Abstract: An image forming apparatus for forming images on both surfaces of a recording sheet. It is discriminated from image signals obtained by scanning a first surface and a second surface of an original which surface has more or less toner consumption, and the image formation sequence is controlled so that an image, which has been judged to have less toner consumption, is first formed on the first surface of the recording medium while an image, which has been judged to have more toner consumption, is formed on the second surface of the recording sheet afterward. Also, in the formation process of the image, which has been judged to have less toner consumption, the fixing roller is not coated with anti-offset liquid, but in the formation process of the image, which has been judged to have more toner consumption, it is controlled so that the fixing roller is coated with the anti-offset liquid.

Abstract: In an electrophotographic process, a laser beam exposes a photoconductor according to image density level to form a latent image. In the exposure, a duty ratio of light emission period to a length of a dot is changed according to the density level. In a first mode, the duty ratio is decreased with the density level if the density level is lower than a predetermined density level, while in a second mode, the duty ratio is increased if the density level is higher than a predetermined density level. Thus, the nonlinearity of gradation characteristic is improved. A user can select a desired mode among three modes on the duty ratio to reproduce an image of desired image quality. Thus, the nonlinearity of gradation characteristic is improved, and an image can be reproduced stably.

Abstract: In a digital image forming apparatus, a user can select a desired gradation curve representing the relation of the density of reproduced image to the input image signal obtained by reading a document among a plurality of gradation data stored in a memory in correspondence to image forming conditions of an electrophotographic process of forming an image. The image forming condition is determined separately. A gradation correction data is calculated from the gradation data to realize the object gradation curve. Then, an input image signal is converted to light quantity data for a beam for exposing a photoconductor by using the calculated gradation correction data to form a latent image on a photoconductor in the image forming conditions.

Abstract: An image forming apparatus for forming images by an electrophotographic process. The image forming apparatus includes a humidity sensor for detecting the humidity in the area around the image forming members provided therein, a density sensor for detecting the density of images formed on a photoreceptor, and a humidity controller having a dehumidifying unit and a humidifying unit for adjusting the humidity in the area around image forming members. The humidity controller is operated according to humidity historical data generated based on the humidity data outputed from the humidity sensor, a detected photoreceptor potential, a detected amount of developer scattered from the developing unit or the detection result from the density sensor.

Abstract: An image density control apparatus for controlling an image density on a photoconductor surface has a charger for charging the photoconductor surface uniformly. A laser beam is scanned over the photoconductor surface to form a standard latent image having an electric potential distribution on the photoconductor surface. A potential detector detects an electric potential distribution of the standard latent image, and a developer develops a standard toner image from the standard latent image. A density detector detects a density of the standard toner image. Based on the detected electric potential distribution and the detected density, an appropriate gradation correction data is selected. The appropriate gradation correction data is selected by first selecting a gradation correction table group in accordance with the detected electric potential distribution and second selecting a gradation correction data from the gradation correction table group in accordance with the detected density.

Abstract: In an electrophotographic image forming apparatus including a charger for electrically charging the photoconductor to a predetermined initial electric potential, a laser projects a light onto the photoconductor so as to form an electrostatic latent image thereon, and a developing device develops the latent image with toner so as to form a toner image thereon. Further, a charger controller controls the charger based on a detection result of a detector for detecting a state of the photoconductor so that the initial electric potential of the photoconductor changes in a predetermined range, and a selection controller selects one of the plurality of gradation correction data stored in a storage unit based on the detection result of the detector when the initial electric potential of the photoconductor is an upper or lower limit value of the predetermined range.

Abstract: In a digital image forming apparatus with use of electrophotographic process, an electrostatic latent image is formed by modulating the intensity of laser beam according to image data to expose a photoconductor in the raster scan to form an electrostatic latent image. A scan line is divided into groups of consecutive dots, and the exposure of the photoconductor with the beam is allowed only for a predetermined light-emitting time within the time needed to scan a predetermined period of consecutive dots in the scan line direction. Thus, the exposure is stopped periodically and the smoothness of a reproduced image is improved.

Abstract: In an image-forming apparatus by using electrophotographic process, a method for stabilizing an image is provided. First, a photoconductor is sensitized with a prescribed standard sensitizing potential, and the surface potential thereof is detected. Then, the standard sensitizing potential is corrected according to the detected potential. Next, latent image patterns are formed with a plurality of light-emitting powers on a photoconductor which has been sensitized with the corrected prescribed standard potential, and the surface potentials thereof are detected. Thus, a relation between the light-emitting power and the surface potential is obtained directly. Then, the light-emitting power is determined which realizes the detected surface potential nearest to the object potential. Next, a standard toner image is formed for automatic image density control by using the corrected sensitizing potential and the selected light-emitting power.

Abstract: An apparatus and a method for forming an image with use of electrophotographic process, wherein the effect of the diffusion of electrostatic latent image and of beam size is compensated by changing the quantity of light for exposure, a gamma transformation table or a dither threshold value according to the detected value of the surface electric potential of a photoconductor or according to code information put on a support member of the photoconductor.

