JPH06324281A - Optical pickup device - Google Patents

Abstract

PURPOSE:To unnecessitate the mounting adjustment of an objective lens and to provide an optical pickup device having a means for compensating the aberration generated by the tilt of the objective lens by arranging a parallel plane plate for compensating coma aberration between a light source and a collimator lens and adjusting an angle between the perpendicular direction of the parallel plane plate and an optical axis. CONSTITUTION:A laser beam transmitted from a laser light source 1 passes through a parallel plane plate 5 arranged with an inclination complying with the tilt of an objective lens 3 and enters into a collimator lens 2. The collimator lens 2 changes the incident laser beam to a parallel light beam and introduces it to the objective lens 3.A light spot 9 in which coma aberration is compensated is formed on an information recording medium 4 by means of the objective lens 3. The adjustment of the tilt of the objective lens 3 at the time of assembling generated in the manufacturing process is unnecessary and this tilt is easily adjusted by adjusting the tilt of the parallel plane plate 5 for compensating the coma aberration even when the coma aberration generates.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device for optically recording and reproducing information on an information storage medium, and more specifically, it is generated by an adjustment of an optical system in the optical pickup device and an inclination of an optical axis. The present invention relates to correction of aberration.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional ideal optical system in which aberration is not generated in a spot. The emitted light from the laser light source 1 passes through the collimator lens 2 and then becomes parallel light, which is condensed on the information recording medium 4 by the objective lens 3. The reflected light from the information recording medium 4 is modulated by the presence or absence of pits recorded on the information recording medium 4, the direction of magnetization, etc., and converted into an electric signal by a photodetector (not shown). At this time,
The spot formed on the information recording medium 4 has a concentric ring shape with no bias in the periphery like 11 and the offset state of the detection signal is close to zero.

On the other hand, in an actual optical pickup device, the objective lens 3 is attached while being slightly tilted with respect to the optical axis at the time of manufacture, so that adjustment is performed when the optical system is assembled. FIG. 5 shows the state of the spot when the objective lens 3 is tilted with respect to the optical axis. In this state, coma is generated, the spot does not have a concentric ring shape like 12 and an offset occurs in the reflected light from the information recording medium 4.

In Japanese Patent Laid-Open No. 3-242837, the surface shape is -ρ, which is located between the collimating lens and the objective lens.
There is disclosed an aberration correction means using a plate-shaped optical component formed of a plastic plate having an unevenness proportional to ³ cos (3φ−α). Here, ρ is the distance from one point of the wavefront when the polar coordinate system with the center on the exit pupil plane as the origin is set, φ is the angle, and α is a constant determined by each optical pickup device.

[0005]

However, as can be seen from the above equation, since the equation includes a constant determined by each optical pickup device, the surface shape of the plate-like optical component is different for each optical pickup device. However, the creation itself may be easy, but there was a problem that it had to be created for each device.

The present invention has been made in order to solve the above-mentioned problems, and in an optical pickup device, a means for correcting the aberration caused by the inclination of the objective lens without requiring the adjustment of the assembling of the objective lens is required. It is an object of the present invention to provide an optical pickup device having a.

[0007]

In order to achieve the above-mentioned object, the present invention has a light source and a collimator lens for collimating the light emitted from the light source, and the collimated light is formed on an information recording medium by an objective lens. In an optical pickup device that records and reproduces information by forming a minute spot on a parallel plate for correcting coma aberration between the light source and the collimator lens, the vertical direction of the parallel plate and the optical axis And an angle adjusting means for adjusting the angle between and.

The angle adjusting means is composed of a biaxial adjusting mechanism.

Further, it has a light source and a collimator lens for collimating the light emitted from the light source into parallel light, and the parallel light is used to form a minute spot on the information recording medium to record and reproduce information. In the optical pickup device, a hologram element that corrects coma aberration is replaceably arranged between the light source and the collimator lens.

