Abstract: An image It is formed as a patch image which includes a header image portion Ih of a solid image having a length of a circumferential length of a developing roller or more, and a gradation image portion Ig progressively varied in the tone level thereof from the maximum level to the minimum level. The densities of the patch image on an intermediate transfer belt are sampled. However, the sampling results contain errors resulting from noises or variations and hence, are subjected to a noise removal process, a periodical variation correction process and a reverse correction process. The results detected on the intermediate transfer belt do not always coincide with image densities (OD values) on a recording material. Therefore, the detection results are converted into the OD values, based on which tone characteristics of an apparatus is estimated. Then a tone correction table is updated in a manner to compensate for the tone characteristics.

Abstract: An image forming apparatus for forming an image corresponding to an image signal on a recording material, comprising: a signal processor which generates an image-formation control signal by subjecting the image signal to a signal processing process including a screening process selectively using one of plural types of different processing screens; an image forming unit which includes an intermediate transfer medium, and which forms the image by forming a toner image on the intermediate transfer medium corresponding to the image-formation control signal and transferring and fixing the toner image to a recording material; and a detector which detects a quantity of the toner carried on the intermediate transfer medium as the toner image, wherein the signal processing process performed by the signal processor includes a tone correction process for compensating for a gamma characteristics of the apparatus based on a detection result given by the detector detecting a toner image formed as a patch image by using the

Abstract: Based on a video signal, a toner dot counter and an off dot counter detect a size of a toner dot portion to carry an adherent toner thereto and a size of an off dot portion not to carry an adherent toner, respectively. Reference is made to a look-up table based on the detection results, so as to retrieve a coefficient Kv corresponding to a combination of the sizes of the toner dot portion and the off dot portion. A count value Cdot given by the toner dot counter is multiplied by the coefficient Kv, while the resultant product is integrated by an accumulator. An integration value for an image of one page is multiplied by a coefficient K0 equivalent to a toner adhesion percentage of solid image. Thus is determined a toner consumption TC on the page image.

Abstract: Based on a video signal, a toner dot counter and an off dot counter detect a size of a toner dot portion to carry an adherent toner thereto and a size of an off dot portion not to carry an adherent toner, respectively. Reference is made to a look-up table based on the detection results, so as to retrieve a coefficient Kv corresponding to a combination of the sizes of the toner dot portion and the off dot portion. A count value Cdot given by the toner dot counter is multiplied by the coefficient Kv, while the resultant product is integrated by an accumulator. An integration value for an image of one page is multiplied by a coefficient K0 equivalent to a toner adhesion percentage of solid image. Thus is determined a toner consumption TC on the page image.

Abstract: Based on a video signal, a toner dot counter and an off dot counter detect a size of a toner dot portion to carry an adherent toner thereto and a size of an off dot portion not to carry an adherent toner, respectively. Reference is made to a look-up table based on the detection results, so as to retrieve a coefficient Kv corresponding to a combination of the sizes of the toner dot portion and the off dot portion. A count value Cdot given by the toner dot counter is multiplied by the coefficient Kv, while the resultant product is integrated by an accumulator. An integration value for an image of one page is multiplied by a coefficient K0 equivalent to a toner adhesion percentage of solid image. Thus is determined a toner consumption TC on the page image.

Abstract: Based on a video signal, a toner dot counter and an off dot counter detect a size of a toner dot portion to carry an adherent toner thereto and a size of an off dot portion not to carry an adherent toner, respectively. Reference is made to a look-up table based on the detection results, so as to retrieve a coefficient Kv corresponding to a combination of the sizes of the toner dot portion and the off dot portion. A count value Cdot given by the toner dot counter is multiplied by the coefficient Kv, while the resultant product is integrated by an accumulator. An integration value for an image of one page is multiplied by a coefficient K0 equivalent to a toner adhesion percentage of solid image. Thus is determined a toner consumption TC on the page image.

Abstract: Based on a video signal, a toner dot counter and an off dot counter detect a size of a toner dot portion to carry an adherent toner thereto and a size of an off dot portion not to carry an adherent toner, respectively. Reference is made to a look-up table based on the detection results, so as to retrieve a coefficient Kv corresponding to a combination of the sizes of the toner dot portion and the off dot portion. A count value Cdot given by the toner dot counter is multiplied by the coefficient Kv, while the resultant product is integrated by an accumulator. An integration value for an image of one page is multiplied by a coefficient K0 equivalent to a toner adhesion percentage of solid image. Thus is determined a toner consumption TC on the page image.

Abstract: When the remaining toner amount within a developer is relatively large, a control target value of a toner amount is set to Ttgt1, and a lower limit value of a toner amount which can regarded proper is set to TL1. When the density of a patch image formed under a predetermined condition is smaller than a minimum guaranteed density Dma, it is determined abnormality has occurred in the apparatus. Since the characteristic of toner within the developer changes as the remaining toner amount decreases, the control target value is changed to Ttgt2 and the lower limit value is set to TL2 in light of this. In this fashion, regardless of whether the toner characteristic has changed, abnormality in the apparatus is detected without fail.

