| 摘要 |
PURPOSE:To obtain stable temperature characteristics by determining the operation pattern of plural weighted current sources which operate associatively with an expansion current and obtaining an integration current matching with opening characteristics of a shutter blade which vary with time. CONSTITUTION:The operation pattern of the plural current sources whose current values are weighted corresponding to the temperature-compensated expansion current is determined corresponding to the elapse of an exposure time to make integration characteristics follow up opening characteristics of the shutter blade. Consequently, the need to correct a gamma value (ratio of variation quantity of photocurrent and variation quantity of field brightness) by adjusting a bias stage is eliminated, and the integration current does not contain any parameter which is proportional to absolute temperature, so stable temperature characteristics are obtained. Further, a current weighted relatively to a film speed is compressed by a diode 11 and superposed upon the level obtained by compressing the photocurrent by the diode 11 as well, thereby removing a parameter which is proportional to the absolute temperature even from a component corresponding to the film speed as to the integration current to a capacitor 22.
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