BS EN ISO 8980-3:2013 pdf free

BS EN ISO 8980-3:2013 pdf free.Ophthalmic optics – Uncut finished spectacle lenses
The polarizing efficiency of a polarizing lens is determined with radiation polarized parallel and perpendicular to the plane of transmission. Before measuring the sample the incident beam should be essentially 100 % linearly polarized by the introduction of a suitable polarizing medium and calibrating to 100 %. The spectacle lens or the linear polarizer is rotated to the point of maximum transmittance. At this orientation, the luminous transmittance, Tp,max, is recorded. The spectacle lens or linear polarizer is then rotated 90° and the luminous transmittance, Tp,min, is recorded. The polarizing efficiency shall then be calculated according to 3.6.
For the measurements, a spectrophotometer shall be used in combination with a polarizing medium of known plane of polarization in the light path. The spectral transmittance shall be determined in accordance with 7.2 and 7.3.
Select a combination of source oflight and filter to give a correlated colour temperature of(6 500± 1 000) K (approximating CIE Standard lluminant D65 in the visible region). Select a detector with approximately the spectral sensitivity of the CIE 2° Standard Observer (ISO 11664-1) and a visible spectral range that is linear to within±0,5 %. Collimate the beam of light from the source and insert the linear polarizer and the spectacle lens under test between the collimator and detector.
A pair of polarizers are cut to give planes of transmission at a +3° and a – 3° angle about the horizontal.The top and bottom halves of the polarizers shall be then joined together and glass mounted, with the line of the join horizontal to form a split field polarizer. The split-field polarizer shall be capable of being rotated by means of a lever carrying a corresponding pointer. The pointer transverses a scale calibrated in degrees left or right of zero. The split fields shall be illuminated from behind by a diffused light source. Make sure that the top and bottom register bars are long enough to fix a complete spectacle frame parallel to the horizontal axis for measurements of mounted lenses.
Mount the lens on the apparatus between the two register bars with the indicating marks aligned along 180° and with its front surface towards the split-field polarizer. Ensure that the split-field appears in the centre of the lens by means of vertical adjusters.
Move the lever from side to side until the top and bottom halves of the iluminated split-field appear of equal luminance when viewed through the lens.
Read off the pointer position to give the deviation in degrees (plus or minus) of the plane of transmission of the lens from the vertical.BS EN ISO 8980-3 pdf download.