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 first trench is formed in a surface of an n+-type semiconductor substrate that forms a source region. A p-type base region, an n−-type drift region, and an n+-type drain region are deposited in this order in the first trench using epitaxial growth. A second trench extending from the source region to the drift region through the base region is formed in the surface. A gate insulating film and a gate electrode are formed on a surface defining the second trench. The n+-type drain region has a location where growing surfaces come together in epitaxial growth and where a defect is likely to occur, and the gate electrode lacks such a location and thus avoids an increase in normalized ON resistance. Therefore, the breakdown voltage remains high without increasing the ON resistance.

Abstract: An image forming apparatus maintains a constant beam scanning state so that, light beams scan each drum always in the same state once a desired color overlapping accuracy is obtained by controlling color registration in color image formation. This mechanism achieves constantly fine color overlapping without forming a test pattern several times or consuming toner unnecessarily. A beam passage switch is provided in a laser scanning system. Sensors provided near each photosensitive drum determine whether each light beam has scanned a certain portion with no inclination or a certain scanning area, or whether each image magnification provides a desired size.

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 pair of sensor patterns detect a passage position in a sub-scan direction of a light beam scanned over a surface of a photosensitive drum. The sensor patterns have, for example, trapezoidal shapes and are disposed symmetrical at a position equivalent to a position of the surface to be scanned. The sensor patterns are juxtaposed in a scan direction of the light beam at a predetermined interval therebetween. An output integration value from one of the paired photodetector elements successively increases while an output integration value from the other photodetector element successively decreases in relation to a variation of a passage position of the light beam in the sub-scan direction. On the basis of a difference between the output integration values of the paired sensor patterns, the passage position of the light beam in the sub-scan direction is detected.

Abstract: Two sawtooth sensor patterns are combined so that they engage with each other. These sensor patterns are arranged so that a light beam passes sawtooth portions in a horizontal scan direction. A light beam's scan position is determined by integrating a difference between output signals from these sensor patterns. It is possible to provide a highly sensitive circuit for processing signals from the sensors and to improve detection accuracy for light beams.

Abstract: A synchronization signal detector receives a laser beam each time it is scanned in a main scanning direction, and detects a synchronization signal from the received laser beam. An external circuit or the like sets a binary value-determining level for this detector. The binary value-determining level is so determined as not to generate a signal arising from stray light. By this determination, a synchronization error, which is due to stray light, is prevented without adding manufacturing steps to prevent the stray light or without incurring an increase in the cost needed for structural components.

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: An image forming apparatus maintains a constant beam scanning state so that light beams scan each drum always in the same state once a desired color overlapping accuracy is obtained by controlling color registration in color image formation. This mechanism achieves constantly fine color overlapping without forming a test pattern several times or consuming toner unnecessarily. A beam passage switch is provided in a laser scanning system. Sensors provided near each photosensitive drum determine whether each light beam has scanned a certain portion with no inclination or a certain scanning area, or whether each image magnification provides a desired size.

Abstract: An image forming apparatus maintains a constant beam scanning state so that light beams scan each drum always in the same state once a desired color overlapping accuracy is obtained by controlling color registration in color image formation. This mechanism achieves constantly fine color overlapping without forming a test pattern several times or consuming toner unnecessarily. A beam passage switch is provided in a laser scanning system. Sensors provided near each photosensitive drum determine whether each light beam has scanned a certain portion with no inclination or a certain scanning area, or whether each image magnification provides a desired size.

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: 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: 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 trench is formed in an n+ type substrate in a vertical direction from a main surface of the substrate, and a p type layer is deposited in the trench to have a recess portion. An n+ type layer is embedded in the recess portion. Accordingly, the p type layer is formed, as a resistive element, into a U-shape with ends that are ended on the main surface of the substrate. The resistive element has a resistance length corresponding to a path of the U-shape.

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.