JP3837902B2 - Optical pickup device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical pickup device that records and reproduces information.
[0002]
[Prior art]
Conventionally, an optical head for magneto-optical recording using a laser has been used as a means for recording and reproducing information on an optical disk. This optical head consists of a fixed optical system that is an assembly of individual optical components such as prisms, lenses, various sensors, and lasers with high precision, and a reflection mirror and objective lens that are reduced in weight so that they can be accessed at high speed. The basic structure is provided with a movable optical system including
[0003]
In such a system having a fixed optical system and a movable optical system, it is necessary to construct an optical path for light in both systems and to form an optical path between these systems. There were limits. On the other hand, in order to integrate the entire system, a single integrated head enables the incident from the semiconductor laser, the emission of light to the imaging system on the optical disk side, and the re-incidence and reproduction of the reflected light. The present applicant has already proposed and filed this as Japanese Patent Application No. 7-31143.
[0004]
This integrated optical head uses a laminated prism structure in which a plurality of glass plates are laminated. The laminate prism is a prism having a laminated structure in which a plurality of wafer substrates on which optical functional elements necessary for recording and reproduction of an optical disk are mounted using a wafer process technology are bonded and processed. In an integrated optical head using such a laminated prism, it goes without saying that the size and weight are reduced, and the productivity is higher than the conventional one, and the positional relationship of each optical element in the prism is maintained with the exposure mask accuracy, so that the environmental characteristics and There is an advantage of excellent long-term reliability.
[0005]
[Problems to be solved by the invention]
In an integrated optical head using a laminate prism, when a laser is incident by a semiconductor laser irradiation device, incident light is divided into three by a beam diffraction grating and emitted to the optical disc side. After inputting or outputting information to or from the optical disc, it enters the head again and is received by the reproduction sensor.
[0006]
In such an integrated optical head, when the laser from the semiconductor laser irradiation device enters the head, the light is scattered, and in addition to forming a normal optical path by reflecting and absorbing light at the interface of each layer of the laminate prism, This causes a phenomenon of so-called stray light that cannot be controlled.
[0007]
This stray light becomes a disturbance of light detection for focusing and tracking by a laser monitor or a servo sensor, and greatly affects reading of information from the optical disk. In particular, it becomes an obstacle to high integration when the optical head function is expanded by stacking a large number of prisms, which imposes restrictions on the accuracy and processing speed of information processing.
[0008]
The problem to be solved by the present invention is to provide an optical pickup device capable of processing with higher accuracy by suppressing unnecessary light diffusion and stray light in the integrated head and capable of further integration.
[0009]
[Means for Solving the Problems]
The present invention has a laminated structure in which a plurality of light transmissive substrates are laminated, and can refract and reflect incident light from an external light emitting element to read information from an optical information medium and form an optical path to a light receiving element. an optical pickup apparatus comprising a prism element and provided with a light absorbing means for suppressing a return or interference with the optical path by absorbing light overflowing from the optical path from the entrance site of the incident light to the light receiving element, said light absorbing means The absorption film is provided on the outer surface of the substrate or the interface facing the stacking direction, and the absorption film has a multilayer structure in which Si, Ti, and SiO ₂ are stacked as a combination of at least two layers. To do.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The invention described in claim 1 has a laminated structure in which a plurality of light-transmitting substrates are laminated, reads information from an optical information medium by refracting and reflecting incident light from an external light emitting element, and also to a light receiving element. An optical pickup device including a prism element that can form the optical path of the optical pickup, comprising light absorbing means that absorbs light overflowing from the optical path from the incident site of incident light to the light receiving element and suppresses return to the optical path or interference , The light absorption means is an absorption film provided on the outer surface of the substrate or an interface facing the stacking direction, and the absorption film has a multilayer film structure in which Si, Ti, and SiO ₂ are stacked as a combination of at least two layers. and become one with respect to the optical path to the light receiving element after reading the optical path and this until the optical information medium, the light absorbing means can be eliminated interference by absorbing unwanted light. Further, by arranging an absorption film prepared separately from the substrate at an appropriate position, unnecessary light collection and interference with the optical path side can be prevented. Further, it has the effect of preventing unnecessary light collection and interference to the optical path side .
