JPH0821174B2 - Optical head device - Google Patents

Description

The present invention relates to an optical head device for irradiating an information carrier with light to optically record and / or reproduce information.

[Prior Art] In recent years, compact discs in which digitized audio is recorded on the surface of unevenness and video discs in which TV images are recorded have been remarkably spread.

In particular, compact disc players are expected to expand from stationary types to portable types that can be carried around freely, or to in-vehicle players.

These optical information recording / reproducing devices are required to be thin, small, and inexpensive as demands from the user side, and therefore, similar demands are also made on the optical head device for recording or reproducing information on the information carrier as described above. It is getting bigger.

Hereinafter, a conventional optical head device will be described with reference to the drawings.
FIG. 4 is a schematic side view of a conventional optical head device.

As shown in the figure, the divergent light beam emitted from the laser diode 2 which is a light source becomes a parallel light beam by the collimator lens 4, passes through the beam splitter 6, and changes its traveling direction by 90 ° by the total reflection prism 8. And
The light is focused on the surface of the disk 14 by the objective lens 12 which is supported by the actuator 10 so as to be movable in the focusing direction and the tracking direction.

The light beam reflected on the surface of the disk 14 passes through the objective lens 12 and the total reflection prism 8 and is redirected by the beam splitter 6 in the direction perpendicular to the paper surface in FIG.

Next, description will be made with reference to FIG. FIG. 5 is a view of FIG. 4 seen from the direction of arrow A.

As described above, the light beam whose traveling direction is changed by the beam splitter 6 passes through the sensor lens 16 and the cylindrical lens 18, and is condensed on the surface of the sensor 20.

In the above description, the actuator 10 is slidable in both the focusing direction and the tracking direction. In the conventional servo signal detection method, the focusing error signal detection method is the astigmatism method, and the tracking error signal detection method is the push-pull method.

In the above-described optical head device, since the actuator holding the objective lens can move by sliding in both the focusing direction and the tracking direction, the response characteristic of the lens is good and high-speed random access is possible.

[Problems to be Solved by the Invention] However, in the conventional optical head device as described above, when considering the height of the entire device, the height of the actuator and the total reflection prism, the beam splitter, the sensor lens, and the cylindrical lens are used. It is absolutely necessary to add the height of optical components such as the above, and even if efforts are made to reduce the thickness, the limit is usually about 20 mm.

[Object] The present invention has been made in view of the problems of the above-described conventional art, and an object of the present invention is to provide an optical head device which can be made thinner and more compact than the conventional optical head device.

[Means for Solving the Problems] According to the present invention, the above-mentioned object is reflected by a light source, an actuator provided with an optical system for condensing a luminous flux emitted from the light source on an information carrier, and the information carrier. In an optical head device having a photodetector for detecting a light beam, by irradiating the light beam emitted from the light source toward the information carrier and transmitting the light beam reflected by the information carrier, A beam splitter that separates a reflected light beam from the irradiation light beam is disposed inside the actuator, and a light beam that has passed through the beam splitter is guided to the photodetector in an optical path between the beam splitter and the photodetector. An optical waveguide element is provided, the optical path from the light source to the beam splitter and the optical waveguide element are arranged substantially in parallel, and the photodetector is the actuator. Is provided on the same side as the light source with respect to the optical head device.

[Embodiment] An embodiment according to the present invention will be specifically and specifically described below with reference to the drawings.

FIG. 1 is a schematic sectional view showing an embodiment of an optical head device according to the present invention.

As shown, the optical head device 22 according to the present invention has a laser diode 24 which is a light source. The divergent light beam emitted from the laser diode 24 is collimated by a collimator lens 26 as shown in the figure. The light flux collimated by the lens 26 enters the inside of the main body 28 of the optical head device 22 through an opening 30 provided in the main body. The main body 28, the laser diode 24, and the collimator lens 26 are supported and fixed by fixing means (not shown) so that their relative positions do not change.

A beam splitter 32 and an actuator 34 are provided inside the main body 28 as shown in the figure. The actuator 34 is composed of a tracking movable member 36 and a focusing movable member 38 as shown in the drawing. An objective lens 40 is fixedly held on the focusing movable member 38. The beam splitter 32 is arranged inside the actuator 34 as shown. The beam splitter
Numeral 32 is constructed so that a part of the light flux from the laser diode 24 side is reflected in the right angle direction, and a part of the light flux reflected from the disk 42 side passes through as it is.

