Minolta Company, Ltd.

Yukihiko Okuno

Kentaro Katori

Katsuyuki Hirata

Masaki Tanaka

Yoshinobu Hada

Masahiro Kouzaki

Toshifumi Watanabe

Atsushi Kawai

Naoyoshi Kinoshita

Mineyuki Sako

Suguru Hamamichi

Shinichi Yoshimoto

Tetsuya Sakai

Yoshihiro Shojo

Hironobu Nakata

Kentro Katori

An image forming apparatus for forming an image with few defects even when making a copy from a copied image. When forming an image, a standard pattern is formed outside the image forming area in accordance with standard pattern data for color correction. When reading the image together with the standard pattern formed above, the color correction conditions for the image data are modified in accordance with the comparison result between the read standard pattern data and the standard pattern data for color correction. Copying is then performed on a copying paper.

Image forming apparatus which excels in reproducibility of colors, fine lines and gradations even in a copy made from a copied image

In a vertical type developing device in which plurality of screws are arranged up and down, developer transported by an upper developer transporting screw and developer transported by lower developer transporting screw are properly dispersed. Thereby, developer flows smoothly and further stirs and mixes. As means of it, the followings are included: (1) between the upper screw and the lower screw, properly adjusting developer transporting capabilities and dispersing pressures; (2) arrangement of dispersing members between the upper and lower developer transporting screws; (3) arrangement of openings at a partition wall; (4) arrangement of a developer reservoir portions to a developer accommodating unit; or the like.

Developing device with mechanism for smoothly circulating developer

The present invention is to provide a developing apparatus having a supply screw and a recovery screw both of which are arranged vertically to circulate developer, wherein a component in a normal direction of pressure generated by the recovery screw is made larger than that of pressure generated by the supply screw. Thereby, lowering and raising of developer is suppressed and occurrence of fog on the image and the smoke of toner are prevented. Alternatively, a radial member and a centrifugal member are applied to the supply screw and the recovery screw, respectively. Thereby, developer is prevented from moving between screws in the midst of the transportation. Still alternatively, a preliminary stirring portion is provided on extension of a stirring screw at upperstream side. The preliminary stirring portion has a cylindrical body with inlets and outlets. Both inside and outside of the cylindrical body, screws are provided and inclines of screw blades are reversed to each other. Thereby, it enables the developing apparatus to transport the developer which is sufficiently stirred and charged to a development zone without being accompanied by a large-scaled apparatus.

Developing apparatus having improved developer distribution

Pixel data comprising density data of R, G, and B obtained by reading an original with a CCD image sensor are subjected to shading correction by a shading correction unit, and then converted into color region signals H*, V, and C* in the Munsell color space by a first converter. According to the variations of V, a region discriminator determines whether each pixel data belongs to an edge portion of the original image or whether it belongs to a uniform density region of the original image. A noise removing unit performs noise removal by performing smoothing on color region signals H*, V, and C* of the pixel data which have been determined to belong to uniform density regions. A second converter converts the noise-removed color region signals into pixel data of R, G, and B.

Image forming apparatus having a noise removing unit

A digital copying machine develops an electrostatic latent image formed on a photosensitive drum with toner, and transfers the developed image onto a sheet. In forming images on the photosensitive drum successively, three types of test patterns are formed in order in intro-image areas between image forming areas, and AIDC is made. The first test pattern is a low-density pattern, the second test pattern is an intermediate-density pattern, and the third test pattern is a high-density pattern.

Image forming apparatus

An image forming apparatus which forms an image according to image data made up of pixel data on colors of pixel constituting an original image, characterized by comprising a color region discriminator for determining to which color region each pixel data belongs, an image region discriminator for determining whether the pixel data belongs to a uniform density region or whether it belongs to an edge portion, a corrective condition deciding unit for determining MTF corrective conditions for the image data of each color region depending on the discrimination results of both the color region discriminator and the image region discriminator, and an MTF correction unit for performing MTF corrections on the image data according to the MTF corrective conditions determined by the corrective condition deciding unit.

Image forming apparatus having an MTF correction unit

A test pattern comprising a half-tone pattern portion and an edge pattern portion printed according to standard printing data is read by a CCD sensor. A pattern discriminator detects the positions of the half-tone pattern portion and the edge pattern portion. In accordance with a prescribed edge detection criteria using the primary differential data .DELTA.D of density determined by primary differential filters, the CPU determines whether the inputted image data correspond to a uniform density region or whether the inputted image data correspond to an edge portion. If the region discrimination result is different from the result of the pattern detection, the edge detection criteria are changed. The image data is then subjected to MTF correction, and conditions for smoothing or edge emphasizing are altered so that the difference between the corrected image data and the standard printing data remains within a allowable range.

Image forming device and method having MTF correction

Using an image forming apparatus, toner images are respectively formed on photosensitive drums of image forming units set along a transport belt, and the toner images are transferred onto the transport belt or a recording sheet transported on the transport belt to form a color image. The image forming apparatus is composed of a first density detecting sensor for detecting a density of a toner image formed on the recording sheet or the transport belt at the upstream side of each transfer position of at least one image forming unit which is located at the downstream side of a first image forming unit in a transport direction of the transport belt and which is selected as a subject of an image forming condition determination, a second density detecting sensor for detecting a density of the toner image formed on the recording sheet or the transport belt at the downstream side of the transfer position, and an image forming condition determining unit for comparing a detection value given by the first density detecting sensor with a detection value given by the second density detecting sensor and for determining an image forming condition in accordance with the comparison result for an image formation performed by the image forming unit selected as the subject.

