Minolta Company, Ltd.

Keiji Ogoh

Nobuo Kanai

Jun Kohsaka

Kenji Takeshita

Yoshihiro Inagaki

Hiroshi Hiraguchi

Yasushi Nagasaka

Akiyoshi Hamada

Toshio Naiki

Hidenari Tachibe

Osamu Yamada

An image forming apparatus forms an image with a gradation by scanning an image carrying member with a light beam based on image data. The beam is generated by using a light beam generating element capable of independently varying the beam output and the beam diameter. The output of the beam generating element is controlled based on the gradation level (density level) of the image data and the diameter of the beam from the element is controlled based on the gradation level. In short, the output of the light beam generating element and the beam diameter are controlled individually. Therefore, the exposed area of the surface of the image carrying member can be controlled properly by controlling the beam diameter as well as the output of the light beam generating unit. As a result, there can be obtained an image forming apparatus having excellent gradation reproduction over all the density regions. In controlling the output of the light beam generating element, there are cases where a light emitting time per dot is controlled or the beam intensity is controlled, depending on the gradation level of image data.

Image forming apparatus with excellent gradation reproduction

A laser beam scanning optical apparatus which images and scans a laser beam emitted from a laser diode on a photo-sensitive drum through a focusing lens, a polygon mirror and an f.theta. lens. An SOS photosensor detects the scanned laser beam and generates a detection signal. The laser diode is controlled to perform pulse emission a specified time after the generation of the detection signal. The pulse beam is incident to a beam detector which adopts a knife edge method, and the amount of a focal shift is detected. The focusing lens is moved along the optical axis in accordance with the detected amount of a focal shift to correct the position of the image point.

Laser beam scanning optical apparatus

A multi-beam emitting device which splits a light beam emitted from a light source into a plurality of beams with a beam splitter to emit a plurality of beams. As the beam splitter, an optical waveguide type acoustooptic element or the like is used. A multi-beam emitting device according to the present invention has a beam splitter which drives an acoustooptic element with a plurality of electric signals with different frequencies applied thereto so as to deflect a light beam emitted from a light source and split the light beam into a plurality of beams, a signal generator which generates the electric signals with different frequencies which are used for the drive of the acoustooptic element, a modulating circuit which turns on and off the electric signals generated by the signal generater individually based on a data signal, an intensity control circuit which controls the light source to change the intensity of the light beam emitted therefrom. Another multi-beam emitting device has a beam splitter which deflects a light beam emitted from a light source and splits the light beam into an even number of beams, a shutting member which shuts out a half of the beams, a modulating circuit which controls the beam splitter so that the total quantity of light of the beams which are emergent from the beam splitter and not shut out by the shutting member and the beams which are emergent from the beam splitter and shut out by the shutting member will be constant. Further, in these multi-beam emitting devices, the deflecting position of the light beam and the beam waist position of the light beam are inside the optical waveguide type acoustooptic element at a specified distance from each other.

Multi-beam emitting device having an acoustooptic element

A laser beam scanning optical apparatus which has Moire fringes generating elements which is located near a position optically equivalent to a scanning surface and modulates a laser beam emitted from a laser source to generate Moire fringes. The Moire fringes generating elements comprises, for example, a first filter which has spatial grating and a second filter which has spatial grating which slants slightly with respect to the spatial grating of the first filter, the first filter and the second filter being arranged upstream and downstream respectively in an optical path. The laser beam scanning optical apparatus further has a light receiving element for receiving the Moire fringes generated by the Moire fringes generating elements. Focusing means for correcting a position of an image point of the laser beam is driven in accordance with an output of the light receiving element. For example, the light receiving element is a photoelectric element with a plurality of light receiving surfaces, each of which generates an electric signal in accordance with the laser beam incident thereto, and from a phase difference between the electric signals, the position of the image point is detected.

Laser beam scanning optical apparatus having means for generating moire

A laser beam scanning optical apparatus which has a laser source unit, a collimator lens, a cylindrical lens, a polygon mirror and a scanning lens with an f.theta. function. The collimator lens is a bifocal lens, and because of the bifocal collimator lens, a part of the laser beam is focused on a point before the surface of a photosensitive member, and another part of the laser beam is focused on a point after the surface of the photosensitive member. Also, the cylindrical lens can be a bifocal lens. In this case, even when the magnification ratio in the sub scanning direction is designed small, the focal length of the cylindrical lens does not have to be lengthened.

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Toyokawa, Japan

Keiji Ogoh