JP2011023059A - Optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup separating/synthesizing luminous fluxes from a plurality of light sources having different wavelengths by an optical component having wavelength selectivity, to guide them to a plurality of objective lenses, which prevents deterioration in aberration or transmittance due to black points generated in an objective lens when light of a wavelength other than a design wavelength enters the objective lens. <P>SOLUTION: In the case of a BD 8, a laser beam from a BD light source 1 is transmitted through a mirror 5, reflected by a mirror 6, and made incident on a BD objective lens 7. Coating is applied on a DVD/CD objective lens 14 to attenuate unnecessary laser beams reflected by the mirror 5, the laser beams having been emitted from the BD light source 1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical pickup device that optically records and reproduces information.

  In recent years, optical disc apparatuses that record and reproduce information, such as optical disc apparatuses that record and reproduce various types of information such as video, images, and voices using different types of optical discs such as CDs, DVDs, and BDs as media, have been widely used. There is a demand for further miniaturization.

  In order to achieve miniaturization, an optical pickup device needs to combine light sources having different wavelengths with optical components suitable for each application in order to record / reproduce the optical disc having the above format. However, simply downsizing and combining optical components does not reduce the number of components, making it difficult to downsize the entire optical pickup device. Therefore, as one of the miniaturization methods, some optical components are shared, the optical path length of the optical pickup device is shortened, and the miniaturization is realized.

  An example of the configuration and operation of an optical pickup device that can record / reproduce BD, DVD, and CD and share some optical components will be described. FIG. 4 is a diagram showing the configuration of such an optical pickup device.

  First, the case of BD will be described. The light emitted from the blue-violet semiconductor laser which is the light source 101 for BD is reflected by the beam splitter 102, bent into a parallel light beam by the collimator lens 103, transmitted through the wave plate 104 and the mirror 105, and reflected by the mirror 106. The light is condensed on the recording medium 108 by the objective lens 107 for BD. The light reflected by the recording medium 108 returns in the reverse path, passes through the beam splitters 102 and 113, enters the detector 110 through the detection lens 109, is converted into an electrical signal, and is converted to an pit on the recording medium 108. Detect presence / absence, focus and tracking.

  Next, the case of DVD or CD will be described. The light emitted from the red semiconductor laser, which is the light source 111 that can select and emit the wavelength of the DVD or CD, passes through the wave plate 112, is reflected by the beam splitter 113, is bent into a parallel light beam by the collimator lens 103, and the wave plate The light passes through 104, is reflected by the mirror 105, and is condensed on the recording medium 115 by the objective lens 114 for DVD and CD. The light reflected by the recording medium 115 returns in the reverse path, passes through the beam splitters 102 and 113, passes through the detection lens 109, enters the detector 110, and is converted into an electrical signal so that the pits on the recording medium 115 Detect presence / absence, focus and tracking.

  Here, the objective lenses 107 and 114 for BD, DVD, and CD are attached to an integrated lens holder (not shown), and are integrated by electric means (not shown). The light is condensed on the recording medium while focusing and tracking with the recording media 108 and 115.

  On the other hand, BD light that should completely pass through the mirror 105 when using the BD is partially reflected, passes through the objective lens 114 for DVD and CD attached to the lens holder, is reflected on the surface of the recording medium 108, and returns. The incident light is condensed in the objective lens 114 for DVD and CD, causing damage such as black spots in the objective lens 114, and there is a problem of deteriorating aberration and transmittance when using the DVD and CD (FIG. 5). reference). This is a problem that occurs because the wavelength of the light source 111 for DVD and CD is 650 nm and 780 nm, whereas the wavelength of the light source 101 for BD is as short as 405 nm. Therefore, there is no problem with the objective lens 107 for BD.

  In order to solve this problem, a method of shifting the focus only of the objective lens 114 for DVD and CD so that the return light is not condensed inside the objective lens 114 for DVD and CD when BD is used can be considered. However, in order to reduce the size of the optical pickup device and to share parts, the two lenses of the objective lenses 107 and 114 are attached to an integrated lens holder (not shown), and only the objective lens 114 for DVD and CD is used. The focus cannot be shifted independently.

  That is, as a technique for reducing the size of the optical pickup device, there is a technique for sharing an optical component. However, as described above, there is a problem that damage such as a black spot is caused inside the objective lens 114 for DVD and CD. It is necessary to separate and synthesize light sources with different wavelengths. Therefore, in order to share an optical component, wavelength selectivity is required for the coating specification on the optical component. For example, there is a method of adjusting the transmission of light and the beam diameter by applying a coating having wavelength selectivity to an optical component as in the optical pickup device described in Patent Document 1.

JP 2006-120284 A

  However, as in the optical pickup device described in Patent Document 1, the separation of light and the wavelength selective coating only on the combined portion are insufficient, light other than the design wavelength leaks, and the leaked light once passes through the objective lens. When the light is reflected by the disc and returned to the objective lens again, there is a problem that the focal point is focused inside the objective lens, black spots or the like are generated in the objective lens, and the aberration and transmittance are deteriorated.

  In order to solve such problems, the present invention coats the objective lens so that light having a wavelength other than the design wavelength does not pass, reduces leakage light from the shared optical component, deteriorates the aberration of the objective lens, and reduces the transmittance. Is to prevent.

  In the optical pickup device of the present invention, in an optical pickup device having two or more wavelengths, an optical path for propagating light of the first wavelength and an optical path for propagating light of the second wavelength other than the first wavelength are one. The first wavelength is 400 to 420 nm, and the lens disposed in the optical path that propagates the light of the second wavelength is provided with a coat that attenuates or blocks the light of the first wavelength, At least one of the lens surfaces is coated, and a coating for attenuating light having the first wavelength to 1/3 or less of the entire lens is applied.

