JP2572783B2 - Optical pickup device - Google Patents

Description

The present invention relates to an infrared light beam and a light beam different from infrared light, using a semiconductor laser source for generating an infrared light beam and a wavelength conversion element. And an optical pickup device for simultaneously irradiating the recording medium with a recording medium to perform recording.

[Related Art] In recent years, an optical recording / reproducing apparatus capable of optically recording and reproducing information has attracted attention as compared with a magnetic recording / reproducing apparatus which records and reproduces information using a magnetic pickup. Became.

In the optical recording / reproducing apparatus, recording or reproduction is performed by condensing and irradiating a light beam onto a recording medium, and information can be recorded at a higher density than in the case of the magnetic method. This has the advantage that recording can be performed on a recording medium having a small size.

For this reason, it is desirable that the optical pickup device for condensing and irradiating the light beam be small in size.

By the way, in a device capable of optically reproducing or reproducing information, there is a magneto-optical device as a recording / reproducing device capable of erasing once written information data and rewriting it with arbitrary data, but the recording density is limited by the recording wavelength. There is a disadvantage, for example, JP-A-63-66527
Japanese Patent Application Laid-Open Publication No. H11-139,086 discloses an optical system using a wavelength conversion element capable of recording about twice as high density. Also, JP-A-61-2155
No. 42 discloses recording information on a recording medium provided with a photochromic organic thin film comprising a composite of a photochromic functional group and a crosslinked polymer compound, by simultaneously irradiating the recording medium with an ultraviolet laser and irradiating an infrared laser. Alternatively, it is disclosed that erasing is performed by irradiating only an infrared laser, and reproduction is performed by irradiating a recording portion of a medium with visible light. In addition, as materials for the photochromic organic thin film, there are spiropyrans and azobenzenes.
The photochromic function is development with a change in absorption spectrum when reversibly caused by different molecular structures of certain compounds A and B2. Thus, a low-energy state and a high-energy state (unstable state) become possible, and the recording medium is used as a recording medium by detecting a difference in absorbance and transmittance.

Japanese Patent Application Laid-Open No. 62-59934 discloses a wavelength conversion element made of an inorganic crystal such as lithium niobate or potassium dihydrogen phosphate (KDP) or an organic crystal such as urea or 4-nitroallynine. I have.

[Problems to be Solved by the Invention] In the case of the magneto-optical method described above, when recording is performed by irradiating the magneto-optical recording medium with a light beam that has passed through the wavelength conversion element, the temperature on the recording medium is set to a temperature higher than the Curie point. There must be. The technique disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 63-66527 does not solve this problem, and has a disadvantage that recording unevenness occurs.

JP-A-61-215542 discloses the principle of recording / reproducing / erasing on a photochromic organic thin film, but does not describe a specific pickup structure. A problem in making a practical structure is that three types of light sources are required. The increase in the number of light sources inevitably complicates and enlarges the structure of the optical system. In addition, if there is no high-power semiconductor laser that emits light in the ultraviolet region, and a large gas laser must be used, this point is also a problem that must be solved in reducing the size.

The present invention has been made in view of the above points, and provides an optical pickup device that can efficiently record and erase data on a recording medium, particularly a recording medium using a photochromic organic thin film, and has a small and simple configuration. The purpose is to provide.

[Means and Actions for Solving the Problems] In the optical pickup device of the present invention, an optical pickup device for performing recording by simultaneously irradiating an infrared light beam and a light beam different from infrared light onto a recording medium. In, a semiconductor laser light source that generates the infrared divergent light beam, and a collimator lens that converts the infrared divergent light beam generated from the semiconductor laser light source to a parallel light beam,
A wavelength conversion element that is arranged in the light beam of the infrared parallel light beam and converts a part of the infrared parallel light beam into a light beam different from the infrared light, and is different from the infrared light and the infrared light; An objective lens for condensing each of the parallel light beams on the recording medium, wherein the optical axis of the infrared light beam emitted from the semiconductor laser light source and the parallel light beam The optical axis of the light beam different from the infrared light generated by the wavelength conversion element arranged in the optical axis is parallel to each other, and the spots of the respective light beams are irradiated simultaneously and superimposed on the recording medium.

EXAMPLES Hereinafter, the present invention will be described specifically with reference to the drawings.

1 and 2 relate to a first embodiment of the present invention, and FIG. 1 is an optical pickup device 1 according to the first embodiment of the present invention.
FIG. 2 shows a state of a light spot focused and irradiated on the optical disc.

