JPH11339307A - Optical head device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact and inexpensive optical head device capable of compatibly reproducing plural optical disks of different kinds with one head device. SOLUTION: Light beams radiated from plural light sources 201, 202,..., 20n having different wavelengths are converted into luminous fluxes by a collimate lens 7 so as to be equal extension angles and made incident on a single mirror 11 having plural reflection surfaces having different curvature radiuses corresponding to the wavelengths of the light beams of the respective light sources. The respective reflection surfaces convert only the light beams of the corresponding light sources into luminous fluxes so as to be optimal extension angles with respect to an objective lens 9 and then fully reflect these. The reflected light beams are radiated to the recording surface of an optical disk 10 being a medium to be recorded and the existence of the information of respectively corresponding the optical disk is judged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical head device used for an optical disk drive.

[0002]

2. Description of the Related Art Currently used optical discs include C
D, CD-ROM, DVD, etc., and higher density optical disks have been developed. In order to reproduce information recorded on an optical disk, a recording surface on which information is recorded is irradiated with a light beam, and the intensity of the light beam reflected from the recording surface is detected to determine the presence or absence of the information. The information recorded on the optical disk is recorded by forming pits or marks corresponding to the pits on the recording surface of the optical disk. When reproducing the recorded information, the presence or absence of the pits or marks is detected from the intensity of the reflected beam. Further, the type of the optical disk differs depending on the shape of the pits or marks, the recording method, the thickness of the base material, and the like, and the wavelength of the light beam used for reproducing the recorded information also differs depending on the type of the optical disk. Therefore, when reproducing recorded information from different types of optical discs, a light beam having a wavelength corresponding to each type is required. For example, for a CD and a CD-ROM having a base material thickness of 1.2 mm,
A light source with a wavelength in the 780 nm band is supported, and the substrate thickness is 0.6
mm DVD is compatible with a light source having a wavelength in the 635-650 nm band. As described above, reproduction of optical disks of different types can be performed by using light sources having different wavelengths and an objective lens corresponding to the wavelength of the light source in combination. However, in order to reduce the size, weight, and cost of the optical head device, a system using one objective lens has been the mainstream, and many optical head devices have been developed as objective lens compatible optical head devices.

FIGS. 9 to 11 show an embodiment of a conventional optical head device. The optical head device comprises three light sources 1a, 1b, and 1c having different wavelengths, and a WDM (Wavelength Diviser) for multiplexing / demultiplexing a light beam or signal light.
ion Mirror: wavelength selective mirror) 4, 5, 19, 20;
A beam splitter 6 for semi-transmitting the light beam, a collimating lens 7 for converting the light beam into a light beam and condensing a signal light, a rising mirror 17 for reflecting the light beam and the signal light, An objective lens 9 designed to have an optimal aperture diameter when reproducing an optical disk with the light source 1a having the shortest wavelength among the three light sources, and light sources 1b and 1c.
Aperture restricting plate 8 for restricting the aperture diameter of objective lens 9 to be optimal when reproducing the optical disk by means of
An actuator movable section 14 including an objective lens 9 and an aperture limiting plate 8, an optical disc 10 as a recording medium,
Optical receiver 13 on which signal light from optical disk 10 is incident
a, 13b, 13c and a cylindrical lens (cylindrical lens) 1 for providing astigmatic difference to the signal light incident on the light receiver
2a, 12b, and 12c.

