Light distribution control device, vehicle lamp system, and computer program

Abstract

This light distribution control device uses an image based on an imaging device for imaging an area in front of a vehicle to control the formation of a light distribution pattern by a light distribution variable lamp. When illuminance is to be changed in a first illuminance region (IR1) that is less than or equal to a prescribed first illuminance threshold value (Th1), the light distribution control device changes the illuminance by a first change amount (C1) that is smaller than a change amount by which the illuminance is to be changed in an illuminance region that is greater than the first illuminance threshold value (Th1).

Description

Light distribution control device, vehicle lighting system, and computer program

[0001] The present invention relates to a light distribution control device, a vehicle lighting system, and a computer program.

[0002] In recent years, adaptive driving beam (ADB) control has been proposed, which dynamically and adaptively controls a light distribution pattern based on the conditions around the vehicle (see, for example, Patent Document 1). ADB control uses a camera to detect the presence or absence of a light-blocking target located in front of the vehicle that should be avoided from being illuminated with high-intensity light, and blocks the area corresponding to the light-blocking target. Examples of light-blocking targets include vehicles ahead, such as a preceding vehicle or an oncoming vehicle. A vehicle ahead can be detected by the appearance of a light spot corresponding to a lamp in an image. By blocking the area corresponding to the vehicle ahead, the glare experienced by the driver of the vehicle ahead can be reduced.

[0003] JP 2016-088224 A

[0004] In addition to vehicles ahead, other targets that should be avoided include road signs, delineators, billboards, and other light-reflecting objects. In recent years, vehicle lighting fixtures have become increasingly bright, and the intensity of light reflected by light-reflecting objects has tended to increase. As a result, there is an increasing risk that high-intensity light will be reflected from light-reflecting objects and that the driver of the vehicle will be subjected to glare.

[0005] A light-reflecting object does not emit light itself. Therefore, when a light-blocking portion is formed on a light-reflecting object, the light spot corresponding to the light-reflecting object disappears from the image. Then, when the next light distribution pattern is formed, light is irradiated onto the light-reflecting object. As a result, the light spot originating from the light-reflecting object reappears in the image. This repeated disappearance and reappearance of the light spot can be visually perceived by the driver of the vehicle as flickering.

[0006] One way to reduce flickering is to gradually change the amount of light when switching between shading and illumination, thereby extending the cycle of the disappearance and reappearance of the light spot. However, this method delays the formation of the shading area for traffic participants, such as a vehicle or pedestrian ahead, if the light spot originates from such a traffic participant. In other words, reducing flickering to improve the driver's visibility increases the likelihood of causing glare to traffic participants.

[0007] The present invention has been made in consideration of these circumstances, and one of its purposes is to provide a technology that makes it easier to achieve both improved visibility for the driver of the vehicle and reduced glare for traffic participants.

[0008] In order to solve the above problems, one aspect of the present invention is a light distribution control device that controls the formation of a light distribution pattern by a variable light distribution lamp using an image captured by an imaging device that captures an image of the area ahead of a vehicle. When changing the illuminance in a first illuminance region that is equal to or less than a predetermined first illuminance threshold, the light distribution control device changes the illuminance by a first change amount that is smaller than the change amount when changing the illuminance in an illuminance region that exceeds the first illuminance threshold.

[0009] Another aspect of the present invention is a vehicle lighting system that includes an imaging device that images an area ahead of the vehicle, a variable light distribution lamp that can irradiate an area ahead of the vehicle with a visible light beam that has a variable intensity distribution, and the light distribution control device of the above aspect.

[0010] Another aspect of the present invention is a computer program executed by a light distribution control device that controls the formation of a light distribution pattern by a variable light distribution lamp using an image captured by an imaging device that captures an image of the area ahead of a vehicle. The computer program causes the light distribution control device to perform a function of changing the illuminance in a first illuminance region that is equal to or less than a predetermined first illuminance threshold by a first change amount that is smaller than when changing the illuminance in an illuminance region that exceeds the first illuminance threshold.

[0011] Any combination of the above components and conversion of the present invention into a method, device, system, etc. are also valid aspects of the present invention.

[0012] According to the present invention, it is possible to easily achieve both improved visibility for the driver of the vehicle and reduced glare for traffic participants.

[0013] Fig. 2 is a block diagram of a vehicle lighting system according to an embodiment. Fig. 2(A) is a diagram showing an image obtained under the formation of a reference light distribution pattern. Fig. 2(B) is a diagram showing the analysis results of a luminance analysis unit. Fig. 2 is a diagram showing the transition of illuminance of target light regarding a high-luminance light spot originating from a light-reflecting object. Fig. 2 is a diagram showing the transition of illuminance of target light regarding a high-luminance light spot originating from a self-luminous body. Fig. 3 is a flowchart showing an example of light distribution control.

[0014] The present invention will be described below with reference to the drawings based on preferred embodiments. The embodiments are illustrative and do not limit the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention. The same or equivalent components, parts, and processes shown in the drawings are designated by the same reference numerals, and redundant descriptions are omitted where appropriate. The scale and shape of each part shown in the drawings are set for convenience to facilitate explanation and should not be interpreted as limiting unless otherwise specified. Furthermore, when terms such as "first" and "second" are used in this specification or claims, unless otherwise specified, these terms do not indicate any order or importance, but are used to distinguish one configuration from another. Furthermore, some components that are not important for explaining the embodiments are omitted in the drawings.

[0015] Fig. 1 is a block diagram of a vehicle lighting system 1 according to an embodiment. In Fig. 1, some of the components of the vehicle lighting system 1 are depicted as functional blocks. These functional blocks are realized as a hardware configuration by elements and circuits such as a computer CPU and memory, and as a software configuration by a computer program or the like. Those skilled in the art will understand that these functional blocks can be realized in various ways by combining hardware and software.

