JPH0352126A - Optical head - Google Patents

Abstract

PURPOSE:To improve the density of a device and retrieval speed by providing an objective lens and a pressure center at the center of a slider, installing a trapezoidal prism out of the slider and controlling tracking by means of rotation. CONSTITUTION:An optical beam 23 is made incident on a polarizing mirror 27 through optical devices 24 and 25 and the trapezoidal prism 26 whose apex angle is alpha and it forms an image on an optical disk medium 31 as an optical spot 32. The reflected light beam 33 forms the image on a photodetector 36 in a reverse coarse, and detects the error signal of focus and tracking. A focus driving means 37 and a tracking driving means 38 control the optical spot 32 in accordance with the signal. The slider 30 floats through an air layer with the medium 30, the objective lens 28 and a pressing point P are provided in the center of the slide, and the pressure point P is pressed by a pressure spring 40. Thus, the optical head is miniaturized and the density of the device and retrieval speed can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical head of an optical recording and reproducing apparatus that optically records or reproduces information on an optical disc recording medium. Conventional technology: Information is recorded on optical disk media using semiconductor lasers. As an optical head for an optical recording/reproducing apparatus for reproduction, there is a conventional optical head as shown in FIG. In FIG. 6, the diffused light emitted from the semiconductor laser (2) is converted into a parallel light beam by a condenser lens 2 and becomes a light beam 3. The light beam 3 is arranged to be incident on the polarized beam splinter 4 with P polarization, and is transmitted in the direction of 1/4 wavelength. The transmitted light beam 3 has its optical path changed by a deflection mirror 6 so as to be approximately perpendicular to the optical disk medium 8, and then passes through an objective lens 7.
is focused to form a light spot 9 on the optical disk medium 8. The light beam 10 reflected from the optical disk medium 8 passes through the objective lens 7 and the deflection mirror 6 and enters the quarter-wave plate 5. The light beam lO becomes S-polarized by passing through the quarter-wave plate 5, and is reflected by the polarizing beam splitter 4.
The reflected light beam 10 is further converged by an aperture lens 11 and a cylindrical lens l2, and is received by a photodetector 13. The photodetector l3 detects the reproduced signal and
The focus error signal is detected using the so-called astigmatism method, and the tracking error signal is detected using the push-bull method. The focus error signal detected from the photodetector l3 is applied to the focus drive means 14 and the objective lens 7
is controlled in the focus direction. Similarly, the tracking error signal is applied to the tracking drive stage l5 to control the objective lens 7 in the tracking direction. Furthermore, a deflection mirror 6, an objective lens 7 and a focus. Trunking drive means 14.15 are mounted on the transfer platform 16,
They are configured to move together in the radial direction of the optical disc medium 8 and record/reproduce arbitrary tracks.

