# US 2002/0172133 A1 · Reflection type compound prism and optical pickup apparatus employing the same

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- Number: US 2002/0172133 A1
- Document ID: US20020172133A1
- Status: Published application
- Kind: A1
- Application number: 10/078,459
- Filed: 2002-02-21
- Published: 2002-11-21
- Earliest claimed: 2001-04-30
- Assignees: Samsung Electronics Co., Ltd.
- Inventors: Dae-sik Kim; Seung-tae Jung; Cheol-sung Yeon; Kun-ho Cho
- Web page: https://patentgrep.com/patent/US20020172133A1

## CPC

- G11B 7/1356: Double or multiple prisms, i.e. having two or more prisms in cooperation
- G02B 5/04: Prisms
- G11B 7/12: Heads, e.g. forming of the optical beam spot or modulation of the optical beam (disposition or mounting of head elements within housing or with provision for moving of light source, optical beam or detector, irrelevant to the transducing method G11B7/08 {; modulating lasers H01S3/10; controlling the intensity, colour, phase, polarisation or direction of light beams arriving from an independent light source, e.g. switching gating or modulating G02F1/00})
- G11B 7/124: the integrated head arrangements including waveguides
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A reflection type compound prism and an optical pickup apparatus employing the same. As a light beam is passed through the compound prism, a size of the light beam in a direction perpendicular to a reference plane is reduced by a first reflection surface, propagated toward an objective lens by second and third reflection surfaces and the size restored by reflecting the light beam from a fourth reflection surface forming an angle less than 45° with respect to the reference plane so that a height of an optical system is reducible to obtain a small thin optical pickup with a desired NA. The second and third reflection surfaces are spaced apart in a direction perpendicular to the reference plane by an amount close to a diameter of the light beam at a point of incidence of the light beam with the compound prism.

## Claims

### Claim 1

A reflection type compound prism comprising:
a plurality of prisms which:
propagate a light beam by using a difference in angles between surfaces of the prisms, and
control a size of the light beam by reflecting the propagated light beam in a predetermined direction using a surface forming an angle less than 45° with respect to a reference plane.

### Claim 2 (depends on 1)

The reflection type compound prism as claimed in claim 1, wherein the plurality of prisms comprise:
a first prism comprising a first surface which transmits the light beam and a second surface which reflects the light beam at an incline with respect to the reference plane; and
a second prism comprising:
third and fourth surfaces arranged spaced apart in the predetermined direction by a predetermined distance of about a diameter of the light beam incident on the first surface by which the light beam reflected by the first reflection surface is again reflected in order, and
a fifth surface which forms the angle less than 45° with respect to the reference plane and which further reflects the again reflected light beam in the predetermined direction.

### Claim 3 (depends on 2)

The reflection type compound prism as claimed in claim 2, wherein the fifth surface forms an angle in a range including 20° and 40° with respect to the reference plane.

### Claim 4 (depends on 2)

The reflection type compound prism as claimed in claim 2, wherein the third and fourth surfaces are parallel to each other.

### Claim 5 (depends on 2)

The reflection type compound prism as claimed in claim 2, wherein the second prism is a rhomboid prism comprising the third, fourth and fifth surfaces and a surface facing the fifth surface.

### Claim 6 (depends on 3)

The reflection type compound prism as claimed in claim 3, wherein the second prism is a rhomboid prism comprising the third, fourth and fifth surfaces and a surface facing the fifth surface.

### Claim 7 (depends on 4)

The reflection type compound prism as claimed in claim 4, wherein the second prism is a rhomboid prism comprising the third, fourth and fifth surfaces and a surface facing the fifth surface.

### Claim 8 (depends on 2)

The reflection type compound prism as claimed in claim 2, further comprising a third prism disposed between the first and second prisms to make the light beam reflected by the second surface proceed straight to the second prism.

### Claim 9 (depends on 8)

The reflection type compound prism as claimed in claim 8, wherein the third prism is a triangle prism having a right triangle structure.

### Claim 10 (depends on 2)

The reflection type compound prism as claimed in claim 2, wherein the first prism is a triangle prism having an isosceles triangle structure arranged to be inclined by a predetermined angle with respect to the reference plane.

