| 摘要 |
Apparatus for the determination of light transmissivity of film frames preparatory to the making of prints in a copying machine has a plate-like locating device for successive film frames, a light source at one side of the locating device, a group of photosensitive signal-generating elements at the other side of the locating device, and a diaphragm which is interposed between the locating device and photosensitive elements and has a hollow truncated pyramid, plate-like partitions and tubular components which confine light passing through the film frame on the locating device in such a way that a centrally located photosensitive element receives light from the entire film frame and all of the light which has passed through the central field of the frame, whereas each of the other photosensitive elements receives only that light which has passed through a single one of four L-shaped peripheral fields surrounding the central field of the frame. Light which reaches the centrally located element passes through the pyramid as well as around the pyramid. On the other hand, light which reaches the other photosensitive elements passes from the corresponding peripheral fields and thereupon through the tubular components of the diaphragm. Consequently, the signal which is transmitted by the centrally located element is indicative of transmissivity of the entire frame, and the signals transmitted by the other elements are indicative solely of transmissivity of the respective peripheral frames.
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