Polarizing optical element and device using the same

Claim 2

A polarizing optical element (7) which comprises a first substrate (7a) having a first surface formed with first and second gratings (7c, 7d) so as to cross relative to each other at a predetermined crossing angle (T), each of said first and second gratings (7a, 7d) having a grating pitch (Λ) equal to or smaller than the wavelength of a laser beam (L1) which may be incident upon the polarizing optical element (7).

Claim 3

The polarizing optical element (11) as claimed in Claim 1, further comprising a generally plate-like semitransparent reflective layer (10).

Claim 4

The polarizing optical element (16) as claimed in Claim 1, further comprising a semitransparent reflective layer (10) overlaying the first and second gratings (7c, 7d) and a second substrate (15) having a smooth surface (15a) and an indented surface (15b) opposite to each other, said second substrate (15) being laminated over the semitransparent reflective layer (10) with the indented surface (15b) held in contact therewith, said indented surface (15b) of the second substrate (15) being in complemental relationship in shape to the first and second gratings (7c, 7d).

Claim 5

The polarizing optical element (14) as claimed in Claim 1, further comprising a light reflective layer (13) formed over the first and second gratings (7c,7d).

Claim 6

The polarizing optical element (11) as claimed in Claim 2, wherein the semitransparent reflective layer (10) has a reflectivity of 50% or lower relative to the amount of the incoming laser beam (L1).

Claim 7

The polarizing optical element (11) as claimed in Claim 2 or 5, further comprising a semitransparent reflective layer (10) deposited on a second surface of the substrate (7a) opposite to said first surface where the first and second gratings (7c, 7d) are formed.

Claim 8

The polarizing optical element (11) as claimed in Claim 2 or 5, further comprising a semitransparent reflective layer (10) deposited over the first surface of the substrate (7a), said first and second gratings (7c, 7d) being formed over the semitransparent reflective layer (10), said substrate (7a) having a second surface opposite to the first surface and having a non-reflective layer (12) deposited thereon.

Claim 9

The polarizing optical element (16) claimed in Claim 3, wherein material forming the first and second gratings (7c, 7d) and second substrate (15) have respective refractive indexes (N1, N2) which give a difference of 0.03 or smaller therebetween.

Claim 10

The polarizing optical element (16) as claimed in Claim 8, wherein material forming the first and second gratings (7c, 7d) and second substrate (15) are made of the same material.

Claim 11

The polarizing optical element (16) as claimed in Claim 3, 8 or 9, wherein the semitransparent reflective layer (10) has a light transmissivity within the range of 1 to 50% relative to the incoming laser beam (L1).

Claim 12

The polarizing optical element (7) as claimed in any of Claims 1 to 10, wherein the K vector angle (Tk) formed between two K vectors (kc, kd) on the first surface in a direction perpendicular to the first and second gratings (7c, 7d) is selected to be within the range of 70° to 110° in terms of the projection angle (2α) formed by projecting the K vector angle (Tk) onto a plane perpendicular to the path (Z) of travel of the incoming laser beam (L1).

Claim 13

The polarizing optical element (7) as claimed in any of Claims 1 to 10, wherein the K vector angle (Tk) formed between two K vectors (kc, kd) on the first surface in a direction perpendicular to the first and second gratings (7c, 7d) is selected to be within the range of 84° to 96° in terms of the projection angle (2α) formed by projecting the K vector angle (Tk) onto a plane perpendicular to the path (Z) of travel of the incoming laser beam (L1).

Claim 14

The polarizing optical element (7) as claimed in any of Claims 1 to 10, wherein the K vector angle (Tk) formed between two K vectors (kc, kd) on the first surface in a direction perpendicular to the first and second gratings (7c, 7d) is selected to be within the range of 10° to 20° in terms of the projection angle (2α) formed by projecting the K vector angle (Tk) onto a plane perpendicular to the path (Z) of travel of the incoming laser beam (L1).

Claim 15

A polarization analyzing device which comprises: a polarizing optical element (7; 11) comprising a substrate (7a) having a first surface formed with first and second gratings (7c, 7d) so as to cross relative to each other at a predetermined crossing angle (T), each of said first and second gratings (7c, 7d) having a grating pitch (Λ) equal to or smaller than the wavelength of a laser beam (L1) which may be incident upon the polarizing optical element (7; 11), said polarizing optical element (7; 11) being operable to produce two transmitted and diffracted laser beams (L2, L3) when the incoming laser beam (L1) is incident upon the first and second gratings (7c, 7d) of the polarizing optical element (7; 11); and a differential detector means (32) operable to detect the difference between the two transmitted and diffracted laser beams (L2, L3) thereby to provide an indication of a polarized condition of the incident laser beam (L1).

Claim 16

A polarization analyzing device which comprises: a polarizing optical element (7; 11) comprising a substrate (7a) having a first surface formed with first and second gratings (7c, 7d) so as to cross relative to each other at a predetermined crossing angle (T), each of said first and second gratings (7c, 7d) having a grating pitch (Λ) equal to or smaller than the wavelength of a laser beam (L1) which may be incident upon the polarizing optical element (7; 11), said polarizing optical element (7; 11) being operable to produce two transmitted and diffracted laser beams (L2, L3) when the incoming laser beam (L1) is incident upon the first and second gratings (7c, 7d) of the polarizing optical element (7; 11); and a differential detector means (32) operable to detect the difference between the two transmitted and diffracted laser beams (L2, L3) thereby to provide an indication of a polarized condition of the incident laser beam (L1).

Claim 17

A polarization analyzing device which comprises: a polarizing optical element (14; 16) comprising a substrate (7a) having a first surface formed with first and second gratings (7c, 7d) so as to cross relative to each other at a predetermined crossing angle (T), each of said first and second gratings (7c, 7d) have a grating pitch (Λ) equal to or smaller than the wavelength of a laser beam (L1) which may be incident upon the polarizing optical element (14; 16), and a semitransparent reflective layer (10) or a light reflective layer (12) formed over the first and second gratings (7c, 7d), said polarizing optical element (14; 16) being operable to produce two reflected and diffracted laser beams (L12, L13) when the incoming laser beam (L1) is incident upon the first and second gratings (7c, 7d) of the polarizing optical element (14; 16); and a differential detector means (32) operable to detect the difference between the two reflected and diffracted laser beams (L12, L13) thereby to provide an indication of a polarized condition of the incident laser beam (L1).

Claim 18

A polarization analyzing device which comprises: a polarizing optical element (14; 16) comprising a substrate (7a) having a first surface formed with first and second gratings (7c, 7d) so as to cross relative to each other at a predetermined crossing angle (T), each of said first and second gratings (7c, 7d) have a grating pitch (Λ) equal to or smaller than the wavelength of a laser beam (L1) which may be incident upon the polarizing optical element (14; 16), and a semitransparent reflective layer (10) or a light reflective layer (12) formed over the first and second gratings (7c, 7d), said polarizing optical element (14; 16) being operable to produce two reflected and diffracted laser beams (L12, L13) when the incoming laser beam (L1) is incident upon the first and second gratings (7c, 7d) of the polarizing optical element (14; 16); and a differential detector means (32) operable to detect the difference between the two reflected and diffracted laser beams (L12, L13) thereby to provide an indication of a polarized condition of the incident laser beam (L1).

Claim 19

A magneto-optical head system comprising a laser source (1) for emitting and projecting a laser beam (L ) on a magneto-optical recording medium (6) and utilizing a magneto-optical effect for reading information, recorded on the magneto-optical recording medium (6), by the utilization of reflected or transmitted laser beams (L1) reflected from or transmitted through the magneto-optical recording medium (6), which system comprises: a polarizing optical element (7) comprising a substrate (7a) having a surface formed with first and second gratings (7c, 7d) so as to cross relative to each other at a predetermined crossing angle (T), each of said first and second gratings (7c, 7d) having a grating pitch (Λ) equal to or smaller than the wavelength of a laser beam (L1) which may be incident upon the polarizing optical element (7), said polarizing optical element (7) being operable to produce a transmitted laser beam (L4) and two transmitted and diffracted laser beams (L2, L3) when the incoming laser beam (L1) reflected from or transmitted through the magneto-optical recording medium (6) is incident upon the first and second gratings (7c, 7d) of the polarizing optical element (7); a detector (31) responsive to the transmitted laser beam (L4) from the polarizing optical element (7) for detecting at least one of tracking and focusing conditions; and a differential detector (32) operable to detect the difference between the two transmitted and diffracted laser beams (L2, L3) thereby to read the information from the magneto-optical recording medium (6).

