JPH03192542A - optical pickup - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical pickup used in an optical disk drive or the like.

(Prior Art) One of the ways to miniaturize the optical system of the optical pickup is an optical integrated circuit using a thin film waveguide.

Figure 5 shows a conventional example of such an optical integrated circuit type.
A waveguide layer 33 is laminated on the substrate 31 and buffer layer 32. The semiconductor laser 34 is coupled to the end face of the Si substrate 31 and guides laser light to the waveguide layer 33. The guided light passes through the grating 35, is diffracted by the condensing grating coupler 36, propagates in the air, and is transferred to the optical information recording medium 37.
reach. The light reflected by the optical information recording medium 37 enters the condensing grating coupler 36 again, becomes a guided light, is diffracted by the grating 35, and is split into two lights, which are sent to the photodetector sections 38-1 to 38-4. The light is received by Using the electrical signals from the photodetection group, the arithmetic circuit generates a reproduced signal,
Obtain focus error signal and tracking error signal.

Such an optical pickup can be manufactured using planar technology, and significant improvements can be expected in terms of making the device lighter and smaller and simplifying the manufacturing process.

(Problem to be Solved by the Invention) However, in the above configuration, the light is focused on the optical information recording medium 37 via the condensing grating coupler 36,
A grating coupler 36 condenses the reflected light from the medium again.
In order to guide the light into the waveguide 1 through
%, 50%, which means that the efficiency is poor, that is, the light from the laser diode (LD) 34 (here, the LD 34
In this case, it does not mean that the amount of money diverges from the LD.
Of the diverging light from the optical recording medium 37, 25% of the light (which is the size of the aperture of the condensing grating coupler 36) reaches the optical recording medium 37, and of the light reflected from the optical recording medium 37, 25% % will be guided into the waveguide, and 10% will be halved by the beam splitter 35 and directed to the detection system, resulting in an effective amount of 2.5% or less.

In an optical pickup used for an optical disk memory, it is necessary to improve the S/N ratio of a detection signal, and to increase the amount of light reaching the optical recording medium and the view reaching the detection system as much as possible.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical pickup configured to increase the amount of light that reaches an optical recording medium and the amount of light that reaches a detection system.

(Means for Solving the Problems) An optical pickup according to claim 1 of the present invention has an integrated detection system in which at least an optical signal detection system is integrated, and irradiates light from a light source onto an optical recording medium. In an optical pickup that reproduces information from or records information on an optical recording medium by guiding light from the light source to the integrated detection system, an optical path from the light source to the integrated detection system via the optical recording medium. It is characterized in that an optical system (hereinafter referred to as an irradiation light guiding optical system) for guiding light to irradiate an optical recording medium and detect an optical signal is arranged separately from the integrated detection system.

(Function) According to the present invention, the irradiation light guide optical system uses a collimator lens, a polarizing beam splitter, a quarter wavelength plate, a condensing lens, etc. in the same way as the optical system of a normal optical pickup. Accordingly, the optical recording medium can be sufficiently irradiated with light from the semiconductor laser, and the light from the optical recording medium can be brought to the integrated detection system with high efficiency. Furthermore, the optical signal detection system can be fabricated using planar technology using an integrated detection system.

(Example) FIG. 1 is a configuration diagram of an optical pickup according to the present invention.

In the figure, numeral 1 is a semiconductor laser as a light source, 2 is a semiconductor laser as a light source;
The coupling lens 3 for collimating the light beam is a quarter-wave plate;
1 is a condensing lens that focuses light onto a recording medium, 5 is an optical disk as an optical recording medium, 6 is a prism, 7 is a polarizing beam splitter film, and 10 is an integrated detection device manufactured by planar technology as an optical signal detection means. 1G is an adhesive layer that joins the prism 6 and the integrated detection system 10, and 15 is a metal mask layer having an opening. This corresponds to the coupling lens 2, the quarter-wave plate 3, the condenser lens 4, and the polarizing beam splitter film 7.

The light emitted from the semiconductor laser 1 is converted into parallel light by the coupling lens 2. At this time, the polarization direction of the parallel light is perpendicular to the plane of the paper. This parallel light is reflected by the polarizing beam splitter film 7 integrated in the prism 6, and is reflected by the quarter wavelength plate 3.
It becomes circularly polarized light, becomes convergent light by the condensing lens 4, and connects a spot on the optical disk 5.The light reflected by the optical disk 5 passes through the condensing lens 4 and the quarter-wave plate 3, and becomes parallel to the plane of the paper. The polarized light is transmitted through the polarizing beam splitter film 7. Thereafter, 10 parts of the light reach the integrated detection system, become 1M mode guided light, propagate within the waveguide layer 12, and enter the photodetector 18.

Next, the configuration of the integrated detection system 10 will be explained.

A buffer layer 13, a waveguide layer 12 . Gap adjustment layer 11. A metal mask 15 is integrated.

Furthermore, a prism 6 is placed on top of this with an adhesive layer 16 in between. A photodetector 18 is formed within the Si substrate 14, and the output of the photodetector 18 is taken out to the outside by an electrode 19.

FIG. 2 shows a plan view of the integrated detection system 10, an optical disk 5.
The light reflected by the prism 6 is coupled to the waveguide layer 12 through the opening (portion A) of the metal mask 15 close to the bottom surface of the prism 6, and becomes guided light. The guided light is guided through a waveguide condensing mirror surface 20a made by removing the waveguide layer 12.

