Image density control by sensing reference density patterns at multiple points

Claim 1

An image density control for use in an image forming apparatus for controlling a density of a toner image of an electrostatic latent image which is formed on an image carrier and representative of a document image, comprising: at least a first and second reference density patterns each having a different reference density; potential sensing means for sensing potentials of electrophotographic latent images of said first and second reference density patterns which are formed on the image carrier at multiple points along said patterns and for producing signals indicative of said potentials wherein at least one of said signals is indicative of a computed average of the sensed potentials of one of said reference patterns; means for varying various conditions by comparing sensed potentials of the reference density patterns with reference potentials each being assigned to respective one of the reference density patterns; and potential setting means for setting, in response to the potentials sensed by said potential sensing means, each of the reference potentials of the latent images of said first and second reference density patterns at a predetermined target value.