KR100423853B1 - Optical Disc Player - Google Patents

Abstract

Disclosed is an optical disc reproducing apparatus. The apparatus comprises an optical system for guiding a laser beam onto a signal recording surface of a mounted optical disk and for guiding a reflective laser beam onto a light detector. In the present invention, the effective numerical aperture of the objective lens is adjusted according to the distance between the substrate surface of the mounted optical disk and the signal recording surface, and a laser spot having a diameter suitable for the recording density of the mounted optical disk is focused on the signal recording surface. . Therefore, preferably, data recorded on a plurality of optical discs of different types (different thicknesses or different recording densities) can be read.

Description

Optical disc playback device

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates generally to optical disc reading devices, and more particularly to an optical disc reading system or an optical disc reproducing apparatus capable of reading information from an optical disc with a thick substrate and an optical disc with a thin substrate. Optical disks with thick boards represent, for example, optical disks of approximately 1.2 mm thick, and optical disks with thin boards represent optical disks of approximately 0.6 mm thick. In this specification, the thickness of a substrate is defined as the distance from the substrate surface to the information-bearing surface. Thus, an approximately 1.2 mm thick optical disk, consisting of two optical disks each approximately 0.6 mm thick attached back to each other, is also referred to herein as an optical disk approximately 0.6 mm thick.

As a readable optical disc for recording multimedia data, a CD-ROM or the like has been put into practical use. A CD-ROM is a medium having a diameter of 12 cm, a thickness of 1.2 mm, a track pitch of 1.6 μm and a recording capacity of 540 Mbytes on one side. Digital video discs (DVDs) capable of recording video data using compression techniques such as MPEG type compression techniques are under development. When attempting to record MPEG-2 standard video data at a data rate of 4 Mbps on an existing CD-ROM, approximately 20 minutes of video data can be recorded. This means that existing CD-ROMs do not have enough capacity to record about 120 minutes of video.

To solve this problem, a technique for increasing the recording density of an optical disc by several times the recording density of an existing optical disc is under development. In this specification, a recording density equal to the recording density of the CD-ROM is referred to as "standard density".

For example, a super density (SD) of 12 cm diameter that can record approximately 5 Gbytes of data on one side and is identical to the diameter of a CD-ROM has been proposed. SD has a track pitch of approximately 0.73 μm and a shortest pit length of 0.4 μm and uses an efficient modulation mode. The thickness of the SD is 0.6 mm. When these two SDs are attached back to each other, the combined SD can record as much as 10 Gbytes of data equal to 240 minutes in the image data.

A High Density Multimedia Compact Disc (HDMCD) with a diameter of 12 Cm, capable of recording approximately 3.7 Gbytes of data on one side and the diameter of a CD-ROM, was devised. The HDMCD has a track pitch of approximately 0.84 μm and a shortest pit length of 0.45 μm.

The thickness of the HDMCD is 0.6 mm.

As a related art related to the present invention, there is a technique disclosed in Japanese Unexamined Patent Publication No. 7-5727l.

Japanese Unexamined Patent Publication No. 6-2l5406 discloses an optical pickup capable of focusing each beam spot on each information-bearing surface of two different types of optical disks having different substrate thicknesses.

Japanese Unexamined Patent Publication No. 5-303766 discloses an aspheric optical element that is not refracted by a collimated light beam according to the thickness of the mounted optical disk, or retracts according to the thickness of the mounted optical disk, thereby causing the difference in the substrate length without changing the focal length. An optical pickup for correcting a coma is disclosed. In this configuration, it is possible to focus each beam spot on each information-bearing surface of each optical disk having a different board thickness.

Japanese Unexamined Patent Publication No. 6-259804 has a laser diode for reproducing a standard density CD with a thick board and a laser diode for recording and reproducing a high density optical disk with a thin board, and a laser diode selected according to the optical disk. Disclosed is a device capable of focusing a laser beam output from a conventionally held information-bearing surface via an optical system.

