Headlamp detection is an indispensable part of vehicle safety performance detection. The main parameters of headlamp diagnosis are luminous intensity and beam position. When the luminous intensity is insufficient or the position of the beam is slanted, it will cause the driver's vision unclear at night, or make the oncoming driver dazzled, which will greatly affect the driving safety. Therefore, it is necessary to detect and correct the luminous intensity and position of the headlamp regularly. The technical condition of headlamp can be detected by screen method and headlamp calibrator.
1、 Position standard of light beam and screen detection method
（1） Screen detection
(1) Preparations before testing
According to GB7258-2004 technical conditions for motor vehicle operation safety, when testing the position of headlamp beam by screen method, the inspection site shall be flat, the screen and site shall be straight, and the inspected vehicle shall be carried out under the condition of no-load, normal tire pressure and one driver. Stop the two vehicles in front of the screen and perpendicular to the screen, so that the headlamp reference center is 10m away from the screen. On the screen, determine the horizontal reference line equal to the height h from the headlamp reference center to the ground and the left and right headlamp reference center position line based on the projection line of the vehicle longitudinal center plane on the screen. The offset values of the horizontal or vertical direction of the left and right far and near beams are measured respectively.
There are three vertical lines and three horizontal lines on the screen:
The middle vertical line V-V is aligned with the longitudinal center vertical plane of the inspected vehicle.
The vertical lines vl-vl and vr-vr on both sides are respectively the vertical lines of the reference center of the left and right headlamp of the inspected vehicle.
The H-H line in the horizontal line is the same height as the reference center of the inspected vehicle headlamp, and the height from the ground is h; h is the height from the reference center of the inspected vehicle headlamp to the ground, and its value depends on the inspected vehicle type.
The middle horizontal line is the same height as the center of the high beam of the headlamp of the inspected vehicle, and the height from the ground is H1, H1 = 0.85-0.90h.
The lower horizontal line is the same height as the center of the low beam of the headlamp of the inspected vehicle, and the height from the ground is H2, h2 = 0.60-0.80h.
(2) Detection method
During the detection, cover the headlamp on one side first, and then turn on the low beam switch of the headlamp. The corner of the low beam cut-off line or the beam center of the uncovered headlamp shall fall on the intersection position of the lower horizontal line and vl-vl or vr-vr line in the figure, otherwise, it is the deflection of the beam irradiation position. The deflection direction and amount can be measured directly on the screen. Using the same method, check the position of the low beam of the other headlamp.
According to the detection standard, when detecting and adjusting the illumination position of the headlamp beam, the detection and adjustment of the low beam shall be the main method for the far and low beam lamps. For high beam single beam headlamps, the illumination position of the high beam shall be detected. The center of the beam shall be at the intersection of the middle horizontal line and vl-vl or vr-vr line.
It is easy to detect the headlamp by screen method, but it can only detect the illumination position of the beam, not the luminous intensity. In order to adapt to the detection of different models, the screen needs to be changed frequently, which is inefficient, and at the same time, it needs to occupy a large area. Therefore, the headlamp calibrator is widely used to detect the automobile headlamp.