The most essential condition is small divergence (less than 0,1 mrad) of laser beam. S
is an unknown function and it can be represented by, for example as a polynomial. It results from (1) that in order to get more than one of hole edge function parameters, at least one of input parameters (p 1,???., pn) has to be variable. The simplest way to change one of the parameters pi is to move the beam. The principle of new method is to rotate the beam around particular axis so that, the beam can be considered as scanning in polar co-ordinates. It fits very well to the objects of radial symmetry ( the beam path has also the radial symmetry). As the result the function radiation efficiency vs. angle of rotation is obtained, after that function Sh and its parameters (ri) can be calculated using numerical methods. The problem discussed in this paper concerns ambiguity caused by uncertainty of the position of hole and beam rotation axis. It can be solved by expansion the Q function to Fourier series and than examination the first to zeroth harmonic ratio. It is obvious that displacement between axes causes the increase of first harmonic, unfortunately it results in the decrease counter 7, additional density filter 8, reference photon counter 9, PC computer
to transform circular beam to elliptical and its rotation makes the laser beam rotation. Two crossed polarizers are used to adjust the beam intensity. is measured by photon counter 9; the density filter 8 is used to decrease it was mentioned above, theoretically the incident beam should rotate around its optical axis and around the hole axis. However unavoidable uncertainties more complex. The path has been determined by CCD camera, and applied to calculation of hole real dimensions (Sh). Beam axis moves with very small apex angle, (less than 1 mrad) and so this error component was not taken under consideration. The beam dimensions was determined by the moving edge method as 100 x 160 m.
Fig. 3a shows the measurement results of hole shown on Fig. 3b. The hole nominal diameter is 80 ??m and the length (material thickness) is 3,5 mm. The hole position is located at the minimum first to zeroth Fourier ratio (?i??1??m point ???0,0???on the graph in Fig. 5). Fig. 4 shows the light efficiency (Q( )) measurement results after shifting the hole of 20 and 40 ??m, from initial position (???0,0??? point), comparing to the results for initial position. One can see that the line representing measurement results after 20 and 40 ?i?? ??m shift differs comparing to line obtained in the point ???0,0??? (with minimum first to zeroth harmonic ratio). This difference will create the measurement measurement results in this point (Fig. 3a) the best fits the
hole shape shown on microscopic image (Fig. 3b). However small (-5 ??m) systematic error has been observed.