JPS6047240A - Optical head device - Google Patents

Abstract

PURPOSE:To realize an optical head device using plural optical spots with small- sized, lightweight and compact constitution by leading plural luminous fluxes having different wavelengths to a common optical path and also placing a luminous flux limit element based on the change in the physical property in the common optical path. CONSTITUTION:The luminous flux from two semiconductor lasers 1, 2 is made to a parallel luminous fluxes in different progressing directions mutually by a minute angle by a collimation lens 53 and made incident to a parallel flat plate 54. The luminous flux 63 of the 1st wavelength transmitted through the parallel flat plate 54 is reflected on a beam splitter 22, condensed by a condenser lens 23 to form an optical spot on an information carrier face 25 of a recorded carrier (disc) 24. The luminous flux 64 of the 2nd wavelength becomes a luminous flux placed on only one side of an optical axis by the operation of a dichroic mirror 84, reflected on the beam splitter 22 and condensed on the information carrier face 25 by the condenser lens 23. The optical spot produced in this case is formed at a position spaced by a distance from the optical spot by the luminous flux of the 1st wavelength proportional to the interval between the light sources 1 and 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to the structure of an optical head device, and in particular, the present invention relates to the structure of an optical head device, and in particular, to the structure of an optical head device, which records information while focusing a plurality of light beams whose intensity can be modulated independently onto separate points on a record carrier. The present invention also relates to an improved structure of an optical head device that performs reproduction.

[Prior art]

Optical memory systems use optical head devices that record and reproduce information by focusing light onto a record carrier.

Information recording and reproducing devices that use this type of light are expected to be used in a wide variety of fields because they can record and reproduce high-density information in a non-contact manner. Research and development efforts are underway to put it into practical use as a replacement for many information recording and reproducing devices, such as VTRs, tape recorders, magnetic disks for computers, and even document recording using microfilm.

In such an information recording and reproducing apparatus using light, many functions can be added by forming a plurality of light spots on a record carrier and independently modulating the intensity of each light spot. For example, by recording information with a first spotlight and reading out the recorded pip 1 with a second spotlight placed immediately after the first spotlight, the recording state can be monitored or the record carrier can be monitored. Defective parts can be detected. Furthermore, by using two or more spot lights, it is possible to increase the sensitivity by preheating a low-sensitivity sensitive material, and to improve the S/N by recording while erasing or reading multiple times. Furthermore, in the case of a grooveless disk (record carrier), high-density recording can be performed by using adjacent tracks as a tracking guide. Furthermore, by using two or more spotlights, focusing error detection and tracking error detection can be performed using two or more spotlights on each side.
This makes it possible to reliably prevent crosstalk between both signals.

As an optical head that performs recording and reproduction while forming two or more light spots close to each other, a type using a dichroic mirror as shown in FIG. 1 has been proposed.

In FIG. 1, a light beam of a first wavelength emitted from a light source 1 becomes a parallel light beam by a collimator lens 11, is reflected by a dichroic mirror 20, and is reflected by an optical head 20.
be led to. On the other hand, the light beam of the second wavelength emitted from the light source 2 becomes a parallel light beam by the collimator lens 12, passes through the dichroic mirror 20, and is guided to the optical head 21. In this case, the luminous flux from light source 1 and light source 2
The dichroic mirror has a high reflectance for the light beam of the first wavelength and a high transmittance for the light beam of the second wavelength. ing. By using such a dichroic mirror 20, the loss in the amount of light of each luminous flux can be reduced! . Further, in this dichroic mirror 20, the two light beams are given a slight angular separation from each other. The optical head 21 independently detects signals from two optical spots and performs autofocus, autotracking, and signal detection.
Devices with various structures can be used as long as they are functional.

In Fig. 1, two are given a small angular separation from each other.
The two light beams enter the optical head 21 and pass through the beam splitter.
22 and a condensing lens 23, the light is focused onto the information recording surface 2.45 of the record carrier (disc) 24 as two light spots.

The light beam reflected from the record carrier 24 becomes approximately a parallel light beam by the condensing lens 23, and is converted into an approximately parallel light beam by the beam splitter 22.
after being reflected by the second dichroic mirror 26
incident on . Like the dichroic mirror 20 described above, this dichroic mirror 26 has a characteristic of reflecting a light beam of the first wavelength and transmitting a light beam of the second wavelength.