### Claim 11 (depends on 2)

The reflection type compound prism as claimed in claim 2, wherein the first and second prisms are formed and arranged so that total internal reflection of the light beam occurs at the second, third and fourth surfaces.

### Claim 12 (depends on 5)

The reflection type compound prism as claimed in claim 5, wherein the first and second prisms are formed and arranged so that total internal reflection of the light beam occurs at the second, third and fourth of the plurality of surfaces.

### Claim 13 (depends on 8)

The reflection type compound prism as claimed in claim 8, wherein the first and second prisms are formed and arranged so that total internal reflection of the light beam occurs at the second, third and fourth surfaces.

### Claim 14 (depends on 2)

The reflection type compound prism as claimed in claim 2, wherein the fifth surface is a total reflection surface.

### Claim 15 (depends on 10)

The reflection type compound prism as claimed in claim 10, wherein the fifth surface is a total reflection surface.

### Claim 16

A reflection type compound prism comprising:
a first prism having an isosceles triangle structure which is arranged to be inclined with respect to a reference plane; and
a second prism having a rhomboidal structure and a surface forming an angle less than 45° with respect to the reference plane.

### Claim 17 (depends on 16)

The reflection type compound prism as claimed in claim 16, further comprising a third prism having a triangle structure arranged between the first prism and the second prism so that a light beam from the first prism proceeds straight to the second prism.

### Claim 18 (depends on 17)

The reflection type compound prism as claimed in claim 17, wherein the third prism has a right triangle structure.

### Claim 19 (depends on 16)

The reflection type compound prism as claimed in claim 16, wherein at least one surface in the first prism and at least one surface in the second prism, are formed and arranged to produce total internal reflection of a light beam.

### Claim 20 (depends on 16)

The reflection type compound prism as claimed in claim 16, wherein the second prism has a pair of parallel surfaces which are spaced apart in a predetermined direction perpendicular to the reference plane.

### Claim 21 (depends on 19)

The reflection type compound prism as claimed in claim 19, wherein the second prism has a pair of parallel surfaces which are spaced apart in a predetermined direction perpendicular to the reference plane.

### Claim 22

An optical pickup apparatus comprising:
a light source which emits a light beam;
an objective lens which condenses light to form a light spot on a recording surface of a recording medium;
an actuator which drives the objective lens in focus and/or track directions;
a reflection type compound prism which:
reduces a size of the emitted light beam with respect to a first direction which is perpendicular to a reference plane by using a difference in angles between surfaces of the prism,
propagates the reduced size light beam adjacent the actuator, and
reflects the light beam in the first direction toward the objective lens using a surface forming an angle less than 45° with respect to the reference plane; and
a photodetector which photoelectrically converts the light beam reflected by the recording medium and passed through the objective lens and the reflection type compound prism.

### Claim 23 (depends on 22)

The apparatus as claimed in claim 22, wherein the reflection type compound prism comprises:
a first prism comprising a first transmission surface which transmits the light beam and a first reflection surface which reflects the light beam so that the light beam is inclined with respect to the reference plane; and
a second prism comprising second and third reflection surfaces, spaced apart a distance of about a diameter of the light beam at the first transmission surface, which reflect the light beam to a fourth reflection surface forming an angle less than 45° with respect to the reference plane by which the light beam is reflected in the first direction toward the objective lens.

### Claim 24 (depends on 23)

The apparatus as claimed in claim 23, wherein the fourth reflection surface forms an angle in the range including 20° and 40° with respect to the reference plane.

### Claim 25 (depends on 23)

The apparatus as claimed in claim 23, wherein the second and third reflection surfaces are parallel to each other.

### Claim 26 (depends on 23)

The apparatus as claimed in claim 23, wherein the second prism is a rhomboid prism in which the second, third and fourth reflection surfaces and a surface facing the fourth reflection surface form a rhomboidal structure.

### Claim 27 (depends on 23)

The apparatus as claimed in claim 23, wherein the reflection type compound prism further comprises a third prism disposed between the first and second prisms to make a light beam reflected by the first reflection surface proceed straight into the second prism.

