JPS63209036A - Optical head - Google Patents

Abstract

PURPOSE:To make automatic focusing of a semiconductor laser in a laser non- oscillating state possible by mounting an optical head on a slider and making the slider closely float on an optical recording medium. CONSTITUTION:The optical head 21 is made to closely float on the optical recording medium 4. Namely, the optical head 21 is used mounted on the slider 24 set to a load spring 23 on an arm 22 which can move at high speed in a radius direction of the optical recording medium 4. Thus, the focusing control of the optical head 21 is kept in a certain spacing value which is decided with the load of the load spring 23, the shape and the weight of the slider 24 and the running speed of the optical recording medium 4. Since an optical output P varies in a period lambda/2 (lambda means a wavelength and a refractive index between an output end surface 33 and the optical recording medium 4 is n=1) against spacing (h), it is necessary to keep the spacing (h) corresponding to a crest part so as to detect a high quality data signal.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Utilization Public Expenses> The present invention relates to an ultra-small and low-cost optical head that utilizes the complex resonance effect of a semiconductor laser and an optical recording medium.

<Prior art and its problems> Conventionally, this straw-based optical head is described, for example, in Miyazawa et al.: "Semiconductor laser pickup for PCM deck", Electronic Materials, 9.67.
．． As reported in the February 1979 issue, it had the structure shown in Figure 6. That is, the emitted light from the semiconductor laser 1 passes through the coupling lens 2 and the condensing lens 3 and is focused onto the optical recording medium 4. The reflected light from the optical recording medium 4 is returned to the semiconductor laser 1 through an optical path opposite to that described above. The optical output in this case is detected by a photodetector i15 installed at the rear end of the semiconductor laser 1. 6 and 7 are wobbling elements for obtaining a focus error signal and a tracking error signal, and use, for example, a PZT element. The oscillators 8 and 9 drive the PZT elements 6 and 7 to slightly vibrate them in a direction perpendicular to the optical recording medium 4. The focus error signal and the tracking error signal are sent to phase detectors 10 and 1.
1 by phase detection of the feedback light.

In the figure, 12 is a support spring, 13 is a focus control actuator, and 14 is a track control actuator.

As mentioned above, in conventional optical heads, when reproducing information, the semiconductor laser is always in a laser oscillation state, and the focusing lens 3
It was necessary to slightly vibrate the lens to obtain a focus error signal, and use this focus error signal to drive a focus control actuator to perform focus control. For this reason, conventional optical heads require mechanical parts such as focus control actuators in addition to optical parts such as the condenser lens 3 and photodetector N5, making the optical head large and making it difficult to reduce costs and improve reliability. There was a drawback.

<Objective of the Invention> An object of the present invention is to attach an optical head to a slider and levitate the slider close to an optical recording medium, thereby making it possible to automatically focus a semiconductor laser in a non-laser oscillation state. Our goal is to provide an ultra-compact, low-cost, and highly reliable optical head.

Means for Solving the Problems> In order to achieve the above object, the present invention floats the optical head 21 close to the optical recording medium 4 as shown in FIG. 1(a). That is, the optical head 21 is used by being attached to a slider 24 attached to a load spring 23 on an arm 22 that can move at high speed in the radial direction of the optical recording medium 4.

Thereby, the focus control of the optical head 21 is maintained at a constant spacing value determined by the load of the load spring 23, the shape and weight of the slider 24, and the running speed of the optical recording medium 4.

<Example 1> Figures 1(a), (b), and (c) show a first example of the present invention. 3A is a diagram of the optical head in use, FIG. 1B is a configuration diagram of the optical head, and FIG. 10A is another configuration diagram of the optical head. In the figure (b), the optical head 21 is divided into the semiconductor laser 1 and the photodetector I15 by a separation groove 32 having a depth of several μm that reaches the substrate 31. 33 is an output end face, 34 is an active layer, 35 is an insulating layer, 36 is a semiconductor laser electrode, 37 is a photodetector electrode, 38 is a light receiving part, and 39 is a common electrode. A light beam 40 from the semiconductor laser 1 is reflected by the optical recording medium 4, a reflected light 41 returns to the semiconductor laser 1, and the light output (composite resonance signal output) 42 at that time is detected by the light receiving section 38. In the same figure (C), a waveguide lens section 50 is arranged at the tip, and it is possible to reduce the light beam spot 51 on the optical recording medium 4 and improve the recording density. tk
Ru. Reference numeral 52 denotes a buffer layer 53 (which forms the waveguide lens section 50) with an etched mirror surface formed using microfabrication technology.
for example to Si), waveguide layer 54 (for example to glass 7059), waveguide layer 54 (for example to glass 7059
). A Luneburg lens 55 is made of a dielectric material (for example, 5t-N) with a higher refractive index than the waveguide layer 54, and has a circular circumference and a semicircular surface. The operation is the same as in (b).

This result 1. In response to changes in the reflectance of the optical recording medium 4 (presence or absence of information bits), the optical output 42 changes as shown in FIG. 2(a). obtain. Light output and spacing at this time (output end surface 33
The relationship between and the distance l1l)h of the optical recording medium 4 is shown in Figure 3(a).
p (b) d.

弽) is an enlarged view of (a). From the figure, (1) the optical output P decreases rapidly as the spacing h increases.

