JPS61267946A - Optical head - Google Patents

Abstract

PURPOSE:To make an optical head small in size and light in weight by providing one piece of composite hologram element which is formed by superposing a 1/4 wavelength plate, a polalized light separating resist hologram and a hologram lens. CONSTITUTION:One piece of hologram composite element 9 which is formed by superposing a 1/4 wavelength plate 4, a polarized light separating resist hologram 2 and a hologram lens 2 is provided on an optical head 10, and light from a semiconductor laser 1 is condensed onto a disk 8 through the hologram composite element 9. Also, on the optical head 10, the 12-th split light detector for detecting light transmitting through the composite element 9 as a zero-order diffracted light, in a reflected light from the disk 8 is provided, and a tracking detecting signal is detected. Also, the second detector for detecting light which is returned and focused in the direction being different from the semiconductor 1 by a polarized light separating effect is provided, and a focus error signal is obtained. Moreover, the head 10 is loaded on an oscillating actuator 15, and brought to a two-dimensional control in the tracking direction as indicated with arrows A-A' and in the focusing direction as indicated with arrows B-B'. In this way, the optical head can be made small in size and light in weight.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to the improvement of an optical head installed in an optical disk device, and in particular, utilizes a hologram element to miniaturize the optical head and enable it to be integrated into an IC. As a result, the access time, which has been a drawback of optical disk devices, is significantly shortened.

[Industrial application field]

Recent optical heads are particularly geared toward being smaller and lighter, reflecting the need for higher speeds.

The present invention constructs an objective lens and a polarizing beam splitter, which were conventionally arranged individually at predetermined distance intervals, from a hologram, and pastes these two elements and a quarter-wave plate to form a single hologram composite element. By doing so, the optical head is characterized in that it is significantly smaller and lighter.

[Conventional technology]

Various proposals have been made in recent years regarding optical heads for optical discs that utilize holograms. For example, JP-A-59-160
It is similar to that seen in 66.

These optical heads have the potential to be downsized to a fraction of the size of conventional optical heads, but the efficiency of the optical system is poor due to the use of multiple hologram elements, and the Since the structure is complex, there are various problems when realizing it, and in particular, a further technological leap is required in terms of converting the optical head to RC.

[Problem that the invention seeks to solve]

The present invention has been made in order to achieve ultra-miniaturization of the optical head, which has not been able to solve the above-mentioned problems with conventional techniques.

[Means for solving problems]

The above problem can be solved by constructing the optical head with a single hologram composite element consisting of a quarter-wave plate, a polarization resist hologram (conventional polarization beam splitter), and a hologram lens (conventional objective lens), and using a semiconductor laser. The optical helad is configured to focus light from the hologram onto the optical disk through the holographic composite element.

[Effect]

In the present invention, the objective lens and the deflection beam splitter are each composed of a hologram, and the two elements and a quarter wavelength plate are pasted together to form a single hologram composite element, and light from a semiconductor laser is directed to this composite element in an oblique direction. The light enters the disk and is focused onto the disk.

On the other hand, the reflected light from the disk is separated by the above-mentioned composite element into 0th order light (transmitted light) and first order light which is focused in a direction different from that of the laser diode. Two split photodetectors are each arranged to obtain an error signal.

These composite elements, a semiconductor laser chip, and a photodetector are integrated, and this is attached to an actuator that secondaryly drives the disk in the direction of surface runout and in the radial direction, thereby realizing miniaturization of the optical head (IC). It is.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a side sectional view showing the structure of an optical head according to the present invention.

As shown in the figure, the optical head 10 of the present invention has a polarization separation resist hologram 2, a hologram lens 3, l/, and a wavelength vi4 superimposed on the upper surface of the housing 7, and the lower surface of the housing 7 diagonally. It has a structure in which a semiconductor laser 1 is disposed on the lower left side, a first divided photodetector 5 is disposed in the center, and a second divided photodetector 6 is disposed on the diagonally lower right side.

Note that the quarter-wave plate 4 of the optical head is disposed at a position facing the surface of the disk 8.

The operation of the optical head will be explained below.