[0012]
The invention according to claim 2 is a light-emitting element, a light-receiving element that receives light emitted from the light-emitting element and reflected by an optical information medium, and an optical member having a plurality of optical elements formed inside or on the surface An optical pickup device that guides the light emitted from the light emitting element to the optical information medium through the optical member and guides the light reflected by the optical information medium to the light receiving element through the optical member. A light absorbing means for absorbing light is provided in at least a part of a portion of the optical member where the optical element is not formed, and the light absorbing means is an external surface of the substrate constituting the optical member or a stacking direction. It becomes as absorbing film provided on the surface facing the absorbing film, Si, Ti, and made of a multilayer structure obtained by stacking SiO ₂ as a combination of at least two layers, the light absorbing means not It can absorb important light and eliminate interference. Further, by arranging an absorption film prepared separately from the substrate at an appropriate position, unnecessary light collection and interference with the optical path side can be prevented. Further, it has the effect of preventing unnecessary light collection and interference to the optical path side .
[0014]
Invention according to claim 3, multilayer film structure of the absorbing film, the outermost layer facing the incident direction of light and Ti, consisting as 0 transmittance substantially light there is a film thickness of 50nm or more By forming the outermost layer of Ti having a large light absorption coefficient, the transmitted light can be reduced to almost zero with a thin film thickness, and it is possible to recover unnecessary light.
[0015]
Specific examples of embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic longitudinal sectional view of an optical pickup device according to an embodiment of the present invention. FIG. 2 is an exploded perspective view showing each substrate of a laminate prism.
[0016]
In FIG. 1, a prism element 1 is disposed in the integrated optical head in a posture along a submount 51 and a semiconductor laser chip 52 mounted thereon. The prism element 1 includes a photodiode 2 on the lower end side in FIG. 1 and, as shown in FIG. 2, a first substrate 3, a second substrate 4, a third substrate 5, a fourth substrate 6, and a fifth substrate. 7. It has a structure in which the sixth substrate 8 is laminated in order from the top. These first to sixth substrates 3 to 8 are all made of glass, and the angle of the interface formed by the respective laminated surfaces is 45 ° with respect to the direction of laser irradiation from the semiconductor laser chip 52. Eggplant.
[0017]
The second substrate 4 includes a reflective film 4 a and a beam splitter film 4 b on the interface side with the third substrate 5, and a three-beam diffraction grating 4 c on the interface side with the first substrate 3. The third substrate 5 includes a beam splitter film 5a and an LD monitor hologram 5b on the interface side with the fourth substrate 6, and an astigmatism hologram 5c on the interface with the second substrate 4 side. Includes a reflective film 5d. The fifth substrate 7 functions as a polarization separation substrate, and includes a reflection film 7a and a polarization separation film 7b that are twisted with respect to the 45 ° light incident and reflection surfaces of the respective substrates 3 to 7. ing.
[0018]
On the other hand, the photodiode 2 is provided with a servo sensor 2a, a reproduction sensor 2b for S polarization and P polarization, and a laser monitor sensor 2c, respectively.
[0019]
As shown in FIG. 1, the first to sixth substrates 2 to 7 are laminated so that the angle formed between the respective interfaces is 45 °, and are laminated integrally on the photodiode 2 to form the prism element 1. Configure.
[0020]
Here, when the laser is irradiated from the outside of the second substrate 4 in the horizontal direction from the semiconductor laser chip 52, the irradiation laser is turned upward at a right angle by the reflection film 4 a and reaches the three-beam diffraction grating 4. The three-beam diffraction grating 4c converts three beams of zero-order diffracted light (main beam) and ± first-order diffracted light (side beam). These main beam and side beam are incident on the beam splitter film 4b having polarization selectivity.
[0021]
Of the light that has entered the beam splitter film 4b, the light that passes through the beam splitter film 4b is directed to the LD monitor hologram 5b of the third substrate 5, and then from the reflective film 5d to the laser monitor sensor 2c of the photodiode 2. Irradiated. The laser monitor sensor 2c monitors the light emitted from the semiconductor laser chip 52 by detecting the irradiated light.
