Apparatus and method for measurement of the ratio of toner particle electrostatic charge to toner particle mass in electrostatographic devices

In an improved electrostatographic image processing system having a charge storage medium, charging means for placing an electrostatic charge on a surface of said charge storage medium, means for producing a latent electrostatic image on said surface, and a development material for developing said latent electrostatic image on said surface to provide a developed image, said development material including at least a toner component and a carrier component, wherein properties of said developed image are determined by a ratio of electrostatic charge to mass of said toner component, wherein the improvement comprises:

• means for producing a control signal reflecting said ratio of electrostatic charge to mass of said toner component;
• and
• means for controlling the proportion of said toner component in said development material in response to said control signal, said control signal producing means including first apparatus for providing a first signal related to a difference in electrostatic potential of said surface resulting from addition of said toner component to said surface, second apparatus for providing a second signal related to a difference in optical reflectance of said surface resulting from addition of said toner component to said surface, and
• means for combining said first and said second signals to produce said control signal.

Apparatus for controlling the ratio of electrostatic charge to mass for a toner component in a development material utilized in developing an electrostatic latent image on a surface, comprising:

• means for generating a first signal related to a change in the electrostatic charge of said surface resulting from addition of said toner component to said surface;
• second means for generating a second signal related to a change in optical reflectances from said surface resulting from addition of said toner component to said surface whereby to produce a signal reflecting said toner component mass;
• means for combining said first and second second signals to generate a control signal related to the ratio of said change in electrostatic charge to said toner component mass;
• and
• means for controlling the proportion of said toner component in said image developing in response to said control signal.

A method for controlling the concentration of toner particles in a development material for developing latent electrostatic images stored on a surface, the surface having been previously charged to a predetermined electrostatic potential and then exposed to form said latent electrostatic images thereon, said surface having a preset optical relectance, comprising the steps of:

• a. measuring the change in electrostatic potential of said surface resulting from addition of toner particles to said surface to produce a potential measurement;
• b. measuring the change in optical reflectance of said surface resulting from addition of said toner particles to said surface to produce a reflectance measurement;
• c. combining said potential measurement and said reflectance measurement to provide a control signal reflecting the ratio of electrostatic charge to mass of said toner particles;
• and
• d. determining the concentration of said toner particles in said development material from said combined measurements.

In an electrostatographic image processing system of the type wherein a latent electrostatic image is generated on a charge bearing surface and thereafter developed by developing material, said developing material including a toner component and at least one other component, and apparatus for maintaining an electrostatic charge to mass ratio of said toner component within predetermined limits comprising:

• means for providing a signal indicative of said electrostatic charge to mass ratio of said toner component;
• means for comparing said signal to said predetermined limits;
• and
• means for changing the concentration of said toner component in said developing material in response to a change of said charge to mass ratio of said toner component, said signal providing means including means for providing a first signal related to the change in electrostatic potential of said charge bearing surface upon addition of said developing material toner component to said surface, and means for providing a second signal related to the change in optical reflectance from said surface upon addition of said developing material toner component to said surface, said signal providing means including means for combining said first and said second signals to produce said signal indicative of said electrostatic charge to mass ratio of said toner component.

In an electrostatographic image processing system, the steps comprising:

• a. charging a surface of a medium utilized for storing electrostatic images,
• b. measuring a first electrostatic potential of said charged surface;
• c. measuring a first optical reflectance from said surface;
• d. applying charged toner particles to said charged surface;
• e. measuring a second electrostatic potential for said surface with said charged toner particles;
• f. determining a difference between said first and said second electrostatic potential to provide a potential difference;
• g. measuring a second optical reflectance from said surface with said charged toner particles;
• h. determining a difference between said first and second optical reflectance to provide an optical reflectance difference;
• and
• i. dividing said potential difference by said optical reflectance difference whereby to provide a ratio of electrostatic charge to mass of the toner component in said developing material.