Image forming apparatus having a high γ photoreceptor

Claim 1

An apparatus for forming an image, comprising: a photoreceptor including an imaging surface for forming an electrostatic latent image thereon in response to an exposure light beam; means for charging said imaging surface to a predetermined electric potential; said photoreceptor having a light decay characteristic, wherein: when an amount of exposure on an exposed point of said imaging surface is smaller than a given critical amount, an electric potential of the exposed point decays slightly; and when an amount of exposure on the exposed point is larger than said given critical amount, the electric potential of the exposed point decays sharply; image writing means, including a laser beam generator and a generator drive circuit, for scanning and exposing said imaging surface with a laser beam to write said electrostatic latent image on said imaging surface; said generator drive circuit including a signal generator for generating a reference wave signal that has a frequency and an amplitude, and comparator means for comparing a level of an image density signal and a level of said reference wave signal, said comparator means including modulator means, responsive to the compared levels of said image density signal and said reference wave signal, for modulating said image density signal; said laser beam generator being driven in accordance with said modulated image density signal so that when said level of said image density signal is lower than said level of said reference wave signal, said laser beam generator emits a laser beam; and said signal generator setting an amplitude of said reference wave signal such that a maximum level of said image density signal, corresponding to a white image, is lower than a maximum level of said reference wave signal so that when an image is said white image, said laser beam generator emits a laser beam that has an initial amount of exposure light that is lower than said given critical amount to thereby prevent a latent image from being formed on said imaging surface.

Claim 2

An apparatus for forming an image, comprising: a photoreceptor including an imaging surface for forming an electrostatic latent image thereon in response to an exposure light beam; means for charging said imaging surface to a predetermined electric potential; said photoreceptor having a light decay characteristic, wherein: when an amount of exposure on an exposed point of said imaging surface is smaller than a given critical amount, an electric potential of the exposed point decays slightly; and when an amount of exposure on the exposed point is larger than said given critical amount, the electric potential of the exposed point decays sharply; image writing means, including a laser beam generator and a generator drive circuit, for scanning and exposing said imaging surface with a laser beam to write said electrostatic latent image on said imaging surface; said generator drive circuit including a signal generator for generating a reference wave signal that has a frequency and an amplitude, and comparator means for comparing a level of an image density signal and a level of said reference wave signal, said comparator means including modulator means, responsive to the compared levels of said image density signal and said reference wave signal, for modulating said image density signal; said laser beam generator being driven in accordance with said modulated image density signal so that when said level of said image density signal is lower than said level of said reference wave signal, said laser beam generator emits a laser beam; and said signal generator setting an amplitude of said reference wave signal such that a maximum level of said image density signal, corresponding to a white image, is lower than a maximum level of said reference wave signal so that when an image is said white image, said laser beam generator emits a laser beam that has an initial amount of exposure light that is lower than said given critical amount to thereby prevent a latent image from being formed on said imaging surface.

Claim 5

An apparatus for forming an image, comprising: a photoreceptor including an imaging surface for forming an electric latent image thereon in response to an exposure light; means for charging said imaging surface to a predetermined electric potential; said photoreceptor having a light decay characteristic, wherein: when an amount of exposure on a point of said imaging surface is smaller than a given critical amount, an electric potential of the exposed point decays slightly; and when an amount of exposure on the exposed point is larger than said given critical amount, the electric potential of the exposed point decays sharply; exposure means for uniformly exposing said imaging surface with a light amount that is lower than said given critical amount, after the imaging surface has been charged to said predetermined electric potential; and image writing means, including a laser beam generator and a generator drive circuit, for scanning and exposing said imaging surface with a laser beam to write said electric latent image on said imaging surface.

Claim 6

An apparatus for forming an image, comprising: a photoreceptor including an imaging surface for forming an electric latent image thereon in response to an exposure light; means for charging said imaging surface to a predetermined electric potential; said photoreceptor having a light decay characteristic, wherein: when an amount of exposure on a point of said imaging surface is smaller than a given critical amount, an electric potential of the exposed point decays slightly; and when an amount of exposure on the exposed point is larger than said given critical amount, the electric potential of the exposed point decays sharply; exposure means for uniformly exposing said imaging surface with a light amount that is lower than said given critical amount, after the imaging surface has been charged to said predetermined electric potential; and image writing means, including a laser beam generator and a generator drive circuit, for scanning and exposing said imaging surface with a laser beam to write said electric latent image on said imaging surface.