Patent ID: 8587774

Claim:
An image forming apparatus, comprising: an image forming unit having a moving member; and a velocity detecting device that detects velocity and velocity fluctuation of the moving member, wherein the velocity detecting device includes: an image-pattern acquiring unit that includes a laser light source and an area sensor that acquires a one-dimensional or a two-dimensional image, provides a lens between the moving member and the area sensor, irradiates a beam emitted from the laser light source to the moving member to make a scattering light of the moving member scattered from the moving member, and acquires an image pattern on the area sensor derived from the scattering light by using the lens at a predetermined time interval in association with movement of the moving member; and a velocity calculating unit that calculates velocity of the moving member by computing a plurality of the image patterns acquired by the image-pattern acquiring unit, wherein the lens is a reduced optical system that projects a reduced object onto the area sensor.