Therefore, the light flux of the first wavelength is detected by the detector (photodetector).
31A and 31B, and a tracking error signal is detected. On the other hand, the light flux of the second wavelength is guided onto detectors (photodetectors) 33A and 33B via a condenser lens 32A and a cylindrical lens 32B, and the focus is detected.

In FIG. 1, if the record carrier 24 is a magneto-optical recording medium, an analyzer - (not shown -y) is placed in the optical path as necessary. When using a medium in which information is recorded by changing the reflectance or changing the surface shape, the beam cylinder 2 is used.
It is preferable that 2 be a polarizing beam splitter and that a 1/4 wavelength plate (not shown) be placed in the optical path leading to the condenser lens 23 to effectively utilize the amount of light.

In the conventional optical head device described with reference to FIG. In addition to requiring multiple semiconductor lasers (light sources) depending on the number of lights, collimator lenses and polarizing beam splitters are also required depending on the number of light beams, making the structure of the optical field complex. The disadvantage is that the weight increases.

Among these, although the increased weight of the optical head is a serious obstacle to high-speed seeking or access, conventional optical head devices have the disadvantage that it is not possible to reduce the weight of the optical head. Ta.

〔the purpose〕

The purpose of the present invention is to provide a plurality of light beams. The objective is to realize an optical head device that uses an optical head with a compact, lightweight, and compact configuration.

A feature of the present invention is to achieve the above object by guiding a plurality of light fluxes to a common optical path by changing their physical properties, and by arranging a light flux regulating element based on the change in physical properties in the common optical path. It is to be.

[Example: Akira]

The present invention will be described in detail below with reference to FIGS. 2 to 9.

In the embodiment shown in FIG. 2, a first semiconductor laser (light source) 1 emits a light beam of a first wavelength, and a second semiconductor laser (light source) 2 emits a light beam 64 of a second wavelength. These two semiconductor lasers 1.degree. 2 are fixed at a predetermined interval and housed in a single package 3. The distance between the two semiconductor lasers 1 and 2 is the same as that of the record carrier 2.
It is determined based on the distance between light spots formed close to each other on 4.

The light beams from the two semiconductor lasers 1 and 2 are turned into parallel light beams whose traveling directions differ by a small angle from each other by a collimation lens 53, and are incident on a parallel plate 54. parallel plate 5
A dichroic mirror 84 is placed on a portion of the mirror 4.

This dichroic mirror 84 is shown in FIG. 3(A).

As shown in (B), the light beam 63 of the first wavelength is transmitted, but the light beam 64 of the second wavelength has a characteristic of being reflected. The other portion 85 on the parallel plate 54 other than the dichroic mirror 84 transmits both the first wavelength light beam 63 and the second wavelength light beam 64.

In FIG. 2, the light beam 63 of the first wavelength transmitted through the parallel plate 54 is reflected by the beam streak 1 notter 22, condensed by the condenser lens 23, and then onto the information carrier surface 25 of the record carrier (disk) 24. Form a light spot. The first light beam reflected on the information carrier surface passes through the condenser lens 23, the beam splitter 22, the detector lens 55, and the analyzer 36 to the photodetector 31 on the detector 30.
incident on .

A light spot 81 generated on the detector 30 by this first wavelength light is formed at the boundary between the two light detecting sections (light receiving sections) 3]A and 31B of the light detecting section 31, as shown in FIG. In this state, the information carrier surface 25 and the photodetector 31A
, 31B are in an imaging relationship with each other, a tracking error signal can be obtained by calculating the difference in output values between these photodetectors 31A and 31B based on the light receiving section 5.

On the other hand, the light beam 64 of the second wavelength is converted into a light beam on only one side of the optical axis by the action of the dichroic mirror 84, reflected by the beam splitter 22, and focused onto the information carrier surface 25 by the condenser lens 23. Ru. The light spot generated at this time is reflected from the information phase body 25, which is formed at a distance proportional to the distance between the light sources 1 and 2, from the light spot due to the light beam of the first wavelength. The second wavelength light beam transmitted through the condenser lens 23 and the beam splitter 22 enters the detector lens 55, passes through the analyzer 36, and enters another photodetector 33 on the detector 30.
The light spot 8"2 is focused on the top.