Abstract: The present invention relates to an image formation method and the apparatus thereof. An electrostatic latent image formed on a photosensitive body is developed with toner, and the developed toner image is electrostatically transferred onto a recording sheet held on a transfer drum; in repeating the process a plurality of images are formed on the recording sheet. The electric charge on the transfer drum is increased by repeating the electrostatic transfer of the toner image, which can cause a trouble; therefore each time an image formation is completed, the charge on the transfer drum is removed. When a part of the recording sheet held on the transfer body on which the toner image is previously formed faces the photosensitive body, the transfer body is controlled to be apart from the photosensitive drum not to disarrange the image which is previously formed on the recording sheet.

Abstract: An electrophotographic image forming apparatus includes a photosensitive member, a charger for charging the photosensitive member with a given initial potential, a laser diode for forming an electrostatic latent image by applying light to the photosensitive member charged with the initial potential, a laser driver for controlling the amount of light to be applied to the photosensitive member from the laser diode in compliance with an image density signal indicative of the density of each pixel of an image to be formed, and at least one developing device accommodating a developer consisting of toner and carrier. The electrostatic latent image formed on the photosensitive member is developed by the developer contained in the developing device.

Abstract: A developing device in an image forming apparatus has a developing sleeve through which a two-component toner material is applied onto a photosensitive surface. The developing device has an optical sensor assembly including a sensor casing opening towards the developing sleeve and closed by a transparent electroconductive windowpane to which one of two bias voltages is selectively applied for depositing or clearing toner on and off from the windowpane. The sensor assembly also includes an infrared light source for radiating infrared rays of light through the windowpane and a light receiving element for providing an output indicative of the density of toner deposited on the windowpane while the windowpane is electrically connected with the bias voltage source. A central processing unit operates in response to the output from the light receiving element to calculate the density of toner contained in the developing material. Any change in density of the toner in the developing material can be compensated for.

Abstract: In an electrophotographic image forming apparatus, a corona charger electrically charges the photoconductor to a predetermined initial electric potential so as to supply an amount of electric charge thereto, and a laser projects a light onto the charged photoconductor so as to form an electrostatic latent image thereon. A light projecting controller controls the laser to change a light amount of the projected light according to an image density signal, and a developing device develops the formed electrostatic latent image with toner so as to form a toner image thereon. Then, a voltage generator applies a developing bias voltage to the developing device.

Abstract: An apparatus such as a digital printer for forming a image with use of electrophotographic process with a reversal development system, the density is controlled automatically by varying the sensitizing electric potential V.sub.O of the photoconductor and the bias electric voltage V.sub.B of the development unit according to the detected density of the standard toner pattern, while gradation correction fog elimination and/or color balance can be performed at the same time automatically or manually by adjusting V.sub.O and V.sub.B.

Abstract: In an electrophotographic image forming apparatus wherein raster scan of a laser beam is carried out to expose the sensitized photoconductor and the gradation is expressed with intensity modulation method, the duration of the light-emitting time for forming a dot is made smaller than the whole period needed for scanning a region assigned for a dot, while the maximum light intensity is changed according to a ratio of the duration of the light-emitting time to the whole period. Further, a plurality of modes each having a duty ratio different from each other may be provided and the maximum light intensity is changed according to the duty ratio so that the mean quantity of light for a dot is equal to each other.

Abstract: A separation charger is acts on a transfer sheet after an image is transferred onto the sheet for a predetermined number of times at an ouput corresponding to the number of times the image is transferred onto the transfer sheet of a transfer drum. An image forming apparatus forms a high quality image by correcting the ouput of the transfer charger and seperation charger based on the humidity and type of copy sheet detected.

Abstract: An image forming apparatus having a plurality of develolping units containing developer the colors of which are different from each other for forming a full-color image. In this image forming apparatus, a character portion of an original is distinguished from a picture portion thereof upon the scan of the original, and the image formation for the character portion is performed in a different developing condition from the developing condition in which the image formation for the picture portion is performed.

Abstract: A humidity sensor detects a relative humidity which is one of the conditions of surroundings. CPU judges a defective detection and stops an objective image forming operation when density is decreased despite an increase in humidity or when density is increased despite a decrease in humidity basing on an image density information related to AIDC pattern supplied from AIDC sensor and basing on a humidity information supplied from the humidity sensor.

Abstract: A movable support member which supports a plurality of developing units is moved in reciprocating motion within a range of ordinary movement, and is arranged to be movable until one of the developing units arranged on either end of the plurality of developing units in the direction of reciprocating motion is out of the range of ordinary movement. In such position, it is possible to remove and replace all the developing units because they are all positioned away from a photoconductor and a pressing means which acts to push the units toward the photoconductor. Even in such a position, a lock mechanism is actuated to lock the movable support member.

Abstract: An image forming apparatus using a dual component developer. The apparatus comprises a first detection device for detecting a toner density of the developer; a second detection device for detecting an amount of a used toner; a determination device for determining an amount of the toner to be supplied in accordance with the toner density detected by the first detection means; and a revision device for revising the amount of the toner to be supplied determined by the determination means in accordance with the amount of used toner detected by the second detection means.