JPS6212571B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording/reproducing device, and in particular, a floating element that generates dynamic pressure through relative rotational movement with a signal recording medium is provided with an optical pickup including a focus control system light source, etc. , one end of the floating element is fixedly supported at one end of a fixed frame attached to the linear feed system via an elastic body so as to be able to move freely in the focus direction and the track direction, and a cross section provided at the other end of the fixed frame. The other end of the float was freely supported through a rigid plate, with a permanent magnet piece attached to one end and the float attached to the other end so that it could move freely in the track direction in the gap of the square-shaped electromagnet. The present invention relates to an optical recording/reproducing device.

As shown in Fig. 1, in a conventional optical recording/reproducing device, an objective lens is mounted on a float that generates dynamic pressure through relative rotational movement with a signal recording medium (disk) so that it can move freely in the focal direction. As such, there is known an optical pickup section that is separated into an optical pickup section that includes an objective lens and an optical pickup section that excludes only the objective lens. That is, the optical pickup section excluding only the objective lens is fixed to a fixed frame attached to a linear feed system, and only the objective lens is attached via an elastic body so that the optical pickup section including the objective lens can be freely moved in the focal direction. It is attached to the optical pickup section that was removed. The effect is that the light beam emitted from the semiconductor laser 1 installed in the optical pickup section excluding only the objective lens is made into a parallel beam by the collimator lens 2, and then deflected by 90 degrees by the polarizing beam splitter 3 to produce a 1/4 wavelength beam. It passes through the plate 4, is deflected by the galvanometer mirror 5, reaches the objective lens 6, is reflected by the disk 7, returns to the objective lens 6, galvanometer mirror 5, quarter-wave plate 4, goes straight through the polarizing beam splitter 3, and converges. The signal passes through a lens 8 and reaches a photodetector 9 to obtain a focus error signal, a tracking error signal, and an information signal.

Depending on the float 10, the in-focus state cannot be accurately tracked. That is, it is difficult to maintain a constant distance between the objective lens 6 and the disk 7. Further, if there is a tracking error, it is corrected by changing the angle of the galvanometer mirror 5 in accordance with the tracking error signal.

In order to be able to move quickly when linearly feeding an optical pickup, it is necessary to make the optical pickup light and small. Generally, the following formula holds true for the focal length, numerical aperture NA, and aperture φ of an objective lens.

φ=2 tan (sin ^-1 NA) Therefore, in order to make the optical pickup lighter and smaller, if the numerical aperture NA is constant, the focal length must be made smaller and the aperture φ must be made smaller.

However, in the conventional technology, if there is a tracking error, it is corrected by changing the angle of the galvano mirror 5.
The light beam from the galvano mirror 5 passes through the objective lens 6
In order to ensure that the light always passes through, it is necessary that the aperture, that is, the diameter of the objective lens 6, be greater than a certain value. Therefore, in the prior art, there was a problem in that there was a limit to making the objective lens 6 smaller, and there was also a limit to making it lighter and smaller.

The present invention has been made in view of these conventional problems, and includes providing the float with an optical pickup including a focus control system light source, etc., and also allows the float to be moved not only in the focal direction but also in the track direction. The purpose is to solve the above problems by making it movable.

The present invention will be explained below based on the drawings. FIGS. 2a, b, and c are diagrams showing an embodiment of the present invention. One end of the float 10 is fixedly supported via an elastic body 12, such as a plastic elastic body or a metal plate spring body, to one end of a fixed frame 13 attached to a linear feed system.

A rigid plate 14 is fixed to the other end of the float 10,
A permanent magnet piece 15 is attached to the tip of the rigid plate 14. The permanent magnet piece 15 is disposed in a gap between an electromagnet 16 provided at the other end of the fixed frame 13 and having a square cross section.

The electromagnet 16 includes a permanent magnet 16a, a magnetic plate 16b,
and a coil 16c wound around a magnetic plate 16b. When the tracking error signal is zero, no current flows through the coil 16c, and the polarities of the permanent magnet piece 15 and the permanent magnet 16a are arranged as shown in the figure. It is held by an elastic body 12 so as not to move in the Y direction. If the tracking error signal is not zero, a current flows through the coil 16c, and the permanent magnet piece 15 moves in the tracking direction (X direction) according to Fleming's left hand rule.
Therefore, together with the elastic body 12, the float 10 also moves in the track direction.

