JP2605629B2 - Focus offset adjustment method and 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 focus offset adjusting method and apparatus for a read-only or recording / reproducing erasable optical head mounted on an optical disk apparatus, and easily adjusts the focus offset without disassembling the apparatus. The present invention relates to a method and an apparatus for adjusting a focus offset.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIGS.

FIG. 4 illustrates a focus offset adjusting mechanism of a magneto-optical head as an example. The light beam emitted from the semiconductor laser 40 passes through a collimator lens, passes through a composite prism composed of beam splitters 43 and 42, and reaches an objective lens actuator.

The beam emitted from the objective lens 41 is reflected by the optical disk, and a magneto-optical signal is detected by the beam deflected by 90 degrees by the beam splitter 42 of the compound prism. The servo error is detected through the beam.

For detecting a focus error, the beam condensed by the convex lens 44 is split by a beam splitter 45 into a beam going straight and a beam deflected by 90 degrees. The beam split by 90 degrees goes straight through the lens 46 and the cylindrical lens 47 and reaches the four-division optical sensor 48, where a so-called astigmatic focus error detection is performed.

The focus offset can be adjusted by electrically adjusting the offset or by optically adjusting an optical component having a power, such as a convex lens or a concave lens, which constitutes the optical head, in the optical axis direction.

In the former case, the electric servo drive is unstable with respect to a temperature change of an electric component such as a resistance volume. Furthermore, in order to obtain a sufficient carrier-to-noise ratio (CNR), which is the most important for the basic recording / reproducing characteristics, the adjustment range by the semi-fixed resistor for focus offset adjustment is biased, and optimization adjustment cannot be performed. There is.

Therefore, it is necessary to perform the latter optical adjustment so that the electrical focus offset becomes neutral.

The optical focus offset is adjusted by moving the optical block of the concave lens 46 and the cylindrical lens 47 in the optical axis direction. At this time, the eccentric pin 51 is used, and the combination block 49 is provided with the adjustment groove 50 to convert the rotational motion by the linear motion in the optical axis direction.

FIGS. 5 and 6 show CNR and bit error rate (BER) related to performance when a focus offset is used as a parameter, and are diagrams for explaining the importance of focus offset adjustment.

FIG. 5 shows CNR frequency characteristics when a focus offset is used as a parameter. One example is (1,
7) The maximum repetition frequency of 80 Mbps in code modulation is 30 MHz. CNR at this frequency is 4
Whether or not 2 dB can be obtained is a major turning point in the digital recording system.

The CNR frequency characteristic 52 when the focus offset is sufficiently adjusted is indicated by a solid line, and the CNR frequency characteristic 5 when the focus offset deviates from the best point.
3 is indicated by a broken line. As shown in the figure, it is necessary to sufficiently adjust the focus offset to improve the CNR at the highest repetition frequency.

FIG. 6 shows CN with respect to focus offset.
R and bit error rate (BER) characteristics are shown. The focus depth is determined by the objective lens numerical aperture (NA) and the wavelength (λ). When NA = 0.55 and λ = 0.68 μm,
Depth of focus = 1.1 μm. For this depth of focus,
If the focus offset deviates by more than ± 0.5μm, CN
R and the bit error rate deteriorate.

Erasing such an optical head compatible with high density
In a device in which recording / reproducing and three are set as one set and arranged above and below the disk, a total of six optical heads are incorporated in one disk device, and the focus offset adjustment becomes more complicated. Become.

As described above, in order to perform the best recording and obtain the best reproduction signal, it is important to adjust the focus offset with the optical head mounted for each disk device mounted on the disk device. However, if a plurality of optical heads are arranged above and below the disk of the optical disk device, it is difficult to adjust each optical head.

[0016]

The importance of the focus offset adjustment for optimizing the recording / reproducing characteristics has been described with reference to FIGS. Further, it is difficult to adjust the optical head in a state where a plurality of optical heads are installed above and below the disk and in a state where the signal of the disk is reproduced.

Conventionally, the focus offset is adjusted by adjusting the optical sensor with an eccentric pin. However, the adjustment of the optical sensor is on the order of 1 μm, and the adjustment itself is difficult, and the adjustment of the focus optical sensor is performed. The adjustment is performed from the tangential direction of the optical disk, and it is impossible to adjust over the entire area from the inner circumference to the outer circumference of the optical disk due to the arrangement of the eccentric pins.

For this purpose, it is necessary to temporarily remove the optical head from the apparatus and adjust the focus offset with another jig.