[0016] The vehicle lighting system 1 includes an adjustable light distribution lamp 2, an imaging device 4, and a light distribution control device 6. These components may all be housed in the same housing, or some components may be provided outside the housing. For example, the adjustable light distribution lamp 2, imaging device 4, and light distribution control device 6 are housed in a lamp chamber. The lamp chamber is defined by a lamp body having an opening on the front side of the vehicle and a translucent cover attached to cover the opening of the lamp body. The imaging device 4 and light distribution control device 6 may be located outside the lamp chamber, for example, on the vehicle side. In this case, the imaging device 4 may be an on-board camera. The light distribution control device 6 may be configured, for example, in whole or in part, by a vehicle ECU. The vehicle on which the vehicle lighting system 1 is mounted may be a saddle-ride vehicle such as a motorcycle, or a non-saddle-ride vehicle such as a four-wheeled vehicle.

[0017] The variable light distribution lamp 2 is capable of irradiating a visible light beam L1 with a variable intensity distribution ahead of the vehicle. In other words, the variable light distribution lamp 2 is capable of irradiating the space ahead of the vehicle with light of different illuminances depending on the location. Hereinafter, each individual space into which the variable light distribution lamp 2 can irradiate light of different illuminances is referred to as an individual region R. The multiple individual regions R may be arranged, for example, in a line in the vehicle width direction or in a matrix. The variable light distribution lamp 2 receives information instructing a light distribution pattern PTN from the light distribution control device 6 and emits a visible light beam L1 having an intensity distribution corresponding to the light distribution pattern PTN. This forms the light distribution pattern PTN ahead of the vehicle. The light distribution pattern PTN can be understood as the two-dimensional illuminance distribution of an irradiation pattern 902 formed by the variable light distribution lamp 2 on a virtual vertical screen 900 ahead of the vehicle.

[0018] The variable light distribution lamp 2 may have any configuration, including, for example, a plurality of light sources arranged in a horizontal row or a matrix, and a lighting circuit that independently drives and lights each light source. Preferred examples of the light source include semiconductor light sources such as LEDs (light-emitting diodes), LDs (laser diodes), and organic or inorganic EL (electroluminescence). Each individual region R is associated with a light source, and each light source individually irradiates each individual region R with light.

[0019] The resolution of the variable light distribution lamp 2, in other words, the light distribution resolution, is, for example, about 4 to 20 pixels when the light sources are arranged in a horizontal row, and about 1,000 to 2,000,000 pixels when the light sources are arranged in a matrix. The resolution of the variable light distribution lamp 2 refers to the number of unit areas whose illuminance can be independently changed in the light distribution pattern PTN. As an example, each unit area corresponds one-to-one to each individual area R.

[0020] In addition, the variable light distribution lamp 2 may include a matrix-type pattern forming device such as a DMD (Digital Mirror Device) or a liquid crystal device, or a scanning optical pattern forming device that scans the area ahead of the vehicle with light from a light source, in order to form an illuminance distribution according to the light distribution pattern PTN.

[0021] The imaging device 4 is, for example, a camera that is sensitive to the visible light region and repeatedly captures images of the area in front of the vehicle. The imaging device 4 captures reflected light L2 of the visible light beam L1 from a target object in front of the vehicle. The imaging device 4 also captures light emitted by vehicles ahead, including leading and oncoming vehicles, and light emitted by self-luminous objects such as streetlights and electronic billboards. The image IMG generated by the imaging device 4 is sent to the light distribution control device 6. The image IMG is also sent to the vehicle ECU. The vehicle ECU can use the acquired image IMG for target recognition in ADAS and autonomous driving.

[0022] The image IMG that the light distribution control device 6 acquires from the imaging device 4 may be RAW image data, or may be image data that has undergone predetermined image processing by the imaging device 4. Furthermore, the case in which the light distribution control device 6 receives image data in which RAW image data generated by the imaging device 4 has been subjected to image processing by a processing device other than the imaging device 4 also falls under the category of acquiring an image IMG from the imaging device 4. In the following description, "image IMG based on the imaging device 4" means that it may be either RAW image data or data that has undergone image processing. Furthermore, the term "image IMG" may be used without distinguishing between the two types of image data. The resolution of the imaging device 4 is, for example, 300,000 to 5,000,000 pixels.

[0023] The light distribution control device 6 performs ADB control, which dynamically and adaptively controls the formation of the light distribution pattern PTN by the variable light distribution lamp 2, using the image IMG captured by the imaging device 4. The light distribution control device 6 can be configured with a digital processor, for example, a combination of a microcomputer including a CPU and a software program. Note that the light distribution control device 6 may also be configured with an FPGA (Field Programmable Gate Array), ASIC (Application Specific IC), or the like.

[0024] The light distribution control device 6 includes a control unit 8 configured with a CPU and the like, and a storage medium 10 configured with memory and storage. The control unit 8 includes, for example, a luminance analysis unit 12, a pattern determination unit 14, and a lamp control unit 16. The storage medium 10 stores computer programs and the like that are executed by the light distribution control device 6, more specifically, the control unit 8. Each unit included in the control unit 8 operates when an integrated circuit that constitutes the unit executes a program stored in the storage medium 10.

[0025] The luminance analysis unit 12 analyzes the luminance of each individual region R using the image IMG. In the luminance analysis, for example, the luminance analysis unit 12 binarizes the luminance value of each pixel in the image IMG using a predetermined luminance threshold value. Then, the luminance analysis unit 12 identifies predetermined high-luminance light points included in the binarized image. The luminance analysis unit 12 sends the analysis results to the pattern determination unit 14. The luminance threshold value can be set appropriately based on experiments or simulations, and is stored in advance in the storage medium 10.