[0010]

The optical pickup device of the present invention constructed as described above does not require adjustment for the inclination of the objective lens at the time of assembling that occurs during the manufacturing process, and is for correcting coma aberration even when coma aberration occurs. It can be adjusted more easily by adjusting the inclination of the parallel plate.

Further, when a coma aberration is corrected by using a hologram element instead of the parallel plate, it is sufficient to select the hologram element according to the inclination of the objective lens, and it is not necessary to adjust the inclination of the hologram element. Therefore, the coma aberration can be easily corrected.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention, which is a part of an optical system of an optical pickup device for magneto-optical recording and reproduction.

Reference numeral 1 is a laser light source using a semiconductor laser, 2 is a collimating lens for collimating light from the laser light source, 3 is an objective lens for forming a minute spot on the information recording medium 4, and 5 is parallel. It is a flat plate. The parallel plate 5 used here is made of a material having a good light transmittance of about 2 mm in thickness.

Next, the operation will be described. Laser light source 1
The laser light emitted from the laser beam passes through the parallel plate 5 arranged at an inclination according to the inclination of the objective lens 3 and enters the collimator lens 2. The collimator lens 2 converts the incident laser light into parallel light and guides it to the objective lens 3. Then, a spot in which coma aberration is corrected is formed on the information recording medium 4 by the objective lens.

FIG. 2 shows a construction in which the biaxial adjustment mechanism 6 adjusts the angle for correcting the aberration of the parallel plate 5.

FIG. 3 is a view showing another embodiment, in which 7 is a hologram element and 8 is a holder for fixing the hologram element. A holder 8 is arranged between the laser light source 1 and the collimator lens 2 so that the hologram element 7 can be fixed substantially perpendicular to the optical axis, and the coma aberration due to the inclination of the objective lens 3 is corrected, and the coma aberration is formed on the information recording medium 4. To form an ideal corrected spot.

The hologram element 7 is used by replacing it according to the inclination of the objective lens 3. However, it is not necessary to arrange the hologram element 7 so as to be inclined like the parallel plate 5, and since the thickness is thin, a comparison is made with the parallel plate 5. , The optical system can be made compact.

[0018]

As described above, the optical pickup device according to the present invention can omit the adjustment of the inclination of the optical axis of the objective lens by adjusting the assembling of the objective lens, and is caused by the omission of the adjustment. Coma aberration can be easily corrected.

Further, when the coma aberration is corrected by using the hologram element, it is not necessary to incline the element itself, so that the adjustment becomes remarkably easy.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an optical pickup device showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an optical pickup device showing another embodiment of the present invention.

FIG. 3 is an explanatory diagram of an optical pickup device showing another embodiment of the present invention.

FIG. 4 is a configuration diagram showing a conventional ideal optical pickup device.

FIG. 5 is a diagram for explaining coma aberration in a conventional optical pickup device.

[Explanation of symbols]

 1 Laser Light Source 2 Collimating Lens 3 Objective Lens 4 Information Recording Medium 5 Parallel Plate 6 2-Axis Adjustment Mechanism 7 Hologram Element 8 Holder 9, 10, 11, 12 Spot State

Claims (3)

[Claims] 1. A light source and a collimator lens for collimating the light emitted from the light source into parallel light, and the parallel light is used to form a minute spot on an information recording medium to record and reproduce information. In the optical pickup device, a parallel plate for correcting coma aberration is arranged between the light source and the collimator lens, and angle adjusting means for adjusting the angle between the vertical direction of the parallel plate and the optical axis is provided. Optical pickup device. 2. The optical pickup device according to claim 1, wherein the angle adjusting means is a biaxial adjusting mechanism. 3. A light source and a collimator lens for collimating the light emitted from the light source into parallel light, and recording and reproducing information by forming a minute spot on the information recording medium by the parallel light with an objective lens. In the optical pickup device, a hologram element that corrects coma aberration is displaceably arranged between the light source and the collimator lens.