| 摘要 |
<p>A rotating or reciprocating shutter synchronized with the film drive of a cinematographic camera carries or incorporates a light-guiding body of transparent material interposed between the camera objective and its light gate during periods of film transport to direct incident light onto a photoelectric element. The light-guiding body has a flat front surface perpendicular to the optical axis and a generally dihedral internally reflecting rear surface whose faces converge forwardly at a ridge intersecting that axis. One of these rear faces reflects axially incident light rays transversely outwardly through a first lateral surface of the body onto the photoelectric element; the other rear face directs such light rays onto an internally reflecting second lateral surface from which the rays pass through the first lateral surface to the photoelectric element, the second lateral surface being inwardly concave to let slanting incident rays strike the front surface from within at less than the critical angle of the transparent material whereby these rays are internally reflected at that front surface toward the first lateral surface.</p> |
