2.1. Not more than one ‘cut-off’ shall be visible(1).
2.2. Sharpness of ‘cut-off’
The sharpness factor G is determined by scanning vertically through the horizontal part of the ‘cut-off’ at 2,5° from the V-V where:
[Bild bitte in Originalquelle ansehen] where β = the vertical position in degrees.
The value of G shall not be less than 0,13 (minimum sharpness) and not greater than 0,40 (maximum sharpness).
2.3. Linearity
The part of the horizontal ‘cut-off’ that serves for vertical adjustment shall be horizontal between 1,5° and 3,5° from the V-V line (see Figure 1).
The inflection points of the ‘cut-off’ gradient at the vertical lines at 1,5°, 2,5° and 3,5° shall be determined by the equation:
[Bild bitte in Originalquelle ansehen].
The maximum vertical distance between the inflection points determined shall not exceed 0,2°.
3. Vertical and horizontal adjustment
If the ‘cut-off’ complies with the quality requirements of paragraph 2 of this annex, the beam adjustment may be performed instrumentally.
Figure 1
Measurement of ‘cut-off’ quality
[Bild bitte in Originalquelle ansehen]
Note
: The scales are different for vertical and horizontal lines.
3.1. Vertical adjustment
Moving upward from below the line B (see Figure 2 below), a vertical scan is carried out through the horizontal part of the ‘cut-off’ at 2,5° from V-V. The inflection point (where d
2
(log E)/dv
2
= 0) is determined and positioned on the line B situated one per cent below H-H.
3.2. Horizontal adjustment
The applicant shall specify one of the following horizontal aim methods:
(a) The ‘0,2 D line’ method (see Figure 2 below).
A single horizontal line at 0,2° D shall be scanned from 5° left to 5° right after the lamp has been aimed vertically. The maximum gradient ‘G’ determined using the formula [Bild bitte in Originalquelle ansehen] where β is the horizontal position in degrees, shall not be less than 0,08.
The inflection point found on the 0,2 D line shall be positioned on the line A.
Figure 2
Instrumental vertical and horizontal adjustment — horizontal line scan method
[Bild bitte in Originalquelle ansehen]
Note
: The scales are different for vertical and horizontal lines.
(b) The ‘3 line’ method (see Figure 3)
Three vertical lines shall be scanned from 2° D to 2° U at 1°R, 2°R, and 3°R after the lamp has been aimed vertically. The respective maximum gradients ‘G’ determined using the formula:
[Bild bitte in Originalquelle ansehen]
where β is the vertical position in degrees, shall not be less than 0,08. The inflection points found on the three lines shall be used to derive a straight line. The intersection of this line and the line B found while performing vertical aim shall be placed on the V line.
Figure 3
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