[0026] The pattern determination unit 14 determines the illuminance of light to be irradiated onto each individual region R based on the analysis results of the luminance analysis unit 12, and determines the light distribution pattern PTN to be formed in the forward region. In determining the light distribution pattern PTN, the pattern determination unit 14 adjusts the illuminance of light to be irradiated onto the individual region R where the target forming the high-brightness light spot is located so that the luminance value of the high-brightness light spot included in the image IMG, in other words, the pixel values ​​of the pixels constituting the high-brightness light spot, approaches a predetermined target low luminance. Information regarding the target low luminance is pre-stored in the storage medium 10. The target low luminance is a luminance that can reduce the glare received by the driver of the vehicle due to light reflected from a light-reflecting object and allows the driver of the vehicle to see the light-reflecting object, and can be appropriately set based on experiments or simulations. In this embodiment, the target low luminance is lower than the luminance threshold value, but the target low luminance may also be the same value as the luminance threshold value. The pattern determination unit 14 sends information regarding the determined light distribution pattern PTN to the lamp control unit 16.

[0027] The lamp control unit 16 instructs the variable light distribution lamp 2 to form a light distribution pattern PTN. The lamp control unit 16 is configured, for example, with a known LED driver module (LDM). If the dimming method of the light source of the variable light distribution lamp 2 is analog dimming, the lamp control unit 16 adjusts the DC level of the drive current flowing through the light source. If the dimming method of the light source is PWM (Pulse Width Modulation) dimming, the lamp control unit 16 adjusts the average level of the drive current by switching the current flowing through the light source and adjusting the ratio of the on period. If the variable light distribution lamp 2 includes a DMD, the lamp control unit 16 controls the on / off switching of each mirror element constituting the DMD. If the variable light distribution lamp 2 includes a liquid crystal device, the lamp control unit 16 controls the light transmittance of the liquid crystal device. As a result, the light distribution pattern PTN is formed ahead of the vehicle.

[0028] Next, the light distribution control performed by the light distribution control device 6 will be described in detail. Fig. 2(A) is a diagram showing an image IMG0 obtained under the formation of a reference light distribution pattern PTN0. Fig. 2(B) is a diagram showing the analysis results of the luminance analysis unit 12. Note that although Fig. 2(A) shows seven individual regions R arranged in a horizontal row, the number and arrangement of the individual regions R are not limited to this.

[0029] In one example of light distribution control, the lamp control unit 16 first controls the variable light distribution lamp 2 to form a reference light distribution pattern PTN0. Information related to the reference light distribution pattern PTN0 is pre-stored in the storage medium 10. Once the reference light distribution pattern PTN0 is formed, the imaging device 4 generates an image IMG0 that shows the situation ahead of the vehicle under the formation of the reference light distribution pattern PTN0, as shown in FIG. 2A .

[0030] The reference light distribution pattern PTN0 is a light distribution pattern with a fixed illuminance that does not depend on the luminance value of each individual region R. Therefore, the reference light distribution pattern PTN0 does not include a light-blocking portion or a light-attenuating portion, which will be described later. As an example, the reference light distribution pattern PTN0 is a light distribution pattern that irradiates light with a predetermined maximum illuminance onto substantially the entire imaging range of the imaging device 4.

[0031] The luminance analysis unit 12 identifies high-brightness light points using the image IMG0 obtained when the reference light distribution pattern PTN0 is formed. That is, the luminance analysis unit 12 performs a luminance binarization process on the image IMG0 using the above-mentioned luminance threshold. In the example shown in FIG. 2A , a delineator 102 and an oncoming vehicle 104 are present ahead of the vehicle. The delineator 102, which is a light-reflecting object, is imaged as a high-brightness light point when the reference light distribution pattern PTN0 is formed. In the present disclosure, the light-reflecting object refers to at least one selected from the group consisting of a road sign, a delineator 102, and a signboard. Alternatively, the light-reflecting object refers to an object having a retroreflective surface at least in a portion visible from the vehicle. Furthermore, the headlamp of the oncoming vehicle 104 is self-luminous and is therefore imaged as a high-brightness light point.

[0032] 2B, the binarized image IMG1 obtained by binarizing the image IMG0 includes a high-brightness light spot 202 resulting from the delineator 102 and a high-brightness light spot 204 resulting from the headlamp of the oncoming vehicle 104. Therefore, the brightness analysis unit 12 can identify the high-brightness light spots 202 and 204 from the binarized image IMG1. As an example, the high-brightness light spots 202 and 204 are each a collection of multiple pixels.

[0033] The pattern determination unit 14 determines the light irradiated onto the individual region R where the target forming the high-brightness light spots 202, 204 is located as the target for illuminance adjustment. Hereinafter, this light will be referred to as target light as appropriate. The individual region R irradiated with the target light will be referred to as a target individual region. The pixel that captures the target individual region will be referred to as a target pixel. Note that light irradiated onto individual regions R surrounding the individual region R where the target forming the high-brightness light spots 202, 204 is located may also be included in the target light. In particular, when the individual regions R are arranged in a matrix, it can be effective to include the light irradiated onto the surrounding individual regions R in the target light.

[0034] For example, light irradiating the individual region R where the driver of the oncoming vehicle 104 is located is also included in the target light. The fact that the high-brightness light spot 204 originates from the headlamp of the oncoming vehicle 104 can be estimated based on the pairing of the high-brightness light spots 204, i.e., the fact that the two high-brightness light spots 204 are arranged at a predetermined interval in the vehicle width direction, and the position of the high-brightness light spot 204 in the binarized image IMG1. The position where the driver of the oncoming vehicle 104 is located can also be estimated based on the position of the high-brightness light spot 204. The same applies to the preceding vehicle. Note that the light blocking portion for the driver of the oncoming vehicle 104 may be set in a separate light distribution control. In this case, the light distribution control according to this embodiment can omit the process of determining the type of target forming the high-brightness light spot.

