Image density control apparatus

Claim 3

An apparatus as recited in claim 1, wherein said sensing and biasing means includes; a probe positioned adjacent to the photoconductive surface and arranged to detect the potential of the sample electrostatic latent image recorded thereon prior to toner particles being deposited on the photoconductive surface; a voltage source for electrically biasing said toner particle depositing means; and means, in electrical communication with said probe and said voltage source, for generating an electrical output signal indicative of the sample electrostatic latent image potential detected by said probe to regulate the output voltage of said voltage source.

Claim 4

An apparatus as recited in claim 2, wherein successive distinguishable single color electrostatic latent images are recorded on the charged photoconductive surface, including an indexable support member having a plurality of discrete neutral density samples disposed thereon, said support member being mounted in a light-receiving relationship with said illuminating means, each of said neutral density samples having a pre-selected density substantially about the cut-off density of the respective single color electrostatic latent image corresponding thereto.

Claim 5

An apparatus as recited in claim 3, wherein the neutral density samples disposed on said support member include: a first neutral density sample for a green electrostatic latent image; a second neutral density sample spaced from said first neutral density sample for a blue electrostatic latent image; and a third neutral density sample spaced from said first and second neutral density samples for a red electrostatic latent image.

Claim 6

An apparatus as recited in claim 2, wherein said electrical signal generating means includes: means for periodically sampling the sample electrostatic latent image potential detected by said probe; and circuit means for analyzing the periodically detected sample electrostatic latent image potential and forming a continuous electrical output signal indicative thereof.

Claim 7

An electrophotographic printing machine of the type having a photoconductive surface, including: means for charging the photoconductive surface to a substantially uniform potential; at least one neutral density sample having a preselected density corresponding to substantially about the predetermined cut-off density of the single color electrostatic latent image; means for exposing the charged photoconductive surface to a single color light image of an original document to record thereon a single color electrostatic latent image, said exposing means being arranged to illuminate said neutral density sample and project a light image thereof onto the charged photoconductive surface to record thereon a sample electrostatic latent image having a potential intermediate the single color electrostatic latent image and the non-image regions of the charged photoconductive surface; means for depositing toner particles, complementary in color to the single color electrostatic latent image, on the charged photoconductive surface; and means for sensing the potential of the sample electrostatic latent image recorded on the charged photoconductive surface and electrically biasing said toner particle depositing means to a potential corresponding to the sample electrostatic latent image potential so that toner particles are deposited on regions of the photoconductive surface having a potential substantially greater than the potential of the sample electrostatic latent image.

Claim 8

An electrophotographic printing machine of the type having a photoconductive surface, including: means for charging the photoconductive surface to a substantially uniform potential; at least one neutral density sample having a preselected density corresponding to substantially about the predetermined cut-off density of the single color electrostatic latent image; means for exposing the charged photoconductive surface to a single color light image of an original document to record thereon a single color electrostatic latent image, said exposing means being arranged to illuminate said neutral density sample and project a light image thereof onto the charged photoconductive surface to record thereon a sample electrostatic latent image having a potential intermediate the single color electrostatic latent image and the non-image regions of the charged photoconductive surface; means for depositing toner particles, complementary in color to the single color electrostatic latent image, on the charged photoconductive surface; and means for sensing the potential of the sample electrostatic latent image recorded on the charged photoconductive surface and electrically biasing said toner particle depositing means to a potential corresponding to the sample electrostatic latent image potential so that toner particles are deposited on regions of the photoconductive surface having a potential substantially greater than the potential of the sample electrostatic latent image.

Claim 9

A printing machine as recited in claim 6, wherein said sensing and biasing means includes: a probe positioned adjacent to the photoconductive surface and arranged to detect the potential of the sample electrostatic latent image recOrded thereon prior to toner particles being deposited on the photoconductive surface; a voltage source for electrically biasing said toner particle depositing means; and means, in electrical communication with said probe and said voltage source, for generating an electrical output signal indicative of the sample electrostatic latent image potential detected by said probe to regulate the output voltage of said voltage source.

Claim 10

A printing machine as recited in claim 7, wherein successive distinguishable single color electrostatic latent images are recorded on the charged photoconductive surface, including an indexable support member having a plurality of discrete neutral density samples disposed thereon, said support member being mounted on the printing machine in a light-receiving relationship with said exposing means, each of said neutral density samples having a pre-selected density substantially about the cut-off density of the respective single color electrostatic latent image corresponding thereto.

Claim 11

A printing machine as recited in claim 8, wherein the neutral density samples disposed on said support member include: a first neutral density sample for a green electrostatic latent image; a second neutral density sample spaced from said first neutral density sample for a blue electrostatic latent image; a third neutral density sample spaced from said first and second neutral density samples for a red electrostatic latent image.

Claim 12

A printing machine as recited in claim 7, wherein said electrical signal generating means includes means for periodically sampling the sample electrostatic image potential detected by said probe; and circuit means for analyzing the periodically detected sample electrostatic latent image potential and forming a continuous electrically output signal indicative thereof.