Abstract: A tracking signal and a focusing signal are stabilized by eliminating multi-layer crosstalk. The diffraction position, with respect to a semiconductor detector, from a center region of a multi-region diffraction grating disposed along the return path of reflection light from the layer of interest is placed further away from the optical axis than the diffraction position from a peripheral part of the diffraction grating. Stray light from other layers is thus prevented from being incident on a sensing region for a peripheral region of the diffraction grating. Further, the area of the semiconductor detector is reduced by dividing the center region.

Abstract: An optical pick-up which permits the relative position of a diffracting optical element and a photodetector to be adjusted by feedback control with signals which are generated when more than one kind of diffracted light differing in order is received, the diffracted light occurring as the reflected light from the optical disc is divided and diffracted by the diffracting optical element having multiple regions. The photodetector which detects the light beam passing through the central region of the diffracting optical element and generates RF signals is juxtaposed with sub-photodetectors, so that they receive reflected stray light from out-of-focus layers and perform computation to calculate the reflected stray light component which the RF signal detector receives, thereby detecting only the component of signals of the reflected light from a target layer.

Abstract: Provided is an optical pickup device capable of stabilizing a tracking signal and a focusing signal and of preventing quality deterioration of a data signal by eliminating a multi-layer crosstalk. Of reflected lights from a multi-layer disc, a reflected light from a target layer is split into two by a light flux splitting optical system so that the reflected light is spread out toward two directions with respect to a central line, and then the split lights are condensed. In this case, a reflected light from another layer does not reach a condensing position of the reflected light from the target layer, and only the reflected light from the target layer can be detected by a detector. Accordingly, a crosstalk from the another layer is eliminated.

Abstract: According to the present invention, of all beams of light reflected from the optical disc, only light in a peripheral region excluding a push-pull region is used to generate a DPD signal. In this method of signal generation that optimizes internal light-receiving surface interconnections in a photodetector, the lens error signal required for the generation of a tracking error signal in the DPP scheme is amplified at a lower amplification factor. In addition, the light reflected from the multilayered optical disc will be divided into a plurality of regions and the divided beam of light will be focused at different positions on the photodetector. When the beam is focused upon a desired layer, stray light from recording layers other than those to be subjected to information reproduction will not enter the photodetector light-receiving surfaces used for servo signals.

Abstract: When recording/reproducing an optical disc having a recording layer of multi-layer structure, an unwanted optical beam reflected from a recording layer other than a target layer for recording/reproduction is incident on a photodetector to cause an unwanted disturbance component to leak to a detection signal, giving rise to a degradation in the quality of a tracking control signal. In an optical pickup apparatus, for suppression of the degradation, an optical element is mounted having a diffraction area for diffracting part of the optical beam and light receiving planes for sub-optical beams are provided each of which has a light shielding zone or dead zone of a predetermined width on its central sectioning line.

Abstract: In an optical pickup capable of removing inter-layer crosstalk, a dark line that may appear in a central portion of a beam is removed. Thereby, an error in a data signal is reduced. Reflected light from a multi-layer disc is split into two parallel bundles with a splitting optical system in a way that the light is split at a central line. Thereby, when reflected light from a target layer is focused, the reflected light is not influenced from an attenuation element provided on an optical axis.

Abstract: An optical pickup device capable of eliminating interlayer crosstalk which is responsible for fluctuation in control signals and error rate in data signals, thereby ensuring stable action for a multilayered recording disc with a narrow interlayer spacing. The reflected beam coming from the multilayered disc is divided along the central line into two parallel portions by the dividing optical system and then condensed. The reflected beam coming from the active layer, which has been condensed, is reflected by the reflecting plane whose reflecting region is limited and the thus reflected beam is detected by the optical detector. The reflected beam coming from other layers is not reflected by the reflecting plane, so that interlayer crosstalk is reduced.

Abstract: To reduce a bad influence on a tracking control signal and a data signal by reflected light from an adjacent layer on a multi-layer disc as stray light, the following device is made in the invention. Reflected light from the multi-layer optical disc including stray light from another layer is once converged by a reflected light condenser lens and is reflected on a reflector. A grating which prevents zero-order light from being generated by setting groove depth to ?/4 and which is set to pitch to prevent positive and negative first- or higher-order diffracted lights from returning to the reflected light condenser lens is arranged between the lens and the reflector including an optical axis with the grating apart from the reflector. Hereby, as reflected light from another layer is cut off though reflected light from a corresponding layer is transmitted to a detector, a detected control signal and a detected data signal are not influenced by reflected light from another layer.

Abstract: Of the beams reflected by an optical disk, only peripheral beams excluding the push-pull region are used to generate a DPD signal in order to optimize internal wire connections among the light receiving areas of the optical detector and thereby reduce the amplification factor of the lens error signal, required for generating the tracking error signal of the DPP method. A beam reflected from a multilayered optical disk is divided into some beam diffraction areas. The divided beam diffraction areas and the light receiving areas are so arranged that the divided beams focus at different positions on the optical detector and that, when a beam is focused on a target recording layer of the disk, stray light from other than the target recording layer being reproduced does not enter into the servo signal light receiving area of the optical detector.

Abstract: An optical pick-up which permits the relative position of a diffracting optical element and a photodetector to be adjusted by feedback control with signals which are generated when more than one kind of diffracted light differing in order is received, the diffracted light occurring as the reflected light from the optical disc is divided and diffracted by the diffracting optical element having multiple regions. The photodetector which detects the light beam passing through the central region of the diffracting optical element and generates RF signals is juxtaposed with sub-photodetectors, so that they receive reflected stray light from out-of-focus layers and perform computation to calculate the reflected stray light component which the RF signal detector receives, thereby detecting only the component of signals of the reflected light from a target layer.