Claim 20

A magneto-optical head system comprising a laser source (1) for emitting and projecting a laser beam (L ) on a magneto-optical recording medium (6) and utilizing a magneto-optical effect for reading information, recorded on the magneto-optical recording medium (6), by the utilization of reflected or transmitted laser beams (L1) reflected from or transmitted through the magneto-optical recording medium (6), which system comprises: a polarizing optical element (7) comprising a substrate (7a) having a surface formed with first and second gratings (7c, 7d) so as to cross relative to each other at a predetermined crossing angle (T), each of said first and second gratings (7c, 7d) having a grating pitch (Λ) equal to or smaller than the wavelength of a laser beam (L1) which may be incident upon the polarizing optical element (7), said polarizing optical element (7) being operable to produce a transmitted laser beam (L4) and two transmitted and diffracted laser beams (L2, L3) when the incoming laser beam (L1) reflected from or transmitted through the magneto-optical recording medium (6) is incident upon the first and second gratings (7c, 7d) of the polarizing optical element (7); a detector (31) responsive to the transmitted laser beam (L4) from the polarizing optical element (7) for detecting at least one of tracking and focusing conditions; and a differential detector (32) operable to detect the difference between the two transmitted and diffracted laser beams (L2, L3) thereby to read the information from the magneto-optical recording medium (6).

Claim 21

A magneto-optical head system comprising a laser source (1) for emitting and projecting a laser beam (L1) on a magneto-optical recording medium (6) and utilizing a magneto-optical effect for reading information, recorded on the magneto-optical recording medium (6), by the utilization of reflected or transmitted laser beams (L1) reflected from or transmitted through the magneto-optical recording medium (6), which system comprises: a polarizing optical element (11) comprising a substrate (7a) having a surface formed with first and second gratings (7c, 7d) so as to cross relative to each other at a predetermined crossing angle (T), each of said first and second gratings (7c, 7d) having a grating pitch (Λ) equal to or smaller than the wavelength of a laser beam (L1) which may be incident upon the polarizing optical element (11), said polarizing optical element (11) being operable to produce a transmitted laser beam (L4), a reflected laser beam (L5) and two transmitted and diffracted laser beams (L2, L3) when the incoming laser beam (L1) reflected from or transmitted through the magneto-optical recording medium (6) is incident upon the first and second gratings (7c, 7d) of the polarizing optical element (11); a first error detector (33) responsive to the transmitted laser beam (L4) from the polarizing optical element (11) for detecting one of focusing and tracking conditions; a second error detector (34) responsive to the reflected laser beam (L5) from the polarizing optical element (11) for detecting the other of the focusing and tracking conditions; and a differential detector (32) operable to detect the difference between the two transmitted and diffracted laser beams (L2, L3) thereby to read the information from the magneto-optical recording medium (6).

Claim 22

A magneto-optical head system comprising a laser source (1) for emitting and projecting a laser beam (L1) on a magneto-optical recording medium (6) and utilizing a magneto-optical effect for reading information, recorded on the magneto-optical recording medium (6), by the utilization of reflected or transmitted laser beams (L1) reflected from or transmitted through the magneto-optical recording medium (6), which system comprises: a polarizing optical element (11) comprising a substrate (7a) having a surface formed with first and second gratings (7c, 7d) so as to cross relative to each other at a predetermined crossing angle (T), each of said first and second gratings (7c, 7d) having a grating pitch (Λ) equal to or smaller than the wavelength of a laser beam (L1) which may be incident upon the polarizing optical element (11), said polarizing optical element (11) being operable to produce a transmitted laser beam (L4), a reflected laser beam (L5) and two transmitted and diffracted laser beams (L2, L3) when the incoming laser beam (L1) reflected from or transmitted through the magneto-optical recording medium (6) is incident upon the first and second gratings (7c, 7d) of the polarizing optical element (11); a first error detector (33) responsive to the transmitted laser beam (L4) from the polarizing optical element (11) for detecting one of focusing and tracking conditions; a second error detector (34) responsive to the reflected laser beam (L5) from the polarizing optical element (11) for detecting the other of the focusing and tracking conditions; and a differential detector (32) operable to detect the difference between the two transmitted and diffracted laser beams (L2, L3) thereby to read the information from the magneto-optical recording medium (6).

