| Popis: |
The direction of a normal of a small plane surface, such as the ones of Vickers Diamond Pyramid, cannot be determined accurately by autocollimation, for the diffraction effect appears because of the apparent minuteness of the diameter of the collimator lens. Hence a new apparatus was designed.The apparatus is shown diagramatically in Fig. 1 and 2. The microscope is constructed by an objective Ob and an occular Oc, and it also has a half silvered mirror H and a cross line graticule X. When the cross line is illuminated, its primary image is formed at Y. When a mirror is placed at the middle point between Y and the work point B of the microscope, its normal is parallel to the optical axis of the microscope, the secondary image of the cross line is formed at B, and then, the cross line is visible at the centre of the view field.When tne small mirror is tilted around S (Fig. 1) by an angle of θ, the cross line is displaced by the amount (y-b)mθ at the field stop A, and the displacement can be measured by a micrometer occular.The performance of the apparatus is studied by introducing the parameters of m (magnification of the objective) and n=x/y.And the following results are obtained;……1) The sensitivity of the measurement is calculated by eqs. 9 and 10, and the results of numerical calculation are shown in Fig. 3.2) The lower limit of the area of the small plane surface to be measured can be obtained by eq. 13, and the numerical results are shown in Table.3.3) The maximum angle of θ is calculated by eqs. 18, 19 and 20 and the numerical results are shown by full lines in Fig. 5, '6 and 7. |