[0004] Three light sources 1a, 1b, 1c having different wavelengths
Are arranged at a predetermined distance from the optical disk 10. The wavelength of the light source to be used is determined according to the type of the optical disk 10 to be reproduced. For the high-density type optical disk 10a, the light source 1a having the shorter wavelength among the three light sources is used, and the medium-density type optical disk 10b The light source 1b having the next shortest wavelength is used, and the light source 1c having the next shortest wavelength is reproduced on the optical disk 10c of the low density type. The WDM 4 combines the light beams of the light sources 1a and 1b (in the figure, the optical paths of the light sources 1a, 1b and 1c at the time of reproducing the optical disk are separately shown in FIGS. 9, 10 and 11), and the WDM 5 is used. Combines the combined light beams of the light sources 1 and 2 and the light beam of the light source 3.
The beam splitter 6 has a half mirror inside, and semi-transmits the incident light beams from the light sources 1a, 1b, and 1c, and receives the signal light reflected and returned after the light beam reaches the optical disk 10. Vessels 13a, 13
b, branch into 13c side. The light beam transmitted through the beam splitter 6 is incident on a collimating lens 7 and is converted into a light beam such that the light beams from the light sources 1a, 1b, and 1c have an optimum spread angle with respect to the objective lens 9, respectively. . The signal light reflected by the optical disk 10 is
The photodetectors 13a, 13b, 1
The light is focused on 3c. At this time, since the optimum spread angle with respect to the objective lens 9 differs for each of the light sources 1a, 1b, and 1c, the light sources 1a, 1b, and 1c are arranged at positions at different distances from the collimator lens 7, respectively. The light receivers 13a, 13b, 13c are arranged so as to be equal to the respective distances from the collimating lens 7 to the light sources 1a, 1b, 1c. The light beam transmitted through the collimator lens 7 and having the optimum spread angle with respect to the objective lens 9 is totally reflected toward the optical disk 10 by the rising mirror 17. The WDM 19 separates the signal light from the optical disc 10c and the signal light from the optical discs 10a and 10b, and outputs the signal light from the optical disc 10c to the photodetector 13.
c. Similarly, the WDM 20 is used for the optical disc 1
0a and the signal light from the optical disk 10b are demultiplexed, and the signal light from the optical disk 10a is
a, the signal light from the optical disk 10b is made incident on the light receiver 13b. Here, the cylindrical lenses 12a, 1
Reference numerals 2b and 12c give astigmatic differences to the signal lights incident on the photodetectors 13a, 13b and 13c. As described above, since the aperture limiting plate 8 is arranged so that the aperture diameter of the objective lens 9 becomes the optimal aperture diameter, it is possible to reproduce different types of optical discs with one objective lens.

FIG. 12 shows another embodiment of the conventional optical head device. In this embodiment, the light sources 1a, 1a
After arranging the light beams b and 1c at positions where the light beams having the same divergence angle when transmitted through the collimating lens 7, the light beams from the light sources 1a, 1b and 1c corresponding to the optical disks 10a, 10b and 10c are arranged. Two concave lenses 18a and 18b for converting a light beam into a light beam having an optimum divergence angle with respect to the objective lens 9 are arranged, and the concave lenses 18a and 18b are arranged according to the types of optical disks 10a, 10b and 10c. , It is possible to reproduce different types of optical discs with one objective lens 9. At this time, the light sources 1a,
Since 1b and 1c are arranged at equal distances, the distance from the collimating lens 7 to the light receiver also matches, and as a result, one light receiver 13 can be shared.

FIG. 13 shows still another embodiment of the conventional optical head device. In this embodiment, the basic configuration is the same as that shown in FIG.
A hologram element 21 that converts light beams from the light sources 1a, 1b, and 1c corresponding to 10b and 10c into light beams so as to have optimal divergence angles with respect to the objective lens 9, respectively.
Is arranged in front of the aperture limiting plate 8 in the actuator movable section, and the light flux is varied according to the type of the optical disk 10, so that one objective lens 9 can reproduce different types of optical disks.

[0007]

However, in the above-mentioned conventional optical head device, the light beams of the respective light sources corresponding to the different types of optical disks are transmitted to the objective lens after passing through the collimating lens. In order to change the light flux so as to have an optimum divergence angle, it is necessary to arrange the collimating lens and the respective light sources with different distances. In addition, since the signal light reflected from the different types of optical disks is also focused on the light receiver, it is necessary to arrange each light receiver at a position equal to the distance from the collimating lens to each light source. did not become. For this reason, a plurality of light sources, light receivers, and the like are required, resulting in an increase in the size of the apparatus.

Further, in order to convert light beams from a plurality of light sources corresponding to different types of optical discs into light beams having optimum divergence angles with respect to the objective lens, a concave lens is used in accordance with the type of optical disc. In the switching device, the distance from the collimating lens to each light source can be equalized, so that the distance from the collimating lens corresponding to each light source to each light receiver becomes equal, and the common light receiving device is used. It was possible to reduce the size of the device on the light receiver side. However, for example, two concave lenses are required to correspond to three optical disks, and a complicated mechanism for switching the concave lenses is also required. Therefore, there is a disadvantage that the entire apparatus is increased in size.

