Phase varying device, and optical pickup apparatus using the same for magneto-optical storage

Claim 2

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 1, wherein said phase change means comprises a 1/2-wavelength plate (15), said plate including two division regions (15a, 15b) obtained by division into at least two on a flat plane orthogonal to said light axis (O-O') facing across said light axis as a boundary and having planes of vibration at predetermined angles relative to said light axis, having C axes with respect to said light axis defined as a C₁ axis and a C₂ axis, and said plate being arranged so that the emitted light from said laser beam source (11) passes through one division region and the reflection light reflected at the recording surface (1a) of said magneto-optic recording medium (1) passes through another division region.

Claim 3

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 2, wherein said light detection element (16) is divided into a plurality of regions with said light axis (O-O') as a center corresponding to the division of said 1/2-wavelength plate (15).

Claim 4

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 3, wherein said light detection element (16) has four division regions not having a detection portion in the portion corresponding to said light axis (O-O').

Claim 5

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 4, wherein a magneto-optic (MO) recording signal recorded in said magneto-optic recording medium is detected from the detection signals of the four division regions of said light detection element (16).

Claim 6

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 5, wherein an astigmatic optical system such as a condenser lens (17), cylindrical lens (18), etc. is provided between said light detection element (16) and said polarization beam splitter (14).

Claim 7

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 2, wherein said 1/2-wavelength plate (15) is face-adhered to the surface of said polarization beam splitter (14) on said objective lens (13) side.

Claim 8

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 3, wherein, as said light detection element (16), a light detection element (19) having a large light receiving surface area is face-adhered to the surface of said polarization beam splitter (14) orthogonal to the surface to which said 1/2-wavelength plate (15) is adhered.

Claim 9

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 8, wherein said laser beam source (11) is a hologram laser unit equipped with a focus error detection function.

Claim 10

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 6, wherein a collimate lens (12) collimating the beam from said laser beam source to a parallel beam is provided between said laser beam source (11) and said polarization beam splitter (14).

Claim 11

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 2, wherein, as the aforesaid polarization beam splitter (14), use is made of a polarization beam splitter (14A) in which the phase difference between the polarized P wave component and the polarized S wave component is almost 0°.

Claim 12

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 2, wherein: the angles of the vibration planes in said two division regions (15a, 15b) of said 1/2-wavelength plate (15) are made different and a light detection element (16A) in which the light receiving plane is not divided is used as said light detection element (16).

Claim 13

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 1, wherein the light detection element (16A) in which the light receiving plane is not divided is an avalanche photodiode.

Claim 14

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 2, wherein said optical pickup apparatus for a magneto-optic storage device comprises: a laser coupler (20) which includes a microprism (23) having a plane (23a) with a predetermined inclination angle and having a first parallel plane reflecting the light incident through said plane at the first position and a second parallel plane parallel to said first parallel plane at which the light reflected at said first position is further reflected and is constituted so that the light reflected at the second parallel plane is further reflected to the second position of the first parallel plane; two light detection elements (24, 25) provided corresponding to said first position and second position of said first parallel plane, and each having three division regions obtained by division into three, i.e., a center portion (24b, 25b) and two side portions (24a:24c, 25a:25c) thereof; and a laser beam source (22) provided so as to face said inclination plane of said microprism (23), said microprism, said two light detection element and said laser beam source being integrally constituted on the same semiconductor substrate (21); a first mirror (31) provided on the side at which the light from said laser beam source (22) incident upon the inclination plane of said microprism (23) is reflected; a second mirror (32) which faces the reflection plane of said first mirror (31), receives the reflection light from said first mirror, and emits the same to the orthogonal direction; and a 1/2-wavelength plate (34) which has two division regions (34a, 34b), for dividing the emitted light of said second mirror (32) to at least two, which face each other with said light axis as a boundary on a plane orthogonal to said light axis (O-O'), have planes of vibration of predetermined angles, and have C axes with respect to said light axis defined as a C₁ axis and C₂ axis, and which is arranged so that the emitted light from said second mirror (32) passes through one division region and the reflection light reflected at the recording surface (1a) of said magneto-optic recording medium (1) passes through another division region.

Claim 15

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 14, wherein: provision is further made of two differential amplifiers (26, 27) which detect the differential signals from the three division regions of each of said two light detection elements (24, 25) and a third differential amplifier (28) which further differential-amplifies the output signals of these differential amplifiers.

Claim 16

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 15, wherein an objective lens (33) is provided between said 1/2-wavelength plate (34) and said magneto-optic disk (1).

