JP2600704B2 - Optical recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus using an optical tape, an optical disk, or the like as a recording medium, and more particularly, to a light beam for scanning a light beam using an acousto-optic deflecting element. The present invention relates to a recording / reproducing device.

[Summary of the Invention]

The present invention relates to an optical recording / reproducing apparatus using an optical tape, an optical disk, or the like as a recording medium, and guides a light beam to an acousto-optic deflecting element, and uses a zero-order light beam transmitted through the acousto-optic deflecting element, and the acousto-optic deflecting element. Deflection controlled 1
The next light beam is discriminated by the polarizing beam splitter,
By projecting the primary light beam onto the optical recording medium via the quarter-wave plate, it is possible to prevent the zero-order light beam which is not involved in recording / reproducing the information signal from reaching the optical recording medium. An optical recording / reproducing apparatus in which a light beam reflected by an optical recording medium is extracted by a polarizing beam splitter for discriminating between a zero-order light beam and a primary light beam so that an information signal can be easily reproduced. It is.

[Conventional technology]

Conventionally, using an optical tape or an optical card as a recording medium,
An optical recording / reproducing apparatus which records or reproduces a predetermined information signal by scanning a light beam on the recording medium via an acousto-optic deflecting element (AOD) is disclosed in, for example, Japanese Patent Application It has been proposed as described in Japanese Patent Application No. 61-261724.

Such an optical recording / reproducing apparatus is, as shown in FIG.
It has a laser light source 101 such as a laser diode. In the recording mode, the light beam emitted from the laser light source 101 is modulated in accordance with the information signal to be recorded to change its intensity, and in the reproduction mode, has a constant intensity lower than that in the recording mode. I have. This light beam is converted into a parallel light beam by predetermined optical components such as a collimating lens 102, and the acousto-optic deflecting element 103
It is led to. The light beam incident on the acousto-optic deflecting element 103 is subjected to deflection control by the acousto-optic deflecting element 103. The acousto-optic deflecting element 103 has a transducer 103a and an absorber 103b on both surfaces facing each other, receives a drive signal given from a deflection driver 103c to the transducer 103a, and sets the deflection angle of the light beam,
The angle is changed within a predetermined angle range in the direction indicated by the arrow α in FIG.

Then, the light beam reaches the objective lens 107 via the cylindrical lens 104 and the pair of relay lenses 105 and 106. The objective lens 107 transmits the light beam to the optical recording medium 1.
Light is condensed on the recording surface 109 of 08.

The deflection-controlled light beam is condensed on the recording surface 109 by the objective lens 107 by performing deflection control within a predetermined angle range in the direction indicated by the arrow α in FIG. The first position indicated by f ₀ in FIG.
Scanning from the focal position so that until the second focal position indicated by Figure 4 in f _1.

The optical recording medium 108 is moved in a direction perpendicular to the paper surface of FIG. 4, that is, in a direction perpendicular to the scanning direction of the light beam.

In the recording mode, the recording surface 109 undergoes a chemical or physical change due to the irradiation of the light beam, and an information signal is recorded.

In this recording / reproducing apparatus, in order to reproduce the information signal recorded on the optical recording medium, for example, as described in the specification of Japanese Patent Application No. 61-261724 filed earlier by the present applicant. In addition, a beam splitter 110 is provided between the collimating lens 102 and the acousto-optic deflecting element 103,
The beam splitter 110 may extract and detect the reflected light beam from the recording surface 109. That is, in the reproduction mode, the light beam is scanned as described above, is reflected on the recording surface 109, and is incident on the objective lens 107 again. The reflected light beam is transmitted to the beam splitter 1 through the pair of relay lenses 106 and 105, the cylindrical lens 104, and the acousto-optic deflecting element 103.
Guided to 10. The reflected light beam is reflected by the beam splitter 110 and guided to a light detecting unit 111 including a detection lens, a photodetector, and the like. This light detection means 111
The information signal is reproduced by detecting the reflected light beam.

