CA2036412A1 - Optical head - Google Patents
Optical headInfo
- Publication number
- CA2036412A1 CA2036412A1 CA002036412A CA2036412A CA2036412A1 CA 2036412 A1 CA2036412 A1 CA 2036412A1 CA 002036412 A CA002036412 A CA 002036412A CA 2036412 A CA2036412 A CA 2036412A CA 2036412 A1 CA2036412 A1 CA 2036412A1
- Authority
- CA
- Canada
- Prior art keywords
- light
- optical disk
- reflecting
- optical head
- optical
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 230000003287 optical effect Effects 0.000 title claims abstract description 75
- 230000004907 flux Effects 0.000 description 12
- 238000010586 diagram Methods 0.000 description 6
- 241000543381 Cliftonia monophylla Species 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B7/1359—Single prisms
Landscapes
- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Head (AREA)
- Optical Recording Or Reproduction (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A separate-type optical head having a fixed unit equip-ped with a light source and a photo-detecting system separ-ated from a movable unit equipped with a light reflecting system which reflects and converts a light from the light source to be a light incident upon an optical disk perpend-icularly and returns the reflecting light from the optical disk to the fixed unit, wherein a prism having reflecting surfaces being at angles of 45° to each other is arranged for the reflecting system in the movable unit for reflecting the light from the light source so as to a light incident upon the optical disk perpendicularly even in the case where the movable unit inclines to the optical disk.
A separate-type optical head having a fixed unit equip-ped with a light source and a photo-detecting system separ-ated from a movable unit equipped with a light reflecting system which reflects and converts a light from the light source to be a light incident upon an optical disk perpend-icularly and returns the reflecting light from the optical disk to the fixed unit, wherein a prism having reflecting surfaces being at angles of 45° to each other is arranged for the reflecting system in the movable unit for reflecting the light from the light source so as to a light incident upon the optical disk perpendicularly even in the case where the movable unit inclines to the optical disk.
Description
2036~1~
TITI.E OF THE INVENTION
OPTICAL HEAD
BAC~GROUND OF THE INVENTION
Field of the Inven-tion This invention relates to an optical head for recording and reproducing information to an optical disk, more parti-cularly to a separate-type optical head wherein a fixed optical head unit comprising a light source and a photo-detecting system is separated from a movable op-tical head unit comprising a reflecting system and an objective lens system.
Description of Related Art Fig. 1 is a block diagram showing the structure of a conventional optical head of a separate type as disclosed, for example, in Japanese Utility Model Application Laid~pen No. 6~-31506. In Fig. 1, reference numeral 1 designates an optical disk, whose radial direction is taken as a base line 2. Reference numeral 3 designates a fixed unit, arranged at a fixed position, having a laser light source which projects a light in a direction parallel to the base line 2, and a photo-detecting system for detecting a reflecting light from the optical disk 1. A light projected from the laser ligh-t source of the fixed unit 3 is incident upon a slidably mov-able unit ~ driven in a direction parallel to the base line ' .
2~3~ 2 2. The movable unit 4 radiates this light from the fixed unit 3 to the optical disk 1. The optical disk 1 reflects the light from the movable unit 4 which in turn reflects the received light to the fixed unit 3.
The movable uni-t 4 is equipped with a reflecting mirror 4a and an objective lens 4b. The reflecting mirror 4a reflects the light from the laser li~ht source to the optic-al disk 1, and the reflecting light from the optical disk 1 to the fixed unit 3. The condenser lens 4b condenses the light reflected by -the reflecting mirror 4a onto the optical disk 1, and the reflecting light from the optical disk 1 onto the reflec-ting surface of the reflecting mirror 4a.
The operation of the above-described conventional optical head will be explained below. When a luminous flux from the laser light source of the fixed unit 3 enters the movable unit 4 in parallel with the base line 2, it is de-flected by the reflecting mirror 4a to be perpendicular to the surface of the optical disk 1. The luminous flux is then condensed to a point on the optical disk 1 by the ob-jective lens 4b.
The light reflected by the optical disk 1 is collected again by the objective lens 4b and returned to the fixed unit 3 along a reverse course of the aforementioned. The photo-detecting sys-tem in the fixed unit 3 detects a tra-cking error to the optical disk 1.
. .
