Abstract: A multi-beam scanning optical system includes a light source having a plurality of light-emission points, an incident optical system for guiding a plurality of light beams emitted from the light source to a deflector, a scanning optical system for forming the plurality of light beams reflected/deflected by the deflector into images on a scanned surface, and a synchronization detection device in which a part of the plurality of light beams from the deflector are reflected at a predetermined angle in a sub-scanning cross-section by using a mirror to be scanned on a surface of a slit member and to be guided to a surface of a synchronization detection element via the slit member, and a timing at a scanning start position on the scanned surface is controlled by using a signal from the synchronization detection element. The slit member is positioned such that a plurality of light beams scanned on a surface of a slit opening are substantially vertically scanned on the slit opening.

Abstract: This specification discloses a plate-like polarizing element for converting light into polarized light having a plurality of units arranged along a common plane across the light, each of the units being provided with dividing means for dividing the light into reflected light and transmitted light whose planes of polarization are orthogonal to each other, varying means for varying the polarized state of at least one of the reflected light and the transmitted light to thereby make the planes of polarization of the two lights coincident with each other, and reflecting means for reflecting one of the reflected light and the transmitted light and directing it substantially in the same direction as the direction of travel of the other. The specification also discloses a polarizing conversion unit provided with such plate-like polarizing element, and a projector provided with such unit.

Abstract: An optical scanning device corrects a scanning line curvature and prevents image quality degradation, while spatially separating a plurality of light beams at oblique angles of incidence despite its compact magnifying optical scanning device construction. The optical scanning device directs, to the deflection surface of an optical deflector via a cylindrical lens, the plurality of light beams emitted by a light source having a plurality of light emission sections, guides, via an f.theta. lens system to a surface being scanned, the plurality of light beams deflected by the optical deflector so that the plurality of light beams scan the surface being scanned. The f.theta.

Abstract: A scanning optical system includes a light source, an optical deflector for deflecting a laser beam emitted from the light source, a first optical element for collimating the laser beam emitted from the light source into a parallel beam, a second optical element for focusing the parallel beam collimated by the first optical element to the optical deflector and making the parallel beam incident on the optical deflector, a third optical element for focusing the laser beam deflected by a deflection plane of the optical deflector onto a target irradiation surface. In a subscanning section of the scanning optical system, the following conditions are satisfied. An optical axis of the first optical element and an optical axis of the second optical element are parallelly decentered from each other. The second optical element and the third optical element are decentered from a central axis of the scanning optical system.

Abstract: The laser light source includes a laser light emitting device for emitting a plurality of laser light beams, a condenser lens for condensing the laser light beams, an interval adjusting unit for adjusting the interval between the laser light emitting device and the condenser lens, and a rotary adjustment unit for adjusting the laser light emitting device around a rotary axis perpendicular to the optical axis of the condenser lens. The rotary axis is positioned near light emission points of the laser light emitting device.

Abstract: In a scanning optical apparatus, a light beam emitted by a light source is caused to be obliquely incident on a deflection surface of an optical deflector in a sub scanning section through an optical device to form an image of the light beam deflectively reflected by the optical deflector on a surface to be scanned by an imaging optical system. A lateral magnification of the imaging optical system in a sub scanning direction is caused to change in accordance with a distance away from the on-axis to an off-axis along the main scanning direction.

Abstract: A scanning optical system includes a light source, an optical deflector for deflecting a laser beam emitted from the light source, a first optical element for collimating the laser beam emitted from the light source into a parallel beam, a second optical element for focusing the parallel beam collimated by the first optical element to the optical deflector and making the parallel beam incident on the optical deflector, a third optical element for focusing the laser beam deflected by a deflection plane of the optical deflector onto a target irradiation surface. In a subscanning section of the scanning optical system, the following conditions are satisfied. An optical axis of the first optical element and an optical axis of the second optical element are parallelly decentered from each other. The second optical element and the third optical element are decentered from a central axis of the scanning optical system.

Abstract: An error between a set value of magnification and an actual value of magnification is reduced by correcting the amounts of movement of a single-focus lens unit and a mirror in accordance with a production error in the focal length (in accordance with the lot number) of the single-focus lens unit.

Abstract: A method for producing a replica mirror for use in an image-forming apparatus is described. The process includes a step where a mirror base plate including a mirror surface inclined with respect to the scanning axis in the image-forming apparatus is prepared. A reflective film layer is adhered to a master plate via a releasing layer. Then an adhesive material is applied to the reflective film layer. The reflective film layer is adhered to the mirror base plate via the adhesive material by pressing the mirror base plate onto the adhesive material. The reflective film layer is then transferred to the mirror base plate by peeling off the releasing layer from the reflective film layer.

Abstract: This invention provides a projector capable of effectively utilizing the light from the light source and significantly reducing the light illuminating the outside of the area to be illuminated, thereby attaining an excellent efficiency of light utilization. In the illuminating system of the present invention provided with a light source and a reflector, there is further provided a circular reflector of a spherical surface, for returning the light, which emerges from the light source to the outside of the area to be illuminated, without being reflected on the reflector, to the light source. Also there is provided a flat mirror or a substantially spherical sub reflector for returning the light, which proceeds to the outside of the area to be illuminated, after being reflected on the reflector, to the light source. The sub reflector may be provided in the vicinity of the light source.

