JP3215760B2 - Optical recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus for recording and reproducing information on a recording medium by light, and more particularly, to an optical recording / reproducing apparatus.
The present invention relates to an optical recording / reproducing apparatus capable of forming a plurality of spots on a recording medium and simultaneously recording and reproducing on a plurality of tracks.

[0002]

2. Description of the Related Art Hitherto, in order to further improve the recording / reproducing speed, an optical recording / reproducing apparatus adopting a multi-beam system for scanning spots formed by a plurality of beams on different tracks has been devised.

In a multi-beam optical recording / reproducing system, the focal length error of a lens, the variation in the interval between light emitting points of a multi-point light emitting semiconductor laser used as a light source, etc.
There is a possibility that the interval between the condensed spots on the recording medium does not match the width of the recording track.

If the spot width does not match the track width,
Since at least a part of the spot picks up a signal from a position shifted from the track, there is a problem that an error rate of a reproduced signal using light reflected by the spot increases.

Conventionally, an image rotator provided between a light source and an objective lens is rotated and adjusted in order to make each spot coincide with a corresponding track, so that a spot row on a recording medium is moved in the track direction. A method is known in which each spot is adjusted to each track without tilting the spot and changing the spot interval.

[0006]

However, in the above-described conventional adjusting method, spots other than the center of rotation move not only in the track width direction but also in the direction along the track. There is a problem that information recorded and reproduced has a time lag between the data and other spots.

In particular, a VTR for a tape-shaped recording medium
In an optical recording / reproducing apparatus using a head that rotates so as to cross in the width direction of the tape as in the helical scan method, when the spot row is tilted, the spot width fluctuates within the tape width as shown in FIG. Track adjustment could not be performed.

In addition to the above-described method of tilting the row of spots, other means for changing the interval between spots themselves include a first method of changing the zoom ratio by tilting a beam shaping prism, and a second method of changing a photographic lens. A method is conceivable in which the zooming lens group and the image position change correcting lens group are respectively position-controlled to change the magnification, such as a zoom lens used.

However, in the first method, it is necessary to reversely rotate the two prisms about the optical axis in order to keep the emission angle constant and not to change the direction of the spot row. Although this method is theoretically possible, it has a problem in responsiveness and is not suitable as a means used for correcting a tracking error in an actual operating environment.

In the case of the second method as well, the structure is complicated to control the positions of the two lens groups, and mounting is difficult.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and in an optical recording / reproducing apparatus of a multi-beam system, the distance between a plurality of spots formed on a recording medium is made simple. It is an object of the present invention to provide a device having a mechanism capable of adjusting the responsiveness.

[0012]

In order to achieve the above object, an optical recording / reproducing apparatus according to the present invention has a light source section for generating a plurality of light beams and a plurality of light beams from the light source section on a recording medium. An objective lens that forms an image as a spot ,
Different spots formed by multiple beams
Multi-beam optical recording / reproduction operated on tracks
In the device, light between the light source unit and the objective lens
It is provided so that it can move on the axis, and moves back and forth in the optical axis direction.
Image magnification changes around + 1x, including + 1x
And the movement changes the imaging magnification of the entire system.
It is characterized by having a lens that can be used. Where
The imaging magnification of the body is the imaging magnification of the lens itself,
Object point incident on the lens and the image formed by the lens
Is the horizontal magnification.

[0013]

Embodiments of the present invention will be described below. FIG.
Shows an outline of the optical system of the optical tape system of the embodiment.

A magnetic film is formed on the surface of the optical tape, and the recording / reproducing apparatus records information using heat and a magnetic field of light and reflects the information in the same manner as a commonly used magneto-optical disk apparatus. The recorded information is reproduced using the magnetic Kerr effect at the time.

A plurality of beams emitted from the multi-point light emitting semiconductor laser 1 are converted into parallel light beams by a collimating lens 2, and the cross section of each beam is circular through a beam shaping optical system 20 composed of two prisms. Is corrected to The shaped light beam passes through the first beam splitter 3 and is once converged by the condenser lens 4.

