Exposure control device and method

Claim 1

A control system for varying the exposure of an original in an electrostatic image forming system, comprising: a light source responsive to voltage input; means for positioning an original document for exposure by the light source; means for applying an initial predetermined voltage to the light source; means for developing an electrostatic image of the original including a photosensitive member that received the image; a reference pattern that is positioned for exposure by the light source and development by the photosensitive member; means for sampling the image density of the reference pattern; means for sampling the image density of the image of the reference pattern developed on the photosensitive member including a sensor; memory means for storing a predetermined table of values corresponding to a relationship between the density of the reproduced reference pattern and the sensor; means for defining a relationship between the light source voltage and the density of the reproduced reference pattern as modified by the value in the memory means; comparator means for comparing the measured image density with a predetermined image density to produce a correction signal, and means for providing a fixed increment adjustment of the relationship between the light source voltage and the density of the reproduced reference pattern in response to the correction signal, whereby a light surface voltage is determined for an exposure operation from the density of the reproduced reference pattern.

Claim 6

A method of controlling a voltage to be supplied to a lamp which can illuminate an original in a copying machine, wherein an electrostatic latent image is formed by projecting an original image on a photosensitive member and then the electrostatic latent image is transferred onto a transfer paper after making it into a visible image by development, the copy machine is provided with an original density detecting means for detecting the original density, a standard pattern disposed at a position where it can be illuminated by the lamp which illuminates the original and a visible image density of the standard pattern, comprising the steps of: (a) forming a visible image by developing a latent image obtained by exposing the standard pattern with the lamp to which an optional lamp voltage (V L ) is supplied; (b) obtaining the visible image density (ID) by the visible image density (ID) based on a first predetermined characteristic data which shows a relationship between the lamp voltage for the standard pattern and an image density; (d) obtaining a voltage difference (V L -g(ID)) between the lamp voltage (V L ), when the visible image is formed, and the lamp voltage (g(ID)) obtained by the characteristic data; (e) obtaining a lamp voltage (f(OD)) for the original density obtained by the original density detecting means based on a second predetermined characteristic data which shows a relationship between the original detected and the lamp voltage to be supplied to the lamp corresponding to its density, and (f) determining a voltage (f(OD)+V L -g(ID)) as the voltage to be supplied to the lamp for illuminating the original, wherein the voltage difference (V L -g(ID)) is added to the lamp voltage (f(OD)).

Claim 7

A method of controlling a voltage to be supplied to a lamp which can illuminate an original in a copying machine, wherein an electrostatic latent image is formed by projecting an original image on a photosensitive member and then the electrostatic latent image is transferred onto a transfer paper after making it into a visible image by development, the copy machine is provided with an original density detecting means for detecting the original density, a standard pattern disposed at a position where it can be illuminated by the lamp which illuminates the original and a visible image density of the standard pattern, comprising the steps of: (a) forming a visible image by developing a latent image obtained by exposing the standard pattern with the lamp to which an optional lamp voltage (V L ) is supplied; (b) obtaining the visible image density (ID) by the visible image density (ID) based on a first predetermined characteristic data which shows a relationship between the lamp voltage for the standard pattern and an image density; (d) obtaining a voltage difference (V L -g(ID)) between the lamp voltage (V L ), when the visible image is formed, and the lamp voltage (g(ID)) obtained by the characteristic data; (e) obtaining a lamp voltage (f(OD)) for the original density obtained by the original density detecting means based on a second predetermined characteristic data which shows a relationship between the original detected and the lamp voltage to be supplied to the lamp corresponding to its density, and (f) determining a voltage (f(OD)+V L -g(ID)) as the voltage to be supplied to the lamp for illuminating the original, wherein the voltage difference (V L -g(ID)) is added to the lamp voltage (f(OD)).