Testing image density to control toner concentration and dynamic range in a digital copier
First Claim
1. In an image forming system comprising charging means for uniformly charging a surface of a photoconductive element to a predetermined potential, and exposing means for exposing said surface of said photoconductive element to a light image to electrostatically form a latent image on said surface, a developing system for developing said latent image to produce a toner image, comprising:
- sensor pattern forming means for forming two toner image patterns on the photoconductive element, each of said two toner image patterns having a different particular toner density on the photoconductive element;
a photosensor for sensing toner densities of toner deposited on said two toner image patterns; and
control means for determining a difference between the sensed toner densities of toner deposited on the two toner image patterns, for variably controlling an amount of toner to be supplied to a developer and for variably controlling a dynamic range of a latent image such that the toner density difference between said two toner image patterns is maintained at a predetermined difference value, wherein said dynamic range represents a difference between maximum and minimum values of a surface potential of said photoconductive element on which said latent images are formed.
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Abstract
A developing system of the type using a two-component developer and capable of reproducing image densities and halftone images stably with no regard to changes in ambient conditions and aging. At least two toner image patterns each having a different toner density are formed on a photoconductive element. The amounts of toner deposited on the individual patterns are sensed by a photosensor, while the supply of toner to a developer and the dynamic range of a latent image are controlled in combination in response to the output of the photosensor.
38 Citations
15 Claims
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1. In an image forming system comprising charging means for uniformly charging a surface of a photoconductive element to a predetermined potential, and exposing means for exposing said surface of said photoconductive element to a light image to electrostatically form a latent image on said surface, a developing system for developing said latent image to produce a toner image, comprising:
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sensor pattern forming means for forming two toner image patterns on the photoconductive element, each of said two toner image patterns having a different particular toner density on the photoconductive element; a photosensor for sensing toner densities of toner deposited on said two toner image patterns; and control means for determining a difference between the sensed toner densities of toner deposited on the two toner image patterns, for variably controlling an amount of toner to be supplied to a developer and for variably controlling a dynamic range of a latent image such that the toner density difference between said two toner image patterns is maintained at a predetermined difference value, wherein said dynamic range represents a difference between maximum and minimum values of a surface potential of said photoconductive element on which said latent images are formed. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A developing method for an image forming system comprising the steps of:
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(a) uniformly charging a surface of a photoconductive element to a predetermined potential; (b) exposing the surface of the photoconductive element to a light image to electrostatically form a latent image on the surface; (c) forming two toner image patterns on the surface of the photoconductive element, each of said two toner image patterns having a different particular toner density; (d) sensing toner densities of toner deposited on the two toner image patterns; (e) determining a difference between the sensed toner densities of toner deposited on the two toner image patterns and controlling an amount of toner to be supplied to a developer such that the sensed amount of toner coincides with a predetermined amount; and (f) variably controlling a dynamic range of a latent image such that the toner density difference between the two toner image patterns is maintained at a predetermined difference value, wherein said dynamic range represents a difference between maximum and minimum values of a surface potential of said photoconductive element on which said latent images are formed. - View Dependent Claims (11, 12, 13, 14, 15)
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Specification