### Claim 28 (depends on 27)

The apparatus as claimed in claim 27, wherein the third prism is a triangle prism having a right triangle structure.

### Claim 29 (depends on 23)

The apparatus as claimed in claim 23, wherein the first prism is a triangle prism having an isosceles triangle structure arranged to be inclined by a predetermined angle with respect to the reference plane.

### Claim 30 (depends on 23)

The apparatus as claimed in claim 23, wherein the first and second prisms are formed and arranged so that total internal reflection of the light beam occurs at the first, second and third reflection surfaces.

### Claim 31 (depends on 23)

The apparatus as claimed in claim 23, wherein the fourth reflection surface is a total reflection surface.

### Claim 32 (depends on 22)

The apparatus as claimed in claim 22, wherein the reflection type compound prism comprises:
a first prism having an isosceles triangle structure which is arranged to be inclined with respect to the reference plane; and
a second prism having a rhomboidal structure and a surface forming an angle less than 45° with respect to the reference plane.

### Claim 33 (depends on 32)

The apparatus as claimed in claim 32, wherein the reflection type compound prism further comprises a third prism having a triangle triangle structure arranged between the first prism and the second prism so that the light beam proceeds straight from the first triangle prism into the second prism.

### Claim 34 (depends on 33)

The apparatus as claimed in claim 33, wherein the third prism has a right triangle structure.

### Claim 35 (depends on 32)

The apparatus as claimed in claim 32, wherein in the first prism and the second prism, at least one surface is formed and arranged to produce total internal reflection of the light beam.

### Claim 36 (depends on 32)

The apparatus as claimed in claim 32, wherein:
the second prism comprises a pair of parallel surfaces which are arranged spaced apart in a predetermined direction perpendicular to the reference plane by an amount close to a diameter of the light beam at an incident surface of the first prism.

### Claim 37 (depends on 35)

The apparatus as claimed in claim 35, wherein:
the second prism comprises a pair of parallel surfaces which are arranged spaced apart in a predetermined direction perpendicular to the reference plane by an amount close to a diameter of the light beam at an incident surface of the first prism.

### Claim 38 (depends on 22)

The apparatus as claimed in claim 22, wherein the recording medium has a structure in which data is recorded on and/or reproduced from the recording medium in a reflection surface recording method.

### Claim 39 (depends on 23)

The apparatus as claimed in claim 23, wherein the recording medium has a structure in which data is recorded on and/or reproduced from the recording medium in a reflection surface recording method.

### Claim 40 (depends on 32)

The apparatus as claimed in claim 32, wherein the recording medium has a structure in which data is recorded on and/or reproduced from the recording medium in a reflection surface recording method.

### Claim 41 (depends on 22)

The apparatus as claimed in claim 22, wherein at least a portion of the objective lens is disposed closer to the reference plane than a portion of the light beam at an incident surface of the reflection type compound prism.

### Claim 42 (depends on 23)

The apparatus as claimed in claim 23, wherein at least a portion of the objective lens is disposed closer to the reference plane than a portion of the light beam at the first transmission surface.

### Claim 43 (depends on 32)

The apparatus as claimed in claim 32, wherein at least a portion of the objective lens is disposed closer to the reference plane than a portion of the light beam at an incident surface of the reflection type compound prism.

### Claim 44 (depends on 22)

The apparatus as claimed in claim 22, further comprising an optical path changer, provided on an optical path between the light source and the reflection type compound prism, which changes a proceeding path of the light beam.

### Claim 45 (depends on 44)

The apparatus as claimed in claim 44, wherein the optical path changer comprises:
a polarizing beam splitter which one of transmits and reflects an incident light beam according to a polarization of the incident light beam; and
a wave plate which changes the polarization of the incident light beam.

### Claim 46 (depends on 44)

The apparatus as claimed in claim 44, wherein the optical path changer comprises a hologram element which selectively transmits or diffracts and transmits an incident light beam according to a direction of incidence, and the light source, the hologram element, and the photodetector are optically modularized.

