JPS6154049A - Light pickup - Google Patents

Abstract

PURPOSE:To utilize an actuator for detecting signals of a variety of servo systems and to miniaturize a light pickup by disposing photoelectric transfer elements for detecting some part of light for recording and reproducing on the interior of the actuator. CONSTITUTION:Prisms 17 and 19 and photoelectric transfer elements 31, 32 and 33 are disposed at the interior of a rotating actuator. Some part of recording light is made incident on the elements 31 and 32, and the light intensity of a light source is monitored or displayed. Moreover a light intensity stabilizing servo and the lighting up of the light source, etc., are checked. Only the light reflected by a disk is made incident on the transfer element 33 and caused to confirm the presence or absence of the disk and to monitor a reflecting ratio of the disk. Since the actuator is used to obtain a variety of indispensable signals for the constitution of a light pickup, it can be miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to optical video discs, compact digital audio, and still image disc files.

This invention relates to an optical pickup used for recording and reproducing various optical discs such as digital data files.

Conventional Structure and Problems The basic structure of a conventional main pickup using a rotary actuator will be explained with reference to FIG. In Figure 1,
Reference numeral 1 denotes an objective lens holding cylinder, which holds an objective lens 2 mounted at a position eccentric to the central axis of rotation. The objective lens holding tube is connected to a hollow rotating shaft 3 having a window 18, and the rotating shaft 3 is inserted into a rotating bearing 4, and the objective lens holding tube 1 is rotated in the tracking direction about the center of the rotating shaft. It becomes possible to move. Further, the rotation shaft 3 is slidable within the rotation bearing 4,
The objective lens holding cylinder 1 is also movable in the focusing direction. Here, in order for the rotating shaft 3 to rotate and slide smoothly, the bearing portion 4 is made of a plastic material that has its own lubricity, and the rotating shaft 3 is also made of a non-ferrous metal such as aluminum or ceramic. ing. The bearing part 4 is the yoke part 5
is fixed. A ring-shaped magnet 6 is attached to the outer circumference of the yoke portion 6, and an outer circumferential yoke 7 is attached thereon. The outer yoke 7 is composed of a yoke wall and a notch (not shown), and the yoke wall and the notch are arranged in two symmetrical positions separated by 90 degrees in the circumferential direction. The inner circumferential yoke (not shown) is similarly composed of a yoke wall and a notch,
The outer circumferential yoke 7 and the inner circumferential yoke portion are arranged such that the yoke walls and the notches face each other. A magnetic circuit is formed between the inner circumferential yoke wall, the yoke portion 5, the magnet, the outer circumferential yoke 7, and the outer circumferential yoke 7, and the outer circumferential portion of the objective lens holding cylinder portion 1 is inserted between the respective yoke walls. A focusing coil 9 and a tracking coil (not shown) are attached to the objective lens holding cylinder 1.
placed on the outer periphery of The focusing coil 9 is wound in the circumferential direction, and by passing a current through this coil, a force is applied to the coil in the direction of the rotation center axis, and depending on the direction and value of the current, the rotation center axis of the objective lens holding tube 1 is Control directional movement and focus. The tracking coils are wound in a rectangular shape, and four tracking coils are arranged on the outer periphery of the objective lens holding cylinder 1. Half of each tracking coil is located within the magnetic air gap and the other half is located in the cutout.

When a current is applied to this coil, a force is applied to the coil located within the magnetic gap in the circumferential direction of the rotation axis, and the direction and value of the current control the movement of the objective lens holding tube 1 in the circumferential direction of the rotation axis. and perform tracking.

Reference numeral 16 denotes a window that directs light from the light source into the rotating shaft, and then a prism 17 fixed within the rotating wheel and a prism 19 on a fixed base 20 coupled to the inner wall of the objective lens holding cylinder. Guide the light to objective lens 2.

In the rotary actuator configured in this way, the prisms 17 and 19 are fixed on the rotation shaft 14 and the objective lens holding tube 1, respectively, and move together with the objective lens holding tube, so that the objective lens 2 can be rotated. This has the advantage that there is no loss of light amount due to vignetting even when the lens moves or slides, and the tracking range can be widened.

