JPH0644603A - Pinhole plate for optical head device and main beam detector - Google Patents

Abstract

PURPOSE:To simplify a positioning method for preventing the intrusion of a side beam and to position a pinhole or a main beam detection part on a main beam in a short time in the detecting system for the information signal of an optical head with super-high resolution. CONSTITUTION:Since the intensity distribution of the converged point-like beam of a super-high resolution image is concentric, the removal of a side beam is carried out by a pinhole 5. However, it is difficult to align a main beam with the pinhole 5 of several tens mum. Therefore, the main beam larger than the pinhole 5 is searched for around the pinhole 5. Then, by moving a pinhole plate with position confirming function 6 on the X-Y plane and introducing the main beam to the pinhole 5, the positioning of the pinhole plate with position confirming function 6 is easily performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pinhole plate and a main beam detector for an optical head device, and more particularly to a pinhole plate and a main beam detector for an optical head device applied to an optical signal recording / reproducing device using a laser light source. Regarding vessels.

[0002]

2. Description of the Related Art When recording information on an optical disc, recording is performed by forming pits on the optical disc, the pits having the same size as the laser beam narrowed down to the diffraction limit. Since the recording density is inversely proportional to the square of the laser wavelength, it is necessary to shorten the wavelength of the laser light source in order to increase the recording density. However, the semiconductor laser that can be used in the optical disk device is considered to have a limit of about 650 nm.

For this reason, introduction of a super-resolution method as disclosed in Japanese Patent Laid-Open No. 12624/1990, which can realize a spot below the diffraction limit, is under study.

Next, a pinhole plate and a main beam detector of a conventional optical head device will be described with reference to the drawings.

FIG. 5 is a view showing an optical system configuration of a conventional optical head device using a conventional pinhole plate, and FIG. 6 is a perspective view showing the shape of the conventional pinhole plate.

In FIG. 5, in a conventional optical head device, a divergent light beam emitted from a semiconductor laser 30 is converted into a parallel light beam by a collimator lens 31. Next, the light shielding plate 32
Causes the intensity of light near the center of the parallel constraint to be attenuated. The parallel light flux transmitted through the polarization beam slitter 33 is λ /
The P-polarized light is converted from the P-polarized light by the four plate 34, and is condensed on the surface of the recording medium 36 by the objective lens 35 to form a concentric super-resolution spot. The laser light that has read the information from the surface of the recording medium 36 is reflected, and the objective lens 3 is read again.
5 and becomes a parallel light beam, which passes through the λ / 4 plate 34 and is converted from circularly polarized light to S polarized light.
Is reflected by and guided to the signal detection system.

The signal detection system includes an information signal detector 43, a focus error signal detector 45, and a track error signal detector 40. The focus error signal is detected by the knife edge method and the track error signal is detected by the push-pull method. . When detecting an information signal, a conventional pinhole plate 42 as shown in FIG. 6 is arranged at the focal point of the condenser lens 41 in order to remove the sneak of the side beam, and the main beam of the main beam is transmitted so that only the main beam passes through the pinhole 5. Adjust to the position.

FIG. 7 is a diagram showing an optical system configuration of a conventional head device using a conventional main beam detector, and FIG. 8 is a perspective view showing the shape of a conventional main beam detector used in a conventional optical head device. is there.

In FIG. 7, the optical system of the conventional optical head device is the same as that shown in FIG. 5 except for the information signal detecting section, so that only the information signal detecting section will be described.

In FIG. 7, in the optical system of this conventional optical head device, the information signal detector itself has a function of removing the side beam. The focus of the re-focusing lens 41 is shown in FIG.
A conventional main beam detector 50 as shown in (1) is arranged, and the main beam detector 15 is aligned with the position of the main beam so that only the main beam is received.

[0011]

In the conventional pinhole plate and main beam detector of the above-mentioned optical head device, since the pinhole and main beam detector have a diameter of only ten and several μm, the position of the main beam is searched for. There is a problem that it is difficult to match them.

An object of the present invention is to provide a pin pole plate and a main beam detector of an optical head device which can simplify the positioning of a pinhole and a main beam detector.

