| 摘要 |
PURPOSE:To measure density accurately, by arranging a polarization converter, which converts linearly polarized light into circularly polarized light or elliptically polarized light, which is approximate to the circularly polarized light, at an arbitrary place on a light path for a light from a laser to a picture film. CONSTITUTION:A light beam is emitted from a laser A and converted into circularly polarized light or elliptically polarized light, which is approximate to the circularly polarized light by a 1/4 wavelength plate C in a converging optical system B. The diameter of the beam is converted into a desired beam diameter by a beam diameter converter D. Then, the light is converged by a condenser lens G and inputted to the surface of a picture film L, which is held by rollers H-K. The light beam, which has passed the film L, is split into two light beams having a large quantity of light and a small quantity of light by a beam splitter N in a light receiving optical system M and outputted to a light quantity detector Q. One beam is converted into a voltage by a photoelectric converter P and a current to voltage converter R. The other beam is converted into a voltage by converter Q and S. The voltages are inputted to a voltmeter U in response to the selection of a switch T. The voltages are measured as the quantity of light, and the density of the beam scanning part is obtained based on the quantity of light. |
