JPH0196834A - Optical information recording and reproducing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an optical information recording/reproducing apparatus using an optical disk, magneto-optical disk, etc. as an information recording medium.

BACKGROUND OF THE INVENTION Generally, an optical pickup in this type of optical information recording/reproducing apparatus is constructed as shown in FIG. That is, linearly polarized light emitted from a semiconductor laser 1 as a light source becomes circularly polarized by passing through a collimating lens 2, a polarizing beam splitter 3, and a λ/4 plate 4, and is transmitted to an optical disk 6 as an information recording medium by an objective lens 5. A focused beam of light is irradiated onto the surface. Then, the reflected light from the surface of the optical disk 6 passes through the objective lens 5 again, and then passes through the λ/4 plate 4 again, thereby becoming linearly polarized light that is tilted by 90° with respect to the initial light. As a result, in the polarizing beam splitter 3, the light is reflected in a direction in which it is separated from the incident light by the polarizing plane 3a. The light is then deflected by a prism-like knife 8 while being condensed by the detection lens 7, and is irradiated onto the track detection light receiving element 9. Note that a focus detection light receiving element 10 is provided in the straight direction of the knife 8. In other words, it is of the knife type, and the knife 8 separates it into focus detection light and track detection light. This is true not only for reflection intensity reading type discs but also for Kerr rotation angle reading type discs such as magneto-optical disks.

However, the conventional knife method requires fine adjustment when assembling the knife 8, and is generally not suitable for mass production. Furthermore, optical components such as the polarizing beam splitter 3, the detection lens 7, and the knife 8 are spatially separated, and the effects of reflection, scattering, etc. cannot be ignored, resulting in poor light utilization efficiency. To avoid this, each optical component needs an anti-reflection coating, which is expensive. Furthermore, according to the conventional Knifezi method, when the focal point position changes, the amount of light that reaches the track detection light receiving element 9 also changes. However, since tracking deviation is detected based on the distribution of light in the cross section, such a change in the amount of light due to a change in the focal position is undesirable.

Purpose The present invention was made in view of the above points.
It is an object of the present invention to provide an optical information recording/reproducing device which can realize a knife system that is easy to adjust and is inexpensive, and can also detect track deviation without being affected by changes in focal position.

Structure In order to achieve the above object, the present invention provides an optical information recording and reproducing apparatus that records or reproduces information by irradiating light from a light source onto an information recording medium, in which reflected light containing information from the information recording medium is emitted from the information recording medium. A first condensing grating that condenses a portion of the light onto the focus detection light receiving element, and a knife protruding into the condensing optical path of the condensing grating to condense the remaining part of the reflected light onto the track detection light receiving element. The present invention is characterized in that a second light condensing grating is integrally provided with a transparent member interposed therebetween.

A first embodiment of the present invention will be described below with reference to FIGS. 1 to 5. The basic configuration is similar to that shown in FIG. 7, and the same parts are indicated by the same reference numerals. Roughly speaking, in place of the detection lens 7 and the knife 8, a knife optical system is constructed using two condensing gratings 11, 1.2. These condensing gratings 11 and 12 are rectangular transparent members 1.
It is integrated by being loaded on both sides of 3.

Here, the first condensing grating 11 is formed in such a size that the lower half of the information-containing light reflected from the optical disk 6 and separated from the incident light by the polarizing beam splitter 3 can be incident thereon. Further, the second condensing grating 12 is disposed on the other side of the transparent member 13 on the upper half side opposite to the first condensing grating 11, so that the upper half of the reflected light can enter. It is configured. Both of these condensing gratings 11, 12 are formed identically. Specifically, it is configured as a condensing holographic grating, and the grating shape is curved, for example, as shown in FIG. 3, and has a condensing function. Such a structure may be of a refractive index distribution type or a surface relief type, but for example, if it is a surface relief type, the grating cross-sectional shape will be as shown in FIG.

Next, the positional relationship of the condensing gratings 11, 12, etc. will be explained. First, a focus detection light receiving element 10 is disposed at the focal position of the diffracted light by the first condensing grating 11. At this time, such a first
The second condensing grating 12 reaches a central position in the optical path of the diffracted light by the condensing grating 11.
The positional relationship is set so that the edge protrudes and acts as a knife edge. That is, the second condensing grating 12 functions to block the diffracted light from the first condensing grating 11. On the other hand, a track detection light receiving element 9 is disposed at the focal position of the diffracted light by the second condensing grating 12.

The transparent member 13 loaded with the first and second condensing gratings 11 and 12 in this manner is integrally attached to the reflected light exit side surface of the polarizing beam splitter 3 via the coupling portion 14 . This joint portion 14 is shown in FIG. 5(a).
The connecting member IS as shown in the figure (b) may also be used.
The polarizing beam splitter 3 and the transparent member 13 may be bonded together using a transparent adhesive 16 as shown in FIG.

As such adhesive 16, a thermosetting adhesive, an electromagnetic wave curing adhesive, or the like is used.

In any case, according to this embodiment, the conventional detection lens,
Instead of the knife, a transparent member 13 in which the first and second condensing gratings 11 and 12 are integrally mounted is integrally attached to the polarizing beam splitter 3, thereby enabling focus detection and tracking by the knife method. Detection can be performed. Such a knife detection system is extremely inexpensive compared to conventional systems, and since the optical components are integrated, it is easy to assemble and adjust. Furthermore, the detection light receiving element 9 for the truck
Only the second condensing grating 12 is involved in the amount of light for the track detection light receiving element 9 even if the focal position shifts. As a result, a correction circuit or the like is not required in the track detection system, and the track detection circuit can be further simplified.

A second embodiment of the present invention will be explained with reference to FIG.

In the above embodiment, the first and second condensing gratings 11.1
2 are exactly the same and their focal lengths are also the same, but in this embodiment, these first and second condensing gratings 11.
By making the focal lengths of the transparent members 12 different by a predetermined amount, the light receiving elements 9 and 10 can be disposed on the same surface of the transparent member 17. This transparent member 17 is the transparent member 1
The three surfaces are integrally connected via a connecting part 18 similar to the connecting part 14. According to this, even the light receiving element portion can be integrated.

Effects Since the present invention is configured as described above, it is possible to create a knife-type detection system using a grating that is much cheaper than a conventional knife-type grating, and such a grating can be integrated using a transparent member. Therefore, it is easy to assemble and adjust, and since only the second condensing grating functions on the light receiving element for track detection and the focus system does not function, focal fluctuations occur. However, it can be made unaffected by this.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing a first embodiment of the present invention, and FIG.
The figure is a schematic side view of the transparent member, etc., Figure 3 is a front view of the grating, Figure 4 is its sectional view, Figure 5 is a vertical side view showing the structure of the joint, and Figure 6 is the second embodiment of the present invention. FIG. 7 is a schematic side view showing a conventional example. 2... Semiconductor laser (light source), 7... Optical disk (
information recording medium), 9... light receiving element for track detection, 1
o... Light receiving element for focus detection, 11... First condensing grating, 12... Second condensing grating, 13... Transparent member

Claims (1)

[Claims] In an optical information recording and reproducing apparatus that records or reproduces information by irradiating light from a light source onto an information recording medium, a part of the reflected light containing information from the information recording medium is focused on a focus detection light receiving element. a second condensing grating that protrudes as a knife edge into the condensing optical path of the condensing grating and condenses the remaining portion of the reflected light onto a track detection light receiving element; An optical information recording/reproducing device characterized in that: and are integrally provided via a transparent member.