JPH02192038A - Optical disk device in fixed optical system - Google Patents

Abstract

PURPOSE:To make unnecessary optical axis adjustment in a mobile part and a fixed part and to improve environment resistance by integrating the mobile part to trace the track of an optical disk medium and the fixed part to support an optical system. CONSTITUTION:The device consists of a mobile part 12, which has an actuator to trace an optical head to the track on the optical disk medium, and a fixed part 14, which provides a light source and an information detecting function and is fixed at the base of the optical disk device, and the mobile part 12 moves by the guide of a guide rail 15, and the mobile part 12 is linked to the fixed part 14 by a parallel light flux 7 emitted from the fixed part 14. Further the guide direction of the guide rail 15 is made correspond to the optical axis of a parallel light flux 7, and the guide rail 15 and the fixed part 14 are integrally composed. Consequently the optical axis emitted from the fixed part 14 corresponds to the moving axis of the mobile part 12, and the axis adjusting mechanism is made unnecessary. Thus the optical disk device of the fixed optical system at high reliability can be realized.

Description

[Detailed Description of the Invention] [Summary] This invention relates to an optical disk device using a fixed optical system, and in particular to an optical head access mechanism, which eliminates the need for optical axis adjustment between a movable part and a fixed part, and improves environmental resistance. The optical disc device is composed of a movable part including an actuator for making the optical head follow a track on a predetermined optical disc medium, and a fixed part equipped with a light source and an information detection function and fixed to the base of the optical disc device. A fixed optical system in which the movable part moves while being guided by a guide rail provided in the radial direction of the optical disc medium, and the movable part and the fixed part are connected by a parallel light beam emitted from the fixed part. In the system type optical disc device, the guide rail and the fixing portion are integrated with each other in a state where the guide direction of the guide rail is aligned with the optical axis of the parallel light beam.

[Industrial application field]

The present invention relates to a fixed optical system type optical disc device, and more particularly to an access mechanism for an optical head.

In the information recording field of recent computer systems and workstations, image processing technology, simulation,
Coupled with advances in technology, the capacity of external storage devices required to store output data is said to be increasing at an annual rate of 50%.

The external storage device currently mainly used for this purpose is called a magnetic disk, but this has problems in terms of reliability as the medium cannot be exchanged.

There is a problem such as 9 where the storage capacity is insufficient. Therefore, optical disks are attracting attention as an external storage device that has the potential to solve these problems. Although optical disks have a recording density 10 times that of magnetic disks, they are characterized by non-contact recording and easy medium exchange.

Furthermore, conventionally used optical discs are so-called write-once optical discs that allow the user to record data only once.
Recently, with the prospect of practical application of the magneto-optical method,
Rewritable optical discs, on which data can be recorded and erased at will, are about to be commercialized. With the advent of this rewritable optical disc, its application fields are expected to expand rapidly.

[Conventional technology]

FIG. 2 shows a configuration diagram of a conventional optical disc device.

In order to make the description of the configuration and operation easier to understand, the same parts will be designated by the same reference numerals throughout the design and their repeated description will be omitted.

In the figure, 1 is a semiconductor laser that is a light source, 2 is a collimating lens that converts the emitted light from the semiconductor laser 1 into parallel light, and 3 is a beam that separates the emitted light from the semiconductor laser 1 and the reflected light from the optical disk medium 5. A splitter 4 is a two-dimensionally movable objective lens that irradiates the optical disk medium 5 with laser light as a minute spot (the moving mechanism is omitted), 6 is a reflecting mirror, 7 is the reflecting mirror 6 and the beam splinter 3 8 is a polarizing beam splitter that detects the light containing the signal component on the optical disk medium 5; 9 is a photodetector that converts this light into an electrical signal; A focus error signal and a track error signal for making the trunk track a desired trunk are detected at the same time.

The parts of the objective lens control signal detection system in the focus and track directions are shown in FIGS. 3 and 4.

FIG. 3 is an explanatory diagram of a focus error signal detection method, and shows a well-known astigmatism method.

