JP2857245B2 - Optical pickup device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device provided with a grating element.

2. Description of the Related Art An example of a conventional optical pickup device having a grating element will be described with reference to FIG. Light emitted from the laser light source 1 is reflected by the transmission grating 2, collimated by the collimator lens 3, condensed by the objective lens 4, and irradiated on the surface of an optical disk 5 as an optical information recording medium. The recording of information is performed. The reflected light from the optical disk 5 is incident on the transmission type grating 2 through the objective lens 4 and the collimator lens 3 in order, and thereby the two linearly polarized light (S (Polarized wave, P-polarized wave).

In this case, as shown in FIG. 6, the P-polarized wave transmitted through the transmission type grating 2 is reflected by the high reflection surface 6 as the first reflection member disposed on the back surface side, and again,
The light passes through the transmission grating 2 and travels toward the laser light source 1. On the other hand, the S-polarized wave diffracted by the transmission grating 2 is reflected by the high reflection surface 6 provided on the back side thereof, diffracted by the transmission grating 2 again, and heads toward the laser light source 1.

Then, as shown in FIGS. 7 (a) and 7 (b), of the P-polarized light and the S-polarized light emitted from the transmission grating 2, the P-polarized light is detected by the two-divided light receiving element 7a, and the push-pull method is performed. The tracking servo can be performed by detecting the track error signal. Also, S
Focus servo can be performed by causing the four-divided light receiving element 7b to detect a polarized wave and detecting a focus error signal using an astigmatism method.

FIG. 8 (a) shows another signal detection method.
As shown in (b), four-divided light receiving element 8a, three-divided light receiving element
Using 8b, the P-polarized wave is detected by the four-divided light receiving element 8a,
By detecting the S-polarized wave by the three-divided light receiving element 8b,
The focus error signal and the track error signal can be detected by using the spot size method.

Problems to be Solved by the Invention In the case of the conventional apparatus as described above, the light emitted from the laser light source 1 is reflected on the surface of the transmission grating 2 and condensed on the surface of the optical disk 5. In this case, since the pitch of the transmission type grating 2 is set to an interval equal to or longer than the wavelength, even if the light reflected thereby is not a diffracted light, the disturbance of the wavefront can be considered to be considerable. When the light whose wavefront is disturbed is irradiated onto the surface of the optical disk 5 via the objective lens 4, it is impossible to perform recording in a minute area required for the optical disk 5. Therefore, even if the objective lens 4 having a high NA (numerical aperture) is used to eliminate such wavelength disturbance, the beam cannot be narrowed down to the diffraction limit.

Therefore, it is impossible to perform recording in a very small area required for the optical disc 5 due to such a situation, which has been a bottleneck for increasing the capacity.

Means for Solving the Problems In order to solve such a problem, according to the first aspect of the present invention, a transmission type grating is provided on an optical path while light emitted from a laser light source travels toward an optical information recording medium. In the optical pickup device in which the first reflection member is disposed at a certain angle with the transmission type grating, a second reflection member is provided on an optical path on the side opposite to the first reflection member sandwiching the transmission type grating. A reflection member was provided.

According to a second aspect of the present invention, in the first aspect of the present invention, the second reflection member is formed on one surface of the prism, and a transmission grating is integrally attached to the surface on which the second reflection member is formed. .

According to a third aspect of the present invention, in the first and second aspects of the present invention, the first reflecting member is formed on one surface of the prism.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the second reflecting member is formed on one surface of the prism, and the transmission type grating is disposed opposite to the surface on which the second reflecting member is formed. .

According to the first aspect of the present invention, the laser light emitted from the laser light source is reflected by the second reflecting member and irradiates the surface of the optical information recording medium, and the laser light is reflected by the grating surface as in the related art. However, since the light is reflected by the optical flat reflecting surface, light focused down to the diffraction limit can be made incident on the optical information recording medium, thereby realizing a large capacity optical disc.

According to the second aspect of the present invention, since the prism on which the second reflection member is formed is adhered integrally to the transmission grating, the size can be further reduced.

According to the third aspect of the present invention, the prism is also used on the first reflecting member side, so that two prisms having the same shape are used, so that it is easier to obtain, and at the same time, it is inexpensive and has a holding function. Simplification can be achieved.

According to the fourth aspect of the present invention, since the second reflecting member is formed on the surface of the prism which is easily available, it is possible to provide an inexpensive structure, and the second reflecting member and the transmission type grating are provided separately. Thereby, the degree of freedom of the design can be further expanded.

An embodiment of the present invention will be described with reference to FIG. The same parts as those in the prior art (see FIGS. 5 to 8) are denoted by the same reference numerals, and the description of the same parts will be omitted.

While the laser light emitted from the laser light source 1 travels toward the transmission grating 2, the second reflection is provided on the optical path opposite to the high reflection surface 6 as the first reflection member sandwiching the transmission grating 2. A reflection plate 9 as a member is provided. In this case, the surface of the reflection plate 9 is finished to an optical flat surface.

In such a configuration, the laser light emitted from the laser light source 1 is incident on the reflection plate 9 and is partially reflected thereby. The partially reflected light is condensed and radiated onto the surface of the optical disk 5 via the collimator lens 3 and the objective lens 4 in order, thereby recording information and the like. The reflected light from the optical disk 5 passes through the objective lens 4 and the collimating lens 3 in that order, partially passes through the reflecting plate 9 and enters the transmission type grating 2, where it is polarized and separated. Get the waves.

Then, in the same manner as in the prior art, the P-polarized wave is transmitted through the transmission type grating 2, reflected by the high reflection surface 6, again transmitted through the transmission type grating 2, and detected by the two-divided light receiving element 7a. A track error signal can be obtained. The S-polarized wave is diffracted by the transmission grating 2, reflected by the high reflection surface 6, is diffracted again by the transmission grating 2, and is divided into four light receiving elements.
7b, a focus error signal can be obtained.

