Abstract: A device for developing an electrostatic latent image by applying magnetic toner is provided. The device includes a first transporting sleeve for transporting the magnetic toner along a first transporting path as carried thereon with the toner supplied from a hopper and a second transporting sleeve for transporting the toner along a second transporting path, which passes through a developing station where the latent image is developed, as carried thereon with the toner transferred from the first sleeve at least partly. There are also provided a first doctor blade for forming a first film of toner on the first sleeve and a second doctor blade for forming a second film of toner on the second sleeve.

Abstract: A rotary encoder for producing a pair of pulse trains with a desired phase difference therebetween is provided. The encoder comprises a rotary plate provided with a plurality of slits arranged in the form of a ring and a stationary slit plate provided with two sets of slits spaced apart at a particular distance. In accordance with the present invention, a single light source and a pair of light-receiving elements are provided, and the rotary and stationary slit plates are provided such that their distance may be appropriately adjusted. With such a structure, a phase difference between the two signals obtained by the light-receiving elements may be precisely adjusted to an intended value.