JPS61133050A - Recording, reproducing and erasing device of optical information - Google Patents

Abstract

PURPOSE:To constitute easily an optical information recording, reproducing and erasing device without focusing by using a head whose distance from an objective lens to a recording medium will not change even if a beam scanning mirror acts. CONSTITUTION:A laser beam L21 is narrowed down by an objective lens 13 through a deflection beam spliter 11 and a l/4 plate 12, and then reflected by a galvano mirror 14 to focus on the recording medium 30. The spot temperature of the recording medium rises and recording or erasing can be possible. The reproduction of information can be realized by picking up the reflected beam from the recording medium as it is by a photodetector shown by a code 20 in the figure. The recording of information in the tape width direction is carried out by rotating the galvano mirror 14. At this time its center 17 and that of the circular arc of the head 16 is set equal and the focusing position of the objective lens 13 is so constituted to overlap it on the circular arc, the laser beam can focus on the recording medium as shown by codes L14a and L14b without fail.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention utilizes laser light and focuses the light onto a recording medium, and is suitable for recording, reproducing, and erasing information. Regarding equipment.

[Background of the invention]

The above-mentioned device is an optical system composed of many lenses, and the lenses are mainly composed of glass.

In addition, many of the lenses 4o have a lens drive mechanism because it is necessary to automatically perform m-point adjustment.

An optical disk device will be described below as a typical example of such an optical system. Optical disk devices are published in magazines [Hitachi Hyoron J
This is already well known in the August 1984 issue.

FIG. 2 shows the overall configuration of the optical system of a conventional optical disk device. The symbols of each part in the figure and their operations will be explained below. 1 is a laser diode serving as a light source. A collimation lens 2 converts the light beam from the laser diode 1 into parallel light. Reference numeral 3 denotes a polarizing beam splitter (hereinafter abbreviated as PBS), which transmits the output light of the collimation lens and refracts the return light from the λ/4 plate indicated by symbol 4, which will be described below. λ·//4[X4 is used for phase polarization of light in order to facilitate discrimination between incident light and reflected light at PB83. Reference numeral 5 denotes an objective lens, which is used to condense incident light. A coupling lens 6 receives the light flux from the PBS 3 and condenses it. The Campling lens 6 is composed of two semicylindrical lenses orthogonally crossed. 7 is a photodetector. The photodetector 7 indirectly detects the light spot shape of the output light L5 from the objective lens 5 by detecting the light spot shape of the incident light L6 from the coupling Lemmelo. 8 is an actuator, and the actuator 8 adjusts the focal position of the output light L5 of the objective lens 5 according to the output of the photodetector 7. 81 is a lens drive unit, and the lens drive unit 81 is an actuator 8.
The position of the objective lens 5 is adjusted by the drive control output from. 9 is a disk on which information can be optically recorded, reproduced, erased, etc., and a part thereof is shown. The above recording is performed on the disk 9 by irradiating a desired light spot onto the disk surface with the output light L5 from the objective lens 5.

It allows playback, deletion, etc. 10 is a motor, and the disk 9 is driven by the motor 10.

FIG. 3 shows a conventional embodiment of the photodetector 7 shown in FIG. In the same figure, L6 indicates the output light L6 of the compling lens 6 of FIG. 2. Pl.

P2. P3. P4 is a photodiode for converting the amount of light into an air distribution signal. When the light spot of the incident light L6 is a perfect circle, the photodiodes P1. ．． P2. P3,
and P4 output voltages as vl, V2 . V3. V4
Then, these a are set so that they are each equal. 71 and 72 are subtracters for tracking on the disk 9, respectively. By detecting the output signal of the difference (vl-V2) between the output voltage V1 of the photodiode P1 and the output voltage v2 of the photodiode P2,
It is indirectly determined whether the output light L5 from the objective lens 5 is irradiated onto a predetermined twin. If you have an objective/
When the output light L5 of the lens 5 does not strike the information recording line of the disk 9 symmetrically, a difference occurs between the output voltages v1 and v2.
It detects the deviation from the upper recording line and outputs a tracking control signal TAI for controlling the position of the objective lens 5 until the difference disappears.

Similarly to the subtracter 71, the subtracter 72 uses the output voltages v3 and v4 of the photodiodes P3 and P4 as input signals to obtain a tracking control signal T of 2. 73 and 74 are adders, 75 is a comparator, and the output light L of the objective lens 5.
5 is a part for obtaining two output signals for autofocus control to adjust the depth of focus applied to the disk 9. This means that when the depth of focus matches the recording line of the disk 9, the incident light L6 is perfectly circular and the photodiodes PL, P2. P3. P4 is evenly incident on P4, and the amount of luminous flux is also the largest, and the output voltage is v1°V2. V3. V4 are equal and their magnitude is maximum. If the depth of focus is shifted and the incident light L6 is not shaped like an ellipse, the photodiode P1°P2. P3. P4 (7) Output voltage V1
．． V2. (V1+73) and (72) created with V3゜v4
+V4) so that there is no difference in the value. This phenomenon is detected using adders 73, 74 and comparator 75, and the position of objective lens 5 is adjusted until the output signal FA becomes zero. FIG. 4 shows a conventional embodiment of a driving section for the objective lens 5 using tracking and autofocus control.

In the same figure, Stt.