[0022]
On the other hand, the beam components of the main beam and the side beam reflected by the beam splitter film 4 b are transmitted through the upper surface of the second substrate 4. Then, the transmitted light is incident on an objective lens (not shown) disposed on the optical disc board (not shown) side, and is imaged on the information recording surface of the optical disc board by the focusing action of the objective lens. At this time, the image spots of the two side beams on the information recording surface are imaged at substantially symmetrical positions around the image spot of the main beam. Then, information recording or reproducing signals and reading of so-called servo signals for tracking and focusing are performed on the information recording surface using the imaging spots of the main beam and side beams.
[0023]
The main beam and side beam return light reflected by the information recording surface of the optical disc is incident on the beam splitter film 4b of the second substrate 4 again. This beam splitter film 4b has a transmittance of almost 100% with respect to light having a vibration component parallel to the incident surface (P-polarized component), and with respect to a vertical vibration component (S-polarized component). Has a constant reflectivity.
[0024]
The light transmitted through the beam splitter film 4 b is incident on the beam splitter film 5 a of the third substrate 5. Similarly to the beam splitter film 4b of the second substrate 4, the beam splitter film 5a also has a transmittance of 100% for the P-polarized component and a constant reflectance for the S-polarized component. . Then, the light component transmitted through the beam splitter film 5a enters the reproduction sensor 2b via the polarizing separation film 7b and the reflection film 7a of the fifth substrate 7.
[0025]
Further, the light that does not pass through the beam splitter film 5a is reflected by this portion and then travels toward the astigmatism hologram 5c. From there, it is irradiated to the servo sensor 2a, the focus error is performed by the astigmatism method, and the tracking error is 3 beams. Done by law.
[0026]
As described above, the laser is incident on the prism element 1 from the semiconductor laser chip 52 to read and reproduce information from the optical disk. Simultaneously with this reproduction, detection of a focus error and a tracking error is performed simultaneously.
[0027]
Here, after the laser beam from the semiconductor laser chip 52 is irradiated onto the second substrate 4, it does not form a clearly separated optical path as shown in the figure but diffuses to all the substrates 3 to 8. Thus, the appearance is as if light is emitted from the entire prism element 1. And since each board | substrate 3-8 is glass, the transmitted light which passed through these board | substrates 3-8 hits the inner surface of the metal case which forms the outline material of an optical integrated head, and reflects, It also enters the prism element 1 again.
[0028]
From the above, stray light is generated inside the prism element 1 as described in the section of the prior art, and this causes disturbance to the servo sensor 2a, the reproduction sensor 2b, and the laser monitor sensor 2c. On the other hand, in the present invention, in order to suppress the occurrence of such stray light, unnecessary light does not interfere with the light irradiation light path to the optical disc board side or the light passing through the optical path to each sensor 2a, 2b, 2c. Therefore, a metal absorption film that absorbs irradiated light is provided at a predetermined position.
[0029]
FIG. 3 is an exploded side view of each of the substrates 3 to 8 and shows an example in which the first absorption film A and the second absorption film B are formed on the second substrate 4. The first absorption film A and the second absorption B are combinations in which at least two of Si, Ti, and SiO ₂ are laminated. For example, two layers of Si and Ti, A five-layer structure in which SiO ₂ , Ti, Si, and Ti are laminated in this order can be employed.
[0030]
Here, the first absorption film A and the second absorption film B are formed at the boundary between the second substrate 4 and the third substrate 5 in the example of FIG. 3, but instead, on the outer surface of the prism element 1. You may make it provide in the combination part of the other boundary of board | substrates 3-8. The arrangement of the first absorption film A and the second absorption film B is basically such that there is no interference with the optical path described above. Note that the formation of Si, SiO ₂ , Ti, or the like may be performed using a vapor deposition method or a sputtering method. In the present embodiment, the light is guided to a predetermined position using the prism element 1 having a laminated structure. However, even if the prism element 1 does not have a laminated structure, the light is reflected or refracted a plurality of times to obtain a predetermined position. The absorbing means of the present invention can be applied as long as it is an optical member having a function of leading to the above.