In order to read information from the high density optical disk, the spot diameter of the laser beam focused on the information-bearing surface should be reduced to approximately 0.9 μm. In order to reduce the spot diameter to such a size, the wavelength of the laser beam must be shortened or the numerical aperture NA of the objective lens must be increased. However, if the numerical aperture NA of the objective lens is increased, the coma is increased in proportion to the third square of the numerical aperture NA of the objective lens. For this reason, if the laser beam reaching the board surface of the optical disk is deflected with respect to the perpendicular of the board surface, the coma is increased and the reproduced signal is reduced. Deflection of the optical disk, which prevents the laser beam from reaching vertically on the board surface, is caused by distortion of the optical disk or the like. On the other hand, since the coma is also proportional to the thickness of the optical disk board, it is possible to control the coma due to the deflection of the optical disk by reducing the thickness of the optical disk board. Based on this principle, a method of reducing the thickness of the optical disk board to reduce the spot diameter of the laser beam to approximately 0.9 μm by increasing the numerical aperture NA of the objective lens while controlling coma due to deflection of the optical disk board. This was tested.

The objective lens of the optical pickup is designed in consideration of the thickness of the optical disk and the wavelength of the laser beam. Therefore, when the substrate thickness of the optical disk on which information is recorded or the information is read differs from the substrate thickness assumed in the objective lens design process, waveform aberration occurs. As a result, the laser beam is not focused on the information-bearing surface of the optical disk, and thus information recording to or reproducing from the optical disk is impossible. For example, if an optical pickup equipped with an objective lens designed for an optical disc with a board thickness of 0.6 mm is used, the optical beam with a substrate thickness of 1.2 mm cannot focus the laser beam on the information-retaining surface. It is not possible to record information on an optical disk having a thickness of 1.2 mm or to read information recorded on an optical disk having a thickness of 1.2 mm. This means that for two different types of optical discs with different substrate thicknesses, an optical pickup equipped with two objective lenses suitable for each different type of optical disc must be prepared.

1.2 mm thick standard density discs (CD, CD-ROM), 1.2 mm thick high density discs (HDMCD), and 0.6 mm thick high density discs (SD) are expected to continue to exist in the future.

It is an object of the present invention to provide an apparatus capable of recording data on an optical disk having two or more different thicknesses, and to provide an apparatus capable of reading data from an optical disk having two or more different thicknesses.

The optical reproducing apparatus of the present invention irradiates a laser light to a signal recording surface of a plurality of types of optical disks having different distances from the substrate surface to the signal recording surface through an objective lens, and detects the laser light reflected from the signal recording surface. An optical reproducing apparatus for guiding a signal to reproduce a signal, the optical reproducing apparatus comprising: a first semiconductor laser emitting a first laser light having a first wavelength and a second laser light emitting a second laser light having a second wavelength different from the first wavelength; A second semiconductor laser and light shielding means for shielding the outer circumferential portion of the second laser light emitted from the second semiconductor laser without shielding the first laser light emitted from the first semiconductor laser according to the distance; The light shielding means shields the outer peripheral portion of the laser light according to the polarization planes of the first and second laser lights.

The apparatus may further include laser light switching means for driving the first semiconductor laser when the optical disk having the short distance is set, and for driving the second semiconductor laser when the optical disk having the standard distance is set. .

An optical disk reading apparatus for irradiating a laser beam onto a signal recording surface of an optical disk through an objective lens and guiding a laser beam reflected from the signal recording surface onto an optical detector, wherein the optical disk reading device outputs a signal from a laser source. The object of the present invention is achieved by constructing such an optical disc reading device, including means for adjusting the optical numerical aperture of the objective lens by adjusting the optical system for guiding the laser beam to the objective lens according to the thickness of the optical disc.

In this configuration, when the effective numerical aperture of the objective lens is adjusted in accordance with the thickness of the substrate of the mounted optical disk, a laser spot having a diameter suitable for the recording density of the mounted optical disk is focused on the signal recording surface of the mounted optical disk. .

For example, the above adjustment is performed by inserting a stopping down means in the optical path between the laser source and the objective lens.

For example, two different types of laser sources that are polarized in a direction perpendicular to each other switch in operation from one laser source to another, stopping down the diameter of the optical path for one polarization and stopping down for another polarization. The above adjustment is carried out by constructing an optical disk reading device in which polarization selecting means is not made. In such a configuration, switching from one laser source to another in accordance with a determination of whether an optical disk of standard thickness or a thinner thickness optical disk is mounted. Standard thicknesses are, for example, thicknesses in the range 1.15 mm to 1.25 mm, and thin thicknesses are, for example, thicknesses in the range 0.55 mm to 0.65 mm.