The lens 5 is provided at a position where the light beam converged by the condenser lens 4 diverges, and has an image forming magnification of +
It is movable in the optical axis direction so as to change the magnification within a range including 1 ×. The light beam transmitted through the lens 5 is converted into a substantially parallel light beam by the servo lens 6 and relayed by the relay lenses 7 and 8. The servo lens 6 is provided so as to be displaceable in an optical axis direction and a direction orthogonal to the optical axis for focusing and tracking. As a result, this lens
5 slightly in the optical axis direction before and after the imaging magnification of itself is +1 times.
The spot width equals the track width.
It is possible to adjust the imaging magnification of the whole system enough to match
However, the image forming position based on the movement of the lens 5 at this time is
The change is very small compared to the amount of movement of the lens 5. to this
The focus shift is minimal and only the image magnification can be adjusted
An optical system is obtained.

The optical elements from the semiconductor laser 1 to the relay lens 8 are provided on a fixed part A.

The light beam emitted from the relay lens 8 is reflected off the optical axis of the incident light beam by the first reflecting surface 9a of a prism 9 as a deflecting member provided in the rotary head B,
The light is reflected again by the reflection surface 9b in a direction parallel to the incident light beam. The rotating head B has its optical axis Ax relative to the fixed part A.
Rotate around. R is the radius of gyration.

The light beam reflected from the prism 9 enters the objective lens 10 and forms a plurality of spots spaced apart in the longitudinal direction of the tape on an optical tape 11 as a recording medium. Therefore, recording / reproduction can be performed on a plurality of tracks in one rotation.

The spot on the optical tape 11 moves as shown in FIG. 2 by the rotation of the head. To adjust the distance between the spots, move the lens 5 in the optical axis direction.
Change the magnification of the whole system . Thereby, the spot interval can be changed without changing the direction of the spot row.

The light beam reflected from the optical tape 11 becomes a parallel light beam through the objective lens 10 again, and becomes a parallel light beam.
7, the light enters the first beam splitter 3 via the servo lens 6, the lens 5, and the condenser lens 4. The luminous flux reflected by the first beam splitter 3 is converted into a 波長 wavelength plate 12
Rotates the polarization direction by 45 degrees, and is separated by the polarization beam splitter 13 into P and S polarization components.

P transmitted through the polarizing beam splitter 13
The polarized light component is transmitted to the first light receiving element 15 by the condenser lens 14.
Focused on top. The S-polarized light component reflected by the polarization beam splitter 13 is condensed on the second light receiving element 17 by the condenser lens 16.

Since the magnitude of the intensity of the polarized light component changes depending on the direction of the magnetic field in the area where the spot is located on the optical tape, the reproduced signal from the optical tape is transmitted to each light receiving element 1.
5 and 17 are obtained by subtracting the outputs of the subtracters 18. Each signal of a track error and a focus error is detected using the output of at least one of the light receiving elements, and the servo lens is driven by an actuator (not shown) to eliminate these errors. In order to detect an error signal, it is necessary to divide the light receiving area of the light receiving element into a plurality of light receiving areas, which are generally known as a technique of a magneto-optical disk apparatus, and thus will not be described in detail here.

FIG. 3 is an explanatory diagram showing the optical system of the embodiment in more detail, and its specific numerical configuration is shown in the following table. The surface numbers in the table are given from the semiconductor laser 1 side, the symbol r is the radius of curvature, d is the lens thickness or air gap, nd is the refractive index at d-line (588 nm), ν is the Abbe number, n780 is a refractive index at a wavelength of 780 nm.

Table 1 shows the configuration of the collimator lens.
The collimating lens is a parallel flat plate that is a cover glass
(Surface numbers 1 and 2) and six lenses. Second
The lens and the third lens are bonded together. Symbol d0
Indicates the distance from the semiconductor laser to the cover glass.

