Abstract: An optical scanning system has an image reading scanning system for emitting a first scanning beam of light to read an image of an object, an image forming scanning system for emitting a second scanning beam of light to form an image on a light receiving surface, and a light receiving element. Each of the first and second scanning beams is incident on the light receiving element when each of the first and second scanning beams is located at an end portion of a scanning area, and the first scanning beam and the second scanning beam have different optical characteristics. The optical scanning system also has a circuit for generating a horizontal synchronous signal for the image reading optical system and the image forming optical system, respectively, in accordance with light received by the light receiving element.

Abstract: A laser beam emitting device is provided for use, for example, in a laser beam printer. The device includes a single laser diode for emitting a laser beam having an output power level that is dependent on a driving current supplied to the laser diode. Two laser diode drivers are connected to the single laser diode and can be individually energized to drive the single laser diode to emit a laser beam that can have different output power levels. A selector is connected to the drivers for producing one of a plurality of selecting signals corresponding to the different output power levels, respectively, to select and energize one of the drivers.

Abstract: A laser driving circuit is provided for driving a laser diode, in which the intensity of the laser beam emitted by the laser diode depends upon the amount of electrical current flowing through the laser diode. The laser driving circuit includes a current source for generating an electrical current to flow through the laser diode, the electrical current being varied in accordance with the voltage applied to the current source. In the laser driving circuit, voltage is applied to the current source in accordance with the intensity of the laser beam emitted by the laser diode. A variable resistor member is further provided for varying the voltage applied to the current source and at least one fixed resistor member is selectively connected in parallel with the variable resistor member for dividing the voltage, varied by the variable resistor member, at a predetermined ratio.

Abstract: A column filter using bundles of long fibers is disclosed. The bundles of long fibers are fixed at their lower end portions but are free-standing at their upper end portions. The length of the fibers in the bundles may preferably be longer than 1,000 mm but shorter than 3,000 mm--especially longer than 2,000 mm but shorter than 3,000 mm. During operation, the bundles may be compressed to a height of 80-30%, generally 50-40% of their original height. A plurality of holders for the respective bundles of long fibers, each of said holders being formed of a cap and a tube communicating to each other, said cap defining orifices and said tube defining a slot through a side wall and opening at both upper and lower ends, may preferably be provided on a perforated plate arranged transversely in a lower interior part of the shell with the cap being located above the perforated plate and the tube being positioned below the perforated plate. The holders cover substantially all perforations of the perforated plate.

Abstract: A column filter using bundles of long fibers is disclosed. The bundles of long fibers are fixed at their lower end portions but are free-standing at their upper end portions. The length of the fibers in the bundles may preferably be longer than 1,000 mm but shorter than 3,000 mm--especially longer than 2,000 mm but shorter than 3,000 mm. During operation, the bundles may be compressed to a height of 80-30%, generally 50-40% of their original height. A plurality of holders for the respective bundles of long fibers, each of said holders being formed of a cap and a tube communicating to each other, said cap defining orifices and said tube defining a slot through a side wall and opening at both upper and lower ends, may preferably be provided on a perforated plate arranged transversely in a lower interior part of the shell with the cap being located above the perforated plate and the tube being positioned below the perforated plate. The holders cover substantially all perforations of the perforated plate.