Problems to be Solved by the Invention In the optical recording/reproducing device as an information memory, increasing the recording density per volume (hereinafter referred to as device density) and increasing the search speed have traditionally been major iiifis.
Unlike magnetic recording and reproducing devices in which only a minute magnetic head moves, optical recording and reproducing devices move comparatively heavy objects such as an objective lens, focus, and tracking drive means, which reduces the search speed. In addition, in terms of recording density, it is superior to magnetic recording and reproducing devices, but in the case of magnetic recording, since the head is minute, a structure in which disk media are stacked (hereinafter referred to as a stacked structure) is used, and the device density is higher than that of optical recording and reproducing devices. There are some that are even better than playback devices. For this reason, optical recording and reproducing devices must improve not only the search speed but also the device density. In general, to increase device density in optical recording and reproducing devices, (1)
In order to increase the search speed, it is possible to increase the numerical aperture of the objective lens, (2) reduce the wavelength of the semiconductor laser, or (3) increase the number of optical disk media to create a stacked structure. It is conceivable to reduce the mass of the transport means or (1) increase the thrust of the transport means. In general, increasing the thrust does not increase the device density, so it is desirable to make the optical head smaller, increase the numerical aperture, and create a stacked structure. By the way, in order to prevent contact between the optical disk medium 8 and the objective lens 7, the conventional optical head requires a working distance M (WD in the figure) of about 1.5 to 2 mm. Even if the numerical aperture was increased, the focal length could not be reduced, and the diameter of the light beam increased in proportion to the numerical aperture, and the optical component (volume) increased in proportion to the third power. Also, since the depth of focus becomes shallower in proportion to the square of the numerical aperture, focus control accuracy must be improved accordingly.
There was also the problem that the focus drive means 14 became large. Furthermore, when the numerical aperture is increased, the imaging performance deteriorates due to the inclination of the disk, and there is a problem that sufficient recording and reproducing performance cannot be obtained, so a numerical aperture of about 0.5 is used practically. On the other hand, in order to form the optical disk medium 8 into a stacked structure, the optical head is miniaturized. It is important to note that in the structure of conventional optical heads, even if a focus drive means and a tracking drive hand are provided on the condensing lens side, the head will not be as small as a magnetic head, and the device density will be improved. It is difficult to achieve this goal. In the end, in the conventional configuration, even if the numerical aperture is increased and a stacked structure is used, the fFI degree does not improve. like this! In order to solve the problem of i8, a floating optical head has been proposed in which the optical head is floated above the optical disk medium 8 using a slider like a magnetic head. but,
In a floating optical head, a yawing phenomenon occurs in the slider due to the surface runout of the disk and the vibration of the spring that holds the slider, which deteriorates the stability of the optical spot. The present invention is intended to solve these problems. Means for Solving In In order to solve the above-mentioned problems, the present invention provides (1)
A laser light source, a condenser lens that condenses light emitted from the laser light source, a mirror that deflects the condensed light beam in the direction of an optical disk medium, and an objective lens that converges the light beam onto the optical disk medium. , a slider floating above the optical disk medium and equipped with the mirror and the objective lens; a pressing means for pressing the slider against the optical disk medium; a light separating means for separating reflected light from the optical disk medium; A light detection means for receiving light is provided, and the pressing center of the pressing means is arranged approximately on the optical axis of the objective lens. A laser light source, a condenser lens that condenses the light emitted from the laser light source, a mirror that deflects the condensed light beam in the direction of the optical disk medium, and an objective that converges the light beam onto the optical disk medium. a lens, a slider floating above the optical disc medium and equipped with the mirror and the objective lens, a pressing means for pressing the slider against the optical disc medium, a light separating means for separating reflected light from the optical disc medium, and separation. and a prism having an acute apex angle between the condensing lens and the mirror, and the prism is rotated to perform tracking control. be. (3) A laser light source, a condensing lens that condenses the light emitted from the laser light source, a light separating means that separates the condensed light beam from the reflected light from the optical disk medium, and receives the separated reflected light. a mirror for deflecting the focused light beam in the direction of the optical disk medium; an objective lens for converging the light beam onto the optical disk medium; A slider equipped with a mirror and the objective lens, and a pressing means for pressing the slider against the optical disc medium are configured to be movable in the radial direction of the optical disc medium. Effect: With the above configuration, a stable floating optical head can be obtained, so the optical head can be miniaturized and the optical disk recording medium can have a stacked structure. Furthermore, since the working distance of the objective lens can be reduced and the numerical aperture can be increased, it is possible to improve the imaging density and search speed. EXAMPLE An example of the present invention will be explained below based on FIGS. 1 to 4. No.lrf! J shows an embodiment of the optical recording/reproducing apparatus according to the present invention, and FIG. 2 is a view taken in the direction of arrow C in FIG. As shown in FIG. 1, the diffused light emitted from the 2L semiconductor laser is condensed by a condenser lens 22, and a parallel light beam 2
3 and is arranged so as to be incident on the polarized beam splinter 24 with P polarization. The light beam 23 incident with P polarization passes through a polarization beam splitter 24, passes through a 1/4 wavelength beam 25, and becomes circularly polarized. Further, the optical path passes through a trapezoidal prism 26 with two non-parallel surfaces and an apex angle α, and is bent by a deflecting mirror 27 held in a mirror holder 29 so as to be approximately perpendicular to the optical disc medium 3l. The light is converged and narrowed down onto the recording surface of the optical disc medium 31 to form a light beam 32.