[0035] Figure 3 shows the transition of the illuminance of the target light for a high-brightness light spot 202 originating from a light-reflecting object. The vertical axis in Figure 3 represents the percentage of illuminance when the illuminance at the maximum rating of the variable light distribution lamp 2 is taken as 100%. Hereinafter, the illuminance at the maximum rating will be referred to as the upper limit illuminance where appropriate. For example, if the dimming method for the light source is PWM dimming, the illuminance can be rephrased as the ratio of the on period, that is, the duty ratio. The horizontal axis represents time.

[0036] When a high-brightness light spot 202 is detected in the individual region R irradiated with light of the maximum illuminance, the pattern determination unit 14 reduces the illuminance of the target light irradiated on the individual region R where the delineator 102 is located to a predetermined minimum illuminance by a third reduction amount C3d. Time t1 in Figure 3 indicates the timing when the delineator 102 appears in the target individual region. As an example, the maximum illuminance is 90% of the upper limit illuminance, and the minimum illuminance is 0% of the upper limit illuminance. The maximum and minimum illuminances are not limited to these values ​​and can be set appropriately based on experiments or simulations.

[0037] In the present embodiment, the amount of illuminance reduced by one update of the light distribution pattern PTN when reducing the illuminance from maximum illuminance to minimum illuminance is stored in advance in storage medium 10 as a basic reduction amount. Furthermore, the amount of illuminance increased by one update of the light distribution pattern PTN when increasing the illuminance from minimum illuminance to maximum illuminance is stored in advance in storage medium 10 as a basic increase amount. The basic reduction amount is determined based on the time required to reduce the illuminance from maximum illuminance to minimum illuminance and the number of light distribution patterns PTN that can be updated by the variable light distribution lamp 2 within this time. The basic increase amount is determined based on the time required to increase the illuminance from minimum illuminance to maximum illuminance and the number of light distribution patterns PTN that can be updated by the variable light distribution lamp 2 within this time.

[0038] The time for decreasing the illuminance from the maximum illuminance to the minimum illuminance and the time for increasing the illuminance from the minimum illuminance to the maximum illuminance can be set appropriately taking into consideration factors such as the discomfort felt by the driver of the vehicle due to a sudden change in illuminance, the glare felt by traffic participants such as the driver of the vehicle ahead and pedestrians due to a gradual change in illuminance, and the reduced visibility felt by the driver of the vehicle due to a gradual change in illuminance. As an example, the third decrease amount C3d is a basic decrease amount.

[0039] When the illuminance of the target light reaches a minimum illuminance, the high-brightness light spot 202 resulting from the light-reflecting object disappears from the image IMG. Therefore, the pattern determination unit 14 gradually increases the illuminance of the target light to bring the luminance value of the target pixel closer to the target low luminance. As a result, a dimming portion corresponding to the delineator 102 is formed in the light distribution pattern PTN. In this disclosure, the dimming portion "corresponding to the delineator 102" and the shading portion described below "corresponding to the oncoming vehicle 104" mean that when the light distribution pattern PTN is projected forward, the dimming portion overlaps with the delineator 102 and the shading portion overlaps with the oncoming vehicle 104.

[0040] The pattern determination unit 14 of this embodiment changes the illuminance by different amounts when changing the illuminance in the first illuminance region IR1, when changing the illuminance in the second illuminance region IR2, and when changing the illuminance in the third illuminance region IR3.

[0041] The first irradiance region IR1 belongs to an irradiance range equal to or less than a predetermined first irradiance threshold Th1. The second irradiance region IR2 belongs to an irradiance range greater than the first irradiance threshold Th1 and equal to or less than a second irradiance threshold Th2 that is greater than the first irradiance threshold Th1. The third irradiance region IR3 belongs to an irradiance range greater than the second irradiance threshold Th2. The first irradiance region IR1 may be the entire irradiance range equal to or less than the first irradiance threshold Th1, or a portion thereof. The second irradiance region IR2 may be the entire irradiance range greater than the first irradiance threshold Th1 and equal to or less than the second irradiance threshold Th2, or a portion thereof. The third irradiance region IR3 may be the entire irradiance range equal to or more than the second irradiance threshold Th2.

[0042] For example, the first illuminance threshold Th1 is 25% of the upper limit illuminance, and the second illuminance threshold Th2 is 50% of the upper limit illuminance. The first illuminance region IR1 is the entire range from the minimum illuminance to 25% illuminance. The second illuminance region IR2 is the entire range from over 25% illuminance to 50% illuminance. The third illuminance region IR3 is the entire range from over 50% illuminance to the maximum illuminance.

[0043] The first illuminance threshold Th1 is the upper limit of illuminance at which traffic participants do not experience glare, even if light with an illuminance equal to or less than the threshold is irradiated for a relatively long period of time. The second illuminance threshold Th2 is the upper limit of illuminance at which traffic participants do not experience glare, even if light with an illuminance equal to or less than the threshold is irradiated for a relatively short period of time. The first illuminance threshold Th1 and the second illuminance threshold Th2 can be set appropriately based on experiments or simulations and are pre-stored in the storage medium 10.

[0044] When changing the illuminance in the first illuminance region IR1, the pattern determination unit 14 changes the illuminance by a first change amount C1 that is smaller than the change amount when changing the illuminance in illuminance regions above the first illuminance threshold Th1, i.e., the second illuminance region IR2 and the third illuminance region IR3. Therefore, in the first illuminance region IR1, the illuminance of the target light increases by the first change amount C1 each time the light distribution pattern PTN is updated. The absolute value of the first change amount C1 is smaller than the absolute values ​​of the aforementioned basic decrease amount, basic increase amount, and third decrease amount C3d, as well as the absolute values ​​of the second change amount C2 and third increase amount C3u, which will be described later.