Abstract: When recording/reproducing an optical disc having a recording layer of multi-layer structure, an unwanted optical beam reflected from a recording layer other than a target layer for recording/reproduction is incident on a photodetector to cause an unwanted disturbance component to leak to a detection signal, giving rise to a degradation in the quality of a tracking control signal. In an optical pickup apparatus, for suppression of the degradation, an optical element is mounted having a diffraction area for diffracting part of the optical beam and light receiving planes for sub-optical beams are provided each of which has a light shielding zone or dead zone of a predetermined width on its central sectioning line.

Abstract: Provided is an optical pickup device capable of stabilizing a tracking signal and a focusing signal and of preventing quality deterioration of a data signal by eliminating a multi-layer crosstalk. Of reflected lights from a multi-layer disc, a reflected light from a target layer is split into two by a light flux splitting optical system so that the reflected light is spread out toward two directions with respect to a central line, and then the split lights are condensed. In this case, a reflected light from another layer does not reach a condensing position of the reflected light from the target layer, and only the reflected light from the target layer can be detected by a detector. Accordingly, a crosstalk from the another layer is eliminated.

Abstract: An optical pickup apparatus aiming at reduction of adverse effect on a tracking control signal and a data signal by preventing the reflected light from the adjacent layers of a multilayer disc changing to a stray light. In this optical pickup apparatus, the reflected light from the optical disc including the stray light from the adjacent layer is once focused with a focusing lens and is then reflected with the reflection plate. A flat attenuation element is provided between the lens and the reflection plate parallel to the optical axis with inclusion of the optical axis under the condition separated from the reflection plate. The reflection plate reflects the reflected light from the relevant layer and the attenuation element shields the reflected light from the adjacent layer. The light returning to the focusing lens includes less influence of the stray light. This light is detected with a detector to become a control signal and a data signal.

Abstract: In an optical pickup capable of removing inter-layer crosstalk, a dark line that may appear in a central portion of a beam is removed. Thereby, an error in a data signal is reduced. Reflected light from a multi-layer disc is split into two parallel bundles with a splitting optical system in a way that the light is split at a central line. Thereby, when reflected light from a target layer is focused, the reflected light is not influenced from an attenuation element provided on an optical axis.

Abstract: The adverse influence of reflected light from adjacent layers as stray light on a control signal or data signal is reduced when tracking a multilayered optical disc using differential push-pull method. The reflected light from the optical disc including stray light from an adjacent layer is once condensed with a condenser lens having little aberration and is then reflected by a reflecting mirror having a partial reflecting region. The resultant reflected light, which has the influence of stray light reduced, passes through a polarization beam splitter and becomes incident on a four-quadrant detector (for main beam) and a split detector (for sub beam) via a condenser lens having astigmatic aberration.

Abstract: The amount of reflected light from an adjacent layer in a multilayer optical disc is reduced by means of a combination of half-wave plates having different optical axes and a flat mirror. The polarization direction of the reflected light from a target layer is changed without changing the polarization direction of reflected light from the adjacent layer so as to detect a signal from the target layer alone. Because no stray light is introduced into the tracking error signal or focus signal, the laser light irradiated position can be controlled with high accuracy. This makes it possible to accurately determine the laser irradiated position during reading and writing, thereby enhancing signal quality. Because no reflected light from the adjacent layer is introduced into the data signal, a data signal with reduced error can be obtained.

Abstract: Influences of reflected light, which result in crosstalk from adjacent layers in a multi-layered optical disk, are mitigated. In an astigmatic optical system of an optical pickup, a first composite segmented wave plate having a segmentation direction that is in the same direction as the focal line that is close to the astigmatic optical system, a second composite segmented wave plate of the same segmentation direction, and an analyzer are inserted.

Abstract: In a multilayer optical recording medium having at least three recording layers, an influence of interlayer crosstalk due to an unnecessary light is removed. Each of the recording layers includes an information recording area, and the recording layers other than the nearest recording layer and the farthest recording layer when viewed from a light incident side include a first annular area having uneven patterns formed thereon, and a second annular area having uneven patterns formed thereon, the first annular area being adjacent to an inner side of the information recording area, the second annular area being adjacent to an outer side of the information recording area.

Abstract: To reduce a bad influence on a tracking control signal and a data signal by reflected light from an adjacent layer on a multi-layer disc as stray light, the following device is made in the invention. Reflected light from the multi-layer optical disc including stray light from another layer is once converged by a reflected light condenser lens and is reflected on a reflector. A grating which prevents zero-order light from being generated by setting groove depth to ?/4 and which is set to pitch to prevent positive and negative first- or higher-order diffracted lights from returning to the reflected light condenser lens is arranged between the lens and the reflector including an optical axis with the grating apart from the reflector. Hereby, as reflected light from another layer is cut off though reflected light from a corresponding layer is transmitted to a detector, a detected control signal and a detected data signal are not influenced by reflected light from another layer.

Abstract: An optical pickup apparatus aiming at reduction of adverse effect on a tracking control signal and a data signal by preventing the reflected light from the adjacent layers of a multilayer disc changing to a stray light. In this optical pickup apparatus, the reflected light from the optical disc including the stray light from the adjacent layer is once focused with a focusing lens and is then reflected with the reflection plate. A flat attenuation element is provided between the lens and the reflection plate parallel to the optical axis with inclusion of the optical axis under the condition separated from the reflection plate. The reflection plate reflects the reflected light from the relevant layer and the attenuation element shields the reflected light from the adjacent layer. The light returning to the focusing lens includes less influence of the stray light. This light is detected with a detector to become a control signal and a data signal.