US 7,072,270 B2 · Method and device for detecting optical data and reading-writing apparatus for optical data

Abstract

Light from a light source is applied to a diffraction grating via a collimator lens. The light diffracted by the diffraction grating is applied to a polarization beam splitter. The light polarized by the polarization beam splitter at a given polarizing plane is transmitted and is applied to a recording surface of an optical disc via a ¼-wave plate and an objective lens. The light reflected from the recording surface of the optical disc is applied to the polarization beam splitter via the objective lens and the ¼-wave plate and is reflected by the polarization beam splitter toward a focusing lens. The light incident to the focusing lens is thereby condensed and is applied to a holographic element which diffracts the light and disposes the focal points of the ±1 diffraction orders to be offset from each other along the optical axis of the zeroth diffraction order with the focal point of the zeroth diffraction order being between the focal points of the ±1 diffraction orders. The diffracted light is applied to a photo-detector via an optical element, for example, a flat plate disposed to be inclined with respect to the optical axis, for increasing the diameter of the diffracted light in a given direction.

Claims12

Dependent claims

A method for detecting optical data by applying light from a light source to a recording medium and detecting by a photo-detector the light which has been reflected by the recording medium and which carries data from the recording medium, the method comprising the steps of:

diffracting the reflected light into ±1 diffraction orders and zeroth diffraction order so as to dispose the focal points of the ±1 diffraction orders to be offset from each other along the optical axis of the zeroth diffraction order with the focal point of the zeroth diffraction order being between the focal points of the ±1 diffraction orders;
detecting the zeroth diffraction order by the photo-detector by increasing the diameter of the zeroth diffraction order in a direction substantially perpendicular to the direction of a track of the recording medium;
and
detecting the ±1 diffraction orders by the photo-detector, the ±1 diffraction orders forming circular light spots on the photo-detector.

1 more element

An optical-data-detecting device for applying light from a light source to a recording medium and detecting the light which has been reflected by the recording medium and which carries data from the recording medium, the optical-data-detecting device comprising:

a holographic element for diffracting the light reflected by the recording medium into ±1 diffraction orders and zeroth diffraction order and disposing the focal points of the ±1 diffraction orders to be offset from each other along the optical axis of the zeroth diffraction order with the focal point of the zeroth diffraction order being between the focal points of the ±1 diffraction orders;
a photo-detector disposed at the diffraction light-emission side of the holographic element, for detecting the ±1 diffraction orders and the zeroth diffraction order;
and
an optical element laminated on a light-receiving surface of the photo-detector, for applying the zeroth diffraction order to the photo-detector while increasing the diameter of the zeroth diffraction order in a direction substantially perpendicular to the direction of a track of the recording medium, and applying the ±1 diffraction orders to the photo-detector so that the ±1 diffraction orders form circular light spots on the photo-detector.

1 more element

A reading-writing apparatus for reading and writing optical data, comprising:

a light source;
driving means for driving a recording medium for rotation;
an optical head for applying light from the light source to the rotating recording medium via an objective lens which is movably supported and detecting by a photo-detector via the objective lens the light which has been reflected by the recording medium and which carries data from a data-recording surface of the recording medium, the optical head comprising:
a holographic element for diffracting the light reflected by the recording medium into ±1 diffraction orders and zeroth diffraction order and disposing the focal points of the ±1 diffraction orders to be offset from each other along the optical axis of the zeroth diffraction order with the focal point of the zeroth diffraction order being between the focal points of the ±1 diffraction orders;
a photo-detector disposed at the diffraction light-emission side of the holographic element, for detecting the ±1 diffraction orders and the zeroth diffraction order;
and
an optical element laminated on a light-receiving surface of the photo-detector, for applying the zeroth diffraction order to the photo-detector while increasing the diameter of the zeroth diffraction order in a direction substantially perpendicular to the direction of a track of the recording medium, and applying the ±1 diffraction orders to the photo-detector so that the ±1 diffraction orders form circular light spots on the photo-detector;
a signal-processing circuit for forming a read signal in accordance with a detection signal outputted from the photo-detector;
and
a servo control circuit for moving the objective lens in accordance with the detection signal outputted from the photo-detector.

7 more elements

Dependencies are inferred from the claim text.

Method and device for detecting optical data and reading-writing apparatus for optical data

Life of this patent

Method and device for detecting optical data and reading-writing apparatus for optical data

Life of this patent

Abstract

Claims12