,~ .
2~3~412 In the case where the movable unit 4 inclines at an an,gle~ towards the optical disk l as shown in Fig. 2, the luminous flux reflected by the reflecting mirror 4a inclines at twice the angle ~, i.e., 2~, and incident upon the surface of the optical disk l in this state. Therefore, the light returning from the optical disk l inclines as well.
The luminous flux returning from the movable unit 4 to the fixed unit 3 becomes not parallel to the base line 2, which causes a positional deviation of the luminous flux to the photo-detecting system in the fixed unit 3.
As a result, an offset is caused in a tracking error signal, inviting an adverse influence to the tracking cont-rol of the optical head. Particularly? in the case,of the separate-type optical head, the distance between the photo-detecting system in the fixed unit 3 and the reflecting mirror 4a of the movable unit 4 is greater, whereby the off-set considerably affects the optical head. Besides, the movable unit 4 may variously incline as it moves, which makes it difficult to correct the offset.
~UMMARY OF T~E INVENTION
This invention has been devised to solve the afore-mentioned problems encountered in the prior art.
An essential object of this invention is to provide an optical head capable of correctly detecting information of 2~36~ ~
tracking error from an optical disk at all -times, by de-flecting a light from a light source in a fixed unit to be incident upon the recordin~ surface of an optical disk per-pendicularly, and deflecting a reflecting light from -the optical disk to be in parallel with the optical disk even when a movable unit inclines to the optical disk.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a block diagram showing the structure of a conventional separate-type optical head;
Fig. 2 is an enlar~ed partial block diagram of a con-ventional separate-type optical head;
Fig. 3 is a block diagram showing the structure of a separate-type optical head according to this invention;
Fig. 4 is an enlarOed partial block diagram of the separate-type optical head according to this invention; and Fig. 5 is a diagram of an optical path explanatory of the operation of the inclined separate-type optical head according to this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
. .
`` 2~364~2 A separate-type optical head according to -this inven-tion will be discussed in detail hereinbelow with reference to Figs. 3 through 5 in which reference numeral 1 designa-tes an optical disk, whose radial direction is taken as a base line 2. Reference numeral 3 designates a fi~ed unit, ar-ranged at a fixed position, which is equipped with a laser light source for projecting a lioht in a direction parallel to the base line 2 and a photo-detecting system for detect-ing a reflecting light from the optical disk 1. A light projected from the laser ligh-t source of the foxed unit 3 is incident upon a slidably movable unit 4 driven in a parallel direction to the base line 2. The movable unit 4 radiates this light from the fixed unit 3 to the optical disk 1. The optical disk 1 reflects the light from the movable unit 4, and the movable unit 4 reflects the liaht from the optical disk 1 to the fixed unit 3.
The movable unit 4 is equipped with a prism 4A and an objective lens 4b. The prism 4A has reflecting surfaces 401, 402 being at angles of 45 to each other, which reflect the light from the laser light source towards the optical disk 1, and the light from the optical disk 1 towards the fixed unit 3. The objective lens 4b condenses the light from the laser light source reflected by the prism 4A onto the optical disk 1 and condenses also the reflecting light from the optical disk 1 onto the reflecting prism 4A.
. . .
203~12 The optical head having the above-described structure will operate in the manner as follows. When a luminous flux from the laser light source of the fixed unit 3 enters the movable unit 4, it is reflected by the reflecting surface 401 of the prism 4A and then the reflecting light is re-flected by the reflecting surface 402 which is at an angle of 45 to the former reflecting surface 401 so that the luminous flux is incident ~pon the optical disk 1 perpendi-cularly to the base line 2. The reflecting light from the prism 4A is condensed to a point on the optical disk 1 by the obJective lens 4b.
The light reflected from the optical disk 1 is con-densed again by -the objective lens 4b and returned to the fixed unit 3 along a reverse course of the above after it is reflected by the reflecting surfaces 401, 402 of the prism 4A. At this time, the photo-detecting system in the fixed unit 3 detects information of tracking errors to the optical disk 1.
Fig. 4 illustrates an optical path explanatory of the operation of the movable unit 4 when it inclines at an angle ~ to the base line 2. The luminous flux reflected by the prism 4A does not incline at all by being reflected from the reflecting surfaces 401, 402 to be incident upon the optical disk 1 perpendicularly. Likewise, the light returning from the optical disk 1 travels correctly along the reverse . . .
