JPH01204233A - Optical head - Google Patents

Abstract

PURPOSE:To keep a beam profile, which is image-formed on a disk in the circumferential direction, constant at the time of reproducing and recording by providing a triaxial driving actuator, a dividing mirror which reflects one part of a laser beam before projecting to an objective lens, and a servo means driving the objective lens in circumferential direction of the disk. CONSTITUTION:The triaxial driving actuator is obtained and a dividing mirror 18, which reflects one part of the laser beam before projecting to an objective lens 5, is provided so as to move in the disk circumference direction in one body with the objective lens 5. Dividing photo-detecting parts 19a and 19b are provided to receive the reflected light of the dividing mirror 18 and to detect the dislocation of the laser beam in the disk circumference direction and a servo means 21 is provided to drive the objective lens 5 in the disk circumference direction in correspondence to a detecting signal by the dividing photo- detecting parts 19a and 19b. The relative positions of the beam intensity center of the laser beam before projecting to the objective lens 5 and the center of the objective lens in the disk circumference direction are always kept to constant. Thus, the beam profile to be image-formed on the disk is kept always constant in the disk circumference direction.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical head used in optical disk recording/reproducing devices and the like.

2. Description of the Related Art A conventional optical disk recording and reproducing apparatus, as shown in FIG. 3, includes a disk motor 2 for rotating a disk 1;
An optical head 3 for recording and reproducing information on the disk 1, and a transfer unit (for example, a linear motor, etc.) 4 for moving the gutter 3 optically in the radial direction of the disk 1.
have.

As shown in FIG. 4, the optical head 3 includes an objective lens 5, a laser 6 as a light source, a collimator lens 7, a polarizing prism 8, a quarter-wave plate 9, and an objective lens 5 in a focusing direction. and a moving coil type actuator 10, a prism 11, a detection lens 12, a focus detector 13, a detector 14 for both tracking error signal and reproduction signal, etc., which constitute a magnetic circuit driven in the tracking direction. ing.

In the apparatus configured as described above, the transfer unit 4 is driven to perform a rough search for the target address on the disk, and the objective lens 5 in the optical head 3 is finely moved by the actuator 10 to reach the target address. .

In FIG. 4, a laser beam from a laser 6, which is a light source, is converted into parallel light by a collimator laser 7, changed its optical path upward by a polarizing prism 8, passes through a 1/1 wavelength plate 9, and is then passed through an objective lens 5. An image is formed on the disk 1.

At this time, the focus sync drive and tracking drive are performed by slightly moving the objective lens 5 using the actuator 10.

The reflected light from the disk 1 passes through the objective lens 5 and again through the quarter-wave plate 9, and then passes through the polarizing prism 8.
When light is incident on it, it is transmitted. A part of this transmitted light is
The light is reflected by the prism 11 and guided to the focus detector 13 via the detection lens 12.

The other light passes through the prism 11 and is guided in the far field to a detector 14 that also serves as a tracking error signal and reproduction signal.

Problems to be Solved by the Invention However, with such a configuration, the beam profile in the circumferential direction on the disk may differ between playback and recording, which deteriorates the recording and playback signal quality. There was a problem.

The above problem arises for the following reasons. That is, in the conventional example described above, the objective lens 5 has a structure that does not move in the disk circumferential direction, so the optical axis center of the parallel laser beam before entering the objective lens 5 and the center of the objective lens 5 in the disk circumferential direction Although the relative position with respect to the laser beam is fixed and does not change, there are some lasers in which the center of the emitted beam intensity differs between reproduction (low power) and recording (high power). For this reason, for example, even if the beam intensity center of the parallel laser beam before entering the objective lens during playback is adjusted to the center of the objective lens 5 in the disk circumferential direction, the beam intensity center will shift during recording. It may shift in the disk circumferential direction with respect to the upper middle of the objective lens 5. Conversely, if the beam intensity center during recording is adjusted to the center of the objective lens, it may shift during playback. In this way, the relative position between the center of the beam intensity of the parallel laser beam before entering the objective lens and the center of the objective lens in the circumferential direction of the disk will be shifted either during recording or during playback. However, the beam profile formed on the disk in the circumferential direction of the disk is different, which deteriorates the recording and reproduction signal quality.