Therefore, an object of the present invention is to solve the above-mentioned problem by adjusting the optical focus offset of the optical head from the outside of the apparatus in a state where a plurality of optical heads are mounted on the apparatus, and achieving the best recording. The purpose is to obtain reproduction characteristics.

[0020]

SUMMARY OF THE INVENTION A focus offset adjusting method according to the present invention adjusts an optical focus offset of an optical disk recorder for moving an optical head on the inner and outer circumferences of a disk via a linear motor. An error detecting system is provided with an optical portion having power, a groove portion orthogonal to the optical axis is provided in the error portion, and an eccentric pin is brought into contact with a tip portion of the groove portion so as to be movable in the optical axis direction. Attaches a long rod extending in the radial direction of the disk, makes it movable in the direction of the optical axis, and furthermore, this eccentric pin connects the optical part having the power of the optical head, which is disposed directly inside the apparatus from outside the apparatus, to the light of the optical head. It is characterized in that it can be adjusted in the axial direction.

The focus offset adjusting apparatus of the present invention adjusts the optical focus offset of an optical disk recorder that moves an optical head on the inner and outer circumferences of a disk via a linear motor, and supplies power to a focus error detection system of the optical head. An optical part is provided, and a groove part orthogonal to the optical axis is provided in the optical part, and an eccentric pin is brought into contact with a tip part of the groove so as to be movable in the optical axis direction. An elongate rod extending in the radial direction is attached and configured to be movable in the direction of the optical axis, and the eccentric pin is used to connect the optical part having the power of the optical head directly disposed inside the apparatus from outside the apparatus to the optical head. The optical axis is adjustable in the optical axis direction.

[0022]

The focus offset adjusting method and apparatus according to the present invention can be realized by moving the focus optical sensor or moving the lens having power in the optical axis direction.

Generally, the adjustment accuracy of the optical sensor is on the order of μm, and it is very difficult to perform the adjustment with the optical head mounted on the optical disk device. Therefore, if the optical head is configured to adjust the latter combined block of the concave lens and the cylindrical lens having the power by moving in the optical axis direction, the adjustment accuracy will be on the order of 10 μm, and the adjustment will be easy.

Further, an optical head is designed so that this optical axis direction is tangential to the optical disk, a hole is formed on a line extending from the center of the optical disk outside the optical disk device, and a combination block of a concave lens and a cylindrical lens is adjusted through an eccentric pin. I do.

At the time of this adjustment, an eccentric pin is applied to the focus offset adjusting hole of the optical head mounted on the linear motor, and the movement of the optical head is fixed by a lock plate described later.

[0026]

FIG. 1 shows a recording method according to the present invention, ie, a constant recording wavelength constant angular velocity rotation method (Constant Wave Length-Constant).
FIG. 1 shows a principle diagram of an optical disk device based on Angular Velocity (CWL-CAV).

FIG. 2 shows the appearance of the optical disk apparatus according to the present invention, and shows the operation of inserting an eccentric pin for adjusting a focus offset. FIG. 3 shows the operation when the movement of the linear motor is locked and the focus offset is adjusted, and the operation when the locked state is released.

Referring to FIG. 1, optical heads are arranged above and below an optical disk 3, and when the lower optical head 1 moves from the inner circumference to the outer circumference of the optical disk, the upper optical head 2 is synchronized from the outer circumference of the optical disk with the inner optical head. It is configured to move to the circumference and to add the two recording rates to a constant recording rate.

For example, the current television system N
Although the uncompressed digital NTSC composite signal in the TSC system is 123 Mbps, the upper optical head 2
Is 80 Mbps at the outermost periphery of the disk, the lower optical head 1 is located at the innermost periphery of the disk, and the recording rate is 43 Mbps.
ps. The sum of both recording rates is always 123 Mbp
This is a method in which s is constant.

FIG. 2 shows an optical head arranged above and below a disk.
The operation of adjusting the focus offset from outside the disk device will be described. When a plurality of optical heads are arranged in this manner, the state of adjusting the optical focus offset is shown by taking out a single optical head, and locking and unlocking the movement of the inner and outer circumferences of the optical head. FIG.
(A) and FIG. 3 (b).

Referring to FIG. 2, three optical heads are arranged above and below the optical disk, respectively, and erase heads 21, 22, recording heads 23, 24, reproducing head 25,
26 heads.

The arrangement of these optical heads is divided into three equal parts, and the innermost and outermost positions of the optical head are indicated by rectangular marks with circles representing lenses.

