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A headlamp beam tester is a means to check both the orientation and intensity of a vehicle headlamp to ensure that it meets a minimum standard for the country of use of the vehicle. In the United Kingdom, a headlamp beam tester is used to assess the headlight during an MOT test but in order to be used it must be approved as suitable for use in the scheme. A list of acceptable headlight testers for use within the MOT test scheme is listed on the Department of Transport website.
A headlight tester comprises a fully adjustable single optical collimated light lens assembly which is rail mounted and designed to prevent any distortion of the optical lens supporting structure during general use, such as when aligning the lens to the vehicle or manoeuvring the assembly along the rails.
The optical lens itself, which is designed to accurately focus all types of vehicle headlamp, and is fully adjustable in the vertical plane; achieved by mounting it to a vertical column. The measurement travel of the optical lens is between the heights of 500mm and 1500mm, which allows for the testing of all vehicles up to and including heavy goods vehicles. Finally, at the top of the lens mounting column is a mirror or laser which allows the headlight tester to be aligned with the longitudinal axis of the presented vehicle.
During a headlamp inspection, the vehicle headlamp is aimed through the lens at an aiming screen target which has four solid red or blue lines showing the 0.5%, 1.25%, 2% and 2.75% positions about the centreline. The % increments are only in the 3.25% and 4% positions when the tester is to be used specifically with HGV’s. The measurement is taken manually by assessing the exact beam pattern on the aiming screen by a trained technician.
A feature often included as part of such a tester is a method by which the intensity of the beam can be measured. This is achieved with a light meter or Lux meter which is incorporated within the assembly itself. This can be used to not only measure the intensity of the dipped beams but also to measure and compare the full beam intensity.