892results about "Optical detectors" patented technology

An optical pickup apparatus having an irradiation optical system for condensing a light beam on a track of a recording plane and a photodetection optical system for guiding return light to a photodetector to detect a focal error includes a holographic lens provided in the optical path of the return light for outputting 0-th and ±1st order diffracted lights based on the return light; an optical element provided in front of or behind the holographic lens for providing astigmatism; photodetectors for receiving the 0-th and ±1st order diffracted lights; and servo-signal generating operation circuits connected to the photodetectors for generating a first and second focus error signals having a first and second capture ranges based on the output signal of the photodetector.

An information reading apparatus can detect the coupling state of the input light to a waveguide of a laminated recording medium in a simple manner, so as to enable to focus the input light on a target recording layer to access the information recorded in the target recording layer quickly. The apparatus is compact and is economical to produce. The apparatus has a light source for injecting a light on an input edge of a lamination recording section, assembled into the recording medium containing a lamination of recording layers. Each recording layer has data represented by scattering centers which diffract an input light generated by a converging lens. An input light directing device directs the light source and the converging lens as a unit to focus the input light on a desired location. An image recording device records an informational image generated by guided waves produced within a laminated waveguide. An optical power detector detects output light emitted from an output edge of a specific recording layer as well as scattered light generated from recording layers other than the specific recording layer. An optical power discrimination circuit determines whether an optical power detected by the optical power detector is associated with the output light or the scattered light. Data recorded in any specific recording layer can be accessed quickly and simply by focusing input light on a core layer of a multi-layered hologram recording data storage medium. Because the absolute positional information stored in the storage medium is minimized, data storage capacity of the storage medium is almost unaffected while making the apparatus compact and low cost.

In an optical information recording medium having at least two information layer, guide grooves for tracking or sample pits or information pits corresponding to information signals are formed on a surface of a first substrate. A first information layer formed by a thin film for reflecting a portion of a light beam made incident on the first substrate and permitting penetration of a portion of the light beam is formed on a surface of the first substrate. Guide grooves for tracking or information pits corresponding to information signals are formed on a surface of a second substrate. A second information layer having a reflectance higher than that of the first information layer is formed on a surface of the second substrate. Between the first information layer and the second information layer, there is formed a transparent separation layer for positioning the first information layer and the second information layer to be spaced a predetermined distance apart from each other.

The present invention aims to generate an offset-free tracking signal and to realize a stable tracking control even if an optical disc is a multi-layer disc having three or more layers.Light receiving portions of a main region light receiving portion group is arranged between a projection line of a third dividing line on a photodetector and a projection line of a fourth dividing line on the photodetector by stray lights from information layers adjacent to the one, on which a light beam is focused, out of a plurality of information layers. Further, light receiving portions of a subregion light receiving portion group is arranged between a projection line of a first dividing line on a photodetector and a projection line of a second dividing line on the photodetector by the stray lights from the information layers adjacent to the one, on which a light beam is focused, out of the plurality of information layers.

An optical pickup can be provided, the optical pickup being capable of recording and playback of a plurality of optical disks having different specs by using light beams of different wavelengths, and further being suitable for integrating the semiconductor lasers and light receiving elements into a single package, by including: first and second semiconductor lasers adjacently disposed; a three-beam diffraction grating for generating three beams for tracking control; a second hologram element for diffracting light of the second semiconductor laser to guide it to a photosensor; a complex polarization beam splitter (PBS) for reflecting only light from the first semiconductor laser; and a first hologram element for diffracting light of the first semiconductor laser to guide it to the photosensor.