Mitsubishi Denki Kabushiki Kaisha

Mitsushige Kondou

Shinsuke Shikama

Eiichi Toide

Kazuo Okada

Natsuro Tsubouchi

Shiro Hine

Toshiaki Suhara

Keizo Kono

Kazuo Iwata

Hiroshi Nishihara

Kenjiro Kime

Nobumasa Egashira

In case that the light beam emitted from a light source mounted on a base element is focused to a spot light on a data storage media to write the data, when the light beam reflected from the data storage media to return to the light source is reflected from the base element and focused again on the data storage media, it becomes difficult to precisely read/write the data on the storage media. In order to resolve the above problem, a light beam treating means is provided in the base element to prevent the re-incident light beams from being reflected toward the data storage media and focused thereon.

Optical head apparatus

An optical IC-type head assembly for recording and for reading information on an optical disc, comprising a substrate, a light guiding layer comprising a dielectric thin film formed monolithically on the substrate, a laser oscillator for injecting the laser beam into the light guiding layer, a grating coupler for converging the laser beam on the optical disc, and a photo detector for receiving the beam reflected by the optical disc and coming out of the grating coupler. In one embodiment the substrate is made of material having cleavability. One side surface of the light guiding layer receiving the laser beam is a break surface formed by cleaving the substrate along the cleavage plane. The photo detector is disposed at the break surface of the light guiding layer. The substrate is preferably made of single crystal material. In another embodiment, a beam splitter is disposed between the laser oscillator and the grating coupler for splitting the reflected beam coming out of the grating coupler into two symmetrical beams. Each split beam forms an acute angle with respect to the optical axis of the reflected beam. The acute angle is preferably less than 30 degrees. The beam splitter may converge each of the split beams at a photo detecting element disposed between the laser oscillator and the grating coupler.

Method of producing optical head assembly

Optical head assembly with efficient light source coupling surface and

An optical signal reading device comprising a laser light source (101), an objective (107) slidable in the direction of the optical axis which is at right angles to the disc surface of a disc-like record carrier, a light detector (110) for receiving the reflected light coming from the disc surface via the objective, and a beam splitter (104) comprised of a single optical part disposed between the light source (101), light detector (110), and objective (107). The splitter has a pair of reflecting surfaces disposed approximately parallel to each other to ensure that the incident light from the light source (101) and the reflected light guided to the light detector (110) are parallel and opposite to each other.

Optical signal reading device

An automatic focusing device for controlling the position of the objective lens relative to the information recording medium is provided with an astigmatic optical system which receives the reflected light beam reflected by the information recording medium. The light receiving surface of a light detector included in the astigmatic optical system consists of a central light receiving section formed approximatley symmetrically with respect to two axes intersecting each other perpendicularly and having a constricted central portion, and two side light receiving sections formed approximately symmetrically with respect to those two axes and opposite to each other. The light reception signal given by the central light receiving section and the light reception signals given by the side light receiving sections are fed to a focal position detecting circuit which gives a signal corresponding to the deviation of the objective lens from the focused position, on the basis of the light reception signals given thereto.

Automatic focusing device

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Nagaokakyo, Japan

Mitsushige Kondou