1. Field of the Invention
The present invention relates to a vehicular lamp that includes a lamp unit comprised of a reflector and a light source and provided in a lamp chamber, which is formed by a lamp body having a front opening and a transparent front cover attached to the front opening of the lamp body, so that the optical axis direction of the lamp unit is adjusted by a tilting movement adjustment mechanism.
2. Description of the Related Art
Laser radar mechanisms have conventionally been in practical use as apparatuses to detect a separation distance and a relative velocity between a vehicle and an object that is present so as to oppose the traveling direction of the vehicle or the periphery of the vehicle.
Such laser radar mechanisms detect the separation distance and the relative velocity with respect to an object by emitting a laser beam toward the object and then receiving a reflection beam from the object.
Conventionally, such laser radar mechanisms are fixed to the front of a vehicle body in order to, for example, detect vehicular front information such as an inter-vehicular distance between the vehicle and another vehicle traveling in front of the vehicle.
However, when the laser beam emitting portion or the laser beam receiving portion of such a laser radar mechanism that is fixed to the front of the vehicle body while being exposed to the surroundings becomes dirty due to mud splashes while the vehicle is in operation or the like, the detection ability of the laser radar mechanism would be lowered. When this occurs, then it becomes impossible to achieve a predetermined level of detection performance. To cope with this situation, it has been suggested that, for example, a laser radar mechanism be covered by an exclusive-use cover that surrounds the laser radar mechanism. However, this leads to a problem that the installation of the exclusive-use cover makes the cost of the vehicle higher.
In addition, when such a laser radar mechanism is fixed to the front of a vehicle body, another problem arises. The detection angle of the laser radar mechanism is affected by changes in the posture of the vehicle.
In order to solve these problems, a proposal has been made in which a front information detecting means such as a laser radar mechanism is fixed to a lamp unit that is installed in a vehicular lamp as disclosed in U.S. Pat. No. 6,459,476. In this vehicular lamp, the lamp unit is provided inside a lamp-chamber so that the optical axis direction of the lamp unit is adjusted by a tilting movement adjustment mechanism (i.e., optical axis direction adjusting means), wherein the lamp chamber is comprised of a lamp body that has a front opening in the front thereof and a transparent front cover attached to the front opening of the lamp body, and the lamp unit is comprised of a reflector and a light source.
In this structure, since the laser radar mechanism is housed in the lamp chamber that is installed in the vehicular lamp, the laser radar mechanism is protected from, for instance, mud splashes during the operation of the vehicle, and an exclusive-use cover is not required to be installed.
In addition, since the laser radar mechanism is able to make a tilting movement together or integrally with the lamp unit by the tilting movement adjustment mechanism, and since the radiation angle of the radiated laser beam can be appropriately adjusted, the reflection beam that corresponds to the front information is not affected by the changes in the posture of the vehicle, and it is possible to accurately detect the vehicular front information.
However, when the laser radar mechanism is attached to the lamp unit itself that is driven by the tilting movement adjustment mechanism as described above, the load applied on the tilting movement adjustment mechanism is extremely large since the laser radar mechanism is generally quite heavy. As a result, it is necessary to increase the strength of the mechanism elements of the tilting movement adjustment mechanism; and in addition, a smooth performance of the tilting movement adjusting operation by the tilting movement adjustment mechanism is prevented.