[0031]
Further, if the first and second absorption films A and B are arranged, it is unnecessary so that the optical path as shown in FIG. 1 can be obtained when the laser is irradiated from the semiconductor laser chip 52. All light can be absorbed by the absorption film. At this time, the absorbing film absorbs the irradiated light without reflecting it at all, and converts the light energy into heat energy, so that unnecessary light interference to the optical path directed to the optical disc board and each of the sensors 2a to 2c is caused. It can be avoided and disturbance to the irradiated light can be suppressed. Therefore, the accuracy of the exchange of information with the optical disc board and the transmission of information to the sensors 2a to 2b is improved, and a highly accurate optical pickup device can be obtained.
[0032]
【Example】
FIG. 4 is a diagram showing the characteristics of reflectance and transmittance with respect to the incident light wavelength when the film thicknesses of Si and Ti are set to 29.2 nm and Ti is 200 nm in the light incident direction. It can also be seen that the reflectance is 1% or less and the transmittance is 0 even for the laser wavelength of 790 nm from the semiconductor laser chip 52, and it functions as a light absorption film.
[0033]
In the case where the absorption film having such characteristics is uniformly formed on the side surface 5E of the prism element 1 in FIG. 1, the light that passes through the beam splitter 4b and is incident on the 5E surface can be absorbed. Unnecessary light incident on 2a and the reproduction sensor 2b can be recovered.
[0034]
FIG. 5 shows a five-layer structure in the order of Si, SiO ₂ , Ti, Si, and Ti depending on the incident direction of light. The respective film thicknesses are Si = 21.8 nm, SiO ₂ = 17.9 nm, and Ti = It is a diagram which shows the characteristic of the reflectance and transmittance | permeability with respect to an incident light wavelength when forming by 25.3 nm, Si = 31.0, and Ti = 200 nm. Such a five-layer structure also exhibits the same characteristics as those of the two-layer structure of Si and Ti shown in FIG.
[0035]
Here, it is not possible to specify from which direction the unnecessary light enters the absorption film. Therefore, even if the incident angle of light changes variously, the light absorption characteristic by an absorption film must be maintained.
[0036]
FIG. 6 is a line comparing the reflectance for S-polarized light and P-polarized light in the case of the two-layer structure of Si and Ti in FIG. 4 and the five-layer structure in the order of Si, SiO ₂ , Ti, Si, and Ti in FIG. FIG. The subscript number 1 for S and P corresponds to a two-layer structure, and the subscript number 2 corresponds to a five-layer structure.
[0037]
As is apparent from this diagram, the incident angle characteristics of the absorption films of the respective layer structures are wider in the five-layer structure of Si, SiO ₂ , Ti, Si, and Ti than in the two-layer structure. You can see that Therefore, if the incident direction of unnecessary light cannot be uniquely estimated or can be regarded as a phenomenon that occurs at random, it is effective to use an absorption film having a five-layer structure of Si, SiO ₂ , Ti, Si, and Ti. Become.
[0038]
In order to reduce the light transmittance to 0, a layer having a large absorption coefficient may be formed in the outermost layer from the light incident direction, and this is possible by using Ti as the outermost layer. That is, as shown in FIG. 7, the transmittance with respect to the film thickness of Ti has a tendency that the film thickness is 50 nm or more and the transmittance is 3% or less. Can do.
[0039]
The above is the characteristic when the light absorption film is formed on the outer surface 5E of the prism element 1, but FIG. 8 is formed at the boundary between the second substrate 4 and the third substrate 5, for example, as shown in FIG. In this case, the characteristics of reflectance and transmittance are shown. At this time, Si = 15.1 nm, SiO ₂ = 31.6 nm, Ti = 12.6 nm, Si = 23.1, and Ti = 200 nm, and have the same characteristics as those formed on the outer surface 5E. Was confirmed.