30 is a slider that floats through an air layer between it and the optical disk medium 31, and includes an objective lens 28 and a deflection mirror 2.
7 is installed. The objective lens 28 is attached to an opening of φd provided approximately at the center of the slider 30 as shown in FIG.
It is designed to irradiate. The light beam 33 reflected by the optical disk medium 3l passes through the objective lens 28, the deflection mirror 27, and the trapezoidal prism 26, has its polarization changed from circularly polarized light to S-polarized light by the 174-wave plate 25, and enters the polarizing beam splitter 24.
Since the light beam 33 is S-polarized, it is reflected by the polarization beam splitter 24, converged by an aperture lens 34 and a cylindrical drill lens 35, and formed into an image on a photodetector 36. As in the conventional example, the photodetector 36 is configured to detect a focus error signal using the astigmatism method and a tracking error signal using the push-pull method along with the reproduction signal. 40 is a pressure spring, one end of which is connected to the transfer table 4 as shown in FIG.
The other end presses the slider 30 at point P. 39 is a temporary spring for holding the slider 30, one end of which is fixed to the A part of the pressing spring 40, and the other end fixed to the B part of the mirror holder 29. As shown in FIGS. 1 and 2, the temporary spring 39 has a protrusion T at the portion fixed to the mirror holder 29, and the slider 30 is centered around point P due to the elasticity of the protrusion T and the leaf spring 39. The degree of freedom is given in the direction of rotation. The transfer table 4l has a pressing spring 40.1 spring 39, a main roller holder 29, and a slider 3.
0, objective lens 28. The polarizing mirror 27 is arranged to be moved in the radial direction of the optical disk medium 3l. Reference numeral 37 denotes a focus drive means, which drives the condenser lens 22 in the optical axis direction using the focus error signal to control the optical spot 32 so that it is always focused on the optical disc medium 3l. Further, 38 is a tracking drive means, which drives the trapezoidal prism 26 by the tracking error signal.
In this method, the angle of the emitted light beam 23 is slightly changed by rotating it in the D direction to control knocking.
Since the angle change of 3 is small, highly precise tracking can be performed. Additionally, since the objective lens does not move, the optical head can be made smaller, and multiple optical heads can be driven independently when configured in a stacked structure. In the above illumination, in the present invention, since the objective lens 7 is attached to the slider 30, the working distance M (WD in FIG. 1) is lowered to nearly 0, and the aperture can be adjusted without increasing the volume of the optical components. You can increase the number. Also,
The optical head can be miniaturized to the same level as the magnetic head, and the optical disk medium 31 can be made into a stacked structure, making it possible to improve mounting density and search speed. On the other hand, when the slider 30 is floated above the optical disk medium 3l as shown in FIG. 4, a yawing phenomenon occurs in which the slider 30 is scattered in the X direction or Y direction due to the surface deflection of the optical disk medium 3l and the vibration of the leaf spring 39. do.
However, since the center of pressure of the pressure spring 40 is placed approximately on the optical axis of the objective lens 7, even if the light spot 32 moves in the X or Y direction, there is little movement in the focus or tracking direction of the light spot 32. 32 can be stabilized. Further, by providing a pressing point approximately on the optical axis of the objective lens 7, the position of the deflection mirror 27 is stabilized, so that the deviation between the light beam 23 and the deflection mirror 27 is reduced, and the light spot 32 is stabilized. Furthermore, by arranging the objective lens 7 approximately at the center of the slider 30, the influence of the above-mentioned yawing can be further reduced. Further, in the center of the slider 30, there is relatively little disturbance in the air layer formed between the optical disc recording medium 3l and the slider 30, and there is little change in the refractive index due to atmospheric pressure fluctuations, so deterioration of aberrations can be reduced. Effects of the Invention According to the optical recording/reproducing apparatus of the present invention, it is possible to reduce fluctuations in the optical spot due to the yawing of the floating optical head and aberrations due to fluctuations in air pressure in the floating space, thereby realizing a stable optical head. Furthermore, since highly accurate tracking control can be performed without attaching a trunking drive means to the transfer stage, it has become possible to miniaturize the optical head and create a stacked structure for optical disk media. Furthermore, by switching to floating type light, it is possible to increase the numerical aperture of the objective lens. Therefore, it is possible to improve device density and search speed, which were major issues in optical recording and reproducing devices.

[Brief explanation of drawings]

1 is a principle diagram of an optical recording/reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a view taken in the direction of arrow C in FIG. 1, and FIG. Figure 4,
FIG. 5 is an explanatory diagram of the optical head in the embodiment, and FIG. 6 is a diagram of the principle of a conventional optical head. 21...Semiconductor laser, 22...Condensing lens, 23...Optical beam, 24...
Polarizing beam splitter, 26... Trapezoidal prism, 27... Deflection mirror, 28... Objective lens, 30... Slider 31...
Optical disk medium, 32... Light spot, 37.
...Focus drive means, 3 days...Tracking drive means, 40...Press spring, 4l.
...transfer table.

Claims (1)

[Scope of Claims] (1) A laser light source, a condensing lens that condenses the light emitted from the laser light source, a mirror that deflects the condensed light beam in the direction of an optical disk medium, and a an objective lens that converges on the optical disk medium, a slider floating above the optical disk medium and equipped with the mirror and the objective lens, a pressing means for pressing the slider against the optical disk medium, and separating light reflected from the optical disk medium. 1. An optical head comprising a light separating means for detecting the separated reflected light and a light detecting means for receiving the separated reflected light, the optical head being characterized in that the pressing center of the pressing means is provided approximately on the optical axis of the objective lens. (2) The optical head according to claim (1), wherein the slider is provided with an opening, and an objective lens is attached to the opening. (3) The optical head according to claim (1), wherein the objective lens is provided approximately at the center of the slider. (4) A laser light source, a condensing lens that condenses the light emitted from the laser light source, a mirror that deflects the condensed light beam in the direction of the optical disk medium, and a condensing lens that converges the light beam onto the optical disk medium. an objective lens, a slider floating above the optical disc medium and equipped with the mirror and the objective lens, pressing means for pressing the slider against the optical disc medium, and light separation means for separating reflected light from the optical disc medium; A light detection means for receiving the separated reflected light and a prism having two non-parallel surfaces located between the condenser lens and the mirror are provided, and tracking is controlled by rotating this prism. light head. (5) a laser light source, a condensing lens that condenses the light emitted from the laser light source, and a light separation means that separates the condensed light beam from the reflected light from the optical disk medium;
a mirror that fixes the light detection means that receives the separated reflected light, and deflects the focused light beam in the direction of the optical disk medium; an objective lens that focuses the light beam on the optical disk medium; and the optical disk medium. An optical head in which a slider floating upward and equipped with the mirror and the objective lens, and a pressing means for pressing the slider against the optical disk medium are movable in the radial direction of the optical disk medium. (6) The focus of the light beam converged on the optical disk medium is controlled by moving the condensing lens in the optical axis direction. light head.