JPS6319937B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical scanning device that optically and non-contact reads information recorded at high density on a tape or a rotating disk.

Generally, a drawback of this type of optical scanning device is that the light spot for reading information cannot be traced along a specific track due to disturbances such as vibration and eccentricity that occur when the rotating disk rotates.

Conventionally, in order to eliminate the above-mentioned difficulties, an optical scanning device using the wobbling method described below has been proposed.

The above-mentioned optical scanning device using the wobbling method causes a light spot irradiated on an information track on a rotating disk to vibrate minutely at a single frequency in a direction perpendicular to the direction of the information track. It consists of a device that performs synchronous detection by extracting the same frequency component as the vibration from the changes in the reproduced signal that occurs, and the magnitude of the synchronous detection output corresponds to the absolute amount of deviation of the optical spot. The sign of the output corresponds to the direction of deviation of the light spot, and by detecting these and applying negative feedback, the deviation of the light spot from the information track is minimized.

In the optical scanning device described above, the frequency at which the light spot is oscillated on the track is such that when the light spot is scanned in an uncontrolled manner over a rotating disk, etc.
Since a value greater than the reciprocal of the time it takes for the light spot to cross the track is required, a frequency of several tens of kHz or more is normally required. Since this is done by vibrating the condensing lens using It is necessary to increase the length of the optical path to the optical lens, which has the disadvantage of increasing the size.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical scanning device with a small size and a large range of motion.

For this reason, the present invention provides the above-mentioned reproduction signal from a reproduced signal obtained by slightly vibrating a light spot irradiated onto an information track provided on an optical recording medium such as a rotating disk at a single frequency in a direction perpendicular to the direction of the information track. In an optical scanning device that extracts a signal having a single frequency component and minimizes the deviation of a light spot from an information track, a piezoelectric bimorph is supported at both ends by lenses that focus a light spot on an information track. It is characterized in that it is coupled to approximately the center of the vibrator, and the piezoelectric bimorph vibrator causes the lens to vibrate at a single frequency.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In the figure, 1, 1 is a piezoelectric bimorph vibrator,
Reference numeral 2 denotes a condenser lens that connects a light spot to a rotating disk (not shown); 3, 3 a rod that transmits the vibrations of the piezoelectric bimorph vibrators 1, 1 to the condenser lens 2; 4, the piezoelectric bimorph vibrators 1, 1, an outer frame that supports the condenser lens 2 and the rods 3, 3;
Reference numerals 5, . . . , 5 are connecting members between the piezoelectric bimorph vibrators 1, 1 and the outer frame 4, and 6 is an objective lens for collimating the light from a light source 7 such as a semiconductor laser.

The two piezoelectric bimorph oscillators 1, 1 that vibrate the condensing lens 2 are attached to the connecting members 5, . is transmitted to the condensing lens 2, and the condensing lens 2 is caused to vibrate by the vibration. That is, each piezoelectric bimorph vibrator 1 is supported by connecting members 5, 5 at both ends thereof, and the condenser lens 2 is fixed approximately at the center of both ends of each piezoelectric bimorph vibrator 1. It is supported by a rod 3.

The piezoelectric bimorph vibrators 1, 1 are made to vibrate at a frequency equal to the resonant frequency of the system formed by these piezoelectric bimorph vibrators 1, 1, condenser lens 2, etc.

On the other hand, the aperture of the objective lens 6 that converts the light from the light source 7 into parallel light beams is made larger than the aperture of the condenser lens 2, so that the light that enters the objective lens 6 from the light source 7 and becomes parallel is transmitted through the condenser lens. The light beam enters the condenser lens 2 as a light beam larger than the aperture of the condenser lens 2, and a light spot is imaged on an information track such as a rotating disk (not shown) provided at its focal position.

If the optical scanning device has the above configuration, the focal position of the condenser lens 2 will vibrate by the same distance in the vibration direction as the condenser lens 2 vibrates.
The position of the light spot will also vibrate in the same way.

At this time, the vibration frequency of the piezoelectric bimorph oscillators 1, 1 is made to match the resonance frequency of the system consisting of these piezoelectric bimorph oscillators 1, 1, condensing lens 2, etc., as described above, so The piezoelectric bimorph vibrators 1, 1 can apply vibrations with a sufficiently large displacement to the condenser lens 2.

In the above embodiment, since parallel light is incident on the optical axis of the condenser lens 2, the condenser lens 2
can use an inexpensive lens that does not require correction of off-axis aberrations. Of course, it goes without saying that the light spot can be vibrated even if the light is not parallel as described above.

According to the present invention, the condenser lens is supported at both ends and is coupled to the center of the piezoelectric bimorph resonator, which has a large displacement with a small volume. It is possible to apply large displacement vibrations to the condenser lens without tilting the optical axis, etc., and the protrusion from both ends of the piezoelectric bimorph oscillator of the condenser lens is also reduced, and the distance from the light source to the condenser lens is reduced. The optical path is shortened, the shape is much smaller than conventional optical scanning devices, the movable range is widened, the structure is simple, and the cost can be reduced.

[Brief explanation of the drawing]

The figure is a perspective view showing the structure of an optical scanning device according to the present invention. DESCRIPTION OF SYMBOLS 1... Piezoelectric bimorph resonator, 2... Condensing lens, 3... Rod, 4... Outer frame, 5... Connection member,
6...Objective lens, 7...Light source.

Claims (1)

[Claims] 1 A reproduction signal having the above-mentioned single frequency component is obtained by slightly vibrating a light spot irradiated onto an information track provided on an optical recording medium such as a rotating disk at a single frequency in a direction perpendicular to the direction of the information track. In an optical scanning device that extracts a signal and minimizes the deviation of a light spot from an information track, a lens that focuses a light spot on an information track is supported at approximately the center of a piezoelectric bimorph oscillator at both ends. an optical scanning device, characterized in that the piezoelectric bimorph vibrator is coupled to a piezoelectric bimorph vibrator to cause the lens to vibrate at a single frequency.