For example, the above adjustment is performed by selectively reading the reflection beam of one polarization beam whose beam diameter is stopped down or the reflection beam of the other polarization beam which is transmitted without the beam diameter being stopped down. This is for example the first light detector for detecting the reflected beam of one polarization beam whose beam diameter has been stopped down and the second light for detecting the reflected beam of the other polarizing beam which is transmitted without the beam diameter being stopped down. It can be particularly configured by providing a detector and sending the detection signal of the predetermined photo detector to the read signal processing section.

The object of the present invention is also achieved, for example, by adjusting the degree of the high frequency component of the read signal or by adjusting the gain-up degree of the read signal in accordance with the thickness of the mounted optical disk.

Also, for example, using an objective lens whose inner peripheral portion is designed to have a longer focal length than the outer circumferential portion, the objective of the objective lens can be focused so that the laser spot can be focused on the signal recording surface of each type of optical disk having a different thickness. By adjusting the numerical aperture, the object of the present invention is achieved. For example, when a standard thickness optical disk is mounted, the laser beam passed through the inner circumferential portion of the objective lens is focused on the signal recording surface, and when a thin thickness optical disk is mounted, the optical disk is mounted through the circumferential portion of the objective lens. The passed laser beam is focused on the signal recording surface. In the latter case, when the inner circumferential portion of the objective lens is blocked, the laser spot is stopped down due to the optical super-resolution phenomenon.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

(1) First embodiment:

1 shows a first embodiment according to the present invention. In this figure, the semiconductor laser 11 and the semiconductor laser 12 output the laser beam in a polarization direction perpendicular to each other.

The straight line represents the laser beam from the semiconductor laser 11 and the dotted line represents the laser beam from the semiconductor laser 12. The semiconductor laser 11 is mounted for an optical disk 51 having a thickness of 0.6 mm and is designed to output a laser beam having a wavelength of 635 ± 15 nm (or 650 ± 15 nm). Here, ± 15 nm is an error. The semiconductor laser 12 is mounted for an optical disk 52 with a thickness of 1.2 mm and is designed to output a laser beam with a wavelength of 635 ± 15 nm (or 650 ± 15 nm). The 0.6 mm thick optical disk 51 is a high density SD, and the 1.2 mm thick optical disk 52 is a high density HDMCD or a standard density CD. The numerical aperture of the objective lens 24 is designed to be 0.6 with respect to the optical disk 51 having a thickness of 0.6 mm.

When the 0.6 mm thick optical disk 51 is mounted, the semiconductor laser 11 is turned on and the semiconductor laser 12 is turned off. A laser beam having a wavelength of 635 nm (P polarized beam) output from the semiconductor laser 11 is transmitted through the polarizing beam splitter 21 and refracted by the collimator lens 22 to be a collimated beam, thereby providing a half mirror ( transmitted through the half mirror 23 and not stopped down, but through the polarization filter 31 and collected by the objective lens 24 on the signal recording surface 5la of the optical disk 51 having a thickness of 0.6 mm. Focused At this time, the diameter of the laser spot is 0.9 mu m.

The laser light reflected by the signal recording surface 5la is refracted by the objective lens 24 to be a collimated beam, which is transmitted through the polarization filter 31 without being stopped down and reflected by the half mirror 23 and is 90 °. The light is refracted by the light condenser and focused by the condenser lens 25 and focused on the photodetector 40, and then detected as a signal corresponding to the recording data.

When the optical disk 52 having a thickness of 1.2 mm is mounted, the semiconductor laser 12 is turned on and the semiconductor laser 11 is turned off. A laser beam having a wavelength of 635 nm (S polarized beam) output from the semiconductor laser 12 is transmitted by the polarizing beam splitter 21 and collimated by the collimator lens 22, through the half mirror 23. And the peripheral portion is blocked by the polarization filter 31 and transmitted through the center portion (stopped down by the polarization filter 31), and then collected by the objective lens 24 to be used as an optical disk having a thickness of 1.2 mm ( Is focused on the signal recording surface 52a. At this time, the diameter of the laser spot is 1.3 mu m. That is, by stopping down by the polarization filter 31, the effective numerical aperture of the objective lens 24 is approximately 0.4.