[Problems to be solved by the invention]

By the way, in the acousto-optic deflecting element 103 used in the above-described optical recording / reproducing apparatus, the light beam incident on the acousto-optic deflecting element 103 is a zero-order light beam which is transmitted without diffracting the light beam. And a primary light beam that is diffracted and transmitted by the light beam. The zero-order light beam is a light beam that has the same traveling direction and polarization state as the light beam that is transmitted after passing through the acousto-optic deflecting element 103. The primary light beam is subjected to deflection control by the acousto-optic deflecting element 103 and its polarization state is changed, so that the primary light beam is in a linear polarization state in a direction orthogonal to the polarization direction of the incident light beam.

Then, the zero-order light beam reaches the recording surface 109 similarly to the first-order light beam. Since the zero-order light beam is not deflection-controlled by the acousto-optic deflecting element 103, the zero-order light beam is always f
Ranging from ₀ to f ₁ is focused at a position slightly deviated from the scanning range of the first-order optical beams.

At this time, the zero-order light beam condensed on the recording surface 109 writes an information signal on the recording surface 109 in the recording mode, similarly to the primary light beam. In the reproducing mode, the zero-order light beam is reflected by the recording surface 109 in the same manner as the primary light beam. Then, the recording surface 10 of the zero-order light beam
The light beam reflected by 9 reaches the light detecting means 111 similarly to the light beam reflected by the recording surface 109 of the primary light beam.

As described above, since the zero-order light beam is converged on the recording surface 109 and is reflected and reaches the light detecting means 111, accurate recording and reproduction are not guaranteed.

In order to prevent such an adverse effect that the zero-order light reaches the recording surface 109, as shown in FIG.
It is conceivable to provide a shielding plate 112 at a position where the zero-order light beam is condensed between the pair of relay lenses 105 and 106. In this way, the zero-order light beam is transmitted to the shielding plate 112.
Shielded by

However, when the primary light beam is close to the zero-order light beam, that is, when the angle at which the primary light beam is diffracted by the acousto-optic deflecting element 103 is small, the primary light beam is The plate 112 may be shielded together with the zero-order light beam. Therefore, the information signal can be recorded / reproduced by the primary light beam only because of the scanning angle of the primary light beam.
This is only when scanning within an angle range that is not shielded by the shielding plate 112.

The angle at which the primary light beam is deflection-controlled by the acousto-optic deflection element 103 is as small as about several degrees. Among the angles at which the primary light beam is deflection-controlled, the angle effective for recording / reproducing the information signal is further narrowed by the shielding plate 112 because the recording density of the information signal on the recording surface 109 is reduced. An obstacle to much more improvement. In addition, it is required to keep the arrangement position of the shielding plate 112 with high accuracy, making assembly and adjustment of the apparatus complicated and poor in practicality.

Further, utilizing the difference in the polarization state between the zero-order light beam and the first-order light beam, the zero-order light beam and the first-order light beam can be combined using an optical component such as a polarization filter whose transmittance has polarization dependence. Discrimination from the primary light beam can be considered. However, means for discriminating between the zero-order light beam and the primary light beam and means for extracting the reflected light beam from the recording surface 109 must be provided independently. This complicates the configuration of the device.

Therefore, the present invention has been proposed in view of the above-described circumstances, and ensures that a zero-order light beam that is not deflection-controlled by an acousto-optic deflecting element does not reach a recording medium, thereby ensuring accurate recording and reproduction. It is an object of the present invention to provide an optical recording / reproducing apparatus capable of achieving an improvement in recording density while improving the recording density with a simple apparatus configuration.

[Means for solving the problem]

In order to solve the above problems and achieve the above object, in an optical recording / reproducing apparatus according to the present invention, a linearly polarized light beam is supplied to an acousto-optic deflecting element, and the deflection direction of the acousto-optic deflecting element and the polarization direction Are incident so that they are parallel,
The polarization beam splitter discriminates between the zero-order light beam transmitted through the acousto-optic deflecting element and the primary light beam whose deflection is controlled by the acousto-optic deflecting element in accordance with a scanning signal. Scanning on an optical recording medium through a quarter-wave plate, the reflected light beam from this optical recording medium is guided to the polarizing beam splitter through the quarter-wave plate, and by the polarizing beam splitter, The reflected light beam is extracted to perform optical recording / reproduction.