[0045] The pattern determination unit 14 changes the illuminance in the first illuminance region IR1 by the first change amount C1, provided that the change in illuminance occurs after the minimum illuminance but before the maximum illuminance is reached. In other words, the pattern determination unit 14 executes control to increase the illuminance of the target light by an amount different from the standard increase amount when the illuminance of the target light reaches the minimum illuminance. This allows the illuminance of the target light to be quickly minimized when a high-brightness light spot is detected. Therefore, if the high-brightness light spot is caused by a traffic participant, the glare experienced by the traffic participant can be more reliably reduced.

[0046] In the example shown in FIG. 3 , the illuminance of the target light is at a value at time t2 where the luminance value of the target pixel exceeds the target low luminance Br. Therefore, the pattern determination unit 14 reduces the illuminance of the target light in the light distribution pattern PTN to be formed next. In this embodiment, when reducing the illuminance in the first illuminance region IR1, the illuminance is also reduced by the first change amount C1. As a result, the illuminance of the target light again becomes an illuminance where the luminance value of the target pixel falls below the target low luminance Br. Thereafter, an increase by the first change amount C1 and a decrease by the first change amount C1 are repeated. Note that the first change amount C1 may be different values ​​when the illuminance is increased and when it is decreased.

[0047] Even if the illuminance of the target light repeatedly increases and decreases, the amount of change is the first change amount C1, which is sufficiently small. Therefore, the possibility that the driver of the vehicle will perceive it as flickering is extremely low. Furthermore, if the illuminance is changed by the first change amount C1, responsiveness when a new traffic participant appears in the target individual area may be reduced. However, because the illuminance is equal to or less than the first illuminance threshold Th1, glare to the new traffic participant can be suppressed.

[0048] The target low luminance Br is determined from the perspective of the glare received by the driver of the vehicle, visibility, etc., and can therefore be set to the same value regardless of the type of light-reflecting object. On the other hand, the illuminance corresponding to the target low luminance Br varies depending on the light reflectance of the target, even if the target low luminance Br is the same. The illuminance corresponding to the target low luminance Br is the illuminance at which the luminance value of the pixel capturing an image of the target when light of that illuminance is irradiated onto the target becomes the target low luminance Br, and will be referred to as the target illuminance hereinafter as appropriate. The target illuminance is relatively low for targets with relatively high light reflectance, such as the delineator 102, and relatively high for targets with relatively low light reflectance, such as pedestrians. Because the delineator 102 has a high light reflectance, the target illuminance falls within the first illuminance region IR1.

[0049] Time t3 in Figure 3 indicates the timing when the delineator 102 disappears from the target individual region. When the delineator 102 disappears, light reflection in the target individual region disappears, and the luminance value of the target pixel becomes substantially 0. Therefore, the pattern determination unit 14 increases the illuminance of the target light by the first change amount C1. As a result, the illuminance of the target light exceeds the first illuminance threshold Th1 and reaches the second illuminance region IR2.

[0050] When changing the illuminance in the second illuminance region IR2, the pattern determination unit 14 changes the illuminance by a second change amount C2 that is smaller than the change amount when changing the illuminance in an illuminance region above the second illuminance threshold Th2, i.e., the third illuminance region IR3. The absolute value of the second change amount C2 is greater than the absolute value of the first change amount C1 and smaller than the absolute values ​​of the third decrease amount C3d, the third increase amount C3u, the basic decrease amount, and the basic increase amount. Therefore, in the second illuminance region IR2, the illuminance of the target light increases more quickly than in the first illuminance region IR1.

[0051] Time t4 in Figure 3 indicates the timing when a new target object appears in the target individual area. The target illuminance of this target object is higher than the target illuminance of the delineator 102 and is included in the second illuminance area IR2. Such a target object may be a pedestrian or the like, whose light reflectance is lower than that of the delineator 102. This target object will be referred to as a low-light-reflecting object hereinafter.

[0052] In the example shown in FIG. 3 , the illuminance of the target light exceeds the target illuminance of the low-light-reflecting object at time t5. Therefore, the pattern determination unit 14 reduces the illuminance of the target light in the light distribution pattern PTN to be formed next. In this embodiment, when reducing the illuminance in the second illuminance region IR2, the illuminance is also reduced by the second change amount C2. As a result, the illuminance of the target light again becomes an illuminance at which the luminance value of the target pixel falls below the target low luminance Br. In other words, the illuminance of the target light again falls below the target illuminance. Thereafter, an increase by the second change amount C2 and a decrease by the second change amount C2 are repeated. Note that the second change amount C2 may be different values ​​when the illuminance increases and decreases.

[0053] Even if the illuminance of the target light repeatedly changes above and below the target illuminance of the low-light reflecting object, the change is sufficiently small, being the second change amount C2. Therefore, the driver of the vehicle is unlikely to perceive it as flickering. Furthermore, changing the illuminance by the second change amount C2 may reduce responsiveness when a new traffic participant appears in the target individual area. However, because the illuminance is equal to or less than the second illuminance threshold Th2, glare experienced by the new traffic participant can be reduced.

[0054] Time t6 in Figure 3 indicates the timing when the low-light-reflecting object disappears from the target individual region. When the low-light-reflecting object disappears, light reflection in the target individual region disappears, and the luminance value of the target pixel becomes essentially 0. Therefore, the pattern determination unit 14 increases the illuminance of the target light by the second change amount C2. As a result, the illuminance of the target light exceeds the second illuminance threshold Th2 and reaches the third illuminance region IR3.

[0055] When increasing the illuminance in the third illuminance region IR3, the pattern determination unit 14 increases the illuminance by a third increase amount C3u. The third increase amount C3u is greater than the first change amount C1 and the second change amount C2. Therefore, in the third illuminance region IR3, the illuminance of the target light increases more quickly than in the second illuminance region IR2. The illuminance of the target light then eventually recovers to its maximum illuminance. As an example, the third increase amount C3u is a general increase amount.