The polarization filter 31 allows the P polarization beam to pass through without stopping (two-way arrow in FIG. 1 (b)), and the S polarization beam stops down to a smaller diameter [black dots in FIG. 1 (b)]. Polarization selective filter. When the numerical aperture of the objective lens 24 is 0.6, if the focal length of the objective lens is 3.3 mm and the effective diameter of the laser beam (diameter of the outer circle in Fig. 1 (b)) is 3.96 mm, the polarization filter 31 The diameter (diameter of the inner circle in Fig. 1 (b)) with a numerical aperture after stopping down by is 2.64 mm.

The laser beam reflected by the signal recording surface 52a is collimated by the objective lens 24 and transmitted through the polarization filter 31 without being stopped down (since the laser beam has already been stopped down), and then the half mirror 23 Is refracted by 90 [deg.]), Collected by the condenser lens 25, focused on the photodetector 40, and then detected as a signal corresponding to the recording data.

In the above-described configuration, the polarization filter 31 is used. However, instead of the polarization filter 31, a polarization selection hologram may be used. It is an optical element that scatters peripheral portions so that only the central portion of one polarizing beam is passed through.

Further, in the above-described configuration, good condensing characteristics can be obtained by placing the polarizing filter 31 immediately before the objective lens 24 so that the objective lens 24 and the polarizing filter 31 can be integrally shifted even during tracking servo control. Read characteristics can be achieved. However, if such a drop in readability is acceptable, the polarization filter 31 may be provided as a fixed aperture. In this case, the polarization filter 31 may be disposed at a predetermined position between the semiconductor laser 12 and the objective lens 24. Furthermore, if a polarization filter 31 is provided at a portion away from the optical path of the semiconductor laser 11 (ie, between the laser diode 12 and the polarization beam splitter 21), a normal stop may be used instead of the polarization filter. have.

(2) Spot diameter for effective NA:

Hereinafter, with reference to FIG. 2, the relationship between the effective numerical aperture NA and the laser spot diameter will be described. 2 is designed for a 0.6 mm thick disk and by using an objective lens with a NA of 0.6, the laser beam is focused on the signal recording surface of an optical disk of 1.2 mm thickness, and the aperture is set in the optical path to adjust this aperture. This shows the relationship between the effective NA and the laser spot in the actual case where the effective NA is changed. Here, a black dot represents the case where the laser beam with a wavelength of 635 nm is used, and a white point shows the case where the laser beam with a wavelength of 780 nm is used.

In the region where the effective NA is 0.4 or less, the laser spot diameter is approximately proportional to λ / NA. It is effective in the area where NA is 0.4 or more because of the phenomenon that when an optical disk having a thickness different from the normal thickness is read, the spherical aberration increases in proportion to the square of the numerical aperture. The stop down of the spot diameter becomes more difficult. Here, the typical thickness is the thickness designed to match the mounted objective lens.

For this reason, as shown in FIG. 2, when the effective numerical aperture is about 0.4 (0.35-0.4), the laser spot diameter is the smallest (1.3 μm for the 635 nm laser beam and 1.65 for the 780 nm laser beam). Μm). According to the present invention, an optical disk of 1.2 mm thickness can be read by using an objective lens designed for 0.6 mm thickness. That is, a standard density CD 1.2 mm thick and a high density SD 0.6 mm thick can be exchanged.

Wavelengths of 635 ± 5 nm, 650 ± 15 nm, 680 ± 15 nm or 780 ± 15 nm may be used.

In addition, the wavelength of the semiconductor laser 11 and the semiconductor laser 12 may differ.

(3) Exchange of HDMCD and SD:

As described above, when a laser beam with a wavelength of 635 nm is used, a laser spot having a diameter of 1.3 μm is formed on a signal recording surface of an 1.2 mm thick optical disk using an objective lens designed for a 0.6 mm thick optical disk. You can focus. On the other hand, when a laser beam with a wavelength of 780 nm is used, an objective lens designed for a 0.6 mm thick optical disk can be used to focus a laser spot having a diameter of 1.65 μm on the signal recording surface of the 1.2 mm thick optical disk. Can be.

In the 1.2 mm thick standard density CD currently used, since a laser spot having a diameter of 1.6 μm can be read out, a laser beam having a wavelength in the range of 620 nm to 800 nm is obtained as described above, from 1.3 μm to 1.65 μm. It can be read by stopping down to the range. However, when reading a high density HDMCD having a thickness of 1.2 mm, a laser spot diameter of about 1.1 mu m is required, so that the above configuration cannot achieve good read characteristics.