The optical head device 22 of this embodiment has two openings 30 and 44 provided in the main body 28 and notches provided in a tracking movable member 36 and a focusing movable member 38, which will be described later, respectively, in order to secure a passage of a light beam. And parts 58 and 64. Further, as shown in the drawing, an optical waveguide element 46 is fixed to the lower end of the main body 28. A diffraction grating 48 is provided in the optical waveguide element 46. The light flux reflected on the surface of the disk 42 passes through the objective lens 40 and the beam splitter 32, passes through the opening 44, is diffracted by the diffraction grating 48, and is totally reflected within the optical waveguide element 46 several times, and then the sensor 50. Focus on top.

In the present embodiment, the servo signal detection method is the focusing error signal detection method is the knife edge method, and the tracking error signal detection method is the push-pull method.

Next, the tracking movable member 36 and the focusing movable member 38 will be described with reference to FIGS. 2 and 3.

2 is a perspective view of the tracking movable member 36, and FIG. 3 is a perspective view of the focusing movable member 38.

In FIG. 2, the tracking movable member 36 has a main body 54 in which a through hole 52 is arranged in the central portion. As shown in the figure, coils 56a and 56b for tracking control are wound around both ends of the main body in the horizontal direction with the through hole 52 interposed therebetween. Further, in the vicinity of the through hole 52 of the main body 54, a cutout portion 58 for passing a light flux is provided.

In FIG. 3, the focusing movable member 38 has a lens barrel 60 at the center. An objective lens 40 is provided near the upper end of the lens barrel. Further, the focusing control coils 62a and 62b are provided at both ends in the horizontal direction of the lens barrel 60.
Is provided. Further, similarly to the above-mentioned cutout portion 58, the lens barrel 60 is provided with a cutout portion 64 for passing a light beam.

Then, in the optical head device 22, the lens barrel of the focusing movable member 38 is provided in the through hole 52 portion of the tracking movable member 36.
It is provided in a state where 60 parts are slidably fitted together.

The above is the description of the embodiment of the optical head device according to the present invention.

In the optical head device of the present invention configured as described above, the height of the entire device is the sum of the height of the actuator and the thickness of the optical waveguide element, so that it can be thinned to about 10 mm.

Further, since the actuator is of the sliding type, the response characteristics are good, and since no resonance mode occurs, high speed random access is possible.

[Effects of the Invention] As described in detail and specifically above, in the optical head device of the present invention, the beam splitter is arranged inside the actuator, and the detection optical system is composed of an optical waveguide element. The height of the entire device can be set to about 10 mm, and a thin optical head device can be provided. Further, since the optical path from the light source to the beam splitter and the optical waveguide element are arranged substantially in parallel, and the photodetector is arranged on the same side as the light source with respect to the actuator, the optical head is very compact in the horizontal direction as well. A device can be provided.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of an optical head device according to the present invention, FIGS. 2 and 3 are perspective views of a tracking movable member and a focusing movable member, respectively, and FIG. 4 is a conventional optical head device. FIG. 5 is a schematic side view of FIG.
It is the figure seen from the direction. 22 …… Optical head device 24 …… Laser diode 32 …… Beam splitter 34 …… Actuator 42 …… Disk 46 …… Optical waveguide element 50 …… Sensor

Claims (1)

[Claims] 1. Light comprising a light source, an actuator provided with an optical system for condensing a luminous flux emitted from the light source on an information carrier, and a photodetector for detecting the luminous flux reflected by the information carrier. In the head device, the actuator includes a beam splitter that separates a reflected light flux from the information carrier from the irradiation light flux by reflecting a light flux emitted from the light source toward the information carrier and transmitting a light flux reflected by the information carrier. Placed inside the
And in the optical path between the beam splitter and the photodetector, has an optical waveguide element that guides the light flux transmitted through the beam splitter to the photodetector, and an optical path from the light source to the beam splitter. An optical head device, wherein the optical waveguide elements are arranged substantially in parallel, and the photodetector is arranged on the same side as the light source with respect to the actuator.