[0056] When the illuminance is within the third illuminance region IR3 and the illuminance must be reduced due to the appearance of a new traffic participant in the target individual region, the pattern determination unit 14 reduces the illuminance by the third reduction amount C3d. As an example, the third increase amount C3u is smaller than the third reduction amount C3d. In this case, priority can be given to reducing glare for the traffic participants. As another example, the third increase amount C3u is equal to or greater than the third reduction amount C3d, and preferably, the third increase amount C3u is greater than the third reduction amount C3d. In this case, priority can be given to improving visibility for the driver of the vehicle.

[0057] From the above explanation, the first illuminance region IR1 can be considered as a region where the illuminance of the target light changes slowly, the second illuminance region IR2 as a region where the illuminance of the target light changes at a medium speed, and the third illuminance region IR3 as a region where the illuminance of the target light changes at a high speed.

[0058] 4 is a diagram showing the transition of the illuminance of the target light for the high-brightness light spot 204 originating from a self-luminous object. The vertical and horizontal axes in FIG. 4 are the same as those in FIG. 3. When the high-brightness light spot 204 is detected in the individual region R irradiated with light of the maximum illuminance, the pattern determination unit 14 reduces the illuminance of the target light irradiated on the individual region R where the oncoming vehicle 104 is located to a predetermined minimum illuminance by a third reduction amount C3d. Time t7 in FIG. 4 indicates the timing when the oncoming vehicle 104 appears in the target individual region.

[0059] Because the headlamp of the oncoming vehicle 104 that forms the high-brightness light spot 204 is a self-luminous element, the luminance value of the target pixel does not change even when the illuminance of the target light reaches a minimum illuminance. Therefore, the pattern determination unit 14 cannot shift to control to increase the illuminance of the target light. As a result, as shown in FIG. 4 , the illuminance of the target light is maintained at a minimum illuminance. This forms a shading portion corresponding to the oncoming vehicle 104 in the light distribution pattern PTN. The shading portion can also be interpreted as a dimming portion with a minimum illuminance. The illuminance of light other than the target light is maintained at, for example, a maximum illuminance. The pattern determination unit 14 sends information about the determined light distribution pattern PTN to the lamp control unit 16.

[0060] As described above, the lamp control unit 16 controls the variable light distribution lamp 2 to form a reference light distribution pattern PTN0 that does not include any shading or dimming portions when forming the first light distribution pattern PTN in light distribution control. In subsequent light distribution controls, if the image IMG includes a high-brightness light spot, the illuminance of the target light is adjusted as described above, that is, a light distribution pattern PTN that includes shading or dimming portions is formed.

[0061] The pattern determination unit 14 detects the luminance value of the identified target pixel in the image IMG obtained under the formation of the updated light distribution pattern PTN, and determines the next light distribution pattern PTN based on the detection result. Furthermore, the luminance analysis unit 12 executes a process of identifying high-luminance light spots using the image IMG. This makes it possible to detect the appearance of new high-luminance light spots.

[0062] 5 is a flowchart showing an example of light distribution control. This flow is repeatedly executed at predetermined timings when an instruction to execute light distribution control is given by a light switch (not shown), for example, and the ignition is on.

[0063] The light distribution control device 6 controls the variable light distribution lamp 2 to form a light distribution pattern PTN (S101). If this is the first light distribution pattern to be formed in the light distribution control, the light distribution control device 6 controls the variable light distribution lamp 2 to form a reference light distribution pattern PTN0. The light distribution control device 6 also generates a formation flag for the light distribution pattern PTN and stores it in memory. Whether this is the first light distribution pattern to be formed can be determined based on the presence or absence of this formation flag. If this is not the first light distribution pattern to be formed, the light distribution control device 6 controls the variable light distribution lamp 2 to form the light distribution pattern PTN determined in the previous routine. Next, the light distribution control device 6 acquires an image IMG from the imaging device 4 (S102) and determines whether a high-brightness light point is present in the image IMG (S103).

[0064] If a high-brightness light spot is present (Y in S103), the light distribution control device 6 reduces the illuminance of the target light from the maximum illuminance to the minimum illuminance. That is, a light-blocking portion is determined in the light distribution pattern PTN to be formed next (S104). Note that if the illuminance of the target light is less than the maximum illuminance, that illuminance is maintained in this step. If a high-brightness light spot is not present (N in S103), the light distribution control device 6 skips step S104.

[0065] Next, the light distribution control device 6 determines whether the light distribution pattern PTN formed in step S101 has a light-attenuating portion or a light-blocking portion (S105). If the light distribution pattern PTN does not have a light-attenuating portion or a light-blocking portion (N in S105), the light distribution control device 6 maintains the illuminance of the light irradiated to each individual region R (S106) and ends this routine. The light distribution pattern PTN determined through step S106 is formed in step S101 of the next routine.

[0066] If the light distribution pattern PTN formed in step S101 has a dimming portion or a light-shielding portion (Y in S105), the light distribution control device 6 determines whether there is a dimming portion where the luminance value of the target pixel exceeds the target low luminance (S107). If there is a dimming portion where the luminance value exceeds the target low luminance (Y in S107), the light distribution control device 6 reduces the illuminance of the corresponding dimming portion by an amount corresponding to the illuminance region to which the illuminance belongs (S108). If there is no dimming portion where the luminance value exceeds the target low luminance (N in S107), the light distribution control device 6 skips step S108.

[0067] Next, the light distribution control device 6 increases the illuminance of the dimming portion where the luminance value of the corresponding pixel is equal to or less than the target low luminance by an amount corresponding to the illuminance region to which the illuminance belongs (S109), and ends this routine. The light distribution pattern PTN determined through step S109 is formed in step S101 of the next routine. Note that if the light distribution pattern PTN only has dimming portions whose luminance values ​​exceed the target low luminance, the processing in step S109 is essentially omitted. In addition, the formation flag for the light distribution pattern PTN is deleted when an instruction to stop light distribution control is issued by the light switch or when the ignition is turned off.