;
2036~12 course of the above reflecting light, so that the luminous flux returning from the movable unit 4 to the fixed unit 3 is always parallel to the base line 2.
Fig. 5 depicts an optical path explanatory of the pri-nciple of the optical head of this invention, wherein a broken line indicates an optical path when the movable unit 4 indicated by a solid line inclines at the angle ~. An angle a3 defined by the l~lminous flux from the laser light source to the prism ~r~ and the reflecting light from the prism 4A to the optical disk 1 is obtained as follows;
cl + c2 = 135 al = 180 - 2 cl a2 = 180 - 2 c2 al + a2 = 360 - 2~0 = 90 a3 = 180 - (al + a2) = 90 Even when the movable unit 4 inclines at angle ~, the following equations are held;
bl = al + 2 b2 = a2 - 2 ~
b3 = 180 - ( al + a2) = 90 Accordingly, the prism 4A reflects the luminous flux from the laser light source always in a perpendicular direc-tion to the optical disk 1.
As such, the luminous flux incident upon the photo-detecting system in the fixed unit 3 is free from the posi-203~412 tional deviation, without an offset in a -tracking error signal, thereby enabling stable tracing control.
As this invention may be embodied in several forms without departing from the spirit of essential characterist-ics thereof, the present embodiment is therefore illustrat-ive and not res-trictive, since the scope of the invention is defined by the appended claims rather than by the descrip-tion preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such me-tes and bounds thereof are therefore intended to be embraced by the claims.
, .. .. . . .. .
TITI.E OF THE INVENTION
OPTICAL HEAD
BAC~GROUND OF THE INVENTION
Field of the Inven-tion This invention relates to an optical head for recording and reproducing information to an optical disk, more parti-cularly to a separate-type optical head wherein a fixed optical head unit comprising a light source and a photo-detecting system is separated from a movable op-tical head unit comprising a reflecting system and an objective lens system.
Description of Related Art Fig. 1 is a block diagram showing the structure of a conventional optical head of a separate type as disclosed, for example, in Japanese Utility Model Application Laid~pen No. 6~-31506. In Fig. 1, reference numeral 1 designates an optical disk, whose radial direction is taken as a base line 2. Reference numeral 3 designates a fixed unit, arranged at a fixed position, having a laser light source which projects a light in a direction parallel to the base line 2, and a photo-detecting system for detecting a reflecting light from the optical disk 1. A light projected from the laser ligh-t source of the fixed unit 3 is incident upon a slidably mov-able unit ~ driven in a direction parallel to the base line ' .
2~3~ 2 2. The movable unit 4 radiates this light from the fixed unit 3 to the optical disk 1. The optical disk 1 reflects the light from the movable unit 4 which in turn reflects the received light to the fixed unit 3.
The movable uni-t 4 is equipped with a reflecting mirror 4a and an objective lens 4b. The reflecting mirror 4a reflects the light from the laser li~ht source to the optic-al disk 1, and the reflecting light from the optical disk 1 to the fixed unit 3. The condenser lens 4b condenses the light reflected by -the reflecting mirror 4a onto the optical disk 1, and the reflecting light from the optical disk 1 onto the reflec-ting surface of the reflecting mirror 4a.
The operation of the above-described conventional optical head will be explained below. When a luminous flux from the laser light source of the fixed unit 3 enters the movable unit 4 in parallel with the base line 2, it is de-flected by the reflecting mirror 4a to be perpendicular to the surface of the optical disk 1. The luminous flux is then condensed to a point on the optical disk 1 by the ob-jective lens 4b.
The light reflected by the optical disk 1 is collected again by the objective lens 4b and returned to the fixed unit 3 along a reverse course of the aforementioned. The photo-detecting sys-tem in the fixed unit 3 detects a tra-cking error to the optical disk 1.
. .
,~ .
2~3~412 In the case where the movable unit 4 inclines at an an,gle~ towards the optical disk l as shown in Fig. 2, the luminous flux reflected by the reflecting mirror 4a inclines at twice the angle ~, i.e., 2~, and incident upon the surface of the optical disk l in this state. Therefore, the light returning from the optical disk l inclines as well.