As shown in FIG. 1, a disk-shaped optical recording medium (hereinafter, abbreviated as an optical disk) 2 having a recording layer formed using a photochromic thin film is driven to rotate by a spindle motor (not shown). The optical pickup device 1 is attached to a carriage (movable table) 4 so as to face the surface, and traverses the optical disk 2 in a radial direction (that is, a concentric track or a spiral track) by carriage moving means such as a voice coil motor (not shown). In the direction,
In FIG. 1, it can be moved in the direction perpendicular to the plane of the drawing.

The optical pickup device 1 has the following configuration.

Infrared (for example, wavelength 780 nm) and visible light (for example, 630 nm)
In the infrared / visible laser diode array 5 for outputting the laser beam, a light beam for erasing or reproduction, that is, an infrared or visible light beam is generated as S-polarized light with a desired power, and this light beam is converted into a parallel light beam by a collimator lens 6. The light enters the polarization beam splitter 7. This polarization beam splitter 7
The S-polarized light beam that has passed through the quarter-wave plate 8 after being almost 100% reflected (set to a quarter wavelength for visible light) is circularly polarized for visible light, and External light is converted into an elliptical beam, which is further irradiated onto the optical disc 2 condensed by the objective lens 9. The light applied to the recording surface of the optical disc 2 is reflected by the recording surface, and the objective lens 9
After passing through the quarter-wave plate 8, the circularly polarized light becomes P-polarized light with respect to visible light, and almost 100% is transmitted through the polarizing beam splitter 7,
The light passes through a quarter-wave plate 11 provided on the opposite side of the quarter-wave plate 8 and enters a dichroic mirror 12. The dichroic mirror 12 is formed of a material that transmits visible light and reflects infrared light. Therefore, at the time of reproduction, that is, in the case of visible light, the transmitted visible light is split into two by the focus detection biprism 13 and enters the photodetector 14. A focus error signal is generated by the differential output of the two divided light receiving elements 14a and 14b (which form the photodetector 14). The focus error signal is transmitted to a lens actuator via a phase compensation circuit and a focus driver (not shown). The objective lens 9 is held in a focus state by a focus servo means applied to a focus coil 15 to be formed. In FIG. 1, a tracking error signal by a push-pull method is generated by a differential output of a light receiving element (not shown) arranged adjacently in a direction perpendicular to the paper surface, and the tracking error signal is tracked through a phase compensation circuit and a driver. A tracking servo means for applying a light spot to a target track by applying to the target coil 16 is configured.

At the time of erasing, that is, in the case of infrared light, the light is reflected by the dichroic mirror 12 and is not received by the photodetector 14.

In the first embodiment, an infrared laser diode 21 is provided to generate a recording light beam, and the S-polarized infrared light beam (for example, having a wavelength of 780 nm) of the laser diode 21 is provided. After being formed into a parallel light beam by the collimator lens 22 and having the cross-sectional shape of the light beam shaped into a circle through the shaping prism 23, the wavelength conversion element 24
Is incident on. The wavelength conversion element 24 is arranged concentrically at the center of the parallel light beam of the infrared light beam. Thus, the wavelength conversion element 24 generates an ultraviolet light beam having half the wavelength of the infrared light incident on the element 24.
These ultraviolet and infrared light beams are reflected by the polarizing beam splitter 7, become circularly polarized light through the quarter-wave plate 11, reflected by the dichroic mirror 12, and again 1 /
The light passes through the four-wavelength plate 11 to become P-polarized light, and passes through the polarization beam splitter 7. Further, the light is converted into a circularly polarized light by the quarter-wave plate 8, condensed by the objective lens 9 and irradiated on the optical disk 2, so that information can be recorded on the recording surface of the photochromic organic material.

By the way, in the first embodiment, the objective lens 9 is used for the circular light beam obtained by shaping the light beam of the infrared laser diode 21 and the ultraviolet light beam by the wavelength conversion element 24 arranged at the center of the light beam. Thus, the light spot when the light is focused and irradiated on the optical disk 2 is set as shown in FIG.

A field between the groove portions 31 having a depth of 1/8 wavelength (this wavelength is the wavelength of visible light used for reproduction) used for causing the beam spot focused on the optical disk 2 to follow the target track. In the section, a data area 32 serving as a recording area for information data is formed. Each data area 32
A pre-pit area 33 is provided at the boundary between the adjacent data areas 32, 32 to identify the track number,
An identification code such as a sector number is recorded. Note that no group section is provided on both sides of the pre-pit area 33.

By the way, the light spot by the optical pickup device 1 is condensed and irradiated so that the light spot 35 of the infrared light beam enters inside the light spot 34 of the ultraviolet light beam during recording as shown in FIG. .