Tandem-type image forming apparatus and image forming condition

The individual pattern of each color of the standard pattern is printed on a copy being made, and when the copy is read by a scanner, the image data of the standard pattern are converted into color region signals in a uniform color space by an HVC converter and a C.multidot.H operation unit. In the case where the saturation of the image data has become lower than the standard saturation of the color region, saturation corrective coefficients are determined by a saturation corrective coefficient calculation unit. After the saturation coefficients have been determined for each color of the standard pattern, the image data of the original are read out, and the saturation corrective coefficients for the color region of the image data are used for saturation correction by a saturation correction processing unit. The image data which have been subjected to the saturation correction are reversely converted into the image data of each color by a reverse HVC converter. According to the reversely converted image data, an image is formed on a copying paper.

Image forming apparatus having a saturation correction unit

A supply screw 10 and a collection screw 20 for a developing device equip with screw blades having different forms at particular sections so as to make conveying force of developer different depending on sections. Screw blades for big conveying force are attached within sections where developer distribution is dense while screw blades for small conveying force are attached within sections where developer distribution is sparse. In other words, conveying force is made to be greater at sparse-distribution section while smaller at dense-distribution section. Developer delivery is also promoted by providing different conveying force area within carry-up area where developer is carried up from a supply screw 10 to a collection screw 20 or vice versa. By making conveying force of each section different, developer is uniformly delivered to a developing roll 87 whether in width direction or in axial direction. Furthermore, developer circulation in a developing device becomes smooth.

Developing device

An image forming apparatus is provided which is immune to characteristic variations of a photoconductor and a developer material, which can detect the amount of toner adhering to a test toner image accurately, and which can always form a favorable image using an optimal image forming parameter. A predetermined test toner image is formed on the photoconductor using developing devices. The amount of toner adhering to the formed test toner image is detected by an AIDC sensor. A printer control unit determines grid potential Vg of a corona charger and development bias potential Vb of each developing device based on the detected amount of adhering toner. A predetermined image is formed using the determined grid potential and development bias potential. The printer control unit changes the image forming condition for the next test toner image based on the detected amount of adhering toner so that the amount of toner adhering to the next test toner image can be detected in a range of high detection sensitivity of the AIDC sensor.

Digital image forming apparatus with test image optimization

In an electrophotographic image forming apparatus, a correction coefficient corresponding to each density level of toner consumption of a developing device is determined in accordance with a selected tone correction method, and/or the ratio of the emission period to the non-emission period of a light source. A toner consumption calculator multiplies the correction coefficients by the number of pixels of each density level of document image data, and determines the amount of toner consumed by the developing device from the sum total value of the multiplication results determined for each density level. A toner replenishment device resupplies toner to the developing device based on the determined amount of consumed toner. As a result, a constant toner concentration Tc normally can be maintained because toner is resupplied based on the calculated amount of toner consumption.

Image forming apparatus which calculates toner consumption in accordance

In a digital image forming apparatus, when a latent image is formed on a photoconductor, a light from a light source is emitted in a period of a duty ratio while modulated according to image data, and the latent image is developed and transferred onto a sheet of paper. The duty ratio, defined as a ratio of a light-emitting time of a light exposing the photoconductor to a period for exposing a dot, is changed in the same document according to dot information on the document such as an edge signal. In the modulation of the optical intensity, the light emission onto the photoconductor is performed with a duty ratio which may be set for each dot. Image portions formed with different duty ratios may exist at the same time in a reproduced image. For example, an edge portion in a document is reproduced at the duty ratio of 100% while a non-edge portion is reproduced at the duty ratio less than 100%.

Digital image forming apparatus and method with variable duty ratio

An image formation apparatus for forming a full color image in the four colors of cyan, magenta, yellow and black has a optical ATDC sensor attached in a cyan developing device to control the toner density under optical ATDC. A black developing device has the toner density controlled by AIDC. A standard develop efficiency .eta.STD of the cyan developing device obtained as a result of the AIDC is compared with a develop efficiency .eta. of black toner. The toner supply amount of the black developing device is determined according to the comparison result to supply the toner. Thus, an image formation apparatus is provided that can detect at favorable accuracy the toner density of a developing device incorporating a developer of which the toner density cannot be detected using optical ATDC to supply a required amount of toner.

Image formation apparatus that can maintain appropriately toner density

The image forming apparatus is provided with a detecting means for detecting transfer efficiency when transferring a toner image from a photosensitive member to a transfer sheet, and a developing efficiency changing means for changing developing efficiency based on the transfer efficiency detected by the detecting means, and corrects the toner consumption predicted by the predicting means based on the transfer efficiency as detected by the detecting means, so as to determine the amount of toner to be replenished. When the developing efficiency is changed based on the transfer efficiency, toner consumption also changes, and does not match the predicted toner consumption. According to the present invention, toner concentration in a developer can be even more accurately controlled by correcting the predicted toner consumption by the change in transfer efficiency. Detection of transfer efficiency is achieved by a method of indirectly detecting humidity in the apparatus, or a method of measuring the amount of toner transferred to a transfer member.

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Toyokawa, Japan

Yukihiko Okuno