Abstract: A light measuring device wherein a correct measured value can be obtained even if incident light varies in time or a luminance or brightness of an object for measurement is insufficient. The device comprises a branched optical fiber of a random specification having therein three mutually independent light transmission paths for introducing light from a common input end to three output ends. The input end of the optical fiber is located at a slightly defocused position of an objective lens while the output ends are individually opposed to three light receiving elements having different spectral sensitivities. Three components of light are simultaneously converted into electric signals and then into digital values by circuit means each including a double integration analog to digital converter. When a luminance is insufficient at a light receiving element, the gain of the associated analog to digital converter can be adjusted so as to assure appropriate measurement of light.

Abstract: An analog to digital converting device which can convert analog input signals individually into digital values of accurately corresponding magnitudes even when there is some difference in the input signals. The device comprises an integrating circuit which includes an operational amplifier for receiving an analog signal, an integrating capacitor connected between an input terminal and an output terminal of the operational amplifier, and a reset switch connected in parallel to the integrating capacitor. The integrating circuit is controlled to first perform an integrating operation and then an inverse integrating operation. A comparator is connected to an output terminal of the integrating circuit. A diode or transistor is connected in parallel to the integrating capacitor for limiting an amount of charge to be accumulated in the integrating capacitor by an inverse integrating operation to below a predetermined value.