Claim 23

The magneto-optical head system as claimed in Claim 17, wherein said polarizing optical element (11) further comprises a semitransparent reflective layer (10) and wherein said reflected laser beam (L5) is the one reflected from the semitransparent reflective layer (10).

Claim 24

The magneto-optical head system as claimed in Claim 17 or 18,wherein the reflected laser beam (L5) is reflected from the other surface (10A) of the substrate (7a) opposite to said surface where the first and second gratings (7c, 7d) are formed.

Claim 25

A magneto-optical head system comprising a laser source (1) for emitting and projecting a laser beam (L ) on a magneto-optical recording medium (6) and utilizing a magneto-optical effect for reading information, recorded on the magneto-optical recording medium (6), by the utilization of reflected or transmitted laser beams (L1) reflected from or transmitted through the magneto-optical recording medium (6), which system comprises: a polarizing optical element (16) comprising a first substrate (7a) having a surface formed with first and second gratings (7c, 7d) so as to cross relative to each other at a predetermined crossing angle (T), each of said first and second gratings (7c, 7d) having a grating pitch (Λ) equal to or smaller than the wavelength of a laser beam (L1) which may be incident upon the polarizing optical element (16), a semitransparent reflective layer (10) formed so as to overlay the first and second gratings (7c, 7d), and a second substrate (15) having a smooth surface (15a) and an indented surface (15b) opposite to each other, said second substrate (15) being laminated over the semitransparent reflective layer (10) with the indented surface (15b) held in contact therewith, said indented surface (15b) of the second substrate (15) being in complemental relationship in shape to the first and second gratings (7c, 7d), said polarizing optical element (16) being operable to produce a transmitted laser beam (L14), a reflected laser beam (L15) and two reflected and diffracted laser beams (L12, L13) when the incoming laser beam (L1) reflected from or transmitted through the magneto-optical recording medium (6) is incident upon the polarizing optical element (16); a first error detector (33) responsive to the transmitted laser beam (L14) from the polarizing optical element (16) for detecting one of focusing and tracking conditions; a second error detector (34) responsive to the reflected laser beam (L15) from the polarizing optical element (16) for detecting the other of the focusing and tracking conditions; and a differential detector (32) operable to detect the difference between the two reflected and diffracted laser beams (L12, L13) thereby to read the information from the magneto-optical recording medium (6).

Claim 26

A magneto-optical head system comprising a laser source (1) for emitting and projecting a laser beam (L ) on a magneto-optical recording medium (6) and utilizing a magneto-optical effect for reading information, recorded on the magneto-optical recording medium (6), by the utilization of reflected or transmitted laser beams (L1) reflected from or transmitted through the magneto-optical recording medium (6), which system comprises: a polarizing optical element (16) comprising a first substrate (7a) having a surface formed with first and second gratings (7c, 7d) so as to cross relative to each other at a predetermined crossing angle (T), each of said first and second gratings (7c, 7d) having a grating pitch (Λ) equal to or smaller than the wavelength of a laser beam (L1) which may be incident upon the polarizing optical element (16), a semitransparent reflective layer (10) formed so as to overlay the first and second gratings (7c, 7d), and a second substrate (15) having a smooth surface (15a) and an indented surface (15b) opposite to each other, said second substrate (15) being laminated over the semitransparent reflective layer (10) with the indented surface (15b) held in contact therewith, said indented surface (15b) of the second substrate (15) being in complemental relationship in shape to the first and second gratings (7c, 7d), said polarizing optical element (16) being operable to produce a transmitted laser beam (L14), a reflected laser beam (L15) and two reflected and diffracted laser beams (L12, L13) when the incoming laser beam (L1) reflected from or transmitted through the magneto-optical recording medium (6) is incident upon the polarizing optical element (16); a first error detector (33) responsive to the transmitted laser beam (L14) from the polarizing optical element (16) for detecting one of focusing and tracking conditions; a second error detector (34) responsive to the reflected laser beam (L15) from the polarizing optical element (16) for detecting the other of the focusing and tracking conditions; and a differential detector (32) operable to detect the difference between the two reflected and diffracted laser beams (L12, L13) thereby to read the information from the magneto-optical recording medium (6).