  As described above, according to the present invention, the lens disposed in the optical path that propagates the light of the second wavelength is provided with the coat that attenuates or blocks the light of the first wavelength. The effect of reducing the light leakage from the lens and preventing the deterioration of the aberration and the transmittance of the objective lens is achieved.

Configuration diagram of an optical pickup device according to an embodiment of the present invention The figure which shows the BD light attenuation | damping coat design performance of embodiment of this invention The figure which shows the objective lens for DVD and CD of embodiment of this invention, BD light attenuation | damping coating, and a recording medium Configuration of conventional optical pickup device The figure which shows the conventional objective lens and recording medium for DVD and CD

  An example of the configuration and operation of an optical pickup device capable of recording / reproducing BD, DVD and CD of the present invention will be described. FIG. 1 is a diagram illustrating a configuration of an optical pickup device.

  First, the case of BD will be described. The light emitted from the blue-violet semiconductor laser, which is the light source 1 for BD, is reflected by the beam splitter 2, is bent into a parallel light beam by the collimating lens 3, is transmitted through the wave plate 4 and the mirror 5, and is reflected by the mirror 6. The light is condensed on the recording medium 8 by the objective lens 7 for BD. The light reflected from the recording medium 8 returns the reverse path, passes through the beam splitters 2 and 13, passes through the detection lens 9, enters the detector 10, is converted into an electrical signal, and is converted into pits on the recording medium 8. Presence / absence, focus, and tracking are detected.

  Next, the case of DVD or CD will be described. Light emitted from a red semiconductor laser, which is a light source 11 that can emit light by selecting a wavelength of DVD or CD, is transmitted through a wave plate 12, reflected by a beam splitter 13, bent by a collimating lens 3 into a parallel light beam, and the wave plate. 4. Reflected by the mirror 5 and condensed on the recording medium 15 by the objective lens 14 for DVD and CD. The light reflected by the recording medium 15 returns in the reverse path, passes through the beam splitters 2 and 13, enters the detector 10 through the detection lens 9, is converted into an electrical signal, and is converted to an pit on the recording medium 15. Detect presence / absence, focus and tracking.

  Here, as in the prior art, the two lenses of the objective lenses 7 and 14 for BD, DVD, and CD are attached to an integrated lens holder (not shown), and electrical means (not shown). Thus, the light is condensed on the recording medium while being focused and tracking with the recording medium.

  BD light is used for the purpose of preventing damage to the DVD and CD objective lens 14 when part of the light to be transmitted through the mirror 5 is partially reflected and leaks into the DVD and CD objective lens 14 when the BD is used. The coating 16 (see FIG. 3) is applied, and the coating 16 composed of nine layers as shown in Table 1 is applied so that the BD light is reflected from the surface of the objective lens 14 for DVD and CD. Has been.

  The design performance at that time is shown in FIG. The refractive index of the high refractive material at a wavelength of 400 nm is 2.18214, and the refractive index of the low refractive material is 1.428855. As can be seen from FIG. 2, in the wavelength range of 400 to 420 nm, the transmittance is 1/3 or less of the wavelength range of 600 nm or more, and when BD is used, the BD light to the objective lens 14 for DVD and CD is transmitted. Leakage caused damage such as black spots inside the objective lens 14 for DVD and CD, and reduced defects that deteriorated aberration and transmittance when using DVD and CD. In the present embodiment, the attenuation coat 16 is applied to the lens surface on the incident side of the objective lens 14 for DVD and CD so that the transmittance is 1/3 or less of the wavelength range of 600 nm or more in the wavelength range of 400 to 420 nm. Even if the same attenuation coating is applied to the lens surface on the recording medium side, the effect does not change. In addition, the effect does not change even if attenuation coating is applied to both surfaces of the lens. In that case, there is no problem if the total transmittance of the front and back surfaces of the lens is 1/3 or less of the wavelength range of 600 nm or more in the wavelength range of 400 to 420 nm. Further, in this example, the coating was performed with nine layers, but the number of layers is not limited.

  According to the present invention, since the lens disposed in the optical path that propagates the second wavelength is coated to attenuate or block the light of the first wavelength, the leakage light from the shared optical component is reduced. Since it has the effect of preventing the deterioration of the aberration and the transmittance of the objective lens, it is useful when applied to an optical pickup device for recording / reproducing optical disks of a plurality of formats.

11, 111 Red semiconductor laser 1, 101 Blue-violet semiconductor laser 2, 13, 102, 113 Beam splitter 3, 103 Collimator lens 4, 12, 104, 112 Wave plate 5, 6, 105, 106 Mirror 7, 107 For BD Objective lens 14, 114 Objective lens for DVD, CD 8, 15, 108, 115 Recording medium 9, 109 Detector lens 10, 110 Detector 16 BD light attenuation coating

Claims (4)

A first optical path for propagating light of a first wavelength;
A second optical path for propagating light of the second wavelength;
In an optical pickup device having
The first optical path and the second optical path are partially shared,
The optical pickup lens disposed in the second optical path is provided with a coating that attenuates or blocks light of the first wavelength.
An optical pickup device characterized by that. The first wavelength is:
400-420 nm,
The optical pickup device according to claim 1. The coating is
Applied to at least one lens surface of the optical pickup lens disposed in the second optical path;
The optical pickup device according to claim 1, wherein: The coating is
Attenuating light of the first wavelength to 1/3 or less,
The optical pickup device according to any one of claims 1 to 3, wherein

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