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.

Abstract: A gradation patch image Ip used for determination of tone characteristics of an apparatus is progressively varied in the tone level thereof from the maximum tone level (level 255) to the minimum tone level (level 0). The gradation patch image is either a toner image continuously and consistently varied in the tone level thereof (FIG. 3A) or a toner image having the tone levels varied stepwise at a smaller pitch than a width of a detection region of a patch sensor (FIG. 3B). In density detection of such a gradation patch image Ip, toner image densities at portions on either sides in the detection region of the patch sensor are canceled each other out by averaging and hence, only a toner image density substantially at the center of the detection region can be obtained.

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: A light emitting element irradiates light upon a surface area of an intermediate transfer belt which is wound around a roller, i.e., upon a wind area, and light receiving units receive light reflected at the wind area. Based on a signal outputted from a sensor, the quantity of toner is measured. In the wind area, the intermediate transfer belt does not flap in a direction which is approximately perpendicular to a direction in which the belt travels. This suppresses a change in distance (sensing distance) between the sensor and the intermediate transfer belt.

Abstract: A development bias calculation and an electrifying bias calculation are executed in this order. In the development bias calculation, a plurality of toner images are formed as first patch images while changing the development bias. An optimal development bias, which is necessary to obtain the target density, is determined based on densities of the first patch images. In the electrifying bias calculation, toner images are formed as second patch images while changing the electrifying bias with the development bias fixed to the optimal development bias. An optimal electrifying bias, which is necessary to obtain the target density, is determined based on densities of the second patch images.

Abstract: A toner quantity measuring apparatus in which an input offset voltage is applied to the output side of an irradiation quantity monitoring light receiving element, so that a light emitting element remains turned off unless a light quantity control signal exceeds a predetermined signal level. Prior to irradiation of light upon an intermediate transfer belt and measurement of a toner quantity, a light quantity control signal below the predetermined signal level is supplied to an irradiation quantity adjusting unit and the light emitting element is turned off without fail. A memory stores, as a dark output voltage, an output voltage from a reflection quantity detecting unit upon the turning off. Light reflected from the intermediate transfer belt is split into p-polarized and s-polarized light to detect a toner quantity and colors of the toner.

Abstract: An improved optical scanning apparatus is adapted to be such that at either end of the scan range, an optical beam deflected by a reflecting surface of a scanner will pass through an anamorphic lens in scanning optics at a position spaced from its optical axis in the sub-scanning direction. The anamorphic lens has such a sectional profile in the sub-scanning direction that the lens thickness at one end of the sub-scanning direction differs from the thickness at the other end. Also, a high speed optical scanning apparatus based on the dual incidence and the oblique incidence, can prevent a positional variation of a scanning line that is due to a shift of each facet of the rotating polygonal mirror, which is caused by an offset of the rotating axis of the rotating polygonal mirror.

Abstract: A light emitting element irradiates light upon a surface area of an intermediate transfer belt which is wound around a roller, i.e., upon a wind area, and light receiving units receive light reflected at the wind area. Based on a signal outputted from a sensor, the quantity of toner is measured. In the wind area, the intermediate transfer belt does not flap in a direction which is approximately perpendicular to a direction in which the belt travels. This suppresses a change in distance (sensing distance) between the sensor and the intermediate transfer belt.

Abstract: In an apparatus, first and second processing modes are prepared to determine an optimal development bias. Either one of the first processing mode and the second processing mode is selected as a processing mode in accordance with an operation status of the apparatus. Hence, it is possible to select and execute the most appropriate processing mode in accordance with an operation status to thereby efficiently and highly accurately determine an optimal value of a development bias which is one density controlling factor.

Abstract: An input offset voltage is applied to the output side of an irradiation quantity monitoring light receiving element, so that a light emitting element remains turned off unless a light quantity control signal exceeds a predetermined signal level. Prior to irradiation of light upon an intermediate transfer belt and measurement of a toner quantity, a light quantity control signal below the predetermined signal level is supplied to an irradiation quantity adjusting unit and the light emitting element is turned off without fail. A memory stores, as a dark output voltage, an output voltage from a reflection quantity detecting unit upon the turning off. In actual measurement of a toner quantity, with light irradiated upon the intermediate transfer belt, the dark output voltage is subtracted from the output voltage outputted from the reflection quantity detecting unit, whereby an influence of the dark output voltage is eliminated.

Abstract: A development bias calculation and an electrifying bias calculation are executed in this order. In the development bias calculation, a plurality of toner images are formed as first patch images while changing the development bias. An optimal development bias, which is necessary to obtain the target density, is determined based on densities of the first patch images. In the electrifying bias calculation, toner images are formed as second patch images while changing the electrifying bias with the development bias fixed to the optimal development bias. An optimal electrifying bias, which is necessary to obtain the target density, is determined based on densities of the second patch images.

