Headlight intensity standard and instrument testing method in headlight inspection and testing

Automobile headlight detection is an indispensable part of automobile safety performance detection. The main parameters of headlight diagnosis are luminous intensity and beam position. When the light intensity is insufficient or the beam irradiation position is skewed, it will cause the driver's vision is unclear at night, or make the driver blinding, will greatly affect the driving safety. Therefore, the luminescence intensity and beam irradiation position of the headlamp should be detected and corrected regularly. In the test library encyclopedia shared before the inspection standards and methods of automobile headlight (A) introduced the headlight technical status, available screen method and headlight calibration instrument detection. Today, I will continue to introduce the headlight intensity standard and instrument detection method in the headlight inspection and detection.

Ii. Headlamp luminous intensity standard and instrument testing method

(1) Inspection and testing standards for the luminescence intensity of headlamps

GB7258-2017 "Technical Conditions for Safety of Motor Vehicle Operation" stipulates that the luminescence intensity of each headlight beam of motor vehicle should meet the requirements in Table 2. When testing, its power supply system should be in the charging state.

(1) When two symmetrical lights of a four-light motor vehicle meet the requirements of the two-light system, they are considered qualified

(2) Headlight calibration instrument to detect luminescence intensity and optical axis deflection

Headlight calibration instrument is a special equipment used to detect the headlight luminescence intensity and the deflection of the optical axis, which is placed on the opposite side of the vehicle under test according to a certain measuring distance. The deflection of the optical axis represents the position of the beam.

1. Detection principle of headlight corrector

There are many types of headlamp correctors, but the basic detection principle is similar. Generally, the photocell which can convert the absorbed light energy into current is used as the sensor. According to the size and proportion of the current generated by the headlamp main beam irradiation of the photocell, the headlamp luminous intensity and optical axis deflection are measured.

(1) Detection principle of luminescence intensity

The circuit for measuring the luminescence intensity of headlamp is composed of photometer, variable resistance and photocell, as shown in FIG. 3. According to the specified distance, the headlamp illuminates the photocell, and the photocell generates the corresponding photocurrent according to the size of the light intensity to make the photometer pointer swing, indicating the luminous intensity of the headlamp.

(2) Detection principle of optical axis deflection

The circuit to measure the deflection of the headlight optical axis is composed of two pairs of photocells. The left and right pairs of photocells are connected with the left and right deflection indicator, which is used to detect the left and right deflection of the beam center. The upper and lower pairs of photocell S are connected with the upper and lower skew indicator, which is used to detect the amount of the upper and lower skew of the beam center. When the photocell is irradiated by the headlight beam, if the beam irradiation direction is skewed, it will respectively make the photocell receiving surface is not consistent, and therefore the current generated is not consistent. The current difference generated by the photocell makes the pointer of the upper and lower skew indicator and the left and right skew indicator swing respectively so as to detect the skew direction and the skew amount of the optical axis.

If the appropriate adjusting mechanism is used to adjust the position of the light shining on the photocell, so that each pair of photocells receives the same illumination on the left, S, S, S and S above and S below, the output current of each pair of photocells is equal, and the pointer of the two deflections indicator points to zero, and the adjustment amount reflects the deflection amount of the center of the beam. When the pointer of the skew indicator is at zero, the light intensity of the photocell is strong. The sum of the output current of the four photocells indicates the luminous intensity of the headlamp.