ISO 11146-1 pdf download – Lasers and laser-related equipment —Test methods for laser beam widths, divergence angles and beam propagationratios — Part 1: Stigmatic and simple astigmatic beams

ISO 11146-1 pdf download – Lasers and laser-related equipment —Test methods for laser beam widths, divergence angles and beam propagationratios — Part 1: Stigmatic and simple astigmatic beams.
angle between the x-axis of the laboratory system and that of the principal axis of the power density distribution which is closer to the x-axis
NOTE From this definition it follows that —,r/4 < o < n-/4 for Ic’I  .‘r/4 ; if ç = ut 4, p is defined as the angle between the x-axis and the major principal axis (axis of maximum extent) of the power density distribution. 3.5 beam widths extent of a power density distribution in a cross section of the beam at an axial location z along that principal axis which is closer to the x- ocr-axis of the laboratory coordinate system, respectively, based on the centered second order moments of the power density distribution NOTE 1 If the principal axes make the angle ,t14 with the x- and y-axes of the laboratory coordinate system, then d is by convention the larger beam width. NOTE 2 This definition differs from that given in ISO 11145:2001, subclause 3.5.2. where the beam widths are defined only in the laboratory system, whereas for the purposes of this part of ISO 11146 the beam widths are defined in the principal axes system. 3.6 ellipticity of a power density distribution ratio between the minimum and maximum beam widths 3.7 circular power density distribution power density distribution having an ellipticity greater than 087 3.8 beam diameter extent of a circular power density distribuhon, based on the second order moments stigmatism property of a beam having circular power density distributions in any plane under free propagation and showing power density distributions after propagation through a cylindrical lens all having the same or azimuthal orientation as that lens 3.10 simple astigmatism property of a non-stigmatic beam whose azimuth angle shows a constant orientation under free propagation, and which retains its original orientation after passing through a cylindrical optical element whose cylindrical axis is parallel to one of the principal axes of the beam NOTE The principal axes of a power density distribution corresponding to a beam with simple astigmatism are called the pnncipal axes of that beam. general astigmatism property of a beam which is neither stigmatic nor simple astigmatic NOTE This part of ISO 11146 deals only with stigmatic and simple astigmatic beams. Refer to ISO 11146-2 for general astigmatic beams. It shall be confirmed, from manufacturers’ data or by measurement, that the output quantity of the detector system (e.g. the voltage) is linearly dependent on the input quantity (laser power), Any wavelength dependency, non-linearity or non-uniformity of the detector or the electronic device shall be minimized or corrected by use of a calibration procedure. When using a scanning device for determining the power density distribution, care shall be taken to ensure that the laser output is spatially and temporally stable during the whole scanning period. When measuring pulsed laser beams, the trigger time delay of sampling as well as the measuring time interval play an important role because the beam parameters may ctiange during the pulse. Therefore it is necessary to specify these parameters in the test report. 6.5 Beam-forming optics and optical attenuators If the beam cross-sectional area is greater than the detector area, a suitable optical system shall be used to reduce the beam cross-sectional area on the detector surface. The change in magnification shall be taken into account during the evaluation procedure. Optics shall be selected appropriate to wavelength. An attenuator may be required to reduce the laser power density on the surface of the detector. Optical attenuators shall be used when the laser output-power or power density exceeds the detectors working (linear) range or the damage threshold. Any wavelength, polarization and angular dependency, nonlinearity or non-uniformity, including thermal effects of the optical attenuator, shall be minimized or corrected by use of a calibration procedure. None of the optical elements used shall significantly influence the relative power density distnbution. 6.6 Focusing system The focusing system shall conform to the requirements relating to the beam-forming optics given in 6.5. The total uncertainty contributed by the focusing system shall be less than 1 % of the beam width.