### Claim 47

An optical pickup for recording/reproducing a signal to/from a recording medium, the optical pickup comprising:
a light source which emits a light beam; and
a reflection type compound prism, which communicates the light beam toward the optical recording medium, the reflection type compound prism comprising:
a first surface which transmits the light beam,
a second surface which reflects the transmitted light beam to be inclined with respect to a reference plane and reduces a size of the transmitted light beam in a direction perpendicular to the reference plane,
third and fourth surfaces disposed parallel to the reference plane and which propagate the reduced size light beam by total internal reflection, and
a fifth surface which reflects the propagated reduced size light beam toward the optical recording medium and adjusts a size of the propagated reduced size light beam.

### Claim 48 (depends on 47)

The optical pickup as claimed in claim 47, wherein the fifth surface adjusts the size of the propagated reduced size light beam to a size corresponding to a diameter of the light beam at the first surface.

### Claim 49 (depends on 47)

The optical pickup as claimed in claim 47, wherein the fifth surface reflects the adjusted size light beam through the fourth surface and in a direction perpendicular to the reference plane.

### Claim 50 (depends on 49)

The optical pickup as claimed in claim 49, wherein the fifth surface is disposed with respect to the reference plane at an angle in a range including 20 and 40 degrees.

### Claim 51 (depends on 47)

The optical pickup as claimed in claim 47, further comprising an objective lens, disposed between the fourth surface and the optical recording medium.

### Claim 52 (depends on 47)

The optical pickup as claimed in claim 47, wherein a portion of the first surface is closer to the optical recording medium than the fourth surface.

### Claim 53 (depends on 47)

The optical pickup as claimed in claim 47, further comprising:
a photodetector which photoelectrically converts a light beam returned from the recording medium;
wherein the reflection type compound prism communicates the returned light beam toward the photodetector.

### Claim 54 (depends on 53)

The optical pickup of claim 53, further comprising a beam splitter which transmits the emitted light beam toward the reflection type compound prism and reflects the returned light beam to the photodetector according to respective polarizations of the emitted and returned light beams.

### Claim 55 (depends on 47)

The optical pickup of claim 47, wherein:
the first and second surfaces are surfaces of an isosceles triangle prism and the isosceles triangle prism further comprises a base surface,
the third, fourth and fifth surfaces are surfaces of a rhomboid prism, the rhomboid prism further comprising a sloped surface parallel to the fifth surface, and
the reflection type compound prism further comprises a right triangle prism which joins the base surface of the isosceles triangle prism with the sloped surface of the rhomboid prism.

### Claim 56 (depends on 55)

The optical pickup of claim 55, wherein:
the right triangle prism has a base surface, a height surface and a hypotenuse surface,
the height surface of the right triangle prism joins the base surface of the isosceles triangle prism, and
the hypotenuse surface of the right triangle prism joins the sloped surface of the rhomboid prism.

### Claim 57 (depends on 56)

The optical pickup of claim 56, wherein the base surface of the isosceles triangle prism makes an angle of about 60 degrees with the third surface.

### Claim 58 (depends on 56)

The optical pickup of claim 56, wherein the hypotenuse surface of the right triangle prism makes an angle of 30 degrees with the third surface.

### Claim 59 (depends on 54)

The optical pickup of claim 54, wherein the isosceles triangle prism is truncated in height for at least a portion of a width of the isosceles triangle prism.

### Claim 60

An optical pickup for recording/reproducing a signal to/from a recording medium, the optical pickup comprising:
a light source which emits a light beam; and
a compound prism, comprising:
a first surface,
a second surface, oriented at a first angle with respect to a first surface, which transmits the light beam,
a third surface oriented at a second angle with respect to the second surface and which reflects the light beam toward the first surface by total internal reflection,
a fourth surface, spaced apart from the first surface, which together with the first surface propagates the light beam by total internal reflection, and
a fifth surface, oriented at an angle in a range including 20 degrees and 40 degrees with respect to the first surface, which reflects the propagated light beam toward the optical recording medium.

### Claim 61 (depends on 60)

The optical pickup as claimed in claim 60, wherein the first and fourth surfaces are parallel.