[Action]

In the optical recording / reproducing apparatus according to the present invention, since the primary light beam whose deflection is controlled by the acousto-optic deflecting element and the zero-order light beam whose deflection is not controlled are discriminated by the polarization beam splitter, they are involved in recording / reproducing information signals. Not above 0
The secondary light beam is prevented from reaching the optical recording medium, and the reflected light beam of the primary light beam is extracted by the polarization beam splitter by the optical recording medium, so that the information signal can be easily reproduced.

〔Example〕

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

As shown in the schematic plan view of FIG. 1 and the schematic side view of FIG. 2, the optical recording / reproducing apparatus of this embodiment has a recording / reproducing light source 1 such as a laser diode. This record
The recording / reproducing light beam emitted from the reproducing light source 1 has a predetermined wavelength of, for example, about 780 nm. In the recording mode, the recording / reproducing light beam is modulated in accordance with an information signal to be recorded to change its intensity. The intensity is lower than the light beam in the mode. The recording / reproducing light beam is indicated by an arrow A in FIGS.
As shown in FIG. 1, the light is in a linearly polarized state in a direction perpendicular to the paper surface in FIG. 1 and in a direction parallel to the paper surface in FIG.

In the recording and reproducing modes, the recording / reproducing light beam is converted into a parallel light beam by the collimating lens 2 and guided to the acousto-optic deflecting element (AOD) 3.

The acousto-optic deflecting element 3 has a medium portion 3a made of an anisotropic crystal such as TeO ₂ or PbMoO ₄ , and the diffraction angle in the Bragg diffraction or the Debye-Shears effect is the same as that of the medium portion.
An element that performs optical deflection control by modulating the frequency of the ultrasonic wave transmitted through the medium portion 3a by utilizing the fact that the frequency is substantially proportional to the frequency of the ultrasonic wave transmitted through the medium portion 3a.

In this embodiment, an anisotropic Bragg diffraction type acousto-optic deflector is used as the acousto-optic deflector 3.
In the medium portion 3a of the acousto-optic deflecting element 3,
The recording / reproducing light beam incident here is separated into a zero-order light beam and a primary light beam by diffraction.

The anisotropic Bragg diffraction type acousto-optic deflecting element 3 includes:
Transducers are provided on both opposing surfaces of the medium portion 3a.
3b and an absorbing portion 3c. The transducer 3b is
It is given from deflection drive unit 3d, by the driving signal V _T which is frequency modulated according to a predetermined scanning signal to generate an ultrasonic wave. When the ultrasonic wave is transmitted through the medium portion 3a, the primary light beam is directed in a direction in which the transducer 3b and the absorbing portion 3c face each other, that is, in a plane parallel to the plane of FIG. Is changed within a predetermined angle range in a direction indicated by an arrow θ in FIG. 2 so that the light is transmitted. This change in the diffraction angle is substantially proportional to the frequency of the ultrasonic wave generated by the transducer 3b. Since the frequency of the ultrasonic wave is frequency-modulated according to the scanning signal, the deflection angle of the primary light beam after passing through the medium portion 3a is controlled by the scanning signal.

The medium section 3a changes the polarization state of the primary light beam. The primary light beam passes through the medium portion 3a, and as shown by an arrow B in FIGS. 1 and 2, the polarization of the recording / reproducing light beam before entering the medium portion 3a. A linear polarization state in a direction orthogonal to the direction is obtained.

The zero-order light beam has the same traveling direction and polarization state as the recording / reproducing beam before entering the medium portion 3a. Therefore, the polarization directions of the primary light beam and the zero-order light beam are orthogonal to each other.