[0040]
【The invention's effect】
In the first and second aspects of the invention, the light absorbing means can absorb unnecessary light and eliminate interference with the optical path to the optical information medium and the optical path to the light receiving element after reading the optical path. The reading accuracy of information from an optical disc or the like is further improved, and the reproduction of images, sounds, etc. is further optimized. In addition, as long as the absorption film prepared separately from the substrate is placed in an appropriate position, unnecessary light collection and interference with the optical path side can be prevented. Therefore, conventional methods such as sputtering and vapor deposition are used. in easily absorbing film was formed product is obtained, it is possible to prevent Si, Ti, interference to recover the optical path side just unnecessary light combination of a limited material SiO _2.
[0043]
In the invention according to claim 3 , by forming Ti having a large light absorption coefficient in the outermost layer, the transmitted light can be reduced to almost zero even if the absorption film is thin. Can be made thinner.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view of an optical pickup device according to an embodiment of the present invention. FIG. 2 is a schematic perspective view showing an exploded substrate. FIG. 3 is a boundary between a second substrate and a third substrate. 4 is an exploded side view of the prism element showing an example of forming the film in the form of FIG. 4. FIG. 4 shows the incident light wavelength when Si and Ti are formed in the order of Si with a film thickness of 29.2 nm and Ti of 200 nm according to the incident direction of light. FIG. 5 is a five-layer structure in the order of Si, SiO ₂ , Ti, Si, Ti depending on the incident direction of light. FIG. 6 is a diagram showing the characteristics of reflectance and transmittance with respect to the incident light wavelength when formed at 21.8 nm, SiO ₂ = 17.9 nm, Ti = 25.3 nm, Si = 31.0, and Ti = 200 nm. The two-layer structure of Si and Ti in FIG. 4 and Si and SiO in FIG. _{2 is} a diagram comparing the reflectance for S-polarized light and P-polarized light in a 5-layer structure in the order of Ti, Si, and Ti. FIG. 7 is a characteristic diagram of transmittance with respect to the thickness of Ti. Diagram showing the characteristics of reflectance and transmittance when an absorption film is formed in the element 【Explanation of symbols】
DESCRIPTION OF SYMBOLS 1 Prism element 2 Photodiode 2a Servo sensor 2b Reproduction sensor 2c Laser monitor sensor 3 1st board | substrate 4 2nd board | substrate 4a Reflective film 4b Beam splitter film | membrane 4c 3 beam diffraction grating 5 3rd board | substrate 5a Beam splitter film | membrane 5b LD monitor hologram 5c Non Point aberration hologram 5d Reflective film 6 Fourth substrate 7 Fifth substrate 7a Reflective film 7b Polarization separation film 8 Sixth substrate 51 Submount 52 Semiconductor laser chip

Claims (3)

A prism element that has a laminated structure in which a plurality of light-transmitting substrates are laminated, and can refract and reflect incident light from an external light emitting element to read information from an optical information medium and form an optical path to a light receiving element. An optical pickup device comprising: a light absorbing means that absorbs light overflowing from an optical path from an incident site of incident light to a light receiving element and suppresses return to the optical path or interference ;
The light absorption means is an absorption film provided on the outer surface of the substrate or an interface facing the stacking direction, and the absorption film has a multilayer film structure in which Si, Ti, and SiO ₂ are stacked as a combination of at least two layers. the optical pickup apparatus characterized by comprising. A light-emitting element; a light-receiving element that receives light emitted from the light-emitting element and reflected by an optical information medium; and an optical member having a plurality of optical elements formed inside or on the surface, and is emitted from the light-emitting element. The optical pickup device guides the reflected light to the optical information medium via the optical member and guides the light reflected by the optical information medium to the light receiving element via the optical member, A light absorbing means for absorbing light is provided in at least a part of the portion where the element is not formed ,
The light absorbing means is an absorption film provided on the outer surface of the substrate constituting the optical member or an interface facing the stacking direction, and the absorption film is a combination of at least two layers of Si, Ti, and SiO _2. An optical pickup device comprising a multilayer film structure . The multilayer structure of the absorption film is characterized in that the outermost film facing the light incident direction is Ti, the film thickness is 50 nm or more, and the light transmittance is substantially zero . 2. The optical pickup device according to any one of 2 above.

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