Abstract: A light beam position detecting device detects the passage positions of a plurality of light beams for scanning the surface of a photosensitive drum. The light beam position detecting device has a sensor pattern for generating an output which is continuously changed in a wide range with a variation in the passage position of the light beam in a sub-scanning direction perpendicular to a main scanning direction of the light beam. The sensor pattern precisely detects the relative scanning position of the light beam in a wide range. The passage positions of the plurality of light beams for scanning the surface of the photosensitive drum are controlled to a preset position based on the output of the sensor pattern.

Abstract: Four beams are caused to scan a scanning surface in the main scanning direction in parallel. The beams expose the target area between two optical sensors, not the surface of a photosensitive drum, to produce correction data to correct shifts in the exposure positions of the four beams in the main scanning direction with an accuracy of less than a small fraction of one pixel. On the basis of the correction data, an actual image formation area is set on the photosensitive drum. This makes it possible to always control the relative exposure scanning position accurately even when the relationship between the main scanning positions of the light beams is unknown.

Abstract: A light beam position detecting device detects the passage positions of a plurality of light beams for scanning the surface of a photosensitive drum. The light beam position detecting device has a sensor pattern for generating an output which is continuously changed in a wide range with a variation in the passage position of the light beam in a sub-scanning direction perpendicular to a main scanning direction of the light beam. The sensor pattern precisely detects the relative scanning position of the light beam in a wide range. The passage positions of the plurality of light beams for scanning the surface of the photosensitive drum are controlled to a preset position based on the output of the sensor pattern.

Abstract: In a digital copying machine using a multi-beam optical system, a sensor pattern SH for sensing the power of each of the light beams a to d scanning the surface of a photosensitive drum and sensor patterns SB1 to SF1, SB2 to SF2 for sensing the passing positions of the beams are provided in a light beam position sensing unit. The sensor patterns SB1 to SF1, SB2 to SF2 are arranged linearly in the sub-scanning direction at intervals corresponding to two resolutions. The power of each light beam on the surface to be scanned is controlled so as to be in a specific range. Even when the light beams are scanned with different resolutions, they can be controlled with high accuracy so as to constantly have an ideal positional relationship between them. This always assures high picture quality.

Abstract: There is provided an image forming apparatus which can implement digital control of a laser beam scan (analog amount) that moves at high speed, without using any high-speed, multi-bit A/D converter. Upon executing a digital process on the basis of analog detection value Vo corresponding to the passage position or light beam power of a light beam with which a photosensitive drum is irradiated, comparator CMP0, comparison reference value (threshold value) Vr of which changes in correspondence with detection value (integration output) Vo, is used. New comparison reference value Vr is supplied to comparator CMP0 on the basis of digital data BMDA corresponding to output CMPOUT of this comparator.

Abstract: A light beam scanner unit includes a light beam generating unit for generating light beams at a fixed power, a polygon mirror for reflecting light beams generated from the light beam generating means toward a surface to be scanned, thereby scanning it, and a light beam power sensing unit for sensing light beam power for scanning a surface to be scanned with the polygon mirror. This light beam scanner unit further has a mirror contamination sensing unit for sensing contamination of the polygon mirror by comparing a sensing result obtained from the light beam power sensing unit when light beams are emitted by the light beam generating unit with a preset reference value.

Abstract: A light beam position detecting device detects the passage positions of a plurality of light beams for scanning the surface of a photosensitive drum. The light beam position detecting device has a sensor pattern for generating an output which is continuously changed in a wide range with a variation in the passage position of the light beam in a sub-scanning direction perpendicular to a main scanning direction of the light beam. The sensor pattern precisely detects the relative scanning position of the light beam in a wide range. The passage positions of the plurality of light beams for scanning the surface of the photosensitive drum are controlled to a preset position based on the output of the sensor pattern.

Abstract: A light beam scanner unit includes a light beam generating unit for generating light beams at a fixed power, a polygon mirror for reflecting light beams generated from the light beam generating means toward a surface to be scanned, thereby scanning it, and a light beam power sensing unit for sensing light beam power for scanning a surface to be scanned with the polygon mirror. This light beam scanner unit further has a mirror contamination sensing unit for sensing contamination of the polygon mirror by comparing a sensing result obtained from the light beam power sensing unit when light beams are emitted by the light beam generating unit with a preset reference value.

Abstract: A light beam scanner unit includes a light beam generating unit for generating light beams at a fixed power, a polygon mirror for reflecting light beams generated from the light beam generating means toward a surface to be scanned, thereby scanning it, and a light beam power sensing unit for sensing light beam power for scanning a surface to be scanned with the polygon mirror. This light beam scanner unit further has a mirror contamination sensing unit for sensing contamination of the polygon mirror by comparing a sensing result obtained from the light beam power sensing unit when light beams are emitted by the light beam generating unit with a preset reference value.

Abstract: Four beams are caused to scan a scanning surface in the main scanning direction in parallel. The beams expose the target area between two optical sensors, not the surface of a photosensitive drum, to produce correction data to correct shifts in the exposure positions of the four beams in the main scanning direction with an accuracy of less than a small fraction of one pixel. On the basis of the correction data, an actual image formation area is set on the photosensitive drum. This makes it possible to always control the relative exposure scanning position accurately even when the relationship between the main scanning positions of the light beams is unknown.