Abstract: An image-forming apparatus includes an image-forming unit for image-forming image information of an original on a record medium, an optical-path-length varying unit for varying a distance between an object and an image, a driving unit for driving the image-forming unit and the optical-path-length varying unit in an interlocking manner such that the image information of the original is formed on the record medium at a plurality of magnifications, and a control unit for controlling the driving unit. In the structure, the image-forming unit and the optical-path-length varying unit are mounted to the driving unit such that the positions of the image-forming unit and the optical-path-length varying unit are adjustable relative to the driving unit. An appropriate magnification is obtained even if a focal length of the fixed-focus image-forming lens fluctuates due to errors occurring during its manufacturing process.

Abstract: This invention provides a projector capable of effectively utilizing the light from the light source and significantly reducing the light illuminating the outside of the area to be illuminated, thereby attaining an excellent efficiency of light utilization. In the illuminating system of the present invention provided with a light source and a reflector, there is further provided a circular reflector of a spherical surface, for returning the light, which emerges from the light source to the outside of the area to be illuminated, without being reflected on the reflector, to the light source. Also there is provided a flat mirror or a substantially spherical sub reflector for returning the light, which proceeds to the outside of the area to be illuminated, after being reflected on the reflector, to the light source. The sub reflector may be provided in the vicinity of the light source.

Abstract: A projector comprising a light source having first and second high-luminance light emitting areas, an illuminating optical system for directing the light, from said light source, toward an object to be illuminated, wherein said first and second high-luminance light-emitting areas are positioned on the optical axis of said illuminating optical system, and a projection optical system for projecting the light emerging from said illuminated object, wherein said illuminating optical system is constructed in such a manner that a central area of said illuminated object is illuminated by most of the light beam from said first high-luminance light-emitting area, and a peripheral area of said illuminated object is illuminated by the remainder of the light beam from said first high-luminance light emitting area and most of the light from said second high-luminance light-emitting area.

Abstract: A synthetic silica glass powder obtained by calcining a silica gel powder obtained by hydrolysis of a tetraalkoxysilane, said synthetic silica glass powder containing from 1.times.10.sup.-1 to 1.times.10.sup.-4 ppm of boron and having an internal silanol group concentration of at most 150 ppm and an isolated silanol group concentration of at most 5 ppm.

Abstract: A polarizing conversion unit is disclosed. The unit is provided with a polarizing beam splitter for separating light from a light source into first and second polarized lights differing in polarized state from each other, polarizing conversion means for varying the polarized state of the first polarized light and making it substantially coincident with the polarized state of the second polarized light, and reflecting means for reflecting the first or second polarized light, at least a portion of that surface of the outer peripheral portion of the polarizing conversion unit which is parallel to the optical path of the light functioning as a reflection surface.

Abstract: This specification discloses a plate-like polarizing element for converting light into polarized light having a plurality of units arranged along a common plane across the light, each of the units being provided with dividing means for dividing the light into reflected light and transmitted light whose planes of polarization are orthogonal to each other, varying means for varying the polarized state of at least one of the reflected light and the transmitted light to thereby make the planes of polarization of the two lights coincident with each other, and reflecting means for reflecting one of the reflected light and the transmitted light and directing it substantially in the same direction as the direction of travel of the other. The specification also discloses a polarizing conversion unit provided with such plate-like polarizing element, and a projector provided with such unit.

Abstract: Synthetic quartz glass powder is produced by (a) hydrolyzing an alkoxysilane to form a gel, (b) finely dividing the gel and then drying, or drying the gel and then finely dividing, and (c) calcining the obtained powder, the powder being maintained under an atmosphere with an oxygen concentration of not less than 30 vol % during at least a part of the calcining period at a temperature of not lower than 1,000.degree. C.

Abstract: This specification discloses a polarization converting apparatus having means emitting non-polarized light, and polarizing means having a light incidence surface and a light emergence surface, the polarizing means receiving the non-polarized light by the light incidence surface and causing polarized light to emerge from the light emergence surface, the size and shape of the light incidence surface being similar to the size and cross-sectional shape of the non-polarized light. The specification also discloses an optical instrument having such apparatus.

Abstract: A polarization illumination apparatus is constituted by only a light source, light condensing means having a reflection mirror arranged behind the light source, polarization beam splitting means for splitting light emerging from the light condensing means into first and second polarized light components having different directions of polarization, and return means for returning the first polarized light component to the light condensing means. The direction of polarization of the first polarized light component is changed in such a manner that the first polarized light component from the return means is obliquely incident on and reflected by a mirror surface of the reflection mirror. Therefore, a polarization illumination apparatus which can modulate the vibration direction of polarized light without using an optical phase plate, and has high light utilization efficiency, and a projector using the apparatus can be realized.

Abstract: An image display apparatus has a radiation source, generator for generating an image by modulating a polarized light beam and directing device for directing a light beam from the radiation source toward the generator. The directing device has a conversion optical system for converting the beam from the radiation source into the polarized light beam. The conversion optical system has a polarizing beam splitter for splitting the beam from the radiation source into a first and second beams. In the conversion optical system, a 1/4 wavelength plate and a mirror are arranged so that the plane of polarization of the first beam is rotated to generate a third beam with the plane of polarization same as that of the second beam. The third beam is directed toward the generator through the polarizing beam splitter while the second beam is also directed toward the generator.