An objective lens vertical movement mechanism 11 is provided in the center of the floating element 10. The objective lens vertical movement mechanism 11 moves in the focal direction (Z
A magnetic body with an inverted L-shaped cross section is formed on the top surface of a ring-shaped permanent magnet, a magnetic body with a rectangular cross section is formed on the top surface, and a voice coil for driving the objective lens is installed between both magnetic bodies. The current flowing through the coil controls the objective lens 6 up and down based on Fleming's left hand rule.

A housing cylinder 17 is attached to the upper part of the objective lens vertical movement mechanism 11, which houses a quarter wavelength plate 4, a polarizing beam splitter 3, a collimator lens 2, a semiconductor laser 1, and a photodetector 9. The polarizing beam splitter 3 has a shape that doubles as a cylindrical lens, making the optical system compact.

Note that instead of controlling only the objective lens 6 up and down, the entire storage tube 17 including the objective lens 6 may be controlled up and down.

The float 10 has an arc shape in its longitudinal longitudinal section, and its relative speed is 100 mm in inner diameter, 300 mm in outer diameter, and 300 mm in outer diameter.
When the rotation speed is 30Hz, they are 9.4m/sec and 28.3, respectively.
m/sec and can float sufficiently. Although this flying height depends on the shape of the float 10, when the distance between the surface of the disk 7 and the bottom of the float 10 is about 5 um, the floating amount is about 0.1 to 0.3 um. If the focal length of the objective lens 6 is 2 mm, the distance between the surface of the disk 7 and the objective lens 6 is 0.3 mm, and the NA is 0.5, the aperture φ will be 2.3 mm, and such a lens can be manufactured with less than 0.1 g. .

In addition, a polarizing beam splitter 3, a quarter wavelength plate 4,
The diameter of the photodetector 9 is approximately 2.3mm, so it is less than half the size and weighs less than the conventional one.
It can be reduced to about 1/8. Furthermore, since it is possible to keep the distance from the disk 7 to the photodetector 9 to about 10 mm, it is much shorter than the conventional distance of about 70 mm.

As explained above, the present invention provides a floater with an optical pickup including a focus control system light source, etc., and also allows the floater to move not only in the focal direction but also in the track direction. , the objective lens can be made smaller, the whole can be made smaller and lighter, and it can move quickly during linear feeding.

[Brief explanation of the drawing]

Figure 1 shows a conventional optical recording/reproducing device; Figure 2 shows a conventional optical recording/reproducing device;
Figure a is a front view showing an embodiment of the present invention, Figure 2 b is a partial sectional view showing an embodiment of the invention, and Figure 2 is a front view showing an embodiment of the invention.
FIG. c is a perspective view showing an embodiment of the present invention. 1... Semiconductor laser, 2... Collimator lens, 3
...Polarizing beam splitter, 4...1/4 wavelength plate, 5...
Galvanometer mirror, 6...Objective lens, 7...Disc, 8...Convergent lens, 9...Photodetector, 10...Floater, 11...Objective lens vertical movement mechanism, 12...Elastic body, 13...Fixed to be attached to the linear feed system Frame, 14... Rigid plate, 15... Permanent magnet piece, 16... Electromagnet, 16a... Permanent magnet, 16b... Magnetic plate, 16
c...Coil, 17...Storage tube.

Claims (1)

[Claims] 1. An optical pickup including a focus control system light source, etc. is provided on the float that generates dynamic pressure through relative rotational movement with the signal recording medium, and an optical pickup including a focus control system light source, etc. One end of the float is fixedly supported via an elastic body so that it can move freely, and one end is fixed and supported so that it can move freely in the track direction in the gap of an electromagnet with a square cross section provided at the other end of the fixed frame. 1. An optical recording/reproducing device characterized in that the other end of the floating element is freely supported via a rigid plate to which a permanent magnet piece is attached and the floating element is attached to the other end.