Abstract: In a digital copying machine using a multi-beam optical system, a light beam position detector situated on a line extended from the surface of a photosensitive drum detects the passing position of each light beam scanned by a polygon mirror rotated by a polygon motor. A CPU calculates control amounts for galvanomirrors by using a beam position detector output processor, on the basis of the detection result of the beam position detector. Based on the calculated control amounts, galvanomirror drive circuits drive the galvanomirrors, thereby to control the positions of the beams in a sub-scan direction. The passing positions of the beams can be precisely detected with no special precision in assembling the optical system. In addition, the positions of the beams in the sub-scan direction can be controlled at predetermined positions, even if some change occurs in the structure of the optical system due to a variation in ambience or a variation with the passing of time.

Abstract: Four beams are caused to scan a scanning surface in the main scanning direction in parallel. The beams expose the target area between two optical sensors, not the surface of a photosensitive drum, to produce correction data to correct shifts in the exposure positions of the four beams in the main scanning direction with an accuracy of less than a small fraction of one pixel. On the basis of the correction data, an actual image formation area is set on the photosensitive drum. This makes it possible to always control the relative exposure scanning position accurately even when the relationship between the main scanning positions of the light beams is unknown.

Abstract: A light beam is made to scan and expose a photosensitive drum in the main scanning direction and the passing position of the light beam in the sub-scanning direction is sensed. On the basis of the result of the sensing, the light beam is shifted in the sub-scanning direction when the beam is made to scan by a scanner so that the passing position may come in a target range, which brings the passing position to the proper position. After the position control, the passing position of the light beam is confirmed and controlled so that the passing position may fall on the proper position a specific number of times consecutively. When the light beam is shifted in the sub-scanning direction, the passing position of the light beam is brought into a final target range in such a manner that the target range is forced to converge stepwise in a first range and then in a second range narrower than the first range.

Abstract: In a digital copying mechine using a multi-beam optical system, first light receiving elements of a light beam detector placed on the extension of the surface of a photosensitive drum detects the positions of paths of scanning light beams in the sub-scanning direction. On the basis of the results of this detection, the amount of control for the position of the path of each light beam is calculated. Galvano mirrors, adapted to reflect the light beams onto the surface of the photosensitive drum, are driven accordingly, so that the paths of the light beams are properly positioned in the sub-scanning direction. Second light receiving elements of the light beam detector detect times at which the light beams move across the light beam detector. A sync clock is produced after a delay from when each light beam moves across the light beam detector.

Abstract: A beam position detector output processor converts an output from a beam position detector into beam position information. A main control unit detects a total offset value of a plurality of operational amplifiers constituting the processor. The detected offset value is used to compensate a determination reference value used to control the sub-scanning position of a beam, or the beam position information obtained from the beam position detector output processor. As a result, the offsets of the operational amplifiers constituting the beam position detector output processor are compensated.

Abstract: A beam passing position controlling apparatus comprises a light source for emitting a beam, a mechanism for reflecting the beam toward an image carrier surface to scan the image carrier surface, a sensor for detecting a position where the beam passes on the image carrier surface, a circuit for calculating a correction amount from the position detected, a mechanism for correcting the passing position of the beam on the basis of the correction amount, and a circuit for controlling respective operations of the apparatus.

Abstract: An image forming apparatus includes image forming units to transfer images onto an image receiving medium that is moved in a specified direction together with a conveyor belt which conveys the image receiving medium. The image forming units of the apparatus form test patterns on the conveyor belt or the image receiving medium. The test patterns include a leading edge and a trailing edge along the specified direction defining a distance therebetween, the distance varying continuously.

Abstract: An image forming apparatus including a plurality of latent image forming units for forming latent images on a plurality of image carriers, a plurality of developing devices for forming developed images by developing the latent images formed by the latent image forming units, and an image conveyer belt for conveying the developed images formed by the developing devices. The image forming apparatus further contains a registration sensor for detecting the developed images conveyed on the image conveyer belt, and the registration sensor has a light source, a first optical fiber element for guiding the light from the light source and illuminating the image conveyer belt to obtain the reflected light, a second optical fiber element for guiding the reflected light in a specified direction, and a light receiving element for converting the reflected light guided by the second optical fiber element into an electric signal.

Abstract: An image forming apparatus includes plural latent image forming units for forming latent images on plural image carriers, plural developing units for developing the latent image formed on the image carriers and plural transfer units for transferring the color images developed on the image carriers to an image receiving medium conveyed by a medium support member. This image forming apparatus also includes a first detector for detecting a test pattern. This first detector has a light projecting portion and a light receiving portion which is arranged in parallel with the running direction of the medium support member. The image forming apparatus has a computing unit which computes misregistration of color images developed and transferred onto one of the medium support member and the image receiving medium based on a difference between a detection result by the detector and a threshold value. The misregistration of color images are corrected based on the results of computation by the computing unit.

Abstract: In a printer head constituted by a large number of linearly arranged LEDs, a lighting time designator receives image data at a period corresponding to one scanning period, designates a lighting time of each LED within one scanning period in accordance with image data corresponding to each LED and the lighting capacity of each LED, and outputs lighting time data. A lighting mode designator determines a lighting mode for designating a timing, within one scanning period, at which each LED is caused to emit light, on the basis of image data, and outputs lighting mode designation data. A light timing controller divides one scanning period into a plurality of time intervals and supplies the lighting time data to the printer head a plurality of number of times within one scanning period at the time intervals on the basis of the lighting mode designation data, thereby selectively causing the respective LEDs to emit light.