Kabushiki Kaisha Toshiba

Other

Sou Ishika

Akihiro Kasahara

Takashi Yoshizawa

Hideo Yamasaki

A DVD laser emits a first light beam, and a CD laser emits a second light beam. An optical diffraction element diffracts first and second reflected lights corresponding to the first and second light beams, respectively. An optical detection element detects the first and second reflected lights reflected from a polarizing beam splitter. The optical axes of the CD and DVD lasers are set to diverge from each other. Thus, reflected light components necessary for focusing and tracking of a CD and a DVD are all detected by a detection element.

Optical head and optical disk drive

A light detecting device includes an object leans for leading a light beam from a light source to a recording medium. The recording medium has a groove and a header portion formed by interrupting the groove. The light detecting device further includes a photo-detector for detecting the light beam reflected on the recording medium and led by the object lens to output a signal corresponding to intensity of the reflected light beam, the photo-detector including a light beam detecting surface in a specified shape to which a component of the reflected light beam diffracted by the header portion is not incident.

Light detecting device for receiving light from corresponding portions

An optical head device for irradiating a light beam onto a recording medium to optically reproduce information recorded on the recording medium, the device includes a light source for generating a light beam to project onto the recording medium, a detector for detecting the light beam reflected from the recording medium, and an optical system for leading the light beam from the light source to the recording medium along a first optical axis and leading the light beam reflected from the recording medium along the first optical axis to the detector. The device further includes a half mirror arranged between the optical system and the recording medium, for reflecting a part of the light beam led to the recording medium toward the optical system to lead the part of the light beam onto the detector. The half mirror is tilted at a prescribed angle against the first optical axis to lead the part of the light beam reflected along a second optical axis differ from the first optical axis to the detector.

An optical head having a rotating mirror

A light detection device includes a lens, a photodetector, positioned tilted at a prescribed angle to an incident beam axis, for detecting the incident beam which is incident passing through the lens, and a mask for shading a light reflected by the photo-detector to prevent from returning the reflected light in the direction of the incident beam.

Tilted light detection device for preventing undesirable retro-reflection

An optical head comprises a laser beam source, a photo-detector device for receiving a laser beam emitted from the laser beam source and reflected at a data recording medium, an optical system for sending the laser beam from the data recording medium to the photo-detector device, and a base member for fixing the photo-detector device and the optical system. The photo-detector device has a photo-detector element, a mount member on which the photo-detector element is mounted, a block for fixing one end of the mount member, a spring member for applying elastic force to the mount member, a screw member for moving the photo-detector element along one direction against elastic force of the spring member and fixing the element to an arbitrary position, and a hinge portion formed in the fixing end of the mount member.

Optical head

An optical disk apparatus has a light source, light focusing means for focusing the light beam to a recording film of an optical disk light reception means for receiving a reflected light beam from the recording film, and optical axis adjustment means arranged in an optical path between the light source and the light focusing means and for adjusting a dislocation of the optical axis of the light beam from the optical center axis of the light focusing means. The optical axis adjustment means has an light transmissive flat plate having parallel surfaces which are installed diagonally to the optical axis, or with the light transmissive flat plate and means which supports the light transmissive flat plate and inclines rotatably the direction of the light transmissive flat plate around two axes by turning a curved surface seat thereof.

Optical disk apparatus

In an optical system, a light beam is converged on an optical disk and the light beam reflected from the optical disk passes through the objective lens and guided to a convex lens made of a refractive material having a first relatively large refractive index. The light beam is converged by the convex lens and divided by a half prism into a transmitted light beam and a reflected light beam. The reflected light beam is detected by a photodetector and converted into a tracking signal. The transmitted light beam is guided to a concave lens made of a refractive material having a second refractive index smaller than the first refractive index so that a divergent power is applied to the transmitted light beam from the concave lens. The converged light beam from the concave lens is detected by a photodetector and converted into a focusing signal. The objective lens is controlled in accordance with the focusing and tracking signals so that the objective lens is maintained in focusing and tracking states.

Focusing detection optical path for an optical information processing

An optical head in use with an optomagnetic disk apparatus employs a polarized beam splitter when information is recorded on and read out from a recording medium. In the optical head according to the present invention, the polarization plane of the polarized beam splitter is arranged so that it makes an angle of substantially 45.degree. with the polarization angle of the polarized laser beam entering the polarized beam splitter, whereby the optical head according to this invention does not use a 1/2 wavelength plate which is indispensable to the conventional optical head. In addition, the assembly and adjustment of the optical head according to the present invention are simplified.

Optical head in use with an optical recording/reproducing apparatus

A light beam emitted from a semiconductor laser is converged on a recording surface of an optical disk by a lens. The light beam is intensity-modulated and reflected in accordance with information recorded on the optical disk. The light beam is guided to a photodetector through a light beam diverging unit. The diverging unit is formed of first and second glass plates individually having parallel flat surfaces. A gap is formed between the first and second glass plates such that the glass plates are situated at substantially equal distances from the optical axis. The glass plates are oppositely tilted to the optical axis. The light beam is divided into three light beams by the first and second glass plates, the three light beams including first and second light beams and a third light beam which passes through the gap between the glass plates. The individual light beams separated by the light beam diverging device are guided to the photodetector, which has four detecting regions separated by separation lines. An output from the detecting regions irradiated with the first and second light beams is electrically processed to detect a focusing error, while an output from the detecting region irradiated with the third light beam is electrically processed to detect a tracking error. If a difference is detected between the outputs, in the focusing and tracking operation, correction signals corresponding to individual detection signals are supplied to a shifting device supporting the lens for movement, so that the lens is kept focused.

Apparatus for detecting and correcting focusing and tracking errors

In an optical information-processing apparatus, retrieving and recording laser beams are focused on an optical disk in a recording mode. The retrieving and recording laser beams are reflected from the optical disk and are transferred by the objective lens. The transferred retrieving laser beam is spatially separated from the transferred recording laser beam and is incident on the photo-sensitive region of a photodetector the edge of photo-sensitive region is so arranged as to be separated at distance d2 from the recording laser beam when the objective lens is in focusing state. The distance d2 satisfies the following inequality:

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Kawasaki, Japan

Sou Ishika