 Polarizing plate and liquid-crystal display containing the same |
| What is claimed is: 1. A polarizing plate comprising: a protective film, 5 to 150 μm thick, ... |
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| Polarization independent wavelength tunable filter based on birefringence compensation |
| It is an object of the present invention to provide a tunable, polarization independent wavelength ... |
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| Wavelength division multiplexer and demultiplexer |
| This invention is based on the observation that many filters have the characteristic property that ... |
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| Tunable filtering device for optical communications |
| To solve the above problems, it is an objective of the present invention to provide a tunable ... |
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| Wavelength selection switches for optical application |
| This invention is based on the observation that, by making use of filters that selectively passes ... |
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| All-optical holographic code division multiple access switch |
| These shortcomings and other limitations and deficiencies are obviated in accordance with the ... |
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| Method and apparatus for displaying three-dimensional images |
| What is claimed is: 1. A method for producing a three-dimensional image, comprising the steps of: ... |
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Optical head
| Details |
Inventors: Takahashi, Jun-ichi;
Assignee: NEC Corporation (JP)
Primary Examiner: Ben; Loha
Assistant Examiner:
Attorney, Agent or Firm: Ostrolenk, Faber, Gerb & Soffen, LLP
A light radiated from a light source is focused to provide a light spot on an optical disc. A central portion of the radiated light is shielded, and a peripheral portion of the radiated light is modulated to have an intensity decreasing in an outer periphery direction, respectively, by a light intensity modulator. Consequently, a diameter of the light spot is reduced, and side-lobes are suppressed. In place of the light intensity modulator, a light source filter and a second filter are used. A secondary light source is formed by focusing the radiated light. At a point of the secondary light source, the light source filter having a central portion of 0% and a peripheral portion of 100%, respectively, in light transmission intensity is provided. On an output side of a collimator lens, the second filter having central portion of 100% and a peripheral portion of 0%, respectively, in light transmission intensity is provided. |
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DETAILED DESCRIPTION Accordingly, it is an object of the invention to provide an optical head in which a diameter of a light spot formed on an optical head is smaller than a diffraction limitation for high density recordation and reproduction, while side-lobes are suppressed to increase a signal to noise ratio of the reproduced information.
It is a further object of the invention to provide an optical head in which the diameter reduction of a light spot formed on an optical disc is realized without dependency on a wavelength of a light beam and a numerical aperture on an objective lens.
According to the invention, an optical head, comprises: a light source for providing a radiated light beam; a collimator lens for collimating the radiated light beam to provide a collimated light; an objective lens for focusing the collimated light to form a light spot on an optical disc; a beam splitter for splitting a light beam reflected from the optical disc to first and second light beams; means for converting the first and second light beams to first and second electric signals; a light source filter for converting an intensity distribution of the radiated light beams to an intensity distribution of a disc having a circular aperture to provide an intensity distribution-converted light which is supplied to the collimator lens as the radiated light beam; and a second filter for converting an intensity distribution of the intensity distribution of the distribution-converted light dependently on the intensity distribution-converted light, the second filter being positioned at an output stage of the collimator.
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Optical Systems 