When the lower heads 21, 23, 25 start from the innermost circumference, the upper optical heads 22, 24, 26
Starts from the outermost circumference toward the inner circumference. These 6
For each of the optical heads, a hole for adjusting a focus offset is provided outside the disk device. Optical head 21,
Adjustment holes 210 for 22, 23, 24, 25, 26
220, 230, 240, 33, and 260 are provided.

Adjustment rods 211, 221, 231, 241, 32, 26 with eccentric pins attached to the ends through these adjustment holes
Step 1 adjusts the focus offset of the optical head while monitoring the signal output.

The optical head 25 will be described as an example with reference to FIG. In the adjustment hole 31 of the optical head, a long adjustment rod 32 having an eccentric pin attached to the tip is disposed through adjustment guides 33 and 34 provided in the optical disk recorder. At this time, the drive coil 35 constituting the linear motor
The optical head 25 is fixed by pressing the carriage 36 attached to the optical head 25 with a long beam plate 37.

The beam plate 37 also serves to fix and protect the optical head when transporting and moving the optical disk device.

FIG. 3A shows a state in which the optical head has stopped moving in the disk radial direction (locked state).
(B) shows a state where the lock of the optical head is released (unlocked state).

Since the adjustment rod 32 extends in the radial direction of the disk, the focus offset can be easily adjusted even if the adjustment rod 32 is located at the inner or outer circumference of the optical disk and in the signal reproducing state.

[0039]

According to the present invention, the focus offset can be easily adjusted regardless of whether the optical head is located at the inner or outer circumference of the optical disc and in the signal reproducing state. Therefore, recording and reproduction with good CNR frequency characteristics can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of an optical disk device using CWL-CAV according to the present invention.

FIG. 2 is an external view of an optical disk device according to the present invention.

FIGS. 3A and 3B are perspective views respectively showing a locked state and an unlocked state of focus offset adjustment in one embodiment of the present invention.

FIG. 4 is a schematic view illustrating a focus offset adjustment mechanism of the magneto-optical head.

FIG. 5 is a diagram showing CNR frequency characteristics when a focus offset is used as a parameter.

FIG. 6 is a diagram showing CNR and bit error rate (BER) characteristics with respect to a focus offset.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical head under optical disk 25 Optical head 31 Adjustment hole 32 Adjustment rod 33, 34 Adjustment guide 35 Coil 36 Carriage 37 Beam plate 43 Beam splitter 44 Convex lens 45 Beam splitter 46 Concave lens 47 Cylindrical lens 48 Quadrant sensor 50 Adjustment groove 51 Eccentric pin 52 CNR frequency characteristics

Claims (4)

(57) [Claims] An optical part having a power is provided in a focus error detection system of an optical head for adjusting an optical focus offset of an optical disk recorder for moving an optical head on the inner and outer circumferences of a disk via a linear motor. A groove portion orthogonal to the optical axis is provided, and an eccentric pin is brought into contact with the tip portion in this groove to enable movement in the optical axis direction.This eccentric pin is attached with a long rod extending in the disk radial direction, The focus is characterized in that the eccentric pin is movable in the direction of the optical axis, and that the eccentric pin is capable of adjusting the optical part having the power of the optical head disposed directly in the apparatus from outside the apparatus in the direction of the optical axis of the optical head. Offset adjustment method. 2. A method for adjusting an optical focus offset of an optical disk recorder for moving an optical head on the inner and outer circumferences of a disk via a linear motor, wherein an optical part having power is provided in a focus error detection system of the optical head. A groove portion orthogonal to the optical axis is provided, and an eccentric pin is brought into contact with a tip portion of the groove so as to be movable in the optical axis direction. The eccentric pin is elongated in the disk radial direction. A rod is attached and configured to be movable in the direction of the optical axis. Further, this eccentric pin can adjust the optical part having the power of the optical head disposed inside the apparatus directly from the outside of the apparatus in the direction of the optical axis of the optical head. A focus offset adjusting device, characterized in that: 3. An adjusting rod having an eccentric pin attached to the distal end portion thereof, wherein an adjusting rod insertion guide is provided inside the apparatus, wherein the adjusting rod has an eccentric pin attached thereto. 2. The focus offset adjusting method according to 1. 4. An adjusting rod having an eccentric pin attached to the distal end portion of the apparatus, wherein an adjusting rod insertion guide is provided in the apparatus, and the adjusting rod is provided with an eccentric pin. 3. The focus offset adjusting device according to 2.