[0068] This embodiment includes a computer program executed by the light distribution control device 6. This computer program causes the light distribution control device 6 to perform a function of changing the illuminance in a first illuminance region IR1 that is equal to or less than a predetermined first illuminance threshold Th1 by a first change amount C1 that is smaller than when changing the illuminance in an illuminance region that exceeds the first illuminance threshold Th1. This embodiment also includes a storage medium 10 that stores the computer program.

[0069] As described above, the light distribution control device 6 according to this embodiment changes the illuminance in the first illuminance region IR1, which is equal to or less than the first illuminance threshold Th1, by a first change amount C1 that is smaller than the change amounts in the second illuminance region IR2 and the third illuminance region IR3, which are equal to or greater than the first illuminance threshold Th1. Low-illuminance light included in the first illuminance region IR1 is unlikely to cause glare to traffic participants, even if it is irradiated on them. Therefore, the change amount of illuminance can be set small. Furthermore, by reducing the change amount of illuminance, it is possible to make flickering less noticeable to the driver of the vehicle. Therefore, it is possible to easily achieve both improved visibility for the driver of the vehicle and reduced glare for traffic participants.

[0070] Furthermore, the light distribution control device 6 adjusts the illuminance of the target light so that the luminance values ​​of the pixels that constitute the high-luminance light spot 202 caused by the light-reflecting object approach the target low luminance. This makes it possible to reduce the glare caused by the light-reflecting object while maintaining the driver's visibility of the light-reflecting object.

[0071] Furthermore, in recent years, research and development of advanced driver-assistance systems (ADAS) and autonomous driving technologies has been progressing as technologies to assist drivers in driving operations. ADAS and autonomous driving technologies use imaging devices such as cameras, which are like mechanical eyes, to grasp the situation ahead of the vehicle and perform vehicle control according to the situation. When high-intensity light is reflected from a light-reflecting object, whiteout occurs in the image generated by the imaging device, which can hinder understanding of the situation. Furthermore, weakening the light irradiation on the light-reflecting object makes it difficult for the imaging device to detect the light-reflecting object. Therefore, the light distribution control according to this embodiment is also useful for improving the accuracy of ADAS and autonomous driving technologies.

[0072] Furthermore, in the second illuminance region IR2, which exceeds the first illuminance threshold Th1 and is equal to or smaller than the second illuminance threshold Th2, the light distribution control device 6 changes the illuminance by a second change amount C2 that is smaller than the change amount in the third illuminance region IR3, which exceeds the second illuminance threshold Th2. This makes it easier to achieve both improved visibility for the driver of the vehicle and reduced glare for traffic participants. Note that it is assumed that there are fewer targets whose target illuminance is included in the second illuminance region IR2 than in the first illuminance region IR1. Therefore, the second illuminance region IR2 and the third illuminance region IR3 do not need to be distinguished. The light distribution control device 6 may also have three or more illuminance thresholds. In this case, the amount of change in illuminance is adjusted for four or more illuminance regions.

[0073] Furthermore, in the third illuminance region IR3 exceeding the second illuminance threshold Th2, the light distribution control device 6 reduces the illuminance by the third decrease amount C3d and increases the illuminance by the third increase amount C3u that is smaller than the third decrease amount C3d. In this case, it is possible to prioritize reducing glare for traffic participants. Alternatively, the light distribution control device 6 reduces the illuminance in the third illuminance region IR3 by the third decrease amount C3d and increases the illuminance by the third increase amount C3u that is equal to or greater than the third decrease amount C3d. In this case, it is possible to prioritize improving visibility for the driver of the vehicle.

[0074] Furthermore, when a high-brightness light spot 202, 204 is detected in the forward area illuminated by light of maximum illuminance, the light distribution control device 6 reduces the illuminance of the target light by a third reduction amount C3d to the minimum illuminance. Then, on the condition that the illuminance change occurs after the minimum illuminance but before the maximum illuminance is reached, the light distribution control device 6 changes the illuminance in the first illuminance area IR1 by a first change amount C1. These measures further reduce glare for traffic participants.

[0075] The above describes the embodiments of the present invention in detail. The above-described embodiments merely illustrate specific examples of implementing the present invention. The content of the embodiments does not limit the technical scope of the present invention, and many design modifications, such as changes, additions, and deletions of components, are possible within the scope of the inventive concept defined in the claims. A new embodiment incorporating design modifications will combine the effects of the combined embodiments and modifications. In the above-described embodiments, design modifications that are possible are emphasized by using notations such as "in this embodiment" or "in this embodiment," but design modifications are also permitted even in areas without such notation. Any combination of the above components is also valid as an aspect of the present invention. Hatching in cross sections in the drawings does not limit the materials of the hatched objects.

