temperature sensor exceeds a predetermined temperature threshold, a cooling control is executed to operate the cooling device to cool the image sensor. A control unit configured as described above. Equipped with The control unit When the environmental illuminance acquired from the illuminance sensor is equal to or lower than a predetermined illuminance threshold, the temperature threshold is set to a first temperature; When the environmental illuminance acquired from the illuminance sensor exceeds the illuminance threshold, the temperature threshold is set to a second temperature higher than the first temperature. It was configured as follows: In-vehicle camera control device.

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