As shown in FIG. 4, this photodetector 33 is composed of two photodetectors (light receiving sections) 33A and 33B.

A light spot 82 is formed at the boundary between these light detection sections. In this case, the photodetectors 33A, 33B and the information carrier surface 25
When the two are in an imaging relationship, the light spot 82 is set so that the same amount of light enters the two photodetectors. Therefore, the information carrier 25 shifts back and forth from the in-focus position due to longitudinal vibration such as vibration of the record carrier 24, and the light spot 82
moves in the left-right direction in FIG. 4 in accordance with this change %iK. Therefore, a focus error signal can be detected by calculating the difference between the output values based on the amount of light received by the two photodetectors 33A and 33B.

According to the embodiments described above with reference to FIGS. 2 to 4, as is clear from the comparison with the conventional configuration shown in FIG.
It is possible to eliminate most of the optical elements such as lenses and beam slitters that were required in conventional structures, which makes it possible to simplify the optical head device and reduce electrical flux, making the device more compact. It can be realized.

Further, according to this embodiment, the optical paths of the first wavelength light beam 63 and the second wavelength light beam 64 overlap over almost the entire optical system, so that the volume utilization efficiency is significantly reduced. can be increased. Moreover, the feature of an optical head device that uses a plurality of optical spots, which is that the size and function of each spot can be controlled independently, can be maintained without any inferiority compared to the conventional structure.

Next, a second embodiment of the present invention will be described with reference to FIGS. 5 and 6.

In FIG. 5, a light beam from a first light source (half-four-body laser) 1 is guided to an optical fiber 61 via a coupling lens 51''.On the other hand, a light beam from a second light source 2 is guided to a coupling lens 52''. The optical fibers 61 and 62 are guided to the optical fiber 62 via the
It has the function of transmitting a single mode of light to the other end while maintaining its polarization state, so a linearly polarized spherical wave is emitted from the exit end face of the optical fiber.

The two light beams 63 and 64 emitted from the end faces of the optical fibers 61 and 62 are made into parallel light beams whose traveling directions differ by a minute angle from each other by the collimation lens 53, and are reflected by the beam splitter 22 and sent to the condenser lens 23. The light is focused on the information carrier surface 25 of the record carrier 24 as a light spot.

In the embodiment shown in FIG. 5, instead of using the parallel plate 54 of the embodiment shown in FIG. The wavelength characteristics are given to the parts.

The embodiment shown in FIG. 5 differs from the embodiment shown in FIG. 2 in the parts explained above, but in other parts, the principle and basic configuration are substantially the same as the embodiment shown in FIG. 2. be.

The reflective surface portion 94 of the beam splitter 22 has reflection and transmittance characteristics as shown in FIG. 6(A) for a first wavelength light beam having a wavelength λl and a second wavelength light beam having a wavelength λ2. have. Further, the other reflective surface portion 95 has a wavelength λ
It has reflection and transmittance characteristics as shown in FIG. 6(B) for the light beams of the second wavelength and the wavelength λ2, respectively.

As is clear from the graph in FIG. 6, the reflective surface portion 9
4 and the reflective surface portion 95 have the same reflection and transmittance for the light beam of the first wavelength (λ1), and are so-called semi-transparent. On the other hand, for the light beam of the second wavelength (λ2), the reflective surface portion 94 acts as a mirror with almost 100% reflection, and the reflective surface portion 95 acts as a transparent object with a transmittance of 100.

Therefore, the light flux of the first wavelength can be formed into a minute spot light using the entire aperture of the condenser lens 23, and the light flux of the second wavelength can be formed into a slight spot light using half of the aperture of the condenser lens 23. A spread light spot is formed. These 2
Two spot lights are formed on the information carrier surface 25 of the record carrier 24 at positions close to each other with an interval proportional to the interval between the respective light beams 63, 64 at the exit end face of the optical fiber 61, 62.

The light beam of the first wavelength reflected from the information carrier surface 25 is transmitted to the photodetector of the detector 30 via the condenser lens 23, the beam streak notter 22, and the detector lens 55, as in the embodiment shown in FIG. The light is focused on 31.