Further, in an apparatus using a hologram element in order to convert a light beam of each light source into a light beam having an optimum divergence angle with respect to the objective lens, the production of the hologram element requires precision. Since processing technology is required, there is a disadvantage that the price of the apparatus is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and uses a rising mirror having a plurality of reflecting surfaces having a plurality of radii of curvature arranged integrally with a concave lens to select a wavelength on a reflecting surface of the mirror. An object of the present invention is to provide a compact and inexpensive optical head device by arranging dielectric multi-layer films having different properties so that different types of optical disks can be interchangeably reproduced by one objective lens.

[0011]

In order to solve the above-mentioned problems, an optical head device according to a first aspect of the present invention comprises a plurality of light sources for emitting light beams having different wavelengths, and a light beam or signal light. A WDM for demultiplexing, a beam splitter for transmitting / branching a light beam or signal light, a collimating lens for converting the light beam into a light beam and condensing the signal light, and a specific beam from the plurality of beams A single mirror that reflects only the light toward the objective lens side, an actuator movable section having an aperture limiting plate that limits the aperture diameter of the objective lens, and a single light receiver that receives the signal light reflected from the optical disc to be reproduced. Characterized by the following.

According to another aspect of the present invention, there is provided an optical head device according to the first aspect, wherein the single mirror has a reflecting surface having two or more radii of curvature. Each reflecting surface is provided with a dielectric multilayer film so that only the light beam of the corresponding light source is totally reflected and the beams of the other light sources are completely transmitted.

Further, in order to solve the above problem, the invention according to a third aspect of the present invention is directed to the optical head device according to the first aspect, wherein the single mirror portion is constituted by a plano-concave lens. Things.

According to the configuration of the present invention, a light source is selected according to an optical disk to be used, and a light beam from the light source is
After being synthesized by WDM, the light passes through a beam splitter and a collimator lens, is reflected by a reflecting surface of a mirror corresponding to a wavelength, and is reflected from an optical disk through an opening of an aperture limiting plate. The reflected light is given an astigmatic difference by a cylindrical lens as a signal and is incident on a light receiver.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical head device according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing one embodiment of an apparatus for reproducing an optical disk according to the present invention. As shown in FIG. 1, the apparatus according to the present invention includes n light sources 201, 202,..., 20n having different wavelengths, WDM 302 and WDM 30n for multiplexing light beams, and a light beam from the light source. A beam splitter 6 that semi-transmits and splits the signal light reflected by the optical disk toward the light receiver 13.
And a collimating lens 7 for converting the respective light beams so as to have the same divergence angle and converging the signal light to the light receiver 13 and a reflecting surface having a different radius of curvature. A mirror 11 forming a film;
The objective lens 10 is designed to have an aperture diameter for reproducing a high-density optical disk with a light source having the shortest wavelength, and the aperture diameter is limited so that the aperture diameter of the objective lens is optimal when reproducing the respective optical disks. Aperture limiting plate 8, an optical disk 10 as a recording medium, a light receiver 13 on which signal light from the optical disk is incident, and a cylindrical lens (cylindrical lens) for giving astigmatic difference to the signal light incident on the light receiver. ) 12).