The elliptical light emitted from the semiconductor laser 1 is transmitted to the polarization separation resist hologram 2. Hologram lens 3° 1/4 wavelength plate 4
The light is then focused onto the disk 8.

The polarization separation resist hologram 2 is an element that can change the course of light depending on the polarization direction of the light, and corresponds to a conventional polarization beam splitter.

The hologram lens 3 is a member corresponding to a conventional objective lens, and since light is incident obliquely here, it also has a circularity correction effect.

The polarization direction of the reflected light from the disk 8 is rotated by 90'' by the quarter-wave plate 4, and then the polarization separation resist hologram 2
The direction can be changed to the direction of the second photodetector 6.

Note that since these hologram elements utilize a diffraction effect, there is always some zero-order light that passes through them, and this passing light is received by the first photodetector 5.

Since the photodetector 5 is placed in the far field, it can detect a tracking signal in a tracking detection direction called a push-pull method.

On the other hand, the second photodetector 6 can obtain a focus error signal.

However, the information signal is sent to the first photodetector 5. The sum signal of each of the second photodetectors 6 is detected.

The above semiconductor laser 1. Polarization separation resist hologram 2
．． Hologram lens 3. 'wave plate 4° and split photodetector 5. By integrating the second two-split photodetector 6 as described above, its size can be reduced to 1.5+a+n x 1.5n
It becomes possible to reduce the size to about +m x 1.5a+m. This size is actually 115,000 to 1/10,000 times smaller than conventional optical heads.

FIG. 2 is a perspective view showing an embodiment of an actuator for driving an optical head.

Various structures of secondary drive type actuators having both focusing and tracking functions have been devised so far, but in this embodiment, the secondary drive type actuator is combined with an oscillating type actuator 15.

As shown in FIG.
The lens is driven two-dimensionally in the tracking direction indicated by the arrow ^-A'' and in the focusing direction indicated by the arrow BB'.

The actuator 15 equipped with each of these components is driven in the disk radial direction by a VCH (not shown).
A coarse access operation is performed.

〔Effect of the invention〕

As explained in detail above, the optical head of the present invention has a simple component configuration consisting of only one hologram composite element, a semiconductor laser, and a photodetector, so the optical system is simple and as mentioned above, it is revolutionary and compact. It is possible to reduce the weight. Also, ■Hologram lenses are easy to make because they do not require high diffraction efficiency.

■Reduced size and weight enables high-speed access comparable to magnetic disks.

There are also some really big side effects.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing the structure of the optical head of the present invention, and FIG. 2 is a perspective view showing an embodiment of an actuator for driving the optical head. In the figure, 1 is a semiconductor laser, 2 is a polarization separation resist hologram, 3 is a hologram lens, 4 is a 1/4 wavelength plate, 5 is a first photodetector, 6 is a second photodetector, 7 is a housing, and 8
1 is a disk, 9 is a hologram composite element, 10 is an optical head, 11 is a movable part, 12 is a coil, 13 is a magnetic circuit, 1
5 invented the actuator 1; 1st - To the support 7b"sB' gravity 7 la acti 2 eta n complete) Kuratatsu Figure 2

Claims (3)

[Claims] (1) An optical head for an optical disk device that optically records, reproduces, and erases information on a disk. What is claimed is: 1. An optical head comprising a plurality of hologram composite elements, the optical head being configured to condense light from a semiconductor laser onto a disk via the hologram composite elements. (2) The optical head includes a first photodetector for detecting the light reflected from the disk passing through the composite element as zero-order diffracted light, and a polarization separation effect to return and focus the light in a direction different from that of the semiconductor laser. a second photodetector that detects the light that is detected, the first photodetector detects a tracking error signal, and the second photodetector detects a focus error signal to perform light point control. An optical head according to claim 1. (3) An actuator that integrates the semiconductor laser, composite element, and first and second photodetectors that make up the optical head, and drives the integrated optical head itself in a direction perpendicular to the disk surface and in a radial direction. The optical head according to claims 1 and 2, wherein the optical head is mounted on a camera to perform light spot control.