JPS6134740A - Optical head - Google Patents

Abstract

PURPOSE:To use only one laser light source to reduce considerably the cost of a device by converging the luminous flux of a semiconductor laser near the apex of a pyramidical mirror in the center of a rotating drum and condensing it with one of plural object lenses. CONSTITUTION:Four objective lenses 4 are arranged at angular intervals of 90 deg. in a rotating drum 3 rotated by a motor 1, and a quadrangular pyramid mirror 8 which changes the direction of a luminous flux by 90 deg. is fixed in the center of them. The luminous flux from a semiconductor laser 9 provided on the outside of the drum 3 is converged near an apex 10 of the mirror 8 by a condenser lens 11. In this constitution, the luminous flux whose direction is changed by 90 deg. by one reflecting face of the mirror 8 is focused on a recording medium 7 by one objective lens 4 to perform recording or reproducing. Thus, only one expensive semiconductor laser light source is used to reduce considerably the cost of the device.

Description

[Detailed description of the invention] [Field of application of the invention] TECHNICAL FIELD The present invention relates to light for optical recording and reproduction.

[Background of the invention]

In conventional optical recording and reproducing devices, especially optical rotary head recording devices exclusively for optical recording, an optical head consisting of a semiconductor laser and an objective lens is mounted on a rotating drum.
One optical head is made up of several semiconductor lasers, and in the case of a multi-head system, the same number of semiconductor lasers as the number of heads are used.

Semiconductor lasers, especially high-output semiconductor lasers for recording, are expensive, and the problem is that the more semiconductor lasers are used, the more expensive the optical head becomes. Also,
In the so-called U-shaped helical scan method, the optical axis of two to four optical heads is precisely 180° to 90°.
It is necessary to install it on a rotating drum so that
There is also the problem that it is difficult to accurately position and mount all of the plurality of optical heads.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the cost of a multi-head type optical rotary head recording device by reducing the number of semiconductor lasers to one, thereby reducing the cost of the device, and to provide an optical head that can precisely position the optical heads. It is about providing.

[Summary of the invention]

In order to achieve the above object, an optical head according to the present invention includes a plurality of objective lenses mounted on a rotating drum, and a plurality of objective lenses fixed at the center of the rotating drum and having a number of reflective surfaces equal to the number of objective lenses. A pyramidal mirror, the rotating drum, a semiconductor laser placed outside, and the semiconductor 17-
It was decided to include an optical means for converging the light beam emitted from the polygonal pyramid near the vertex of the polygonal pyramidal mirror.

[Embodiments of the invention]

1, below, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of an optical head according to the present invention. FIG. 2 is a side sectional view of the optical head.

In FIGS. 1 and 2, reference numeral 1 denotes a motor. A rotating drum 3 is fixed to the end of a shaft 2 which is rotated as appropriate by the motor 1. On the opposite side of the rotating drum 3 to the shaft 2, four The objective lens 4 and the light transmitting section 3a are easily arranged on the optical axis with exact 90° symmetry. On the outer periphery of the rotating drum 3, there are rows 25,
An optical recording medium 7 in the form of a tape (or card) is appropriately run through the recording medium 6 . Finally, a four-sided pyramidal mirror 8 that changes the direction of the light beam by 90 degrees is fixed at the center of the rotating drum filter. On the other hand, a semiconductor laser 9 is located at a location other than the rotating drum 3.
A converging lens 11 that converges the light beam emitted from the semiconductor laser 9 near the apex 10 of the quadrangular pyramidal mirror 8 is arranged along an extension of the axis 2 of the rotating drum 6.

Next, the operating principle will be explained. The light beam emitted from the semiconductor laser 9 is condensed by a condenser lens 11 and focused near the apex of the quadrangular pyramidal mirror 8 . The focus should be placed at a position slightly offset from the center of the rotating drum. In this case, the light beam whose direction is changed by 90 degrees by one reflecting surface of the quadrangular pyramidal mirror 8 and becomes a diverging light beam is condensed by one of the four objective lenses 4, and the rotation of the rotating drum 3 causes the light beam to become a divergent beam. As the recording medium 7 travels, information is recorded (or reproduced) with a focus on the recording layer of the optical recording medium 7.

Every time the rotating drum 3 rotates 90 degrees, the reflecting surface of the quadrangular pyramidal mirror 80 on which the light beam enters changes one after another, so the tape-shaped optical recording medium 7 is simply mounted over the outer circumference of the rotating drum 6 over a range of 90 degrees. Therefore, information can be recorded (or reproduced) on the entire surface of the optical recording medium 7.

〔Effect of the invention〕

As described above, according to the optical head of the present invention, a plurality of optical heads are configured with one semiconductor laser, so that regardless of the number of heads, especially in the case of a multi-head system, the number of semiconductor lasers can be reduced. Only one head is needed, and the positioning between the optical heads becomes easier and more accurate. Especially in the case of recording optical heads that use expensive high-output semiconductor lasers, the price is significantly reduced. .

[Brief explanation of drawings]

FIG. 1 is a plan view of an optical head according to an embodiment of the present invention, and FIG. 2 is a side sectional view of the optical head.

Claims (1)

[Claims] 1. Multiple objective lenses mounted on a rotating drum,
A polygonal pyramidal mirror fixed at the center of the rotating drum and having a number of reflecting surfaces equal to the number of objective lenses; a semiconductor laser disposed at a location other than the rotating drum; An optical head characterized by comprising an optical means for converging near the apex of a pyramidal mirror.