BS EN 167-2002 pdf download.Personal eye-protection Optical test methods.
This BS EN 167 specifies optical test methods for eye-protectors, the requirements for which are contained
in other ENs.
Alternative methods may be used if shown to be equivalent.
Non-optical lest methods are given in EN 168.
Specilicalions are given in EN 166.
A definition of terms is given In EN 165.
2 Normative references
This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text, and the publications are listed liereatter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in It by amendment or revision. For undated references the latest edition of the publication referred to applies (including amendments).
EN 165, Personal eye-protection — Vocabuiwy.
EN 166, Personal eye-protection — Specifications.
EN 168, Personal eye-protection — Non-optical test methods.
3 Test for phericaI, astigmatic and prismatic refractive powers
NOTE The reference methods for assessment of refractive power are contained in 3.1 and 3.2.
If dunng measurement using the telescope a doubling or other aberration of the image is observed then the ocular
may either be cIassfied as a defective, or subjected to further examination using the method described in annex A.
3.1 Testing unmounted oculars covering one eye
3.1.1 Apparatus
3.1.1.1 Telescope
A telesco with an aperture of nominally 20 mm and a magnification between 10 and 30, fitted with an adjustable oyepi3co incorporating a reticule.
3.1.1.3 Filter
A filter with its maximum transmittance in the green part of the spectrum may be used to reduce Chromatic aberrations.
3.1.1.4 Calibration tenses
Lenses with positive and negative spherical relrachve powers of 0.06 m1, 0,12 m1 and 0,25 m1
(tolerance ± 0,01 m1).
3.1.2 Arrangement and calibration of apparatus
The telescope and illuminated target are placed on the same optical acis (4,60 ± 0,02) m apart.
The observer focuses the reticule and the target and aligns the telescope to obtain a clear Image of the pattern. This selling is regarded as the zero point of the focusing scale of the telescope. The telescope shall be aligned so that the central aperture of the target is imaged on the centre of the cross-line graticule. This setting is regarded as the zero point of the prism scale.
The focusing adjustment of the telescope is calibrated with the calibration lenses (3.1.1.4) so that a power of 0.01 m1 may be measured. Any other equivalent calibration method may be used.
3.1.3 Procedure
Position the ocular in front of the telescope in the as-worn position, or other position as specified by the manufacturer, If the as-worn position is unknown, or if no position is specified by the manufacturer then the ocular shall be positioned normal to the telescopic axis and the tests conducted at the geometric centre.
3.1.3.1 Spherical refractive power and astigmatic refractive power
3.1.3.1.1 Oculars without astigmatic refractive power
The telescope is adjusted until the image of the target is clearly focussed. The spherical power of the ocular is then
read from the scale of the telescope.
3.1.3.1.2 Oculars with astigmatic refractive power
The target, or the ocular, is ro1atcl in o:cicr to align the principal nie dians & the ocular with the bars of the target The telescope is focused firstly on one set of bars (measurement D) and then on the perpendicular bars.
4.2.1 Basic method
4.2.1.1 Apparatus
The arrangement is shown in Figure 4.
The spherical concave mirror H1 forms an image of light I of identical dimensions at diaphragm LB. The spherical concave mirror H3 forms an image of diaphragm LB in the plane of diaphragms BL and BR. The achromatic lens A is positioned immediately behind the diaphragm so that a reduced image of the test sample in position P appears on diffusing screen MS. The image of iris diaphragm lB1 is formed at the same time as lB2
The arrangement collects all the light originating from the filter between angles a = 1,5° and a + ta = 20 in relation to the optical axis.
4.2.1.2 Procedure
The ocular is placed in the parallel beam at position P. then diaphragm B1 is put in place. The flux 1L falling onto the photodetector corresponds to the undiffused light transmitted by the sample. Diaphragm 81 Is then replaced by annular diaphragm B: flux ø falling onto the photodetector corresponds to the total diffused light originating from the filter and from the apparatus. The test sample is then placed at position P. The flux 4 which then falls onto the photodetector corresponds to the diffused light coming from the apparatus only.
The difference ø – corresponds to the light diffused by the filter. The mean reduced luminance factor 1 for the solid angle w is calculated from the preceding fluxes by means of the formula:BS EN 167-2002 pdf download.