[0076] The invention according to the above-described embodiment may be specified by the following items: [Item 1] A light distribution control device (6) that controls formation of a light distribution pattern (PTN) by a variable light distribution lamp (2) using an image (IMG) based on an imaging device (4) that images an area ahead of a vehicle, wherein, when changing the illuminance in a first illuminance region (IR1) that is equal to or less than a predetermined first illuminance threshold (Th1), the light distribution control device (6) changes the illuminance by a first change amount (C1) that is smaller than the change amounts (C2, C3d, C3u) when changing the illuminance in illuminance regions (IR2, IR3) that exceed the first illuminance threshold (Th1). [Item 2] The light distribution control device (6) according to Item 1, wherein, when changing the illuminance in a second illuminance region (IR2) that is above a first illuminance threshold (Th1) and is equal to or smaller than a second illuminance threshold (Th2) that is greater than the first illuminance threshold (Th1), the illuminance is changed by a second change amount (C2) that is smaller than the change amounts (C3d, C3u) when changing the illuminance in an illuminance region (IR3) that is above the second illuminance threshold (Th2). [Item 3] The light distribution control device (6) according to Item 2, wherein, when lowering the illuminance in a third illuminance region (IR3) that is above the second illuminance threshold (Th2), the illuminance is lowered by a third decrease amount (C3d), ​​and when increasing the illuminance in the third illuminance region (IR3), the illuminance is increased by a third increase amount (C3u) that is smaller than the third decrease amount (C3d). [Item 4] The light distribution control device (6) according to Item 2, wherein when reducing the illuminance in a third illuminance region (IR3) exceeding the second illuminance threshold value (Th2), the illuminance is reduced by a third reduction amount (C3d), ​​and when increasing the illuminance in the third illuminance region (IR3), the illuminance is increased by a third increase amount (C3u) equal to or greater than the third reduction amount (C3d). [Item 5] The light distribution control device (6) according to Item 3 or Item 4, wherein when a predetermined high-brightness light spot (202, 204) is detected in a forward region irradiated with light of a predetermined maximum illuminance, the illuminance of light irradiated to the forward region is reduced by the third reduction amount (C3d) to a predetermined minimum illuminance. [Item 6] The light distribution control device (6) according to Item 5, wherein the illuminance is changed in the first illuminance region (IR1) by a first change amount (C1), provided that the illuminance change occurs after the minimum illuminance has passed and before the maximum illuminance has been reached.[Item 7] A vehicle lighting system (1) comprising: an imaging device (4) that images an area ahead of the vehicle; a variable light distribution lamp (2) that can irradiate a visible light beam (L1) having a variable intensity distribution toward the area ahead of the vehicle; and a light distribution control device (6) according to any of Items 1 to 6. [Item 8] A computer program executed by the light distribution control device (6) that controls formation of a light distribution pattern (PTN) by the variable light distribution lamp (2) using an image (IMG) based on the imaging device (4) that images an area ahead of the vehicle, the computer program causing the light distribution control device (6) to perform a function of changing the illuminance in a first illuminance range (IR1) that is equal to or less than a predetermined first illuminance threshold (Th1) by a first change amount (C1) that is smaller than when changing the illuminance in illuminance ranges (IR2, IR3) that exceed the first illuminance threshold (Th1). [Item 9] A light distribution control method for controlling the formation of a light distribution pattern (PTN) by a variable light distribution lamp (2) using an image (IMG) based on an imaging device (4) that images an area in front of a vehicle, the light distribution control method including, when changing the illuminance in a first illuminance region (IR1) that is equal to or less than a predetermined first illuminance threshold value (Th1), changing the illuminance by a first change amount (C1) that is smaller than the change amounts (C2, C3d, C3u) when changing the illuminance in illuminance regions (IR2, IR3) that exceed the first illuminance threshold value (Th1).

[0077] The present invention can be used in a light distribution control device, a vehicle lighting system, and a computer program.

[0078] 1 Vehicle lighting system, 2 Variable light distribution lamp, 4 Imaging device, 6 Light distribution control device, 8 Control unit, 10 Storage medium, C1 First change amount, C2 Second change amount, C3d Third decrease amount, C3u Third increase amount, IR1 First illuminance region, IR2 Second illuminance region, IR3 Third illuminance region, Th1 First illuminance threshold, Th2 Second illuminance threshold.

Claims

1. A light distribution control device that controls the formation of a light distribution pattern by a variable light distribution lamp using an image based on an imaging device that images the area in front of a vehicle, wherein when changing the illuminance in a first illuminance region below a predetermined first illuminance threshold, the illuminance is changed by a first amount of change that is smaller than the amount of change when changing the illuminance in an illuminance region above the first illuminance threshold.

2. A light distribution control device as described in claim 1, wherein, when the illuminance is changed in a second illuminance region above the first illuminance threshold and equal to or less than a second illuminance threshold greater than the first illuminance threshold, the illuminance is changed by a second amount of change which is smaller than the amount of change when the illuminance is changed in an illuminance region above the second illuminance threshold.

3. A light distribution control device as described in claim 2, wherein when reducing the illuminance in a third illuminance region exceeding the second illuminance threshold value, the illuminance is reduced by a third reduction amount, and when increasing the illuminance in the third illuminance region, the illuminance is increased by a third increase amount smaller than the third reduction amount.

4. A light distribution control device as described in claim 2, wherein when lowering the illuminance in a third illuminance region exceeding the second illuminance threshold value, the illuminance is lowered by a third reduction amount, and when increasing the illuminance in the third illuminance region, the illuminance is increased by a third increase amount equal to or greater than the third reduction amount.

5. A light distribution control device as described in claim 3 or 4, wherein when a predetermined high-brightness light spot is detected in a forward area where light of a predetermined maximum illuminance is irradiated, the illuminance of the light irradiated to the forward area is reduced to a predetermined minimum illuminance by the third reduction amount.

6. The light distribution control device according to claim 5, wherein the illuminance is changed by the first change amount in the first illuminance region on condition that the change in illuminance occurs after passing through the minimum illuminance and before reaching the maximum illuminance.

7. A vehicle lighting system comprising: an imaging device that images an image in front of the vehicle; a variable light distribution lamp that can irradiate a visible light beam having a variable intensity distribution in front of the vehicle; and a light distribution control device according to any one of claims 1 to 4.

8. A computer program executed by a light distribution control device that controls the formation of a light distribution pattern by a variable light distribution lamp using an image based on an imaging device that images the area in front of the vehicle, the computer program causing the light distribution control device to execute a function of changing the illuminance by a first amount of change that is smaller when changing the illuminance in a first illuminance region that is equal to or less than a predetermined first illuminance threshold value than when changing the illuminance in an illuminance region that exceeds the first illuminance threshold value.

Images