JPH073461Y2 - Optical pickup device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to an optical pickup device used in a device for optically recording and reproducing information by irradiating an optical recording medium with a light spot.

<Prior Art> An optical pickup device of this type is generally one that records, reproduces, and erases information by one laser light source. In this method, when reproducing information, the signals recorded on the disc are sequentially read by one light spot, and when recording information, similarly, the information is sequentially written by one light spot. However, there is a drawback that the read / write speed, that is, the data transfer rate is slow.
Therefore, as shown in FIG. 2, a method has been used in which a plurality of pickup devices are used to record or reproduce information in parallel to increase a substantial data transfer rate.

In the figure, the laser light from the semiconductor laser light source 1a is collimated by the collimator lens 2a, and then is irradiated as a light spot 8a on the disc-shaped recording medium 10 by the objective lens 4a through the beam splitter 3a to form a disc-shaped light. The reflected light reflected by the recording medium 10 is collimated by the objective lens 4a, reflected at a right angle by the beam splitter 3a, incident on the prism 5, deflected according to the law of refraction, and received by the condenser lens 6. It is focused on the element 7a.

On the other hand, the laser light from the semiconductor laser light source 1b is collimated by the collimator lens 2b, and then the objective lens 4b passes through the beam splitter 3b and the disc-shaped recording medium 10 is emitted.
It is irradiated as a light spot 8b on the top, and a disk-shaped recording medium
The reflected light reflected by 10 is collimated by the objective lens 4b, reflected at a right angle by the beam splitter 3b, incident on the prism 5 through the beam splitter 3a, and deflected according to the law of refraction to be condensed. Light receiving element by lens 6
Focused on 7b.

Since the semiconductor laser light sources 1a and 1b have different emission wavelengths, and the deflection angles at the prism 5 are different due to this, the reflected light 12a, 12b from the spots 8a and 8b on the disk is changed.
b is focused on different light receiving elements 7a and 7b.

The light-receiving elements 7a and 7b can simultaneously reproduce the signals read by the spots 8a and 8b located at different positions on the disc, so that the data transfer rate is twice as high as that of the method of reading the signals by one laser light source. Is obtained.

<Problems to be Solved by the Invention> In the conventional device shown in FIG. 2, the light reflected from the disc and reflected at a right angle by the beam splitter passes through the surface 3a ₁ of the beam splitter 3a as shown in FIG. It is emitted vertically and is incident on the surface 5 ₁ of the prism 5 and the semiconductor laser light source 1
a, and the first refraction according to the wavelength 1b, the surface of the prism 5 5 ₂
Similarly, after the second refraction, the light reaches the condenser lens 6. When the difference between the emission directions of the light beams 12a and 12b of the respective wavelengths obtained by the above-mentioned two total refraction is Δθ and the focal length of the condenser lens 6 is f, the distance between the condensing positions of the light beams 12a and 12b. Since x is given by x = ftan Δθ, x increases as Δθ increases or f increases.

In order to reduce the size of the optical pickup, the focal length f of the condenser lens 6 should be as short as possible.
The distance between a and 7b is preferably large in order to detect the signals of the light rays 12a and 12b independently without interfering with each other. That is, in order to reduce the size of the pickup, it is necessary to reduce f while keeping x constant in the above equation, and thus the difference Δθ in deflection angle due to wavelength must be increased. However, in order to increase Δθ, there is no effective means other than using a plurality of prisms, which increases the number of parts and complicates the optical system and raises the cost. There was a problem that it would end up.

The present invention has been made in view of these problems, and has been made for the purpose of realizing miniaturization of an optical pickup without significantly increasing the cost.

<Means for Solving Problems> In order to achieve the above object, in the present invention, an information recording medium is irradiated with a plurality of light beams having different wavelengths through beam splitters, respectively. Each of the signal lights reflected from each beam splitter is reflected by the respective beam splitters so as to have the same optical path, and each signal light emitted from one beam splitter is incident on the deflection means, and each wavelength is converted by this deflection means. In the optical pickup device for deflecting the signal light of each wavelength to the light receiving element having the light receiving surface at or near the convergence point of the signal light of each wavelength, the final emission surface of the beam splitter for emitting the signal light to the deflection means. Is tilted with respect to a plane perpendicular to the signal light.

