The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 03, 1978
Filed:
Nov. 29, 1976
Takahiro Ohta, Asaka, JP;
Akira Muramatsu, Asaka, JP;
Fuji Photo Film Co., Ltd., Minami Ashigara, JP;
Abstract
The intensity of light penetrating an X-ray film being viewed is automatically maintained at a preset, adjustable, eye comfort level. A photosensor detects the average light level on the observer side, and its output controls the charging time of a capacitor coupled to the emitter of a unijunction transistor. When the capacitor reaches a predetermined voltage it fires the transistor and dumps its charge through a pulse generator which in turn triggers a gated semiconductor connected in series with the viewer light source. The period between successive firing cycles is proportional to the penetrating light level. Thus, if the light level increases, as when a relatively transparent film negative is inserted in the viewer or when a negative is removed, the capacitor charging time increases, the firing period increases, and the light source intensity therefore decreases to restore the preset level of light penetration.