| 摘要 |
PURPOSE:To make it possible to measure a focal distance in an extermely easy manner, by measuring the beam radius or the beam radius and beam waist of a focusing optical element of which the focal distance design value is preliminarily known at once. CONSTITUTION:A cylindrical lens SL to be inspected is arranged on a support 22 and a stand 23 is moved to an X-direction to adjust the distance between the lens SL and a beam waist BW to a focal distance design value f0 while a solid photographing element 12 is moved to the X-direction on the stand 21 to make the distance between the lens SL and a light receiving region equal to f0. Thereafter, when measurement is performed while the lens SL is sent to a longitudinal direction by a drive motor 24, the measurement of a focal distance can be performed over the total length of the lens SL. That is, the size omega1 of the beam waist is set to a constant size to be brought to a known amount or measured at every focal distance measuring time and the beam size omega2(Z) of the laser beam is measured at the position spaced apart from a focusing optical element to be inspected over the distance f0 while operation is applied to omega1, omega2(Z) to obtain the measured value fM of the focal distance. |