One of the reflected laser beams from the optical disk medium 5 that has passed through the polarizing beam splitter 8 is made to pass through a condensing lens and a cylindrical lens (not shown) to impart astigmatism to the reflected laser beam. This is detected by

At the just-focus point, the light beam with astigmatism has a circular cross-section as shown in Figure 3 (bl), and when the disk approaches and moves away from the objective lens 4 from the just-focus point, the cross-section is as shown in Figure 3 (a). , as shown in FIG.
By summing the outputs of the 0 diagonal elements and subtracting them, a focus error signal is obtained. That is, the outputs of each detection element of the four-part photodetector 10 are respectively A, B, and C.
, D, and the value obtained from (A+C)-(B+D) by an adder and a subtracter (not shown) is Ef.
An S-shaped curve of the focus error signal shown in is obtained, and the servo is applied to the just focus point which is the zero point.

FIG. 4 is an explanatory diagram of a trunk error signal detection method, and shows a well-known push-pull method. When the spot narrowed down by the objective lens 4 is at the center of a guide groove provided on the surface of the optical disk medium 5 called a pre-group 11, the reflected laser beam from the information recording medium 5 is Although the shape is symmetrical, when the spot moves left and right with respect to the pre-group 11 (that is, goes off-track), the reflected laser beam from the optical disk medium 5 becomes left and right unbalanced, and by taking the difference between the left and right sides, a track error signal is generated. is obtained.

However, compared to magnetic disk devices, which currently dominate as external storage devices, optical disk devices are inferior in terms of data transfer speed and access time. This is mainly due to the weight of the optical head of the optical disc device. Reducing the weight of the optical head is essential to improving the technology of optical disk devices.

For this reason, various studies have been made, but one of the most effective is a system that consists of a movable part including an actuator part for making the optical head follow a desired track, a light source, an optical system, and a circuit. There is a method of apparently reducing the weight of the movable part of the optical head by separating it into a fixed part and a fixed part. However, compared to conventional integrated optical heads, this method requires much stricter assembly precision, is difficult to adjust, and has problems with reliability in terms of environmental resistance.

FIG. 5 is an explanatory diagram of the assembly accuracy of a conventional fixed optical head. This figure shows V CM as a movable part moving mechanism.
(Voice Co11 Motor) 12 is shown as a block diagram of a fixed optical system optical disc device. The movable part 12 and the fixed part 14 are connected only by the parallel light beam 7 emitted from the optical system of the fixed part 14.

Here, if the mechanical precision of the movable part 12 is poor or the optical axis of the parallel light beam 13 and the movement axis of the movable part 12 do not match, the spot will be focused by the objective lens 4 as the movable part 12 moves. Deterioration of condition occurs.

Furthermore, optical axis misalignment occurs between the light incident on the objective lens 4 and the reflected light, causing an offset in focus error and tracking error signals, reducing the servo tracking range and deteriorating reliability and accuracy.

FIG. 6 is a diagram for explaining the causes of conventional axis misalignment. FIG. 6 fa) shows an example using a galvanometer mirror 6 due to angular deviation (deviation amount: σ). Figure 6 (bl is the amount of parallel movement (shift amount; D) shows an example using the reflector 6. There are two types of factors as described above. - Each mechanical factor mentioned in boat fishing Accuracy is σ=1/1
000 rad or less, D=500- or less.

[Problem to be solved by the invention]

In a conventional fixed optical system optical disk device, after adjusting the movable part 12 and the fixed part 14 separately and assembling them on the drive base of the fixed part 14, the movement axis of the movable part 12 and the optical system of the fixed part 14 are adjusted. Three or four axes were adjusted to match the output optical axes of the two.

Providing such an adjustment mechanism has the disadvantage that the reliability of the device itself is reduced (for example, the dimensional accuracy of the adjustment portion changes in response to temperature changes).

The present invention has been made in view of the above-mentioned conventional drawbacks, and aims to eliminate the need for optical axis adjustment between the movable part and the fixed part, and to improve environmental resistance.

