JPH04263127A - Recording device of optical recording medium - Google Patents

Abstract

PURPOSE:To control an irradiation position with high accuracy and response using a compact of a inexpensive actuator by controlling a relative position of a plurality of optical beams which irradiate a recording medium using a wedge prism. CONSTITUTION:A light relay uses a wedge prism 15. Then, a member which can be rotated freely and carries this wedge prism 15 is operated by an actuator 17 which is a positioning means operated according to this wedge prism 15. In this case, even if a deviation from an optical axis of an optical beam is canceled and the prism 15 is rotated, it becomes possible to allow the optical beam to enter nearly a center of an objective lens 9. Thus, by selecting a plate thickness of the wedge prism 15 properly, the optical beam enters an incidence pupil of the objective lens 9, thus preventing light from being kicked.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus that records information signals by irradiating an optical recording medium with a plurality of light beams.

0002

[Background Art] It is widely known that a light beam carrying multiple information signals is irradiated onto an optical disc master such as a glass master to record information signals, and then an optical disc for playback is formed based on this master. There is. In particular, a device has recently been developed that divides a wideband video signal such as a high-definition signal into three channel signals and records them on a single disc.
Practical implementation is underway.

In FIG. 6, a light beam P0 emitted from a laser light source 1 is reflected by a mirror 2 and formed into a half mirror.
3a. In the half mirror 3a, 1/3 of the amount of the incident light beam is transmitted and 2/3 is reflected. The transmitted light beam P1 is incident on the pulse modulator 4a. The reflected light beam is incident on the half mirror 3b, where half of it is transmitted and the other half is reflected. The reflected light beam P2 enters the pulse modulator 4b, and the transmitted light beam P3 is reflected by the mirror 3c and enters the pulse modulator 4.
It is incident on c. Therefore, the three light beams P1, P2,
The light amounts of P3 are equal to each other. The three pulse modulators 4 are so-called AOM (Acoustic Optica).
This is a light modulation means called a modulator, which modulates a light beam into a pulse signal according to an input signal supplied thereto.

On the other hand, three video signals from a high-definition baseband signal source (not shown) are supplied to an FM modulator 5 as signal generating means. FM modulator 5a,
Each of the modulated video signals from 5b, 5c is provided to a respective pulse modulator 4a, 4b, 4c. In the pulse modulator 4, each light beam S1, S2, S3 pulse-modulated by the video signals 1 to 3 is irradiated onto a recording medium by an irradiation means described below.

The light beam S1 is reflected by a mirror 6a and transmitted through beam splitters 6b and 6c. The pulse-modulated light beam S2 from the pulse modulator 4b is reflected by the beam splitter 6b and transmitted through the beam splitter 6c. Similarly, the light beam S3 from the pulse modulator 4c is reflected by the beam splitter 6c. These three light beams S1, S2, and S3 are connected to an optical repeater 7 which is an optical repeater.
After passing through the beam splitter 8, it is reflected by the objective lens 8.
The light is focused and irradiated onto the glass master disk 9. Glass master 9
is rotationally driven by a spindle motor 10 at a constant linear velocity or angular velocity.

[0006] On the glass master disk 10, three optical beams S1, S2, and S3 form a set of three tracks, on which each video signal is recorded. During this recording, relative irradiation positions are controlled so that the three light beams form parallel tracks. The irradiated light beam is reflected by the irradiated surface (recording surface) of the glass master 10, and the returned beam is supplied to the imaging section 12, which is a detection means such as a CCD camera. In the imaging unit 12, the light beam S
The relative irradiation positions of 1, S2, and S3 are detected and a position signal is generated. This allows highly accurate relative position detection by detecting the number of horizontal scanning lines existing between each spot of the return beam on the imaging plane.

This position signal is supplied to the position control circuit 13, which is a control means, and is compared with a reference value indicating the correct relative irradiation position.The difference, that is, an error signal, is generated as an irradiation control signal to control the light. is applied to repeater 7. In the optical repeater 7, the relative irradiation positions of the light beams S1, S2, and S3 irradiated onto the glass master 10 are controlled according to the irradiation control signal.

Specifically, as shown in FIGS. 9 and 10, the relative irradiation positions of the spot of the main beam S1 of the recording beam and the spots of the light beams S2 and S3 on both sides are shifted in the radial direction. In this case, position control in the tangential direction, that is, the track direction is not performed. The deviation of the relative illumination position of the light beam is controlled by varying the angle of incidence of the beam on the objective lens.