However, the various servo system detection optical systems and signal regeneration detection systems that make up the optical pickup are all located outside the rotary actuator, and when considered as an optical pickup, the dimensions are quite large. There was a problem in that the entire playback machine could not be made smaller.

OBJECTS OF THE INVENTION An object of the present invention is to reduce the size of an optical pickup using a rotary actuator.

Composition of the Invention The present invention aims to utilize the advantages of a rotary actuator while also achieving miniaturization as an optical pickup. It features a configuration in which conversion elements are arranged to detect various servo systems and reproduced signals.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention is shown in FIG. In the figure, numerals 31 to 33 indicate photoelectric conversion elements, respectively. Photoelectric conversion elements 31 and 32 are used to monitor and display the light intensity from the light source, to perform a light intensity stabilization servo, to confirm the lighting of the light source, and to monitor the light modulation waveform. In order to make a desired amount of light incident on the photoelectric conversion element, it is necessary to apply a desired coating to the prism. Furthermore, when linearly polarized light is used as a light source, this can also be achieved by coating the prism surface so that the plane of polarization is totally reflected, and arranging the light source so that the plane of polarization is slightly inclined. Furthermore, the use of the photoelectric conversion element 33 makes it possible to check the presence or absence of a disc, monitor the reflectance of the disc, etc.

Another embodiment of the invention is shown in FIG. In the figure, numeral 34 denotes a two-split photoelectric conversion element, which is divided into two in the direction perpendicular to the plane of the paper. The view in the X direction is shown in Figure 3. In FIG. 3, the arrow indicates the track direction. In this way, the two-split photoelectric conversion element 34
When the disk is placed at the focal point of the objective lens 2, the far-field distribution from the grooves or pits on the disk is determined by the relative position of the reading or writing spot and the grooves or pits on the two-split photoelectric conversion element 34. The tracking error signal can be detected by calculating the difference between the outputs of each photoelectric conversion element. However, in this case, it is desirable that the depth of the groove or pit be approximately λ/8 with respect to the wavelength λ of the light source.

Reference numeral 36 denotes a knife attached to the objective lens holding tube 1, and when the objective lens 2 focuses on the disk surface, the light reflected from the disk passes through the windows 18 and 35 via the prism 19. It is placed so as to shield half of the area.

Further, a two-split photoelectric conversion element 37 is fixed to the inner wall of the objective lens holding cylinder 1. The light conversion element 37 is divided into 3 parts a and 37b in the direction of the central axis of rotation. By arranging the knife 36 in this way, the differential signal output from the two-split photoelectric conversion element 37 can be focused on the disk depending on the relative relationship between the disk position and the focal position of the objective lens 2. The focus error signal can be detected by changing between + and - around 0 center. This signal detection can be performed by adding the respective outputs of the photoelectric conversion elements for focus and tracking detection.

By adopting such a configuration, it is possible to place all the components of the original pickup inside the rotary actuator, making it possible to reduce the size of the pickup, and moreover, it is possible to make effective use of the advantages of the rotary type actuator. It becomes possible to obtain a high-quality detection signal without such problems.

FIG. 4 shows another embodiment of the invention. In the figure, 38 is a holder for mounting a 7-lindrical lens 39 and a 4-split charging detector 40t, which is fixed to the prism 19. An optical system configured in this way is generally called an astigmatism method, and uses the fact that the beam shape on the detector changes from ellipse to perfect circle to ellipse depending on the position of the disk to generate a focus signal. To detect. An X-direction field view of the photoelectric conversion element is shown in FIG. In this case, detection of the focus error signal can be realized by taking the difference between the signal obtained by adding the photoelectric conversion elements 4Qa and 4Qc and the signal obtained by adding 4ob and aod. Detection of tracking error signal is
It can be detected by taking the difference between the signal obtained by adding photoelectric conversion elements 40a and 4od and the signal obtained by adding 4ob and 40c (!
It is obtained by adding the outputs of each of the aods.

By adopting the above configuration, the same advantages as those of the above-described embodiments can be obtained.

FIG. 5 shows another embodiment of the invention. 41 is prism 1
9 shows an optical fiber whose one end is fixed to a plane parallel to the rotational center axis of 9, and the other end is arranged at the center position of the two-split photoelectric conversion element 42.

The X-direction field view of the photoelectric conversion element 'f' is shown in FIG.

When arranged in such a configuration, if the light from one end of the ipar 71 is located at the center of the two-split photoelectric conversion element 42 when the rotary actuator is located at the rotational neutral point, each The differential signal output from the photoelectric conversion elements 42a and 42b makes it possible to detect the rotational position of the rotational actuator. This signal can be used as a return signal to the neutral point or as a position signal of the original pickup during random access. In this embodiment, the light transmitted through the prism 19 is used, but the same detection can be performed using the light transmitted through the prism 17. However, in this case, since the reflected light from the objective lens is used, it is necessary to arrange the subject so that it is near the focal point of the objective lens 2. still,
The amount of light is also smaller than in the case of the prism 19.

Another embodiment of the present invention will be described using FIG. 6.

45 is a holder that holds the lens 43, and the prism 19
Fixed. A part of the reflected light from the disk passes through the prism 19 and is focused on a one-dimensional physical sensor 40. A one-dimensional position sensor is a sensor whose output voltage changes depending on the spot position on the sensor. In this case, the rotational position of the actuator 〇 can be detected by correcting the one-dimensional positive sensor at the rotational neutral point, as in the above embodiment.

Effects of the Invention As described above, the present invention eliminates vignetting due to the rotation of a rotary actuator by arranging photoelectric conversion elements for detecting various signals that are essential for the configuration of an optical pickup in the rotary actuator. By taking advantage of the fact that this phenomenon does not occur, it is possible to perform good signal detection, and the optical pickup can be made extremely compact.

In addition, in the present invention, a photoelectric element is arranged inside a rotary actuator whose optical path is part of the rotation axis, and detects a part of the light irradiated onto a disk for recording, reproduction, or erasing. The purpose of use of the photoelectric conversion element and the arrangement or combination of the light source system for signal detection are not limited.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional optical pickup using a rotating actuator, FIG. 2 is a block diagram of an optical pickup according to an embodiment of the present invention, and FIG. FIGS. 4 and 5 show an optical pickup as another embodiment of the present invention, where a is a configuration diagram, b is a view from the direction of the arrow of a photoelectric conversion element, and FIG. 6 is a still another embodiment of the present invention. FIG. 2 is a configuration diagram of an optical pickup. 1...Objective lens holding tube, 2...One objective lens, 3...Rotation shaft, 4...Rotation bearing, 6...-・Yoke, 6...Magnet, 7...Outer yoke, 9...-7 Orcasing coil, 16...Window, 1y, 19. -3
5... Prism, 20... Prism fixing stand, 31.32, 33, 34, 37, 40.44...
・・・・Photoelectric conversion element, 36・・・・Nifetsuji, 39・・・Cylindrical lens, 4o・・・・
...Lens, 38°46...Holder, al.
...Fiber. Name of agent: Patent attorney Toshio Nakao and 1 other person'2
1 1X4 Figure 2 Figure 3 ((L)

Claims (3)

[Claims] (1) an objective lens holding tube that is rotatable around a rotational center axis and slidable in the axial direction of the rotational center axis; an objective lens provided at a position, a means for driving the objective lens holding tube in the two axial directions, a rotary actuator that makes the inside of the rotation axis a part of the optical path, and a rotary actuator that transmits light from a light source. An optical pickup comprising a means for guiding the light to the objective lens, the objective lens condensing the light from the light source to almost the solar limit, and realizing at least one function of optically recording, reproducing, and erasing information. An optical pickup characterized in that a photoelectric conversion element for detecting at least a portion of light from the light source is disposed within the rotary actuator. (2) The optical pickup according to claim 1, wherein the photoelectric conversion element is fixed on the objective lens holding cylinder. (3) Claim 1, characterized in that the photoelectric conversion element is arranged in a fixed part of the rotary actuator.
Optical pickup described in section.