The recording / reproducing light beam split into the zero-order light beam and the primary light beam is guided to the polarization beam splitter 5 via the cylindrical lens 4. As shown by R ₀ in FIG. 1, the polarization beam splitter 5 is disposed such that its reflection surface is parallel to the polarization direction of the polarization light beam. Are reflected by the reflection surface of the polarizing beam splitter 5. 1 above
Order light beam, as described above, since a linear polarization state that is orthogonal to the polarization direction of the 0 order light beam, as shown in FIGS. 1 and 2 in I _1, passes through the polarizing beam splitter 5 I do. Thus, the polarization beam splitter 5 discriminates the zero-order light beam from the primary light beam.

The primary light beam that has passed through the polarizing beam splitter 5 reaches a quarter-wave plate 6. The primary light beam is
The light is converted into a circularly polarized state by the / 4 wavelength plate 6 and reaches the objective lens 9 via the pair of relay lenses 7 and 8. The objective lens 9 focuses the primary light beam on the recording surface 11 of the optical recording medium 10. The optical recording medium 10 is formed in a disk shape, a card shape, a tape shape, or the like, and is formed with the recording surface 11 having photosensitivity.

The primary light beam has passed through the relay lenses 7 and 8 by being subjected to deflection control according to a predetermined scanning signal within a range of a predetermined diffraction angle in a direction indicated by an arrow θ in FIG. Thereafter, deflection is performed within a predetermined angle range in the direction indicated by the arrow λ in FIG. Therefore, the first-order optical beam current is caused to converged on the recording surface 11 spot by the objective lens 9, the second figure from the first focal position indicated by the second figure F ₀
The until a second focal position indicated by F _1, it is scanned in accordance with a predetermined scanning signals. The optical recording medium 10 is driven by a driving means (not shown) in a direction parallel to the plane of FIG. 1 and a direction perpendicular to the plane of FIG. 2 in a direction perpendicular to the scanning direction of the primary light beam. It is moved.

In the recording mode, the recording surface 11 undergoes a chemical or physical change due to the light energy of the primary light beam of the recording light beam to be scanned, and a predetermined information signal is recorded.

In the reproduction mode, the 1
The next light beam is reflected by the recording surface 11 and reaches the objective lens 9, the pair of relay lenses 8, 7 and the quarter-wave plate 6. At this time, the primary light beam is in a circularly polarized state in a direction opposite to that before reflection on the recording surface 11. Therefore, as shown by an arrow C in FIGS. 1 and 2, by passing through the quarter-wave plate 6, the light passes through the acousto-optic deflecting element 3 and then enters the quarter-wave plate 5. A linear polarization state in a direction orthogonal to the polarization direction of the previous primary light beam is obtained. Therefore, the first-order optical beams, as shown in FIG. 1 in R _1, is reflected by the reflecting surface of the polarization beam splitter 5, it is guided to the detection lens 12. The detection lens 12 is a light detector for detecting the primary light beam.
Focus on 13 The photodetector 13 receives the primary light beam and outputs a reproduction signal.

In the optical recording / reproducing apparatus of this embodiment, as described above, the zero-order light beam transmitted through the acousto-optic deflecting element 3 is discriminated by the polarization beam splitter 5 and reaches the recording surface 11. Absent. Therefore, over the entire scanning range of the primary light beam on the recording surface 11,
Accurate recording and reproduction of information signals can be performed. In the reproduction mode, the primary light beam reflected by the recording surface 11 is extracted from the optical path returning to the recording / reproduction light source 1 by the polarization beam splitter 5, so that the light beam is easily emitted. The information signal is detected by the detector 13 and reproduced.

The present invention is not limited to the above-described embodiment, but can be appropriately changed. For example, in the above-described embodiment, the zero-order light beam is output from the polarization beam splitter 5.
The primary light beam is transmitted through the polarizing beam splitter 5 and reaches the recording medium 10, but the zero-order light beam is reflected by the zero-order light beam as shown in FIG. The primary light beam transmitted through the polarization beam splitter 5 may be reflected by the reflection surface of the polarization beam splitter 5 to reach the recording medium 10.

