| 摘要 |
<p>A pair of threshold-operated, normally non-conductive cascaded thyristors are connected in shunt with a flash tube for rapidly interrupting the output of the tube when a predetermined quantity of light energy has been emitted therefrom. A photosensitive film is exposed to a portion of the light energy emitted from the flash tube and yields an optical density characteristic which is proportional to the predetermined quantity of the light energy except when the exposure time is extremely short. This deviation from proportionality for short exposure times is compensated by coupling a suitably valued resistor in the transconductive path of each of the thyristors to delay the extinction of the flash after interruption. The resistance value is chosen to provide sufficient residual flash exposure of the film to raise its optical density to a value more nearly proportional to the predetermined quantity of light.</p> |