The n light sources 201, 202,
.., 20n is an optical disk 10 that is a recording medium
a, 10b,..., 10n (hereinafter, when the type is not specified, the optical disk 10) is arranged at a predetermined interval. As for the wavelength of the light source, the light source 201 has the shortest wavelength, and the light sources having longer wavelengths are arranged in the order of the light sources 202, 203,. Optical disc 1 to be played
0, the wavelength of the light source used is determined. When reproducing the high-density type optical disk 10a, the light source 201 having the shorter wavelength among the light sources is used. The light source 10b having a short wavelength is used, and as the optical disk of the low density type is used, the light source having a long wavelength is used for reproduction. WDM3
02 combines the light beams of the light sources 201 and 202, and WD
M30n combines the combined light beams of the light sources 201 and 202 and the light beam of the light source 3. Next, the beam splitter 6 has a half mirror inside, and transmits the light beams from the light sources 201, 202,..., 20n to be semi-transmitted, and reflects the light beams after reaching the optical disk 10. The returning signal light is branched into two at the photodetector 13 side. The light beam transmitted through the beam splitter 6 enters the collimator lens 7 and is
The light beams from 2,..., 20n are converted into light beams having a divergent angle equal to each other. The signal light reflected by the optical disk 10 is collected by the collimator lens 7 on the light receiver 13. At this time, by arranging the respective light sources at the same distance from the collimator lens 7, the distance of the light receiver from the collimator lens 7 to each light source can be matched, and one light receiver 1
3 can be used in common. Collimating lens 7
Is reflected by the mirror 11 having a reflection surface having a different radius of curvature toward the optical disk 10 and enters the actuator movable unit 14. The actuator movable section 14 uses the objective lens 9 and the light source 202 having an optimal aperture diameter when reproducing the high-density optical disk 10a using the shortest wavelength among the n light sources. To play the optical disk 10b
Alternatively, there is provided an aperture limiting plate 8 for limiting the light beam so as to have an optimal aperture diameter when reproducing the optical disk 10n using the light source 20n.

Here, the mirror 11 will be described in detail. As shown in FIG. 2, the mirror 11 has a plurality of reflection surfaces having different radii of curvature in order to reflect light beams having different wavelengths incident from the plurality of light sources to the optical disk side. The plurality of reflective surfaces are formed by using glass to form a plurality of base materials having different radii of curvature, and when bonding the base materials together, depositing or sputtering a multilayer film acting as a mirror between the base materials. Can be produced. The first reflection surface 111 converts the light beam from the light source 201 into a light beam having an optimum divergence angle with respect to the objective lens 9 and totally reflects the light beam, and allows the light beams from the other light sources to be totally transmitted. It constitutes a dielectric multilayer film. The second reflecting surface 112 (the radius of curvature R2) is
A dielectric multilayer film that converts a light beam from the light source 202 into a light beam having an optimum divergence angle with respect to the objective lens 9 and totally reflects the light beam, and transmits all the light beams from other light sources is configured. doing. Similarly, the n-th reflection surface 11n (radius of curvature Rn) totally reflects the light beam from the light source 20n and totally transmits the light beam from the other light sources. FIG. 3 shows a wavelength transmittance characteristic of the dielectric multilayer film. At the wavelength of the light source 201 (wavelength λ1),
It shows that only the transmittance to the first surface is low and the transmittance to the other surfaces is high. On the first surface, the light beam of the light source 201 (wavelength λ1) is reflected toward the objective lens, and the other light sources 202 and It can be seen that light beams from 20n (wavelengths λ2 and λn) are transmitted.

FIGS. 4 to 6 show the optical paths of the light beams emitted from the respective light sources. In FIG. 4, the light beam from the light source 201 is reflected by the first surface 111 of the mirror 11,
Irradiates the optical disc 10a. In FIG. 5, the light beam from the light source 202 is applied to the second surface 1 of the mirror 11.
The light is reflected at 12 and irradiates the optical disk 10b. Similarly, in FIG. 6, the light beam from the light source 20n is reflected by the n-th surface 11n of the mirror 11 and irradiates the optical disk 10n. In this way, by reflecting the light beams of the respective light sources on the reflecting surfaces having different radii of curvature, it is possible to reproduce compatible optical disks of different types.

FIGS. 7 and 8 show another embodiment of the optical head device according to the present invention. As light sources with different wavelengths,
Two light sources 601 and 602 are used, and two types of optical disks as recording media are used, namely, optical disks 60a and 60c. Then, a plano-concave lens 15 is used as a medium for converting a light beam from the light source into a light beam having an optimum spread angle with respect to the objective lens 9 and reflecting the light beam. As shown in the figure, the plane side of the plano-concave lens 15 is installed so as to face the collimating lens 7, and the light beam from the light source 601 is converted into a light beam having an optimum divergence angle with respect to the objective lens 9 by the plane. The light is converted into a bundle and totally reflected, and reproduction of the high-density optical disk 60a is performed. Further, the light beam from the light source 602 is converted by the concave surface side of the plano-concave lens 15 into a light beam having an optimum spread angle with respect to the objective lens 9 and totally reflected.
The reproduction of the low-density optical disk 60c is performed.

