Directive 2003/97/EC of the European Parliament and of the Council (repealed)Show full title

Appendix 1

Procedure for determining the radius of curvature ‘r’ of the reflecting surface of a mirror

1. Measurement U.K.

1.1. Equipment U.K.

A ‘spherometer’ similar to the one described in Figure 3 having the indicated distances between the tracing pin of the dial gauge and the fixed legs of the bar is used.

1.2. Measuring points U.K.

1.2.1. The principal radii of curvature shall be measured at three points situated as close as possible to positions at one-third, one-half and two-thirds of the distance along the arc of the reflecting surface passing through the centre of this surface and parallel to segment b, or of the arc passing through the centre of the reflecting surface which is perpendicular to it if this arc is the longer. U.K.

1.2.2. Where, owing to the size of the reflecting surface, it is impossible to obtain measurements in the directions defined in point 1.1.1.5 of Annex I, the technical services responsible for the tests may take measurements at the said point in two perpendicular directions as close as possible to those prescribed above. U.K.

2. Calculation of the radius of curvature ‘r’ U.K.

‘r’ expressed in mm is calculated from the formula:

• 

where:

r_p1

:

the radius of curvature at the first measuring point,

r_p2

:

the radius of curvature at the second measuring point,

r_p3

:

the radius of curvature at the third measuring point.

Figure 3: spherometer U.K.