Therefore, to exchange 1.2 mm thick high density HDMCD and 0.6 mm thick SD, a circuit as shown in FIG. 5 is used. In particular, when reading the HDMCD, the amplifier 60a is selected, and the gain-up degree of the read signal and the amplification degree of the high frequency component are increased than in the case of SD, and this data is transmitted to the read signal processor 70. In addition, the amplifier 61a is selected, and the gain-up degree of the tracking error signal is increased than in the case of SD, and this data is transmitted to the tracking servo controller 71. On the contrary, when reading SD, the amplifier 60b is selected, and the gain-up degree of the read signal and the amplification degree of the high frequency component are reduced than in the case of HDMCD, and this data is transmitted to the read signal processor 70. In addition, the amplifier 61b is selected, and the gain-up degree of the tracking error signal is reduced than in the case of the HDMCD, and this data is transmitted to the tracking servo controller 71. By configuring the circuit as described above, the read signal with frequent jitter and loud noise can be compensated.

This configuration also requires a wavelength in the range of 620 nm to 665 nm.

(4) Second Embodiment

3 shows a second embodiment. According to the second embodiment, as a light detector, a light detector 41 which detects the reflection beam of the laser beam output from the semiconductor laser 11 and the light which detects the reflection beam of the laser beam output from the semiconductor laser 12 Detector 42 is used. In this configuration, the polarizing beam splitter 26 is disposed in front of the photo detectors 41 and 42 so that the reflected beam of the laser beam output from the semiconductor laser 11 is focused on the photo detector 41, and the semiconductor laser The laser beam output from 12 is condensed on the light light emitter 42. As two photodetectors are used in this manner, a photodetector is arranged for the first semiconductor laser (semiconductor laser 11 or semiconductor laser 12), and a second semiconductor laser (semiconductor laser 12) for the photodetector. Or semiconductor laser 11] is no longer necessary.

Since the other parts of the configuration of the second embodiment are the same as the configuration of the first embodiment, the same parts are denoted by the same reference numerals, and their description will be omitted.

(5) Third embodiment:

4 shows a third embodiment. According to the third embodiment, as the semiconductor laser, the one-chip semiconductor laser 10 is used. The semiconductor laser 10 is composed of two semiconductor lasers mounted on one chip, capable of outputting laser beams of each of the TE mode and the TM mode having polarization directions perpendicular to each other. The laser wavelength is 635 nm. Since the one-chip semiconductor laser having the TE mode and the TM mode is used and the laser beam of the TE mode or the TM mode is selected depending on whether an optical disk of 0.6 nm thickness or an optical disk of 1.2 mm thickness is mounted, The polarization beam splitter 21 shown in FIGS. 1 and 3 is no longer needed.

Since other parts of the configuration of the third embodiment are the same as those of the first and second embodiments, the same parts are denoted by the same reference numerals, and their description will be omitted.

(6) Fourth Example:

6 shows a fourth embodiment. According to the fourth embodiment, the objective lens 24 and the polarization filter 31 of the first to third embodiments are replaced by the objective lens 240 and the polarization filter 310, respectively. Since other parts of the configuration of the fourth embodiment are the same as those of the first and third embodiments, description of the entire optical system will be omitted, and the objective lens 240 and the polarization filter 310 will be described.

The objective lens 240 is designed by changing the focal length between the inner circumference portion and the outer circumference portion. In particular, the objective lens 240 is designed to have a different curvature between the inner circumference portion and the outer circumference portion as shown in FIG. 6 (a) to pass through the inner circumference portion of the objective lens 240. The laser beam is focused on the signal recording surface 52a of the 1.2 mm thick optical disk and the laser beam passing through the outer circumferential portion of the objective lens 240 is focused on the signal recording surface 5la of the optical disk 0.6 mm thick. .

The polarization filter 310 blocks only the outer circumferential portion of the S polarization beam in the same manner as the polarization filter 31 described above. That is, the polarization filter 310 causes the outer circumference portion and the inner circumference portion of the P polarization beam to be transmitted as indicated by the two-way arrow straight line and the two-way arrow dotted line, and only the inner circumference portion of the S polarization beam is the sixth (c). Allow for transmission as indicated by black dots in the figure.

When reading a 1.2 mm thick HDMCD, the S-polarized beam indicated by the black dots is output from the laser source, the outer circumferential portion of the S-polarized beam is blocked by the polarization filter 310, and the inner circumferential portion of the S-polarized beam is polarized. Passed through the filter. As indicated by the one-dot chain line in FIG. 6 (a), by the inner circumferential portion of the objective lens 240, the S-polarized beam is focused on the signal recording surface 52a of the HDMCD 1.2 mm thick, and then Data is read from HDMCD.

