JPH0696467A - Optical recording and reproducing device - Google Patents

Abstract

(57) [Abstract] [Objective] In a multi-beam type optical recording / reproducing apparatus, it has a mechanism capable of adjusting the interval between a plurality of spots formed on a recording medium with a simple configuration and with good responsiveness. The purpose is to provide a device. In an optical information recording / reproducing apparatus for forming light beams from a semiconductor laser 1 that generate a plurality of light beams as a plurality of spots on an optical tape 11 by an objective lens 10, between the semiconductor laser 1 and the objective lens 10. In addition, a lens 5 for changing the imaging magnification by moving in the optical axis direction is provided, and the lens 5 is movable so as to change the magnification within a range including -1.

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,
The present invention relates to an optical recording / reproducing apparatus capable of forming a plurality of spots on a recording medium and simultaneously performing recording / reproducing on a plurality of tracks.

[0002]

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

In a multi-beam type optical recording / reproducing system, due to a focal length error of a lens, a variation in a light emitting point interval of a multi-point light emitting semiconductor laser used as a light source, and the like,
There is a possibility that the distance between the focused 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 spots picks up a signal from a position displaced from the track, there is a problem that the error rate of the reproduction signal using the reflected light from this spot increases.

Conventionally, in order to match each spot with the corresponding track, the image rotator provided between the light source and the objective lens is rotationally adjusted so that the spot train on the recording medium is moved in the track direction. There is known a method of aligning each spot with each track without tilting them and changing the spot interval.

[0006]

However, in the above-described conventional adjusting method, the spots other than the rotation center move not only in the track width direction but also in the direction along the track. There is a problem in that the information to be recorded / reproduced between the spots and other spots is temporally displaced.

In particular, a VTR is applied to a tape-shaped recording medium.
In an optical recording / reproducing apparatus using a head that rotates across the width direction of the tape as described above, when the spot row is tilted, the spot width changes within the tape width as shown in FIG. Could not make adjustments.

In addition to the method of tilting the spot row as described above, as means for changing the spot interval itself, first, there is a method of tilting the beam shaping prism to change the zoom ratio, and secondly, for a photographic lens. A method of varying the magnification by controlling the position of each of the zoom lens group and the image position change correction lens group, such as the zoom lens used, can be considered.

However, in the first method, it is necessary to reversely rotate the two prisms around the optical axis in order to keep the exit angle constant and to keep the direction of the spot row unchanged. Although this method is theoretically possible, it has a problem in responsiveness and is unsuitable as a means used for correcting a tracking error in an actual operating environment.

Also in the case of the second method, the structure is complicated because the positions of the two lens groups are respectively controlled, and the 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, a plurality of spots formed on a recording medium have a simple structure, and An object of the present invention is to provide a device having a mechanism that can be adjusted with good responsiveness.

[0012]

In order to achieve the above-mentioned object, an optical recording / reproducing apparatus according to the present invention has a light source section for generating a plurality of light fluxes and a plurality of light fluxes from the light source section on a recording medium. And an objective lens for forming an image, and a lens provided between the light source unit and the objective lens for changing the image forming magnification by moving in the optical axis direction. It is characterized in that it is movable so as to change the magnification within a range including -1.

[0013]

Embodiments of the present invention will be described below. Figure 1
[Fig. 3] shows an outline of an 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 by heat and magnetic field of light and reflects the same as in a generally used magneto-optical disk apparatus. The recorded information is reproduced by using the magnetic Kerr effect of time.

A plurality of beams emitted from the multipoint emission semiconductor laser 1 are made into parallel light beams by a collimator lens 2, and each beam has a circular cross section through a beam shaping optical system 20 composed of two prisms. Is corrected to. The shaped light flux 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 flux converged by the condenser lens 4 diverges, and is movable so as to change the magnification within a range including -1. The light beam that has passed through the lens 5 is made 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 the optical axis direction and a direction orthogonal to the optical axis for focusing and tracking.

The optical elements from the semiconductor laser 1 to the relay lens 8 are provided in the fixed portion 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 the prism 9 as a deflecting member provided in the rotary head B, and the second light beam is reflected.
By the reflecting surface 9b, it is reflected again in a direction parallel to the incident light beam. The rotary head B has its optical axis Ax with respect to the fixed portion A.
Rotate around. R is the radius of gyration.

The reflected light beam from the prism 9 enters the objective lens 10 and forms a plurality of spots on the optical tape 11, which is a recording medium, which are separated in the longitudinal direction of the tape. Therefore, it is possible to record / reproduce on a plurality of tracks with one rotation.

The spot on the optical tape 11 moves as shown in FIG. 2 by the rotation of the head. In order to adjust the spot interval, the lens 5 is moved in the optical axis direction to change the magnification of the optical system. As a result, the spot interval can be changed without changing the direction of the spot row.

The reflected light beam from the optical tape 11 becomes a parallel light beam through the objective lens 10 again, and the relay lens 8,
It is incident on the first beam splitter 3 via 7, the servo lens 6, the lens 5, and the condenser lens 4. The light flux reflected by the first beam splitter 3 is transmitted to the half-wave plate 12
The polarization direction is rotated by 45 degrees by and is separated into both P and S polarization components by the polarization beam splitter 13.

