JPS6259371B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording device for optically recording and reproducing information.

First, a conventional optical recording/reproducing apparatus of this type will be explained with reference to FIG.

In FIG. 1, 1 is a light source, 2 is a half mirror, 3 is a movable mirror, 4 is a condenser lens, 5 is an information recording disk, and 6 is a photodetector.

When recording with the apparatus shown in FIG. This is done by condensing the light and forming a minute spot on the information recording disc 5. The smaller the diameter of the minute spot, the higher the power density, and the better recording becomes possible. In order to reduce the micro spot diameter using the condenser lens 4, it is necessary to make maximum use of the numerical aperture (NA) of the condenser lens 4, and for this purpose, it is necessary to maximize the numerical aperture (NA) of the condenser lens 4. It is necessary to make it incident.

When reproducing information recorded on the information recording disc 5 in this way, the light from the light source 1 is focused on the information recording disc 5 via the half mirror 2, the movable mirror 3, and the condensing lens 4. Condensing lens 4 for reflected light
The light is reflected by the movable mirror 3 through the mirror 2, and then reflected by the half mirror 2 and incident on the photodetector 6.

In such a reproduction state, in order to sequentially reproduce the information recorded on the information recording disc 5, it is necessary to make the light spot follow the recording pit on the information recording disc 5, and for this purpose, the movable mirror 3 is moved slightly. Rotate and apply tracking servo. For example, the movable mirror 3 is slightly rotated as shown by the broken line in FIG. 1, but the optical system shown in FIG. Therefore, when the movable mirror 3 rotates slightly, the light reflected by the movable mirror 3 is deflected as shown by the broken line, and a part of the reflected light no longer enters the condenser lens 4. Therefore, the intensity and light amount balance of the light incident on the photodetector 6 changes in accordance with the rotation of the movable mirror 3. Focus servo and tracking servo are performed by detecting subtle changes in the light incident on the photodetector 6, but as mentioned above, some of the light reflected by the movable mirror 3 is incident on the condenser lens 4. If it runs out, there is a drawback that the operation of the servo system becomes unstable.

The present invention eliminates the above-mentioned conventional drawbacks, and provides an optical recording and reproducing device that can perform good recording by making light incident on the full aperture of the condensing lens during recording, and provides a stable reproduction state during reproduction. An embodiment of the present invention will be described below with reference to FIGS. 2 and 3. In FIG. 2, the same parts as in FIG. 1 are given the same numbers.

The feature of this embodiment is that, as shown in FIG. 2, a light shielding plate 8 having a hole 7 formed therein is provided between the light source 1 and the half mirror 2, as shown in FIG. 3, so that it can be inserted and removed. The light shielding plate 8 is not interposed in the optical path during recording, but the light shielding plate 8 is interposed in the optical path during reproduction. The diameter of the hole 7 of the light shielding plate 8 is smaller than the diameter of the beam of light from the light source at the position of the light shielding plate 8.

According to this embodiment, during recording, the condenser lens 4
The light is incident on the full aperture of the lens, allowing good recording to be performed, and during playback, the light shielding plate 8 is interposed in the optical path to reduce the diameter of the light beam, which reduces the diameter of the light beam to the condenser lens 4, as shown in FIG. As shown by the broken line in , even if the movable mirror 3 rotates slightly, part of the light reflected by the movable mirror 3 will not be incident on the condenser lens 4, regardless of the rotation of the movable mirror 3. This has the advantage that the amount of light to the photodetector 6 and the balance of the amount of light are constant, and stable servo operation can be performed.

Note that insertion and removal of the light shielding plate 8 into and out of the optical path can be controlled using a plunger or the like.

The present invention has the above configuration, and has the advantage that stable servo operation during good recording and reproduction is possible.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a conventional optical recording/reproducing device.
FIG. 2 is a schematic diagram of an optical recording/reproducing device according to an embodiment of the present invention, and FIG. 3 is a perspective view of a light shielding plate of the device. 1... Light source, 2... Half mirror, 3... Movable mirror, 4... Condensing lens, 5... Information recording disk,
6... Photodetector, 7... Hole, 8... Light shielding plate.

Claims (1)

[Claims] 1. A light source, a half mirror that allows the light from the light source to pass through, a movable mirror that reflects the light that has passed through the half mirror, and a condenser that collects the light reflected by the movable mirror to form a minute spot on the information recording disk. An optical recording/reproducing device comprising: a light lens; and a photodetector for detecting light reflected by the information recording disk and reflected by the movable mirror and the half mirror via the condensing lens; a light shielding plate provided in an optical path between the half mirror and having a hole formed therein with a diameter smaller than a diameter of a beam of light from the light source, and selecting the light shielding plate in the optical path according to a recording/reproduction mode. 1. An optical recording and reproducing device comprising means for intervening.