That is, assuming that the wavelength of the ultraviolet light beam is λ1 and the wavelength of the infrared light beam is λ2, the light spot diameter Dλ1 of the ultraviolet light beam and the light spot diameter D of the infrared light beam as shown in FIG.
In order to make λ2 satisfy the relationship of Dλ1> Dλ2, the objective lens 9
Is set to an appropriate value such that NA (λ1) <NA (λ2) (where NA (λ1) and NA (λ2) are numerical apertures for wavelengths λ1 and λ2, respectively). In general, there is a relation of spot diameter D = λ / NA.

Further, the light spot 36 of the infrared light beam for erasing has a larger diameter than the light spot 35 of the infrared light beam for recording, so that the recorded portion can be surely erased. still,
In the field portion, the ultraviolet light beam light spot 34 has an infrared light beam light spot 35. Immediately after that, the pit on which the visible light beam light spot is recorded is irradiated, and the DAR
Check of data writing.

In FIG. 2, a light spot 35 of the infrared light beam is formed inside the light spot 34 of the ultraviolet light beam, which is shown in FIG. 6 of Japanese Patent Application Laid-Open No. 56-116004. As described above, it can be understood from the fact that the beam is more narrowed by using the ambient light. Therefore, the infrared light beam at the time of recording passing through the wavelength conversion element 24 (by the infrared laser diode 21)
The beam diameter on the optical disk 2 is different from the infrared light beam for erasing (which is generated by the infrared and visible laser diode array 5) which is not affected by the wavelength conversion element 24. The spot 36 can be made larger than the light spot 35 of the recording infrared light beam, and erasing can be performed reliably.

According to the first embodiment configured as described above, in particular, the ultraviolet light beam required for recording is generated from the infrared light beam using the wavelength conversion element 24, and the infrared light beam itself is also generated. Since it is used as a recording beam, it is possible to realize an optical pickup device having a small diameter and a simple configuration capable of effectively recording information on an optical disk using a photochromic material for a recording film.

Also, since the light spot 34 of the ultraviolet light beam and the light spot 35 of the infrared light beam are superimposed on the optical disc,
The superimposed portion, that is, the light spot 35 of the infrared light beam
Will be heated sufficiently high (above the Curie point).

Next, a second embodiment of the present invention will be described with reference to FIG.

After the S-polarized light of the infrared laser diode 21 used for recording and erasing is converted into a circular parallel beam by the collimator lens 64, the wavelength conversion disposed at the center position of this parallel beam on one incident surface of the polarizing beam splitter 62. element
It is incident on 24. The wavelength conversion element 24 is configured so that the applied voltage can be turned on and off by switching the switch 42 on and off. That is, when the switch 42 is turned off, all light passing through the wavelength conversion element 24 (including light outside the wavelength conversion element 24) becomes infrared light, and this infrared light is used for erasing. It was done. When the switch 42 is turned on, recording is performed in the same manner as in the first embodiment.

In the erasing mode, the switch 42 is turned off (no voltage is applied), the wavelength is not converted even when the light enters the wavelength conversion element 24, and the polarization beam splitter remains in the infrared light beam.
62, the light is converted into elliptically polarized light through the quarter-wave plate 8 via the beam splitter 63, and then condensed by the objective lens 9 to irradiate the optical disk 2.

On the other hand, in the recording mode, the switch 42 is turned on (voltage is applied), and the wavelength of the infrared beam on the center side of the beam is converted by passing through the wavelength conversion element 24 to be converted into an ultraviolet light beam. The infrared light beam and the ultraviolet light beam pass through the quarter-wave plate 8 through the polarization beam splitter 62 and the beam splitter 63, and are then made into elliptically polarized light. Incidentally, the recording beam spot when the optical disk 2 according to the present embodiment is focused and irradiated is the same as that shown in FIG.

Further, in the reproduction mode, the P-polarized beam of the visible / infrared laser diode 5 is converted into a parallel beam by the collimator lens 65, then is obliquely incident on the shaping surface forming the polarization beam splitter 62, shaped and circular. Become a beam. Thus, the light enters the quarter-wave plate 8 through the polarization beam splitter 62 and the beam splitter 63. Light beam 1/4
By passing through the wave plate 8, the light is converted into circularly polarized light, and is irradiated on the optical disc 2 through the objective lens 9. The return light from the optical disk 2 passes through the objective lens 9, is converted into S-polarized light by the 波長 wavelength plate 8, reflected by the beam splitter 63, transmitted through the dichroic mirror 55, and enters the half mirror 56. Half of the return light is transmitted by the half mirror 56 and received by the information reproducing photodetector 58 collected by the lens 57. on the other hand,
The light reflected by the half mirror 56 is P-polarized by the half-wave plate 59, and the return light reflected by the slope of the critical angle prism 52 is received by the photodetector 60 for focus detection.