On the other hand, the second wavelength (λ2
) passes through the condenser lens 23, passes through the reflective surface portion 95 of the beam splitter 22, and is condensed onto the photodetector 33 of the detector 30 via the detector lens 55. In this manner, the light beam 1 having the wavelength of 200 nm passes through the reflective surface portion 95 of the beam splitter 22 and can be efficiently guided to the detector 30.

Also in the embodiment described with reference to FIG. 5, the tracking error signal and the focus error signal can be reliably detected by the same effect as in the case of the first embodiment described with reference to FIGS. 2 to 4. . Furthermore, when compared with conventional optical head devices, the same effects as in the embodiments of FIGS. 2 to 4 can be achieved.

In each of the above embodiments, two semiconductor lasers 1 and 2 with mutually different wavelengths are used, and a focus error of 1 beam is produced using a luminous flux of half the effective diameter. However, the scope of application of the present invention is not limited to this, the number of light beams can be set arbitrarily, and the light beam portion used for focus error detection can also be implemented in various other ways. can. That is, a plurality of light beams are guided to a common optical path with different physical properties such as wavelength, and in the common optical path, a dichroic mirror 94 based on the change in physical properties or a reflective surface portion 94 with different wavelength characteristics is provided. Various modified embodiments may be implemented within the configuration of arranging flux limiting elements such as .95.

Next, a third embodiment of the main unit 1 will be described with reference to FIGS. 7 to 9.

In this embodiment, as shown in FIG. 8, a polarization-maintaining optical fiber 60 having two core portions 67 and 68 in the same jacket is used.

Each core 67.68 has an oval cladding 69.7 on its circumferential surface.
0 are arranged as shown in FIG.

By adopting such an fxI configuration, linearly polarized light vibrating in the same direction can be guided to the optical head without requiring special assembly and adjustment steps.

The optical head device shown in FIG. 7 uses a single optical fiber 60 having two core portions 67 and 68 as described above.
Two semiconductor lasers (light sources) driven independently of each other■
, 2 to the optical head.

In FIG. 7, the luminous flux from the first semiconductor laser is
The light is guided to the core portion 67 of the optical fiber 60 via the coupling lens 51 and the gicroic prism 49. On the other hand, the light beam from the second semiconductor laser 2 is guided to the core 68 of the optical fiber 60 via the coupling lens 52 and the beam splitter 49. Here, each semiconductor laser 1.degree.2 emits light of different wavelengths, that is, a first wavelength light having a wavelength .lambda.] and a second wavelength light having a wavelength .lambda.2. In addition, since the reflective surface of the beam splitter 49 has the characteristic of transmitting the first wavelength light and reflecting the second wavelength light, these two light beams are transmitted through the optical fiber without causing any light loss. It leads to 60. Furthermore, the optical fiber 60
Since the directions of linear polarization of each light beam propagated in the two cores 67 and 68 in the optical core 60 are the same, the optical cores 67 and 68
When the vibration directions of the respective light beams at the input end of the optical fiber are aligned in a predetermined direction, the light beam 6 of 8g1 generated at the exit end of the optical fiber
3 and the second light beam 64 each become linearly polarized light vibrating in the same direction. Further, the distance between the two cores 67 and 68 (particularly the distance at the emission end) is set at a predetermined distance depending on the distance between two light spots formed at positions close to each other on the record carrier 25.

As in the case of the embodiment shown in FIG. The light passes through the /4 wavelength plate 29 and becomes circularly polarized light, and is focused by the condenser lens 23 to form two light spots close to each other on the information recording surface 25 of the record carrier (such as an optical disk) 24.

These two light beams are reflected by the information recording surface 25, become almost parallel light beams by the condenser lens 23, and then pass through the quarter-wave plate 29 and become linearly polarized light having a plane of vibration perpendicular to that at the time of incidence. . As a result, these two beams pass through the polarizing beam splitter 22 and enter the detector lens 55.

A circular dichroic mirror 84 is formed in the center of the detector lens 55, as shown in FIG. This dichroic mirror 84 is shown in FIG.
), the first wavelength light 6.3 is transmitted, but the second wavelength light 64 is reflected. Therefore, the second wavelength light transmitted through the detector lens 55 becomes a light beam having a doughnut-shaped cross section.