[0013]

A pinhole plate of an optical head device according to the first aspect of the present invention collects light emitted from a laser light source as a minute spot on a recording medium surface by an objective lens, and the recording medium surface Light intensity that is formed from an optical system that guides the reflected light from the laser to the photodetector, and reduces the intensity of light near the center in the cross section of the light beam emitted from the laser light source between the laser light source and the objective lens A lens which has a reducing means or a phase changing means for changing the phase of light near the center, and which re-focuses the reflected light from the recording medium surface between the objective lens and the photodetector. And a pinhole plate installed at the focal position of the lens and having a pinhole that transmits only the vicinity of the center of the re-focused spot, and the photodetector receives light transmitted through the pinhole. light In the pinhole plate of the head unit, around the pin holes, and has a plurality of slit-shaped windows are formed radially around the pin hole.

In the main beam detector of the optical head device according to the second aspect of the present invention, the light emitted from the laser light source is condensed as a minute spot on the recording medium surface by the objective lens, and the reflected light from the recording medium surface is collected. A light intensity reducing means configured to include an optical system leading to a main beam detector and reducing intensity of light near a center in a cross section of a light beam emitted from the laser light source, between the laser light source and the objective lens, or A phase changing unit that changes the phase near the center is provided, and the reflected light from the recording medium surface is re-focused on the main beam detector between the objective lens and the main beam detector. In the main beam detector of the optical head, the main beam detector has a lens for And a light receiving portion of the plurality of slits are formed radially in the direction of the light detection unit around the optical detection unit for the longitudinal direction around the.

[0015]

The pinhole plate and the main beam detector of the optical head device of the present invention are provided with a pinhole or a main beam detector, and a window or a light receiver for capturing a main beam larger than them. . First, the main beam is searched by detecting the transmitted light from the window or the signal from the light receiving portion. After that, by moving the pinhole or the main beam detector in the plane and guiding the main beam to them, the pinhole or the main beam detector can be easily positioned.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

1 and 2 are perspective views showing the shapes of the first and second embodiments of the pinhole plate with a position confirming function used in the optical head device of the first embodiment of the present invention, respectively. .

The optical system of the optical head device of this embodiment is shown in FIG.
The pinhole plate 42 in the optical system of the conventional optical head device shown in FIG. 1 is replaced with the pin pole plates 6 and 6a with the position confirmation function shown in FIG. 1 or 2. Since the description of the optical system is the same as that of the conventional example, the description thereof is omitted.

In FIG. 1, a pinhole plate 6 with a position confirming function of the first embodiment has a main beam position confirming window 1 around a pinhole 5 which shields a side beam in the center and transmits only a main beam. 2, 3, 4 are provided. For example, when the main beam is captured by the main beam position confirmation window 1, the pinhole 5 can be aligned with the main beam position by moving the pinhole plate 6 with the position confirmation function in the Y direction. . When the main beam is captured by the main beam position confirmation window 2, the pinhole 5 can be aligned with the main beam position by moving the pinhole plate 6 with the position confirmation function in the X direction.

In FIG. 2, the pinhole plate 6a with the position confirming function of the second embodiment is one in which the main beam position confirming windows 7, 8, 9, 10 are wedge-shaped.
Since the widths of the main beam position confirmation windows 7, 8, 9, 10 are narrowed toward the pinhole 5a, more rapid positioning is possible.

The main beam position confirmation windows in FIGS. 1 and 2 do not necessarily have to be arranged at four positions, but may be arranged at at least one position. The optical system of the optical head apparatus according to the first embodiment of the present invention is the main beam detector 50 in the conventional optical system shown in FIG. 7, and the main beam detector 16 with a position detecting function shown in FIG. 3 and FIG. It has been replaced with. Since the description of the optical system is the same as that of the conventional example, the description thereof is omitted.

FIGS. 3 and 4 are perspective views showing the shapes of the first and second embodiments of the main beam detector with the position detecting function, which are used in the optical head device according to the second embodiment of the present invention. .

In FIG. 3, a main beam detector 16 with a position detecting function of the first embodiment has a main beam detector 15 installed at the center for detecting only the main beam,
Main beam position detector 1 of the photodetector radially patterned around the main beam detector 15.
It has 1, 12, 13, and 14.

The main beam detector 16 with the position detecting function moves the main beam detecting unit 16 with the position detecting function in the Y direction when the main beam is detected by the main beam position detecting unit 11, for example. The main beam detector 15 can be aligned with the position of the main beam. When the main beam position detector 12 captures the main beam, the main beam detector 15 is moved to the main beam position by moving the position detecting function main beam detector 16 in the X direction. Can be matched.

In FIG. 4, a main beam detector 16a with a position detecting function according to the second embodiment is provided with a central main beam detecting portion 15a and wedge-shaped patterned main beam position detecting portions 17, 18, and 19. , 20. Main beam position detector 17, 18, 19, 20
Since the width of is narrower toward the main beam detector 15, more rapid positioning is possible.

