JPH0210529A - Optical head - Google Patents

Abstract

PURPOSE:To make the optical head miniaturized, light and thin structive by using an optical element for converting a cross section shape of an optical beam. CONSTITUTION:An incident light beam is reflected by splitting into >= 2 in one direction on an reflecting surface of the optical element 10 formed in a sequential stepped shape as the reflecting surface set up at a prescribed inclination, thus changing the conversion ratio of the direction of a major axis to the direction of a minor axis of the cross section shape of the optical beam. By this method, a shaping prism for shaping the major axial direction and the minor axial direction of the optical beam of an ellipse, etc., in length and suppressing a loss quantity of light can be out of use, and the constitution of the optical head which should have been in complicated constitution can be simplified, while the miniaturization with light weight and thin formation can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical reproducing device that optically reads information recorded on a disc such as a video disc, or to optically records information on a disc.

The present invention relates to an optical head used in a reproducing or erasing device.

2. Description of the Related Art In recent years, optical recording and reproducing devices have come to be used as external storage media for computers in the audio and video fields. First, an example of a conventional optical recording/reproducing device will be described.

Figure 8 shows the optical system of a conventional optical recording/reproducing device. 1 is a semiconductor laser, 2 is a collimating lens that converts the light emitted from the semiconductor laser into parallel light, and 3 is a beam-shaping lens. A shaping prism suppresses light loss; 4 is a polarizing beam splitter for guiding the light beam reflected from the disk and returned to the photodiode; 6 is a polarizing beam splitter for guiding the light beam reflected from the disk surface back to the semiconductor laser; A quarter wavelength plate prevents backtalk from occurring, and 6 is an objective lens that forms a beam spot of about 1 μm on the disk.

In the optical recording/reproducing device configured as above,
As shown in FIG. 9, the light beam emitted from the semiconductor laser 1 has a far-field pattern with a beam spread determined by the diffraction phenomenon, and the spread angle θ± in the direction perpendicular to the cemented surface is
The expansion in the direction parallel to the joint surface is approximately 2 to 3 times larger than the angle θl.
Become twice as large.

A collimating lens 2 is used to reduce the loss in the amount of light of this beam and make it a parallel beam. Furthermore, in an optical disk optical system that also performs recording, such as a recording/reproducing device, the loss of light amount from the light source to the recording surface becomes an important problem. Also, objective lens 6
If the intensity distribution of the light incident on the disk is not uniform, the beam spot cannot be narrowed down to a circular shape on the disk. Therefore, in combination with the shaping prism 3 that shapes the beam, loss of light amount can be suppressed.

This shaped beam is made incident on an objective lens. At this time, the incident beam having a Gaussian intensity distribution expressed by equation (1) is condensed by an objective lens to form a spot image as shown in FIG.

! (p) = exp (-2127w2) −
(1) If the objective lens is an aberration-free diffraction-limited lens, the spot radius W0 on the image plane is expressed by the following equation.

w0= K *λ/NA ・・・・・・
(2) K: Constant determined by the shape of the lens aperture and the intensity distribution of the cross section of the incident beam NA: Numerical aperture of the objective lens Problems to be solved by the invention However, the above configuration has the following problems. have.

After converting the beam emitted from a light source, such as a semiconductor laser, into parallel light, the optical head has a prism for shaping the cross-sectional shape of the elliptical beam into a circular shape and a total reflection mirror that changes the direction of the beam toward the disk. This was a big change in layout in response to miniaturization and thinning.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide an optical head for an optical recording/reproducing device that can be made small, lightweight, and thin.

Means for Solving the Problems In order to solve the above problems, the optical head of the present invention reflects an incident light beam on the reflection surface of an optical element in which the reflection surface is set at a predetermined angle of inclination and is sequentially formed in a step-like manner. By dividing the light beam into two or more parts in one direction for reflection, the conversion ratio between the long axis direction and the short axis direction of the cross-sectional shape of the light beam is changed.

Effect of the Invention With the above-described configuration, the present invention can eliminate the need for a shaping prism that suppresses light loss by shaping the lengths of a light beam such as an ellipse in the major axis direction and minor axis direction, and eliminates the need for a conventionally complicated configuration. The optical head configuration, which was previously difficult to achieve, can be simplified, and it can be made smaller, lighter, and thinner.

EXAMPLE Hereinafter, an optical head for an optical recording/reproducing apparatus according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows an optical head of an optical recording/reproducing apparatus according to a first embodiment of the present invention. In FIG. 1, 1 is a semiconductor laser, 2 is a collimating lens, 8 is an optical element for converting the cross-sectional shape of a light beam, 6 is a quarter wavelength plate, and 6 is an objective lens.

This optical element 10 has a step-like reflective surface formed on the end face as a reflective surface that divides an incident beam into two or more parts in the Y direction and reflects the light beam from the semiconductor laser 1 in a cross section in the Y direction. The length is made longer to reflect the light.