20b, one of the six reflected lights becomes a convergent waveguide light, and a two-split light detection section 18a,
The other reflected light that is focused on 18b also becomes convergent waveguide light and is sent to another two-split light detection section 18c.

The light is focused on 18d. When the optical disk 5 and the condensing lens 4 are in a focused state, the waveguide condensing mirror surface 20a.

The light reflected and converged by 20b is transmitted to photodetectors 18a and 18b.
and between the photodetectors 18c and 18d, respectively. On the other hand, when the optical disk 5 and the condensing lens 4 are out of focus and move away from each other, the condensing point is located at the photodetector 18.
a and in the direction of the photodetector 18d. Also,
When approaching from focus, the focal point shifts toward the photodetectors 18b and 18c. These photodetectors 1
The outputs of 8a to 18d are calculated by an arithmetic circuit (not shown),
A reproduction signal, a focus error signal, and a tracking error signal can be obtained.

Regarding each refractive index of the integrated detection system 10, the refractive index of the prism 6 is nl, the refractive index of the adhesive layer 16 is net gap adjustment/the refractive index of W11 is nl, the refractive index of the waveguide layer 12 is nl, and the refractive index of the waveguide layer 12 is nl. If the refractive index of the layer 13 is 05, then the structure is such that n-nigonc>n,>n, , n1° is satisfied. Specifically, when the wavelength is 790 nm, prism 6, high refractive index glass 5FII np=1.7656 adhesive layer 16 polyimide nc=1.70 gap layer 11, SiO□ sputtered film n,=1.467, d= 0.52 μm waveguide layer 12 5iON sputtered film n, = 1.557. d=1.5pm Buffer layer 13SiO, thermal oxide film n,,=1.460. d=1.0 μm. The length of the opening of the metal mask 15 was 2 m.

In order to guide light from the bottom of the prism 6 to the waveguide layer 12, it is sufficient to arrange the prism 6 so that the incident angle of the light at the bottom of the prism 6 is 61 degrees. The coupling efficiency to the layer is maximized. In other words, if the opening of the metal mask 15 is made to have the same size as the diameter of the beam reaching the bottom surface of the prism 6, about 80% of the total amount of light can be guided into the waveguide layer 12.

The coupling efficiency can also be controlled by changing the thickness of the gap adjustment layer 11. Of course, the refractive index of the gap adjustment layer 11 may be changed.

Another example is shown in FIG. 3, in which a prism 8 is newly provided in contact with the polarizing beam splitter film 7, and a quarter wavelength plate 3 is bonded to the prism 8.

Another embodiment is shown in FIG. 4. In this embodiment, the parallel light emitted from the semiconductor laser 1 and the coupling lens 2 passes through the polarizing beam splitter 28 and passes through the quarter-wave plate 3 and the condensing lens 4. After that, the optical disc 5 is reached.

The polarization direction of the light emitted from the semiconductor laser 1 is parallel to the plane of the paper. When the light reflected by the optical disk 5 passes through the quarter-wave plate 3, it becomes polarized light perpendicular to the plane of the paper, is reflected by the polarizing beam splitter film 27 of the polarizing beam splitter 28, enters the prism coupler 26, and becomes a TE mode guide. The light propagates through the waveguide R12 as a wave light. With this configuration, the arrangement of the optical disc 5, the integrated detection system 10, and the irradiation light guide optical system can be changed from the configuration shown in FIG. 1.

It can be adapted to the spatial space of each pickup head.

(Effects of the Invention) As explained above, in the optical pickup of the present invention, (1) Almost 100% of the light that passes through the coupling lens reaches the optical recording medium (optical disk).

■Almost 100% of the light reflected from the optical recording medium comes from prisms.
Reach the integrated detection system. By optimizing the coupling to the integrated detection system, approximately 80% of the light reaches the photodetector, making it possible to provide an optical pickup with high light utilization efficiency.

Furthermore, in the optical pickup according to the second aspect, coupling to the integrated detection system can be optimized.

[Brief explanation of drawings]

FIG. 1 is a detailed diagram showing the configuration of the optical pickup of the present invention.
FIG. 2 is a plan view of the integrated detection system of FIG. 1, FIGS. 3 and 4 are diagrams showing other embodiments of the optical pickup according to the present invention, and FIG. 5 is a diagram showing the configuration of a conventional optical pickup. FIG.

Claims (1)

[Claims] 1. By having an integrated detection system that integrates at least an optical signal detection system, by irradiating light from a light source onto an optical recording medium and guiding the light from the recording medium to the integrated detection system, In an optical pickup that reproduces information from or records information on an optical recording medium, an optical path from the light source to the integrated detection system via the optical recording medium includes an optical path to the optical recording medium separate from the integrated detection system. An optical pickup characterized in that an optical system for guiding light to irradiation and optical signal detection (hereinafter referred to as an irradiation light guiding optical system) is arranged. 2. The integrated detection system includes a waveguide layer, a gap adjustment layer having a lower refractive index than the waveguide layer, and a metal mask portion having an opening, and a prism having a higher refractive index than the waveguide layer. 2. The optical pickup according to claim 1, wherein the optical pickup is made of a material bonded through an adhesive layer having a higher refractive index than the waveguide layer.