Claim 17

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 2, wherein: a polarization beam splitter (14A) in which the phase difference between the polarized P wave component and the polarized S wave component is almost 0° is used as said polarization beam splitter; said 1/2-wavelength plate (15) is face-adhered to the surface of said polarization beam splitter (14A) on the side of said objective lens (13); and a light detection element (19) having a laser light receiving surface area is face-adhered to the surface of said polarization beam splitter (14A) orthogonal to the surface to which said 1/2-wavelength plate (15) is face-adhered.

Claim 18

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 17, wherein: the angles of said planes of vibration in two division regions (15a, 15b) of said 1/2-wavelength plate (15) are made different and a light detection element (16A) in which the light receiving plane is not divided is used as said light detection element.

Claim 19

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 18, wherein said light detection element (16A) in which the light receiving plane is not divided is an avalanche photodiode.

Claim 20

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 2, which has: a laser beam source (11); an objective lens (13) which converges the emitted light from said laser beam source and irradiates the same onto the recording surface (1a) of the magneto-optic recording medium (1); a polarization beam splitter (14) which is arranged between the above-described laser beam source and the objective lens and splits the predetermined polarized beam component in the reflection light reflected at the recording surface of the above-described magneto-optic recording medium; a 1/2-wavelength plate (15) which is arranged between said polarization beam splitter and said magneto-optic recording medium, has planes of vibration having predetermined angles in two division regions (15a, 15b) obtained by division into at least two on the plane orthogonal to the light axis, and has C axes of them with respect to said light axis defined as the C₁ axis and c₂ axis; and light detection elements (16, 16A) which detect the level of the predetermined polarized beam component split at the above-described polarization beam splitter, and wherein the reflection light in the emitted light from said laser beam source, passed through one region of said 1/2-wavelength plate, and reflected at the recording surface of said magneto-optic recording medium is made to pass through another region of said 1/2-wavelength plate.

Claim 21

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 2, wherein the angles of the planes of vibration of said two division regions are 45° and 22.5°, respectively.

Claim 22

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 1, wherein: said phase change means comprises a phase difference generation device including a 45 degree prism (40), and phase difference generating films (41, 41A, 41B) which have a plurality of division regions (41a:41b, 41aA:41bA, 41aB:41bB) which are coated on the reflection plane of said 45 degree prism, are obtained by division into at least two on the plane orthogonal to said light axis (O-O'), and have mutually predetermined phase difference characteristics and which are arranged so that the emitted light from said laser beam source (11) passes through one division region and the reflection light reflected at the recording surface (1a) of said magneto-optic recording medium (1) passes through another division region.

Claim 23

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 21, wherein the film thickness of said phase difference generating films (41, 41A, 41B) is adjusted to change said phase difference.

Claim 24

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 23, wherein: the number of said division regions is two and these two division regions are divided symmetrically relative to the diagonal line of said reflection plane (40a).

Claim 25

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 23, wherein: the number of said division regions is two and these two division regions are divided symmetrically vertically in said reflection plane (40a).

Claim 26

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 23, wherein: the number of said division regions is two and these two division regions are divided symmetrically horizontally in said reflection plane (40a).

Claim 27

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 22, wherein said light detection element (14) is divided corresponding to the division of said phase difference generating film.

Claim 28

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 27, wherein the magneto-optic recording signal recorded in said magneto-optic recording medium is detected from the detection signal of said light detection element.

Claim 29

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 28, wherein a condenser lens (17) and a cylindrical lens (18) are provided between said light detection element and said polarization beam splitter (14).

Claim 30

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 29, wherein, as said light detection element, a light detection element (19) having a large light receiving surface area is face-adhered to the surface of said polarization beam splitter (14) orthogonal to the side on which said phase difference generation device is arranged.

Claim 31

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 22, wherein said optical pickup apparatus for a magneto-optic storage device comprise: a laser coupler (20) which includes a microprism (23) having a plane (23a) with a predetermined inclination angle and having a first parallel plane reflecting the light incident through said plane at the first position and a second parallel plane parallel to said first parallel plane at which the light reflected at said first position is further reflected and is constituted so that the light reflected at the second parallel plane is further reflected to the second position of the first parallel plane; two light detection elements (24, 25) provided corresponding to said first position and second position of said first parallel plane, and each having three division regions obtained by division into three, i.e., a center portion (24b, 25b) and two side portions (24a:24c, 25a:25c) thereof, respectively; and a laser beam source (22) provided so as to face said inclination plane of said microprism (23), said microprism, said two light detection element and said laser beam source being integrally constituted on the same semiconductor substrate (21); a polarization beam splitter (14) provided on the side at which the light from said laser beam source (22) incident upon the inclination plane of said microprism (23) is reflected; said phase difference generation device (39) which is arranged on the light emission side of said phase polarization beam splitter; a mirror (32) arranged on the light emission side of said phase difference generation device; and an objective lens (13) for guiding the emitted light of said mirror (32) to the recording surface (1a) of said magneto-optic disk (1).