FIG. 4 shows an optical pickup according to a third embodiment of the present invention.
71 is indicated.

An infrared light beam is emitted (P-polarized light) by the infrared laser diode 72, becomes parallel light by the collimator lens 73, and the short-axis direction of the field pattern of the semiconductor laser is aligned with the long-axis direction by the beam shaping prism 74 to form a beam shape. Becomes a circle. The circular light beam is transmitted through the wavelength conversion element 24 disposed on a part of the beam, and the transmitted light beam is converted into an ultraviolet light beam. Then
The infrared / ultraviolet light beam transmitted through the polarization beam splitter 75 and further transmitted through the beam splitter 76 is converted into elliptically polarized light by transmitting through the quarter-wave plate 77, and is condensed on the medium surface by the objective lens 9.

At this time, the ultraviolet light beam is obliquely incident because it transmits outside the axial light of the lens aperture of the objective lens 9, returns with a positional shift symmetrically with respect to the optical axis, and contains both P and S components at the quarter-wave plate 77. Of the components that have become linearly polarized light and have passed through the beam splitter 76, the S-polarized component is reflected by the polarizing beam splitter 75,
The residual P-polarized light returns to the light source and is affected by noise, but is not a problem because it is small. Similarly, the ultraviolet light beam also passes through the quarter-wave plate 77, and becomes two components of P and S linearly polarized light. The S polarized light component is reflected by the polarization beam splitter 75, and the P polarized light component returns to the recording laser 72 side. There is no problem because it is a small amount.

S-polarized visible light is emitted by the visible laser 78 for reproduction, becomes parallel light by the collimator lens 79, is reflected by the polarization beam splitter 75, is reflected / transmitted by about half by the beam splitter 76, and the transmitted light is The light is converted into circularly polarized light by the quarter-wave plate 77, collected by the objective lens 9, and irradiated on the optical disk 2. The return light from the optical disc 2 is
Transmits through the quarter-wave plate 77, enters the beam splitter 77, reflects / transmits about half each, and the reflected light is a dichroic mirror
The light passes through 80, passes through the biprism 81 for focus detection, and is received by the photodetector 82. Note that the beam splitter
Return light (infrared and ultraviolet) entering 76 is a dichroic mirror
The light is reflected at 80 so that it does not enter the photodetector 82 for obtaining a control signal and an information signal.

[Effects of the Invention] As described above, according to the present invention, a semiconductor laser light source that generates an infrared divergent light beam, and the infrared divergent light beam generated from the semiconductor laser light source is converted into a parallel light beam. A collimator lens, a wavelength conversion element that is disposed in the light beam of the infrared parallel light beam, and converts a part of the infrared parallel light beam into a light beam different from the infrared light, Since the optical pickup device has an objective lens that focuses each of the different parallel light beams on the recording medium, an infrared light beam and a light beam different from the infrared light beam are superimposed on the recording film of the recording medium. Therefore, information can be recorded efficiently.

[Brief description of the drawings]

1 and 2 relate to a first embodiment of the present invention. FIG. 1 is a block diagram of an optical pickup device of the first embodiment.
FIG. 3 is an explanatory diagram showing a state of a light spot irradiated on a recording medium according to the first embodiment, FIG. 3 is a configuration diagram of an optical pickup device showing a second embodiment of the present invention, and FIG. FIG. 9 is a configuration diagram of an optical pickup device according to a third embodiment. DESCRIPTION OF SYMBOLS 1 ... Optical pick-up apparatus 2 ... Optical disk 4 ... Carriage 5 ... Infrared and visible laser diode 7 ... Polarization beam splitter (PBS) 8, 11 ... 1/4 wavelength plate 9 ... Objective lens 12 ... … Dichroic mirror 14… photodetector 21… infrared laser diode 24… wavelength conversion element

Claims (1)

(57) [Claims] 1. An optical pickup device for performing recording by simultaneously irradiating an infrared light beam and a light beam different from the infrared light onto a recording medium, comprising: a semiconductor laser light source for generating the infrared divergent light beam; A collimator lens that converts the infrared divergent light beam generated from the semiconductor laser light source into a parallel light beam; and a part of the infrared parallel light beam that is disposed in the light beam of the infrared parallel light beam. A wavelength conversion element that converts light into a light beam different from the infrared light, and an objective lens that focuses each of the parallel light beams different from the infrared light and the infrared light on the recording medium. Optical pickup device.