In FIG. 9, the amount of deviation Δy of the light beam in the radial direction on the glass master disk 10 must be controlled with an accuracy of ±0.01 μm. Optical deflector 7 of optical repeater 7
The light beam emitted from a passes through a beam expander first lens 7b with a focal length f1 of 30 mm and a beam expander second lens 7c with a focal length f2 of 120 mm, and is converged by an objective lens (f=2.69 mm) 9. and irradiated. If the optical path length L1 from the optical deflector 7a to the beam expander first lens 7b is 670 mm, Δy=
Beam expander first lens 7 for 0.01 μm
The incident angle Δθ to b is approximately 1.5×10−5 rad. It is known that Therefore, the optical deflector 7a must have a minimum deflection angle of Δθ or less. Also, the relative position control range needs to be ±0.1 μm, so the incident angle is ±1.5×10-4 rad. must cover the range of

Conventionally, an AOD (optical optical deflector) or a rotating mirror is used as the optical deflector 7a. The AOD utilizes the fact that a high-frequency electric signal with a center frequency of about 300 MHz is input, and by changing the center frequency, the diffraction angle of the first-order diffracted light changes. An example of using an AOD is disclosed in Japanese Patent Laid-Open No. 62-28233. However, in this disclosed example, AOM4,
Since modulation and deflection of the light beam are performed separately using the AOD 5 and AOD 8, there is a drawback that the attenuation of the light beam becomes large. Therefore, it is conceivable to modulate and deflect the light beam using one AOD. However, in this method, in order to obtain the desired relative control position range (±0.1 μm in this case), A
The light beam passing through the OD deviates greatly from the point on the optical axis where the beam waist, that is, the beam spot is at its minimum, and the beam spot becomes large. However, the AOD has a property that the responsiveness deteriorates as the passing beam spot becomes larger, and a problem arises in that a control position range of ±0.1 μm cannot be obtained. Furthermore, the optical path length from the AOD to the beam expander first lens 7b is long, which causes the problem that the light is eclipsed from the entrance pupil to the objective lens 9.

On the other hand, a technique using a rotating mirror is disclosed in, for example, Japanese Unexamined Patent Publication No. 62-283426. In FIG. 10, in order to obtain Δy=0.01 μm in the glass master 10, Δθ=1.5×1
0-5rad. A deflection angle of the light beam S1 is required. In this case, the minimum rotation angle of the rotating mirror 14 is Δθ/2, or approximately 7.5×10 −6 rad. It becomes below. Mirror 14a
If the distance from the center of rotation to the point of action M of the mirror support 14b is 40 mm, the operating range of the point of action M is 0.3
It becomes μm. Generally, a DC motor, a stepping motor, or a piezo is conventionally used as an actuator for driving the rotating mirror 14. However, it is difficult to obtain an accuracy of 0.3 μm with a DC motor, which is possible with a stepping motor. However, in this case, a large stepping motor is required, which also poses a problem in terms of miniaturization of the device. Also, piezo is 0.3μ
Although the operation of m is possible, it has the disadvantage that it changes over time.

0012

[Object of the Invention] Therefore, an object of the present invention is to control the relative irradiation position of a light beam with high precision and good response even when using a small and inexpensive actuator such as a DC motor. An object of the present invention is to provide a recording device for an optical recording medium having an optical repeater.

[0013]

SUMMARY OF THE INVENTION A recording device for an optical recording medium according to the present invention includes: a light source that emits a plurality of light beams; a signal generating means that generates a plurality of information signals as many as the plurality of light beams; a plurality of modulated light beams by modulating each of them with each of the information signals; an irradiation means for irradiating each of the modulated light beams onto a recording medium; and a light modulation means for irradiating each of the modulated light beams onto a recording medium; a detection means for detecting relative irradiation positions between the light beams and emitting a position signal; a control means for generating an irradiation control signal in accordance with the position signal; and at least one of the modulated light beams emitted from the light modulation means. 1 to the irradiation means, wherein the optical relay means includes a wedge prism that receives at least one of the modulated light beams on its entrance surface; and positioning means for adjusting the angle of incidence of the modulated light beam incident thereon by adjusting the wedge prism according to the angle of incidence of the modulated light beam.

[0014]

In the optical recording medium recording apparatus according to the present invention, a wedge prism is used to control the relative irradiation positions of a plurality of light beams irradiated onto the recording medium.

[0015]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 5. As shown in FIG. 1, a wedge prism 15 is used in the optical repeater 7. An actuator 17, which is a positioning means that operates in response to an irradiation control signal, operates a rotatable member (not shown) that supports this wedge prism 15. With this operation, the incident angle Δθ = 1.5 that satisfies the condition of deviation amount Δy = 0.01 μm
×10-5 rad. The deflection angle of wedge prism 15
The apex angle of 1deg. , the angle of incidence on the wedge prism 15 is set to 8deg. In this case, the angular rotation angle Δθw of the wedge prism 15 is 6.9×10 −3 rad. It can be obtained by In other words, the relationship between Δθ and Δθw is Δθw/Δθ
=460, Δθw is a rotation angle 460 times as large as Δθ, and the critical adjustment of the rotation angle as in the prior art can be eliminated. If the distance l from the rotation center of the wedge prism 15 to the point of action is 30 mm, the working distance Δx of the wedge prism 15 at the point of action is:
From Δx=l×Δθw, it becomes 0.207 mm. This working distance can be sufficiently achieved even if a DC motor is used for the actuator 17.

The wavelength λ of the light beam is a laser beam of 406.7 mm, a synthetic quartz wedge prism with a refractive index of 1.469432 and a thickness of 4.74 mm is used, and a beam expander first lens 7 is connected from the wedge prism 15.
When the optical path length L to b is 661 mm and the focal length ratio of the beam expander lens f2/f1 = -3,
The deviation of the light beam from the optical axis is canceled, and even if the wedge prism 15 rotates, the light beam can be made to enter approximately the center of the objective lens 9. By appropriately selecting the thickness of the wedge prism 15 in this way,
Since the light beam enters the entrance pupil of the objective lens 9, vignetting of the light can be avoided.

Specific examples using the wedge prism 15 are shown in FIGS. 2 to 5. In the first embodiment shown in FIG. 2, a main beam S1 and other light beams S2 and S3 are incident on the optical repeater 7 after being reflected by mirrors 16a, 16b, and 16c. The main beam S1 is directly incident on the folding mirror 7d, while the other light beams S2 and S3 are incident on the folding mirror 7d via wedge prisms 15a and 15b, respectively. The three light beams reflected by the folding mirror 7d are reflected again by the next folding mirror 7e and enter the beam expander first lens 7b. In this case, the light utilization efficiency is approximately 100%.

In the second embodiment shown in FIG. 3, the relative positions to be irradiated are in the pattern shown in the eighth pattern. In this embodiment, first, the relative positions of the main beam S1 and the light beams S2 and S3 in the track direction are adjusted by a wedge prism 15a that refracts the light beam in a direction perpendicular to the paper plane of FIG. , and further wedge prism 15
b and 15c adjust the relative positions of the light beams S2 and S3 in the radial direction. In this case as well, the light utilization efficiency is close to 100%.

In the third embodiment shown in FIG. 4, the light utilization efficiency is 50%, which is lower than the first and second embodiments, but it has the advantage that the optical path length can be shortened, and the relative As for the position, both the patterns shown in FIGS. 7 and 8 are possible. Also, Figure 5
In the fourth embodiment shown in FIG.
Although it becomes worse at 3%, the optical path length can be shortened as in the third embodiment, and both the irradiation patterns shown in FIGS. 7 and 8 are possible. This fourth embodiment has the advantage that the structure of the optical repeater 7 can be simplified by providing the diffraction grating 18.

[0020]

As explained above, in the optical recording medium recording apparatus according to the present invention, the relative positions of the plurality of light beams irradiated onto the recording medium are controlled using a wedge prism, so the apparatus is small and inexpensive. Using an actuator, it is possible to control the irradiation position with high precision and high responsiveness.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the operating principle of a wedge prism used in an optical repeater according to the present invention.

FIG. 2 is a configuration diagram of a first embodiment using the wedge prism of FIG. 1;

FIG. 3 is a configuration diagram of a second embodiment using the wedge prism of FIG. 1;

FIG. 4 is a configuration diagram of a third embodiment using the wedge prism of FIG. 1;

FIG. 5 is a configuration diagram of a fourth embodiment using the wedge prism of FIG. 1;

FIG. 6 is a block diagram common to the present invention and a conventional recording device.

7 is a pattern diagram of a light beam irradiated onto the glass master disk 10 in FIG. 6. FIG.

8 is a pattern diagram of a light beam irradiated onto the glass master disk 10 in FIG. 6. FIG.

FIG. 9 is a structural diagram of the optical repeater 7 in FIG. 6.

FIG. 10 is a principle diagram of a conventional rotating mirror type optical repeater 7.

[Explanation of symbols]

7...Optical repeater 9...Objective lens 10...Glass master 12...Imaging section 13...Position control circuit 15... Wedge prism 17...actuator

Claims (1)

[Claims] 1. A light source that emits a plurality of light beams, a signal generating means that generates a plurality of information signals as many as the plurality of light beams, and a light source that modulates each of the light beams with each of the information signals. a light modulating means for generating a plurality of modulated light beams, an irradiation means for irradiating each of the modulated light beams onto a recording medium, and a means for detecting relative irradiation positions between the modulated light beams irradiated onto the recording medium a detection means for emitting a position signal using the light beam; a control means for generating an irradiation control signal in response to the position signal; and an optical relay means for relaying at least one of the modulated light beams emitted from the light modulation means to the irradiation means. The optical relay means includes a wedge prism that receives at least one of the modulated light beams on its entrance surface, and adjusts the wedge prism according to the irradiation control signal to make the light enter the beam. A recording device for an optical recording medium, comprising positioning means for adjusting the incident angle of the modulated light beam.