Claim 32

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 22, which has: a laser beam source (11); an objective lens (13) which converges the emitted light from said laser beam source and irradiates the same onto the recording surface (1a) of the magneto-optic recording medium (1); a polarization beam splitter (14) which is arranged between said laser beam source and the objective lens and splits the predetermined polarized beam component in the reflection light reflected at the recording surface of said magneto-optic recording medium; and a phase difference generation device which is arranged between said polarization beam splitter and said magneto-optic recording medium, has a 45 degree prism (40) and phase difference generating films (41, 41A, 41B) which have a plurality of division regions having mutual predetermined phase difference characteristics (41a:41b, 41aA:41bA, 41aB:41bB) coated on the reflection plane of said 45 degree prism and obtained by division into at least two on the plane orthogonal to said light axis (O-O'), and which are arranged so that the emitted light from said laser beam source (11) passes through one division region and the reflection light reflected at the recording surface (1a) of said magneto-optic recording medium (1) passes through another division region; and light detection elements (16, 16A) detecting the level of the predetermined polarized beam component split at said polarization beam splitter, and wherein the reflection light in the emitted light from said laser beam source, passed through one region of said phase difference generation device and reflected at the recording surface of said magneto-optic recording medium, is made to pass through another region of said phase difference generation device.

Claim 33

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 1, wherein said phase change means comprises a combination optical rotating plate (52, 62, 72) which has division regions (52a:52b, 62a:62b, 72a:72b) obtained by division into at least two on the plane orthogonal to said light axis (O-O') and which are arranged so that the emitted light from said laser beam source (11) is passed through one region while right optical rotating or left optical rotating the same at exactly a predetermined angle, and the reflection light reflected at the recording surface of said magneto-optic recording medium is passed through another region while optical rotating the same in the inverse rotation direction to said rotation exactly at a predetermined angle.

Claim 34

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 33, wherein the optical rotation angle of said combination optical rotating plate is defined by the material and thickness of said combination optical rotating plate.

Claim 35

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 33, wherein said light detection element has a circuit which has a plurality of division regions corresponding to the division of said combination optical rotating plate, differentially computes the signals corresponding to the light receiving surface area detected in these division regions of the light detection element, and thereby detects the magneto-optic signal recorded in said magneto-optic recording medium.

Claim 36

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 35, wherein said combination optical rotating plate (52) and said detector (16) are integrally constituted on the facing planes of said polarization beam splitter (14).

Claim 37

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 33, wherein provision is made of an astigmatic optical system such as a condenser lens (17), cylindrical lens (18), etc. between said light detection element (16) and said polarization beam splitter (14).

Claim 38

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 33, wherein a collimate lens (12) collimating the beam from said laser beam source to a parallel beam is provided between said laser beam source (11) and said polarization beam splitter (14).

Claim 39

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 2, wherein: said optical pickup apparatus for a magneto-optic storage device has said integral type apparatus having a laser coupler (20) which includes a microprism (23) having a plane (23a) with a predetermined inclination angle and having a first parallel plane reflecting the light incident through said plane at a first position and a second parallel plane parallel to said first parallel plane at which the light reflected at said first position is further reflected, and constituted so that the light reflected at a second parallel plane is further reflected to a second position of the first parallel plane; two light detection elements (24, 25) provided corresponding to said first position and second position of said first parallel plane, each having three division regions obtained by division into three, i.e., a center portion (24b, 25b) and two side portions (24a:24c, 25a:25c) thereof, respectively; and a laser beam source (22) provided so as to face said inclination plane of said microprism (23) said microprism, said two light detection elements and said laser beam source being integrally formed on the same semiconductor substrate (21), and a polarization beam splitter (14) provided on the side at which the light from said laser beam source (22) incident upon the inclination plane of said microprism (23) is reflected; a mirror (32) which is arranged on said combination rotating plate (52) of said integral type apparatus so as to face each other; and an objective lens (13) which guides the emitted light of said mirror (32) to the recording surface (1a) of said magneto-optic disk.