<Operation> Since the final exit surface of the beam splitter is tilted with respect to the plane perpendicular to the signal light, multiple signal lights with different wavelengths are emitted at the refraction angle according to each wavelength when exiting the beam splitter. However, as compared with the case where only the conventional prism is used, the refraction contributing to the separation of the signal light is increased once, and the angle difference after refraction of each signal light, that is, the above-mentioned Δθ is increased. Therefore, the optical pickup can be downsized with a small number of parts without complicating the optical system.

<Embodiment> Next, an embodiment of the present invention shown in FIG. 1 will be described.
The same parts as those in the conventional example shown in FIG. 2 are indicated by the same reference numerals, and only different parts will be described.

In the figure, 3a 'is a beam splitter for guiding the reflected light 12a of the laser light from the semiconductor laser light source 1a to a signal detection system including a prism 5, a condenser lens 6 and the like, and a reflected light 12b from the beam splitter 3b is also included. It is configured so that it overlaps with the reflected light 12a and passes through this beam splitter 3a 'in the same direction. 3a ₁ 'beam splitter 3a to a final exit surface with respect to the reflected light 12a, 12b' is emission surface of the reflected light 12a which passes through the beam splitter 3a ', 12b
Is inclined with respect to a plane perpendicular to the plane, and the inclination is such that refraction in the same direction as the refraction of the reflected light at the prism 5 can be obtained.

In the configuration as described above, reflected from the disk 10,
The reflected lights 12a and 12b reflected at right angles by the respective beam splitters 3a 'and 3b are the surface 3 of the beam splitter 3a'.
The light enters at a finite incident angle with respect to a ₁ ′, exits from the surface 3 a ₁ ′ at a refraction angle corresponding to each wavelength, and reaches the prism 5 with an angle difference. In the prism 5, similar to the conventional example, the reflected light 12a, 12 has different refraction angles for each wavelength by refraction twice
given to b, the angle difference Δθ between the two rays is further expanded. Then, the reflected lights 12a and 12b are condensed by the lens 6 at intervals x according to the above-mentioned formula, and are detected by the light receiving elements 7a and 7b.

That is, in this embodiment serves as the beam splitter 3a ₁ 'also has a function of the spectral prism, while the same parts as the conventional, it is possible to increase the difference in deflection angle between the different wavelength light. Therefore, the same light receiving element 7a, the light receiving element 7 from the beam splitter 3a ₁ 'with respect to the spacing x between 7b
The distance to a and 7b can be made smaller than before, and the optical pickup device can be downsized.

<Effect of the Invention> As is apparent from the above-described embodiments, the optical pickup device of the present invention is such that the final exit surface of the beam splitter is tilted with respect to the plane perpendicular to the signal light.

Therefore, the optical pickup device can be downsized by reducing the distance from the beam splitter to the light receiving element without increasing the number of parts and increasing the cost, and when the downsizing is not required, the prism It is also possible to use a beam splitter only to separate rays of different wavelengths without using an optical fiber.In this case, the cost is reduced by reducing the number of parts and the light quantity is increased due to the decrease in the number of optical components through which the rays pass It is possible to improve the / N ratio.

[Brief description of drawings]

FIG. 1 is a schematic side sectional view of an embodiment of the present invention, and FIGS. 2 and 3 are a schematic side sectional view of a conventional example and a schematic side sectional view of its main part, respectively. 1a, 1b …… Semiconductor laser light source, 3a, 3a ′, 3b …… Beam splitter, 3a ₁ ′ …… Exit surface, 5 …… Prism, 7a,
7b: light receiving element, 10: disc-shaped recording medium, 12a, 12b
……reflected light

Claims (1)

[Scope of utility model registration request] 1. An information recording medium is irradiated with a plurality of light beams having different wavelengths through beam splitters, and each signal light reflected from the information recording medium has the same optical path by each beam splitter. As described above, each signal light emitted from one beam splitter is incident on the deflecting means, and is deflected based on each wavelength by this deflecting means, and the signal light of each wavelength is converged at or near the convergence point. In an optical pickup device for guiding light-receiving surfaces to respective light-receiving elements, the final emission surface of a beam splitter for emitting signal light to the deflecting means is inclined with respect to a plane perpendicular to the signal light. Optical pickup device.