US 6,618,116 B1 · Optical head device and a diffraction element suitable for the device, and a method of manufacturing the diffraction element and the optical head device

Abstract

In order to read out information even from an optical recording medium having birefringence, of a diffracting element comprising an optical material forming a diffraction grating 21 having a cross-sectional shape of projections and recesses, and another optical material 22 filled at least in the recesses of the diffraction grating 21, at least one of the above two types of optical materials 21 and 22 shows birefringence, and the other optical material 22 has a refractive index which is different from both the ordinary refractive index and the extraordinary refractive index of said one optical material 21 showing birefringence. Further, in order to obtain a diffracting element of polarization type having a high diffraction efficiency and a uniform distribution in the plane, an alignment treatment film 11 is formed on one of two substrates 2 facing each other, spacers 12 to hold the space constant, and liquid crystal to be a thin film 1 of polymer liquid crystal, are sandwiched between the substrates 2 facing each other, the liquid crystal is aligned and cured by irradiation with light to obtain the thin film 1 of polymer liquid crystal, then one substrate is taken off, a grating having a cross-sectional shape of projections and recesses is formed on the thin film 1 of polymer liquid crystal, and the projections and recesses are filled with an isotropic medium.

Claims16

Dependent claims

A diffracting element comprising:

a diffraction grating having a cross-sectional shape including projections and recesses, said projections being formed with an optical material and at least said recesses being filled with another optical material;
one of the optical materials showing a birefringence due to an extraordinary refractive index, and the other of the optical materials comprising an isotropic optical material;
said isotropic optical material having at least one refractive index which is different from both an ordinary refractive index of the optical material showing said birefringence and the extraordinary refractive index;
and
said diffracting element having a first order diffraction-efficiency for polarized light exiting through the diffraction grating which is at least 10% of a first order diffraction-efficiency for polarized light returning through the diffraction grating.

2 more elements

Dependencies are inferred from the claim text.

Optical head device and a diffraction element suitable for the device, and a method of manufacturing the diffraction element and the optical head device

Life of this patent

Optical head device and a diffraction element suitable for the device, and a method of manufacturing the diffraction element and the optical head device

Life of this patent

Abstract

Claims16