Claim 40

An optical pickup apparatus for a magneto-optic storage device comprising: a laser beam source (11); an objective lens (13) which converges the emitted light from said laser beam source and irradiates the same onto the recording surface (1a) of the magneto-optic recording medium (1); a polarization beam splitter (14) which is arranged between the above-described laser beam source and the objective lens and splits the predetermined polarized beam component in the reflection light reflected at the recording surface of the above-described magneto-optic recording medium; a combination optical rotating plate (52, 62, 72) which is arranged between said polarization beam splitter and the above described magneto-optic recording medium, has division regions (52a:52b, 62a:62b, 72a:72b) obtained by division into at least two on the plane orthogonal to the light axis (O-O'), and is arranged so that the emitted light from said laser beam source (11) is passed through one side region while right optical rotating or left optical rotating the same exactly at a predetermined angle, and the reflection light reflected at the recording surface of the above-described magneto-optic recording medium is passed through the other side region while rotating the same in the inverse rotation direction to the above-described rotation exactly at a predetermined angle; and light detection elements (16, 16A) which detect the level of the predetermined polarized beam component split at the above-described polarization beam splitter, and wherein the reflection light in the emitted light from said laser beam source, passed through one region of said combination rotating plate and reflected at the recording surface of said magneto-optic recording medium, is made to pass through another region of said combination rotating plate (52).

Claim 41

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 33 or 40, wherein: said combination optical rotating plates (52, 62 and 72) are divided by a line parallel to the pit-forming direction of the recording surface (1a) of said magneto-optic disk (1) and the optical rotation angles of said divisional left optical rotating plate (52a, 62a, 72a) and the optical rotation angles of the right optical rotating plate (52b, 62b, 72b) are set to predetermined values, so that said phase change characteristics are adjusted.

Claim 42

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 33 or 40, wherein: said-combination optical rotating plate (52, 62 and 72) is divided by a line orthogonal to the pit-forming direction of the recording surface (1a) of said magneto-optic disk (1) and the optical rotation angle of said divisional left optical rotating plate (52a, 62a, 72a) and the optical rotation angle of the divisional right optical rotating plate (52b, 62b, 72b) are set to predetermined values, so that said phase change characteristics are adjusted.

Claim 43

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 41 or 42, wherein the optical rotation angle of said combination optical rotating plate is set to about 10° or more.

Claim 44

An optical pickup apparatus for a magneto-optic storage device as set forth in claim 43, wherein the optical rotation angle of said combination optical rotating plate is set to 22.5°.

Claim 45

A phase difference generation device comprising: a 45 degree prism (40); and a plurality of division regions (41a:41b, 41aA:41bA, 41aB:41bB) coated on the reflection plane (40a) of said 45 degree prism, obtained by division into at least two on the plane orthogonal to the light axis (O-O'), and having mutually predetermined phase difference characteristics, and wherein the predetermined phase difference being produced between the light incident upon one division region and the light emission from another region.

Claim 46

A phase difference generation device as set forth in claim 45, wherein said phase difference is adjusted by changing the film thickness of a material forming said division regions.

Claim 47

A phase difference generation device as set forth in claim 46, wherein said division region is symmetrically divided relative to the diagonal line of said reflection plane (40a).

Claim 48

A phase difference generation device as set forth in claim 46, wherein said division region is divided symmetrically vertically in said reflection plane (40a).

Claim 49

A phase difference generation device as set forth in claim 46, wherein said division region is divided symmetrically horizontally in said reflection plane (40a).

Claim 50

A combination optical rotating plate comprising regions (52a, 52b) obtained by division into at least two on a plane orthogonal to the light axis (O-O') and, formed so that the light incident upon one region is passed while right optical rotating or left optical rotating the same exactly at a predetermined angle, and the light incident upon another region is passed while optical rotating the same in the inverse rotation direction to said rotation exactly at a predetermined angle.

Claim 51

A combination rotating plate as set forth in claim 50, wherein the optical rotation angle of said optical rotating plate is defined by the material and thickness of said combination optical rotating plate.

Claim 52

A combination rotating plate as set forth in claim 51, wherein the materials constituting said division regions are end face-adhered when they have a predetermined thickness, and they are polished to a thickness giving the desired optical rotation angle, whereby said combination optical rotating plate is formed.

Claim 53

A combination optical rotating plate as set forth in claim 50, wherein: said combination optical rotating plate (52, 62, 72) is divided in a predetermined orientation and the optical rotation angle of the divisional optical rotating plate is set to a predetermined value, to thereby adjust said phase change characteristics.