Upon reading an SD of 0.6 mm thickness, the P-polarized beam is output from the laser source as indicated by the double arrow straight line and the double dotted line straight line in FIG. 6 (c). The P-polarized beam is not blocked by the polarization filter 310, and the outer and inner circumferential portions of the P-polarized beam are collected by the objective lens 240. Of all the laser beam portions, the laser beam portion transmitted through the outer circumferential portion of the objective lens 240 is focused on the signal recording surface 51a of the SD of 0.6 mm thickness as indicated by the straight line in FIG. 6 (a). After that, the data is read from the SD. Here, the laser beam portion passing through the outer circumferential portion of the objective lens 240 is not stopped down on the signal recording surface 51a, and the adverse effect of the inner circumferential portion is ignored.

Unlike the polarization filter 31 already described above, the polarization filter 310 may be replaced by a filter capable of blocking the outer circumference of the S polarization beam and blocking the inner circumference of the P polarization beam. That is, a filter capable of transmitting only the outer circumferential portion of the P polarization beam as indicated by the double-headed arrow straight line in FIG. 6 (c) and the inner circumferential portion of the S polarized beam as indicated by the black dot in FIG. It may be used in such a configuration.

In such a configuration, when reading an SD of 0.6 mm thickness, the inner circumferential portion is blocked by the polarization filter 310 and the outer circumferential portion passes through the polarization filter 310, and the signal recording surface 51a is provided by the objective lens 240. Optical super resolution is generated in the P-polarized beam focused on the beam.

Therefore, there is an effect that the diameter of the laser spot focused on the signal recording surface 51a can be stopped down.

(7) Other Examples

In each of the above-described embodiments, the effect of the present invention is achieved by transmitting one polarization beam and stopping the other flat beam through a polarization selective optical element to reduce the effective numerical aperture. However, the effect of the present invention may also be achieved by delivering a laser beam of a predetermined wavelength and reducing the effective numerical aperture by stopping down the laser beam of another wavelength through the wavelength selective optical element.

In the laser beam having a wavelength of 430 nm or the laser beam having a wavelength of 532 nm, the former is a blue laser, the latter is a green laser and is not referred to in each of the above-described embodiments. However, the present invention is also realized by using each of them.

FIG. 1 (a) is a block diagram showing the optical system of the first embodiment, and FIG. 1 (b) is a diagram showing the polarization selection filter used in the first embodiment.

2 shows the relationship between the spot diameter and the effective numerical aperture adjusted by inserting a diaphragm in the optical path when an objective lens with a numerical aperture adjusted to 0.6 with an SD of 0.6 mm thickness is used, the laser beam being 1.2 mm thick. A graph showing condensing on the signal recording surface of the disc.

3 is a block diagram showing the optical system of the second embodiment.

4 is a configuration diagram showing the optical system of the third embodiment.

5 is a block diagram showing a signal processor used when the HDMSC and the SD are compatible with each other.

6 shows main parts of a fourth embodiment;

Explanation of symbols for the main parts of the drawings

11, 12: semiconductor laser

21: beam splitter

22: collimator lens

23: half mirror

24: objective lens

25 condensing lens

31: polarization filter

51, 52: optical disc

5la, 52a: signal recording surface

Claims (2)

An optical type for reproducing a signal by irradiating laser light through an objective lens to a signal recording surface of a plurality of types of optical disks having different distances from a substrate surface to a signal recording surface, and guiding the laser light reflected from the signal recording surface to an optical detector. In the playback device, A first semiconductor laser for emitting a first laser light having a first wavelength; A second semiconductor laser for emitting a second laser light having a second wavelength different from the first wavelength; Light blocking means for shielding the outer circumferential portion of the second laser light emitted from the second semiconductor laser without shielding the first laser light emitted from the first semiconductor laser according to the distance. Including, And the light shielding means shields the outer circumference of the laser light according to the polarization planes of the first and second laser lights. The laser light switching means according to claim 1, wherein the first semiconductor laser is driven when the optical disk having a short distance is set, and the second semiconductor laser is driven when the optical disk having a standard distance is set. The optical disk reproducing apparatus further comprises.