[0026]

[Table 1]

Table 2 shows the beam shaping prism 20 (first to first).
4 shows the configuration of the first beam splitter 3 (the fifth and sixth surfaces). Both the incident and exit end faces are flat.
Symbol d0 is the distance between the last surface of Table 1 and the first surface of Table 2.
(The same applies hereinafter). In addition, the thickness d of the prism indicates a length through which a light beam passing through the optical axis of the collimator lens passes, and the beam splitter 3 does not describe a separation surface.

[0028]

[Table 2]

Table 3 shows that the condenser lens 4 (the first to eleventh surfaces), the lens 5 (the twelfth and thirteenth surfaces), and the servo lens 6 (the fourteenth to second surfaces).
2) is shown. The lens 5 is a sphere,
Thirteen surfaces have a shape of one spherical surface.

[0030]

[Table 3]

Table 4 shows the configuration of the relay lenses 7 and 8. The relay lenses 7 and 8 are configured by arranging the same laminated lens in opposite directions.

[0032]

[Table 4]

Table 5 shows the configuration of the deflecting prism 9. The second surface and the third surface are reflecting surfaces, and the light rays on the optical axis reach the reflecting surface 3.5 mm after entering the prism 9.

[0034]

[Table 5]

Table 6 shows the structure of the objective lens 10.

[0036]

[Table 6]

In the above configuration, the position of the lens 5 shown in Table 3 is when the magnification of the lens 5 is +1 times, and the magnification is +4 by moving the lens 5 by +0.142 mm in the optical axis direction. %, And moving by -0.154 mm changes the magnification by -4%. At this time, the deviation of the back focus of the entire system is -0.003 mm.

Although the above embodiment has been described with respect to an example in which the present invention is applied to an optical tape system, any system employing a multi-beam system can be similarly applied to a conventional optical disk system. .

Further, in the above embodiment, the example in which the magnification changing lens 5 is constituted by a single lens has been described. It is clear that the system can be constructed.

[0040]

As described above, according to the present invention, in the optical information recording / reproducing apparatus adopting the multi-beam system, the spot interval is adjusted by changing the magnification of the optical system without tilting the beam train. It is also possible to minimize the out-of-focus at that time. Therefore, it is possible to easily adjust the spot interval with good responsiveness and to provide a configuration suitable for an apparatus using a tape-shaped recording medium.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an optical system schematically illustrating an optical tape system according to an embodiment.

FIG. 2 is an explanatory diagram showing a relationship between a locus of a spot and a tape.

FIG. 3 is an explanatory diagram showing a specific configuration of an optical system of the optical tape system according to the embodiment.

FIG. 4 is an explanatory diagram showing a relationship between a track of a spot and a tape when a spot row is inclined.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser 2 ... Collimating lens 5 ... Lens which changes imaging magnification 10 ... Objective lens

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-54-74705 (JP, A) JP-A-1-204230 (JP, A) JP-A-2-241018 (JP, A) JP-A 5- 101422 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G11B ^7/ 12-7/22

Claims (2)

(57) [Claims] 1. A light source unit for generating a plurality of light beams, and an objective lens for forming an image of the light beams from the light source unit as a plurality of spots on a recording medium, and formed by a plurality of beams.
Multiple spots can be operated on different tracks.
In a multi-beam optical recording / reproducing device, it can be moved on the optical axis between the light source unit and the objective lens.
At the time of moving back and forth in the optical axis direction.
The imaging magnification changes around + 1x including + 1x
In addition, a lens whose imaging magnification is changed by the movement
An optical recording / reproducing apparatus comprising: 2. A deflecting member for deflecting a plurality of light beams incident from the light source unit side out of the incident direction and entering the objective lens between the lens for changing the imaging magnification and the objective lens. 2. The optical recording / reproducing apparatus according to claim 1, wherein the deflecting member and the objective lens are provided in a rotary head rotatably provided around the direction of the incident light beam. .