The first wavelength light condensed by the detector lens 55 passes through the dichroic mirror 59 and then enters the detector 31 for signal reading and A tracking signal is detected.

On the other hand, the second wavelength light is focused by the detector lens 55, then reflected by the dichroic mirror 59, and enters another detector 33. This detector 33 is a concentric circle detector or one having a function equivalent thereto, and is placed at a position out of focus with respect to the second wavelength light, and detects a focus error based on a change in the size of the light beam. In this case, since the second wavelength light is shaped to have a donut-shaped cross section, the sensitivity when detecting focus errors using a concentric detector is improved, and the focus error signal against vertical movements such as surface wobbling of the record carrier is improved. The linearity of change can be improved, and a focus error signal can be detected accurately.

According to the third embodiment described above with reference to FIGS. 7 to 9, most of the many optical elements such as lenses and beam slits can be omitted compared to the conventional optical head device shown in FIG. It is possible to simplify the structure and reduce the weight of the optical head device. Further, as in each of the embodiments described above, since the optical paths of the first wavelength light and the second wavelength light overlap over almost the entire optical system, the volume utilization efficiency can be significantly increased. Each spot is a feature of an optical head device that uses multiple light spots at the same time. The advantage of being able to independently control the size and function of (i) can be maintained in this embodiment as well.

In each of the embodiments described above, two semiconductor radars with different wavelengths are used, and a dichroic mirror is arranged in the common optical path of the two light beams. It is also possible to configure the light to be linearly polarized light having a plane of vibration, in which case a dichroic filter is used for the dichroic mirror 84.

Also, the shape of the mask placed in the optical path is two-dimensional as shown in the figure.
In addition to the divided shape, any shape such as a donut shape or a slit shape can be used.

Furthermore, the mask placed in the optical path can be placed at any position as long as it is within a common optical path through which a plurality of light beams pass almost in common.
It can be appropriately arranged on the surface of J, the detector lens 55, the beam splitter 22, etc.

As is clear from the above description, according to the present invention, an optical head device using a plurality of light spots can be configured to be small, lightweight, and concise, and it is possible to perform seek or access operations with a light beam. Thus, an optical head device that can be operated easily and accurately can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic layout diagram illustrating the structure of a conventional optical head device, FIG. 2 is a schematic explanatory diagram showing the configuration of an embodiment of the optical head device according to the present invention, and FIG. 3 (Al is shown in FIG. 2). 3(B) is a longitudinal sectional view of the parallel plate in FIG. 1, and FIG. 4 is an explanation showing the relationship between the detector (photodetector) and the light spot in FIG. 1. 5 is a schematic explanatory diagram showing the 414 configuration of the second embodiment of the optical head device of the present invention, and FIG. 6 is a graph illustrating the characteristics of the two-split reflective surface of the beam splitter in FIG. , FIG. 7 is a schematic explanatory diagram showing a third embodiment of the optical head device according to the present invention, FIG. 8 is an explanatory diagram illustrating the structure of the optical fiber in FIG. 7, and FIG. FIG. 9(4) is a schematic front view, and FIG. 9(13) is a schematic vertical cross-sectional view. 1.2... Semiconductor radar (light source), 22. ... Beam series 123... Condenser lens, 24... Record carrier, 25... Information carrier surface, 3o... Detector, 31.33... Photodetector, 53... Collimator Lens, 54...Parallel plate, 55...Detector lens, 59...Dichroic mirror, 60.61.
62... Optical fiber, 63... Luminous flux of the first wavelength, 64... Luminous flux of the second wavelength, 84... Dichroic mirror, 94.95... Beam splitter - formed on the reflecting surface. Reflective surface part. Fig. 1 Fig. 2 Fig. 5 Fig. 3 Fig. 4 Fig. 5 Fig. 33) 22 Bud 23] Spit

Claims (1)

[Claims] (1) In an optical head device that records and reproduces information by condensing a plurality of light beams whose intensity can be modulated independently onto a record carrier via a common optical path, the plurality of light beams are physically connected to each other. Optical head device M0 characterized in that a light flux is guided to the common optical path with a changed property, and a light flux limiting element based on the change in the physical property is arranged in the common optical path (2, as set forth in claim 1) The optical head device 6 is characterized in that the +NU light beams have different wavelengths from each other.