Abstract: In a density control technique wherein a density of a toner image formed as a patch image is detected for performing density control based on the detected result, detection errors are decreased so as to properly set a density control factor. The density control factor is optimized based on a variation rate of the patch image densities against a varied density control factor. The detected results of the patch image densities are corrected based on information on an image carrier acquired before the formation of the patch images.

Abstract: Optimization of a density control factor accompanying formation of a patch image is executed every time a predetermined period of time elapses since the end of a preceding image forming operation. Since an image is formed at regular intervals in this manner, it is possible to suppress a density variation which is created as toner carried on a developer roller is left unused for long. This effect further improves when the developer roller is rotated idle prior to formation of a patch image or regularly at predetermined timing.

Abstract: An image forming apparatus for forming an image corresponding to an image signal on a recording material, comprising: a signal processor which generates an image-formation control signal by subjecting the image signal to a signal processing process including a screening process selectively using one of plural types of different processing screens; an image forming unit which includes an intermediate transfer medium, and which forms the image by forming a toner image on the intermediate transfer medium corresponding to the image-formation control signal and transferring and fixing the toner image to a recording material; and a detector which detects a quantity of the toner carried on the intermediate transfer medium as the toner image, wherein the signal processing process performed by the signal processor includes a tone correction process for compensating for a gamma characteristics of the apparatus based on a detection result given by the detector detecting a toner image formed as a patch image by using the

Abstract: In a density control technique wherein a density of a toner image formed as a patch image is detected for performing density control based on the detected result, detection errors are decreased so as to properly set a density control factor. The density control factor is optimized based on a variation rate of the patch image densities against a varied density control factor. The detected results of the patch image densities are corrected based on information on an image carrier acquired before the formation of the patch images.

Abstract: Optimization of a density control factor accompanying formation of a patch image is executed every time a predetermined period of time elapses since the end of a preceding image forming operation. Since an image is formed at regular intervals in this manner, it is possible to suppress a density variation which is created as toner carried on a developer roller is left unused for long. This effect further improves when the developer roller is rotated idle prior to formation of a patch image or regularly at predetermined timing.

Abstract: In a density control technique wherein a density of a toner image formed as a patch image is detected for performing density control based on the detected result, detection errors are decreased so as to properly set a density control factor. The density control factor is optimized based on a variation rate of the patch image densities against a varied density control factor. The detected results of the patch image densities are corrected based on information on an image carrier acquired before the formation of the patch images.

Abstract: Optimization of a density control factor accompanying formation of a patch image is executed every time a predetermined period of time elapses since the end of a preceding image forming operation. Since an image is formed at regular intervals in this manner, it is possible to suppress a density variation which is created as toner carried on a developer roller is left unused for long. This effect further improves when the developer roller is rotated idle prior to formation of a patch image or regularly at predetermined timing.

Abstract: When the remaining toner amount within a developer is relatively large, a control target value of a toner amount is set to Ttgt1 and a lower limit value of a toner amount which can regarded proper is set to TL1. When the density of a patch image formed under a predetermined condition is smaller than a minimum guaranteed density Dma, it is determined abnormality has occurred in the apparatus. Since the characteristic of toner within the developer changes as the remaining toner amount decreases, the control target value is changed to Ttgt2 and the lower limit value is set to TL2 in light of this. In this fashion, regardless of whether the toner characteristic has changed, abnormality in the apparatus is detected without fail.

Abstract: Based on a video signal, a toner dot counter and an off dot counter detect a size of a toner dot portion to carry an adherent toner thereto and a size of an off dot portion not to carry an adherent toner, respectively. Reference is made to a look-up table based on the detection results, so as to retrieve a coefficient Kv corresponding to a combination of the sizes of the toner dot portion and the off dot portion. A count value Cdot given by the toner dot counter is multiplied by the coefficient Kv, while the resultant product is integrated by an accumulator. An integration value for an image of one page is multiplied by a coefficient K0 equivalent to a toner adhesion percentage of solid image. Thus is determined a toner consumption TC on the page image.

Abstract: Output signals Vp from a density sensor are sampled for plural positions on an intermediate transfer belt and an amount of toner adhesion is determined based on the results of sampling. Since these sample data pieces may contain noises, each predetermined number of data pieces of higher order and of lower order are removed from the resultant sample data string. The removed data pieces are each replaced by an average value Vpavg of the other sample data pieces. The amount of toner adhesion is calculated based on the data string thus replaced.

Abstract: For optimization of a direct current developing bias Vavg, a patch image Ivn is formed whose length is longer than a circumferential length L0 of a photosensitive member. From an average value of sensor outputs sampled over the length L0 of the patch image, a toner density of the patch image Ivn is calculated and a value corresponding to an average value ODavg of optical densities OD is accordingly found. This cancels an influence of density variations appearing in association with rotating cycles of the photosensitive member exerted over a patch image.

Abstract: A condition controlling process is executed when parameters expressing a state of toner within a developer reaches predetermined threshold values. On each one of two parameters, namely, a dot count value which is indicative of a toner consumption amount (an integrated value of the number of dots formed using an exposure beam) and a developer roller rotating time which is indicative of the degree of toner fatigue, a threshold value (denoted at the dotted lines) which triggers execution of the condition controlling process is set. At the time that the path d of dots which are expressed as combinations of these parameters intersects each dotted line (the intersections (1) through (6)), the condition controlling process is executed.