The luminous flux returning from the movable unit 4 to the fixed unit 3 becomes not parallel to the base line 2, which causes a positional deviation of the luminous flux to the photo-detecting system in the fixed unit 3.
As a result, an offset is caused in a tracking error signal, inviting an adverse influence to the tracking cont-rol of the optical head. Particularly? in the case,of the separate-type optical head, the distance between the photo-detecting system in the fixed unit 3 and the reflecting mirror 4a of the movable unit 4 is greater, whereby the off-set considerably affects the optical head. Besides, the movable unit 4 may variously incline as it moves, which makes it difficult to correct the offset.
~UMMARY OF T~E INVENTION
This invention has been devised to solve the afore-mentioned problems encountered in the prior art.
An essential object of this invention is to provide an optical head capable of correctly detecting information of 2~36~ ~
tracking error from an optical disk at all -times, by de-flecting a light from a light source in a fixed unit to be incident upon the recordin~ surface of an optical disk per-pendicularly, and deflecting a reflecting light from -the optical disk to be in parallel with the optical disk even when a movable unit inclines to the optical disk.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a block diagram showing the structure of a conventional separate-type optical head;
Fig. 2 is an enlar~ed partial block diagram of a con-ventional separate-type optical head;
Fig. 3 is a block diagram showing the structure of a separate-type optical head according to this invention;
Fig. 4 is an enlarOed partial block diagram of the separate-type optical head according to this invention; and Fig. 5 is a diagram of an optical path explanatory of the operation of the inclined separate-type optical head according to this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
. .
`` 2~364~2 A separate-type optical head according to -this inven-tion will be discussed in detail hereinbelow with reference to Figs. 3 through 5 in which reference numeral 1 designa-tes an optical disk, whose radial direction is taken as a base line 2. Reference numeral 3 designates a fi~ed unit, ar-ranged at a fixed position, which is equipped with a laser light source for projecting a lioht in a direction parallel to the base line 2 and a photo-detecting system for detect-ing a reflecting light from the optical disk 1. A light projected from the laser ligh-t source of the foxed unit 3 is incident upon a slidably movable unit 4 driven in a parallel direction to the base line 2. The movable unit 4 radiates this light from the fixed unit 3 to the optical disk 1. The optical disk 1 reflects the light from the movable unit 4, and the movable unit 4 reflects the liaht from the optical disk 1 to the fixed unit 3.
The movable unit 4 is equipped with a prism 4A and an objective lens 4b. The prism 4A has reflecting surfaces 401, 402 being at angles of 45 to each other, which reflect the light from the laser light source towards the optical disk 1, and the light from the optical disk 1 towards the fixed unit 3. The objective lens 4b condenses the light from the laser light source reflected by the prism 4A onto the optical disk 1 and condenses also the reflecting light from the optical disk 1 onto the reflecting prism 4A.
. . .
203~12 The optical head having the above-described structure will operate in the manner as follows. When a luminous flux from the laser light source of the fixed unit 3 enters the movable unit 4, it is reflected by the reflecting surface 401 of the prism 4A and then the reflecting light is re-flected by the reflecting surface 402 which is at an angle of 45 to the former reflecting surface 401 so that the luminous flux is incident ~pon the optical disk 1 perpendi-cularly to the base line 2. The reflecting light from the prism 4A is condensed to a point on the optical disk 1 by the obJective lens 4b.
The light reflected from the optical disk 1 is con-densed again by -the objective lens 4b and returned to the fixed unit 3 along a reverse course of the above after it is reflected by the reflecting surfaces 401, 402 of the prism 4A. At this time, the photo-detecting system in the fixed unit 3 detects information of tracking errors to the optical disk 1.
Fig. 4 illustrates an optical path explanatory of the operation of the movable unit 4 when it inclines at an angle ~ to the base line 2. The luminous flux reflected by the prism 4A does not incline at all by being reflected from the reflecting surfaces 401, 402 to be incident upon the optical disk 1 perpendicularly. Likewise, the light returning from the optical disk 1 travels correctly along the reverse . . .
;
2036~12 course of the above reflecting light, so that the luminous flux returning from the movable unit 4 to the fixed unit 3 is always parallel to the base line 2.