[Means to solve the problem]

FIG. 1 is a perspective view showing the configuration of the present invention.

a movable section 12 including an actuator for causing the optical head to follow a track on a predetermined optical disk medium 5;
It consists of a fixed part 14 equipped with a light source and an information detection function and fixed to the base of the optical disc device, and the movable part 12
moves while being guided by a guide rail 15 provided in the radial direction of the optical disc medium 5, and moves along the movable portion 12.
and the fixing part 14 are connected by a parallel light beam 7 emitted from the fixing part 14.In an optical disc device of a fixed optical system, the guiding direction of the guide rail (Is) is set to the direction of the parallel light beam (7). The guide rail Q5) and the fixed portion 0 are integrated in a state where they are aligned with the optical axis.

[For production]

According to this structure, the output optical axis from the fixed part 14 and the movable part 1
The movement axes of
This makes it possible to realize an optical disk device with a fixed optical system that is less prone to axis misalignment due to external force during runaway, that is, has a highly reliable fixed optical system.

〔Example〕

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

FIG. 1 is a perspective view showing the configuration of the present invention. In the figure, the movable part 12 has a structure that allows access in the radial direction (direction of arrow P) of an optical disk medium (not shown) by a VCM (not shown). This VCM is supported by guide rails 15. Naturally, this guide rail is machined with sufficient mechanical precision. In general, the machining accuracy of cylinders is very high, and sufficient accuracy can be guaranteed to realize a fixed optical system. Reference numeral 14 denotes a fixed part centered on the optical system. Reference numeral 16 indicates a plurality of rollers built into the movable part 12, which are connected to the guide rail 1 via ball bearings, etc.
5 with high accuracy, is guided by a guide rail in accordance with the driving direction of the VCM, and is structured to be able to reciprocate in the direction of arrow P.

Conventionally, the fixed part 14 is fixed to the pace part of the drive and pitched to match the movement axis of the movable part 12.

Although it was common to have adjustment mechanisms such as rolling, in this figure, these adjustment mechanisms are removed and the fixed part 14 is integrated with the guide rail 15 of the VCM.

Specifically, the base portion of the fixed portion 14 on which the optical system is mounted and the guide rail 15 are integrated by means of enlarging means, casting means, or the like. At this time, the entire optical system shown in FIG. 1 is integrated to form an optical system.

Therefore, adjustments to the beam convergence state, adjustment of the signal reproduction system, etc. are performed using the configuration shown in FIG. 1 as one unit.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the fixed part includes a movable part that moves in the radial direction of the optical disc medium to follow a desired track, a support rail that supports the optical system, and a signal reproduction system. As a result, the moving axis of the movable part and the optical axis of the parallel light beam from the fixed part are integrated, making it possible to use a fixed optical system with high environmental resistance and reliability against aging. An optical disk device can be realized.

=11

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of the present invention, FIG. 2 is a configuration diagram of a conventional optical disc device, FIG. 3 is an explanatory diagram of a focus error signal detection method, and FIG. 4 is an explanatory diagram of a trunk error signal detection method. , FIG. 5 is a diagram for explaining the assembly accuracy of a conventional fixed optical head, and FIG. 6 is a diagram for explaining the causes of conventional axis deviation. In FIGS. 1 and 2, 5 represents an optical disk medium, 7 represents a parallel light beam, 12 represents a movable portion, 14 represents a fixed portion, and 15 represents a guide rail. secret

Claims (1)

[Claims] A movable part (1) including an actuator for causing the optical head to follow a track on a desired optical disk medium (5).
2), and a fixed part (14) equipped with a light source and an information detection function and fixed to the base of the optical disc device, and the movable part (12) is a guide provided in the radial direction of the optical disc medium (5). A fixed optical system that moves while being guided by a rail (15), and the movable part (12) is connected to the fixed part (14) by a parallel light beam (7) emitted from the fixed part (14). In the optical disc device of the above-mentioned method, the guide rail (15) is moved in a state where the guide direction of the guide rail (15) is aligned with the optical axis of the parallel light beam (7).
5) and the fixing portion (14) are integrated into a fixed optical system type optical disc device.