[0021]

According to the first aspect of the present invention, light beams from a plurality of light sources corresponding to different types of optical disks are converted into light beams having an equal divergence angle by a collimating lens, and the light beams are directed toward the objective lens by a mirror. Since the light beam is reflected and has an optimum aperture diameter corresponding to the optical disk in the actuator movable section, a plurality of optical disks can be reproduced compatible with one objective lens. Also,
By making the distances from the collimating lens to the respective light sources equal, the distances from the collimating lens of the light source to the light receiver become equal, so that a plurality of different types of optical discs can be reproduced with only one light receiver.

According to a second aspect of the present invention, in the first aspect of the present invention, a plurality of reflecting surfaces having different radii of curvature corresponding to the respective light sources are provided on a mirror portion for reflecting a light beam from the light source toward the objective lens. By providing the light beam, total reflection can be performed with a light beam having an optimum divergence angle with respect to the objective lens. Therefore, even if the type of an optical disk to be reproduced and the number of light sources corresponding thereto are increased, only the reflection surface is increased. Therefore, the size of the apparatus can be reduced.

According to a third aspect of the present invention, in the first aspect of the present invention, the mirror section having a reflecting surface having a plurality of radii of curvature is formed of a plano-concave lens which has already been established in the art, and thus is advantageous in cost. It is.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment according to the present invention.

FIG. 2 is a diagram illustrating an optical path of a light beam from a mirror unit and a light source according to the present invention.

FIG. 3 is a diagram illustrating wavelength transmittance characteristics of a wavelength selection film.

FIG. 4 is a diagram showing an optical path at the time of reproducing a high-density optical disc according to the embodiment of the present invention.

FIG. 5 is a diagram showing an optical path at the time of reproducing a medium-density optical disc according to the embodiment of the present invention.

FIG. 6 is a diagram showing an optical path at the time of reproducing a low-density optical disc according to the embodiment of the present invention.

FIG. 7 is a diagram showing an optical path at the time of reproducing a high-density optical disk according to another embodiment of the present invention.

FIG. 8 is a diagram showing an optical path during reproduction of a low-density optical disk according to another embodiment of the present invention.

FIG. 9 is a configuration diagram showing one embodiment of a conventional optical head device.

FIG. 10 is a configuration diagram showing one embodiment of a conventional optical head device.

FIG. 11 is a configuration diagram showing one embodiment of a conventional optical head device.

FIG. 12 is a configuration diagram illustrating one embodiment of a conventional optical head device.

FIG. 13 is a configuration diagram showing one embodiment of a conventional optical head device.

[Explanation of symbols]

 Reference Signs List 6 Beam splitter 7 Collimating lens 8 Aperture limiting plate 9 Objective lens 10 Optical disk 10a High-density optical disk 10b Medium-density optical disk 10n Low-density optical disk 11 Mirror 12 Cylindrical lens 13 Optical receiver 14 Actuator movable unit 201 Light source 202 Light source 20n Light source 302 WDM 30n WDM

Claims (3)

[Claims] 1. A plurality of light sources for emitting light beams having different wavelengths, a WDM for multiplexing / demultiplexing a light beam or signal light, a beam splitter for transmitting / branching a light beam or signal light, and a light beam Into a light beam, and a collimating lens that condenses the signal light; a single mirror that reflects only a specific beam from the plurality of beams to the objective lens side; and an aperture that limits the aperture diameter of the objective lens. An optical head device comprising: an actuator movable section having a limiting plate; and a single light receiver for receiving signal light reflected from an optical disk to be reproduced. 2. The single mirror has reflecting surfaces with two or more radii of curvature, each reflecting surface totally reflecting only a light beam of a corresponding light source, and transmitting a beam of another light source completely. 2. The optical head device according to claim 1, wherein a dielectric multilayer film is provided on the optical head. 3. The optical head device according to claim 1, wherein the single mirror comprises a plano-concave lens.