In the example shown in FIG. 3, the polarization beam splitter 5 is disposed such that its reflection surface is parallel to the polarization direction of the primary light beam indicated by an arrow B in FIG. The first-order optical beam by the reflecting surface of the polarization beam splitter 5 is reflected as shown by FIG. 3, R ₁ and toward the optical recording medium 10 through the quarter-wave plate 6. Since the zero-order light beam is linearly polarized light in a direction orthogonal to the polarization direction of the primary light beam indicated by an arrow A in FIG. 3, the polarization beam splitter is indicated by I ₀ in FIG. 5 is transmitted. Then, the reflected light beam of the primary light beam by the recording surface 11 is orthogonal to the polarization direction of the primary light beam before being incident on the polarization beam splitter 5, as indicated by arrow C in FIG. since the linearly polarized light state of the direction, and transmitted through the polarizing beam splitter 5 as indicated by Figure 3 in I _1, leading to the detection lens 12. This third
Also in the example shown in the drawing, the light beam reflected by the recording surface 11 is extracted as described above, so that the same effect as in the above-described embodiment can be obtained.

The cylindrical lens 4 and the pair of relay lenses
7, 8 are not indispensable for the implementation of the present invention, and can be omitted as appropriate.

〔The invention's effect〕

As described above, in the optical recording / reproducing apparatus according to the present invention, the primary light beam whose deflection is controlled by the acousto-optic deflecting element and the zero-order light beam whose deflection is not controlled are discriminated by the polarizing beam splitter, and the primary light beam is discriminated. The beam reaches the recording surface of the optical recording medium via the quarter-wave plate. Then, the primary light beam reflected by the recording surface is extracted by the polarization beam splitter.

Therefore, the above-mentioned 0 which is not involved in the recording / reproduction of the information signal.
The secondary light beam is prevented from reaching the optical recording medium, and recording / reproduction can be performed over the entire scanning range of the primary light beam.

Extracting the reflected light beam of the primary light beam from the recording surface is performed by the same polarization beam splitter as the polarization beam splitter that discriminates the zero-order light beam from the primary light beam. That is, since one polarizing beam splitter has two functions, simplification and downsizing of the device configuration can be achieved.

That is, the present invention can be achieved with a simple and compact device configuration by guaranteeing accurate recording / reproduction over the entire scanning range of the primary light beam and improving the recording density. It is possible to provide an optical recording / reproducing apparatus that has been made.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing a configuration of an embodiment of an optical recording / reproducing apparatus according to the present invention, and FIG. 2 is a schematic side view showing a configuration of an embodiment of the optical recording / reproducing apparatus. FIG. 3 is a schematic diagram showing an arrangement of a polarization beam splitter which is a main part of another embodiment of the optical recording / reproducing apparatus. FIG. 4 is a schematic side view showing a configuration of a conventional optical recording / reproducing apparatus using an acousto-optic deflecting element. DESCRIPTION OF SYMBOLS 1 ... Light source for recording / reproduction 3 ... Acousto-optic deflecting element 5 ... Polarization beam splitter 6 ... 1/4 wavelength plate 9 ... Objective lens 10 ... Optical recording medium 13 ... Photodetector

Claims (1)

(57) [Claims] 1. A light beam in a linearly polarized state is incident on an acousto-optic deflecting element such that the deflection direction of the acousto-optic deflecting element and the polarization direction are parallel to each other, and the zero-order light transmitted through the acousto-optic deflecting element. A light beam and a primary light beam whose deflection is controlled by the acousto-optic deflecting element according to the scanning signal are discriminated by a polarizing beam splitter, and the primary light beam is radiated through a quarter-wave plate. The reflected light beam is projected onto a recording medium, and the reflected light beam from the optical recording medium is guided to the polarization beam splitter through the quarter-wave plate, and the reflected light beam is extracted by the polarization beam splitter to perform optical recording. An optical recording / reproducing device for reproducing.