Claim 27

A magneto-optical head system comprising a laser source (1) for emitting and projecting a laser beam (L1) on a magneto-optical recording medium (6) and utilizing a magneto-optical effect for reading information, recorded on the magneto-optical recording medium (6), by the utilization of reflected or transmitted laser beams (L1) reflected from or transmitted through the magneto-optical recording medium (6), which system comprises: a polarizing optical element (14) comprising a substrate (7a) having a surface formed with first and second gratings (7c, 7d) so as to cross relative to each other at a predetermined crossing angle (T), each of said first and second gratings (7c, 7d) having a grating pitch (Λ) equal to or smaller than the wavelength of a laser beam (L1) which may be incident upon the polarizing optical element (14), a light reflective layer (13) coated so as to overlay the first and second gratings (7c, 7d), said polarizing optical element (14) being operable to produce a reflected laser beam (L15) and two reflected and diffracted laser beams (L12, L13) when the incoming laser beam (L1) reflected from or transmitted through the magneto-optical recording medium (6) is incident upon the polarizing optical element (14); a detector (31) responsive to the reflected laser beam (L15) from the polarizing optical element (14) for detecting at least one of focusing and tracking conditions; and a differential detector (32) operable to detect the difference between the two reflected and diffracted laser beams (L12, L13) thereby to read the information from the magneto-optical recording medium (6).

Claim 28

A magneto-optical head system comprising a laser source (1) for emitting and projecting a laser beam (L1) on a magneto-optical recording medium (6) and utilizing a magneto-optical effect for reading information, recorded on the magneto-optical recording medium (6), by the utilization of reflected or transmitted laser beams (L1) reflected from or transmitted through the magneto-optical recording medium (6), which system comprises: a polarizing optical element (14) comprising a substrate (7a) having a surface formed with first and second gratings (7c, 7d) so as to cross relative to each other at a predetermined crossing angle (T), each of said first and second gratings (7c, 7d) having a grating pitch (Λ) equal to or smaller than the wavelength of a laser beam (L1) which may be incident upon the polarizing optical element (14), a light reflective layer (13) coated so as to overlay the first and second gratings (7c, 7d), said polarizing optical element (14) being operable to produce a reflected laser beam (L15) and two reflected and diffracted laser beams (L12, L13) when the incoming laser beam (L1) reflected from or transmitted through the magneto-optical recording medium (6) is incident upon the polarizing optical element (14); a detector (31) responsive to the reflected laser beam (L15) from the polarizing optical element (14) for detecting at least one of focusing and tracking conditions; and a differential detector (32) operable to detect the difference between the two reflected and diffracted laser beams (L12, L13) thereby to read the information from the magneto-optical recording medium (6).

Claim 29

The magneto-optical head system as claimed in any one of Claims 16 to 21, wherein the position of a polarizing plane of the incident laser beam (L1) is so selected as to be inclined at an angle of 5° or smaller relative to the axis (X) which divides into two equal part the projection angle (2α) formed by projecting the K vector angle (Tk), which is delimited between respective K vectors (kc, kd) of the first and second gratings (7c, 7d), on a plane perpendicular to the path (Z) of travel of the incoming laser beam (L1), or relative to the different axis (Y) which is rotated 90° from said axis (X) dividing the projection angle (2α)into the two equal parts.