This application claims the benefit of and priority to Korean Patent Application No. 10-2020-0102046, filed on Aug. 13, 2020, which is hereby incorporated by reference as if fully set forth herein.

BACKGROUND

Field of the Disclosure

The present disclosure relates to a vehicle lighting device and a method of controlling luminance thereof, and more particularly to a vehicle lighting device using an infrared camera and to a method of controlling luminance thereof.

Discussion of the Related Art

In general, a vehicle is equipped with a vehicle lighting device for stably securing a driver's field of view or notifying other vehicles of the traveling state of the vehicle when traveling in a dimly lit environment.

Such a vehicle lighting device operates according to the traveling state of a vehicle in order to secure the driver's safety. Such a vehicle lighting device includes headlights mounted to the front side of the vehicle and taillights mounted to the rear side of the vehicle.

The headlights mainly serve to illuminate the area in front of the vehicle when the vehicle travels at night.

The taillights include a brake lamp, which is turned on when the driver operates a brake system and include a turn-signal lamp, which indicates the direction in which the vehicle is to turn.

Generally, the human eye is sensitive even to low-intensity light in environments in which the amount of light is small (e.g. at nighttime), but is insensitive even to high-intensity light in environments in which the amount of light is large (e.g. during the daytime).

Therefore, if the vehicle lighting device emits a constant intensity of light regardless of the time of day, the driver may suffer from eye fatigue due to the relatively high light intensity when driving at night, and may suffer from poor visibility due to the relatively low light intensity when driving during the daytime, which may cause an accident.

In order to solve the above problems, there has been proposed a method of controlling a vehicle lighting device, which is disclosed in Korean Patent Registration No. 10-1393349. According to this conventional control method, the intensity of light emitted from the vehicle lighting device varies according to the luminance or the weather conditions outside the vehicle.

Described in more detail, according to the conventional method of controlling a vehicle lighting device, when the detected luminance outside the vehicle falls within a predetermined luminance range, a first lamp radiates light having a predetermined intensity corresponding to the luminance range. When it is detected that fog is present in the environment around the vehicle, a second lamp is turned on.

In addition, according to the conventional method of controlling a vehicle lighting device, when it is detected that the brake system of the vehicle is operating, a third lamp radiates light having a predetermined intensity corresponding to the detected luminance. When it is detected that it is raining outside the vehicle and the detected amount of rainfall is within a predetermined rainfall amount range, the second lamp is turned on. When the brake system operates while traveling in the rain, the third lamp radiates light having a predetermined intensity corresponding to the detected amount of rainfall.

However, in the conventional method of controlling a vehicle lighting device, a large number and variety of sensor modules are required in order to detect the surroundings of the vehicle, and the logic for controlling the sensor modules is very complicated.

Therefore, the conventional method of controlling a vehicle lighting device may increase the cost of manufacturing the vehicle due to the application of a large number and variety of sensor modules, and may cause quality degradation and frequent occurrence of errors due to complicated logic.

In addition, according to the conventional method of controlling a vehicle lighting device, the luminance of the vehicle lighting device, which is controlled by the determination logic in response to the detected surroundings of the vehicle, may be somewhat different from the luminance that is desired by the driver in the actual situation around the vehicle.

SUMMARY

Accordingly, the present disclosure is directed to a vehicle lighting device and a method of controlling luminance thereof that substantially obviate one or more problems due to limitations and disadvantages of the related art.

An object of the present disclosure is to provide a vehicle lighting device and a method of controlling luminance thereof. The vehicle lighting device and method are capable of appropriately controlling luminance suitable for a driver in a daytime-driving mode and a nighttime-driving mode using a camera for monitoring the driver without using a separate luminance sensor.

However, the objects to be accomplished by the embodiments are not limited to the above-mentioned objects. Other objects not mentioned herein should be clearly understood by those having ordinary skill in the art to which the embodiments pertain from the following description.

In order to accomplish the above and other objects, a vehicle lighting device according to an embodiment of the present disclosure is provided. The vehicle lighting device may include: a camera module configured to capture an image of the driver's face; a sensing unit configured to detect the surroundings of a vehicle; a lighting unit including at least one light source to illuminate the interior of the vehicle; and a controller. The controller may be configured: to acquire information on a daytime mode and a nighttime mode through the sensing unit; to acquire information on an infrared brightness level or information on the size of the pupil of the driver's eye based on the image of the driver's face captured by the camera module; and to control the luminance of the lighting unit in response to the acquired information.

In order to accomplish the above and other objects, a method of controlling luminance of a vehicle lighting device according to a first embodiment of the present disclosure is provided. The method may include: determining a daytime mode or a nighttime mode based on an ambient luminance detected by an luminance sensor; capturing an image of the face of the driver through a camera module and repeatedly measuring an infrared brightness level from the captured image of the face of the driver; and controlling the luminance of a lighting unit for the daytime mode or the nighttime mode in response to a change in the measured infrared brightness level.

In order to accomplish the above and other objects, a method of controlling luminance of a vehicle lighting device according to a second embodiment of the present disclosure is provided. The method may include: determining a daytime mode or a nighttime mode based on an ambient luminance detected by an luminance sensor; capturing an image of the pupil of the driver through a camera module and repeatedly measuring the size of the pupil of the driver in the captured image; and controlling the luminance of a lighting unit for the daytime mode or the nighttime mode in response to a change in the measured size of the pupil of the driver.

In order to accomplish the above and other objects, a method of controlling luminance of a vehicle lighting device according to a third embodiment of the present disclosure is provided. The method may include: determining a daytime mode or a nighttime mode based on an ambient luminance detected by an luminance sensor; capturing an image of the face of the driver through a camera module and repeatedly measuring an infrared brightness level from the captured image of the face of the driver; capturing an image of the pupil of the driver through the camera module and repeatedly measuring a size of the pupil of the driver in the captured image; calculating a change in the measured infrared brightness level; calculating a change in the measured size of the pupil of the driver; and controlling the luminance of a lighting unit for the daytime mode or the nighttime mode in response to the calculated change in the infrared brightness level and the calculated change in the size of the pupil of the driver.

The controlling the luminance of the lighting unit may include: establishing a lookup table in which a plurality of levels based on which the luminance of the lighting unit is controlled is set and in which duty ratios at which the lighting unit is driven in the daytime mode and the nighttime mode are respectively set in the plurality of levels; selecting a level by lowering or raising a current level, among the plurality of levels, in response to a change in the infrared brightness level and/or a change in the size of the pupil of the driver; and driving the lighting unit at a duty ratio of a daytime mode or a nighttime mode corresponding to the selected level.