Abstract: In an apparatus, first and second processing modes are prepared to determine an optimal development bias. Either one of the first processing mode and the second processing mode is selected as a processing mode in accordance with an operation status of the apparatus. Hence, it is possible to select and execute the most appropriate processing mode in accordance with an operation status to thereby efficiently and highly accurately determine an optimal value of a development bias which is one density controlling factor.

Abstract: In an apparatus, first and second processing modes are prepared to determine an optimal development bias. Either one of the first processing mode and the second processing mode is selected as a processing mode in accordance with an operation status of the apparatus. Hence, it is possible to select and execute the most appropriate processing mode in accordance with an operation status to thereby efficiently and highly accurately determine an optimal value of a development bias which is one density controlling factor.

Abstract: A development bias calculation and an electrifying bias calculation are executed in this order. In the development bias calculation, a plurality of toner images are formed as first patch images while changing the development bias. An optimal development bias, which is necessary to obtain the target density, is determined based on densities of the first patch images. In the electrifying bias calculation, toner images are formed as second patch images while changing the electrifying bias with the development bias fixed to the optimal development bias. An optimal electrifying bias, which is necessary to obtain the target density, is determined based on densities of the second patch images.

Abstract: An improved optical scanning apparatus is adapted to be such that at either end of the scan range, an optical beam deflected by a reflecting surface of a scanner will pass through an anamorphic lens 13 in scanning optics at a position spaced from its optical axis in the sub-scanning direction. The anamorphic lens has such a sectional profile in the sub-scanning direction that the lens thickness at one end of the sub-scanning direction differs from the thickness at the other end. Also, a high speed optical scanning apparatus based on the dual incidence and the oblique incidence, can prevent a positional variation of a scanning line that is due to a shift of each facet of the rotating polygonal mirror, which is caused by an offset of the rotating axis of the rotating polygonal mirror.

Abstract: To provide an optical scanner for typical use with laser beam printers that is capable of effective correction of aberrational characteristics and which also produces a constant beam spot size, a semiconductor laser array 1 having a plurality of light-emitting portions issues a plurality of beams, which are reflected and deflected by reflecting surfaces of rotating polygonal mirror 5 and pass through imaging lens 6 to form a plurality of beam spots on the surface to be scanned 7. Both the entrance and exit surfaces of imaging lens 6 are such that the curvatures in the sub- and main scanning directions are independent of each other, with the curvature in the sub-scanning direction varying continuously in the main scanning direction over the effective area of imaging lens 6.

Abstract: An optical scanner that has a simple construction and which yet exhibits satisfactory imaging performance under varying temperature conditions. Of the two orthogonal scanning cross sections of scanning optics (i.e., the main and sub-scanning cross sections), the one that involves the greater movement of the image plane due to the temperature-dependent changes in optical characteristics (e.g. the variation in the operating wavelength of a light source, the index variation of a lens material and the thermal expansion of a lens itself) is adapted to be the same as the other cross section that involves the greater movement of the image plane due to the change in the distance from the light source to a collimator lens.

Abstract: An optical scanner for use in laser beam printers and the like which is particularly satisfactory in imaging characteristics. A light beam from a semiconductor laser passes through a collimator lens, an aperture diaphragm and a cylindrical lens. The beam is then deflected by a rotating lens mirror and subjected to the focusing action of an imaging lens so that it is focused to form a beam spot, which scans over a scan surface as the beam is deflected. The imaging lens has aspheric surfaces in the main-scanning cross section and is designed so that the rate of change in its curvature and other relevant parameters satisfy a predetermined equation so as to lie within a predetermined range.

Abstract: An optical scanner comprises: a light source; beam shaping optics for transforming an optical beam from the light source into a convergent beam; a rotating polygonal mirror having at least a first reflecting face for deflecting the convergent beam and a second reflecting face; and transmission optics having a lens, with which the optical beam deflected by the first reflecting face of the rotating polygonal mirror is allowed to be incident on the second reflecting face of the rotating polygonal mirror, with the optical beam incident on the second reflecting face of the rotating polygonal mirror being deflected therefrom to produce a scanning optical beam which scans a predetermined surface to be scanned, wherein the convergent optical beam forms a focused image at a point located between the first reflecting face of the rotating polygonal mirror and the lens in the transmission optics.

Abstract: An optical scanner that has a simple construction and which yet exhibits satisfactory imaging performance under varying temperature conditions. Of the two orthogonal scanning cross sections of scanning optics (i.e., the main and sub-scanning cross sections), the one that involves the greater movement of the image plane due to the temperature-dependent changes in optical characteristics (e.g. the variation in the operating wavelength of a light source, the index variation of a lens material and the thermal expansion of a lens itself) is adapted to be the same as the other cross section that involves the greater movement of the image plane due to the change in the distance from the light source to a collimator lens.