Abstract: An A/D converting device comprises; a plurality of A/D converters connected in parallel with each other, for carrying out a converting operation a plurality of numbers of times, in which an analog signal is converted into a digital data, a selecting circuit for selecting each A/D converter from the plurality of A/D converters at each sampling timing during the converting operation to sample the converted digital data, a selecting circuit controlling unit for controlling the selecting circuit so that when one A/D converter is selected at one sampling timing during the Nth converting operation, another A/D converter is selected at the one sampling timing during the (N+1)th converting operation, an adding circuit for integrating the digital data sampled at the one sampling timing during each converting operation, and a processing unit for processing the integrated digital data.

Abstract: An offset correction circuit containing an integrator is provided between an output of a first DC amplifier and an input of a second DC amplifier, and the integrator corrects not only an offset error caused by an input signal in the first DC amplifier, but also an offset error caused by an input signal in the second DC amplifier. Thus, the effect of the offset error proportional to the integral value of the input signal strength, occurring depending on the temperature stability or power supply voltage variation rate resulting from the input signal in the two DC amplifiers can be canceled.

Abstract: The purpose of the invention is to offer an optical-frequency-stabilized light source with high accuracy and stability of the optical frequency. An optical splitter 8 splits output light from a local light source 7 into two beams. An optical detector 2 detects beat signals formed by the superimposition of the optical frequency difference between the local light source 7 and the output light, and a rectifier 3 rectifies the beat signal. A time measuring circuit 4 measures the time at which the beat signal was obtained. A frequency measuring circuit 5 measures the beat frequency. A CPU 6 outputs the deviation between the output light from the local light source 7 and the target optical frequency. A Fabry-Perot etalon transmission detection circuit 11 outputs an electrical signal corresponding to the optical frequency of the output light from an optical splitter 9.

Abstract: An optical frequency sweep signal generator using an optical frequency variable bandpass filter which can be practically used is provided.