The main beam position detectors in FIGS. 3 and 4 do not necessarily have to be arranged in four places, but may be arranged in at least one place.

In the above-described optical head device of this embodiment, as a means for forming the super-resolution spot, a light shielding plate for reducing the intensity of light near the center in the cross section of the light beam emitted from the semiconductor laser is used. Although the case has been shown, it is also possible to use a phase shift plate that changes the phase of light near the center.

Further, in the above-described optical head device of the present embodiment, the case where the semiconductor laser is used as the light source is shown, but a solid-state laser or a short wavelength light source in which the semiconductor laser and the nonlinear optical element are combined is used. It is also possible to use.

[0029]

As described above, according to the present invention, by providing a window or a light receiving portion for capturing a May beam around the pinhole or the main beam detecting portion, the diameter is more than 10 μm.
The effect is that the pinhole or the main beam detector, which is only available, can be aligned with the position of the main beam in a short time.

[Brief description of drawings]

FIG. 1 is a perspective view showing a shape of a first embodiment of a pinhole plate with a position confirmation function used in an optical head device according to an embodiment of the first invention.

FIG. 2 is a perspective view showing the shape of a second embodiment of the pinhole plate with position confirming function used in the optical head device of the first embodiment of the present invention.

FIG. 3 is a perspective view showing a shape of a first embodiment of a main beam detector with a position detecting function used in an optical head device according to an embodiment of the second invention.

FIG. 4 is a perspective view showing the shape of a second embodiment of the main beam detector with the position detecting function used in the optical head device of the embodiment of the second invention.

FIG. 5 is a diagram showing an optical system configuration of a conventional optical head device using a conventional pinhole plate.

FIG. 6 is a perspective view showing the shape of a conventional pinhole plate used in a conventional optical head device.

FIG. 7 is a diagram showing an optical system configuration of a conventional optical head device using a conventional main beam detector.

FIG. 8 is a perspective view showing the shape of a conventional main beam detector used in a conventional optical head device.

[Explanation of symbols]

 1,2,3,4 Main beam position confirmation window 5,5a Pinhole 6,6a Pinhole plate with position confirmation function 7,8,9,10 Main beam position confirmation window 11,12,13,14 Main beam Position detection unit 15,15a Main beam detection unit 16,16a Main beam detector with position detection function 17,18,19,20 Main beam position detection unit 30 Semiconductor laser 31 Collimator lens 32 Light shielding plate 33 Polarization beam splitter 34 λ / 4 Plate 35 Objective Lens 36 Recording Medium 37 Beam Splitter 38 Lens 39 Beam Splitter 40 Track Error Signal Detector 41 Refocusing Lens 42 Pinhole Plate 43 Information Signal Detector 44 Knife Edge 45 Focus Error Signal Detector 50 Main Beam Detector

Claims (2)

[Claims] 1. A laser light source comprising an optical system that collects light emitted from a laser light source as a minute spot on a recording medium surface by an objective lens and guides reflected light from the recording medium surface to a photodetector. Between the objective lens and the objective lens, there is provided a light intensity reducing means for reducing the intensity of the light near the center in the cross section of the light beam emitted from the laser light source, or a phase changing means for changing the phase of the light near the center. Then
A lens for re-focusing the reflected light from the recording medium surface between the objective lens and the photodetector, and a focal point of the lens, which is transmitted only near the center of the re-focusing spot. In the pinhole plate of the optical head device for receiving the light transmitted through the pinhole, the photodetector has a pinhole plate formed with the pinhole, and the pinhole is formed around the pinhole. A pinhole plate for an optical head device, which has a plurality of slit-shaped windows radially formed at the center. 2. An optical system which collects light emitted from a laser light source as a minute spot on a recording medium surface by an objective lens and guides reflected light from the recording medium surface to a main beam detector. Between the light source and the objective lens, light intensity reducing means for reducing the intensity of light near the center in the cross section of the light beam emitted from the laser light source, or phase changing means for changing the phase near the center Further, between the objective lens and the main beam detector, a lens for re-focusing the reflected light from the recording medium surface on the main beam detector is provided, and the main beam detector is re-collected. In the main beam detector of an optical head having a photodetector that receives only near the center of a light spot, the light having the longitudinal direction in the direction of the photodetector around the photodetector A main beam detector for an optical head device, comprising a plurality of light receiving portions on a plurality of slits formed radially around the detection portion.