BS EN 167:2002 pdf download
BS EN 167:2002 pdf download.Personal eye-protection一 Optical test methods.
4.2.2 Simplified method
4.2.2.1 Apparatus
The test arrangement is shown in Figure 5.
NOTE The measurement prricle is identical to thai given in 4.2.1, but the diameter ol the measuring zone is smaller (approximately 2,5 mm) and the test arrangement is simplified.
The beam of the laser (L) is expanded using the two lenses L1 and 12 and Is directed towards the measuring point of the ocular (P). Ocular (P) is positioned in such a way that it can rotate around the axis of the beam.
The deviation of the beam is a function of the prismatic refractive power at the measuring point.
The annular or circular diaphragm, whichever is chosen, is at a distance of (400 ± 2) mm from the centre of the ocular.
The lens A then produces the image of the centre of the ocular on the photoreceptor S.
The part of the test arrangement, comprising the diaphragms, the lens and the receptor, Is designed to rotate about the vertical axis through the centre of the ocular.
The ocular and the detector part of the apparatus have to pivot in order to compensate for any prismatic refractive power of the ocular.
NOTE For oculars without corrective effect, It is not necessary, in most cases, for the ocular and the detector part to perot.
4.2.2.2 Procedure
4.22.2.1 Calibration of the apparatus
Set up the apparatus, the essential features ol which are shown In Figure 5. wIthout the ocular in place. Put the annular diaphragm BIR In place. Rotate the detector part of the apparatus (consisting of a photoreceptor S. a lens A and the annular diaphragm B) horizontally about P so as to align the light beam from the beam expander (consisting of a lens Li with a typical focal length ottO mm, a lens 12 with a typical focal length at 30 mm and a circular diaphragm B with a pinhole of sufficient size so as to provide a uniform beam) with the centre 01 the annular diaphragm B. Measure the flux ‘ falling onto the photoreceptor S, corresponng to the total diffused kght, Replace the annular diaphragm BR by the circular diaphragm Bt.
Measure the flux ‘P tailing onto the photoreceptor, corresponding to the total non-diffused light.
Oblain the reduced luminance factor for the apparatus, f , for the solid angle musing the following equation;
4 is the luminous flux without the ocular in the parallel beam and with the annular diaphragm BR in place;
L is the luminous flux without the ocular in the parallel beam and with circular diaphragm Bj in place;
to is the solid angle defined by the annular diaphragm BR.
4.2.2.2.2 Testing of the ocular
Place the ocular in the parallel beam at position P as shown in Figure 5. Repeat 4.2.2.2.1 with the ocular in place, and with the ocular rotated about the axis of the beam to a position such that the prismatic deviation by the ocular is horizontal.
Measurements ot transmittance of oculars shall be taken at the visual centre of the ocular. It the visual centre is not known then the geometric centre shall be used.
NOTE Visual cenfre Is as defined in EN 166 Measurements of transmittance of frames shal be taken at all parts of the frame through which raclation could directly pass to the eye when the frame Is mounted on the test head.
7 Determination of variations in luminous transmittance
7.1 Unmounted oculars covering one eye
Locate the visual centre of the ocular. It the visual centre is not known the geometric centre shall be used. Refer to this as the centre
NOTE Visual centre is as defined in EN 166
Determine a circular area around the centre with diameter d, calculated as follows:
a) for ocufars more than 50 mm in vertical depth. d. (40.0 ± 0.5) mm:
b) for ocutars less than 50 mm in vertical depth, d (verlical depth of ocular — 10) mm.
Scan this circular area with a 5 mm nominal diameter light beam whilst at the same time measunng the luminous transmittance.
NOTE No measurements are to be recorded in a marginal region 5mm wide around the periphery of the ocular. For oculars with bands or gradients of different luminous transmittance, the requirement for variations in luminous
transmittance applies in this circular area but perpendicularly 10 the gradient (see Figure 7).
Changes of luminous transmittance that are caused by thickness variations due to the design of the lens are permitted and are determined using the correction procedure detailed in 7.3.