(2) Optical output P is period λ/2(λ
is the wavelength, and the refractive index between the output end face 33 and the optical recording medium 40 is n.
; Changes in 1).

I understand that.

Therefore, in order to detect a high quality data signal, it is necessary to maintain the semiconductor laser 1 and the optical recording medium 4 at a spacing h corresponding to the peak in FIG. Note that the spacing h depends on the dimensions, shape, weight, and load spring 2 of the slider 24.
3, and depends on the running speed of the optical recording medium 4, etc.

<Embodiment 2> FIG. 4 shows an optical head according to a second embodiment of the present invention. This optical head assumes a phase change rewrite medium as an optical recording medium, and 4o-1 is an erasing light beam, 40-2 is a recording light beam, and 40-3 is a reproduction light beam. The myopic image of the erasing light beam is an ellipse with an axial ratio of about 10:1,
The myopic images of the recording light beam and the reproduction light beam are circles with an axial ratio of approximately 1:1.

While erasing with the front elliptical light beam, recording is performed with the middle circular light beam, and reproduction is performed with the rear circular light beam. This makes it possible to simultaneously override information and check the reading of recorded information, and by combining this optical head with a phase-transformable rewriting medium, an extremely high-performance optical recording/reproducing device can be realized.

Such multiple light beams are realized by dividing the laser beams 60 having a width and depth of several μm and condensing the emitted light from the semiconductor laser 1 with a waveguide lens 61, respectively. Furthermore, three photodetectors 5 are created using the insulating grooves 32. Note that 36-1, 36-2 and 36-3 are electrodes of the semiconductor laser, 37-1, 37-2 and 37-3 are electrodes of a photodetector, and 39 is a common m-pole. Also, 38-1,
38-2 and 38-3 are light receiving sections of the respective photodetectors. These insulators are created on the semiconductor laser substrate by, for example, reactive ion beam etching. Note that the semiconductor laser 1, the photodetector Wi5, and the waveguide lens 61 may be separate components.

<Embodiment 3> FIG. 5(a) shows another embodiment of the optical head according to the present invention. The difference from FIG. 1(b), (C1 and FIG. 4) is that an anti-reflection film 70 is formed on the output end face 33 of the optical head 21. Such an anti-reflection film M70 is formed by, for example, using a transparent dielectric material thickly. This is realized by forming the wavelength as λ/4n (λ is the wavelength and n is the refractive index).

FIG. 5(b) shows the signal component Sp depending on the presence or absence of the antireflection film 70.
p and noise town 1. This is a comparison. The vertical axis is sp, = p'
-pL (see FIG. 2(b)) ' NPIII is the integral value of the noise component from band 30 to 20 MHz. The horizontal axis is the ratio between the semiconductor laser wAII+current ■ and the threshold value ■\ in the case of no optical feedback (no optical recording medium). Spacing is 2.9 μm.

The reflectance of the output end face 33 is 0.0 without the antireflection film 70.
32, if there is an antireflection film 70, it is O, OS. As shown in the figure, by forming the antireflection film 70, the signal component S□ increases rapidly, whereas the noise N0. It can be seen that there is a slight increase in Therefore, by adding an anti-reflection film, the SN of the data signal can be reduced.
It can be seen that the ratio is significantly improved.

<Effects of the Invention> As explained above, the optical head according to the present invention has optical parts integrated, and is mounted on a slider and used while floating close to the optical recording medium due to air lubrication. ,
It is ultra-compact and low-cost because it does not require a focus control actuator. Furthermore, since the flying height is set to a distance where the signal becomes large and the signal is amplified by the anti-reflection film, there is an advantage that the signal quality during information reproduction is high.

[Brief explanation of the drawing]

1(a) is a perspective view showing an optical head that flies close to each other and moves at high speed; FIGS. 1(b) and (c) are perspective views showing an example of the structure of the optical head of the present invention, al (b) is a principle diagram of signal detection by complex resonance action, and Fig. 3 (1
m) (b) is a graph showing the relationship between the optical output and spacing of the optical head of the present invention, and its enlarged view; FIG. 4 is a perspective view showing another example of the structure of the optical head of the present invention; Figure (a
) is a perspective view showing still another example of the structure of the optical head of the present invention, FIG. 5(b) is a graph showing the relationship between signal component and noise, and FIG. FIG. 3 is a configuration diagram of a head. In the figure, 1 is a semiconductor laser, 4 is an optical recording medium, 5 is a photodetector, 31 is an optical head, 32 is an insulating groove, 33 is an output end face, 38 is a light receiving part, 40 is a light beam, 41 is reflected light, 42 is an optical output, 61 is a waveguide lens, 70 is an antireflection film, and h is a spacing.

Claims (2)

[Claims] (1) An optical recording medium is placed on one output end face of a semiconductor laser, and a photodetector is placed on the other output end face, and the reflected light from the optical recording medium is returned to the semiconductor laser, and information is reproduced by a complex resonance effect. 1. An optical head of a floating type near an optical recording medium, characterized in that a distance h between one output end face of a semiconductor laser and an optical recording medium is set to a value approximately expressed by the following formula. h=(N/2n)λ where λ is the oscillation wavelength, n is the refractive index of the medium between the semiconductor laser and the optical recording medium, and N is a positive integer. (2) The optical head according to claim 1, wherein an antireflection film is formed on the output end face of the semiconductor laser on the optical recording medium side.