JPS6015828A - Pickup of optical recording device - Google Patents

Abstract

PURPOSE:To attain the incidence of a light beam in parallel with a focus lens at all times even at tracking by using a columnar prism as a means for moving slightly the light beam and adjusting an angle between the 1st reflecting face and the 2nd reflecting face of the columnar prism to 45 deg.. CONSTITUTION:The laser light irradiated from a laser light source 1 is made incident on a prism 10 from an incident face 11, reflected on the 1st reflecting face 12, reflected successively on the 2nd reflecting face 13 and irradiated from an irradiating face 14. The angle between the incident face 11 and the irradiating face 14 to 90 deg. and the angle between the 1st reflecting face 12 and the 2nd reflecting face 13 is 45 deg.. The irradiated light is deflected by 90 deg. to the incident light at all times independently of the incident angle of the laser light incident to a penta prism 10 in the optical system above. Thus, no error is caused in error detection.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field 1] The present invention relates to a pickup for an optical recording device, and more particularly to a pickup for an optical recording device having a tracking control system for an optical recording medium.

[Prior Art] An optical disk device is known as a typical optical recording device. Optical discs have tracks that are eccentric to the center of rotation of the disc, and rotate while shaking due to vibrations generated by the rotating means. It is necessary to make a light beam such as a laser beam follow minute fluctuations at any time. For this reason, conventionally, a single plane mirror was used to form the laser optical path, and this plane mirror was rotated slightly to make it follow the track.

That is, as shown in FIG. 1, a laser beam emitted from a laser light source 1 is reflected by a reflecting mirror 2, passes through a focus lens 3, and is made to enter an optical disk surface 4 perpendicularly. Incidentally, in an optical disk device, normally the above-mentioned tracking error and error in focusing of the laser beam on the optical disk surface are simultaneously detected and corrected. For this reason, a beam splitter 5 is arranged in the optical path to take out a part of the reflected light from the optical disk surface 4 and make it enter a detection means such as a photodiode 6. At this time, beam splitter 5 and photodiode 6 are used to detect the focus.
An astigmatism lens 7 is positioned between the two.

In such an optical system, the reflector 2 is used for trunking.
When the focus lens 3 is rotated, the laser beam will be obliquely incident on the focus lens 3, as shown by the dotted line in FIG. Since the astigmatism lens 7 is used to detect the error signal like a bipedal, this optical system becomes an astigmatism system, and therefore the light incident obliquely on the focus lens 3 is reflected on the photodiode 6 surface. One drawback was that the image formation position was shifted, resulting in an error when detecting an error signal.

[Object of the present invention] In view of the above-mentioned prior art, an object of the present invention is to provide an improved pickup for an optical recording device that can always make a light beam incident parallel to the optical axis of a focus lens even during tracking. With the goal.

[Embodiment of the present invention] Fig. 2 is a schematic diagram showing an embodiment of the present invention, in which numeral 1 is a laser light source, numeral 3 is a focus lens, and numeral 4 is an optical disk surface, as in Fig. 1. be. Note that the error detection section is omitted in FIG. 2. 10 is a pentaprism, and the laser beam emitted from the laser beam St i enters the prism 10 from the entrance surface 11, is then reflected by the first reflective surface 12, and then is reflected by the second reflective surface 13.
The light is reflected by the beam and is emitted from the emission surface 14.
Here, the angle between the input surface 11 and the output surface 14 is 90 degrees, and the angle between the first reflection surface 12 and the second reflection surface 13 is 4 degrees.
It is 5 degrees.

In such an optical system, no matter what the angle of incidence of the laser light entering the pentaprism 10, the emitted light is always deflected by 90 degrees with respect to the incident light. That is, as shown in FIG. 3, the emitted light always makes an angle of 90 degrees with the incident light, regardless of the incident angle α.

Therefore, as shown in FIG. 4, by rotating the pentaprism lO by a small angle using a voice coil or the like, the emitted light is moved in parallel, and the laser beam is always perpendicular to the focus lens 3, but only the incident position has moved slightly. Light is allowed to enter.

The movement control of the laser beam by the pentaprism 10 does not involve the rotation of the prism 10 as described above, but by slightly translating the prism 10 horizontally and/or vertically, as shown in FIGS. 5 and 6, for example. It can be achieved in the same way by forcing.

In the above, the term "pentaprism" has been used, but the entrance surface 11. It is clear that the outer shape does not have to be a pentagonal prism shape as long as the first reflecting surface 12, the second reflecting surface 13, and the exit surface 14 form an optical system as described above, and in such a case, the present invention also applies. shall be covered by the invention.

In addition, although the case where the angle between the entrance surface 11 and the exit surface 14 of the prism 10 is 90 degrees has been described, even if this angle is other than 90 degrees, especially if the angle is close to 90 degrees, the incident light and the output light will be A similar effect is obtained, except that the angle formed by the angle changes accordingly. That is, strictly speaking, the direction of the emitted light changes as the prism rotates, but in reality, the rotation angle of the prism is minute, so when the angle between the entrance surface 11 and the exit surface 14 is close to 90 degrees, The change in angle is negligible.

The pickup of the present invention is not limited to the above-mentioned optical disk device, but can be applied to any optical recording device having a control system that allows a light beam to follow a track on an optical recording medium.

[Effects of the present invention] As described above, according to the pink-up of the optical recording device according to the present invention, when following a track on the surface of an optical recording medium, a light beam is always made incident on the focus lens parallel to its optical axis. Therefore, no errors occur during error detection.

[Brief explanation of the drawing]

FIG. 51 is a schematic diagram of an optical system of a conventional pickup. 2, 3, 4, 5, and 6 are schematic diagrams of the optical system of the pickup according to the present invention. 1: Laser light source 2: Reflector 3: Focus lens 4: Light 7' isk surface 5: Beam splitter 6: Photo diode 7: Astigmatism lens 10: Pentaprism 11: Incident surface 12: First reflecting surface 13: Second reflective surface 14: Output surface Fig. 1 Fig. 2 Fig. 4 Fig. 5 @ Fig. 6 Fig. 3

Claims (2)

[Claims] (1) In a pickup of an optical recording device having a control system capable of causing a light beam to follow a track of an optical recording medium,
A columnar prism is used as a means for moving the light beam minutely, and the columnar prism is such that the light beam enters from an incident surface, is reflected by a first reflective surface, then a second reflective surface, and is emitted from an output surface. characterized in that the angle formed by the first reflective surface and the second reflective surface is substantially 45 degrees,
Optical recording device pickup. (2) A pickup for an optical recording device according to claim 1, wherein the angle formed between the entrance surface and the exit surface is substantially 90 degrees.