As described above, the laser light emitted from the laser light source 1 is reflected by the reflection plate 9 and irradiates the surface of the optical disk 5, and the laser light is reflected by the grating surface of the transmission grating 2 as in the related art. Absent. Therefore, since the light is reflected by the optical flat reflecting surface, light focused down to the diffraction limit can be made incident on the optical disk 5, whereby the capacity of the optical disk 5 can be increased.

The reflection efficiency can be further increased by forming the non-reflection coating on the back surface of the reflection plate 9 and the back surface of the transmission grating 2.

Next, an embodiment of the present invention will be described with reference to FIG. Here, the reflection surface as the second reflection member
10 is formed on one surface of a prism 11, and the transmission grating 2 is integrally attached to the surface on which the reflection surface 10 is formed. As the prism 11, an isosceles triangle having an angle of 45 ° with the base can be used. The reflecting surface 10 is finished to an optical flat surface.

With such a configuration, since the transmission grating 2 is integrated with the surface of the prism 11 on which the reflection surface 10 is formed, it is possible to further reduce the size.

Next, an embodiment of the invention described in claim 3 will be described with reference to FIG.
Description will be made based on (b). Here, the high reflection surface 6 as the first reflection plate is formed on one surface of the prism 12.

In FIG. 3A, an isosceles triangular prism 12 having an angle of 45 ° with the same base as the shape of the prism 11 described above is used, and in FIG. This shows an example in which a triangular prism 13 is used.

By forming the high-reflection surface 6 on one surface of the prisms 12 and 13 as described above, two prisms 11 and 12 are used, so that the acquisition is further facilitated, and the holding function is reduced with a cheap configuration. Can be simplified.

Next, an embodiment of the invention described in claim 4 will be described with reference to FIG.
Description will be made based on (b). Here, a reflection surface 10 as a second reflection member is formed on one surface of the prism 11, and the transmission type grating 2 is opposed to the one surface on which the reflection surface 10 is formed.

That is, as shown in FIG. 4 (a), the reflection surface 10 of the prism 11 and the back surface of the transmission type grating 2 disposed opposite to each other are integrated with a spacer 14 interposed therebetween. As shown in (b), the reflection surface 10 of the prism 11 and the grating surface of the transmission type grating 2 disposed opposite to each other are integrated with a spacer 14 interposed therebetween.

As described above, since the reflection surface 10 is formed on one surface of the prism 11 which is easily available, the configuration can be made inexpensive, and by providing the reflection surface 10 and the transmission type grating 2 at a distance from each other. The degree of freedom of the design can be further expanded.

According to the first aspect of the present invention, a transmission grating is provided on an optical path while light emitted from a laser light source travels toward an optical information recording medium, and the first reflection member forms an angle with the transmission grating. In the optical pickup device provided with the second reflection member, the second reflection member is disposed on the optical path on the side opposite to the first reflection member sandwiching the transmission type grating. Since the laser light is reflected by the second reflecting member and irradiates the surface of the optical information recording medium and the laser light is not reflected by the grating surface but by the optical flat reflecting surface as in the related art, the optical information recording is performed. Light that is narrowed down to the diffraction limit can be made incident on the medium, thereby making it possible to increase the capacity of the optical disk.

According to a second aspect of the present invention, in the first aspect of the present invention, the second reflecting member is formed on one surface of the prism, and a transmission grating is integrally attached to the surface on which the second reflecting member is formed. Therefore, the size can be further reduced.

According to a third aspect of the present invention, in the first and second aspects of the present invention, since the first reflecting member is formed on one surface of the prism, the prism is also used on the first reflecting member side. Since two prisms are used, acquisition becomes even easier, and furthermore, the holding function can be simplified at a low cost.

According to a fourth aspect of the present invention, in the first aspect of the invention, the second reflecting member is formed on one surface of the prism, and the transmission type grating is disposed opposite to the surface on which the second reflecting member is formed. Therefore, since the second reflecting member is formed on the surface of the prism that is easily available, the structure can be inexpensive. In addition, by providing the second reflecting member and the transmission type grating apart from each other, the design freedom can be improved. It is possible to expand the degree more.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the invention described in claim 1,
FIG. 2 is a block diagram showing one embodiment of the invention described in claim 2,
FIG. 3 is a block diagram showing one embodiment of the invention according to claim 3;
FIG. 4 is a block diagram showing an embodiment of the invention according to claim 4;
FIG. 5 is a configuration diagram showing a conventional example, FIG. 6 is an explanatory diagram showing a state of polarization separation of the transmission type grating, and FIGS. 7 and 8 are front views showing shapes of various light receiving elements. 1 ... laser light source, 2 ... transmission grating, 5 ...
... optical information recording medium, 6 ... first reflecting member, 10 ... second reflecting member, 11, 12, 13 ... prism

Claims (4)

(57) [Claims] 1. A light source comprising: a transmission grating provided on an optical path while light emitted from a laser light source travels toward an optical information recording medium; and a light having a first reflecting member disposed at an angle to the transmission grating. An optical pickup device comprising a pickup device, wherein a second reflection member is provided on an optical path opposite to the first reflection member with the transmission grating interposed therebetween. A second reflecting member formed on one surface of the prism;
2. The transmission grating according to claim 1, wherein said transmission grating is integrated with said second reflection member.
Optical pickup device as described 3. The optical pickup device according to claim 1, wherein the first reflecting member is formed on one surface of the prism. 4. A second reflecting member is formed on one surface of the prism,
2. The optical pickup device according to claim 1, wherein a transmission type grating is disposed opposite to the surface on which the second reflection member is formed.