It should be noted that an optical head equipped with a mechanism for moving and adjusting the objective lens 5 also in the circumferential direction of the disk is conventionally known.
For example, JP-A-56-98720, JP-A-58-
No. 64648, Japanese Unexamined Patent Publication No. 151848/1983,
It is disclosed in Japanese Patent Application Laid-Open No. 61-250848. However, the methods disclosed in these publications all indicate whether the beam spot precedes or follows the information pits on the disk.
This is a so-called deviation correction with respect to the time axis, but it does not prevent a deviation in the relative position between the beam intensity center of the parallel laser beam before entering the objective lens and the objective lens center in the disk circumferential direction.

The present invention has been made in view of the above-mentioned problems, and the beam profile in the circumferential direction that is imaged on the disk does not change between reproduction and recording, and high-quality recording and reproduction signals can be obtained. The objective is to provide an optical head that can obtain the following.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention uses a three-axis drive actuator that can drive in the focus direction, tracking direction, and disk circumferential direction as the actuator for adjusting the position of the objective lens, and the objective lens A split mirror that reflects a part of the laser beam before it enters the laser beam is provided so as to move integrally with the objective lens at least in the circumferential direction of the disk, and receives the reflected light of the split mirror to reflect the laser beam on the disk circle. A divided light-receiving section is provided for detecting deviation in the circumferential direction, and a servo means is further provided for driving the objective lens in the circumferential direction of the disk in accordance with a detection signal from the divided light-receiving section.

Effect of the Invention With the above-described configuration, the split mirror reflects a part of the laser beam before it enters the objective lens and makes it enter the split light receiving section, and the split light receiving section adjusts the deviation of the center of the beam intensity from the incident light with respect to the objective lens. , and the servo means drives and controls the objective lens in the disk circumferential direction so that the deviation becomes 0. Therefore, the beam intensity center of the laser beam before entering the objective lens and the objective lens center in the disk circumferential direction are The relative position can always be kept constant. Therefore, the beam profile in the disk circumferential direction that is imaged on the disk is always constant, making it possible to obtain high-quality recording and reproduction signals.

Embodiment FIG. 1 is a side view showing a schematic configuration of an optical head according to an embodiment of the present invention, and FIG.
It is a side view seen from a direction different by 0 degrees. In addition, Figure 3,
Components that are the same as those in the conventional example shown in FIG. 4 are designated by the same reference numerals.

In FIG. 1, 1 is an optical disc, 2 is a disc motor for rotating the optical disc, 3 is an optical head for recording and reproducing information on the disc l, and 4 is for transporting the optical head 3 in the radial direction of the disc 1. A transfer unit (for example, a linear motor, etc.) is used to

The optical head 3 includes an objective lens 5, a laser 6 as a light source, a collimator lens 7 that converts the light emitted from the laser 6 into parallel light, a polarizing prism 8, a quarter-wave plate 9, a prism 11. It has a detection lens 12, a focus detector 13, and the like. These configurations are the same as before.

A reproduction signal dedicated detector 15 is provided below the prism 11 at a position that receives the reflected light transmitted through the prism 11. The objective lens 5 is held by a movable body 16 that can move in the focus direction, the tracking direction, and the circumferential direction of the disk. For example, a moving coil type actuator 17 is provided, which constitutes a magnetic circuit that drives in the direction.

In FIG. 2, the movable body 16 reflects a part of the laser beam before it enters the objective lens 5 and transmits the remaining part.
In addition, there is a split mirror 18 that reflects a part of the reflected light from the disk that has passed through the objective lens 5 and transmits the remaining part, and two split mirrors that receive part of the beam that is reflected by the split mirror 18 before entering the objective lens. A detector 19 having a divided light receiving section consisting of light receiving sections 19a and 19b, and a tracking error signal detector I that receives part of the light reflected from the disk reflected by the split mirror 18 are attached, and are integrated with the objective lens 5. It is supposed to move to . Here, the detector 19
The two light receiving sections 19a and 19b can detect the deviation of the center of the laser beam before it enters the objective lens 5 in the disc circumferential direction with respect to the center of the objective lens 5 from the difference in the amount of light incident on the two. For example, in the case of FIG. 2, they are arranged one above the other. Actuator 17
A servo circuit 21 is connected to the servo circuit 21, and the servo circuit 21 controls the actuator 17 to move the movable body 16 in the disk circumferential direction so that the difference between the output signals of the two light receiving sections 19a and 19b becomes 0. It is something to control. Although not shown, a servo circuit in the focusing direction and a servo circuit in the tracking direction that control the actuator 17 are also provided.

The operation of the optical head configured as above will be described below.

The laser beam converted into parallel light by the collimator lens 7 is reflected by the polarizing prism 8, passes through the quarter-wave plate 9, and reaches the splitting mirror 18. A portion of the parallel laser beam is reflected by the splitting mirror 18 and received by the light receiving sections 19a and 19b of the detector 19.