FIG. 2 shows the operation of changing the beam cross-sectional shape of the optical element 1o for changing the cross-sectional shape of the light beam.

As shown in Figure 2, the length of the cross-sectional shape of the incident light beam in the major axis direction (X direction) or minor axis direction (Y direction) is expanded by a conversion ratio of >7 = (a cos θ + b )/b. be able to.

As described above, according to this embodiment, a light beam emitted from a light source is incident from a fixed direction onto the optical element 10 in which reflective surfaces set at a predetermined angle are sequentially formed in a step-like manner. By reflecting the light beam, the conversion ratio between the long axis direction and the short axis direction of the cross-sectional shape of the light beam can be changed.

FIG. 3 shows an optical element 1o for converting the cross-sectional shape of a light beam according to a second embodiment of the present invention. This optical element 10 is constructed by stacking a large number of thin plates 11 whose end faces are at a predetermined angle, making the end faces step-like, and dividing and reflecting a beam incident on the end faces in the long direction of the cross-sectional shape of the reflected light beam. and the conversion ratio in the short axis direction can be freely set.

FIG. 4 shows an optical element 10 for converting the cross-sectional shape of a light beam according to a third embodiment of the present invention.

In this embodiment, thin plates 11 each having a reflective surface at a predetermined angle on the end face are connected by hinges 12 and stacked, and a mechanism 13 is configured to be able to slide on each other and freely change the overlapping position between the plates. By providing this, it is possible to freely set the conversion rate of the light beam shape.

Further, as shown in FIG. 6, thin grates 11 with end faces set at a predetermined angle are stacked, and rod-shaped levers 14, 15
By tilting both end faces of the stacked plates 110, the lengths of the major and minor axes of the light beam can be converted to a desired ratio.

FIG. 6 shows an optical element 10 for converting the cross-sectional shape of a light beam according to a fourth embodiment of the present invention. This optical element 10 is -
The cross-sectional shape of the light beam can be changed by forming V-shaped grooves 16 in parallel on one plate and setting the plate at an arbitrary angle to allow the light beam to enter the plate.

FIG. 7 shows a sixth embodiment of the present invention. This is because the light intensity distribution in the cross section of the incident beam can be freely changed in only one direction by changing the height and angle of the reflecting surfaces set at a predetermined angle or the distance between the reflecting surfaces. For example, as shown in FIG. 7, a light beam incident with a Gaussian distribution can be converted into a square wave and reflected.

This allows the beam to be moved in one direction, but with an apparent NA
After passing through the objective lens 6 shown in FIG. 1, the beam spot can be narrowed to a small size.

Effects of the Invention As described above, the present invention uses an optical element that converts the cross-sectional shape of a light beam in an optical head of an optical recording/reproducing device, thereby achieving a compact, lightweight, and thin device that is free from optical axis deviation due to wavelength fluctuations. It can be made into an optical head.

[Brief explanation of the drawing]

FIG. 1 is a side view of an optical head according to a first embodiment of the present invention, FIG. 2 is an enlarged side view thereof, and FIGS. 3 to 7 are optical heads according to second to sixth embodiments of the present invention. 8 is a perspective view of a conventional optical head, and FIG. 9 is a schematic diagram showing the beams before and after the objective lens.
...Collimating lens, 3...Beam shaping prism, 4...Mountain/polarizing beam splitter, 5...
... Quarter wavelength plate, 6 ... Objective lens,
8...Optical element. Name of agent: Patent attorney Toshio Nakao and 1 other person/-
11-hand laser beam diagram Figure 2 --- Collision, one train, 6 -- one objective lens... 10 -- "Optical element diagram, diagram, diagram, diagram, diagram, diagram.

Claims (5)

[Claims] (1) Comprising a light source that emits a light beam, and an optical element having a step-like reflective surface that has a predetermined inclination angle and that divides the incident beam into two or more parts in one direction of its cross section for reflection, The light beam from the light source is made incident on the optical element at a predetermined angle of incidence, and the ratio of the length of the major axis to the length of the minor axis of the cross-sectional shape of the incident beam and the output beam is converted. Features a light head. (2) A claim characterized in that the optical element has a laminated structure in which a large number of thin plates are stacked, and the end face of each plate is an end face with a constant inclination angle to form a step-like reflective surface. 1. The optical head described in 1. (3) The optical element has a laminated structure in which a large number of thin plates are stacked, each plate end face is an end face with a predetermined inclination angle to form a step-like reflective surface, and the plates are stacked so as to be able to slide on each other. 2. The optical head according to claim 1, further comprising a matching link structure. (4) The optical head according to claim 1, wherein the optical element has a plurality of V-shaped grooves formed on its surface to serve as a reflective surface. (5) The optical element is designed to convert the light intensity distribution in the cross section of the reflected light beam into a desired light distribution by varying the inclination angle and height of each reflecting surface or the distance between adjacent reflecting surfaces. The optical head according to claim 1, characterized in that: