JPS60121548A - Optical disk recorder - Google Patents

Abstract

PURPOSE:To obtain an optical disk recorder which can reduce the viewfield of an objective lens in increasing the density of a recording channel, by controlling the positioning to an image formed with two recording beams so that it is formed on a guide track in satisfying the specific conditions. CONSTITUTION:A control beam is formed into an image on a guide track TR, and also two recording beams are formed into images opposite to each other centering on the guide track and with a space secured to the control beam. The positioning control is carried out so that the images formed with two recording beams satisfies D>(D1+D2)/2+G and D Q/2, where D shows the center distance between the images formed on an optical disk with two recording beams, D1 and D2 show the diameters of both images respectively, G is the width of the guide track and Q is the pitch of the guide track respectively. Thus it is avoided that the images formed by two recording beams are positioned at front and back positioned to each other in the track direction. At the same time, the density is improved for the recording channel. This also secures the effective use of the viewfield of an objective lens and therefore can reduce said viewfield.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical disk recording device configured to record information on an optical disk provided with a guide track for controlling the image position of a beam.

BACKGROUND ART AND PROBLEMS There have not been many reports on optical disk recording regarding multi-channel recording to increase the recording channel density.

For example, using a monolithic semiconductor laser in which multiple lasers are formed on one substrate, multiple individually modulated beams are lined up in a straight line that is oblique to the track direction on an optical disk. It has been proposed that the image be imaged on the camera and recorded on multiple channels.

However, according to this method, there is a problem that the images formed by the recording beam are positioned one after the other in the track direction, and furthermore, there is a restriction that the images are formed in a straight line, so the objective lens The problem is that a wide field of view is required.

OBJECTS OF THE INVENTION The present invention was invented in view of the above-mentioned problems, and its purpose is to increase the density of recording channels while making it possible for images formed by recording beams to move back and forth in the track direction. It is an object of the present invention to provide an optical disk recording device which is not located in a dark position and requires a small field of view of an objective lens.

Summary of the Invention The optical disc recording device according to the present invention includes one control beam and two recording beams, and directs the one control beam onto the guide track in the optical disc. and forming the two recording beams so as to face each other with the guide track in between, and to separate the two recording beams from each other spatially with respect to the control beam;
Furthermore, the image formed by the two recording beams is D>d(
D1+D2)+G (In the formula, D is the center distance of the images of the two recording beams formed by focusing on the optical disk, and Dl is the distance between the centers of the images of the two recording beams formed by focusing on the optical disk. (D2 is the diameter of the image of the recording beam, D2 is the diameter of the image of the other recording beam of the two recording beams formed by focusing on the optical disk, and G is the width of the guide track.) , the image formed by the recording beam is positioned by controlling the positioning so that the image formed by the control beam is formed on the guide track.

As a result, while increasing the recording channel density, the images formed by the recording beam are not positioned one after the other in the track direction, and the field of view of the objective lens can be effectively used, so that the beams are aligned in a straight line on the optical disk. The field of view of the objective lens is small compared to what is being imaged.

Embodiment Next, a specific embodiment of the optical disc recording apparatus according to the present invention will be described with reference to the drawings.

FIG. 1 is an overall diagram of the optical system.

The beam emitted from the light emitting point S1 of the first semiconductor laser (LDl) and used as the recording beam is converted into a parallel beam by the first collimator lens (C(JL,). This parallel beam has a specific wavelength. The first dichroic beam splitter (DB
S, ). In addition, a second semiconductor laser (LD
2) The beams emitted from the pair of light emitting points S2 and S5, the control beam from the light emitting point 82 and the recording beam from the light emitting point 83, are passed through a second collimator lens (COL2). ) into a parallel beam,
Similarly, the first dichroic beam splitter (DBS)
1). Note that the second semiconductor laser (LD2
) is monolithic, and by forming two lasers on one substrate, the pair of light emitting points 82%S5
It is equipped with Therefore, a pair of light emitting points S2.8S
The wavelengths of the beams emitted from each are the same.

By the way, the light emitting point S1 of the first semiconductor laser (LDl)
and the wavelength of the beam from the second semiconductor laser (LD2).
The wavelengths of the beams from the light emitting points s2 and b are different from each other. In this embodiment, for the first tichroic beam splitter (DBS), the former is selected as the wavelength to be transmitted, and the latter is selected as the wavelength to be reflected.

Therefore, the first dichroic beam splitter (D
In il), the recording beam from the first semiconductor laser (LDl) is transmitted, and the recording beam from the second semiconductor laser (LD2) is transmitted.
The control beam and the recording beam from the are reflected, and the beams are combined and emitted.

This emitted composite beam consisting of one control beam and two recording beams is produced by a polarizing beam splitter (PBS) that separates beams with different deflection axes and changes the direction of the beam in the forward and backward directions. is incident on the The combined beam passes through this polarization beam splitter (PBS), and a three-wavelength plate (QWP), which rotates the polarization axis by 45 degrees, is used.
A reflector (M) forming a 5 degree reflection angle and an objective lens (
(JL) and the recording surface I of the optical disc (D,).
This beam is incident and imaged.

On the recording surface of the optical disc (D), there is a first disc as shown in the figure.
Images (1) to (3) are formed corresponding to the recording beam from the second semiconductor laser (LDl) and the control beam and recording beam from the second semiconductor laser (LD2), respectively. By the way, the optical disk (D) is disk-shaped, and on its recording surface, a guide track (TR) for device control consisting of a bit string of a certain length with a certain spatial frequency is provided in a spiral or concentric form. ing.

Next, the combined beam reflected from the recording surface of the optical disk (D) is picked up by the objective lens (OL), follows the optical path in the reverse direction, and passes through the reflector (M) and human wave plate (QWP) in sequence again. and enters a polarizing beam splitter (PBS). At this time, since the combined beam passes through the human wave plate (QWP) twice, the deflection axis differs in wavelength by % compared to the other beam. Therefore, the optical disc (D, l
The reflected combined beam from is reflected at the polarizing beam splitter (PBS) and incident on the dichroic beam splitter (DBS2) of mud 2, which is similar to the first dichroic beam splitter (DBS, ).

However, $1 of the semiconductor laser (L
The recording beam from Dl) is reflected and passes through a convex lens (Ll
) and is incident on the first photodetector (PDl) and imaged. The control beam and recording beam from the second semiconductor laser (LD2) of the combined beam are transmitted and sequentially passed through a convex lens (L2) and a cylindrical lens (CYL) for focus error detection. The light is incident on the second photodetector (PD2) and is imaged.

By the way, the control beam focused on the second photodetector (PD2) causes focus errors due to the astigmatism method, and furthermore, the so-called DPD method based on the high-frequency signal. Tracking error is detected. The objective lens (OL) is driven in the focusing direction and the tracking direction by the focus error signal and tracking error signal based on this detection, and the focus lens and tracking are performed.

Next, the image formation of one control beam and two recording beams on the recording surface of an optical disk will be described with reference to FIG.

The control beam from the light emitting point S2 of the second semiconductor laser (LD2) is directed to a guide track ('l') by drive control of the objective lens (OL) using the tracking error signal, etc.
R), and the image I2 is formed on the guide track (T
R) Positioning is controlled on the top. Further, the recording beam from the light emitting point S1 of the first semiconductor laser (LDl) and the recording beam from the light emitting shield S of the second semiconductor laser (LD2) are formed by imaging the control beam as described above. 1#I2 is positioned on the kite track and is controlled, so that it is imaged so as to be located spatially apart from the control beam and opposite to the guide track (TR). That is, images 1. , I, is imaged by the same objective lens (OL) as the control beam, so it is correctly positioned by controlling the positioning of the image 12 of the control beam on the guide track (TR). This allows for stable and high beat rate recording.

Therefore, between the three images 11 to 13 forming an isosceles triangle whose base is the line connecting the centers of the recording beam images 11 and 13, and whose apex is the center of the control beam image 2, In addition to this, which images the recording beam spatially apart from the control beam, a guide track ('IR
), the following equation is satisfied.

q>p1+D2+c+ 1 D? -Q L>D D; Recording beam image 11. I, center distance D1; first
diameter D2 of the recording beam image 11 of the second semiconductor laser (LD1); diameter G of the control beam and recording beam images 12 and 15 of the second semiconductor laser (LD2); width L of the guide track (TR); control The center of the beam image 12 and the recording beam image 11.
Distance Q from each center of 15; Pitch of guide track (TR); Image quality of each control beam and recording beam.

The diameters D1 and D2 of ~I3 are determined by the wavelength of the beam and the numerical aperture of the objective lens (OL).

Further, the positional relationship of the control beam and the recording beam to form the above-mentioned isosceles triangle of *11 to 1° is such that the first and second semiconductor lasers corresponding to the first and second collimator lenses (COLl) (COL2), respectively This is achieved by adjusting the arrangement of (LDIXLD2) and further the rotation of the entire optical system around the optical axis A.

In this example, by using semiconductor lasers (LDl) (LD2) to obtain the control beam and the recording beam as described above, the characteristics of their compactness and ability to modulate optical output power by direct current modulation are taken advantage of. However, although the second semiconductor laser (LIj2) is monolithic, intermodulation due to thermal coupling between lasers formed on one substrate, which is a drawback of monolithic semiconductor lasers, is CW. This is reduced by high-frequency modulation of the control beam side of the oscillation and by synchronously detecting and extracting servo signals such as tracking error signals. in general,
High frequency modulation suppresses the noise induced by the reflected beam, so the C/N ratio (c
arrival-to-noise-ra tio
) is improved and favorable results are obtained.

By the way, in this example, the wavelengths of the beams of the first and second semiconductor lasers (LDl) (LD2) were made different, but if the control beam can be sufficiently spatially separated from the recording beam, they can be of the same wavelength. Separation is possible at the photodetector (PD2). Further, in this embodiment, the guide track (TR) is a bit string of a constant length, but a DC groove may also be used, and in this case, tracking errors will be detected by the push-pull method.

Effect of the invention The present invention has the following advantages.

(2) Since the two recording beams are imaged to face each other with the guide track in between, the images formed by the recording beams are not positioned one after the other in the track direction.

■, one control beam is imaged on the guide track,
Two recording beams are imaged so as to be spatially separated from the control beam and to face each other across the guide track.

That is, the images formed by one control beam and two recording beams form an isosceles triangle positional relationship. Therefore, the field of view of the objective lens can be used effectively,
Compared to an optical disk in which the beams are imaged on a single line, the field of view of the objective lens is smaller.

(2) Since the control beam and recording beam are clearly separated, there is no mutual interference. In particular, since using a bit string as a guide track has almost no effect on the recording beam, the so-called DI method using the Takaoka 1 signal, which is advantageous for disk skew, is used to detect tracking errors using a bit string guide track. be able to.

[Brief explanation of the drawing]

1 and 2 are for explaining the optical disk recording device according to the present invention, FIG. 1 is an overall view of the optical system, and FIG. 2 is a control beam and recording on the recording surface of the optical disk. FIG. 2 is an enlarged view showing the mutual positional relationship of images formed by beam imaging. In addition, in the symbols used in the drawings, CD, )...... Optical disc (TR)
This is a guide track for... Agent Masaru Ueya Tsuneko Hoyu 2nd drawing 口 口 口 口 1ノ″ 口 ゛口口 z、Is ○口○ 口郎一次へ－←－ (Voluntary) Procedural amendment 1980, 24th Mr. Nong, Commissioner of the Patent Office, 1. Indication of the Case 1988 Patent Application No. 229575 2゛'"') 88 Relationship to the optical disk recording device case
Patent applicant Tokyo 1fIX No. 35, Roa 1 Hill, 6-chome, Kitashinagawa, Shinagawa-ku (218
) Sony Corporation 5, Date of supplementary order (shipment date) Showa year, month, day et al.
Amendment 1 The number of inventions increased by 7, Detailed description of the invention column 8 in the specification subject to amendment, Contents of amendment (1j1 "Deflection axis" on page 7, line 1 of the specification and page 8, line 5) (2) Correct the "polarization beam splitter" on page 7, line 6, page 7, line 4, page 8, line 2, and @page 8, line 7. Respectively[
Polarized beam splinter” and correct. (3), "Rotate the deflection axis by 45 degrees" in lines 5 and 6 on page 7 is corrected to "create a phase difference of 190 degrees." (4), page 8, lines 5-6 [number wavelengths are different. ” is corrected to “rotated by 90 degrees.” (5), "High beat rate" in the 10th line of the 10th member is "
"High bitrate". −1 above

Claims (1)

[Scope of Claim] An optical disk recording device configured to record information on an optical disk provided with a guide track for controlling the image position of the beam, comprising one control beam and two recording beams. In addition, in the optical disc, the
The two control beams are imaged on the kite track and are spatially separated from the control beam, and the two recording beams are imaged to face each other with the guide track sandwiched between them. (In the formula, D is the center distance of the two recording beams formed by focusing on the optical disk, and Dl is the center distance of the two recording beams formed by focusing on the optical disk.) , D2 is the diameter of the other recording beam of the two recording beams formed by focusing on the optical disk, and G is the width of the guide track. ), and the image formed by the recording beam is positioned by controlling the positioning so that the image formed by the control beam is formed on the guide track. Optical disk recording device.