At this time, if the intensity center of the laser beam is shifted from the center of the objective lens 5 in the disk circumferential direction, a difference will occur in the amount of light received by the two light receiving sections 19a and 19b.

The difference signal between the light receiving sections 19a and 19b is sent to the servo circuit 21, and the servo circuit 21 drives the actuator 17 so that the difference signal becomes O, thereby moving the movable body 16 in the circumferential direction of the disk. As a result, even if the beam intensity center of the parallel laser beam before entering the objective lens deviates from the center of the objective lens, for example during playback and recording, the movable body 16 can be moved in the disk circumferential direction. The relative position between the beam intensity center of the collimated laser beam before entering the objective lens and the objective lens center is always kept constant.

Next, the remaining parallel laser light that is transmitted without being reflected by the splitting mirror 18 forms an image on the disk 1 via the objective lens 5, and performs recording or reproduction. The reflected light from the disk 1 passes through the objective lens 5 and enters the splitting mirror 18. A part of the reflected light from the disk 1 is reflected by the split mirror 18 and reaches the tracking error signal detector. Tracking control is performed based on the difference signal added to the tracking error signal detector. The remaining reflected light from the disk 1 that is transmitted without being reflected by the splitting mirror 18 passes through the quarter-wave plate 9, the polarizing prism 8, and the prism 11 and the detection lens 12.
which goes to the focus error signal detector 13 via
The reproduced signal is separated into the one that goes to the dedicated detector 15 and the one that goes to the reproduced signal dedicated detector 15.

In the above embodiment, the split mirror 18 is connected to the objective lens 5.
Although the divided mirror 18 is held by a movable body 16 that can be moved integrally with the objective lens 5 in three axes directions: the focus direction, the tracking direction, and the circumferential direction of the disk, the divided mirror 18 does not necessarily have to be moved in the three axes directions; Any structure that moves integrally in the circumferential direction of the disk may be used. Further, by using the detector 14 for both tracking error signal and reproduction signal in place of the reproduction signal-only detector 15, it is also possible to omit the addition of a tracking error signal detector.

Effects of the Invention As is clear from the above description, the present invention provides an actuator that adjusts the position of an objective lens in the focus direction,
3 that can be driven in the tracking direction and the disk circumferential direction
A split mirror that is a shaft-driven actuator and that reflects a part of the laser beam before it enters the objective lens is provided so as to move integrally with the objective lens at least in the circumferential direction of the disk, and receives reflected light from the split mirror. By providing a divided light receiving section for detecting the deviation of the laser beam in the disk circumferential direction, and further providing a servo means for driving the objective lens in the disk circumferential direction in accordance with a detection signal from the divided light receiving section, A portion of the laser beam before it enters the lens is reflected by a split mirror and enters the split light receiving section, and the objective lens is driven in the circumferential direction of the disk via an actuator using servo means in response to signals from the split light receiving section. The relative position between the beam intensity center of the laser beam before it enters the objective lens and the objective lens center in the disk circumferential direction can be kept constant at all times. This has the effect of keeping the beam profile constant at all times and obtaining high quality recording/reproducing signals.

[Brief explanation of the drawing]

FIG. 1 is a side view showing a schematic configuration of an optical head according to an embodiment of the present invention, and FIG.
FIG. 3 is a side view schematically showing a conventional optical disk recording/reproducing device, and FIG. 4 is a schematic side view of a conventional optical head used in the device. l...disc, 2...disk motor, 3...
Optical head, 4... Transfer unit, 5... Objective lens, 6... Laser, 7... Collimator lens, 13
. . . Focus error signal detector, 15 . . . Reproduction signal dedicated detector, 16 . . Movable body, 17 .
a, 19b... Light receiving section, Addition... Tracking error signal detector, 21... Servo circuit. Name of agent: Patent attorney Toshio Nakao and one other person
Sugego 81, Figure 3

Claims (1)

[Claims] an objective lens; a three-axis drive actuator capable of driving the objective lens in a focusing direction, a tracking direction, and a circumferential direction of the disk; and a three-axis drive actuator arranged to be movable together with the objective lens at least in the circumferential direction of the disk; a divided mirror that reflects a part of the laser beam before it is applied; a divided light receiving section that is arranged at a position to receive the reflected light of the divided mirror and detects a deviation of the laser beam in the disk circumferential direction; and this divided light receiving section. and servo means for driving the objective lens in the circumferential direction of the disk according to a detection signal from the optical head.