Fig. 5 depicts an optical path explanatory of the pri-nciple of the optical head of this invention, wherein a broken line indicates an optical path when the movable unit 4 indicated by a solid line inclines at the angle ~. An angle a3 defined by the l~lminous flux from the laser light source to the prism ~r~ and the reflecting light from the prism 4A to the optical disk 1 is obtained as follows;
cl + c2 = 135 al = 180 - 2 cl a2 = 180 - 2 c2 al + a2 = 360 - 2~0 = 90 a3 = 180 - (al + a2) = 90 Even when the movable unit 4 inclines at angle ~, the following equations are held;
bl = al + 2 b2 = a2 - 2 ~
b3 = 180 - ( al + a2) = 90 Accordingly, the prism 4A reflects the luminous flux from the laser light source always in a perpendicular direc-tion to the optical disk 1.
As such, the luminous flux incident upon the photo-detecting system in the fixed unit 3 is free from the posi-203~412 tional deviation, without an offset in a -tracking error signal, thereby enabling stable tracing control.
As this invention may be embodied in several forms without departing from the spirit of essential characterist-ics thereof, the present embodiment is therefore illustrat-ive and not res-trictive, since the scope of the invention is defined by the appended claims rather than by the descrip-tion preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such me-tes and bounds thereof are therefore intended to be embraced by the claims.
, .. .. . . .. .
Claims (2)
1. An optical head for recording/reproducing informa-tion to/from an optical disk comprising:
a fixed optical head unit provided at a fixed position, which has a light source projecting a light in a direction parallel to the recording surface of said optical disk and a photo-detecting system for detecting a reflecting light from said optical disk, and a movable optical head unit driven in a direction para-llel to the recording surface of said optical disk, which has a light reflecting system for reflecting and converting a light projected from said light source to a light incident upon the recording surface of said optical disk perpendi-cularly, and a condensing system for condensing the light reflected by said light reflecting system onto said optical disk, wherein said light reflecting system has two reflecting surfaces being at angles of 45° to each other.
a fixed optical head unit provided at a fixed position, which has a light source projecting a light in a direction parallel to the recording surface of said optical disk and a photo-detecting system for detecting a reflecting light from said optical disk, and a movable optical head unit driven in a direction para-llel to the recording surface of said optical disk, which has a light reflecting system for reflecting and converting a light projected from said light source to a light incident upon the recording surface of said optical disk perpendi-cularly, and a condensing system for condensing the light reflected by said light reflecting system onto said optical disk, wherein said light reflecting system has two reflecting surfaces being at angles of 45° to each other.
2. An optical head as set forth in Claim 1, wherein said light reflecting system is a prism having at least two reflecting surfaces being at angles of inclined 45° to each other.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2-15110 | 1990-01-26 | ||
| JP1990015110U JPH03106529U (en) | 1990-02-16 | 1990-02-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2036412A1 true CA2036412A1 (en) | 1991-08-17 |
Family
ID=11879693
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002036412A Abandoned CA2036412A1 (en) | 1990-02-16 | 1991-02-15 | Optical head |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPH03106529U (en) |
| CA (1) | CA2036412A1 (en) |
| DE (1) | DE4104779A1 (en) |
| FR (1) | FR2659479A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5311496A (en) * | 1992-11-13 | 1994-05-10 | Hyundai Electronics America | Achromatic expansion prism for magneto-optical drive |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6015829A (en) * | 1983-07-08 | 1985-01-26 | Canon Inc | Pickup of optical recorder |
| JPS60124035A (en) * | 1983-12-07 | 1985-07-02 | Canon Inc | Optical head device |
| JPS6448248A (en) * | 1987-08-17 | 1989-02-22 | Ricoh Kk | Optical pick-up device |
-
1990
- 1990-02-16 JP JP1990015110U patent/JPH03106529U/ja active Pending
-
1991
- 1991-02-13 DE DE4104779A patent/DE4104779A1/en not_active Ceased
- 1991-02-14 FR FR9101784A patent/FR2659479A1/en active Pending
- 1991-02-15 CA CA002036412A patent/CA2036412A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| JPH03106529U (en) | 1991-11-05 |
| DE4104779A1 (en) | 1991-08-29 |
| FR2659479A1 (en) | 1991-09-13 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |