Slice level deciding circuit

摘要

A slice level deciding circuit includes a slice level generator for generating a variable slice level and a comparator for comparing a slice level generated from the generator with a picture image signal. An optimum slice level can be provided by operating, via an arithmetic circuit, a prescribed value on the same slice level as generated from the generator when an output from the comparator satisfies a prescribed slice level deciding condition. Accordingly, deterioration of a picture image quality can be prevented, which is caused by changes of a quantity of light due to variations of ambient temperature around the light source used for obtaining a picture image signal from the readout medium and noise produced upon reading portions on the readout medium where a quantity of light from the light source is reduced.