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

Since the magnitude of the intensity of the polarized component changes depending on the direction of the magnetic field in the area where the spot is located on the optical tape, the reproduction signal from the optical tape is received by each light receiving element 1.
It is obtained by subtracting the outputs of 5, 17 by the subtracter 18. Further, each signal of the track error and the focus error is detected by using the output of at least one of the light receiving elements, and the servo lens is driven by an actuator (not shown) so as to eliminate these errors. In order to detect the error signal, it is necessary to divide the light receiving area of the light receiving element into a plurality of areas. However, since these are generally known as the technology of the magneto-optical disk device, detailed description thereof will be omitted 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 table below. 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 the air gap, nd is the refractive index at d-line (588 nm), ν is the Abbe number, n780 is the refractive index at a wavelength of 780 nm.

Table 1 shows the structure of the collimating lens.
The collimating lens is a parallel flat plate that is a cover glass.
In addition to (surface numbers 1 and 2), it consists of 6 lenses. Second
The lens and the third lens are attached to each other.

[0026]

[Table 1]

Table 2 shows the beam shaping prism 20 (first to first).
4) and the first beam splitter 3 (5th and 6th surfaces) are shown. Both the entrance and exit faces are flat.
The symbol d0 is the distance between the last surface of Table 1 and the first surface of Table 2.
(Same below). Further, the thickness d of the prism indicates the length through which the light ray passing through the optical axis of the collimator lens passes, and the beam splitter 3 does not describe the separation surface.

[0028]

[Table 2]

Table 3 shows a condenser lens 4 (first to eleventh surfaces), a lens 5 (twelfth and thirteenth surfaces), and a servo lens 6 (fourteenth to second surfaces).
2) The structure is shown.

[0030]

[Table 3]

The lens 5 is a lens having aspherical surfaces on both sides. The aspherical surface is defined by the distance X from the tangent plane of the aspherical vertex of the coordinate point on the aspherical surface whose height from the optical axis is Y, the curvature (1 / r) of the aspherical vertex C, and the conic coefficient K. , 4th-order and 6th-order aspherical coefficients are A4 and A6, respectively. The radius of curvature of the aspherical surface in Table 3 is the radius of curvature of the aspherical vertex, and the conical coefficient and the aspherical surface coefficient of these surfaces are shown in Table 4.

[0032]

[Equation 1] X = CY ² / (1 + √ (1- (1 + K) C ² Y ² )) + A4Y ⁴ + A6Y ⁶

[0033]

[Table 4]

Table 5 shows the construction of the relay lenses 7 and 8. The relay lenses 7 and 8 are configured by arranging the same cemented lens in mutually opposite directions.

[0035]

[Table 5]

Table 6 shows the structure of the deflecting prism 9. The second surface and the third surface are reflecting surfaces, and the light ray on the optical axis reaches the reflecting surface at 3.5 mm after entering the prism 9.

[0037]

[Table 6]

Table 7 shows the structure of the objective lens 10.

[0039]

[Table 7]

In the above structure, the magnification is +10 when the lens 5 is moved by -0.227 mm in the direction of the optical axis.
%, And by moving +0.270 mm, the magnification changes by -10%. The back focus shifts at that time are 0.011 mm and 0.012 mm, respectively, which are sufficiently small values with respect to the focusable area of the servo lens 6, and the focus deviated due to the change in magnification can be easily adjusted.

FIG. 4 shows an example in which the lens 5 is a negative lens. Table 8 is a specific example of the numerical configuration. Here, for simplicity, the relay lens is omitted, and the collimator lens 2, the condenser lens 4, the servo lens 6, and the objective lens 10 are shown as one lens each.

In this example, the second, third, fifth, sixth, eighth and ninth surfaces are aspherical surfaces. Table 9 shows the conical coefficient and the aspherical surface coefficient of these aspherical surfaces.

[0043]

[Table 8]

[0044]

[Table 9]

In this case, the lens 5 is moved by +0.1 in the optical axis direction.
Magnification changes + 4% by moving 01 mm,
By moving 0.110 mm, the magnification changes by -4%. Any back focus deviation at this time is -0.
It is 004 mm.

In the above embodiment, only the example in which the present invention is applied to the optical tape system is described. However, if the system adopts the multi-beam method, it can be similarly applied to the conventional optical disk system. it can.

[0047]

As described above, according to the present invention, in the optical information recording / reproducing apparatus adopting the multi-beam method, the spot interval is adjusted by changing the magnification of the optical system without tilting the beam train. In addition, it is possible to suppress the focus deviation at that time. Therefore, it is possible to adjust the spot distance with a simple structure and good responsiveness, and it is possible to provide a structure suitable for an apparatus using a tape-shaped recording medium.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an optical system showing an outline of an optical tape system of an example.

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

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

FIG. 4 is an explanatory diagram of an optical system showing a configuration when the lens 5 is a negative lens.

FIG. 5 is an explanatory diagram showing a relationship between a locus of spots and a tape when a spot row is tilted.

Claims (2)

[Claims] 1. A light source section for generating a plurality of light fluxes, an objective lens for focusing the light fluxes from the light source section on a recording medium as a plurality of spots, and a light source section provided between the light source section and the objective lens. A lens for changing the imaging magnification by moving in the optical axis direction, wherein the lens whose imaging magnification is changed is movable so as to change the magnification within a range including -1 times. Characteristic optical recording / reproducing device. 2. A deflection member for deflecting a plurality of light beams incident from the light source unit side to the outside of the incident direction and for 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 that is rotatable about the direction of the incident light beam. .