812, 813, 814 are coils. 815 C is a holder for the objective lens 5. 816.817 is how it comes out, 8
18.819 is a spring, and 820 is a frame. The objective lens 5 is fixed with a holder 815 and springs 818.81
9, it is installed on the frame 820 of the optical head. The magnets 816 and 817 are used as one of the elements to determine the position of the objective lens 5. By using a magnetic material such as a piece of iron in the holder 5rst, the magnets 816 and 817 have an attractive force, and the tensile strength of the springs [18 and 819] The position of the objective lens 5 is determined. In accordance with the focus control output signal FA from FIG. 3, tR is also applied to the coils 811 and 812 to move the position of the objective lens 5 up or down to obtain a desired depth of focus.

Tracking control signals T and TB are each coil 81
3. Apply current to 814, adjust the left and right positions of the objective lens 5, and perform desired tracking.

As described above, according to the conventional method, tracking is performed to accurately irradiate the recording line of the disk with a light spot, and the depth of focus is controlled. However, tracking and focus control require thousands of complicated control devices, and it is desired to simplify these as much as possible.

[Purpose of the invention]

The purpose is to provide equipment.

[Summary of the invention]

In the present invention, an optical system that does not require an automatic focusing mechanism is realized by using a head in which the distance between the objective lens and the recording medium does not change even if the beam scanning mirror operates.

[Embodiments of the invention]

FIG. 5 shows a recording medium 30 used in the present invention.

This is made by pasting a thin recording material 91 on a base 92 made of flexible plastic or the like by vapor deposition or the like.

FIG. 6 shows the principle of recording, reproducing, and erasing on the tape-shaped recording medium mentioned above. All of these operations are performed by forming a laser beam spot on the tape-shaped recording medium with the laser beam 42 using the lens 41, and using heating, reflected light, etc. there. Information is recorded on the tape-shaped recording medium in both the tape advancing direction and the tape width direction. Of these, scanning in the tape width direction (indicated by arrow 46) is performed by scanning with laser beam 42.

However, the problem at this time is the problem of focal position deviation due to scanning of the laser beam in the tape width direction and the problem of reflected light.

This situation is shown in FIG. FIG. 2A shows a cross section 102 obtained by cutting the tape in the width direction and the objective lens 101. In this case, when the laser beam LLOL is incident perpendicular to the tape, it is focused on the tape, but when the laser is scanned (LiO2), it is not focused on the tape surface, and the reflected light does not return to the objective lens. It diverges in a different direction (
LiO2). In this case, information cannot be reproduced. As a countermeasure, the tape is made into an arc shape (103) as shown in FIG. 7(b). If you irradiate this with a laser beam, the focus will always be on the tape, and it will not diverge when it returns.

FIG. 8 shows a specific configuration of the head. The tape-shaped recording medium 30 is pressed from above and below by heads 16 and 17 in order to maintain the aforementioned circular arc shape.

These heads are optically transparent and pass a focused laser beam, designated L61, to form a beam spot on the tape. At this time, the configuration of the Beamsbot device is also shown.

First, recording and erasing information will be explained. A laser beam indicated by L2L is focused by a polarizing beam sinter 11, a λ/4 plate 1 a metal plate 2, and an objective lens 13. Thereafter, it is reflected by the galpan mirror 14 and focused onto the recording medium 30. Therefore, the spot temperature of the recording medium increases, making recording or erasing possible. The difference between recording and erasing is the difference in laser beam intensity. Reproduction of information can be realized by using the method described above and picking up the reflected light from the recording medium as it is with a photodetector 20.

Information is recorded in the tape width direction by rotating 14 galvano mirrors. At this time, the centers of the arcs of the head indicated by centers 17 and 16 of the galvanometer mirror 14 are the same,
Moreover, if the focal position of the objective lens 13 is configured to overlap on a circular arc, the focal point will always be focused on the recording medium as shown by LL4a and L14b in the figure. Therefore, this optical system does not require a focusing system as long as the tape and head are always used in close contact with each other.

The optical system shown in FIG. 9 is similar to that shown in FIG. 9, but an AO modulator 51 and its modulator 52 are used instead of the galvanometer mirror. Other details are the same as those in FIG. As another method, it is also possible to use a polygon mirror or the like in place of the galvano mirror.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to easily configure an optical information recording/erasing device that does not require focusing.

[Brief explanation of drawings]

An explanatory diagram of the embodiment, FIG. 2 is an overall configuration diagram of the optical system of a conventional optical disk device, FIG. 3 is a configuration diagram of a conventional detector for detecting the focal position, and FIG. 4 is a diagram of a conventional objective lens drive unit. Diagram,
FIG. 5 is a schematic diagram of a tape-shaped information recording medium, and FIG. 6 shows recording on the tape-shaped information recording medium. Figure 7 is an illustration of the relationship between tape shape and focal point position; Figure 8 is an illustration of the arcuate head; Figure 9 is an illustration of the principle of playback and erasing.
The figure shows an embodiment of the present invention using an AO modulator system. 1...L/-f ta(ode), 2...Collimation lens, 3...Polarizing beam splitter, 4...
λ/4 plate, 5... objective lens, 6... coupling lens, 7... photodetector, 9... disk, 11...
...Polarizing beam splitter, 12...λ/4 plate, 13
...Objective lens, 14...Galvano mirror-116.
...circular navel, foil 10 I position f3 12 ft-121 30 bean paste 50 +360 50 +360 5'V (α) (b) IOI

Claims (1)

[Claims] 1. A movable mirror is used to transmit light from a light source onto an information recording medium made of a tape-shaped reversible material whose optical density changes when heated and rapidly cooled, and which returns to its original state when heated and slowly cooled. In a device that uses an objective lens to form a beam spot to record, reproduce, and erase information, the tape is movable in an arcuate shape so that a beam spot is always formed on the recording medium even if the movable mirror is moved. An optical information recording/reproducing/erasing device characterized in that the center of rotation of the mirror and the center of the arc are the same.