Council Directive of 1 March 1971 on the approximation of the laws of the Member States relating to the rear-view mirrors of motor vehicles (71/127/EEC) (repealed) (c. 127)

[F1 ANNEX II U.K. DESIGN SPECIFICATIONS AND TESTS REQUIRED FOR EEC COMPONENT TYPE-APPROVAL OF REAR-VIEW MIRRORS

Textual Amendments

F1 Substituted by Commission Directive of 18 February 1985 adapting to technical progress Council Directive 71/127/EEC on the approximation of the laws of the Member States relating to the rear-view mirrors of motor vehicles (85/205/EEC).

Appendix 1 to Annex II TEST METHOD FOR DETERMINING REFLECTIVITY

3. PROCEDURE U.K.

3.1. Direct calibration method U.K.

In the direct calibration method, air is used as the reference standard. This method is applicable for those instruments which are so constructed as to permit calibration at the 100 % point by swinging the receiver to a position directly on the axis of the light source (see Figure 1).

It may be desired in some cases (such as when measuring low-reflectivity surfaces) to use an intermediate calibration point (between 0 and 100 % on the scale) with this method. In these cases, a neutral density filter of known transmittance shall be inserted in the optical path, and the calibration control shall then be adjusted until the meter reads the percentage transmission of the neutral density filter. This filter shall be removed before reflectivity measurements are performed.

3.2. Indirect calibration method U.K.

The indirect calibration method is applicable in the case of instruments with fixed source and receiver geometry. A properly calibrated and maintained reflectance standard is required. This reference standard should preferably be a flat mirror with a reflectance value as near as possible to that of the test samples.

3.3. Flat mirror measurement U.K.

The reflectance of flat mirror samples can be measured on instruments employing either the direct or the indirect calibration method. The reflectance value is read directly from the indicating meter.

3.4. Non-flat (convex) mirror measurement U.K.

Measurement of the reflectance of non-flat (convex) mirrors requires the use of instruments which incorporate an integrating sphere in the receiver unit (see Figure 2). If the instrument indicating meter indicates n _e divisions with a standard mirror of E % reflectance, then, with a mirror of unknown reflectance, n _x divisions will correspond to a reflectance of X %, in accordance with the formula:

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